Methods and systems for forming an object by volumetric printing

Abstract

The present invention includes methods for forming an object in a volume of a photohardenable composition included in a container including directing a light sheet and an optical image through a selected region of a surface of the container to a first position in the volume to initiate hardening of the composition as a result of exposure to the light sheet and optical image, wherein at least one of the light sheet or the optical image pass through an optical alignment element before passing into the container. Systems and printhead modules are also disclosed.

Description

[0001] METHODS AND SYSTEMS FOR FORMING AN OBJECT BY VOLUMETRIC PRINTING

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims priority to U.S. Provisional Patent Application No. 63 / 639,280 filed on 26 April 2024, which application is hereby incorporated herein by reference in its entirety for all purposes.

[0004] TECHNICAL FIELD OF THE INVENTION

[0005] The present invention relates to the technical field of three-dimensional (3D) printing.

[0006] BRIEF SUMMARY OF THE INVENTION

[0007] The present invention includes methods, systems, and printhead modules for volumetric 3D printing including two or more excitation lights for forming an object or for printing onto an object, wherein at least one of the excitation lights passes through an optical alignment element positioned in the path of the excitation light before entering a container including a photohardenable composition. Preferably at least two of the excitation lights enter the container through, or from, the same side of the container.

[0008] In accordance with one aspect of the present invention, there is provided a method of forming an object in a volume of a photohardenable composition, the method comprising: a. providing a container containing the volume of the photohardenable composition; b. directing a first excitation light along a first light path into the container to a first position in the photohardenable composition and directing a second excitation light along a second light path into the container to the first position in the photohardenable composition such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the first and second excitation lights, wherein at least one of the excitation lights is directed through an optical alignment element before entering the container, and wherein the first position is located at a selected location in the volume of the photohardenable composition; and c. optionally repeating step b. until the object is partially or fully formed, wherein, for a repeated step, the optical image is the same as or different from a previous optical image and the container is positioned such that the selected location in a repeated step is the same as or different from a previous selected location.

[0009] Optionally, in cases where both of the first and second excitation lights pass through an optical alignment element, each can enter a single optical alignment element or different optical alignment elements. Methods described herein can optionally further include changing the location of the container relative to the first position to a selected position in the container.

[0010] An optical alignment element included in a system and method described herein is preferably in direct contact or optically coupled to a surface of the container through which a light path exits the element and enters the container.

[0011] Preferably, a light path entering an input surface of an optical alignment element enters the input surface at a selected angle.

[0012] The portion of a light path as it exits an optical system from which it is generated (e.g., but not limited to, a light sheet generating system, a projection system, etc.) before entry into an optical alignment element or a surface of the container, in cases where a light path does not pass through an optical alignment element before entry into the container, is also referred to herein as an optical axis.

[0013] Optionally, step b can further include directing a third excitation light along a third light path into the container to the first position in the photohardenable composition such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the first, second, and third excitation lights, wherein at least one of the excitation lights is directed through an optical alignment element before entering the container, and wherein the first position is located at a selected location in the volume of the photohardenable composition.

[0014] In accordance with another aspect of the present invention, there is provided a method of forming an object in a volume of a photohardenable composition, the method comprising: a. providing a container containing the volume of the photohardenable composition; b. directing a light sheet including first excitation light along a first light path into the container to a first position in the photohardenable composition and directing an optical image including a second excitation light into the container to the first position in the photohardenable composition such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the light sheet and optical image, the light sheet and / or optical image passes through an optical alignment element before entering the container, and wherein the first position is located at a selected location in the volume of the photohardenable composition; and c. optionally repeating step b. until the object is partially or fully formed, wherein, for a repeated step, the optical image is the same as or different from a previous optical image and the container is positioned such that the selected location in a repeated step is the same as or different from a previous selected location. Optionally, in cases where both of the light sheet and optical image pass through an optical alignment element, each can enter a single optical alignment element or different optical alignment elements.

[0015] Methods and systems described herein can optionally further include changing the location of the container relative to the first position to a selected position in the container.

[0016] An optical alignment element included in a method described is preferably in direct contact or optically coupled to a surface of the container through which a light path exits the element and enters the container.

[0017] Optionally, step b can further include directing a second light sheet along a third light path into the container to the first position in the photohardenable composition such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the light sheet, the optical image, and the second light sheet, wherein at least one of the light sheet, the optical image, or the second light sheet is optionally directed through an optical alignment element before entering the container, and wherein the first position is located at a selected location in the volume of the photohardenable composition.

[0018] Preferably, a light path entering an input surface of an optical alignment element enters the input surface at a selected angle.

[0019] In accordance with another aspect of the present invention, there is provided a method of forming an object in a volume of a photohardenable composition, the method comprising: a. providing a container containing the volume of the photohardenable composition, b. directing a light sheet including first excitation light along a first light path through a first optical alignment element into the container containing the volume of the photohardenable composition and projecting an optical image including a second excitation light along a second light path through the same optical alignment element or a different optical alignment element into the container including the photohardenable composition, wherein the first light path and the second light path are oriented for the light sheet and optical image to intersect at a first position and the container is positioned relative to the first position to locate the intersection of the light sheet and the projected image at a selected location in the photohardenable composition to at least partially harden the photohardenable composition at the selected location as a result of exposure to the light sheet and optical image, and c. optionally repeating step b. until the object is partially or fully formed, wherein, for a repeated step, the optical image is the same as or different from a previous optical image and the container is positioned such that the intersection of the light sheet and projected image in a repeated step is located at a location in the volume that is the same as or different from a previous selected location.

[0020] Methods described herein can optionally further include changing the location of the container relative to the first position to a selected position in the container.

[0021] An optical alignment element included in a method described herein is preferably in direct contact or optically coupled to a surface of the container through which an excitation light path exits the element and enters the container.

[0022] Optionally, step b can further include directing a second light sheet along a third light path into the container to the first position in the photohardenable composition such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the light sheet, the optical image, and the second light sheet, wherein at least one of the light sheet, the optical image, or the second light sheet is optionally directed through an optical alignment element before entering the container, and wherein the first position is located at a selected location in the volume of the photohardenable composition.

[0023] Preferably, a light path entering an input surface of an optical alignment element enters the input surface at a selected angle.

[0024] In accordance with another aspect of the present invention, there is provided a system for forming an object in a volume of a photohardenable composition, the system comprising: a combination including: a. a first optical system for generating first excitation light, the first optical system including first optics for directing the generated first excitation light along a first light path to a first position in a container for containing the volume of the photohardenable composition; b. a second optical system for generating second excitation light, the second optical system including second optics for directing the generated second excitation light along a second light path to the first position in a container for containing the volume of the photohardenable composition; and c. at least one optical alignment element, the optical alignment element being configured or configurable such that at least one of the generated excitation lights passes through an optical alignment element before passing into the container, wherein the two light paths are configured or configurable such that the first and second light paths intersect at the first position in the container. Optionally, in cases where both of the light sheet and optical image pass through an optical alignment element, each of the first and second excitation lights can be oriented or orientable to pass through a single optical alignment element or different optical alignment elements.

[0025] Systems described herein can optionally further include a translation mechanism for changing the location of the container relative to the first position to a selected position in the container.

[0026] An optical alignment element included in a system described herein is preferably in direct contact or optically coupled to the surface of the container through which an excitation light path exits the element and enters the container.

[0027] Preferably, a light path entering an input surface of an optical alignment element enters the input surface at a selected angle.

[0028] In accordance with another aspect of the present invention, there is provided a system for forming an object in a volume of a photohardenable composition, the system comprising: a combination including: a. a light sheet generating system for generating a light sheet from a first excitation light, the light generating system including first optics for directing the generated light sheet along a first light path to a first position in a container for containing the volume of the photohardenable composition; b. a projection system for projecting an optical image from a second excitation light, the projection system including second optics for directing the optical image along a second light path to the first position in the container, wherein the first optics and second optics are fixed or movable relative to each other; and c. at least one optical alignment element, the optical alignment element being positioned or positionable such that the generated light sheet and / or projected optical image passes through an optical alignment element before passing into the container, wherein the two light paths are configured or configurable such that the first and second light paths intersect at the first position in the container.

[0029] Optionally, in cases where both of the light sheet and optical image pass through an optical alignment element, each of the light sheet and optical image can be oriented or orientable to pass through a single optical alignment element or different optical alignment elements.

[0030] Systems described herein can optionally further include a translation mechanism for changing the location of the container relative to the first position to a selected position in the container. An optical alignment element included in a system described herein is preferably in direct contact or optically coupled to the side of the container through which excitation light path exits the element and enters the container.

[0031] Optionally systems described herein can further include a second light sheet generator including third optics on a side of the container opposite the light sheet generator for directing a second generated light sheet along a third light path to the first position in a container and an additional optical alignment element positioned or positionable such that the third light path passes through the additional optical alignment element into the container. In such case, the first, second, and third light paths are preferably configured or configurable to facilitate the three light paths intersecting at the first position in the container such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the first light sheet, second light sheet, and optical image.

[0032] Preferably, a light path entering an input surface of an optical alignment element enters the input surface at a selected angle.

[0033] In accordance with another aspect of the present invention, there is provided a system for forming an object in a volume of a photohardenable composition, the system comprising: a combination including: a. a light sheet generating system for generating a light sheet from a first excitation light, the light sheet generating system including first optics for directing the generated light sheet along a first light path to a first position in a container for containing the volume of the photohardenable composition; b. a projection system for projecting an optical image from a second excitation light, the projection system including second optics for directing the generated optical image along a second light path to the first position in the container, wherein the first optics and second optics are fixed or movable relative to each other, c. a first optical alignment element being positioned or positionable such that the first light path passes through the first optical alignment element into the container and a second optical alignment element being positioned or positionable such that the second light path passes through the first optical alignment element into the container, wherein the first and second optical alignment elements are positioned or positionable such that the first and second light paths intersect at the first position in the container.

[0034] Optionally, in cases where both of the light sheet and optical image pass through an optical alignment element, each of the light sheet and optical image can be oriented or orientable to pass through a single optical alignment element or different optical alignment elements. The system can optionally further include a translation mechanism for changing the location of the container relative to the first position to a selected position in the container.

[0035] The first optical alignment element and second optical alignment element are preferably in direct contact or optically coupled to an outer surface of the container through which a light path exits an element and enters the container.

[0036] Optionally the system can further include a second light sheet generator including third optics on a side of the container opposite the light sheet generator for directing a second generated light sheet along a third light path to the first position in a container and a third optical alignment element being positioned or positionable such that the third light path passes through the third optical alignment element into the container. In such case, the first, second, and third light paths are preferably configured or configurable to facilitate the three light paths intersecting at the first position in the container such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the first light sheet, second light sheet, and optical image.

[0037] Preferably, the first light path enters a first input surface of the first optical alignment element at a first selected angle and the second light path enters a second light input surface of the second optical alignment element at a second selected angle.

[0038] In accordance with another aspect of the present invention, there is provided a system for forming an object in a volume of a photohardenable composition, the system comprising a combination including: a. a light sheet generating system for generating a light sheet from a first excitation light, the light sheet generating system including first optics for directing the generated light sheet along a first light path to a first position in a container for containing the volume of the photohardenable composition; b. a projection system for projecting an optical image from a second excitation light, the projection system including second optics for directing the generated optical image along a second light path to the first position in the container, wherein the first optics and second optics are fixed or movable relative to each other; c. a first optical alignment element being positioned or positionable such that the first light path passes through the first optical alignment element into the container, and a second optical alignment element being positioned or positionable such that the second light path passes through the second optical alignment element into the container, wherein the first and second light paths are configured or configurable such that the first and second light paths intersect at the first position in the container. The system can optionally further include a translation mechanism for changing the location of the container relative to the first position to a selected position in the container.

[0039] Optionally the system can further include a third optical system comprising (i) a second light sheet generating system including third optics or (ii) reflection optics including third optics for reflecting the light sheet passing through the container back through the container, the third optical system being positioned on a side of the container, opposite the first optical system, for directing a second generated light sheet or directing the reflected light sheet along a third light path to the first position in the container. In such case, the first, second, and third light paths are preferably configured or configurable to facilitate the three light paths intersecting at the first position in the container such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the first light sheet, second light sheet, and optical image.

[0040] In accordance with another aspect of the present invention, there is provided a printhead module for use in forming an object, the printhead module comprising: a combination including: a. first optics for directing first excitation light along a first light path to a first position in a container for including a volume including a photohardenable composition and second optics for directing second excitation light along a second light path to the first position in the container; and b. at least one optical alignment element, the optical alignment element being positioned or positionable such that at least one of the excitation lights passes through one optical alignment element along its respective light path before passing into the container.

[0041] Optionally, in cases where both of the light sheet and optical image pass through an optical alignment element, each of the first and second excitation lights can be oriented or orientable to pass through a single optical alignment element or different optical alignment elements.

[0042] Preferably, the two light paths are configured or configurable to facilitate the first and second light paths intersecting at the first position in the container such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the first and second excitation lights.

[0043] Preferably, the first light path enters a first input surface of the first optical alignment element at a first selected angle and the second light path enters a second light input surface of the second optical alignment element at a second selected angle.

[0044] In accordance with another aspect of the present invention, there is provided a printhead module for use in forming an object, the printhead module comprising: a combination including: a. first optics for directing a generated light sheet along a first light path to a first position in a container for including a volume including a photohardenable composition and second optics for directing a generated optical image along a second light path to the first position in the container; and b. at least one optical alignment element, the optical alignment element being positioned or positionable such that the generated light sheet and / or the optical image passes through an optical alignment element along its respective light path before passing into the container.

[0045] Optionally, in cases where both of the light sheet and optical image pass through an optical alignment element, each of the light sheet and optical image can be oriented or orientable to pass through a single optical alignment element or different optical alignment elements.

[0046] Preferably, the two light paths are configured or configurable to facilitate the first and second light paths intersecting at the first position in the container such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the first and second excitation lights.

[0047] Preferably, the first light path enters a first input surface of the first optical alignment element at a first selected angle and the second light path enters a second light input surface of the second optical alignment element at a second selected angle.

[0048] In accordance with another aspect of the present invention, there is provided a printhead module for use in forming an object, the printhead module comprising a combination including: a. first optics for directing a generated light sheet along a first light path to a first position in a container for including a volume including a photohardenable composition and second optics for directing a generated optical image along a second light path to the first position in the container, and wherein the first optics and second optics are fixed or movable; and b. at least one optical alignment element being positioned or positionable such that each of the first and second light paths independently pass through an optical alignment element before passing into the container, wherein the first and second light paths are configured or configurable such that the first and second light paths intersect at the first position in the container.

[0049] Optionally, in cases where both of the light sheet and optical image pass through an optical alignment element, each of the light sheet and optical image can be oriented or orientable to pass through a single optical alignment element or different optical alignment elements. Preferably, the first light path enters a first input surface of the first optical alignment element at a first selected angle and the second light path enters a second light input surface of the second optical alignment element at a second selected angle.

[0050] In accordance with another aspect of the present invention, there is provided a printhead module for use in forming an object, the printhead module comprising a combination including: a. first optics for directing a generated light sheet along a first light path to a first position in a container for including the volume including a photohardenable composition and second optics for directing a generated optical image along a second light path to the first position in the container, and wherein the first optics and second optics are fixed or movable; b. a first optical alignment element being positioned or positionable such that the first light path passes through the first optical alignment element before passing into the container, and a second optical alignment element being positioned or positionable such that the second light path passes through the second optical alignment element before passing into the container.

[0051] The appended claims are hereby incorporated herein by reference in their entirety.

[0052] The foregoing, and other aspects and embodiments described herein and contemplated by this disclosure all constitute embodiments of the present invention.

[0053] It should be appreciated by those persons having ordinary skill in the art(s) to which the present invention relates that any of the features described herein in respect of any particular aspect and / or embodiment of the present invention can be combined with one or more of any of the other features of any other aspects and / or embodiments of the present invention described herein, with modifications as appropriate to ensure compatibility of the combinations. Such combinations are considered to be part of the present invention contemplated by this disclosure.

[0054] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.

[0055] Other embodiments will be apparent to those skilled in the art from consideration of the description and drawings, from the claims, and from practice of the invention disclosed herein.

[0056] BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In the drawings,

[0058] FIGS. 1A and IB depict diagrams of cross-sections of examples of systems and methods in accordance with the present invention including a light sheet generator, a projection system, an optical alignment element, and a container including a photohardenable composition (depicted as a resin vat) wherein a light path of the light sheet generator or projection system passes through the optical alignment element before entering the container.

[0059] FIG. 2 depicts a diagram of a cross-section of an example of systems and methods in accordance with the present invention including a light sheet generator, a projection system, an optical alignment element, and a container including a photohardenable composition, wherein the light paths of the light sheet generator and the projection system pass through a single optical alignment element before entering the container and are aligned to intersect in a common plane. Optionally the interface between the surface of the container through which the light paths enter the container is indexed matched, for example, using a coupling fluid. FIG. 2 also indicates a direction of movement of the container relative to the intersection of the light paths. In the depicted example, the container can optionally move in the x, y, or x,y direction.

[0060] FIG. 3 depicts a diagram of a cross-section of an example of a method and system in accordance with the present invention including one optical alignment element through which a light sheet generated by a light generating system and an optical image projected by a projection system wherein the light alignment element, light sheet generator, and projection system are included within an enclosure.

