Methods and systems for forming an object by volumetric printing

Abstract

The present invention includes methods, systems, and printhead modules for forming an object in a volume of a photohardenable composition included in a container including directing a light sheet and an optical image to intersect at a first position in the photohardenable composition to alter at least one property or cause an initial patterning of the photohardenable composition at the intersection and subsequently directing a second light sheet to intersect the first position at a later time to cause further alteration of the previously altered or initially patterned intersection of the photohardenable composition, and optionally repeating these steps one or more times until the object is partially or fully formed.

Description

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

[0002] PRINTING

[0003] CROSS-REFERENCE TO RELATED APPLICATIONS

[0004] This application claims priority to U.S. Provisional Patent Application No. 63 / 639,280 filed on 26 April 2024 and U.S. Provisional Patent Application No. 63 / 717,125 filed on 06 November 2024, each of which application is hereby incorporated herein by reference in its entirety for all purposes.

[0005] TECHNICAL FIELD OF THE INVENTION

[0006] The present invention relates to the technical field of three-dimensional printing.

[0007] BRIEF SUMMARY OF THE INVENTION

[0008] The present invention includes methods, systems, and printhead modules for volumetric 3D printing of at least one three-dimensional object or printing onto an object. Methods, systems, and printhead modules in accordance with the present invention include exposing at least one selected location in a volume of the photohardenable composition to at least two intersecting first excitation lights (e.g., a first excitation light and a second excitation light) to alter at least one property of the photohardenable composition at the intersection thereof and subsequently exposing the altered photohardenable composition to at least one second excitation light (e.g., a third excitation light) to alter at least one property of the previously altered photohardenable composition.

[0009] In accordance with one aspect of the present invention, there is provided a method for forming at least one three dimensional object in a volume of a photohardenable composition, the method comprising: a. exposing a selected location in the volume of the photohardenable composition to at least two intersecting excitations lights to alter at least one property of the photohardenable composition at an occurrence of an intersection at a selected location creating an altered region of the photohardenable composition at the intersection, wherein the at least two intersecting excitation lights include at least one first excitation light and at least one second excitation light; b. subsequently exposing the altered region of the photohardenable composition to at least one third excitation light to further process an altered region; and c. optionally repeating steps a. and b. one or more times until the at least one object is partially or fully formed, wherein, for a repeated set of steps, the selected location in a repeated set of steps is the same as or different from a previous selected location and the altered region in a repeated step a. has a configuration that is the same as or different from that of a previous step a.

[0010] In accordance with another aspect of the present invention, there is provided a method of forming one or more three-dimensional objects in a volume of a photohardenable composition, the method comprising: a. providing a container containing the volume of the photohardenable composition; b. directing at least two excitations lights to a selected location in the volume to intersect at the selected location in the photohardenable composition to alter at least one property of the photohardenable composition at the intersection creating an altered region of the photohardenable composition , wherein the at least two excitation lights include at least one first excitation light comprising a light sheet including a first wavelength and at least one second excitation light comprising an optical image including a second wavelength; c. subsequently exposing the altered region of the photohardenable composition to at least one third excitation light to further change at least one property of the altered region to at least partially form a three-dimensional object, wherein at least one of the third excitation lights comprises a second light sheet including a third wavelength; and d. optionally repeating steps b. and c. one or more times until the at least one object is partially or fully formed, wherein, for a repeated set of steps, any selected location is the same as or different from a previous selected location and any optical image is the same as or different from a previous optical image.

[0011] Optionally, step b. can further include directing a third light sheet into the volume from a different side (e.g., opposite) side of the container from the first light sheet, the third light sheet being directed along a third light path that overlaps the first light path of the first light sheet such that the first and third light sheets are overlapping and both intersect with the optical image during the creation of the altered region of the photohardenable composition. Preferably the third light sheet includes the first wavelength. In the methods described herein including the alteration of at least one property of a photohardenable composition at the intersection of the first and second excitation lights, non-limiting examples of a property that can be altered include a change in inhibitor concentration or a change in the degree of polymerization, solidification, hardening, or other alteration of the photohardenable composition.

[0012] In the methods described herein, one or more altered regions or on or more initial patterns can be formed at an intersection of first and second excitation lights.

[0013] In accordance with another aspect of the present invention, there is provided a method of forming at least one object in a volume of a photohardenable composition, the method comprising: a. providing a container containing the volume of the photohardenable composition; b. directing two excitation lights to form an intersection at a first position in the container, wherein an initial patterning of at least a portion of an object in the photohardenable composition occurs at the intersection, wherein the initial patterning includes producing a first change in at least one property of the photohardenable composition, wherein the at least two excitation lights include a first excitation light and a second excitation light, wherein the first position is located at a selected location in the volume of the photohardenable composition; c. directing a third excitation light into the volume to overlap the initial patterning at the selected location in the volume at which the first and second excitation lights previously intersected, wherein the overlap by the third excitation light occurs at a later time than the initial patterning and produces a second change in the initially patterned photohardenable composition, and d. optionally repeating steps b. and c. one or more times until the at least one object is partially or fully formed, wherein, for a repeated set of steps, the initial patterning includes a configuration that is the same as or different from a previous initial pattern, and the container is positioned such that the selected location is the same as or different from a previous selected location. In accordance with another aspect of the present invention, there is provided a method of forming at least one 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 comprising a first light sheet including a first wavelength into the container along a first light path to a first position in the photohardenable composition and directing a second excitation light comprising an optical image including a second wavelength into the container to the first position, wherein the light sheet and optical image light form an intersection, wherein an initial patterning of at least a portion of an object in the photohardenable composition occurs at the intersection, wherein the initial patterning comprises producing a first change in at least one property of the photohardenable composition at the first position, wherein the first position is located at a selected location in the volume of the photohardenable composition; c. directing a third excitation light comprising a second light sheet including a third wavelength to the first position in the volume to overlap the initial pattern in the photohardenable composition, wherein exposure by the third excitation light occurs at a later time than the initial patterning and produces a second change in the initial pattern in the photohardenable composition; d. optionally repeating steps b. and c. until the at least one object is partially or fully formed, wherein, for a repeated set of steps, the optical image is the same as or different from a previous optical image and the container is positioned such that the selected location is the same as or different from a previous selected location.

[0014] Optionally, step b. can further include directing a third light sheet into the volume from a different side (e.g., opposite) side of the container from the first light sheet, the third light sheet being directed along a third light path that overlaps the first light path of the first light sheet such that the first and third light sheets are overlapping and both intersect the optical image during the initial patterning. Preferably the third light sheet includes the first wavelength. In the methods described herein, the light path of the at least one first excitation light including the first wavelength through the volume and the light path of the at least one third excitation light through the volume are oriented or orientable to be approximately parallel to each other when passing through the volume of the photohardenable composition.

[0015] In the methods described herein, a first excitation light does not intersect or overlap with a third excitation light within the volume of the photohardenable composition while either is turned on.

[0016] In the methods described herein, a second excitation light does not intersect or overlap with a third excitation light within the volume of the photohardenable composition while either is turned on.

[0017] Optionally a method in accordance with the present invention can further include passing any one or more of the excitation lights through an optical alignment element before entering the container including a volume of a photohardenable composition. In such case, when more than one excitation light passes through an optical alignment element, one or multiple optical alignment elements can be used with any single optical alignment element having one or more than one excitation lights passing through it before entering the container. An optical alignment element can affect the angles at which an excitation light enters the container including the photohardenable composition compared to the angles in the absence of the optical alignment element. Passing excitation lights that intersect in the volume of the photohardenable composition through the same or different optical alignment elements can also affect that angle at which they intersect in the volume of the photohardenable composition compared to the angles at which they would intersect in the absence of the optical alignment element.

[0018] In the methods described herein including an initial patterning that comprises producing a first change in at least one property of the photohardenable composition at the selected location, non-limiting examples of a first change in at least one property can include a change in inhibitor concentration or a change in the degree of polymerization, solidification, hardening, or other alteration of the photohardenable composition.

[0019] In accordance with another aspect of the present invention, there is provided a system for forming at least one three-dimensional object in a volume of a photohardenable composition, the system comprising: a combination including: a. a first optical system for generating at least one 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 at least one 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 the container for containing the volume of the photohardenable composition; 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; and c. a third optical system for generating at least one third excitation light, the third optical system including third optics for directing the generated third excitation light along a third excitation light path to the first position in the container, wherein the system is configured or configurable such that the third excitation light is directed to intersect with the first position after the intersection of the first and second excitation lights at the first position.

[0020] Preferably, the system is configured or configurable such that the third excitation light is not directed to the first position at the same time as the first and / or second excitation lights, but subsequent thereto. For example, the system can preferably be configured such that the third excitation light (excluding back reflections) is not directed to the first position during exposure of the first position to the first excitation light and / or the second excitation light but is directed to intersect with the first position following the exposure of the first position to the first and second excitation lights. More preferably the container and / or third optical system can alternatively or additionally be movable or translatable relative to each other such that he third excitation light can intersect with the first position after the intersection of the first and second excitation lights in the photohardenable composition.

[0021] 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 light sheet generating system for generating a first excitation light comprising a light sheet including a first wavelength, the light generating system including first optics for directing the generated light sheet along a first light path to a first position at a selected location in a container for containing the volume of the photohardenable composition; b. a projection system for projecting a second excitation light comprising an optical image including a second wavelength, 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 and second light paths are configured or configurable such that the first and second excitation light paths intersect at the first position in the container; and c. a second light sheet generating system for generating a third excitation light comprising a second light sheet including a third wavelength light, the second light sheet generating system including third optics for directing the second light sheet along a third excitation light path to intersect with the first position after the intersection of the first and second excitation lights at the first position.

[0022] More preferably the container and / or second light sheet generating system can alternatively or additionally be movable or translatable relative to each other such that he third excitation light can intersect with the first position after the intersection of the first and second excitation lights in the photohardenable composition.

[0023] Optionally, the system can further include a fourth optical system comprising a third light sheet generating system for generating and directing a third light sheet for into the volume from a different side (e.g., opposite) side of the container from the first light sheet, the third light sheet being directed along a third light sheet path that overlaps the first light path of the first light sheet such that the first and third light sheets are overlapping and both intersect the optical image during the initial patterning. Preferably the third light sheet includes the first wavelength.

[0024] Systems described herein can optionally further include a controller for operating or controlling one or more components and / or functions of the system.

[0025] In systems described herein, the first position can preferably be at a selected location in the volume of the photohardenable composition in the container. In systems described herein, the first optics and second optics can optionally be fixed or movable relative to each other.

[0026] Systems described herein can optionally further include a translation mechanism for use in changing the location or position of the container and / or the third optics or third optical system relative to each other for relocating the position of first position at which intersection of the first and second excitations occurred to a different position for intersection with the third excitation light path.

[0027] In a system in accordance with the present invention, the first optical system (which can comprise, for example, a first light sheet generating system) and the third optical systems (which can comprise, for example, a second light sheet generating system) are preferably configured or configurable such that the light path of the first excitation light through the volume and the light path of the third excitation light through the volume are oriented or orientable to be approximately parallel to each other when passing through the volume of the photohardenable composition.

[0028] In a system in accordance with the present invention, the first optical system (which can comprise, for example, a first light sheet generating system) and the third optical system (which can comprise, for example, a second light sheet generating system) are preferably configured or configurable such that the light path of the first excitation light and the light path for the third excitation light are oriented or orientable to be non-overlapping within the volume of the photohardenable composition.

[0029] In a system in accordance with the present invention, the second optical system (which can comprise, for example, a projection system for projection an optical image) and the third optical system (which can comprise, for example, a second light sheet generating system) are preferably configured or configurable such that the light path of the second excitation light and the light path for the third excitation light are oriented or orientable to be non-overlapping within the volume of the photohardenable composition.

