Self-contained CT scintillator in 3D printing collimator

Abstract

The invention relates to a self-contained CT scintillator in a 3D printed collimator. A patient post collimator and a method of manufacturing a patient post collimator are provided. An example method includes: additively manufacturing a collimator array having a plurality of tapered cavities; positioning a plurality of scintillator pixels within the tapered cavities of the collimator array; and hardening the pixels within the tapered cavities. An example post-patient collimator includes: a collimator array including a plurality of cavities, where each cavity of the plurality of cavities includes a tapered wall; a scintillator, the scintillator comprising a plurality of pixels, each of the plurality of pixels being positioned with one of the plurality of cavities of the collimator; and a reflector positioned on top of each of the plurality of pixels.

Description

Technical Field

[0001] Embodiments of the subject matter disclosed herein relate to diagnostic medical imaging, and more particularly to a computed tomography imaging setup with a post-patient collimator. Background Art

[0002] X-ray radiation detectors, such as those used in CT imaging systems, include a patient post-collimator assembly having a collimator and a scintillator. Typically, existing patient post-collimator assemblies are separate components that can be attached to each other (e.g., a collimator positioned on top of a scintillator, or positioned between an X-ray radiation source and a scintillator). The patient post-collimator assembly can be coupled to a photodiode to acquire data associated with a patient or subject scanned using a CT imaging system, thereby achieving image reconstruction. Summary of the invention

[0003] In one embodiment, a post-patient collimator for x-ray radiation includes a collimator array including a plurality of cavities, wherein each of the plurality of cavities includes a tapered wall. The collimator array is additively manufactured. A scintillator includes a plurality of pixels, each pixel being positioned with one of the plurality of cavities of the collimator. A reflector is positioned on top of each of the plurality of pixels.

[0004] In another embodiment, a method of manufacturing a post-patient collimator for x-ray radiation includes: additively manufacturing a collimator array having a plurality of tapered cavities; positioning a plurality of scintillator pixels within the collimator array, wherein each of the plurality of scintillator pixels is positioned within one of the plurality of tapered cavities; and hardening the pixels within the tapered cavities.

[0005] It should be understood that the above brief description is provided to introduce in a simplified form selected concepts that are further described in the detailed description. It is not meant to identify key features or essential features of the claimed subject matter, the scope of which is uniquely defined by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The present invention will be better understood by reading the following description of non-limiting embodiments with reference to the accompanying drawings, in which:

[0007] Figure 1 A pictorial view of an imaging system according to one embodiment of the present invention is shown.

[0008] Figure 2 A block schematic diagram of an exemplary imaging system according to one embodiment of the present invention is shown.

[0009] FIG. 3 depicts a current version of a post-patient collimator assembly including a collimator and a scintillator.

[0010] FIG. 4A to FIG. 4G A process for manufacturing a post-patient collimator assembly as described herein is depicted.

[0011] Figure 5 Depicted FIG. 4A to FIG. 4G Cross-sectional view of an example post-patient collimator assembly depicted in FIG.

[0012] Figure 6 Depicted FIG. 4A to FIG. 5 Top view of the example patient post-collimator assembly depicted in FIG.

[0013] Figure 7 Depicted FIG. 4A to FIG. 6 Bottom view of an example post-patient collimator assembly depicted in FIG.

[0014] Figure 8 Is manufacturing FIG. 4A to FIG. 7 An example method of a post-patient collimator assembly is depicted in FIG. DETAILED DESCRIPTION

[0015] One or more specific embodiments will be described below. In order to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be understood that in the development of any such actual implementation, as in any engineering or design project, many implementation-specific decisions must be made to achieve the developer's specific goals, such as complying with system-related and business-related constraints that may vary from implementation to implementation. In addition, it should be understood that such development efforts may be complex and time-consuming, but are still routine tasks for design, fabrication, and manufacturing for ordinary technicians who benefit from this disclosure.

[0016] When introducing elements of various embodiments of the present subject matter, the articles "a," "an," "the," and "said" are intended to indicate that there are one or more elements. The terms "comprising," "including," and "having" are intended to be inclusive, and mean that there may be additional elements in addition to the listed elements. Furthermore, any numerical examples in the following discussion are intended to be non-limiting, and thus the additional numerical values, ranges, and percentages are within the scope of the disclosed embodiments.

[0017] Various embodiments related to x-ray imaging of a subject are described below. Specifically, systems and methods are provided for CT imaging using a post-patient collimator assembly that includes a collimator and a scintillator. Figure 1 to Figure 2An example embodiment of an imaging system is shown that includes a post-patient collimator assembly positioned between a patient or subject and a detector. FIG3 depicts an example of a prior art post-patient collimator assembly, wherein the collimator is positioned between an X-ray source and a scintillator. Specifically, the collimator is stacked on a top surface of the scintillator. FIG. 4A to FIG. 4G An example manufacturing process for a collimator assembly described herein in which a collimator and a scintillator are integrated is depicted. Figures 5 to 7 An example post-patient collimator assembly described herein is depicted that can be used with FIG. 4A to FIG. 4G The manufacturing process described in is used to manufacture. Figure 8 It is a depiction of manufacturing Figures 5 to 7 Flowchart of an example method of a post-patient collimator.