[0061] FIG. 4 depicts a diagram of a cross-section of an example of a system including a printhead including, for example, in combination, first optics for directing a generated light sheet along a first light path to a first position in a container for including a volume including a photohardenable composition and second optics for directing a generated optical image along a second light path to the first position in the container, and wherein the first optics and second optics are fixed or movable; and two optical alignment elements being positioned or positionable such that the light sheet light path passes through first optical alignment element into the container and the optical image light path passes through the second optical alignment element into the container to intersect at the first position located at a selected position in the photohardenable composition included in the container.

[0062] FIGS. 5 A and 5B depict diagrams of cross-sections of examples of systems and methods in accordance with the present invention in which the projected image is moved (FIG. 5A) and in which the light sheet is moved (FIG. 5B).

[0063] FIGS. 6A and 6B depict diagrams of a cross-section of two examples of systems and methods in accordance with the present invention that include two light paths passing through the different optical alignment elements (e.g., depicted as two right angle prisms) (FIG. 6A) or a single optical alignment element (e.g., depicted as a right angle dove prism) (FIG. 6B) with each light path being normal to a light input face of an optical alignment element and configured to intersect in the container. FIG. 7 depicts a diagram of a cross-section of an example of a system and method in accordance with the present invention that includes two light paths passing through a single optical alignment element wherein the light sheet and projection angles are not symmetric inside the container.

[0064] FIG. 8 depicts a diagram of a cross-section of an example of systems and methods in accordance with the present invention that includes optical axes that are not normal to the light input faces of the optical alignment element.

[0065] FIG. 9 depicts a diagram of a cross-section of an example of systems and methods in accordance with the present invention including an optical alignment element and a photohardenable composition with different refractive indices.

[0066] FIGS. 10A and 10B depict diagrams of a cross-section of two examples of systems and methods in accordance with the present invention. FIG. 10A include two light sheet generating systems and opposed optical alignment elements. FIG. 10B includes a light sheet generating system and optics to reflect the light sheet passing out of the container back through the container and opposed optical alignment elements wherein the light sheet and reflected light sheet each pass through an optical alignment element before entering the container.

[0067] FIG. 11 depicts an example of a cross section of an example of a system and method in accordance with the present invention.

[0068] FIG. 12 depicts a diagram of a perspective view an example of the present invention including a light sheet generator and a projection system (e.g., for generating a two-dimensional (2D) optical image) that are aligned with an optical alignment element (depicted as a prism) to form a 2D-light layer to photopolymerize a resin within a vat on a translation mechanism, wherein the optical alignment element, light sheet generator, and projection system are included within an enclosure.

[0069] FIG. 13 depicts a diagram of a cross-section of an example of the present invention wherein a light sheet generator and a projection system (e.g., for generating a two-dimensional (2D) optical image)are aligned with an optical alignment element to form a 2D-light layer to photopolymerize a photohardenable composition included within a moveable container (e.g., a vat) wherein the container is physically separated from the light sheet generator and 2D projection system and optical alignment element by a window.

[0070] FIG. 14 depicts a diagram of a cross-section an example of a system in accordance with the present invention in which an optical alignment element is integrated with a container (depicted as a vat) that includes the volume of photohardenable composition (depicted as a resin) wherein the container is surrounded by an index-matched fluidic seal or bearing. FIG. 15 depicts a diagram of a cross-section an example of a system and method in accordance with the present invention in which features or additional structure(s) is overprinted onto an object included in the container that includes a volume of photohardenable composition.

[0071] FIG. 16 depicts a side view of an example of a projection system including second optics for projecting a two-dimensional optical image in systems and methods of the present invention.

[0072] FIGS. 17A and 17B depict diagrams of yz and xy views of an example of a light sheet generation system including first optics for inclusion in the present invention.

[0073] FIGS. 18A and 18B depicts examples of two embodiments of the present invention. FIG.

[0074] 18 A shows the case where light sheet and projection light paths are preferably separated by 90 degrees: in one embodiment (a) the two optical path are at a 45 degree angle to the container, in the other (b) they are not.

[0075] The attached figures are simplified representations presented for purposes of illustration only; the actual structures may differ in numerous respects, particularly including the relative scale of the articles depicted and aspects thereof.

[0076] For a better understanding to the present invention, together with other advantages and capabilities thereof, reference is made to the following disclosure and appended claims in connection with the above -described drawings.

[0077] DETAILED DESCRIPTION OF THE INVENTION

[0078] Various aspects and embodiments of the present inventions will be further described in the following detailed description.

[0079] The present invention relates to methods, systems, and printhead modules for volumetric printing of a three-dimensional object.

[0080] The present invention includes methods, systems, and printhead modules for volumetric 3D printing including two or more excitation lights for forming an object or for printing onto an object, wherein at least one of the excitation lights passes through an optical alignment element positioned in the path of the excitation light before entering a container including a photohardenable composition. Preferably at least two of the excitation lights enter the container through, or from, the same side of the container.

[0081] The invention described herein includes methods, systems, and printhead modules that can be particularly advantageous for use in volumetric 3D printing including two or more excitation lights for forming an object or for printing onto a surface of an object. Preferably at least two of the two or more excitation lights enter a container including a resin (also referred to herein as a photohardenable composition) through or from the same side of the container wherein at least one of the excitation lights entering through or from the same side of the container through an optical alignment element positioned in its path of the excitation light before entering the container.

[0082] The methods, systems, and printhead modules of the present invention are advantageous for forming an object including volumetric printing that includes two optical projections. The present invention is particularly advantageous for methods, systems, and printhead modules in which one of the optical projections includes a light sheet.

[0083] The methods, systems, and printhead modules of the present invention are advantageous for use in volumetric printing that includes two optical projections and a volume of a photohardenable composition including the use of upcon verting materials, triplet-triplet annihilation (TTA), photos witchable photoinitiators or other dual- wavelength photoinitiators, and / or combinations including any one or more of the foregoing.

[0084] Volumetric three-dimensional (3D) printing including use of a first projection including a light sheet and a second projection including an optical image can provide a number of benefits such as, for example, high-speed and high-resolution.

[0085] The present invention advantageously can facilitate the ability to print an object in a volume of a photohardenable composition and maintaining a fixed distance or light path length between the optics of the optical systems and the plane in which the object is printed. Such capability can reduce print quality variations such as scattering and light absorption by the photohardenable composition that can arise with varying light path lengths during printing.

[0086] The present invention additionally can facilitate the ability to print with the positions of the optical systems staying fixed with respect to each other and only moving the container including the photohardenable composition relative to the fixed optical systems during printing. Such capability can permit a more compact system footprint, better access to the container (e.g., for cleaning, exchange, etc.), a better geometry for continuous processing compared to one that calls for two opposite unimpeded sides of the container.

[0087] The present invention advantageously can further reduce or overcome complexities associated with printing with two excitation lights that enter from orthogonal sides of a printing container. For example, when printing with two optical projections ( e.g., light sheet and projected optical images) that enter from orthogonal sides of the printing container, as the light sheet transits the container, if the projection system is in focus at the first position, it can become out of focus as the optical projection has to travel through different amounts of air compared to the photohardenable composition to reach the first position, since the photohardenable composition typically has greater index of refraction than air. In order to compensate for this effect, the projection system may need to include an autofocusing function or be moved, e.g., along a stage. Another challenge of this orientation is that the optical projection will travel through larger volumes of the photohardenable composition as the build volume length is increased. For larger volumes of printing, such as a printing system with an optical projection traveling through, e.g., more than 5 cm or even 10 cm of photohardenable composition, any haze or imperfections in the photohardenable composition can cause deformations in the optical projection. The farther the light travels through photohardenable composition, the more opportunity for distortion of the image. Furthermore, over larger distances, issues with vignetting of the optical projection can occur which can require widening of the build volume relative to the optical projection size. Because projected light will have a finite numerical aperture, it will be wider when entering the container than at its focal plane, and to avoid vignetting wider light, the container must be widened. The longer the container, the more significant the required widening. Another complexity when printing with a two optical projections that enter from orthogonal sides of the printing container that can be avoided with the present invention is having to move the light sheet to maintain the desired alignment if a projected image plane location (at focus or within the depth of focus) of the optical image is moved within the volume to print the object.

[0088] Finally, issues can arise in overprinting when the two optical projections enter from separate sides of the container, where occlusion or scattering by the object can prevent successful optical access to an overprinting surface. In the case of overprinting, access from the same side of the container can in many cases provide more unimpeded access to a surface where overprinting is desired. Furthermore, in the case of light sheet and projector entering on the same surface, the focal plane of the projected image can be placed in focus at the first position of the light sheet intersection, and will not move during the print even as the container and optical system are moved relative to each other. Therefore, there is no motion or autofocusing required to remain in focus during the print. Similarly, increases in build volume size do not lead to increased issues with vignetting of projected light when both projector and light sheet enter from same side. The addition of optical coupling elements described here also help to keep the projected image in focus and correctly positioned to overlap the light sheet despite the different refractive indices of air and resin.

[0089] In the invention described herein, preferably two excitation lights, preferably in the form of a light sheet and an optical image, enter a container including a resin or photohardenable composition through one or more selected regions of a surface of the container, preferably through the same side of the container. The attached figures show various examples of the present invention.

[0090] Inclusion of an optical alignment element in the methods, systems, and print modules described herein enables maintaining the direction of the excitation light entering the container of photohardenable composition, otherwise the light path is refracted within the container, which can result in printing inaccuracies. In accordance with one aspect of the present invention, there is provided a method of forming an object in a volume of a photohardenable composition, the method comprising: a. providing a container containing the volume of the photohardenable composition; b. directing a first excitation light along a first light path into the container to a first position in the photohardenable composition and directing a second excitation light along a second light path into the container to the first position in the photohardenable composition such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the first and second excitation lights, wherein at least one of the excitation lights is directed through an optical alignment element before entering the container, and wherein the first position is located at a selected location in the volume of the photohardenable composition; and c. optionally repeating step b. until the object is partially or fully formed, wherein, for a repeated step, the optical image is the same as or different from a previous optical image and the container is positioned such that the selected location in a repeated step is the same as or different from a previous selected location.

[0091] Optionally, in cases where both of the first and second excitation lights pass through an optical alignment element, each can enter a single optical alignment element or different optical alignment elements.

[0092] An optical alignment element included in the system is preferably in direct contact or optically coupled to the surface of the container through which a light path exits the element(s) and enters the container.

[0093] Preferably, a light path enters an input surface of an optical alignment element at a selected angle.

[0094] Optionally, step b can further include directing a third excitation light along a third light path into the container to the first position in the photohardenable composition such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the first, second, and third excitation lights, wherein at least one of the first, second, or third excitation lights is directed through an optical alignment element before entering the container, and wherein the first position is located at a selected location in the volume of the photohardenable composition.

[0095] In accordance with another aspect of the present invention, there is provided a method of forming an object in a volume of a photohardenable composition, the method comprising: a. providing a container containing the volume of the photohardenable composition; b. directing a light sheet including first excitation light along a first light path into the container to a first position in the photohardenable composition and directing an optical image including a second excitation light into the container to the first position in the photohardenable composition such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the light sheet and optical image, wherein the light sheet and / or optical image passes through an optical alignment element before entering the container, and wherein the first position is located at a selected location in the volume of the photohardenable composition; and c. optionally repeating step b. until the object is partially or fully formed, wherein, for a repeated step, the optical image is the same as or different from a previous optical image and the container is positioned such that the selected location in a repeated step is the same as or different from a previous selected location.

[0096] Optionally, in cases where both of the first excitation light and second excitation light pass through an optical alignment element, each can enter a single optical alignment element or different optical alignment elements.

[0097] An optical alignment element is preferably in direct contact or optically coupled to the surface of the container through which a light path exits the element and enters the container.

[0098] Optionally, step b can further include directing a second light sheet along a third light path into the container to the first position in the photohardenable composition such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the light sheet, the optical image, and the second light sheet, wherein at least one of the light sheet, the optical image, or the second light sheet is optionally directed through an optical alignment element before entering the container, and wherein the first position is located at a selected location in the volume of the photohardenable composition.

[0099] Preferably, a light path enters an input surface of an optical alignment element at a selected angle.

[0100] In accordance with another aspect of the present invention, there is provided a method of forming an object in a volume of a photohardenable composition, the method comprising: a. providing a container containing the volume of the photohardenable composition, b. directing a light sheet including first excitation light along a first light path through a first optical alignment element into the container containing the volume of the photohardenable composition and projecting an optical image including a second excitation light along a second light path through the same optical alignment element or a different optical alignment element into the container including the photohardenable composition, wherein the first light path and the second light path are oriented for the light sheet and optical image to intersect at a first position and the container is positioned relative to the first position to locate the intersection of the light sheet and the projected image at a selected location in the photohardenable composition to at least partially harden the photohardenable composition at the selected location as a result of exposure to the light sheet and optical image, and c. optionally repeating step b. until the object is partially or fully formed, wherein, for a repeated step, the optical image is the same as or different from a previous optical image and the container is positioned such that the intersection of the light sheet and projected image in a repeated step is located at a location in the volume that is the same as or different from a previous selected location.

[0101] An optical alignment element is preferably in direct contact or optically coupled to the surface of the container through which a light path exits the element and enters the container.

[0102] Optionally, step b can further include directing a second light sheet along a third light path into the container to the first position in the photohardenable composition such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the light sheet, the optical image, and the second light sheet, wherein at least one of the light sheet, the optical image, or the second light sheet is optionally directed through an optical alignment element before entering the container, and wherein the first position is located at a selected location in the volume of the photohardenable composition.

[0103] Preferably, a light path entering an input surface of an optical alignment element enters the input surface at a selected angle.

[0104] In methods in accordance with various aspects of the present invention, the method can further comprise moving the container relative to the first position to change the location of the selected location in the volume of the photohardenable composition.

[0105] In accordance with another aspect of the present invention, there is provided a system for forming an object in a volume of a photohardenable composition, the system comprising: a combination including: a. a first optical system for generating first excitation light, the first optical system including first optics for directing the generated first excitation light along a first light path to a first position in a container for containing the volume of the photohardenable composition; b. a second optical system for generating second excitation light, the second optical system including second optics for directing the generated second excitation light along a second light path to the first position in a container for containing the volume of the photohardenable composition; and c. at least one optical alignment element, the optical alignment element being configured or configurable such that at least one of the generated excitation lights passes through an optical alignment element before passing into the container, wherein the two light paths are configured or configurable such that the first and second light paths intersect at the first position in the container.

[0106] Optionally, in cases where both of the light sheet and optical image pass through an optical alignment element, each of the first and second excitation lights can be oriented or orientable to pass through a single optical alignment element or different optical alignment elements.

[0107] The system can optionally further include a translation mechanism for changing the location of the container relative to the first position to a selected position in the container.

[0108] An optical alignment element included in the system are preferably in direct contact or optically coupled to the surface of the container through which a light path exits the element and enters the container.

[0109] Preferably, a light path entering an input surface of an optical alignment element enters the input surface at a selected angle.

[0110] In accordance with another aspect of the present invention, there is provided a system for forming an object in a volume of a photohardenable composition, the system comprising: a combination including: a. a light sheet generating system for generating a light sheet from a first excitation light, the light generating system including first optics for directing the generated light sheet along a first light path to a first position in a container for containing the volume of the photohardenable composition; b. a projection system for projecting an optical image from a second excitation light, the projection system including second optics for directing the optical image along a second light path to the first position in the container, wherein the first optics and second optics are fixed or movable relative to each other; and c. at least one optical alignment element, the optical alignment element being positioned or positionable such that the generated light sheet and / or the projected optical image passes through an optical alignment element before passing into the container, wherein the two light paths are configured or configurable such that the first and second light paths intersect at the first position in the container.

[0111] Optionally, in cases where both of the light sheet and optical image pass through an optical alignment element, each of the light sheet and optical image can be oriented or orientable to pass through a single optical alignment element or different optical alignment elements. The system can optionally further include a translation mechanism for changing the location of the container relative to the first position to a selected position in the container.

[0112] An optical alignment element included in the system is preferably in direct contact or optically coupled to the side of the container through which a light path exits the element and enters the container.

[0113] Optionally the system can further include a second light sheet generator including third optics on a side of the container opposite the light sheet generator for directing a second generated light sheet along a third light path to the first position in a container and a third optical alignment element being positioned or positionable such that the third light path passes through the third optical alignment element into the container. In such case, the first, second, and third light paths are preferably oriented or orientable to facilitate the three optical light paths intersecting at the first position in the container such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the first light sheet, second light sheet, and optical image.

[0114] Preferably, a light path entering an input surface of an optical alignment element enters the input surface at a selected angle.

[0115] In accordance with another aspect of the present invention, there is provided a system for forming an object in a volume of a photohardenable composition, the system comprising: a combination including: a. a light sheet generating system for generating a light sheet from a first excitation light, the light sheet generating system including first optics for directing the generated light sheet along a first light path to a first position in a container for containing the volume of the photohardenable composition; b. a projection system for projecting an optical image from a second excitation light, the projection system including second optics for directing the generated optical image along a second light path to the first position in the container, wherein the first optics and second optics are fixed or movable relative to each other, c. a first optical alignment element being positioned or positionable such that the first light path passes through the first optical alignment element into the container and a second optical alignment element being positioned or positionable such that the second light path passes through the first optical alignment element into the container, wherein the first and second optical alignment elements are positioned or positionable such that the first and second light paths intersect at the first position in the container. Optionally, in cases where both of the light sheet and optical image pass through an optical alignment element, each of the light sheet and optical image can be oriented or orientable to pass through a single optical alignment element or different optical alignment elements.

[0116] The system can optionally further include a translation mechanism for changing the location of the container relative to the first position to a selected position in the container.