[0030] Optionally a system in accordance with the present invention can further include one or more optical alignment elements through which one or more excitation lights can pass before entering the container. In such case, when more than one excitation light passes through an optical alignment element, one or multiple optical alignment elements can be used with any single optical alignment element having one or more than one excitation lights passing through it before entering the container. An optical alignment element can affect the angles at which an excitation light enters the container including the photohardenable composition compared to the angles in the absence of the optical alignment element. Passing excitation lights that intersect in the volume of the photohardenable composition through the same or different optical alignment elements can also affect that angle at which they intersect in the volume of the photohardenable composition compared to the angles at which they would intersect in the absence of the optical alignment element.

[0031] Optionally in systems and methods described herein, second excitation light (e.g., an optical image projection) is passed through an aperture positioned between the second optics (e.g., projection optics) or second optical system (e.g., a projection system) and the container. The aperture facilitates control of the excitation light directed into the container to the first position.

[0032] 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 first excitation light comprising a first light sheet including a first wavelength along a first light path to a first position in a container for including the volume including a photohardenable composition; b. second optics for directing a second excitation light comprising a second optical image including a second wavelength along a second light path to the first position in the container; wherein the first optics and second optics are configured or configurable to direct the first and second light paths to intersect at the first position; and c. third optics for directing a third excitation light comprising a second light sheet including a third wavelength along a third light path, the third optics being configured or configurable such that the third light path and first light path are substantially parallel to each other within the container.

[0033] Preferably the third light path for an illuminated second light sheet does not to cross or intersect with the first light path for an illuminated first light sheet and / or the second light paths for an illuminated optical image in the volume of photohardenable composition during printing. When used herein, unless otherwise indicated, a light path or excitation light path refers to the path traveled by light or excitation light from an optical system from which it is generated, projected, and / or directed, as the case may be, and / or optics positioned between the optical system and container through which the light or excitation light passes without regard, for example, to any back-reflections.

[0034] Methods, systems, and printhead modules described herein refer to the intersection of first and second excitation lights at a selected location or at a first position which is located at a selected location. In this regard, first position and selected location can refer to the same position or location.

[0035] The appended claims are hereby incorporated herein by reference in their entirety.

[0036] The foregoing, and other aspects and embodiments described herein and contemplated by this disclosure all constitute embodiments of the present invention.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In the drawings,

[0042] FIG. 1 depicts an example of a system and method of the present invention including a container 110 including a volume of a photohardenable composition, wherein a first excitation light comprising a first light sheet 112 is directed to a first position 116 at a selected location in the volume to intersect with a second excitation light comprising an optical image 114 that is directed to the first position 116. A third excitation light comprising a second light sheet 118 is directed into the container to overlap the first position 116 subsequent to (e.g., at a later point in time) the occurrence of the previous intersection of the first and second excitation lights to create a first change (e.g., an initial patterning) in the photohardenable composition. In the depicted example, the container can be moved to reposition the first position 116 at which the first and second excitation lights intersected to create a change in the photohardenable composition for being exposed to the third excitation light 118. In the configuration depicted in example, the light paths of the second excitation light (e.g., the optical image 114 ) and the third excitation light 118 (e.g., the second light sheet) as shown would intersect in the photohardenable composition if both excitation lights are illuminated at the same time. If both the second and third excitation lights are illuminated at the same time in this depicted configuration, unwanted interaction (e.g., polymerization) could occur where they intersect, which could cause changes in the volume at locations in the volume other than at the desired location at which the first change was created by the previous intersection of the first and second excitation lights at the first position. To prevent such unwanted interactions, in the orientation shown in this FIG. 1, it is preferred to not have both of the second and third excitation lights illuminated at the same time. For example, in this depicted configuration, the third excitation light is preferably not illuminated (e.g., turned off) while the second excitation light is illuminated for intersection with the first excitation light at the first position, and subsequent to the intersection, e.g., after a change or initial pattern is created in the photohardenable composition at the intersection at the first position, the second excitation light, and optionally also the first excitation light, are turned off before the third excitation light is illuminated and directed to the first position to overlap the first position at which the photohardenable composition was previously changed by the intersection of the first and second excitation lights. In an alternative configuration (not shown) in which that light paths of the first and third excitation lights would cross or otherwise intersect in the volume if both were illuminated, preferably the third excitation light would not be illuminated while the first and second excitation lights are illuminated and being directed into the volume to intersect and create a change in the photohardenable composition, and turned on after the first excitation light, and optionally also the second excitation light is turned off.

[0043] FIG. 2 depicts an example of a system and method of the present invention including a container 210 containing a volume of a photohardenable composition, wherein a first excitation light comprising a light sheet 212 including a first wavelength intersects with a second excitation light 214 comprising an optical image including a second wavelength at a first position 216. A third excitation light comprising a second light sheet 218 is directed into the container and overlaps the first position 216 subsequent to (e.g., at a later point in time) the occurrence of the previous intersection of the first and second excitation lights to create a first change (e.g., an initial patterning) in the photohardenable composition, which can optionally occur after the first position 216 is repositioned relative to the light path of the second light sheet 216 for the first position and second light sheet to intersect. In the depicted example, the first excitation light and second excitation light enter the container from the same face of the container and a third excitation light comprising a second light sheet including a third wavelength sheet is configured for the light path of the third excitation light to be directed into the container so as to not intersect the light paths of the first and second excitation lights in the volume while the first and second excitation lights intersect in the photohardenable composition. In the depicted example, the container and / or the optical systems can be moved to reposition the first position at which the first and second excitation lights intersected to create a change in the photohardenable composition for being exposed to the third excitation. In the depicted configuration, the third excitation light path does not intersect the light path of either the first excitation light (e.g., the first light sheet) or the second excitation light (e.g., the optical image) within the photohardenable composition. Since the lights paths of the first, second, and third excitation lights do not cross or intersect in the volume in the depicted example, the three excitation lights can be illuminated at the same time for a portion or all of the printing process. While FIG. 2 shows that the first excitation light 212 and the second excitation light 214 entering the container from the same face of the container, it is not necessary. For example, the light sheet and the projected image may enter from different, such as opposite, faces of the container. Likewise, the second light sheet and the light sheet or projected image need not enter the container from the same face of the container. For example, the second light sheet and the first light sheet may enter from different, such as opposite, faces of the container, or the second light sheet and the projected image may enter from different, such as opposite, faces of the container.

[0044] FIG. 3 depicts an example of a system and method of the present invention including a container 310 containing a volume of a photohardenable composition, wherein a first excitation light 312 comprising a first light sheet including a first wavelength intersects with a second excitation light comprising an optical image 314 including a second wavelength at a first position 316. A third excitation light comprising a second light sheet 318 is directed into the container and overlaps the first position subsequent to (e.g., at a later point in time) the occurrence of the previous intersection of the first and second excitation lights to create a first change (e.g., an initial patterning) in the photohardenable composition. In the depicted example, the first excitation light and second excitation light enter the container from the same face of the container and a third excitation light comprising a second light sheet 318 including a third wavelength sheet is configured for the light path of the third excitation light to be directed into the container so as to not intersect the light paths of the first and second excitation lights in the volume while the first and second excitation lights intersect in the photohardenable composition. The example shown in FIG. 3 further includes an optical alignment element 340 through which the first, second, and third excitation light pass before entering the container. The optical alignment element modifies the angle at which each excitation light enters the container of the photohardenable composition relative to the light path, projected image, and second light sheet in the absence of the optical alignment element. In this configuration, the second light sheet path does not intersect the projected image light path within the photohardenable composition, and therefore it may be turned on at the same time as the projected image for a portion or all of the printing process. While the figure shows that the first light sheet and the projected image enter the container from the same face of the container, it is not necessary. For example, the first light sheet and the optical image may enter from different, such as opposite or adjacent, faces of the container. Likewise, the second light sheet need not enter the container from the same face of the container as the first light sheet and / or the optical image. For example, the second light sheet and the first light sheet may enter from different, such as opposite, faces of the container, or the second light sheet and the optical image may enter from different, such as opposite, or adjacent faces of the container.

[0045] FIG. 4A depicts an exemplary optical lens fabricated using a method described herein.

[0046] FIG. 4B depicts a representative two-dimensional (2D) height map of the surface of a lens printed using the method described herein, where the surface mean roughness value (Sa) was measured to be on average 55 nanometers. FIG. 5 depicts an example of a system and method of the present invention including a container 510 containing a volume of a photohardenable composition, wherein a first excitation light comprising a light sheet 512 including a first wavelength intersects with a second excitation light 514 comprising an optical image including a second wavelength at a first position 516. A third excitation light comprising a second light sheet 518 is directed into the container and overlaps the first position 516 subsequent to (e.g., at a later point in time) the occurrence of the previous intersection of the first and second excitation lights to create a first change (e.g., an initial patterning) in the photohardenable composition (not shown).

[0047] 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.

[0048] For a better understanding of 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.

[0049] DETAILED DESCRIPTION OF THE INVENTION

[0050] Various aspects and embodiments of the present inventions will be further described in the following detailed description.

[0051] The present invention includes methods, systems, and printhead modules for volumetric 3D printing at least one three-dimensional object or printing onto an object. Methods, systems, and printhead modules in accordance with the present invention include exposing at least one selected location in a volume of the photohardenable composition to at least two intersecting first excitation lights (e.g., a first excitation light and a second excitation light) to alter at least one property of the photohardenable composition at the intersection thereof and subsequently exposing the altered photohardenable composition to at least one second excitation light (e.g., a third excitation light) to alter at least one property of the previously altered photohardenable composition.

[0052] The invention described herein includes methods, systems, and printhead modules that can be particularly advantageous for use in volumetric 3D printing including, for example, at least three excitation lights for forming at least one three-dimensional object in a volume of a photohardenable composition, wherein at least two of the at least three excitation lights intersect to change or alter at least one property of the photohardenable composition creating an altered region in the photohardenable composition at an occurrence of the intersection, and subsequently exposing the altered region to at least a third excitation light to further process an exposed altered region to partially or fully form at least a portion of at least one three-dimensional object.

[0053] Preferably the at least three excitation lights include at least a first excitation light comprising a first light sheet including a first wavelength, a second excitation light comprising an optical image including a second wavelength, and a third excitation light comprising a second light sheet including a third wavelength.

[0054] Methods, systems, and printhead modules in accordance with the present invention are particularly advantageous for use in volumetric printing at least on three-dimensional object in a volume of a photohardenable composition including a photohardenable component and a dual-wavelength photoinitiators.

[0055] The present invention advantageously can facilitate production of one or more three- dimensional objects with improved accuracy and minimal defects in contrast to a volumetric printing method and system including an intersection or overlap of a first excitation light (e.g., light sheet) and second excitation light (e.g., an optical image) in forming a three- dimensional object in a volume of photohardenable composition without subsequent exposure of an altered region created by the intersection or overlap of the first and second excitation lights to a third excitation light (e.g., a second light sheet).

[0056] In methods and systems described herein, the altered region or initial patterning of the photohardenable composition created at the intersection or overlap of the first excitation light, e.g., in the form of a light sheet, and the second excitation light, e.g., in the form of an optical image, is preferably not fully cross-linked or polymerized or hardened, with additional cross-linking, polymerization, or alteration of the altered region occurring during the subsequent exposure of the altered region or initial patterning to the third excitation light, e.g., in the form of second light sheet. This can reduce the extent of cross-linking, polymerization, or photohardening to be achieved at the intersection or overlap, which can provide a reduction in inaccuracies and defects in the object being formed.

[0057] By carrying out the exposure to the third excitation light subsequent to the creation of the altered region at the intersection or overlap of the at least first and second excitation lights, there is a passage of time between the creation of the altered region and additional processing to further cross-link, polymerize, or photoharden the altered region. The amount of time between the intersection of the at least first and second excitation lights and the exposure to the third excitation wavelength can affect diffusion, where more time will result in more diffusion in the photohardenable composition. This diffusion can be helpful, as it may be useful for minimizing or removing artifacts such as pixel lines that may result, for example, from the generation of an optical image using a spatial light modulator.