[0018] Although a CT system is described by way of example, it should be understood that the techniques of the present invention may also be useful when applied to images acquired using other imaging modalities, such as tomosynthesis, C-arm angiography, etc. The present discussion of the CT imaging modality is provided merely as an example of one suitable imaging modality.

[0019] Various embodiments may be implemented in conjunction with different types of imaging systems. For example, various embodiments may be implemented in conjunction with a CT imaging system in which a radiation source projects a fan or cone beam that is collimated to lie in the xy plane of a Cartesian coordinate system and is generally referred to as an "imaging plane." The x-ray beam passes through an imaging subject, such as a patient. The beam, after being attenuated by the imaging subject, impinges upon an array of radiation detectors. The intensity of the attenuated radiation beam received at the detector array depends on the attenuation of the x-ray beam by the imaging subject. Each detector element of the array produces a separate electrical signal that is a measure of the beam intensity at the detector location. Intensity measurements from all detectors are collected individually to produce a transmission distribution.

[0020] In third generation CT systems, the radiation source and detector array are rotated in an imaging plane around an object to be imaged (such as a region of a subject) using a gantry so that the angle at which the x-ray beam intersects the imaged subject is constantly changing. A full gantry rotation occurs when the gantry completes a full 360 degree rotation. A set of x-ray attenuation measurements (e.g., projection data) from the detector array at one gantry angle is called a "view." Thus, a view is each incremental position of the gantry. A "scan" of an object includes a set of views made at different gantry angles or viewing angles during one rotation of the x-ray source and detector.

[0021] In an axial diagnostic scan, the projection data is processed to construct images corresponding to two-dimensional slices taken through the imaged subject. A scout scan (also referred to herein as a scout scan) provides projection views along the longitudinal axis of the imaged subject and typically provides aggregates, each of which includes the internal structures of the subject. A method for reconstructing an image from a set of projection data is known in the art as a filtered backprojection technique. The method converts attenuation measurements from the scan into integers known as "CT numbers" or "Houëtsberg units" (HU), which are used to control the brightness of corresponding pixels on a display.

[0022] Figure 1 An exemplary computed tomography (CT) imaging system 10 is illustrated, and Figure 2 An exemplary block diagram of an exemplary imaging system according to an embodiment of the present invention is depicted. The CT imaging system includes a gantry 12. The gantry 12 has an X-ray source 14 that generates and projects a beam of X-rays 16 toward a detector assembly 15 on the opposite side of the gantry 12. The X-ray source 14 projects the beam of X-rays 16 through a pre-patient collimator assembly 13, which uses, for example, one or more filters to determine the size and shape of the beam of X-rays 16. The detector assembly 15 includes a collimator assembly 18 (post-patient collimator assembly), a plurality of detector modules 20 (e.g., detector elements or sensors), and a data acquisition system (DAS) 32. The plurality of detector modules 20 detects the projected X-rays that pass through an imaged subject or object 22, and the DAS 32 converts the data into digital signals for subsequent processing. Each detector module 20 in a conventional system generates an analog electrical signal that represents the intensity of the incident X-ray beam and, therefore, the intensity of the beam that is attenuated when the incident X-ray beam passes through the subject or object 22. During a scan to acquire x-ray projection data, the gantry 12 and components mounted thereon are rotated about a center of rotation 25 (eg, isocenter) to collect attenuation data from multiple viewing angles relative to the imaging volume.

[0023] The rotation of the gantry 12 and the operation of the X-ray source 14 are controlled by a control system 26 of the CT imaging system 10. The control system 26 includes: an X-ray controller 28, which provides power and timing signals to the X-ray source 14; a collimator controller 29, which controls the aperture length and width of the pre-patient collimator 13 (and therefore, the size and shape of the X-rays (e.g., X-ray beam) 16); and a gantry motor controller 30, which controls the rotation speed and position of the gantry 12. An image reconstructor 34 receives sampled and digitized X-ray data from the DAS 32 and performs high-speed image reconstruction. The reconstructed image is applied as input to a computer 36, which stores the image in a storage device 38. The computer 36 also receives commands and scanning parameters from an operator via a console 40. An associated display 42 allows the operator to observe the reconstructed image and other data from the computer 36. The computer 36 uses the commands and parameters provided by the operator to provide control signals and information to the DAS 32, the x-ray controller 28, the collimator controller 29, and the gantry motor controller 30. In addition, the computer 36 operates a table motor controller 44, which controls a motorized table 46 to position the subject 22 and the gantry 12. Specifically, the table 46 moves portions of the subject 22 through a gantry opening or aperture 48.