[0117] The first optical alignment element and second optical alignment element are preferably in direct contact or optically coupled to an outer surface of the container through which a light path exits an elements and enters the container.

[0118] Optionally the system can further include a second light sheet generator including third optics on a side of the container opposite the light sheet generator for directing a second generated light sheet along a third light path to the first position in a container and a third optical alignment element being positioned or positionable such that the third light path passes through the third optical alignment element into the container. In such case, the first, second, and third light paths are preferably configured or configurable to facilitate the three optical light paths intersecting at the first position in the container such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the first light sheet, second light sheet, and optical image.

[0119] Preferably, the first light path enters a first input surface of the first optical alignment element at a first selected angle and the second light path enters a second light input surface of the second optical alignment element at a second selected angle.

[0120] In accordance with another aspect of the present invention, there is provided a system for forming an object in a volume of a photohardenable composition, the system comprising a combination including: a. a light sheet generating system for generating a light sheet from a first excitation light, the light sheet generating system including first optics for directing the generated light sheet along a first light path to a first position in a container for containing the volume of the photohardenable composition; b. a projection system for projecting an optical image from a second excitation light, the projection system including second optics for directing the generated optical image along a second light path to the first position in the container, wherein the first optics and second optics are fixed or movable relative to each other; c. a first optical alignment element being positioned or positionable such that the first light path passes through the first optical alignment element into the container, and a second optical alignment element being positioned or positionable such that the second light path passes through the second optical alignment element into the container, wherein the first and second light paths are configured or configurable such that the first and second light paths intersect at the first position in the container.

[0121] The system can optionally further include a translation mechanism for changing the location of the container relative to the first position to a selected position in the container.

[0122] Optionally the system can further include a third optical system comprising a second light sheet generating system including third optics or reflection optics including third optics for reflecting the light sheet passing through the container back through the container, the third optical system being positioned on a side of the container opposite the first optical system for directing a second generated light sheet or directing the reflected light sheet along a third light path to the first position in the container. In such case, the first, second, and third light paths are preferably oriented or orientable to facilitate the three light paths intersecting at the first position in the container such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the first light sheet, second light sheet, and optical image.

[0123] In accordance with another aspect of the present invention, there is provided a printhead module for use in forming an object in a volume of a photohardenable composition, the printhead module comprising: a combination including: a. first optics for directing first excitation light along a first light path to a first position in a container for containing the volume of the photohardenable composition and second optics for directing second excitation light along a second light path to the first position in the container; and b. at least one optical alignment element, the optical alignment element being positioned or positionable such that at least one of the excitation lights passes through an optical alignment element along its respective light path before passing into the container.

[0124] Optionally, in cases where both of the light sheet and optical image pass through an optical alignment element, each of the first and second excitation lights can be oriented or orientable to pass through a single optical alignment element or different optical alignment elements.

[0125] Preferably, the two light paths are configured or configurable to facilitate the first and second light paths intersecting at the first position in the container such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the first and second excitation lights.

[0126] Preferably, the first light path enters a first input surface of the first optical alignment element at a first selected angle and the second light path enters a second light input surface of the second optical alignment element at a second selected angle. In accordance with another aspect of the present invention, there is provided a printhead module for use in forming an object in a volume of a photohardenable composition, the printhead module comprising: a combination including: a. first optics for directing a generated light sheet along a first light path to a first position in a container for containing the volume of the photohardenable composition and second optics for directing a generated optical image along a second light path to the first position in the container; and b. at least one optical alignment element, the optical alignment element being positioned or positionable such that the generated light sheet and / or the optical image passes through an optical alignment element along its respective light path before passing into the container.

[0127] Optionally, in cases where both of the light sheet and optical image pass through an optical alignment element, each of the light sheet and optical image can be oriented or orientable to pass through a single optical alignment element or different optical alignment elements.

[0128] Preferably, the two light paths are configured or configurable to facilitate the first and second light paths intersecting at the first position in the container such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the first and second excitation lights.

[0129] Preferably, the first light path enters a first input surface of the first optical alignment element at a first selected angle and the second light path enters a second light input surface of the second optical alignment element at a second selected angle.

[0130] In accordance with another aspect of the present invention, there is provided a printhead module for use in forming an object in a volume of a photohardenable composition, the printhead module comprising a combination including: a. first optics for directing a generated light sheet along a first light path to a first position in a container for containing the volume of the photohardenable composition and second optics for directing a generated optical image along a second light path to the first position in the container, and wherein the first optics and second optics are fixed or movable; and b. at least one optical alignment element being positioned or positionable such that each of the first and second light paths independently pass through an optical alignment element before passing into the container, wherein the first and second light paths are configured or configurable such that the first and second light paths intersect at the first position in the container. Preferably, the first light path enters a first input surface of the first optical alignment element at a first selected angle and the second light path enters a second light input surface of the second optical alignment element at a second selected angle.

[0131] In accordance with another aspect of the present invention, there is provided a printhead module for use in forming an object in a volume of a photohardenable composition, the printhead module comprising a combination including: a. first optics for directing a generated light sheet along a first light path to a first position in a container for containing the volume of the photohardenable composition and second optics for directing a generated optical image along a second light path to the first position in the container, and wherein the first optics and second optics are fixed or movable; b. a first optical alignment element being positioned or positionable such that the first light path passes through the first optical alignment element before passing into the container, and a second optical alignment element being positioned or positionable such that the second light path passes through the second optical alignment element before passing into the container.

[0132] In certain embodiments, the first optical alignment element includes a first element light input surface and a first element light output surface and the first optical element is positioned or positionable such that the first light path is preferably orthogonal to the first element input surface and the first element light output surface is optionally adaptable for direct or indirect contact with an outer surface of the container through which the light sheet and the optical image are directed into the container, and / or the second optical alignment element includes a second element light input surface and a second element light output surface and the second optical alignment element is positioned or positionable such that the second light path is preferably orthogonal to the second element input surface and the second element light output surface is optionally adaptable for direct or indirect contact with the outer surface of the container through which the light sheet and the optical image are directed into the container. When in use for 3D printing one or more objects in a volume, the two light paths of the print module are preferably configured or configurable such that the first and second light paths intersect at the first position in the container such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the light sheet and optical image.

[0133] In methods, systems, and printhead modules described herein that include the projection of an optical image, the optical image is typically perpendicular to the second light path.

[0134] In methods, systems, and printhead modules described herein, it can be desirable for the first light path and the second light path to be oriented or orientable to be orthogonal or substantially orthogonal, or close to 90-degrees, to each other where they meet or intersect at the first position in the volume of the photohardenable composition.

[0135] Alternatively, in methods, systems, and printhead modules described herein, the first light path and the second light path can be oriented or orientable to be at a non-90-degree angle to each other where they meet or intersect at the first position in the volume of the photohardenable composition.

[0136] Preferably the light sheet and optical image overlap at the first position. More preferably the overlap or intersection of the light sheet and the projected image is coplanar or substantially coplanar (e.g., the focal planes of the light sheet and the projected image overlap in a common plane).

[0137] Preferably the first light path and the second light path are each oriented at a non-90 degree angle to the surface of the container through which they enter the container.

[0138] In methods, systems, and printhead modules described herein, the first and second excitation lights (whether in a light sheet, optical image, or other configuration) are preferably oriented or orientable to enter the photohardenable composition from or through the same side of the container. Entry of the first and second excitation lights (whether in a light sheet, optical image, or other configuration) from or through the same side of the container can be particularly desirable to facilitate printing objects with a large size in two dimensions (e.g., a large two-dimensional crosssection).

[0139] An optical alignment element for use in the present invention typically includes at least one light input surface and a light output surface. Preferably an optical alignment element is positioned or positionable relative to a light path such the light path is orthogonal to the light input surface through which the light path passes into the optical element. An optical alignment element can be in direct or indirect contact with a surface of the container through which light path passes into the container. Preferred optical alignment elements comprise a prism or other prism optics which are suited for aligning the optical path of excitation light (whether in a light sheet, optical image, or other configuration) in the container of the photohardenable composition. Examples of prisms and other prism optics include optical prisms, including but not limited to, right angle prisms, dove prisms, triangular prisms, right triangular prims, equilateral prisms, assemblies or combinations of two or more prisms or prism optics. One or more prism faces can optionally include one or more coatings.

[0140] An optical alignment element is preferably appropriately sized for transmitting full cones of excitation light included in an optical projection (e.g., light sheet, optical image, or other configuration of excitation light) passing therethrough. Prisms that do not have faces that are at 45 degrees to the container can also be used. A prism can have any angle from 0-90 degrees. When prisms that do not have faces that are at 45 degrees to the container, it is preferable for the optical axis of the light sheet and projected optical image to enter a light input face of the prism at normal incidence and for the projection and light sheet to intersect in a common plane within the container. An example is shown in FIG 18(b).

[0141] Prism(s) used with projection and / or light sheet axes that are not normal to the input faces of the prisms can achieve a coplanar intersection of the optical image and light sheet at the first position, by, for example, selecting the refractive index of the prism appropriately (it will be different from the refractive index of the resin or photohardenable composition). An advantage of this approach can be reducing or avoiding back-reflection from the prism back along the optical axis into the first optics or light optics of the light generating system or second optics or projection optics of the projection system, where it can result in optical distortion or source instability.

[0142] Optionally, exchangeable prisms that have the same shape but a range of refractive indices (for example, made from different glasses) can be used so as to be able to accommodate a range of resin refractive indices.

[0143] Optionally, a fillable prism shell that can be filled with resin matching fluid can be used so as to be able to accommodate different resin refractive indices.

[0144] Optionally, exchangeable prisms that have a range of face angles so as to be able to accommodate a range of resin refractive indices can be used.

[0145] Optionally, tiltable prisms or prism surfaces can be used so as to be able to accommodate a range of resin refractive indices.

[0146] Other examples of optical alignment elements include an arrangement and / or combination including one or more facets, optical gratings, and / or other optical features that can be included in or at a surface of the container through which excitation light (e.g., configured as a light sheet, optical image, or other configuration) enters the container. Such arrangements and / or combinations can improve control of the angles at which the first and second optical exes intersect in the volume.

[0147] Preferably an optical alignment element is constructed from a material that has a refractive index that is the same as that of the container, the photohardenable composition, or both. An optical alignment element will preferably comprise a glass.

[0148] .The following Table 1 outlines a number of variables that can be taken into consideration in the selection process for an optical alignment element for use in embodiments of the present invention including excitation light configured as a light sheet or optical image and non-limiting examples ranges therefor, which can be independently selected for each variable. Table 1

[0149] In the above Table 1:

[0150] • Angles are with respect to system coordinates which are aligned with the container.

[0151] • Combinations of the above variables are preferably chosen such that the intersection angle in resin is 90deg so that the light sheet and projector focal plane are coplanar.

[0152] • Angle of prism face and angle of optic axis can be independently chosen for the light paths of the excitation light(s) (whether in a light sheet, optical image, or other configuration).

[0153] • Note that angle of incidence onto prism does not need to be normal.

[0154] • Note that refractive index of prism and refractive index of resin do not need to be the same, although it can be desirable for them to be similar.

[0155] • Note that intersection angle in resin can, but does not need to, be symmetric with respect to system coordinates. For example, the projector and light sheet angles inside the photohardenable composition can be symmetric with both being at the same angle inside the container (e.g., at 45 degrees). Alternatively, the projector and light sheet angles inside the photohardenable composition can be non-symmetric with the two angles being different inside the container, e.g., the projector at 35 degrees, and light sheet at 55 degrees, or other combinations of angles.

[0156] • If an optical alignment element comprising a prism is used for both projector and light sheet, two discrete prisms can be used or a single combined prism can be used.

[0157] • If using two discrete prisms, prism refractive index can be independently chosen for the light sheet and projector paths. Following Table 2 includes non-limiting examples of methods for varying the above listed variables:

[0158] Table 2

[0159] The above variations can be desirable for use of the printer with a range of resins having a range of refractive indices, to facilitate ease of alignment of printer components, to compensate for the manufacturing tolerance range of the variables.

[0160] FIGS. 1A and IB depict two examples of methods and systems of the present invention including two excitation lights (depicted as a light sheet and projected optical image) wherein one excitation light path passes through an optical alignment element (e.g., prism optics) before passing into the container of a photohardenable composition.

[0161] FIG. 1A depicts a preferred example wherein the photohardenable composition and the optical alignment element have the same refractive index. In the depicted example, the light sheet 100 is generated by the light sheet generating system 101 and directed into a light input surface 102 of the optical alignment element 103 (depicted by way of example as a 55 degree prism) at a 90- degree incidence angle (i.e., normal incidence). In the depicted example, the light path of the light sheet, after passing through the optical alignment element, into the container of the photohardenable composition 104 and the light path of the optical image 107 generated and projected by the projection system 105 into the container without passing through an optical alignment element, intersect in the photohardenable composition at an angle 106 of 90 degrees.

[0162] Additional information relating to an example of the system depicted in FIG. 1A that can be preferred includes:

[0163] • Refractive Index of Photohardenable Composition and the Optical Alignment Element: 1.5

[0164] • Light sheet: o Optical Alignment Element angle 55°° o Normal incidence onto Optical Alignment Element o Angle inside container = 55°

[0165] • Projector o Angle of incidence onto container = 59° o Angle inside container = 35°

[0166] • Intersection angle of light sheet and projection light paths in the photohardenable composition = 90°.

[0167] FIG. IB depicts a preferred example wherein the photohardenable composition and the optical alignment element have the same refractive index. In the depicted example, the projected optical image 107 is generated by the projection system 105 and directed into a first light input surface 102 of the optical alignment element 103 (depicted by way of example as a 55 degree prism) at a 90-degree incidence angle (i.e., normal incidence). In the depicted example, the light path of the projected optical image, after passing through the optical alignment element into the container of the photohardenable composition 104, and the light path of the light sheet 100 generated and projected by the light sheet generating system 101 into the container without passing through an optical alignment element intersect in the photohardenable composition at an angle 106 of 90 degrees.

[0168] Additional information relating to an example of systems and methods represented in FIG. IB that can be preferred includes:

[0169] • Refractive Index of Photohardenable Composition and the Optical Alignment Element: 1.5

[0170] • Projector: o Optical Alignment Element angle 55°° o Normal incidence onto Optical Alignment Element o Angle inside container = 55°

[0171] • Light sheet: o Angle of incidence onto container = 59° o Angle inside container = 35

[0172] • Intersection angle of light sheet and projection light paths in the photohardenable composition = 90°.

[0173] While the examples depicted in FIGS. 1A and IB show the two light paths intersecting in the photohardenable at a preferred angle of 90 degrees, in the methods, systems, and print modules described herein, an intersection close to 90 degrees is also preferred, as is any angle which facilitates the depth of field of the light sheet lying within the depth of field of the optical image .

[0174] In the inventions described herein, depending upon the object being printed and the accuracy tolerances therefor, other angles can be suitable for the intersection of the two light paths at the first position. The closeness to 90 degrees can depend on the thickness of the light sheet and the depth of focus of the optical image projection.

[0175] In the inventions described herein, preferably the overlap or intersection of the light sheet and the projected image in the common plane is substantially coplanar and more preferably coplanar.

[0176] In the inventions described herein, preferably the light path of an excitation light (whether as a light sheet, optical image, or other configuration) that passes through an optical alignment element before passing into a container of a photohardenable composition enters a light input surface of the optical alignment element at a selected angle with the light input surface. Examples of the selected angle include, but are not limited to an angle greater than zero degrees to less than 180 degrees, e.g., an angle in a range from about 15 degrees to about 165 degrees. It can be particularly desirable for a light path to enter the input surface of an optical alignment element at an angle of 90 degrees or substantially 90 degrees, as shown in the examples depicted in FIGS. 1A and IB.

[0177] In the inventions described herein, it can be particularly desirable for each of the first light path and second light path to be normal to the input surface of the optical alignment element at the point at which it enters the element and for the two light paths also meet or intersect at a substantially 90 degree, most preferably 90 degree, angle at the first position in the container. The closeness to 90 degrees can depend on the thickness of the light sheet and the depth of focus of the optical image projection.

[0178] In the methods and systems described herein, at the intersection of the two light paths at the first position, preferably the thickness of the light sheet lies within the depth of focus of the projected optical image at the first position, the depth of focus of the projected optical image lies within the thickness of the light sheet at the first position, or the thickness of the light sheet and the depth of focus of projected optical image are matched so they overlap in a common plane. In the methods and systems described herein, the optical alignment element is preferably optically coupled to the surface of the container through which the light sheet and optical image are directed.

[0179] In the methods and systems described herein, the first optics, second optics and optical alignment element(s) can preferably be locked or fixed in position throughout the printing process. Preferably such positions are fixed such that such that the first light path is normal to the light input surface of an optical alignment element through which the light sheet is directed and the second light path is normal to the light input surface of the optical alignment element through which the optical image is projected. Preferably the first light path and second light path additionally intersect in the photohardenable composition substantially at, and more preferably at, a 90 degree angle. Most preferably, the light sheet will be in plane with the focal plane of the optical image (wherein the optical image being orthogonal to its second light path) minimizing aberrations and image / printing non-uniformities.

[0180] FIGS. 18A and 18B depict examples of two embodiments of the present invention. FIG. 18 A shows the case where light sheet and projection light paths are preferably separated by 90 degrees: in one embodiment (a) the two optical path are at a 45 degree angle to the container, in the other (b) they are not, in case (b) a prism with angles other than 45 degrees is required (i.e., not a right angle or a Dove prism).

[0181] FIGS. 18A and 18B depict the intersection of the light sheet axis and projection axis at a preferred angle of 90 degrees. As discussed herein, other intersection angles can also be used.