[0058] The amount of time between the intersection of at least the first and second excitation lights to create an altered region (e.g., an initial pattern) in the photohardenable composition and the exposure of the altered region (e.g., the initial pattern) to a third excitation is preferably controlled to help manage diffusion. Such time can be controlled, for example, but not limited to, modifying the distance between a point at which the at least two first excitation wavelengths are position to intersect and the position at which the second light sheet enters the container to overlap the altered region, allowing for selection of an amount of time between creation of the altered region and further photohardening the altered region by exposure to the third excitation light effective for controlling the quality of one or more surface features of an object being form and / or minimizing printing artifacts such as surface roughness or other surface artifacts. There may be an optimal amount of time for a given printing condition. More diffusion may cause a reduction in surface artifacts such as roughness, but too much diffusion may cause a loss of sharpness of features in the parts..

[0059] In the inventions described herein, a third excitation light is preferably engineered to be wider or more angularly diverse than a first excitation light. A third excitation light with such increased angular diversity or increased width can reduce defect formation during the exposure of the altered region to a third excitation wavelength in at least partially or fully forming at least a region of a three-dimensional object being formed.

[0060] A second light sheet that is wider or more angularly diverse than the first light sheet that intersects with the optical image may also be referred to herein as a “light curtain”.

[0061] For example, in aspects of the present invention including alteration of the photohardenable composition at the intersection of a first excitation light comprising a first light sheet and a second excitation light comprising an optical image, the first light sheet typically can be a light sheet formed from highly directional light, which tends to cause formation of artifacts such as self-written waveguides which can manifest when photohardening occurs in the presence of highly directional light, causing defects and roughness in the photopatterned object.

[0062] While it may seem that use of a wider light sheet or multidirectional light at the intersection might be beneficial to avoid artifacts resulting from use of a thin light sheet created by highly direction light, including a wider light sheet or multidirectional light at the intersection can sacrifice resolution in the altered region formed at the intersection and in the resulting three-dimensional object.

[0063] The present invention can overcome this challenge by performing an initial alteration of at least one property of the photohardenable composition in the volume (e.g., forming an initial pattern at a selected location in the photohardenable composition) formed at the intersection of a first excitation light preferably comprising a first light sheet including a first wavelength. Preferably the first light sheet is formed with directional light and has a width which is capable of forming an altered region comprising an initial pattern with relatively higher resolution at the first position, followed by subsequent exposure of the altered region by a third excitation light comprising a second light sheet that is wider or more angularly diverse than the first light sheet to further alter (e.g., further photoharden, polymerize, cross link, or otherwise alter) the previously altered region or initial patterning.

[0064] A second light sheet can be engineered to have less directional light, by, for example, but without limitation, a method including one or more of use of a light system such as higher numerical aperture light, inclusion of a stationary or spinning diffuser in the light path of the second light sheet before entering the container, inclusion of a stationary or spinning microlens array in the light path of the second light sheet before entering the container, or other methods for making a wider or more angularly diffuse second light sheet. This engineering of the second light sheet can allow formation of objects with reduced amounts of defects, inaccuracy and roughness.

[0065] In accordance with one aspect of the present invention, there is provided a method for forming at least one three dimensional object in a volume of a photohardenable composition, the method comprising: a. exposing a selected location in the volume of the photohardenable composition to at least two intersecting excitations lights to alter at least one property of the photohardenable composition at an occurrence of an intersection at a selected location creating an altered region of the photohardenable composition at the intersection, wherein the at least two intersecting excitation lights include at least one first excitation light and at least one second excitation light; b. subsequently exposing the altered region of the photohardenable composition to at least one third excitation light to further process an altered region; and c. optionally repeating steps a. and b. one or more times until the at least one object is partially or fully formed, wherein, for a repeated set of steps, the selected location in a repeated set of steps is the same as or different from a previous selected location.

[0066] In an optional step c., any altered region in a repeated step a. can have a configuration that is the same as or different from that of a previous step a.

[0067] In accordance with another aspect of the present invention, there is provided a method of forming one or more three dimensional objects in a volume of a photohardenable composition, the method comprising: a. providing a container containing the volume of the photohardenable composition; b. directing at least two excitations lights to a selected location in the volume to intersect at the selected location in the photohardenable composition to alter at least one property of the photohardenable composition at the intersection creating an altered region of the photohardenable composition, wherein the at least two excitation lights include at least one first excitation light comprising a light sheet including a first wavelength and at least one second excitation light comprising an optical image including a second wavelength; c. subsequently exposing the altered region of the photohardenable composition to at least one third excitation light to further change at least one property of the altered region to at least partially form a three-dimensional object, wherein at least one of the third excitation lights comprises a second light sheet including a third wavelength; and d. optionally repeating steps b. and step c. one or more times until the at least one object is partially or fully formed, wherein, for a repeated set of steps, any selected location is the same as or different from a previous selected location and any optical image is the same as or different from that of a previous optical image. Optionally, step b. can further include directing a third light sheet into the volume from a different side (e.g., opposite) side of the container from the first light sheet, the third light sheet being directed along a third light path that overlaps the first light path of the first light sheet such that the first and third light sheets are overlapping and both intersect the optical image during creation of the altered region of the photohardenable composition. Optionally the altered region can comprise an initial pattern for at least a portion of the object being printed.. Preferably the third light sheet includes the first wavelength.

[0068] In accordance with another aspect of the present invention, there is provided a method of forming at least one object in a volume of a photohardenable composition, the method comprising: a. providing a container containing the volume of the photohardenable composition; b. directing two excitation lights to form an intersection at a first position in the container, wherein an initial patterning of at least a portion of an object in the photohardenable composition occurs at the intersection, wherein the initial patterning includes producing a first change in at least one property of the photohardenable composition, wherein the at least two excitation lights include a first excitation light and a second excitation light, wherein the first position is located at a selected location in the volume of the photohardenable composition; c. directing a third excitation light into the volume to overlap the initial pattern created at the selected location in the volume at which the first and second excitation lights previously intersected, wherein the overlap by the third excitation light occurs at a later time than the initial patterning and produces a second change in the initially patterned photohardenable composition, and d. optionally repeating steps b. and c. one or more times until the at least one object is partially or fully formed, wherein, for a repeated step, the initial patterning includes a configuration that is the same as or different from a previous initial pattern, 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. In accordance with another aspect of the present invention, there is provided a method of forming at least one 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 comprising a first light sheet including a first wavelength into the container along a first light path to a first position at a selected location in the photohardenable composition and directing a second excitation light comprising an optical image including a second wavelength into the container to the first position, wherein the light sheet and optical image light form an intersection, wherein an initial patterning of at least a portion of an object in the photohardenable composition occurs at the intersection, wherein the initial patterning comprises producing a first change in at least one property of the photohardenable composition at the selected location, wherein the first position is located at a selected location in the volume of the photohardenable composition; c. directing a third excitation light comprising a second light sheet including a third wavelength to the first position in the volume to overlap the initially patterned region of the photohardenable composition, wherein exposure by the third excitation light occurs at a later time than the initial patterning and produces a second change in the initially patterned region of the photohardenable composition; d. optionally repeating steps b. and c. one or more times until the object is partially or fully formed, wherein, for a repeated set of steps, the optical image is the same as or different from a previous optical image and the container is positioned such that the selected location is the same as or different from a previous selected location.

[0069] Optionally, step b. can further include directing a third light sheet into the volume from a different side (e.g., opposite) side of the container from the first light sheet, the third light sheet being directed along a third light path that overlaps the first light path of the first light sheet such that the first and third light sheets are overlapping and both intersect the optical image during the initial patterning. Preferably the third light sheet includes the first wavelength. In the methods described herein, it is preferred that the third excitation light not intersect with either of the first or second excitation lights in the volume during formation of an object.

[0070] Depending on the arrangement of the optical systems used to carry out the method and / or orientation of the light paths of the first, second, and third excitation lights in the volume of the photohardenable composition in the container, it may or may not be desirable to have the third excitation light turned on while the first and second lights are turned on.

[0071] In instances in which it is not desirable for the three excitation lights to be turned on at the same time, the third excitation light may be illuminated or turned on at a later time when the first and second lights are turned off or not illuminated.

[0072] As discussed above, in the inventions described herein, non-limiting examples of a property of a photohardenable composition that can be altered or initially patterned at the intersection of the first and second excitation lights include a change in inhibitor concentration or a change in the degree of polymerization, solidification, hardening, or other alteration of the photohardenable composition.

[0073] FIG. 1 depicts an example of a system and method of the present invention. The depicted system includes a container containing a volume of a photohardenable composition 110, a first light sheet generating system 111 oriented for directing a first excitation light comprising a first light sheet 112 including a first wavelength along a first optical path into the container containing the volume of the photohardenable composition, wherein the first excitation light comprising a light sheet 112 including a first wavelength intersects at a first position 116 with a second excitation light comprising an optical image 114 including a second wavelength generated by a projection system 120. The intersection of the first excitation light and second excitation light at the first position 116 in the container alters at least one property of the photohardenable composition creating an altered region (e.g., an initial pattern) in the photohardenable composition. The altered region can corresponds to an initial pattern representative of the optical image that intersects with the first light sheet at the first position. Typically an optical image corresponds to one of a series of sequential cross-sectional slices of the three-dimensional object being formed or “printed”. After the formation of an altered region at the first position in the container, the container can be translated in a linear direction away from the projector along the direction optical images are projected from the projection system. Such translation of the container moves the position of the altered region in the container to a position at which the third excitation light comprising a second light sheet 118 including a third wavelength traverses the container and overlaps the altered region to change at least one property of the altered region to at least partially form at least a portion of the three-dimensional object being formed.

[0074] As shown in the depicted example, a second light sheet generating system 130 is positioned such that the light path of the second light sheet generated thereby through the volume is substantially parallel to, and spaced from, that of the first light sheet. The distance between the locations at which the first and second light sheets traverse the container and the rate at which the container is translated can affect the amount of time between the creation of the altered region created by the intersection of the first and second excitation lights and the subsequent overlap of the altered region by the third excitation light.

[0075] In the configuration of the example of the system depicted in FIG. 1 orientation, the light path of the projected optical image and the light path the second light sheet traversing the container cross in the photohardenable composition. To prevent the optical image and the second light sheet from intersecting in the photohardenable composition and creating unwanted changes therein, it is preferred to not illuminate these two light excitations at the same time. Instead, as an example, a patterning would first occur at the intersection of the light sheet and the projected image, and when that patterning is complete and those light excitations are turned off, the traversal of this patterned volume by the second light sheet would occur.

[0076] FIG. 2 depicts an example of a system and method of the present invention including a container 210 containing a volume of a photohardenable composition, wherein a first excitation light comprising a light sheet 212 including a first wavelength intersects with a second excitation light comprising an optical image 214 including a second wavelength at a first position 216. The intersection of the first light sheet and optical image at the first position 214 may also be referred to herein as the print plane. A third excitation light comprising a second light sheet 218 is directed into the container and overlaps the first position subsequent to (e.g., at a later point in time) the occurrence of the previous intersection of the first and second excitation lights to create a first change (e.g., an initial patterning) in the photohardenable composition. (FIG. 2. does not depict the intersection of the second light sheet 218 with the first position 216 occurring after repositioning of the first position relative to the position of the second light sheet.) In the depicted example, the first excitation light and second excitation light enter the container from the same face of the container and a third excitation light comprising a second light sheet including a third wavelength sheet is configured for the light path of the third excitation light to be directed into the container so as to not intersect the light paths of the first and second excitation lights in the volume while the first and second excitation lights intersect in the photohardenable composition. In the depicted example, the container and / or the optical systems can be moved to reposition the first position or selected location at which the first and second excitation lights intersected to create a change in the photohardenable composition for being exposed to the third excitation (e.g., second light sheet). In this configuration, the third excitation light path does not intersect the light path of either the first excitation light (e.g., the first light sheet) or the second excitation light (e.g., the optical image) within the photohardenable composition. Since the lights paths of the first, second, and third excitation lights do not cross or intersect in the volume in the depicted example, the three excitation lights can be illuminated at the same time for a portion or all of the printing process. While FIG. 2 shows that the first excitation light (e.g., first light sheet) and the second excitation light (e.g., optical image) enter the container from the same face of the container, it is not necessary. For example, the light sheet and the projected image may enter from different, such as opposite, faces of the container. Likewise, the second light sheet and either or both of the first light sheet or projected image need not enter the container from the same face of the container. For example, the second light sheet and the first light sheet may enter from different, such as opposite, faces of the container, or the second light sheet and the projected image may enter from the same face, or from different faces, such as opposite or adjacent faces of the container. (The depicted example also depicts a first optical system 211 comprising a first light sheet generating system from which a first excitation light (e.g., a first light sheet) 212 is directed to the first position 216 in the volume, a second optical system 220 comprising a projection system from which a second excitation light (e.g., an optical image) 214 is directed to the first position 216 to intersect with the first excitation light, and a third optical system 230 comprising a second light sheet generating system for directing a third excitation light (e.g., a second light sheet) 218 into the volume.