[0024] FIG. 3 depicts a current version of a post-patient collimator assembly 300 including a collimator 302 and a scintillator 304. The example current post-patient collimator assembly 300 includes a collimator 302 comprised of a plurality of collimator plates 306. The example plates may be made of tungsten. Alternatively, another radiation blocking material may be used. The collimator plates 306 are depicted as being positioned at a plurality of angles such that a row of the plurality of tungsten plates forms a curved collimator 302 corresponding to the curve of, for example, the gantry of the CT imaging system 10, which enables each beam 16 of X-ray radiation to travel approximately the same distance from the X-ray source 14 to the collimator 302. In an alternative example such as used in a standard X-ray detector, the collimator plates 306 may be positioned parallel to one another such that the plurality of collimator plates 306 form a row perpendicular to the X-ray source 14.

[0025] The example post-patient collimator assembly 300 of FIG. 3 also includes a scintillator 304. The example scintillator 304 includes a plurality of scintillator elements or pixels 308 arranged so that each scintillator element 308 is positioned between two collimator plates in a plurality of collimator plates 306 in the collimator 302. The scintillator elements or pixels 308 may be made of a ceramic material. In the illustrated example, the scintillator elements 308 are at least partially encapsulated in an epoxy 310 to hold the scintillator elements or pixels 308 in place. The scintillator elements or pixels 308 are positioned parallel to each other, thereby forming straight rows in the scintillator 302. In the illustrated example, the epoxy 310 covers the top and sides of each scintillator element or pixel 308.

[0026] Optical couplers 312 and photodiodes 314 are attached to the bottom surface of the plurality of scintillator elements 308. The example optical couplers 312 may operate as light collimators to improve the light collection efficiency of the photodiodes 314. The optical couplers 312 may be attached to the scintillator elements 308 via adhesive and / or epoxy 310. The example photodiodes 314 receive light energy from the scintillator 302 via the optical couplers 312 and generate corresponding electrical signals. The electrical signals are then provided to the DAS 32 for image reconstruction.

[0027] FIG. 4A to FIG. 4G A process for manufacturing a post-patient collimator assembly 400 as described herein is depicted. The manufacturing process of the example collimator assembly begins with the production of a scintillator pixel or element 402. The example compact pixel or element 402 can be in the form of a compact powder of, for example, a ceramic material. The compact powder can be compressed into a truncated cone shape or a truncated pyramid shape to form a single pixel element or pixel 402. In some examples, the compact powder pixel or element 402 can be manufactured in a mold or using a press. In an alternative example, the scintillator pixel or element 402 is produced from a ceramic powder and / or a resin powder using additive manufacturing (e.g., 3D printing).

[0028] Additionally, the manufacturing process of the example collimator includes the production of an additively manufactured collimator array 404. The example collimator array 404 includes a plurality of cavities or holes 406 having a truncated cone shape or a truncated pyramid shape corresponding to the shape of the example scintillator elements or pixels 402. The shape of the cavity 406 results in the formation of a conical cavity in the collimator array 404. The example collimator array 404 is made of tungsten. Alternatively, other materials capable of blocking X-ray radiation may be used instead. The example collimator array 404 is preferably additively manufactured (e.g., 3D printed), however, any sufficient means of producing the example collimator array 404 may be used. In some examples, the example collimator array 404 and the scintillator pixels 402 may be additively manufactured in series, either individually or together (i.e., each pixel is additively manufactured in a corresponding cavity at the same time as the additive manufacturing of the collimator array). The frustoconical or truncated pyramidal shapes of the example pixels 402 and cavities 406 of the collimator array 404 increase the focusing of the X-ray radiation beam to provide optimized collimation (ie, the cavities 406 and / or pixels 402 of the collimator assembly are in focus).

[0029] Figure 4C The process of inserting one of the example scintillator pixels 402 into one of the cavities 406 of the scintillator array 404 is depicted. If the example scintillator pixel 402 is manufactured separately (i.e., not as an integral component), the process of inserting the example scintillator pixel 402 into the cavity 406 of the collimator array 404 occurs. In examples where the scintillator pixel 402 and the collimator array 404 are additively manufactured (e.g., using a 3D printer capable of printing with multiple materials simultaneously) as a single piece or integral component, Figure 4C The process depicted in is not required. Alternatively, in some example manufacturing methods, the process of inserting the exemplary pixel 402 includes pouring a liquid ceramic material into the formed cavity 406 of the collimator array 404. In such examples, the manufacturing process does not include a step of forming the pixel, but rather includes a step of mixing the liquid ceramic material.