[0182] FIGS. 18A and 18B show examples in which the light sheet path 1801 and the projection light path 1802 are separated by an angle of 90 degrees. In the example depicted in FIG. 18 A, the optical paths of the light sheet and projection are at a 45 degree angle to the container 1829. In the example depicted in FIG. 18B, the optical paths of the light sheet and projection are not at a 45 degrees angle to the container , in which case a prism 1805 with angles other than 45 degrees is utilized (e.g., not a right angle or a Dove prism). While in the two depicted example the intersection of the two light paths is shown with a 90 degree angle in the photohardenable composition, they may alternatively intersect at larger or smaller angles.

[0183] The methods, systems, and printhead modules described herein can facilitate making large parts. This is accomplished at least in part by the capability to move the container and optical systems relative to each other in a two-dimensional plane relative to the first position without altering the amount of resin that either light sheet or projected image have to travel through to reach the intersection, and furthermore without modifying the location of the projectors focal plane relative to the light sheet, and with minimal additional challenges with projector light vignetting as the build volume is increased. Preferably, an optical alignment element and the wall of the container through which an excitation light enters the container have the same index of refraction as the photohardenable composition.

[0184] The present invention is particularly advantageous for use in forming one or more objects that are suspended in the volume of the photohardenable composition during formation.

[0185] The methods, systems and printhead modules described herein can further be adapted for computer control.

[0186] The methods, systems, and printhead modules described herein can further include a first light source and a second light source. A light source can optionally be a component of a light generating system and or projection system or external thereto and in optical communication, with a light generating system, projection system, and / or printhead module during printing of one or more objects.

[0187] Preferably the first optics are configured for optical communication with a first light source and the second optics are configured for optical communication with a second light source.

[0188] Preferably the optical image is perpendicular to the second light path.

[0189] Optionally the first optics and second optics are fixed or movable with respect to each other.

[0190] Although, it can be desirable for the first optics and second optics to be fixed with respect to each other.

[0191] Preferably the first optics, the second optics and the optical alignment element(s) are locked or fixed in position throughout the printing process. Preferably such positions are fixed such that such that the first light path is normal to the light input surface of an optical alignment element through which the light sheet is directed and the second light path is normal to the light input surface of the optical alignment element through which the optical image is projected. Preferably the first light path and second light path additionally overlap or intersect in the photohardenable composition substantially at, and more preferably at, a 90 degree angle. Most preferably, the light sheet will be in plane with the focal plane of the optical image (wherein the optical image being orthogonal to its second light path) minimizing aberrations and image / printing non-uniformities.

[0192] Optics (e.g., first optics) used in directing the light sheet into the photohardenable composition in the methods, systems, and / or printhead modules described herein can be external to, and in optical communication with, the light sheet generating system or can be a component of the light sheet generating system used to generate the light sheet.

[0193] Optics (e.g., second optics) used in projecting the optical image into the photohardenable composition in the methods, systems, and / or printhead modules described herein can be external to the projection system or can be a component of the projection system used to generate the optical image.

[0194] Optionally, a light sheet generating system including optics (e.g., first optics) for directing the light sheet into the photohardenable composition can be included in a system or method described herein.

[0195] Optionally, a projection system including optics (e.g., second optics) for projecting the optical image into the photohardenable composition can be included in a system or method described herein.

[0196] Alternatively, other components of a projection system can be remote and in optical communication with the second optics. Similarly, other components of a light sheet generating system can be remote and in optical communication with the light sheet first optics. Mirrors, other optical components, and / or other known techniques can be used in such optical communication.

[0197] Optics for directing the light sheet into the photohardenable composition in the methods and systems described herein typically can include one or more lenses and / or mirrors.

[0198] Second optics for projecting or directing the optical image into the photohardenable compositions in the methods and systems described herein typically can include one or more lenses and / or mirrors.

[0199] In systems, methods, and / or printheads described herein including one or more optical alignment elements, the first light path and the second light path are preferably at an angle substantially 90 degrees, and more preferably 90 degrees, to each other.

[0200] Preferably each of the first light path and second light path enter the optical alignment element at an angle substantially 90 degrees, and more preferably 90 degrees, to the other and are configures to overlap or intersect in photohardenable composition included in a container at a substantially 90 degree angle, more preferably at a 90 degree angle, to each other.

[0201] Preferably the first light path and second light path enter its light input surface of an optical alignment element(s) at a substantially 90 degree, and more preferably 90 degree, angle to each other and meet in the container at a right angle.

[0202] Preferably the overlap or intersection of the light sheet and the projected image in the common plane is substantially coplanar and more preferably coplanar.

[0203] Preferably the first light path is normal to the first light input surface of the optical alignment element through which the light sheet is transmitted.

[0204] Preferably the second light path is normal to the second light input surface of the optical alignment element through which the optical image is transmitted. It can be particularly desirable for each of the first light path and second light path to be normal to the input surface of the optical alignment element at the point at which it enters the element and also for the two light paths to meet or intersect at a substantially 90 degree, more preferably 90 degree, angle at the first position in the container. The closeness to 90 degrees can depend on the thickness of the light sheet and the depth of focus of the optical image projection.

[0205] As mentioned above, preferably the first optics, the second optics, and the optical alignment element(s) are locked or fixed in position throughout the printing process. Preferably such positions are fixed such that such that the first light path is normal to the light input surface of an optical alignment element through which the light sheet is directed and the second light path is normal to the light input surface of the optical alignment element through which the optical image is projected. Preferably the first light path and second light path additionally intersect in the photohardenable composition substantially at, and more preferably at, a 90 degree angle. Most preferably, the light sheet will be in plane with the focal plane of the optical image (wherein the optical image being orthogonal to its second light path) minimizing aberrations and image / printing non-uniformities.

[0206] Preferably, the optical alignment element and the wall of the container through which an excitation light enters the container have the same index of refraction as the photohardenable composition.

[0207] Preferably there is no air gap between the photohardenable composition and the inner surface of a selected region of the container through which the light sheet and optical image are directed into the volume to minimize or eliminate total internal reflection (TIR).

[0208] In the methods and systems described herein, an optical image can include any optical projection generated by an optical image projection system. Examples of optical images include, without limitation, a two-dimensional image, a patterned or unpatterned two-dimensional arrangement, a line of light, or a single point of light. While an optical image may be described as a two-dimensional image, in printing an object, a two-dimensional image can typically represent a two-dimensional slice of an object to be printed. When projected by excitation light, a two- dimensional optical image typically has a thickness dimension perpendicular to second light path.

[0209] Methods, systems, and printheads in accordance with the present invention include an optical alignment elements between the first optics (whether included in the light sheet generator or external thereto) and a container and between the second optics (whether included in the projection system or external thereto) and the container. Optionally a single optical alignment element for receiving both the light sheet and optical image or separate optical alignment elements for separately receiving the light sheet and optical image can be used. Preferably the first light path along which the light sheet is directed into an optical alignment element is substantially normal, more preferably normal, to the face of the element through which the light sheet is directed. Preferably the second light path along which the optical image is projected into the optical alignment element is also substantially normal, more preferably normal, to the face of the element through which the optical image is projected. More preferably, the first light path and second light path are orthogonal to each other and intersect at a substantially 90-degree angle, more preferably at a 90 degree angle at a first position with both the light sheet and optical image entering the container through a single face of the container.

[0210] The optical alignment element(s) is(are) preferably optically coupled to a selected region of a surface of the container through which the light sheet and optical image enter the container. The container is positioned such that the first position is located at a selected location in the photohardenable composition included therein.

[0211] Preferably there is no air gap between the photohardenable composition and the inner surface of a selected region of a surface of the container through which the light sheet and optical image are directed into the volume to minimize or eliminate total internal reflection (TIR).

[0212] Preferably the x,y dimensions of the optical alignment element or light sheet elements, if separate ones are used for the light sheet and optical image, are selected to accommodate transmission of the full width of light included the light sheet and / or optical image transmitted therethrough, as the case may be.

[0213] FIG. 2 A depicts an example of a system 201 for forming an object by volumetric printing in accordance with an aspect of the present invention that includes a single optical alignment element 207. The illustrated system 201 includes a first optical system 202 comprising a light sheet generating system (such system also being referred to herein as a light sheet generator) that incorporates first optics (not separately shown) for directing a light sheet 203 through a first light input surface 212 and a light output surface 213 of an optical alignment element 207 into a container that includes volume of a photohardenable composition 204. The illustrated system also includes a second optical system comprising a projection system 205 that incorporates second optics (not separately shown) for projecting an optical image through a second light input surface 214 and the light output surface 213 of the optical alignment element into the container including the volume. The optical alignment element is depicted in the figure by way of example as a coupling prism. The light sheet generator including first optics and second projection system including second optics are positioned for the light sheet and optical image to overlap or intersect at a first position 206. The container is initially positioned for the first position to be located at a selected location in the volume. After the light sheet and optical image overlap or intersect at the selected location to alter at least one property or induce hardening of the photohardenable composition, the container can be moved in the x and / or y directions to change the location of the first position to a next selected location for continuing to form the object. The optical alignment element 207 is preferably in direct contact with a surface 215 of the container 204 including the volume and / or is optically coupled to such container surface by including a refractive-index matching coupling fluid 209 at the interface between the optical alignment element and the container. Without coupling the optical alignment element to the photohardenable composition or container surface, light beams can undesirably undergo total internal reflection (TIR) and / or exit the optical alignment element on the side opposite the input surface. The light sheet passes along the first light path from exiting the light sheet generating system through a first light input surface 212 and the light output surface 213 of the optical alignment element 207 through a surface 213 of the container and into the volume 204. The optical image is projected along the second light path from exiting the projection system through a second light input surface 214 and light output surface 213 of the optical alignment element 207 through the same surface 213 of the container and into the volume 204. The optical image is perpendicular to its second light path. While a translation mechanism is not shown, an arrow 217 indicates an example of motion of the container (or resin vat) in the x directions relative to the position of the light sheet generator and projection system, although as shown movement in the x and y direction is possible. (Orientation axes for the drawing are also shown.)

[0214] Preferably the first light path and the second light path intersect at a 90 degree angle with the intersection of light sheet and optical image at the first position being coplanar.

[0215] Preferably the positions of the first optics and the second optics are fixed or locked relative to each other and the location of the intersection of the light sheet and optical image at the first position in the volume is selected and can be changed by moving or positioning the container relative to the first position and / or moving the arrangement including the first optics and the second optics and optical alignment element to the position of the container.

[0216] FIG. 2B depicts a system similar to that shown in FIG. 2A additionally pointing out the “intersection angle” 220 between the light sheet path 250 and the optical projection path 260 at the focal planes of the light sheet and projection systems in the photohardenable composition (also referred to herein as resin or printing resin). (The term “optical axis” refers to excitation light as it exits from the projection system / light sheet generating system, as the case may be, BEFORE entry into the optical alignment element.)

[0217] For a preferred intersection angle of 90 degrees, the light sheet and projected optical image focal plane are co-planar, which is preferred for accurate printing.

[0218] A method and / or system of the present invention can further include a housing or enclosure in which the projection system, light generating system and at least one optical alignment element are contained. FIG. 3 depicts an example of a method and system in accordance with the present invention including one optical alignment element through which a light sheet generated by a light sheet generating system including light sheet optics (which may also be referred to herein as first optics) and an optical image projected by a projection system including projection optics (which may also be referred to herein as second optics) before passing into the container of a photohardenable composition. The configuration of the system depicted in FIG. 3 shows the container on top of the enclosure / housing. Preferably the container or housing / enclosure is moveable with respect to the other to facilitate relocating the first position where the light sheet and optical image intersect or overlap to a selected location in the photohardenable composition included in the container.

[0219] The example of the arrangement depicted in FIG. 3 includes a light sheet generating system330 , a projection system 331 and an optical alignment element 332 included in an enclosure 329. The light sheet is directed along its axis 336 through the first light input surface 334 and light output surface 335 of the optical alignment element 332 into a volume of photohardenable composition 338 included in a container 339. The optical image (not shown) is projected from the projection system 331 along the optical image second light path 340 through the second light input surface 337 and light output surface 335 of the optical alignment element 332 into the volume of the photohardenable composition 338. The optical image (not shown) can typically comprise a two- dimensional optical image that is perpendicular to the second light path 340. (Orientation axes for the drawing are also shown.) In the depicted example, the container is above the arrangement including the light sheet generating system 330, the projection system 331, , and the optical alignment element 332 (e.g., coupling prism). Other orientations of the container and the arrangement relative to each other can also be useful. The interfaces between the container, enclosure, and optical alignment element are preferably optically coupled with a couple gel or material or other optical coupling technique to prevent or eliminate undesired reflection or scattering.

[0220] A system can optionally further include a translation mechanism to facilitate movement, for example, of the container, during printing. A translation mechanism can optionally be included between the container and an arrangement including the first optics or light sheet generator, the second optics or projection system, and any optical alignment elements.

[0221] FIG. 4 illustrates an example of a system in accordance with the present invention that includes a printhead 400 including two optical alignment elements 441, 451 positioned in contact with a container 453 including a photohardenable composition 446. In the depicted example, the light sheet and optical image are shown with each being directed into the container through different optical alignment elements and into the photohardenable composition. The depicted example includes first optics 440 that direct a light sheet 445 along the first light path from the first optics, through a first light input surface 441 and first light output surface 442 of a first optical alignment element 443, and through a surface 444 of a container 453 including a volume of a photohardenable composition 446. The depicted example also includes second optics 447 that project an optical image along the second light path from the second optics through a second light input surface 449 and second light output surface 450 of a second optical alignment element 451 and through the same surface 444 of the container 453 including the volume of the photohardenable composition 446 with the optical image being perpendicular to the second light path. The first optics and the second optics are positioned and oriented such that the light sheet and optical image overlap or intersect at the focal plane of the optical image at a first position 452. Preferably the positions of the first optics or light sheet generating system and the second optics or projection system are fixed or locked relative to each other and the location of the first position in the volume is selected and can be changed by moving or positioning the container including the volume relative to the first position and / or the position of the arrangement including first optics, the second optics, and first and second optical alignment elements relative to the position of the container. (Orientation axes for the drawing are also shown.)

[0222] In a preferred embodiment, the relative position of an optical projection comprising a light sheet and an optical image comprising an optical image stays fixed with the photohardenable composition for a given z-depth. This allows the container (which may also be referred to herein as a vat) including a volume of the photohardenable composition (which may also be referred to herein as a resin or printing resin) to move only in x-y to print a 3D object.

[0223] The depth can be set by the projected optical image and should be suitable to print large devices such as smartphone assemblies, dental devices, microfluidic devices, optics, etc. This allows a 3D printer to function with only x,y-translation which can reduce complexity and cost. The capabilities of the selected translation stage or other translation mechanism and the x,y dimensions of the container are considerations in determining the extent of travel in the x-y directions.

[0224] It may be desirable to move the focal plane of a projected optical image 470 (as shown in FIG. 5A) or light sheet 445 (as shown in FIG. 5B) during printing. For example, the projected image and light sheet can be translated along its respective light path to improve uniformity and resolution of the print. The same concepts can work with one or both of the light sheet and optical image being directed through an optical alignment element 490 before entering the container 453 including the photohardenable composition 446. (Orientation axes for the drawing are also shown.)

[0225] FIGS. 6A and 6B depict diagrams of a cross-section of two examples of systems and methods in accordance with the present invention. FIG. 6A depicts an example that includes a first light path for a light sheet 601 generated by a light sheet generating system (including first optics (not shown)) 602 passing through a first optical alignment element 603 (e.g., depicted as a right angle prism) into a container 629 including a volume of a photohardenable composition 610 and a second light path 604 for a projected optical image (also referred to herein as an optical image) projected by a projection system (including second optics (not shown) 605 passing through a second optical alignment element 606 (e.g., depicted as a right angle prism) into the container 629 including a volume of the photohardenable composition 610 with the light sheet and projected optical image intersecting or overlapping at the first position 611. The container is positionable relative to the first position such that the intersection is at a selected position in the photohardenable composition for printing one or more objects.

[0226] Additional information relating to an example of the systems and methods represented in FIG. 6A that can be preferred includes:

[0227] • Two discrete Optical Alignment Elements

[0228] • Symmetric Light sheet and projector orientations (with respect to system coordinates, e.g., projector and light sheet both at same 45°angle inside the container)

[0229] • Refractive Index of the Photohardenable Composition and Optical Alignment Element: 1.5

[0230] • Optical Alignment Element angle 45°

[0231] • Normal incidence onto Optical Alignment Element

[0232] • Angle inside container = 45°

[0233] • Intersection angle of light sheet and projection light paths in the photohardenable composition = 90°.

[0234] FIG. 6B depicts an example that includes a first light path for a light sheet 620 generated by a light sheet generating system 621 and a second light path 622 for a projected optical image projected by a projection system 623 (FIG. 6B) with each light path passing through the same optical alignment element 625 (e.g., a dove prism). The depicted examples show the light paths for the light sheet and projected optical image intersecting in the photohardenable composition 610 in the container 629 at a preferred angle of 90 degrees with the light sheet and projected optical image intersecting or overlapping at the first position 630 and also shows each of the optical axes entering the respective light input surfaces of an optical alignment element at preferred angle of 90 degrees to the input surface.

[0235] Additional information relating to an example of the systems and methods represented in FIG. 6B that can be preferred includes:

[0236] • One Optical Alignment Element

[0237] • Symmetric Light sheet and projector orientations (with respect to system coordinates, e.g., projector and light sheet both at same 45°angle inside the container)

[0238] • Refractive Index of the Photohardenable Composition and Optical Alignment Element: 1.5 • Optical Alignment Element angle 45°

[0239] • Normal incidence onto Optical Alignment Element

[0240] • Angle inside container = 45°

[0241] • Intersection angle of light sheet and projection light paths in the photohardenable composition = 90°.