[0077] FIG. 3 depicts an example of a system and method of the present invention including a container 310 containing a volume of a photohardenable composition, wherein a first excitation light 311 comprising a light sheet including a first wavelength intersects with a second excitation light 314 comprising an optical image including a second wavelength at a first position 316. A third excitation light 318 comprising a second light sheet is directed into the container for overlapping the first position subsequent to (e.g., at a later point in time) the occurrence of the previous intersection of the first and second excitation lights to create a first change (e.g., an initial patterning) in the photohardenable composition. Preferably the locations of the first position and / or the third excitation light path can be moved relative to each other to facilitate the intersection of the altered region or initial pattern formed at the first position with the third excitation light. In the depicted example, the first excitation light and second excitation light enter the container from the same face of the container and a third excitation light comprising a second light sheet including a third wavelength sheet is configured for the light path of the third excitation light to be directed into the container so as to not intersect the light paths of the first and second excitation lights in the volume while the first and second excitation lights intersect in the photohardenable composition (referred to as resin in the FIG.).

[0078] The example shown in FIG. 3 further includes an optical alignment element 340 through which the first light sheet 312, optical image 314, and second light sheet 318 pass before entering the container 310. The optical alignment element modifies the angle at which each excitation light enters the container of the photohardenable composition relative to the first light path, projected image, and second light sheet in the absence of the optical alignment element. In this configuration, the second light sheet light path does not intersect the projected image light path within the photohardenable composition, and therefore it may be turned on at the same time as the projected image for a portion or all of the printing process. While the figure shows that the light sheet and the projected image enter the container from the same face of the container, it is not necessary. For example, the light sheet and the projected image may enter from different, such as opposite, faces of the container. Likewise, the second light sheet and either or both of the first light sheet or optical image need not enter the container from the same face of the container. For example, the second light sheet or light curtain and the first light sheet may enter from different, such as opposite or adjacent, faces of the container, or the second light sheet and the optical image may enter from different, such as opposite or adjacent, faces of the container.

[0079] FIG. 3 also depicts a first optical system 311 comprising a first light sheet generating system from which a first excitation light (e.g., a first light sheet) 312 is directed to the first position 316 in the volume, a second optical system 320 comprising a projection system from which a second excitation light (e.g., an optical image) 314 is directed to the first position to intersect with the first excitation light, and a third optical system 330 comprising a second light sheet generating system for directing a third excitation light (e.g., a second light sheet) 318 into the volume.

[0080] FIG. 4A depicts an exemplary optical lens fabricated using a method described herein. FIG. 4B depicts a representative 2D height map of the surface of a lens printed using the method described herein, where the surface mean roughness value (Sa) was measured to be on average 55 nanometers.

[0081] Optionally, first, second or third excitation lights can pass through a single or multiple optical alignment elements before entering the container including a volume of a photohardenable composition.

[0082] An optical alignment element can affect the angles at which an excitation light enters the container including the photohardenable composition compared to the angles in the absence of the optical alignment element.

[0083] Passing excitation lights that intersect in the volume of the photohardenable composition through the same or different optical alignment elements can also affect that angle at which they intersect in the volume of the photohardenable composition compared to the angles at which they would intersect in the absence of the optical alignment element.

[0084] Preferably, a light path entering an input surface of an optical alignment element enters the input surface at a selected angle.

[0085] Optionally, any one or more of the first, second, or third excitation lights can pass through an optical alignment elements before entering the container. If a method or system includes more than three excitation lights, the additional excitation lights can also optionally pass through an optical alignment element before entering or passing into the container. If more than one excitation light passes through an optical alignment element, each can pass through a separate optical alignment. If more than one excitation light passes through an optical alignment element, each can pass through the same optical alignment element or each can pass through a different optical alignment element. For example, in methods or systems including two intersecting excitation lights, each can pass through a single or the same optical alignment element or each can pass through a separate or different optical alignment element. Optionally, due to system design considerations concerning where each of the at least three excitation lights enter the container, the at least two intersecting excitation lights can pass through the same single optical alignment element or separate optical alignment elements with the third excitation light passing through a different optical alignment element.

[0086] The portion of a light path as it exits an optical system from which it is generated is also referred to herein as an optical axis.

[0087] A third excitation light preferably comprises a second light sheet. More preferably a second light sheet is a light sheet that is on average wider during its traversal through the photohardenable composition than the average width of the light sheet used, for example, as the source of the first excitation light, for the initial patterning during its traversal through the photohardenable composition.

[0088] In the methods described herein, the light path of the at least one first excitation light including the first wavelength and the light path of the at least one third excitation light are oriented or orientable to be approximately parallel to each other when passing through the volume of the photohardenable composition.

[0089] In the methods described herein, a first excitation light does not intersect or overlap with a third excitation light within the volume of the photohardenable composition while either is turned on.

[0090] In the methods described herein, a second excitation light does not intersect or overlap with a third excitation light within the volume of the photohardenable composition while either is turned on.

[0091] In the methods described herein, the second excitation light comprising a projected image may feature brightness variations, such as a brighter contour of the image versus the bulk, brighter image one side relative to the other, or any other possible image brightness variation.

[0092] Optionally a method in accordance with the present invention can further include passing any one or more of the excitation lights through an optical alignment element before entering the container including a volume of a photohardenable composition. In such case, when more than one excitation light passes through an optical alignment element, one or multiple optical alignment elements can be used with any single optical alignment element having one or more than one excitation lights passing through it before entering the container. An optical alignment element can affect the angles at which an excitation light enters the container including the photohardenable composition compared to the angles in the absence of the optical alignment element. Passing excitation lights that intersect in the volume of the photohardenable composition through the same or different optical alignment elements can also affect that angle at which they intersect in the volume of the photohardenable composition compared to the angles at which they would intersect in the absence of the optical alignment element. In the methods described herein, depending on the configuration of the entry locations at which a first light sheet, an optical image, and a second light sheet enter the container, the second light sheet need not be turned off while the first light sheet and optical image are directed into the volume of the photohardenable composition. For example, as discussed herein, the second light sheet is preferably turned off while the first light sheet and optical image are illuminated to intersect at the first position if the configuration being used would result in the light paths of either or both of the first light sheet or optical image to cross or intersect with the light path of the second light sheet, if illuminated, in the photohardenable composition. In such configuration, the second light sheet is preferably turned off and not illuminated while either or both of the first light sheet or optical image are illuminated and passing through the photohardenable composition with the second light sheet being turned on or illuminated after (e.g., later in time) either or both of the first light sheet or optical image are turned off or the light paths thereof are not passing into or through the photohardenable composition.

[0093] In a configuration in which the light path of the second light sheet does not cross or intersect with light path of either or both of the first light sheet or optical image, the second light sheet may be illuminated or turned on and directed at the volume of the photohardenable composition at the same time either or both of the first light sheet or optical image are illuminated or turned on.

[0094] Methods and systems described herein can optionally further include changing the location of the container and / or the third optical system relative to each other to reposition or change the first position or selected location in the container relative to the position of the third optical system. Optionally the container and / or the third optical system can be moved or translation relative to each other for the first position and third excitation light to intersect. Optionally, in inventions described herein, at least two intersecting excitation lights can be generated by one or more optical systems that are preferably configured for the at least two intersecting excitation lights to intersect at a fixed position in which case the first position or selected position in the container is positioned to coincide with at the fixed position and the container can be moved relative to the fixed position to reposition the first position or a selected location in the volume of photohardenable composition in the container. In such case, the method can further include changing the location of the container relative to the fixed position to change the position of the first position or selected location in the volume.

[0095] 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.

[0096] Optionally, in a method described herein, first, second or third excitation lights can pass through a single or multiple optical alignment elements before entering the container including a volume of a photohardenable composition.

[0097] An optical alignment element can affect the angles at which an excitation light enters the container including the photohardenable composition compared to the angles in the absence of the optical alignment element.

[0098] Passing excitation lights that intersect in the volume of the photohardenable composition through the same or different optical alignment elements can also affect that angle at which they intersect in the volume of the photohardenable composition compared to the angles at which they would intersect in the absence of the optical alignment element.

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

[0100] Optionally, any one or more of the first, second, or third excitation lights can pass through an optical alignment elements before entering the container. If a method or system includes more than three excitation lights, the additional excitation lights can also optionally pass through an optical alignment element before entering or passing into the container. If more than one excitation light passes through an optical alignment element, each can pass through a separate optical alignment. If more than one excitation light passes through an optical alignment element, each can pass through the same optical alignment element or each can pass through a different optical alignment element. For example, in methods or systems including two intersecting excitation lights, each can pass through a single or the same optical alignment element or each can pass through a separate or different optical alignment element. Optionally, due to system design considerations concerning where each of the at least three excitation lights enter the container, the at least two intersecting excitation lights can pass through the same single optical alignment element or separate optical alignment elements with the third excitation light passing through a different optical alignment element.

[0101] 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 a first excitation light including a first wavelength, 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 including a second wavelength, 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; 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; and c. a third optical system for generating a third excitation light including a third wavelength, the third optical system including third optics for directing the generated third excitation light along a third light path to the first position in a container for containing the volume of the photohardenable composition, wherein the system is configured or configurable for the third excitation light to intersect with the first position after the intersection of the first and second excitation lights at the first position. Preferably, the system is configured or configurable such that the third excitation light is not directed to the first position at the same time as the first and / or second excitation lights, but subsequent thereto. For example, the system can preferably be configured such that the third excitation light (excluding back reflections) is not directed to the first position during exposure of the first position to the first excitation light and / or the second excitation light but is directed to intersect with the first position following the exposure of the first position to the first and second excitation lights.

[0102] More preferably the container and / or third optical system can alternatively or additionally be movable or translatable relative to each other such that he third excitation light can intersect with the first position after the intersection of the first and second excitation lights in the photohardenable composition.

[0103] The system can optionally further include a controller for operating or controlling one or more components and / or functions of the system.

[0104] Preferably the first and second optical systems are configured or configurable for the first and second excitation lights to enter the container through, or from, the same side or surface of the container.

[0105] Preferably, the first and second excitation lights are configurable to intersect at an adjustable fixed position in the container.

[0106] Optionally the first optics and second optics are fixed or movable relative to each other.

[0107] Optionally the system further includes an optical alignment element that is positioned or positionable for each of the first and second excitation lights to pass through a light input surface thereof before passing into the container. If included each of the first and second excitation lights preferably passes through different light input surfaces of the optical alignment element.

[0108] Optionally the system further includes two optical alignment elements that are positioned or positionable for each of the first and second excitation lights to pass through a light input surface of a different optical alignment element before passing into the container.

[0109] Optionally the system further includes a separate optical alignment element that is positioned or positionable for the third excitation lights to pass through a light input surface thereof before passing into the container. Preferably the first light path of the first excitation light and the third light path for the third excitation light are oriented or orientable to be approximately parallel to each other when passing through the volume of the photohardenable composition.

[0110] Preferably the first light path of the first excitation light and the third light path for the third excitation light are oriented or orientable to be non-overlapping within the volume of the photohardenable composition.

[0111] Preferably the second light path of the second excitation light and the third light path for the third excitation light are oriented or orientable to be non-overlapping within the volume of the photohardenable composition.

[0112] The system can optionally further include a translation mechanism. The translation mechanism can be used for changing, for example, the location of the container to change the position of a selected location in the container relative to one or more excitation lights. Optionally, the translation mechanism can alternatively or additionally be used to change the position of one or more of the first, second, or third excitation lights relative to the container to change the position of a selected location in the container.

[0113] When an optical alignment element is optionally included in the system, it is preferably in direct contact or optically coupled to the surface of the container through which the first and second light paths enter the container.

[0114] Optionally a container may include one or more anti-reflective or absorptive coatings to prevent back reflections of any of the excitation lights used for the method.

[0115] Preferably, a light path entering an input surface of an optical alignment element enters the input surface at a selected angle.

[0116] 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 first light sheet from a first excitation light including a first wavelength, 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 including a second wavelength, 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 and second light paths are configured or configurable such that the first and second light paths intersect at the first position in the container; and c. a second light sheet generating system for generating a second light sheet from a third excitation light including a third wavelength, the second light sheet generating system including third optics for directing the second light sheet along a third light path to the first position after the intersection of the first and second excitation lights at the first position.

[0117] Preferably, the system is configured or configurable such that the third excitation light is not directed to the first position at the same time as the first and / or second excitation lights, but subsequent thereto. For example, the system can preferably be configured such that the third excitation light (excluding back reflections) is not directed to the first position during exposure of the first position to the first excitation light and / or the second excitation light but is directed to intersect with the first position following the exposure of the first position to the first and second excitation lights.

[0118] More preferably the container and / or second light sheet generating system can alternatively or additionally be movable or translatable relative to each other such that he third excitation light can intersect with the first position after the intersection of the first and second excitation lights in the photohardenable composition.

[0119] Preferably the second light sheet does not intersect (excluding back reflections) with the first light sheet or the optical image projection in the photohardenable composition during printing.

[0120] Optionally, the system can further include a fourth optical system comprising a third light sheet generating system for generating and directing a third light sheet for into the volume from a different side (e.g., opposite) side of the container from the first light sheet, the third light sheet being directed along a third light sheet path that overlaps the first light path of the first light sheet such that the first and third light sheets are overlapping and both intersect the optical image during the initial patterning. Preferably the third light sheet includes the first wavelength. The system can optionally further include a controller for operating or controlling one or more components and / or functions of the system.

[0121] Optionally the first and second optical systems are configured or configurable for the first and second excitation lights to enter the container through, or from, the same side or surface of the container.

[0122] Optionally, the first and second excitation lights are configurable to intersect at an adjustable fixed position in the container.

[0123] Optionally the first optics and second optics are fixed or movable relative to each other.

[0124] Optionally, a system can further include a fourth light sheet generating system for generating and directing a third light sheet for into the volume from a different side (e.g., opposite) side of the container from the first light sheet, the third light sheet being directed along a third light path that overlaps the first light path of the first light sheet such that the first and third light sheets are overlapping and both intersect the optical image during the initial patterning. Preferably the third light sheet includes the first wavelength.

[0125] Preferably each of the light sheet and optical image is oriented or orientable to pass through a single optical alignment element or different optical alignment elements.

[0126] Preferably each of the first light sheet, optical image, and second light sheet are oriented or orientable to pass through a single optical alignment element or different optical alignment elements.

[0127] Preferably the first light sheet of the first excitation light and second light sheet of the third excitation light are oriented or orientable to be approximately parallel to each other when passing through the volume of the photohardenable composition.

[0128] Preferably the first light sheet of the first excitation light and the second light sheet of the third excitation light are oriented or orientable to be non-overlapping within the volume of the photohardenable composition.

[0129] Preferably the optical image of the second excitation light and the second light sheet of the third excitation light are oriented or orientable to be non-overlapping within the volume of the photohardenable composition. A system described herein is preferably configured or configurable for the third excitation light to intersect with the first position after the intersection of the first and second excitation lights at the first position and after repositioning the container and / or third excitation relative to each other such that the first position at which of the first and second excitation lights intersected is repositioned to intersect with the third excitation light.

[0130] As discussed above, systems and methods described herein can optionally further include a translation mechanism. The translation mechanism can be used for changing, for example, the location of the container to change the position of a selected location in the container relative to one or more excitation lights. Optionally, the translation mechanism can alternatively or additionally be used to change the position of one or more of the first, second, or third excitation lights relative to the container to change the position of a selected location in the container. Optionally, in a system described herein, the at least two intersecting excitation lights can be generated by one or more optical systems including optics that are preferably configured for the at least two intersecting excitation lights to intersect at a fixed position in which case the first position or selected position in the container is positioned to coincide with at the fixed position and the container can be moved relative to the fixed position to reposition the first position or a selected location in the volume of photohardenable composition in the container. Optionally a translation mechanism can be controllable.

[0131] 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.

[0132] When an optical alignment element is optionally included in the system, it is preferably in direct contact or optically coupled to the side or surface of the container through which the first and second light paths enter the container.

[0133] Preferably, a light path entering an input surface of an optical alignment element enters the input surface at a selected angle.

[0134] Optionally a container may include one or more anti-reflective or absorptive coatings to prevent back reflections of any of the excitation lights used for the method. In certain embodiments, it is preferred for the light paths of first excitation light and the third excitation light through the volume to be parallel or substantially parallel to each other, as this arrangement causes there to be a similar amount of time between initial patterning by first and second excitation lights and the further excitation by the third light of the patterned volume for all portions of the patterned volume.

[0135] Design of systems and methods described herein can preferably take into consideration factors that include, for example, but not limited to, the part(s) to be printed (e.g., size, shape, thicknesses, etc.), the container in which the part(s) are printed (e.g., its refractive index, size, wall thicknesses, etc.), refractive index of the printing resin, and light sheet thickness in the printing resin, the projection width in air, and width dimension of the build volume along the direction of motion of the container relative to projection and light sheet.

[0136] Preferred systems and methods of the invention include one or more of the following features.

[0137] In preferred systems and methods of the invention, the focal plane of the optical image projection and the first light sheet overlap within the resin. More preferably the overlap is colinear or substantially colinear for enhancing resolution of features of the printed part.

[0138] In preferred systems and methods of the invention, back-reflections off a face of the container from the optical image projection, the first light sheet, and second light sheet or light curtain do not overlap with the excitation light of optical image projections, the first light sheet, and second light sheet or light curtain directed into the container for printing the part(s). Reducing such back-reflections can facilitate better part surface quality.

[0139] In preferred systems and methods of the invention, the first light sheet has a thickness selected for achieving the desired resolution of the part(s) to be printed.

[0140] In preferred systems and methods of the invention, the second light sheet or light curtain has a thickness and angular divergence selected to achieving desired part smoothness.

[0141] In preferred systems and methods of the invention, a build volume is selected to have a width appropriate to accommodate the size(s) of the part(s) to be printed therein. FIG. 5 depicts an example of a system and method of the present invention including a container 510 containing a volume of a photohardenable composition (or printing resin), wherein a first excitation light comprising a light sheet 512 including a first wavelength intersects with a second excitation light comprising an optical image 514 including a second wavelength intersect at a first position 516 in the composition. The intersection of the first light sheet and optical image at the first position 516 can also be referred to as a print plane. The depicted system and method includes an aperture 550 positioned between the second optical system comprising a projection system and the container for controlling the projection of the second excitation light into the container to the first position. A third excitation light comprising a second light sheet 518 is directed into the container and overlaps the first position subsequent to (e.g., at a later point in time) the occurrence of the previous intersection of the first and second excitation lights to create a first change (e.g., an initial patterning) in the photohardenable composition. In the depicted example, the first excitation light and second excitation light enter the container from the same face of the container and a third excitation comprising a second light including a third wavelength sheet is configured for the light path of the third excitation light to be directed into the container so as to not intersect the light paths of the first and second excitation lights in the volume while the first and second excitation lights intersect in the photohardenable composition. In the depicted example, the container and / or the optical systems can be moved to reposition the first position or selected location at which the first and second excitation lights intersected to create a change in the photohardenable composition for being exposed to the third excitation (e.g., second light sheet). In this configuration, the third excitation light path does not intersect the light path of either the first excitation light (e.g., the first light sheet) or the second excitation light (e.g., the optical image) within the photohardenable composition. Since the lights paths of the first, second, and third excitation lights do not cross or intersect in the volume in the depicted example, the three excitation lights can be illuminated at the same time for a portion or all of the printing process. While FIG. 5 shows that the first excitation light (e.g., first light sheet) and the second excitation light (e.g., optical image) enter the container from the same face of the container, it is not necessary. For example, the light sheet and the projected image may enter from different, such as opposite, faces of the container. Likewise, the second light sheet and either or both of the first light sheet or projected optical image need not enter the container from the same face of the container. For example, the second light sheet and the first light sheet may enter from different, such as opposite, faces of the container, or the second light sheet and the projected image may enter from the same face, or from different faces, such as opposite or adjacent faces of the container. The depicted example include a first optical system comprising a first light sheet generating system 511, a second optical system comprising a projection system 520, and a third optical system comprising a second light sheet generating system 530 for creating and directing a first light sheet, an optical image, and second light sheet, respectively.

[0142] Fig. 5 also identifies a number of parameters that can be included in a system and method described herein, the selection of any one or more of which can be useful for achieving one or more of the above-described preferred features. In the figure:

[0143] A refers to the angle of the container with respect to the direction of the optical image projection. Preferably angle A is selected to be an angle at which the entire focal plane to reside in the printing resin. More preferably, A is the smallest angle at which this can occur.

[0144] B refers to the angle of the light sheet and curtain with respect to the direction of the optical image projection. Preferably angle B is selected to be an angle that results in the light sheet being at the same angle as the projection focal plane in the resin. [It can be desirable to set the light sheet thickness in air to provide the desired light sheet thickness in the printing resin.

[0145] C refers to the distance from the center of the light sheet to the center of the optical image projection (along the long dimension of the container). C is preferably selected for achieving colinear or substantially colinear overlap of the light sheet and optical image projection in the printing resin.

[0146] D refers to the distance from the center of the light sheet to the center of the light curtain (along the long dimension of the container). Preferably D is selected to have a value that avoids overlap of back-reflection from the light curtain with the light sheet and / or the optical image projection. More preferably D is the smallest distance for avoiding such overlap. It can be desirable to set the light curtain thickness in air to provide the desired light curtain thickness in the printing resin.

[0147] E refers to the width of the printing resin in the container (along the direction of relative movement between the container and the optical image / light sheet / light curtain). Preferably E is selected to be large enough to accommodate printing of the full size of the desired part.

[0148] While it can be most preferred to address all of parameters A through E, addressing only one or combinations of more than one, can be advantageous.

[0149] Optionally, methods, systems, and printhead modules described herein can include a fifth optical system comprising a fourth light sheet generating system for generating and directing a fourth light sheet including a fifth wavelength into the volume from a different side (e.g., opposite) side of the container from the second light sheet, the fourth light sheet being directed along a fourth light sheet path that overlaps the light path of the second light sheet such that the second and fourth light sheets are overlapping and both intersect the first position or selected location following the creation of an altered region or initial patterning resulting from the intersection of the first and second excitation light at the first position (or selected location). Preferably the second and fourth light sheets include the same wavelength.

[0150] Methods and systems described herein including a first excitation light comprising a first light sheet, a second excitation light comprising a projected optical image, and a third excitation light comprising a second light sheet, can preferably include one or more of following features (i)-(v):

[0151] (i) the container is at an angle with respect to the direction in which the optical image is directed into the volume that is selected such that the optical image has a focal plane that fully lies within the printing resin;

[0152] (ii) the first light sheet is at an angle with respect to the light path of the optical image projection that is selected to be an angle that results in the first light sheet being at the same angle as the optical image focal plane in the resin;

[0153] (iii) each of the first light sheet and the optical image projection has a dimension along the direction of motion of the container relative to the optical image projection and first light sheet , and the distance from the mid-point of the two dimensions is selected for achieving a colinear or substantially colinear overlap of the light sheet and optical image projection in the printing resin;

[0154] (iv) each of the first light sheet and the second light sheet has a dimension along the direction of motion of the container relative to the first light sheet, and the second light sheet, and the distance from the mid-point of the two dimensions is selected for avoiding overlap of back-reflection from the second light sheet and / or the first light sheet with light curtain with the first light sheet and / or the optical image projection;

[0155] (v) a dimension of the printing resin in the container along the direction of relative movement between the container and the optical image / light sheet / light curtain) is selected to be large enough to accommodate printing a full size object.