[0242] FIG. 7 depicts a diagram of a cross-section of an example of systems and methods including light sheet generation system 702 and a projection system 705 and methods in accordance with the present invention that includes two light paths (e.g., a light sheet 701 and a projected optical image 704) passing through a single optical alignment element 707 wherein the light sheet and projection angles inside the container 729 are not the same, e.g., are not symmetric.

[0243] Additional information relating to an example of the systems and methods represented in FIG. 7 that can be preferred includes:

[0244] • Refractive Index of the Photohardenable Composition and Optical Alignment Element: 1.5

[0245] • Light sheet: o Optical Alignment Element angle 60° o Normal incidence onto Optical Alignment Element o Angle inside container = 60°

[0246] • Projector: o Optical Alignment Element angle 30° o Normal incidence onto Optical Alignment Element o Angle inside container = 30°

[0247] • Intersection angle 730 of light sheet and projection light paths in the photohardenable composition = 90°.

[0248] FIG. 8 depicts a diagram of a cross-section of an example of systems and methods in accordance with the present invention including a light sheet generation system 802 and a projection system 805 and a light sheet axis 801 and a projected optical image axis 804 that are not normal to the light input faces of the optical alignment element 807. Add ref ## from drawing

[0249] Additional information relating to an example of the systems and methods represented in FIG. 8 that can be preferred includes:

[0250] • Symmetric Light sheet and projector orientations (with respect to system coordinates, e.g., projector and light sheet both at same 45°angle inside the container 829)

[0251] • Refractive Index of the Photohardenable Composition and Optical Alignment Element: 1.5

[0252] • Optical Alignment Element angle 30°

[0253] • Angle of incidence 23° onto Optical Alignment Element Angle inside container = 45°

[0254] Intersection angle 830 of light sheet and projection light paths in the photohardenable composition = 90°.

[0255] FIG. 9 depicts a diagram of a cross-section of an example of systems and methods in accordance with the present invention including a light sheet generation system 902, a projection system 905, a light sheet axis 901, a projected optical image axis 904, an optical alignment element 907, and a photohardenable composition included in the container 929 , wherein the optical alignment element has a refractive index, n i. and the photohardenable composition has a refractive index, m, that are different from each other.

[0256] Additional information relating to an example of systems and methods represented in FIG. 9 that can be preferred includes:

[0257] • Symmetric Light sheet and projector orientations (with respect to system coordinates, e.g., projector and light sheet both at same 45°angle inside the container)

[0258] • Photohardenable composition refractive index 1.4

[0259] • Optical Alignment Element refractive index 1.7

[0260] • Normal incidence onto Optical Alignment Element

[0261] • Optical Alignment Element angle 35°

[0262] • Angle inside container = 45°

[0263] • Intersection angle 930 of light sheet and projection light paths in the photohardenable composition = 90°.

[0264] FIGS. 10A and 10B depict diagrams of a cross-section of two examples of systems and methods in accordance with the present invention. FIG. 10A depicts an example of systems and methods that include an optical projection system 1001 (including second optics (not shown)) for projecting an optical image along an optical image projection pathl002 through a first optical alignment element

[0265] 1003 to a first position 1004 in a container 1005 including a photohardenable resin and two light sheet generating systems 1006, 1007 and a second optical alignment element 1008 on an opposite side of the container from the first optical alignment element 1003. Each of the first and second light sheet generating systems generate and direct a light sheet through the first and second optical alignment elements, respectively, to the first position where the first light sheet 1009 and second light sheet 1010 preferably overlap in a common plane and also overlap with the projected optical image to induce hardening or alteration of the photohardenable composition at the first position

[0266] 1004 upon exposure to the first and second lights sheets and projected optical image. Preferably, the light paths of the first and second light sheets intersect with light path of the projected optical image at a preferred intersection angle of 90 degrees. Each of the first and second light sheets and optical image preferably enter a light input surface of its respective optical alignment element at a 90 degree angle.

[0267] FIG. 10B includes a light sheet generating system 1006 and reflection optics 1014 for reflecting the generated light sheet 1009 passing out of the container 1005 back through the container and a projection system 1001 (including second optics (not shown)) for projecting an optical image along an optical image projection pathl002. The depicted system also includes a two optical alignment elements 1003, 1008 on opposite sides of the container with the generated light sheet 1009 and the projected optical image passing through the first optical alignment element to intersect at the first position 1004 in the container of the photohardenable composition 1005. The reflected light sheet 1015 is directed through the second optical alignment elements to the first position 1004 where it preferably overlaps in a common plane with the generated light sheet 1009 and projected optical image 1002 to induce hardening or alteration of the photohardenable composition at the first position 1004 upon exposure to the first and second lights sheets and projected optical image. Preferably, the light paths of the generated light sheet 1005 and the reflected light sheet 1015 intersect with light path of the projected optical image at a preferred intersection angle of 90 degrees. Each of the generated light sheet, optical image, and reflected light sheet preferably enter a light input surface of its respective optical alignment element at a 90 degree angle.

[0268] FIG. 11 illustrates another example of a system in accordance with the present invention. In this example, the system includes a light sheet generator 1102 (which includes optics that are not separately shown) for directing a light sheet 1103 along a first light path into the container 1109 and a projection system 1105 (which includes second optics that are not separately shown) for projecting an optical image along a second light path 1108 into the container. (The planar face of an optical projection is typically orthogonal to the second light path.) The system further includes an optical alignment element 1107. While the depicted example of the optical alignment element comprises a right angle prism, other optical alignment elements can be used.. The light sheet generator and projection system are preferably aligned with the optical alignment element such that the light sheet 1103 and optical image directed along the second light path 1108 pass through the optical alignment element to overlap or intersect at a first position 1110 in a container movable with respect to the first position. The container is positioned for the first position 1110 to be located at a selected location in a photohardenable composition included in the container 1109. The light sheet and optical image preferably overlap or intersect in a common plane at the first position to alter or induce hardening (e.g., by cross-linking or photopolymerization) of the photohardenable composition at the selected location. The container can be moved in x-y directions to change the position of the first position to a different selected location whereby the photohardenable composition is altered or hardening of the photohardenable composition is induced at the different position. The optical image at each different selected location typically comprises a sequential two-dimensional slice of the object to be printed. The optical images are sequenced. The container can be sequentially moved for formation of the full or partial object. Preferably, the optical systems are locked in position throughout the print requiring no movement thereby. (As depicted, the y axis is in / out of the page.)

[0269] Preferred configurations of methods and systems described herein including a light sheet generating system and a projection system that are locked or fixed with respect to each other and any included optical alignment element(s). Such locked or fixed configuration can facilitate several advantages including: the container can be moved infinitely in a two-dimensional direction, e.g., the x-y direction to make larger area prints of even upwards of 10 centimeters in at least one dimension and the light sheet is in plane with the focal plane of the optical image minimizing aberrations and imaging / printing nonuniformities.

[0270] Preferred configurations of printhead modules described herein including first optics and second optics that are locked or fixed with respect to each other and any included alignment element(s) can facilitate similar advantages.

[0271] FIG. 12 illustrates a perspective view of an example of a volumetric surface printer that includes a translation mechanism 1229. For example, a user can place a container 1221 that includes a photohardenable composition on a surface 1222 of an enclosure 1223 that includes a light sheet generator or light sheet generating system 1224 and a projection system 1225 aligned with an optical alignment element 1228 such that the light sheet and optical image overlap or intersect in a common plane at a first position 1227 and through which surface the light sheet and optical image pass into the container. To print an object 1226, the container including the photohardenable composition is positioned for the overlap or intersection of the light sheet and optical image at the first position to be located at a selected location in the photohardenable composition for altering or including hardening (e.g., by cross-linking or photopolymerizing) the photohardenable composition at the selected located, following which the position of the container can be translated it in a two- dimensional plane, e.g., in x-y directions, by the translation mechanism so that the first position is repositioned to a different selected location in the photohardenable composition to alter or photopolymerize the composition at the different selected location. Typically, in printing an object, the optical image projected to a different selected location is different from a previous optical image. For example, an optical image is typically a two-dimensional slice of the object to be printed, with each successive image being a sequential two-dimensional slice of the object. The process is typically continued until the desired object is formed. Other orientations of the container, enclosure and parts included therein can be useful.

[0272] While the depicted example includes a light sheet generator and projection system in the enclosure, the enclosure can alternatively include first optics and second optics that are aligned with an optical alignment element such that the light sheet and optical image overlap or intersect in a common plane at a first position. When only first optics and second optics are included in the enclosure, the first optics and the second optics are respectively in optical communication with a remote light sheet generator and remote projection system.

[0273] In a variation of the depicted example, the container can stay stationery and the arrangement including the light sheet generator, projection system, and optical alignment element below can move in the x-y directions.

[0274] FIG. 13 illustrates another example of a system in accordance with the present invention. In this example, the light path of a light sheet 1301 generated from a light sheet generator 1312 (which includes optics (not separately shown) for directing the light sheet into the container 1319) and the light path 1302 of an optical image projected from a projection system 1315 (which includes second optics (not separately shown)) are aligned with the aid of an optical alignment element (depicted as prism) 1317 into a container 1319 of photohardenable composition. The depicted system further includes optical alignment element 1317 which is separated from the container surface by an optically transparent spacing element 1316 (depicted in the illustrated example as a window). The light sheet generator, projection system, and optical alignment element (or optical alignment elements, if separate optical alignment elements are used for the light sheet and optical image) are preferably aligned such that the generated light sheet and optical image pass through the optical alignment element(s) and overlap or intersect at a first position 1311. The container 1319 including a photohardenable composition is position able for the first position to occur at a selected location in the photohardenable composition. At the first position at the selected location, the photohardenable composition is altered or hardened in the process of printing or forming the object. Preferably the light sheet and optical image overlap or intersect in a common plane at the first position 1311 As the container including the photohardenable composition moves in x-y directions and images are sequenced a 3D part is formed. (As depicted, the y axis is in / out of the page.; both x and y axes are parallel to the optically transparent spacing element 1316.)

[0275] The further inclusion of the optically transparent spacing element 1316 allows for physical separation between the printing area where liquids reside and the sensitive optics. It is also a way to create a surface to which the container can be coupled for printing. At each interface (e.g., the optical alignment element -the spacing element and the spacing element and container surface) optical coupling gels and materials can optionally be used to eliminate or minimize reflections and scattering at the surfaces.

[0276] The container can also move in z using a liquid interface in place of the window and moving and refocusing the projection system (e.g., for generating a two-dimensional (2D) optical image) and light sheet generator if desired. The inclusion of the optically transparent spacing element can allow physical separation between the printing area (e.g., the photohardenable composition included in the container) and the arrangement of the first optics and the second optics and optical alignment element(s). (As mentioned herein the first optics and the second optics can optionally be integrated in the light sheet generator and projection system, respectively, or they can be external thereto.) The optical spacing element can further provide a surface to which the container can be optically coupled. It may be desirable for the interface between the optical alignment element(s) and the optically transparent spacing element and / or the interface between the container and optically transparent spacing element to include an optical coupling gel or material to minimize or eliminate reflections and / or scattering at the interfacing surfaces.

[0277] A coupling optic, such as a window, can have a refractive index that is the same as or different from that of the optical alignment element and the photohardenable composition.

[0278] Optionally, by choice of window thickness and refractive index, the z height of printing within the photohardenable composition can be adjusted.

[0279] Alternatively, or additionally, inclusion of a liquid interface in place of, or in addition to, the optically transparent spacing element can permit the container to also move in the z direction for moving and refocusing the projection system and light sheet generator, if desired.

[0280] FIG. 14 illustrates an example of a system and method in accordance with the present invention in which the optical alignment element 1401 includes an integrated chamber 1402 for including a photohardenable composition or a container 1420 for containing a photohardenable composition. (An optical alignment element can include a single piece or multiple pieces that are sealed or other otherwise joined together.) A light sheet generating system 1403 and a projection system 1404 are arranged for the light sheet generator to direct a light sheet 1405 through the optical alignment element 1401 along its light path into the chamber 1402 for containing a container 1420 including the photohardenable composition and for the projection system to project the optical image (not shown) through the optical alignment element into the container along its light path 1415 such that the light sheet and optical image to overlap or intersect at a first position 1408. Optionally, when a container is included in the chamber, as shown in the figure, an interface index- matched fluidic seal or bearing 1410 can be included around the container in the chamber. (While the figure depicts a light sheet generating system and projection system that include integrated first and second optics, respectively, a system can optionally include a light generating system and / or a projection system in which the first optics and second optics, respectively, are not integrated but instead remote and in optical communication with the light sheet generated by other part of the light sheet generating system and optical image projected by the other part of the projection system.

[0281] Preferably the light sheet and optical image overlap or intersect in a common plane. The light sheet light path and optical image light path are preferably orthogonal to each other and overlap or intersect at the first position at a 90 degree angle.

[0282] It is preferable for the first light path to be at a 90 degree angle with the light sheet input surface 1409 of the optical alignment element and for the second light path to be at a 90 degree angle with the optical image input surface 1416 of the optical alignment element.

[0283] The optical image is preferably at a 90 degree angle to the second light path 1415.

[0284] The chamber is preferably sized to accommodate movement of the container 1402 within the chamber in the x, y, and optionally z directions for printing at different selected locations in the photohardenable composition included therein. The integrated optical alignment element - chamber structure can be a single piece or multiple pieces that are sealed together. Preferably the integrated unit is adapted for the chamber to be opened and closed for inserting and removing the container. It can be desirable for the size of the container to be selected e relative to the internal size of the chamber to permit inclusion an index-matched fluidic seal or bearing. The index-matched fluidic seal or bearing can surround all external surfaces of the container included in the chamber. If the container is positioned against or on an internal surface of the chamber, the index-matched fluidic seal or bearing can surround exposed surfaces of the container situated in the chamber and / or any space(s) between the outer surfaces of the container and an internal surface(s) of the chamber. (Orientation axes for the drawing are also shown.)

[0285] Optionally a container suspended in a fluid bearing system can be moved magnetically when a container containing a magnetizable material is used.

[0286] The chamber can optionally further include a translation mechanism (not shown) for moving the position of the container included therein.

[0287] Methods and systems described herein can optionally be used to overprint additional features on a previously made part. In such case, the previously made part is included in the container and the desired additional features are printed on a surface thereof. For example, the container including the previously made part and photohardenable composition and positioned for the first position to be located at a selected location on the surface of the previously made part and the container can thereafter be repositioned to print additional features at different selected location. In some instances, it may be desirable to reprint at a same selected location before repositioning the container for printing at a different selected location.

[0288] FIG. 15 depicts an example of a method and system in accordance with the present invention for overprinting features or other structures 1515 on or over a surface or region of an object 1516 that is included in a volume of a photohardenable composition included in a container 1510. The depicted example includes a light sheet generation system 1502 and a projection system 1505 and a light sheet axis 1501 and a projected optical image axis 1504 that are normal to the respective light input faces of the optical alignment element 1507. In the depicted example, an optical alignment element 1507 is positioned on a surface of the container 1510 including the volume of the photohardenable composition. Optionally an index-matching coupling fluid 1511 can be included between the interfacing surfaces of the optical alignment element and the container.

[0289] FIG. 16 illustrates a side view of a schematic example of a projection system (e.g., for generating a two-dimensional (2D) optical image) for use in the methods and systems described herein.

[0290] In the figure, the optical projection system includes a spatial light modulator, preferably a digital micromirror device (DMD) 1605, a light source 1606 in combination with optics 1607 (which may also be referred to as illumination optics) to illuminate the DMD. Such optics can optionally comprise beam conditioning and condenser optics and relay optics. A light source comprising a laser can be preferred. Second optics (which may also be referred to as projection optics) 1609 are positioned between the DMD and container (not shown) for magnifying and projecting a focused first optical projection of excitation light comprising a two-dimensional image into the container. Optionally, one or more prisms 1610 can be positioned between the DMD and second optics. In the depicted example, an optical image 1611 (e.g., a two-dimensional slice of the object to be printed) is projected for the focal plane of the optical image projection.

[0291] A computer (designated as “PC”) 1621 is also shown. Software can be used to coordinate generation of the desired two-dimensional pattern from the spatial light modulator so that the part is developed plane by plane along the z axis with high axial resolution. Selection of computer controls and software is within the skill of the person of ordinary skill in the relevant art.

[0292] As depicted, the optical projection system comprises a spatial light modulator (e.g., a liquid crystal on Silicon (LCOS) display, digital micromirror device (DMD), liquid crystal display (LCD), or a micro-LED (pLED) display. FIGS. 17A and 17B illustrate different views of an example of a light sheet generator.

[0293] FIG. 17A depicts an yz view and FIG. 17B xy view of an example of light sheet generating system which can be used to generate a plane of light or light sheet. The major face of the plane of light or light sheet is preferably orthogonal to the second light path. The light sheet generator 1733 in the example depicted in FIGS. 17A and 17B includes a light source 1751 which directs collimated light through an optical arrangement including a Powell lens 1752, a first cylindrical lens 1753, a second cylindrical lens 1754, an optional third cylindrical lens 1755 and into the container 1756. An example of a collimated light source 1751 is a free space laser. The use of cylinder lenses is preferred as this permits independent shaping of the light distribution in orthogonal directions. Examples of cylindrical lenses are off the shelf piano convex cylindrical lenses with focal lengths in the range 25mm - 250mm, available from Thorlabs.

[0294] Optionally, a galvanometer, polygon scanner, MEMS scanner, diffractive optical elements, cylindrical lenses, or axicon lenses, with or without additional optical components, can be included in place of the Powell lens.

[0295] Light sources included in the system are preferably selected taking into consideration the photohardenable liquid being used and the hardening mechanism therefor. Such considerations include the wavelength(s) preferred for the particular photo hardening mechanism and power levels preferred therefor. Selection of suitable light sources is within the skill of the person of ordinary skill in the relevant art.

[0296] While the figures depict examples of systems including a container, optionally the container can be included as a component of a system or separately provided for inclusion prior to use.

[0297] Optionally any light source can be included as component of a light sheet generator or projection system or can be separately supplied for inclusion in the system prior to use.

[0298] Spatial light modulators (SLMs) can be used in or with second optics as either amplitude modulators in combination with projection lens to form images in the resin or as wavefront encoding devices to form a phase or complex amplitude modulation on the wavefront in a holographic configuration.

[0299] Other geometries such as using a single SLM in combination with a scanning laser to form an orthogonal light sheet (of similar or different wavelength) to activate a layer for photopolymerization.

[0300] Forming multiple parts in the same resin vat can be desirable by, e.g., translating the projection system, e.g., SLM or using multiple projection systems, e.g., SLMs, from any direction that allows.

[0301] Multiple sets of a light sheet generator and projection system can be used for printing multiple objects in a container to allow for faster printing.

[0302] For example, more than one arrangement or configuration including the first optics or a light sheet generator and the second optics or a projection systems, which arrangement or configuration may further include one or more optical alignment elements, can be arranged around the resin vat or container including a photohardenable composition to increase volume or speed of printing. It is preferable when more than one arrangement or configuration is implemented that the paths of the light sheets and paths of the optical images from any two such arrangements or configurations do not overlap or intersect to avoid crosstalk. Alternative configuration may utilize different types of 2D imagers, including 2D scanners, liquid crystal on silicon (LCDS) display, vertical cavity lasers (VCLs), microLEDs or grating light valves.

[0303] The methods and systems of the present invention can facilitate printing an object in a volume without movement along one axis (e.g., the z-axis). The methods and systems of the present invention can facilitate projecting a light sheet and optical image projection into a volume from one side of a vat or other container that includes photohardenable composition.

[0304] A system and / or method in accordance with the present invention can further include a camera or detector system to monitor the curing region or for calibration purposes. Such camera or detector system can be positioned, e.g., on the opposite side of the printhead.

[0305] An example of a process flow for an example of a method of the present invention or for use with a system of the present invention includes:

[0306] 1. A three-dimensional (3D) object file is sliced into a set a two-dimensional (2D) image slices of a given thickness.

[0307] 2. Insert resin-container onto printer (or pour resin into container).

[0308] 3. Optionally apply environmental control (temperature, degas, purge, sparge, gas curtain (air, nitrogen (N2), argon, or other inert gas)) to the resin container.

[0309] 4. Expose resin simultaneously or subsequent (preferably closely timed sequential exposure with an optical image (e.g., an optical 2D projection of a part slice) and an overlapping or intersecting light sheet.

[0310] 5. Change the position of at least one of (a) the container including the photohardenable composition or (b) (i) the arrangement including the first optics (or light generating system) and second optics (or projection system) or (ii) the printhead module relative to the other in either x-y to expose the next slice; repeat as necessary until the entire part is formed in the photohardenable resin. (Optionally the container can be translated in discrete steps or otherwise can be translated at a continuous velocity.)

[0311] 6. Remove part from container, e.g., without limitation, by use of filtering, by manual collection of the part from the surrounding liquid, with possible assistance from solvent, heat, agitation, etc.

[0312] 7. Optionally wash off residual material from object using solvent, air curtain, centrifugal force, gravity, heating, etc.

[0313] 8. Optionally post-cure object, e.g., without limitation, in fluid, in air, in inert gas, apply UV and / or heating as required. Other process flows can also be used.

[0314] Software can be used to determine the best sequence of 2D projections. In its simplest form such software can control a printer to print one 2D slice at a time.

[0315] The photohardenable composition can be introduced into the system in a sealed container. Examples for introducing the photohardenable composition into the container include, but are not limited to, by fluidic control or by pouring the photohardenable composition into the container.

[0316] The first optics and second optics can be positioned on top, below or to the side of the container.

[0317] After printing, the object can be removed, e.g., without limitation, by introducing a solvent and / or agitation to lower the viscosity of the uncured polymer; a gripper or stage (permanent or 3D printed) can be used to hold the part in place during this process.

[0318] Optionally an anti-reflection (AR) coatings can be included on a light input face of an optical alignment element or container to reduce unwanted reflections and to improve optical throughout.

[0319] The face of a container through which an excitation light exits the container including photohardenable composition (which will typically be opposite the surface through which the excitation light enters the container) can further include an absorbing paint or an outcoupling optic to minimize or prohibit total internal reflection of the light sheet and / or projected image light.

[0320] With additional more complex fluidics it may be possible to move the part in z, for example, by moving the container, without moving the first optics, the second optics, and / or, if applicable, the optical alignment element(s).

[0321] When projecting an optical image, it is preferable to use a projection system that, in addition to second optics, also includes a projection device and can optionally further include one or more optical components and / or mechanisms for translating the position of any of the components of the optical image projection system.

[0322] Examples of projection devices that may be included in a projection system include, but are not limited to, a laser projection system, a liquid crystal display (also referred to herein as “LCD”), a spatial light modulator (also referred to herein as “SLM”) (for example, but not limited to, a digital micromirror device (also referred to herein as “DMD”)), a micro-LED array, a vertical cavity laser array (also referred to herein as “VCL”), a Vertical Cavity Surface Emitting Laser array (also referred to herein as “VCSEL”), a liquid crystal on silicon (also referred to herein as “LCoS”) projector, and a scanning laser system. (Light emitting diode is also referred to herein as “LED”). A light sheet is preferable generated with a light sheet generating system (also referred to herein as a light sheet generator). Light sheet generating systems and techniques are known. Examples of known line generators typically can include optics (e.g., Powell lens, diffractive optic, cylindrical lenses, other collimating optics, etc.) to form a beam in combination with one or more lenses (e.g., cylindrical lenses) and / or optionally one or more components or devices, e.g., scanner, including but not limited to polygon scanner, galvanometer scanner, MEMS scanner, piezo-electric scanner, acousto-optic scanner, a light guide plate (with a fiber light source if used), a spatial light modulator, including but not limited to digital micromirror device (DMD) and Liquid Crystal on Silicon (LCOS) panel that can convert generate a line-shaped beam which is projected across a planar slice of a volume or space creating a sheet of light along the second light path through the volume or space. A sheet of light can also be generated with an extended light source (e.g., a onedimensional array of lasers or LEDs) that can further include other optical components.

[0323] A light sheet generating system can further include additional components including, but not limited to, lenses, other optical components, turn mirrors, translational stages for moving the system and / or components thereof.

[0324] The methods disclosed herein can also include the use of commercially available projection and filtering techniques that can assist in providing a very narrow depth of focus or systems.

[0325] A projection system or light sheet generating systems for use with the present invention can be selected to apply continuous excitation light. Such systems can be selected to apply intermittent excitation light. Intermittent excitation can include random on and off application of light or periodic application of light. Examples of periodic application of light includes pulsing. An optical image projection system and / or light sheet generating systems can be selected to apply a combination of both continuous excitation light and intermittent light, including, for example, an irradiation step that includes the application of intermittent excitation light that is preceded or followed by irradiation with continuous light.

[0326] A projection system comprising a spatial light modulator may be utilized with incoherent light as an amplitude modulator in combination with projection lens to form images in the photohardenable composition for amplitude base projections .

[0327] Optionally, an optical image projection system comprising a spatial light modulator may be utilized or as a wavefront encoding device to form a phase or complex amplitude modulation on the wavefront in a holographic configuration.

[0328] A light sheet is typically generated with excitation light from a light source in optical communication with first optics for directing the path of the light sheet. An optical image projection is typically generated with excitation light from a light source in optical communication with second optics.

[0329] Examples of light sources of the excitation light for use in the methods described herein include lasers, laser diodes, light emitting diodes, light-emitting diodes (LEDs), micro-LED arrays, vertical cavity lasers (VCLs), vertical cavity surface emitting lasers (VCSELs), and filtered lamps. Such light sources are commercially available and selection of a suitable light source can be readily made by one of ordinary skill in the relevant art. Light sources comprising a laser can be preferred.

[0330] Excitation light can have a wavelength in the visible or invisible spectral range.

[0331] In methods and systems in accordance with the present invention, the selection of wavelength(s) of the excitation light for the light sheet and optical image is preferably made taking into account the photohardenable composition and hardening mechanism being used.

[0332] The excitation light used to generate an optical projection is preferably selected to include light at a selected wavelength or in a selected range of wavelengths.

[0333] For example, for photohardenable compositions that are hardenable via a hardening mechanism that involves a single wavelength or range of wavelengths of excitation light, the wavelength of the excitation light projection(s) can be the same. Optionally in such case, an excitation light projection including a different wavelength or range of wavelengths of light can also be included, for example for inhibiting undesired hardening of the photohardenable composition.

[0334] In cases where a photohardenable composition is hardenable via a hardening mechanism that involves more than one wavelength or range of wavelengths of excitation light, the wavelengths or ranges of wavelengths of the excitation light projections will be selected for projecting excitation light with appropriate wavelengths for the hardening mechanism. Optionally a third wavelength or range of wavelengths of light can also be used to inhibit undesired hardening of the photohardenable composition.

[0335] Taking into account the photohardenable composition and hardening mechanism being used, the wavelength of excitation light of the light sheet and optical image may be the same or different.

[0336] A light source can be coherent or incoherent. An incoherent light source can be preferred. An incoherent light source is simpler to use and avoids having to address considerations such as, for example, phase and interference considerations, which can arise with use of a coherent light source.

[0337] Optionally, the excitation light can be temporally and / or spatially modulated. Optionally, the intensity of the excitation light can be modulated. Optionally, source drive modulation can be used, for example, to adjust the absolute power of the light beam. Spatially modulated excitation light can be created by known spatial modulation techniques, including, for example, a liquid crystal on silicon device, and a digital micromirror device. Other known spatial modulation techniques can be readily identified by those of ordinary skill in the relevant art.

[0338] Methods and systems described herein include a photohardenable composition.

[0339] The present invention can be useful in 3D printing objects including light sheet excitation in a volume of a photohardenable composition that can include the use of upconverting materials, triplet-triplet annihilation (TTA), photo-switches, dual-wavelength photoinitiators and any anticipated combinations thereof.

[0340] A photohardenable composition can include a photopolymerizable component.

[0341] A photohardenable composition can further include a photoinitiator (PI) that initiates hardening (e.g., by cross-linking or photopolymerization) of the photopolymerizable component upon excitation by light. Optionally, the photohardenable composition can include a combination of components or additives.

[0342] A photoinitiator can be readily selected by one of ordinary skill in the art, considering its suitability for the mechanism to be used to initiate polymerization as well as its suitability for and / or compatibility with the resin or photopolymerizable component to be polymerized. Other considerations in selecting a photoinitiator include the light absorption characteristics of the photoinitiator and the wavelength(s) of the excitation light to be used. Examples include, without limitation, dual-wavelength photoinitiators, photoswitchable photoinitiators. Other examples of photoinitiators include photoinitiator systems comprising at least one of a compound having a high bond breaking energy, a compounds having a photolabile protecting group, an in situ generated initiator, a quencher, or a pH-sensitive photo initiator.

[0343] A photohardenable composition can further include one or more other additives depending upon the desired end use. Examples of typical additives include, but are not limited to, a thixotrope / rheology modifier, a defoamer, a stabilizer, an oxygen scavenger, and a non-reactive solvent diluent. Any additive can be a single additive or a mixture of additives. For example, a thixotrope can comprise a single thixotrope or a mixture of two or more thixotropes. Additives are preferably selected so that they do not react with the photohardenable component or any photoinitiator or other additive that may be included in photohardenable compositions. A photohardenable composition can optionally include one or more coinitiators and / or sensitizers.

[0344] Examples of photohardenable components useful in a photohardenable composition include ethylenically unsaturated compounds and, more specifically, a polyethylenically unsaturated compounds. These compounds include both monomers having one or more ethylenically unsaturated groups, such as vinyl or allyl groups, and polymers having terminal or pendant ethylenic unsaturation. Such compounds are well known in the art and include acrylic and methacrylic esters of polyhydric alcohols such as trimethylolpropane, pentaerythritol, and the like; and acrylate or methacrylate terminated epoxy resins, acrylate or methacrylate terminated polyesters, etc. Representative examples include ethylene glycol diacrylate, ethylene glycol dimethacrylate, trimethylolpropane triacrylate (TMPTA), pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, dipentaerythritol hydroxypentacrylate (DPHPA), hexanediol- 1,6-dimethacrylate, and diethyleneglycol dimethacrylate. Preferred examples include, but are not limited to, a urethane acrylate or a urethane methacrylate.

[0345] Preferred photoinitiators comprise a photoswitchable photoinitiator which converts from an inactive (non-initiating) form via excitation light of a first wavelength into an active (initiating) form, wherein simultaneous or subsequent (preferably closely timed sequential exposure) excitation light of a second wavelength absorbed by the active form induces hardening of the photohardenable composition (e.g., via a crosslinking or photopolymerization reaction in the photohardenable component), wherein the first and second wavelengths are different.

[0346] Information concerning photohardenable compositions, photoswitchable photoinitiators, and printing that may be useful in connection with the present invention includes International Application No. PCT / US2022 / 037491, filed July 18, 2022, of Quadratic 3D, Inc., International Application No. PCT / US2022 / 042179, filed August 31, 2022, of Quadratic 3D, Inc., International Application No. PCT / US2022 / 042183, filed August 31, 2022, of Quadratic 3D, Inc., International Application No. PCT / US2022 / 042186, filed August 31, 2022, of Quadratic 3D, Inc., International Application No. PCT / US2023 / 022170 of Quadratic 3D, Inc. filed May 13, 2023, International Application No. PCT / US2023 / 022171 of Quadratic 3D, Inc. filed May 13, 2023, International Application No. PCT / US2023 / 022172 of Quadratic 3D, Inc. filed May 13, 2023, and International Application No. PCT / US2023 / 022173 of Quadratic 3D, Inc. filed May 13, 2023, each of the foregoing applications being hereby incorporated herein by reference in its entirety.

[0347] Examples of preferred photoswitchable photoinitiators for use in connection with the present invention include substituted or unsubstituted P-type photochromic molecules. Examples of such preferred photoinitiators include, but are not limited to, substituted or unsubstituted diarylethene molecules. See, for example, International Application No. PCT / US2023 / 022172 of Quadratic 3D, Inc. filed May 13, 2023.

[0348] Examples of compositional ranges for a photoswitchable photoinitiator or other dual wavelength photoinitiator in a photohardenable composition include, but are not limited to, about 0.0001 to about 0.5, including, for example, but not limited to, e.g., about 0.0001 to about 0.1, about 0.0001 to about 0.05, about 0.0001 to about 0.01, about 0.0001 to about 0.009, about 0.0001 to about 0.005, from about 0.0001 to about 0.0025, etc.

[0349] Examples of photoswitchable photoinitiators useful in photohardenable compositions can absorb at about 300 to 450 nm. Depending upon the absorption spectrum for the particular photoswitchable photoinitiator, the conversion to the second form can be induced by exposure to any source which emits in this range, e.g., lasers, light emitting diodes, mercury lamps. Filters may be used to limit the output wavelengths. A non-limiting example of filtered light includes filtered emission from a mercury arc lamp, etc. The second form of the photoswitchable photoinitiator will preferably absorb in a range of about 450 to 1000 nm and 450 to 850 most typically.

[0350] As provided herein, a photohardenable composition in accordance with certain aspects of the present invention includes one or more coinitiators and / or sensitizers and in other aspects of the present invention can optionally include one or more coinitiators and / or sensitizers.

[0351] Examples of coinitiators that may be useful can be selected from among those known in the art and, more particularly, tertiary amines and organoborate salts. lodonium salts may also be useful, particularly in combination with a borate salt. In certain embodiments, an iodonium salt may also be included in combination with a tertiary amine. Examples of other useful electron donating coinitiators are discussed by Eaton, D. F., "Dye Sensitized Photopolymerization", Advances in Photochemistry, Vol. 13, pp 427-486.

[0352] In the methods and systems described herein, preferably the photohardenable composition included in the container displays non-Newtonian rheological behavior. Non-Newtonian rheological behavior can facilitate forming an object in the volume without support structures and with minimal displaced of the object in the volume of the photohardenable composition during formation. NonNewtonian behavior of the photohardenable composition can additionally simplify separation of the object from the volume of the photohardenable composition in which it is formed or printed. Examples of non-Newtonian rheological behavior include but are not limited to pseudoplastic fluid, yield pseudoplastic, Bingham plastic, or Bingham pseudoplastic.

[0353] The methods, systems, and print modules described herein can be used in combination with a computer and software. For example, light sheet generating systems, optical image projection systems and projection devices that may be included therein, that can be included in the methods and systems described herein may be used in combination with a computer and software. Software can be used to coordinate generation of optical projections (e.g., point illuminations, line illuminations, a two-dimensional pattern, or a light sheet) from their respective optical image projection system or projection devices at each position along the projection direction of each so that the part is developed plane by plane. The planar face of an optical projection can be orthogonal to its projection direction into photohardenable composition. When two optical projections are projected into the volume of the photohardenable composition, the projection directions of the two projections are preferably orthogonal to each other. Selection of computer controls and software is within the skill of the person of ordinary skill in the relevant art. Other components can also optionally be included or used with the system.