[0156] 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 first excitation light comprising a first light sheet including a first wavelength along a first light path to a first position in a container for including the volume including a photohardenable composition; b. second optics for directing a second excitation light comprising a second optical image including a second wavelength along a second light path to the first position in the container; wherein the first optics and second optics are configured or configurable to direct the first and second light paths to intersect at the first position; and c. third optics for directing a third excitation light comprising a second light sheet including a third wavelength along a third light path, the third optics being configured or configurable such that the third light path and first light path are substantially parallel to each other within the container.

[0157] Preferably the third light path for an illuminated second light sheet does not to cross or intersect with the first light path for an illuminated first light sheet and / or the second light paths for an illuminated optical image in the volume of photohardenable composition during printing.

[0158] 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. 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.

[0159] Preferably the light sheet and optical image intersect or 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).

[0160] Preferably the third light excitation path does not overlap the first or second light excitation path at any given time at any given point in the photohardenable composition. This condition can be preferably be achieved either by timing excitation so that the third light excitation is not substantially or at all excited at the same time as the first or second light excitation, or in the case that the third light excitation light is illuminated at the same time as the first or second excitation light, by selected light paths such that the third excitation light does not substantially or at all overlaps (excluding back reflections) the first or second excitation light paths at the same time at a substantially the same position within the volume of the photohardenable composition.

[0161] In methods, systems, and printhead modules described herein, the first and second excitation lights (whether in a light sheet, optical image, or other configuration) may be oriented or orientable to enter the photohardenable composition from or through the same side or surface 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 cross-section).

[0162] If an optical alignment element is used, an optical alignment element 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. When optionally included in a method or system described herein, an optical alignment element is preferably in direct or indirect contact (e.g., optically coupled) 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.

[0163] 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 first light sheet, an optical image, a second light sheet or other configuration) enters the container.

[0164] FIG. 1 depicts example of a system and method of the present invention including a container containing a photohardenable composition, where the first excitation light is a light sheet that intersects the second excitation light which is a projected optical image at an angle of approximately 90 degrees to the light sheet. The third excitation light comprises a second light sheet. In this particular example, the light path of the second excitation light and the third excitation light intersect within the photohardenable composition. Therefore, these two lights are not illuminated at the same time. In this configuration, an object is first to be patterned at the intersection of the first and second light excitations, and when this patterning is completed, the container and / or optics are moved relative to each other such that the third excitation light is illuminated at the initially patterned volume and is then moved relative to the container to illuminate the entire initially patterned volume with the third excitation light.

[0165] 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.

[0166] The methods, systems and printhead modules described herein can further be adapted for computer control.

[0167] 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.

[0168] 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.

[0169] Preferably the overlap or intersection of the light sheet and the projected image in the common plane is substantially coplanar and more preferably coplanar.

[0170] 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. Preferably an object is formed layer by layer while suspended in the volume during printing, with the layers representing cross-sectional slices of the object.

[0171] As discussed above, FIG. 2 depicts an example of a system where the first light excitation is a light sheet, the second light excitation is an optical image, and the first and second light excitations enter the container of photohardenable material from the same face. The third optical excitation comprises a second light sheet that also enters the container from the same face, although entry from the opposite face along the same light path would also yield similar results. In this configuration, the second excitation light and the third excitation light (excluding back reflections) do not intersect in the photohardenable composition at the same time. Therefore, in this case, these two excitation lights may be illuminated at the same time. In this example, continuous translation of the container and the light excitations may occur relative to each other, where the first light excitation and the second light excitation intersect each other to cause an initial patterning of the photohardenable material within the volume of the container, and as translation continues, eventually the patterned locations will also overlap the location of the third excitation light, which may be in the form of a second light sheet, to cause further exposure of the initially patterned photohardenable composition. The distance between the first and third light excitation paths can be tuned to vary the time difference between exposure to the first light patterning between first light excitation and second light excitation and the later further exposure of the material by the third light excitation.

[0172] Preferably the positions of the first optics, the second optics and the third 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 the third optics relative to the position of the container.

[0173] 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.

[0174] As discussed above, FIG. 3 depicts an example of a method and system that is similar to that shown in FIG. 2 with the further inclusion of an optical alignment element that may be used to modify the angle at which one, two, or three of the light excitations enter the photohardenable composition. Note that a single optical alignment element is shown here, but various configurations, for example, multiple optical alignments are possible that vary alignment of one, two, or all three excitation lights separately or together.

[0175] FIG. 4A depicts an optical lens fabricated using the configuration depicted in FIG. 2, where the light sheet was approximately 200 microns thick (full width half max) of 405 nanometer light (~1.5 watt / cm2), the projected image was approximately 1 W / cm2of 532 nanometer light, and the second light sheet (or light curtain) was formed by irradiating 365 milliwatts of 405 nanometer light in the shape of a light sheet approximately 3 centimeters tall and 500 microns wide onto a spinning 5 degree engineered silica diffuser situated approximately 1 centimeter away from the container, with the container travelling relative to all the fixed excitation lights at a rate of approximately 1 mm every three seconds. FIG. 4B depicts a surface profile of this lens collected using a Bruker Contour profilometer, where color of gray in the image represents surface height, and location in x and y along the image map to locations in x and y on the surface of the lens. This surface measurement found a mean surface area roughness value Sa of 55 nanometers. In comparison, the surface roughness if printed simply using first and second excitation wavelengths was typically between 300 and 3000 nanometers Sa value.

[0176] A method and system 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.

[0177] The first excitation light can comprise a first light sheet. In this case, the light sheet is generated by methods known in the art such as 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 generate a line-shaped beam which is projected across a planar slice of a volume or space creating a sheet of light along the projection axis through the volume or space. Other strategies known in light sheet generation such as pivoting the light sheet beam, Bessel beam illumination, dual armed illumination, axial dithering, use of a diffuser can also be employed to tailor the properties of a second light sheet light that is wider or more angularly diverse than the first light sheet.

[0178] A projection system can comprise 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.

[0179] When the third excitation light comprises a second light sheet, and the first excitation comprises a first light sheet, the second light sheet may be referred to herein as a light curtain to differentiate it from the first light sheet, as a second light sheet or light curtain comprises a light sheet that is wider than the first light sheet or has an increase angular diversity compared to the first light sheet. The second light sheet may be formed by a method that includes modifying a method similar to a method used to form a first light sheet to further include engineering it to have an increased width or an increased amount of angular diversity. Preferably, the second light sheet further passes through a diffuser positioned in the light path between the second light sheet generating system and the container.

[0180] Light sources included in an optical system are preferably selected taking into consideration the photohardenable liquid being used and the hardening mechanism. Such considerations include the wavelength(s) preferred for the particular photohardening mechanism and power levels. Selection of suitable light sources is within the skill of the person of ordinary skill in the relevant art.

[0181] 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.

[0182] Forming multiple parts in the same container including photohardenable composition can be desirable. Multiple sets of first, second and third light excitations can optionally be used for printing multiple objects in a container at the same time to allow for faster printing.

[0183] For example, more than one arrangement or configuration including the first optics or a first light sheet generating system or and the second optics or a second optical system (e.g., for generating and projecting a second excitation light including a second wavelength (e.g., an optical image), and third optics or a third optical system (e.g., a second light sheet generating system for generating a second light sheet), which arrangement or configuration may further include one or more optical alignment elements, can be arranged around the container including a volume of the photohardenable composition to increase production volume and / or speed of printing. It is preferable when more than one arrangement or configuration is implemented that the paths of the first light sheets and paths of the optical images and paths of the second light sheets from any two such arrangements or configurations do not overlap or intersect to avoid crosstalk.

[0184] 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. 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:

[0185] 1. A three-dimensional (3D) object file is sliced into a set a two-dimensional (2D) image slices of a given thickness.

[0186] 2. Insert container including a volume of photohardenable composition onto printer (or pour or dispense photohardenable composition into a container).

[0187] 3. Optionally apply environmental control (temperature, degas, purge, sparge, gas curtain (air, nitrogen (N2), argon, or other inert gas)) to the container of photohardenable composition.

[0188] 4. Expose photohardenable composition 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, where the exposed volume is later further exposed by a second light sheet or light curtain.

[0189] 5. Change the position of at least one of (a) the container including the photohardenable composition and (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 composition.

[0190] (Optionally the container can be translated in discrete steps or otherwise can be translated at a continuous velocity.)

[0191] 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.

[0192] 7. Optionally wash off residual material from object using solvent, air curtain, centrifugal force, gravity, heating, etc.

[0193] 8. Optionally post-cure object, e.g., without limitation, in fluid, in air, in inert gas, apply UV and / or heating as required.

[0194] One or more change can optionally be made to the above process flow or different process flows may also be determined to be suitable in carrying out the methods described herein. 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.

[0195] 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, fluidic control or by pouring the photohardenable composition into the container.

[0196] The first optics and second optics can be positioned on top, below or to the side of the container.

[0197] The third optics can be positioned on top, below or to the side of the container.

[0198] 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.

[0199] 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.

[0200] 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.

[0201] An optical system, e.g., a projection system (e.g., for generating and projecting an optical image), or a light sheet generating system (e.g., a first light sheet generating system or a second light sheet generating system) 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 periodic application of light. Examples of periodic application of light includes pulsing. An optical image projection system and / or first light sheet generating systems and / or second 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. 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.

[0202] Excitation light can have a wavelength in the visible or invisible spectral range.

[0203] 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.

[0204] 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.

[0205] Taking into account the photohardenable composition and hardening mechanism being used, the wavelength of excitation light of the first light sheet, optical image and second light sheet may be the same or different. It can be desirable for the wavelength of the optical image to be longer than that of one or both of the first light sheet or second light sheet.

[0206] 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.

[0207] Methods and systems described herein include a photohardenable composition.

[0208] 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 photoswitches, dual-wavelength photoinitiators and any combinations thereof.

[0209] A photohardenable composition can include a photopolymerizable component.

[0210] 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. 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 photohardenable composition and / or photohardenable component thereof 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, dualwavelength photoinitiators, photo switchable 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, and a pH-sensitive photoinitiator.

[0211] 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.

[0212] 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. Preferred photoinitiators comprise a photo switchable photoinitiator which converts from a first form with a certain absorption spectrum to a second form with a different absorption spectrum via excitation light of a first wavelength, wherein locations exposed simultaneously or near simultaneously in time with both first and second wavelength experience a change in the photohardenable composition, such as inhibitor concentration, change in degree of polymerization, solidification , hardening or other alteration, that occurs faster than in the presence of either one of these excitation lights alone.

[0213] Information concerning photohardenable compositions, photo switchable 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,

[0214] 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,

[0215] 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.

[0216] Examples of preferred photo switchable 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.

[0217] Examples of compositional ranges for a photo switchable 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.

[0218] Examples of photo switchable photoinitiators useful in photohardenable compositions can absorb at about 300 to 460 nm. Depending upon the absorption spectrum for the particular photo switchable 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 photo switchable photoinitiator will preferably absorb in a range of about 460 to 1000 nm and 460 to 850 most typically.

[0219] 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.

[0220] 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.

[0221] In the methods and systems described herein, preferably the photohardenable composition included in the container displays non-Newtonian rheological behavior where the composition exhibits a yield stress. 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.

[0222] The methods and systems described herein can be used in combination with a computer and software. For example, a light sheet generating systems a projection system, and a projection device that may be included in a projection system, and a second light sheet generating systems 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 light excitations so that the part is developed plane by plane. Selection of computer controls and software is within the skill of the person of ordinary skill in the relevant art.

[0223] 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.

[0224] Methods and systems described herein are particularly useful for forming or “printing” three-dimensional objects.

[0225] Preferably a single optical projection of any of the first, second or third light excitations is insufficient to cause polymerization of the photohardenable composition.

[0226] 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.

[0227] 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.

[0228] 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.

[0229] Examples of container shapes 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.

[0230] Preferably the optically transparent portion(s) of the container is (are) also optically flat. Preferably the surface of the container at the entry points for the first and second excitation lights is planar.

[0231] Preferably the surface of the container at the entry points for the first and second excitation lights is optically transparent.

[0232] 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 or absorptive coatings on a light exit window of the container, blackening of a light exit portion or window of the container, sand blasting the light exit window of the container.

[0233] In the methods and systems 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.

[0234] In the methods and systems described herein, the container may be stationary while an optical projection of excitation light is being directed into the photohardenable composition.

[0235] In the methods and systems described herein, it may be desirable for the position of container be changeable, e.g., rotated, translated, etc., or held stationary.

[0236] 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 photohardenable composition at which the light sheet and optical image intersect, more preferably in a common plane.

[0237] 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 “DLPTM System Optics”; Texas Instruments “TI DLR Technology 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”, Int’l 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.

[0238] 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.

[0239] 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). 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.

[0240] 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.

[0241] 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.

[0242] 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.

[0243] 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 at least one object in a volume of a photohardenable composition, the method comprising: a. exposing a selected location in the volume of the photohardenable composition to at least two intersecting excitations lights to alter at least one property of the photohardenable composition at an occurrence of an intersection at a selected location creating an altered region of the photohardenable composition at the intersection, wherein the at least two intersecting excitation lights include at least one first excitation light and at least one second excitation light, b. subsequently exposing the altered region of the photohardenable composition to at least one third excitation light to further process an altered region; and c. optionally repeating steps a. and b. one or more times until the at least one object is partially or fully formed, wherein, for a repeated set of steps, the selected location is the same as or different from a previous selected location.

2. A method of forming one or more three-dimensional objects in a volume of a photohardenable composition, the method comprising: a. providing a container containing the volume of the photohardenable composition; b. directing at least two excitations lights to a selected location in the volume to intersect at the at the selected location in the photohardenable composition to alter at least one property of the photohardenable composition at the intersection creating an altered region of the photohardenable composition, wherein the at least two excitation lights includes at least one first excitation light comprising a light sheet including a first wavelength and at least one second excitation light comprising an optical image including a second wavelength; c. subsequently exposing the altered region of the photohardenable composition to at least one third excitation light to further change at least one property of the altered region to at least partially form a three-dimensional object, wherein at least one of the third excitation lights comprises a second light sheet including a third wavelength; andd. optionally repeating steps b. and c. one or more times until the at least one object is partially or fully formed, wherein, for a repeated set of steps, any selected location is the same as or different from a previous selected location and any optical image is the same as or different from that of a previous optical image.

3. A method of forming at least one object in a volume of a photohardenable composition, the method comprising: a. providing a container containing the volume of the photohardenable composition; b. directing two excitation lights to form an intersection at a first position in the container, wherein an initial patterning of at least a portion of an object in the photohardenable composition occurs at the intersection, wherein the initial patterning includes producing a first change in at least one property of the photohardenable composition, wherein the at least two excitation lights include a first excitation light and a second excitation light, wherein the first position is located at a selected location in the volume of the photohardenable composition; c. directing a third excitation light into the volume to overlap the initial pattern created at the selected location in the volume at which the first and second excitation lights previously intersected, wherein the overlap by the third excitation light occurs at a later time than the initial patterning and produces a second change in the initially patterned photohardenable composition, and d. optionally repeating b and c one or more times until the at least one object is partially or fully formed, wherein, for a repeated set of steps, the initial patterning includes a configuration that is the same as or different from a previous initial pattern, and the container is positioned such that the selected location is the same as or different from a previous selected location.

4. A method of forming at least one 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 comprising a first light sheet including a first wavelength into the container along a first light path to a first position in the photohardenable composition and directing a second excitation light comprising an optical image including a second wavelength into the container to the first position, wherein the light sheet and optical image light form an intersection, wherein an initial patterning of at least a portion of an object in the photohardenable composition occurs at the intersection, wherein the initial patterning comprises producing a first change in at least one property of the photohardenable composition at the selected location, wherein the first position is located at a selected location in the volume of the photohardenable composition; c. directing a third excitation light comprising a second light sheet including a third wavelength to the first position in the volume to overlap the initially patterned region of the photohardenable composition, wherein exposure by the third excitation light occurs at a later time than the initial patterning and produces a second change in the initially patterned region of the photohardenable composition; d. optionally repeating steps b. and c. until the object until the at least one object is partially or fully formed, wherein, for a repeated set of steps, the optical image is the same as or different from a previous optical image and the container is positioned such that the selected location is the same as or different from a previous selected location.

5. The method of claim 1 or 2 further comprising repositioning the container and / or third excitation relative to each other such that the selected location at which of the first and second excitation lights intersected is repositioned to intersect with the third excitation light.

6. The method of any one of claims 1-3 wherein a first excitation light includes a first wavelength of light, the second excitation light includes a second wavelength of light, and the third excitation light includes a third wavelength of light, wherein second wavelength of light is longer than the first or third wavelength of light, and the first and third wavelength can be the same or different.

7. The method of claim 4 wherein the second wavelength of light is longer than the first wavelength and / or third wavelength, and wherein the first wavelength is the same as or different from the third wavelength.

8. The method of claim 2 or 4 wherein the optical image comprises a two dimensional optical image corresponding to a two dimensional slice of the object to be printed.

9. The method of claim 8 wherein the optical image of a repeated step includes a subsequent slice of the object to be printed.

10. The method of claim 1 or 3 wherein the first excitation light comprises a first light sheet and / or the second excitation light comprises an optical image corresponding to a two dimensional slice of the object to be printed.

11. The method of claim 10 further comprising generating a two-dimensional slice of the object being printed based on a first angle and a second angle in the photohardenable composition at which the light sheet and optical image intersect, wherein the first light path is at the first angle at the first position and the second light path is at the second angle at the first position.

12. The method of claim 4 further comprising generating a two-dimensional slice of the object being printed based on a first angle and a second angle in the photohardenable composition at which the light sheet and optical image intersect, wherein the first light path is at the first angle at the first position and the second light path is at the second angle at the first position.

13. The method of claim 4, wherein the optical image of a repeated step includes a subsequent slice of the object to be printed.

14. The method of any one of claims 1-4 wherein the first and second excitation lights intersect at angle of about 90 degrees to each other in the photohardenable composition.

15. The method of any one of claims 1-4, wherein the first and second excitation lights intersect at an angle less than about 90 degrees in the photohardenable composition.

16. The method of any one of claims 1-4, wherein the method further comprises directing a third light sheet to the selected location in the container to overlap the first excitation light at its intersection with the second excitation light at their intersection at the selected location.

17. The method of claim 16 wherein the first and third light sheets are generated by two separate light sheet generators.

18. The method of claim 16 wherein the third light sheet is generated by a reflection of the first light sheet exciting the container back along its initial light path through the container.

19. The method of claim 1 or 2 wherein a repeated set of steps further includes moving one or more of the container, the first, second, and / or third excitation lights to reposition the location of the altered region for exposure to the third excitation light.

20. The method of claim 6 wherein the wavelength of the first excitation light is in a range from about 350 to 460 nanometers.

21. The method of claim 6, wherein the wavelength of the second excitation light is in a range from about 460 to 850 nanometers.

22. The method of claim 6, wherein the wavelength of the third excitation light is in a range from about 350 to 500 nanometers.

23. The method of any one of claims 1-4 wherein one or more objects produced by the method are suspended without displacement in the photohardenable composition.

24. The method of any one of claims 1-4 wherein the second light excitation is an optical image that project two dimensional slices corresponding to a plurality of slices of the object to be printed that are generated by slicing the object to be printed along a selected axial direction where these slices are designed to recreate the desired image pattern in the photohardenable composition at the intersection of the first and second light excitations.

25. The method of any one of claims 1-4 wherein the first, second and third light excitations are all fixed relative to each other.

26. The method of any one of claims 1-4 wherein the light paths of the first and third excitation lights through the volume are approximately parallel in the photohardenable composition.

27. The method of any one of claims 1-4 wherein any one or more of the first, second or third excitation lights are directed through an optical alignment element to modify the angle at which the excitation light passing through the optical element enters the photohardenable composition from its entry angle without passing through the optical alignment element.

28. The method of any one of claims 1-4 wherein the second light sheet has a width that is greater than that of the first light sheet.

29. The method of any one of claims 1-4 wherein the second light has a greater amount of angular diversity than that of the first light sheet.

30. The method of claim 28 wherein formation of the second light sheet further includes passing the second light sheet through a stationary diffuser or a moving diffuser.

31. The method of claim 29 wherein formation of the second light sheet further includes passing the second light sheet through a stationary diffuser or a moving diffuser.

32. The method of claim 28 wherein formation of the second light sheet further includes passing the second light sheet through a stationary microlens array or a moving microlens array.

33. The method of claim 29 wherein formation of the second light sheet further includes passing the as-generated second light sheet through a stationary microlens array or a moving microlens array.

34. The method of claim 28 wherein formation of the second light sheet further includes passing the as-generated second light sheet through a lens to produce light with a numerical aperture along the width of the light sheet at least twice that of the numerical aperture along the width of the first excitation light.

35. The method of claim 29 wherein formation of the second light sheet further includes passing the as-generated second light sheet through a lens to produce light with a numerical aperture along the width of the light sheet at least twice that of the numerical aperture along the width of the first excitation light.

36. The method of any one of claim 1-4 wherein the light paths of either or both of an illuminated first excitation light and an illuminated second excitation light do not cross or intersect with the light path of an illuminated third excitation light within the volume of the photohardenable composition during formation of an object.

37. The method of any one of the claims 1-4 wherein the photohardenable composition comprises a photopolymerizable component and a photoinitiator.

38. The method of claim 37 wherein the photoinitiator comprises a photoswitchable photoinitiator that is more sensitive at the intersection of the first and second excitation lights than the presence of the first or second excitation lights alone.

39. The method of claim 38 wherein the photohardenable composition further includes one or more coinitiators.

40. The method of claim 37 wherein the photohardenable composition contains one or more additives.

41. The method of any one of claims 1-4 wherein more than one object are formed in the container.

42. The method of any one of claims 1-4 wherein a spatial light modulator is used to generate the optical image.

43. A system for forming at least one three-dimensional object in a volume of a photohardenable composition, the system comprising: a combination including: a. a first optical system for generating at least one 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 at least one 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 the container for containing the volume of the photohardenable composition; wherein the first and second optics are configured or configurable such that the first and second light paths intersect at the first position in the container; and c. a third optical system for generating at least one third excitation light, the third optical system including third optics for directing the generated third excitation light along a third excitation light path to the first position in the container for containing the volume of the photohardenable composition,, wherein the system is configured or configurable for the third excitation light to intersect with the first position after the intersection of the first and second excitation lights at the first position.

44. A system for forming at least one object in a volume of a photohardenable composition, the system comprising: a combination including:a. a first light sheet generating system for generating a first excitation light comprising a light sheet including a first wavelength, the light generating system including first optics for directing the generated light sheet along a first light path to a first position at a selected location in a container for containing the volume of the photohardenable composition; b. a projection system for projecting a second excitation light comprising an optical image including a second wavelength, 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, wherein the first and second optics are configured or configurable such that the first and second excitation light paths intersect at the first position in the container; and c. a second light sheet generating system for generating a third excitation light comprising a second light sheet including a third wavelength light, the second light sheet generating system including third optics for directing the second light sheet along a third light path to the first position after the intersection of the first and second excitation lights at the first position.

45. The system of claim 43 wherein the first excitation light includes a first wavelength of light, the second excitation light includes a second wavelength of light, and the third excitation light includes a third wavelength of light.