[0354] Methods and systems in accordance with the present invention advantageously further do not require adhering the object being printed to a fixed substrate (e.g., build plate) at the beginning of the printing process avoiding a post-processing step of separating the printed object from the fixed substrate.

[0355] Methods and systems described herein are particularly useful for forming or “printing” three-dimensional objects.

[0356] Preferably the at least two optical projections do not overlap or intersect except at one or more selected locations in the volume of the photohardenable composition where local polymerization is desired.

[0357] Most preferably polymerization occurs only when two optical projections overlap or intersect at one or more locations or voxels where local polymerization is desired in the volume of the photohardenable composition.

[0358] Preferably a single optical projection is insufficient to cause polymerization of the photohardenable composition.

[0359] Power densities or intensities of excitation light directed into the volume of photohardenable composition to cause polymerization to occur may be, without limitation, less than 1000 W / cm2, less than 500 W / cm2, less than 100 W / cm2, less than 50 W / cm2, less than 10 W / cm2, less than 5 W / cm2, less than 1 W / cm2, less than 500 mW / cm2, less than 100 mW / cm2, etc.

[0360] In the methods and systems of the present invention, the volume of a photohardenable composition is preferably included within a container wherein at least a portion of the container is optically transparent so that the photohardenable composition is accessible by excitation light. Preferably, the entire container is optically transparent. Optically transparent portions of a container can be constructed from a material comprising, for example, but not limited to, glass, quartz, fluoropolymers (e.g., Teflon FEP, Teflon AF, Teflon PFA), cyclic olefin copolymers, polymethyl methacrylate (PMMA), polynorbornene, sapphire, or transparent ceramic. It can be desirable for the entire container to be optically transparent. Preferably the optically transparent portion(s) of the container is (are) also optically flat.

[0361] Examples of container shapes that can be included in methods and systems of the present invention include, but are not limited to, a cylindrical container having a circular or oval cross- section, a container having straight sides with a polygonal cross-section or a rectangular or square cross-section.

[0362] In methods and systems described herein, it can be preferred for surface(s) of the container at the entry points for the first and second excitation lights to be planar.

[0363] In methods and systems described herein, it can be preferred for surface(s) of the container at the entry points for the first and second excitation lights to be optically transparent.

[0364] In methods and systems described herein, it can be preferred for an optical alignment element and at least the selected region of the wall or surface of the container to have the same index of refraction as the photohardenable composition.

[0365] In methods and systems described herein, preferably there is no air gap between the photohardenable composition and the inner surface of the container through which an excitation lights (whether in a light sheet, optical image, or other configuration) is directed into the volume to minimize or eliminate total internal reflection (TIR).

[0366] In methods and systems described herein, a container can optionally include one or more coatings or surface treatments to reduce back reflections of any of the excitation lights used for the method into the printing resin during printing, which can significantly impact printing accuracy. Examples of such coatings or surface treatments include, but are not limited to, one or more anti- reflective (AR) or absorptive coatings on, for example, a light exit window of the container.

[0367] As discussed above, other examples of an optical alignment element can comprise an arrangement and / or combination including one or more facets, optical gratings, and / or other optical features that can be included in or at a surface of the container and through which excitation light (e.g., configured as a light sheet, optical image, or other configuration) enters the container. Such arrangements and / or combinations can improve control of the angle at which the first and second light paths intersect in the volume.

[0368] Preferably the intersection angle should be 90 degrees or substantially close to 90 degrees, with or without facets. Inclusion of facets can facilitate control of the angle of the projector and light sheet generator with respect to the container. For example, with inclusion of facets, the incidence angles are lower, which can have advantages for mechanical mounting.

[0369] Optionally, one or more filters are added to at least a surface of any optically transparent portions of the container to block undesired light, e.g., with a wavelength the same as the upconverted light (e.g., light with the second wavelength), to prevent unintentional curing.

[0370] Optionally, depending upon the oxygen sensitivity of the photohardenable composition being used, the photohardenable composition can be degassed, purged or sparged with an inert gas before or after being introduced into the container and is maintained under inert conditions, e.g., under an inert atmosphere, while in the container which is preferably closed during printing. This can prevent introduction of oxygen into the container while the three-dimensional object is being printed or formed. Preferably the container is sealed or otherwise closed in an air-tight manner to prevent introduction of oxygen into the container during printing. The seal or other closing techniques that may be used should not be permanent so at least that the printed objects and unpolymerized material can be removed from the container.

[0371] In certain instances, depending, for example, upon the materials used, the photohardenable composition is preferably substantially oxygen free (e.g., less than 50 ppm oxygen) during printing.

[0372] In the methods described herein, it may be desirable to rotate the container to provide additional angles of illumination or projection of excitation light into the volume of photohardenable composition contained therein. This can be of assistance in patterning object volumes or surfaces more accurately or it can be used as a means of providing multiple exposure of a given feature from different angles.

[0373] In the method described herein, the container may be stationary while an optical projection of excitation light is being directed into the photohardenable composition.

[0374] In the systems described herein, it may be desirable for the position of container be changeable, e.g., rotated, translated, etc., or held stationary.

[0375] Before printing, a digital file of the object to be printed is typically obtained. If the digital file is not of a format that can be used to print the object, the digital file is then converted to a format that can be used to print the object. An example of a typical format that can be used for printing includes, but is not limited to, an STL file. Typically, the STL file is then sliced into two- dimensional layers along the direction in which it will be projected into the photohardenable composition with use of three-dimensional slicer software and converted into G-Code or a set of machine commands, which facilitates building the object. See B. Redwood, et al., “The 3D Printing Handbook - Technologies, designs applications”, 3D HUBS B.V. 2018. In the methods, systems, and print modules described herein, a three-dimensional digital file of the object to be printed or formed is preferably decomposed into a series of sequential two-dimensional slices of the object for printing, which slices are preferably based on the angle of the light path for the light sheet and the angle of the light path for the optical image at the first position in the resin or photohardenable composition at which the light sheet and optical image intersect, more preferably in a common plane.

[0376] Other information concerning optical systems that may useful in connection with the various aspects of the present inventions includes Texas Instruments Application Report DLPA022- July 2010 entitled “DLP™ System Optics”; Texas Instruments “TI DLRTechnology for 3D Printing - Design scalable high-speed stereolithograpy [sic] systems using TI DLP technology” 2016; Texas Instruments “DLP6500 0.65 1018p MVSP Type A DMD”, DLP6500, DLPS040A-October 2014 - Revised October 2016; and Y-H Lee, et al., “Fabrication of Periodic 3D Nanostructuration for Optical Surfaces by Holographic Two-Photon-Polymerization”, IntT Journal of Information and Electronics Engineering, Vol 6, No. 3, May 2016, each of the foregoing being hereby incorporated herein by reference in its entirety.

[0377] Additional information that may be useful in connection with the present invention include International Publication No. 2021 / 247926 Al of Quadratic 3D, Inc., for "Volumetric Three Dimensional Printing Methods", filed June 3, 2021; International Publication No. WO 2021 / 247930 Al of Quadratic 3D, Inc., for "Volumetric Three Dimensional Printing Methods Including a Light Sheet And Systems", filed June 3, 2021; International Publication No. WO 2021 / 154897 Al of Quadratic 3D, Inc. filed January 27, 2021 for "Photohardenable Compositions Including An Upconverting Component And Methods"; International Application No. PCT / US2022 / 039766 of Quadratic 3D, Inc. for “Methods And Systems For Forming An Object In A Volume Of A Photohardenable Composition”, filed August 9, 2022, and International Application No. PCT / US2022 / 052157, filed December 7, 2022, of Quadratic 3D, Inc., each of the foregoing being hereby incorporated herein by reference in its entirety for all purposes.

[0378] When used as a characteristic of a portion of a container or build chamber, “optically transparent” refers to having high optical transmission to the wavelength of light being used, and “optically flat” refers to being non-distorting (e.g., optical wavefronts entering the portion of the container or build chamber remain largely unaffected).

[0379] As used herein, the singular forms "a", "an" and "the" include plural unless the context clearly dictates otherwise. Thus, for example, reference to an emissive material includes reference to one or more of such materials.

[0380] The present invention may be embodied in various forms. For convenience, the terms "upper" and "lower" and “top” and “bottom” are used herein to differentiate between the upper and lower ends of the components described herein. The terms "inner" and "outer" are used herein to differentiate between the inner and outer portions of the components described herein. It is to be appreciated that "upper" and "lower", and “top” and “bottom”, and “inner” and “outer” are used only for ease of description and understanding and that they are not intended to limit the possible spatial orientations of the components described herein during assembly or use.

[0381] As used herein, the term “substantially” is meant to mean mostly, or almost the same as, within the constraints of sensible commercial engineering objectives, costs, manufacturing tolerances, and capabilities in the field of volumetric 3D printing assembly manufacturing and use. Similarly, the term “approximately” as used herein is meant to mean close to, or about a particular value, within the constraints of sensible commercial engineering objectives, costs, manufacturing tolerances, and capabilities in the field of volumetric 3D printing assembly manufacturing and use.

[0382] Applicant specifically incorporates the entire contents of all cited references in this disclosure. Further, when an amount, concentration, or other value or parameter is given as either a range, preferred range, or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is not intended that the scope of the invention be limited to the specific values recited when defining a range.

[0383] Other embodiments of the present invention will be apparent to those skilled in the art from consideration of the present specification and practice of the present invention disclosed herein. It is intended that the present specification and examples be considered as exemplary only with a true scope and spirit of the invention being indicated by the following claims and equivalents thereof.

Claims

CLAIMS1. A method of forming an object in a volume of a photohardenable composition, the method comprising: a. providing a container containing the volume of the photohardenable composition; b. directing a first excitation light along a first light path into the container to a first position in the photohardenable composition and directing a second excitation light along a second light path into the container to the first position in the photohardenable composition such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the first and second excitation lights, wherein at least one of the excitation lights is directed through an optical alignment element before entering the container, and wherein the first position is located at a selected location in the volume of the photohardenable composition; and c. optionally repeating step b. until the object is partially or fully formed, wherein, for a repeated step, the optical image is the same as or different from a previous optical image and the container is positioned such that the selected location in a repeated step is the same as or different from a previous selected location.

2. A method of forming an object in a volume of a photohardenable composition, the method comprising: a. providing a container containing the volume of the photohardenable composition; b. directing a light sheet including first excitation light along a first light path into the container to a first position in the photohardenable composition and directing an optical image including a second excitation light into the container to the first position in the photohardenable composition such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the light sheet and optical image, wherein the light sheet and / or the optical image passes through an optical alignment element before entering the container, and wherein the first position is located at a selected location in the volume of the photohardenable composition; and c. optionally repeating step b. until the object is partially or fully formed, wherein, for a repeated step, the optical image is the same as or different from a previous optical image and the container is positioned such that the selected location in a repeated step is the same as or different from a previous selected location.

3. A method of forming an object in a volume of a photohardenable composition, the method comprising: a. providing a container containing the volume of the photohardenable composition,b. directing a light sheet including first excitation light along a first light path through a first optical alignment element into the container containing the volume of the photohardenable composition and projecting an optical image including a second excitation light along a second light path through an optical alignment element into the container containing the volume of the photohardenable composition, wherein the first light path and the second light path are oriented for the light sheet and optical image to intersect at a first position and the container is positioned relative to the first position to locate the intersection of the light sheet and the projected image at a selected location in the photohardenable composition to at least partially harden the photohardenable composition at the selected location as a result of exposure to the light sheet and optical image, and wherein the optical alignment element through which the optical image is directed is the first optical alignment element or a second optical alignment element; and c. optionally repeating step b. until the object is partially or fully formed, wherein, for a repeated step, the optical image is the same as or different from a previous optical image and the container is positioned such that the intersection of the light sheet and projected image in a repeated step is located at a location in the volume that is the same as or different from a previous selected location.

4. The method of claim 1 wherein both of the first and second excitation lights are directed through a single optical alignment element.

5. The method of claim 1 wherein each of the first and second excitation lights is directed through a separate optical alignment element.

6. The method of claim 2 wherein both of the light sheet and the optical image are directed through a single optical alignment element.

7. The method of claim 2 wherein each of the light sheet and the optical image is directed through a separate optical alignment element.

8. The method of claim 3 wherein the optical image is directed through the first optical alignment element.

9. The method of claim 3 wherein the optical image is directed through the second optical alignment element.

10. The method of claim 2 or 3 wherein the optical image is perpendicular to the second light path.

11. The method of any one of claims 1 , 2, and 3 wherein the first excitation light includes a first wavelength and the second excitation light includes a second wavelength.

12. The method of claim 2 or 3 wherein the optical image comprises a two-dimensional optical image.

13. The method of claim 12 wherein the two-dimensional optical image corresponds to a two- dimensional slice of the object.

14. The method of claim 13 wherein the optical image of a repeated step includes a next sequential two-dimensional slice of the object.

15. The method of any one of claims 1, 2, and 3 wherein the first light path and second light path overlap or intersect at an angle less than 90 degrees.

16. The method of any one of claims 1, 2, and 3 wherein the first light path and second light path overlap or intersect at a right angle.

17. The method of any one of claims 1, 2, and 3 wherein the first and second excitation lights overlap or intersect at the first position in a common plane.

18. The method of any one of claims 1, 2, and 3 wherein a repeated step includes moving the container relative to the first position to change the position of the selected location in the photohardenable composition.

19. The method of 13 wherein the first wavelength is in a range from about 350 to about 460 nm and the second wavelength is in a range from about 450 nm to about 850 nm.

20. The method of claim 1 or 2 wherein the first light path enters a light input surface of an optical alignment element at a 90 degree angle.

21. The method of claim 3 wherein the first light path enters a light input surface of the first optical alignment element at a 90 degree angle.

22. The method of claim 1 or 2 wherein the second light path enters a light input surface of an optical alignment element at a 90 degree angle.

23. The method of claim 3 wherein the second light path enters a light input surface of the optical alignment element at a 90 degree angle.

24. The method of claim 11 wherein the first and second wavelengths are not the same.

25. The method of claim 11 wherein the first and second wavelength lights are the same.

26. The method of any one of claims 1 , 2, and 3 wherein the photohardenable composition includes a photohardenable component and a photoinitiator.

27. The method of claim 26 wherein the photohardenable composition further includes an upconverting component.

28. The method of claim 26 wherein the photoinitiator comprises a photoswitchable photoinitiator.

29. The method of claim 28 wherein the photohardenable composition further includes one or more coinitiators.

30. The method of claim 28 wherein photohardenable composition further comprises one or more additives.

31. The method of claim 26 wherein the photoinitiator comprises a dual-wavelength photoinitiator.

32. The method of claim 31 wherein photohardenable composition further comprises one or more additives.

33. The method of any one of claims 1, 2, and 3 further including post-processing the object.

34. The method of any one of claims 1, 2, and 3 wherein one or more objects are formed in the container.

35. The method of claim 2 or 3 wherein a spatial light modulator is included in generation of the optical image.

36. The method of any one of claims 1, 2, and 3 wherein a light output surface of each optical alignment element included in the system is in direct contact with a surface of the container through which the first and / or second excitation lights enter the container.

37. The method of claims 36 wherein the surface of the container through which the first and second excitation lights enter the container and the light output surface of each optical alignment element are index-matched.

38. The method of any one of claims 1, 2, and 3 wherein a light output surface of each optical alignment element included in the system is optically coupled to a surface of the container through which the first and / or second excitation lights enter the container.

39. The method of claim 38 wherein the surface of the container through which the first and second excitation lights enter the container is optically coupled to the light output surface of each optical alignment element via an index-matching material.

40. The method of any one of claims 1 , 2, and 3 wherein there is substantially no airgap between the photohardenable composition and an internal surface of a side of the container through which the first and second excitation lights enter the container.

41. The method of any one of claims 1, 2, and 3 wherein a surface of the container through which the first and second excitation lights enter the container includes one or more optically transparent regions to facilitate passage of the first and second excitation lights therethrough.

42. The method of claim 34 wherein the object is suspended in the volume during formation.

43. The method of any one of claims 1, 2, and 3 wherein the container is moved within a two- dimensional plane parallel to the surface of the container through which the first and second excitation lights enter the container to change the position of the first position for a repeated step.

44. The method of any one of claims 1 , 2, and 3 wherein at least one of the excitation lights is generated by a light source comprising a laser.

45. The method of any one of claims 1, 2, and 3 wherein each of the first and second excitation lights is generated by a light source comprising a laser.

46. The method of claim 1 or 2 wherein an optical alignment element comprises a right angle prism.

47. The method of claim 1 or 2 wherein an optical alignment element comprises a dove prism.

48. The method of claim 3 wherein the first optical alignment element comprises a right triangular prism.

49. The method of claim 3 wherein the second optical alignment element comprises a right triangular prism.

50. The method of any one of claims 1-3 wherein each optical alignment element comprises a right angle prism.

51. The method of any one of claims 1-3 wherein each optical alignment element comprises a dove prism.

52. The method of any one of claims 1 , 2, and 3 further comprising providing a digital representation of the object that has been sliced into a plurality of sequential two-dimensional image slices along a selected axial direction and wherein the second excitation light comprises one of the plurality of the sequential two-dimensional slices.