46. The system of claim 44 or 45 wherein the second wavelength of light is longer than the first or third wavelength of light, and the first and third wavelength can be the same as or different from each other.

47. The system of claim 43 wherein the second excitation light comprises a two dimensional optical image corresponding to a two dimensional slice of the object to be printed.

48. The system of claim 44 wherein the optical image comprises a two dimensional optical image corresponding to a two dimensional slice of the object to be printed.

49. The system of claim 43 or 44 wherein the first and second optics are configured or configurable for the first and second light paths to intersect at an angle of about 90 degrees in the photohardenable composition.

50. The system of claim 43 or 44 wherein the first and second optics are configured or configurable for the first and second light paths to intersect at an angle less than about 90 degrees in the photohardenable composition.

51. he system of claim 43 or 44 wherein the light path of the third excitation light through the volume is approximately parallel to the that of the first excitation light.

52. The system of claim 43 or 44 wherein the system further includes a third light sheet generating system for generating a fourth excitation light comprising a third light sheet including a fourth wavelength, the third light sheet generating system including third optics for directing the third light sheet along a third excitation light path to overlap the first light sheet at the first position.

53. The system of claim 52 wherein the first wavelength and the fourth wavelength are substantially the same.

54. The system of claim 43 or 44 wherein the system further includes a reflection optics positioned or positionable for reflecting the first light sheet exiting the container back through the container along and the first light path, the reflected first light sheet overlapping the first light sheet passing through the container to form a combined light sheet.

55. The system of claim 44 or 45 wherein the first wavelength is in a range from about 350 to about 460 nanometers.

56. The system of claim 44 or 45 wherein the second wavelength is in a range from about 460 to about 850 nanometers.

57. The system of claim 44 or 45 wherein the third wavelength is in a range from about 350 to about 500 nanometers.

58. The system of claim 43 or 44 wherein the photohardenable composition comprises a photopolymerizable component and a photoinitiator.

59. The system of claim 58 wherein the photoinitiator comprises a photoswitchable photoinitiator that = undergoes photoinitiation more rapidly at the intersection of the first and second excitation lights than in the presence of either of the first or second excitation light alone.

60. The system of claim 58 wherein the photohardenable composition further includes one or more coinitiators.

61. The system of claim 58 wherein the photohardenable composition further includes one or more additives.

62. The system of claim 43 wherein the second optical system includes a spatial light modulator for generating an optical image.

63. The system of claim 44 wherein the projection system further includes a spatial light modulator for generating the optical image.

64. The system of claim 44 wherein the second light sheet system further includes a stationary diffuser or a moving diffuser in the third light path of the second light sheet before entering the container.

65. The system of claim 44 wherein the system further includes a stationary microlens array or a moving microlens array in the third light path of the second light sheet before entering the container.

66. The system of claim 44 wherein the system further includes a lens through which the as-generated second light sheet is passed to produce light with a numerical aperture along the width of the light sheet at least twice that of the numerical aperture along the width of the first excitation light.

67. The system of claim 44 wherein the system further includes an axicon lens in the third light path of the second light sheet before entering the container.

68. The system of claim 43 wherein the first, second and third optics are fixed relative to each other.

69. The system of claim 43 or 44 wherein any one or more of the first, second or third excitation lights are directed through an optical alignment element to modify the angle at which the excitation light passing through the optical element enters the photohardenable composition from its entry angle without passing through the optical alignment element.

70. The system of claim 43 or 44 further including a controller for operating and / or controlling one or more components and / or functions of the system.

71. The system of claim 70 wherein the controller is configured to selectively operate at least one, and preferably all, of generation and direction of the first excitation light, the second excitation light, and the third excitation light into the container.

72. The system of claim 43 or 44 further comprising a translation mechanism.

73. The system of claim 72 wherein the controller controls the translation mechanism and position of one or more of the container, the first optical system, the second optical system, and / or the third optical system relative to one or more of the others in one or more of x, y, and z directions to change the selected location in the volume.

74. The system of claim 43 or 44 further comprising a controller configured to control the position of at least one, and preferably all, of the first excitation light, the second excitation light, and the third excitation light relative to the position of the container.

75. The system of claim 43 or 44 further comprising a controller configured to selectively operate at least one, and preferably all, of generation and direction of the first, second, and / or third excitation lights into the container and controlling the translation mechanism and position of any one or more system components moved thereby.

76. The system of claim 43 or 44 further comprising a camera or detector for monitoring the hardening of the photohardenable composition.

77. The system of claim 43 or 44 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.

78. A printhead module for use in forming an object, the printhead module comprising a combination including: a. first optics for directing a first excitation light comprising a first light sheet including a first wavelength along a first light path to a first position in a container for including the volume including a photohardenable composition; b. second optics for directing a second excitation light comprising a second optical image including a second wavelength along a second light path to the first position in the container; wherein the first optics and second optics are configured or configurable to direct the first and second light paths to intersect at the first position; and c. third optics for directing a third excitation light comprising a second light sheet including a third wavelength along a third light path, the third optics being configuredor configurable such that the third light path and first light path are substantially parallel to each other within the container.

79. The printhead module of claim 78 wherein the second wavelength of light is longer than the first or third wavelength of light, and the first and third wavelength can be the same or different.

80. The printhead module of claim 78 or 79 wherein the optical image comprises a two dimensional optical image corresponding to a two dimensional slice of the object to be printed.

81. The printhead module of claim 78 wherein the first and second optics are configured or configurable for the first and second excitation lights intersect at an angle of about 90 degrees in the photohardenable composition.

82. The printhead module of claim 78 wherein the first and second excitation lights intersect at an angle less than about 90 degrees in the photohardenable composition83. The printhead module of claim 78 wherein the third light path for an illuminated second light sheet does not to cross or intersect with the first light path for an illuminated first light sheet and the second light paths for an illuminated optical image in the volume of photohardenable composition during printing.

84. The printhead module of claim 78, wherein the printhead module further includes fourth optics for directing a third light sheet to the first position from a side of the container opposite the first optics, wherein the third light sheet is optionally generated by a third light sheet generating system or by reflecting the first light sheet exiting the container back along the first light path of the first sheet through the container.

85. The printhead module of claim 78 wherein the first wavelength is in a range from about 350 to about 460 nanometers.

86. The printhead module of claim 78 wherein the wavelength of the second excitation light is in a range from about 460 to 850 nanometers.

87. The printhead module of claim 78 wherein the wavelength of the third excitation light is in a range from about 350 to 500 nanometers.

88. The printhead module of claim 78 further including a stationary diffuser through which the second light sheet is passed for altering the width or angular diversity of the second light sheet.

89. The printhead module of claim 78 further including a moving diffuser through which the second light sheet is passed for altering the width or angular diversity of the second light sheet.

90. The printhead module of claim 78 further including a stationary microlens array through which the second light sheet is passed for altering the width or angular diversity of the second light sheet.

91. The printhead module of claim 78 further including a moving microlens array through which the second light sheet is passed for altering the width or angular diversity of the second light sheet.

92. The printhead module of claim 78 further including a lens through which the second light sheet is passed to produce light with a numerical aperture along the width of the second light sheet at least twice that of the numerical aperture along the width of the first excitation light.

93. The printhead module of claim 78 further including an axicon lens through which the second light sheet is passed for altering the width or angular diversity of the second light sheet.

94. The printhead module of claim 78 wherein the first, second and third light excitations are all fixed relative to each other.

95. The printhead module of claim 78 wherein the light paths of the first and third excitation lights are approximately parallel in the photohardenable composition.

96. The printhead module of claim 78 wherein any of the first, second or third excitation lights are directed through an optical alignment element or elements that modifies the angle they travel upon entering the photohardenable composition relative to the angle they would travel in the photohardenable composition in the absence of the optical alignment element or elements.

97. The printhead module of claim 78 further comprising a controller configured to at least one, and preferably all, of the first excitation light, the second excitation light, and the third excitation light and relative movement of the container and the excitation lights.

98. The printhead module of claim 78 further comprising a camera or detector for monitoring the hardening of the photohardenable composition.

99. The method of claim 1 or 2 wherein a repeated set of steps further includes moving one or more of the container, the first, second, and / or third excitation lights to position the location of the altered region for exposure to the third excitation light.

100. The method of claim 3 or 4 further comprising repositioning the container and / or third excitation relative to each other such that the first position at which of the first and second excitation lights intersected is repositioned to intersect with the third excitation light.

101. The method of claim 3 or 4 wherein a repeated set of steps further includes moving one or more of the container, the first, second, and / or third excitation lights to reposition the location of the initial patterning for exposure to the third excitation light.

102. The method of claim 11, wherein the optical image of a repeated step includes a subsequent slice of the object to be printed.

103. The method of claim 7 wherein the wavelength of the first excitation light is in a range from about 350 to 460 nanometers.

104. The method of claim 7, wherein the wavelength of the second excitation light is in a range from about 460 to 850 nanometers.

105. The method of claim 7, wherein the wavelength of the third excitation light is in a range from about 350 to 500 nanometers.

106. The method of claim 28 wherein formation of the second light sheet further includes passing the as-generated second light sheet through an axicon lens.

107. The method of claim 29 wherein formation of the second light sheet further includes passing the as-generated second light sheet through an axicon lens.

108. The method of any one of claims 1-4 wherein the second excitation light is passed through an aperture positioned between the second optical system and the container.

109. The system of claim 43 or 44 further comprising an aperture positioned between the second optical system and the container.

110. The system of claim 43 or 44 wherein the container include a one or more coatings or surface treatments to reduce back-reflections of the excitation lights directed into the printing resin during printing.

111. The system of claims 43 or 44 wherein the system is configured or configurable for the third excitation light to intersect with the first position after the intersection of the first and second excitation lights at the first position and after repositioning the container and / or third excitation relative to each other such that the first position at which of the first and second excitation lights intersected is repositioned to intersect with the third excitation light.

112. The method of claim 2 or 4 wherein the method includes one or more of following features (i) - (v):(i) the container is at an angle with respect to the direction in which the optical image is directed into the volume that is selected such that the optical image has a focal plane that fully lies within the printing resin;(ii) the first light sheet is at an angle with respect to the light path of the optical image projection that is selected to be an angle that results in the first light sheet being at the same angle as the optical image focal plane in the resin;(iii) each of the first light sheet and the optical image projection has a dimension along the direction of motion of the container relative to the optical image projection and first light sheet , and the distance from the mid-point of the two dimensions is selected for achieving a colinear or substantially colinear overlap of the light sheet and optical image projection in the printing resin;(iv) each of the first light sheet and the second light sheet has a dimension along the direction of motion of the container relative to the first light sheet, and the second light sheet, and the distance from the mid-point of the two dimensions is selected for avoiding overlap of back-reflection from the second light sheet and / or the first light sheet with light curtain with the first light sheet and / or the optical image projection;(v) a dimension of the printing resin in the container along the direction of relative movement between the container and the optical image / light sheet / light curtain) is selected to be large enough to accommodate printing a full size object.

113. The system of claim 44 wherein the system includes one or more of following features (i) - (v):(i) the container is at an angle with respect to the direction in which the optical image is directed into the volume that is selected such that the optical image has a focal plane that fully lies within the printing resin;(ii) the first light sheet is at an angle with respect to the light path of the optical image projection that is selected to be an angle that results in the first light sheet being at the same angle as the optical image focal plane in the resin;(iii) each of the first light sheet and the optical image projection has a dimension along the direction of motion of the container relative to the optical image projection and first light sheet , and the distance from the mid-point of the two dimensions is selected for achieving a colinear or substantially colinear overlap of the light sheet and optical image projection in the printing resin;(iv) each of the first light sheet and the second light sheet has a dimension along the direction of motion of the container relative to the first light sheet, and the second light sheet, and the distance from the mid-point of the two dimensions is selected for avoiding overlap of back-reflection from the second light sheet and / or the first light sheet with light curtain with the first light sheet and / or the optical image projection;(v) a dimension of the printing resin in the container along the direction of relative movement between the container and the optical image / light sheet / light curtain) is selected to be large enough to accommodate printing a full size object.

Images