53. The method of any one of claim 1, 2, and 3 further comprising removing the object from the container.

54. The method of claim 53 wherein the method further includes washing the removed object to remove non-hardened photohardenable composition from the object using solvent.

55. The method of claim 53 further including post-curing the object in fluid or air to complete hardening.

56. The method of claim 55 wherein post-curing comprises UV curing.

57. The method of claim 55 wherein post-curing comprises thermal curing.

58. The method of any one of claims 1, 2, and 3 wherein the first position is fixed for a given z- depth.

59. The method of any one of claims 1, 2, and 3 wherein each light path enters an input surface of the optical alignment element through which it is directed at a selected angle.

60. The method of claim 1 further including directing a third excitation light along a third light path into the container to the first position in the photohardenable composition such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the first, second, and third excitation lights, wherein at least one of the first, second, or third excitation lights is directed through an optical alignment element before entering the container, and wherein the first position is located at a selected location in the volume of the photohardenable composition.

61. The method of claim 2 or 3 further including directing a second light sheet or a reflection of the light sheet passing through the container along a third light path into the container to the first position in the photohardenable composition such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the light sheet, the optical image, and the second or reflected light sheet, wherein at least one of the light sheet, the optical image, or the second or reflected light sheet is optionally directed through an optical alignment element before entering the container, and wherein the first position is located at a selected location in the volume of the photohardenable composition.

62. A system for forming an object in a volume of a photohardenable composition, the system comprising: a combination including: a. a first optical system for generating first excitation light, the first optical system including first optics for directing the generated first excitation light along a first light path to a first position in a container for containing the volume of the photohardenable composition; b. a second optical system for generating second excitation light, the second optical system including second optics for directing the generated second excitation light along a second light path to the first position in a container for including the volume of a photohardenable composition; and c. at least one optical alignment element, the optical alignment element being configured or configurable such that at least one of the generated excitation lights passes through an optical alignment element before passing into the container, wherein the two light paths areconfigured or configurable such that the first and second light paths intersect at the first position in the container.

63. A system for forming an object in a volume of a photohardenable composition, the system comprising: a combination including: a. a first optical system comprising a light sheet generating system for generating a light sheet from a first excitation light, the light generating system including first optics for directing the generated light sheet along a first light path to a first position in a container for containing the volume of the photohardenable composition; b. a second optical system comprising a projection system for projecting an optical image from a second excitation light, the projection system including second optics for directing the generated optical image along a second light path to the first position in the container, wherein the first optics and second optics are fixed or movable relative to each other; and c. at least one optical alignment element, the optical alignment element being positioned or positionable such that the generated light sheet and / or the projected optical image passes through an optical alignment element before passing into the container, wherein the two light paths are configured or configurable such that the first and second light paths intersect at the first position in the container.

64. A system for forming an object in a volume of a photohardenable composition, the system comprising: a combination including: a. a first optical system comprising a light sheet generating system for generating a light sheet from a first excitation light, the light sheet generating system including first optics for directing the generated light sheet along a first light path to a first position in a container for containing the volume the photohardenable composition; b. a second optical system comprising a projection system for projecting an optical image from a second excitation light, the projection system including second optics for directing the generated optical image along a second light path to the first position in the container, wherein the first optics and second optics are fixed or movable relative to each other, c. an optical alignment element being positioned or positionable such that the first and second light paths pass through the optical alignment element into the container, wherein the first and second light paths are configured or configurable such that the first and second light paths intersect at the first position in the container.

65. A system for forming an object in a volume of a photohardenable composition, the system comprising a combination including: a. a first optical system comprising a light sheet generating system for generating a light sheet from a first excitation light, the light sheet generating system including first optics for directing the generated light sheet along a first light path to a first position in a container for containing the volume of the photohardenable composition; b. a second optical system comprising a projection system for projecting an optical image from a second excitation light, the projection system including second optics for directing the generated optical image along a second light path to the first position in the container, wherein the first optics and second optics are fixed or movable relative to each other; c. a first optical alignment element being positioned or positionable such that the first light path passes through the first optical alignment element into the container, and a second optical alignment element being positioned or positionable such that the second light path passes through the second optical alignment element into the container, wherein the first and second light paths are configured or configurable such that the first and second light paths intersect at the first position in the container.

66. The system of any one of claims 62-65 further including the container for containing the volume of the photohardenable composition.

67. The system of any one of claims 62-65 further comprising a translation mechanism for positioning the container relative to the first position.

68. The system of claim 62 further comprising a controller configured to selectively operate at least one, and preferably all, of generation and direction of the first and second excitation lights into the container.

69. The system of any one of claims 63- 65 further comprising a controller configured to selectively operate at least one, and preferably all, of generation and direction of the light sheet and optical image into the container.

70. The system of any one of claims 62-65 further comprising a first light source in optical communication with the first optical system.

71. The system of any one of claims 62-65 further comprising a second light source in optical communication with the second optical system.

72. The system of claim 70 further comprising a second light source in optical communication with the second optical system.

73. The system of any one of claims 63-65 wherein the optical image is perpendicular to the second light path.

74. The system of any one of claims 62-65 wherein the first optics and the second optics are fixed or movable with respect to each other.

75. The system of claim 67 wherein the translation mechanism includes a transparent region between the container and the light output surface of each optical alignment element from which an excitation light exits the optical alignment element.

76. The system of any one of claims 62-65 wherein the first optics and the second optics are positioned for the first and second excitation lights to overlap or intersect at the first position.

77. The system of claim 62-65 wherein a light output surface of each optical alignment element is in direct contact with the surface of the container through which the first and second excitation lights enter the container.

78. The system of claims 77 wherein the surface of the container through which the first and second excitation lights enter the container is index-matched with the light output surface of each optical alignment element.

79. The system of claim 62-65 wherein a light output surface of each optical alignment element is optically coupled to a surface of the container through which the first and second excitation lights enter the container.

80. The system of claims 79 wherein the surface of the container through which the first and second excitation lights enter the container is optically coupled to the light output surface of each optical alignment element via an index-matching material.

81. The system of any one of claims 62-65 wherein the surface of the container through which the light sheet and optical image enter the photohardenable composition includes one or more optically transparent regions to facilitate passage of the first and second excitation lights therethrough.

82. The system of claim 67 further including a controller for controlling the translation mechanism and position of the container moved thereby in one or more of the x, y, and z directions to change the selected location of the first position in the volume for partially or fully forming the object.

83. The system of claim 67 further comprising a controller configured to selectively operate at least one, and preferably all, of generation and direction of the first and second excitation lights into the container and controlling the translation mechanism and position of the container moved thereby.

84. The system of any one of claims 62-64 wherein an optical alignment element comprises a right angle prism.

85. The system of any one of claims 62-64 wherein an optical alignment element comprises a dove prism.

86. The system of claim 65 wherein one or both of the first optical alignment element and the second optical alignment element comprises a right angle prism.

87. The system of claim 65 wherein one or both of the first optical alignment element and the second optical alignment element comprises a dove prism.

88. The system of any one of claims 62-65 wherein each optical alignment element comprises a right angle prism.

89. The system of any one of claims 62-65 wherein each optical alignment element comprises a dove prism.

90. The system of claim 62 wherein the first optics are a remote component of the first optical system.

91. The system of claim 62 wherein the first optics are an integral component of the first optical system.

92. The system of any one of claims 63-65 wherein the first optics are a remote component of the light sheet generating system.

93. The system of any one of claims 63-65 wherein the first optics are an integrated component of the light sheet generating system.

94. The system of claim 62 wherein the second optics are a remote component of the second optical system.

95. The system of claim 62 wherein the second optics are an integral component of the second optical system.

96. The system of any one of claims 63-65 wherein the second optics are a remote component of the light sheet generating system.

97. The system of any one of claims 63-65 wherein the second optics are an integrated component of the light sheet generating system.

98. The system of any one of claims 63-65 wherein the projection system comprises a spatial light modulator for creating the optical image for projection by the second optics.

99. The system of any one of claims 62-65 further including a camera or detector system positioned for calibration purposes or to monitor the hardening of the photohardenable composition.

100. The system of any one of claims 62-65 wherein the photohardenable composition includes a photohardenable component and a photoinitiator.

101. The system of claim 100 wherein the photohardenable composition further includes an upconverting component.

102. The system of claim 100 wherein the photoinitiator comprises a photoswitchable photoinitiator.

103. The system of claim 100 wherein the photoinitiator comprises a dual- wavelength photoinitiator.

104. The system of claim 100 wherein photohardenable composition further comprises one or more additives.

105. The system of claim 102 wherein the photohardenable composition further includes one or more coinitiators.

106. The system of claim 105 wherein photohardenable composition further comprises one or more additives.

107. The system of claim 62 wherein both of the first and second excitation lights are oriented or orientable to pass through a single optical alignment element.

108. The system of claim 62 wherein each of the first and second excitation lights is oriented or orientable to pass through a separate optical alignment element.

109. The system of claim 63 wherein both of the light sheet and the optical image are oriented or orientable to pass through a single optical alignment element.

110. The system of claim 63 wherein each of the light sheet and the optical image is oriented or orientable to pass through a separate optical element.

111. The system of any one of claims 62-65 wherein a light path enters an input surface of an optical alignment element at a selected angle.

112. The system of claim 62 further comprising a third optical system for generating and directing a third excitation light along a third light path to the first position in the container for containing the volume of the photohardenable composition, the third optical system being positioned on a side of the container opposite the first optical system.

113. The system of claim 112 further including an additional optical alignment element that is positioned or positionable such that the third light path passes through the additional optical alignment element into the container.

114. The system of claim 112 wherein the first, second, and third light paths are configured or configurable to facilitate the three light paths intersecting at the first position in the container such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the first, second, and third excitation lights.

115. The system of any one of claims 63-65 further comprising a third optical system comprising a second light sheet generating system including third optics or reflection optics including third optics for reflecting the light sheet passing through the container back through the container, the third optical system being positioned on a side of the container opposite the first optical system for directing a second generated light sheet or directing the reflected light sheet along a third light path to the first position in the container.

116. The system of claim 115 further comprising an additional optical alignment element that is positioned or positionable such that the third light path passes through the additional optical alignment element into the container.

117. The system of claim 115 wherein the first, second, and third light paths are configures or configurable to facilitate the three light paths intersecting at the first position in the container such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the first light sheet, second light sheet, and optical image.

118. The system of any one of claims 62-65 wherein the first light path and second light path overlap or intersect at an angle less than 90 degrees.

119. The system of any one of claims 62-64 wherein the first light path enters a light input surface of an optical alignment element at 90 degree angle.

120. The system of claim 65 wherein the first light path enters a light input surface of the first optical alignment element at a 90 degree angle.

121. The system of any one of claims 62-64 wherein the second light path enters a light input surface of the optical alignment element at a 90 degree angle.

122. The system of claim 62-64 wherein the second light path enters a light input surface of the optical alignment element at a 90 degree angle.

123. The system of claim 65 wherein the second light path enters a light input surface of the second optical alignment element at a 90 degree angle.

124. A printhead module for use in forming an object in a volume of a photohardenable composition, the printhead module comprising: a combination including: a. first optics for directing first excitation light along a first light path to a first position in a container for containing the volume of the photohardenable composition and second optics for directing second excitation light along a second light path to the first position in the container; and b. at least one optical alignment element, the optical alignment element being positioned or positionable such that at least one of the excitation lights passes through an optical alignment element along its respective light path before passing into the container.

125. The printhead module of claim 124 wherein each of the first and second excitation lights are oriented to pass through the same optical alignment element.

126. The printhead module of claim 124 wherein each of the first and second excitation lights are oriented or orientable to pass through different optical alignment elements.

127. The printhead module of claim 124 wherein any light path passing through an optical alignment element enters the optical alignment element at a selected angle.

128. The printhead module of claim 124 wherein the first and second light paths are configured or configurable to facilitate the first and second light paths intersecting at the first position in the container such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the first and second excitation lights.

129. A printhead module for use in forming an object in a volume of a photohardenable composition, the printhead module comprising: a combination including: a. first optics for directing a generated light sheet along a first light path to a first position in a container for containing the volume of the photohardenable composition and second optics for directing a generated optical image along a second light path to the first position in the container; and b. at least one optical alignment element, the optical alignment element being positioned or positionable such that the generated light sheet and / or the generated optical image passes through an optical alignment element along its respective light path before passing into the container.

130. The printhead module of claim 129 wherein each of the generated light sheet and the generated optical image are oriented or orientable to pass through the same optical alignment element.

131. The printhead module of claim 129 wherein each of the generated light sheet and the generated optical image are oriented or orientable to pass through different optical alignment elements.

132. The printhead module of claim 129 wherein any light path passing through an optical alignment element enters the optical alignment element at a selected angle.

133. The printhead module of claim 129 wherein the first and second light paths are configured or configurable to facilitate the first and second light paths intersecting at the first position in the container such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the first and second excitation lights.

134. A printhead module for use in forming an object in a volume of a photohardenable composition, the printhead module comprising a combination including: a. first optics for directing a generated light sheet along a first light path to a first position in a container for containing the volume of the photohardenable composition and second optics for directing a generated optical image along a second light path to the first position in the container, and wherein the first optics and second optics are fixed or movable; and b. at least one optical alignment element being positioned or positionable such that the first and second light paths independently pass through an optical alignment element before passing into the container, wherein the first and second light paths are configured or configurable such that the first and second light paths intersect at the first position in the container.

135. The printhead module of claim 134 wherein the first light path enters a first input surface of the optical alignment element at a first selected angle and the second light path enters a second light input surface of the optical alignment element at a second selected angle.

136. The printhead module of claim 134 wherein the first and second light paths are configured or configurable to facilitate the first and second light paths intersecting at the first position in the container such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the first and second excitation lights.

137. A printhead module for use in forming an object in a volume of a photohardenable composition, the printhead module comprising a combination including: a. first optics for directing a generated light sheet along a first light path to a first position in a container for containing the volume of the photohardenable composition and secondoptics for directing a generated optical image along a second light path to the first position in the container, and wherein the first optics and second optics are fixed or movable; b. a first optical alignment element being positioned or positionable such that the first light path passes through the first optical alignment element before passing into the container, and a second optical alignment element being positioned or positionable such that the second light path passes through the second optical alignment element before passing into the container.

138. The printhead module of claim 137 wherein a light path passing through an optical alignment element enters the optical alignment element at a selected angle.

139. The printhead module of claim 137 wherein the first and second light paths are configured or configurable to facilitate the first and second light paths intersecting at the first position in the container such that a crosslinking or polymerization reaction is induced at the first position as a result of exposure by the first and second excitation lights.

140. The method of claim 1 or 2 wherein an optical alignment element comprises an arrangement and / or combination including one or more facets, optical gratings, and / or other optical features that can be included in or at a surface of the container through which excitation light enters the container.

141. The method of claim 3 wherein the first optical alignment element comprises an arrangement and / or combination including one or more facets, optical gratings, and / or other optical features that can be included in or at a surface of the container through which excitation light enters the container.

142. The method of claim 3 further including a second optical alignment element wherein at least one of the first or second optical alignment elements comprises an arrangement and / or combination including one or more facets, optical gratings, and / or other optical features that can be included in or at a surface of the container through which excitation light enters the container.

143. The system of any one of claims 62-64 wherein an optical alignment element comprises an arrangement and / or combination including one or more facets, optical gratings, and / or other optical features that can be included in or at a surface of the container through which excitation light enters the container.

144. The system of claim 65 wherein one or both of the first optical alignment element and the second optical alignment element comprises an arrangement and / or combination including one or more facets, optical gratings, and / or other optical features that can be included in or at a surface of the container through which excitation light enters the container.

145. The system of any one of claims 62-65 wherein each optical alignment element comprises an arrangement and / or combination including one or more facets, optical gratings, and / or other optical features that can be included in or at a surface of the container through which excitation light enters the container.

146. The system of any one of claims 62-64 wherein an optical alignment element comprises a right triangular prism.

147. The system of claim 65 wherein one or both of the first optical alignment element and the second optical alignment element comprises a right triangular prism.

148. The printhead module of any one of claims 124, 129, 134 and 137 wherein at least one optical alignment element comprises a right angle prism.

149. The printhead module of any one of claims 124, 129, 134 and 137 wherein at least one optical alignment element comprises a dove prism.

150. The printhead module of any one of claims 124, 129, 134 and 137 wherein at least one optical alignment element comprises a right triangular prism.

151. The printhead module of any one of claims 124, 129, 134 and 137 wherein at least one optical alignment element comprises an arrangement and / or combination including one or more facets, optical gratings, and / or other optical features that can be included in or at a surface of the container through which excitation light enters the container.

152. The method of claim 13 wherein the first light path is at a first angle at the first position and the second light path is at a second angle at the first position, and wherein the two-dimensional slice of the object is generated based on the first angle and second angle in the photohardenable composition at which the light sheet and optical image intersect.

153. The method of claim 14 wherein the first light path is at a first angle at the first position and the second light path is at a second angle at the first position, and wherein the next sequential two- dimensional slice of the object is generated based on the first angle and second angle in the photohardenable composition at which the light sheet and optical image intersect.

154. The method of claim 17 wherein the first light path is at a first angle at the first position and the second light path is at a second angle at the first position, and wherein the optical image comprises a selected two-dimensional slice of the object, wherein the two-dimensional slice of the object is based on the first angle and the second angle at the first position at which the light sheet and optical image overlap or intersect in the common plane.

155. The method of claim 13 wherein the two-dimensional optical image corresponds to a two- dimensional cross-section of the object.

156. The method of claim 13 wherein the optical image of a repeated step includes a next sequential two-dimensional cross-section of the object.

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