[0030] Figure 4D Depicted is a process of melting or hardening the ceramic and / or resin powder of the example scintillator pixel 402 using a sintering process or hot isostatic pressing. Melting or hardening the scintillator pixel 402 in place within the cavity 406 of the collimator array forms an inseparable component (the inseparable component includes both the collimator and the scintillator that are intermeshed in a single component rather than stacked on top of each other), such as the prior art post-collimator assembly depicted in FIG.

[0031] Figure 4EDepicted is the process of grinding the bottom layer 408 of the collimator assembly 404 to expose the bottom 410 of the scintillator pixel 402, thereby allowing X-ray radiation to fully pass through the pixel 402. The bottom layer 408 of the collimator array may be ground using any means sufficient to grind the tungsten material of the collimator array 404.

[0032] Figure 4F The addition of a reflective material or coating 412 added to the top surface 414 of the scintillator pixel 402 is depicted. The reflective material allows light to pass through in a first direction (e.g., downward through the pixel 402) while preventing light from passing through in a second direction (e.g., upward away from the pixel 402). The reflective material helps focus light emitted by the pixel 402 from the bottom surface 410. In some examples, the reflective material can be a film adhered to the top surface 414 of the pixel 402. In some examples, the reflective material is a plate adhered to the top surface 414 of the pixel. In some examples, the reflective material is an epoxy filled with a reflective pigment (e.g., a reflective epoxy).

[0033] Figure 4G The last step of manufacturing the example post-patient collimator assembly 400 described herein is depicted. In the example last step, the photodiode 416 is attached to the bottom surface of the pixel 402 and the bottom surface 418 of the ground collimator array 404. In some examples, the optical coupler 417 can be positioned between the bottom surface 418 and the photodiode 416. The example photodiode 416 can be attached via an adhesive, epoxy, or other suitable means. Manufacturing the post-patient collimator assembly 400 in this manner reduces alignment errors that typically occur when scintillator pixels are positioned adjacent to a scintillator array, as shown in FIG3. Therefore, the manufacturing process produces a more efficient post-patient collimator assembly 400.

[0034] Figure 5 Depicted FIG. 4A to FIG. 4G A cross-sectional side view of an example post-patient collimator assembly 400 is depicted in FIG. Figure 6 depicts a top view of an example post-patient collimator assembly 400, and Figure 7 A bottom view of an example post-patient collimator assembly 400 is depicted. Figure 5 As depicted in FIG, the multiple conical or pyramidal cavities 406 are not only truncated cone or truncated pyramid shapes, but also the walls 502 extending between the cavities can be tilted at various angles to help focus the X-ray beam. For example, the wall 502 that is closer to the center of the post-patient collimator assembly 400 can be positioned at an angle substantially perpendicular to the photodiode 416 (e.g., 90 degrees). The wall 502 that is positioned closer to the edge 504 of the post-patient collimator assembly 400 can be positioned at a certain angle, and the farther the wall 502 is positioned from the center, the further away from perpendicular (e.g., less than 90 degrees, greater than 90 degrees). Although Figure 5A cross-section of a post-patient collimator assembly 400 including six pixels 402 is depicted, but any number of pixels may be used in the post-patient collimator assembly 400. Furthermore, the example CT imaging system 10 may include one or more of the example post-patient collimator assemblies 400 arranged adjacent to one another in rows, columns, and / or a plurality of rows and columns to form a detector array.

[0035] Figure 6 and Figure 7 A top view and a bottom view, respectively, of an example post-patient collimator assembly 400 are depicted. The top view and the bottom view each depict a grid-like arrangement of pixels 402 within a cavity 402. In the illustrated example, a grid including nine pixels 402 is depicted, but the example post-patient collimator assembly 40 may include a different number of pixels, depending on the size of the CT imaging system, the desired size of the detector, the number of other post-patient collimator assemblies 402 that are combined to form the detector, and / or manufacturing constraints on the size of a post-patient collimator assembly that can be produced using the example methods described herein.

[0036] like Figure 6 As shown in the top view of the post-patient collimator assembly, the top surface 602 of the example pixel 402 and / or reflective material is smaller than the opening 604 of the cavity 406. Figure 7 The bottom surface of the example post-collimator assembly 702 is depicted without the attached photodiode 416. The bottom surface of the pixel 402 is exposed. Figure 6 and Figure 7 Cavity 406 and pixel 402 are depicted as having a truncated pyramid shape, as shown by a square top surface 602, opening 604, and bottom surface 606. Alternatively, when pixel 402 and cavity 406 are truncated cone shapes, the top surface, opening, and bottom surface may have a circular shape.

[0037] Figure 8 Is manufacturing FIG. 4A to FIG. 7800 for a post-patient collimator depicted in . The example method 800 begins with producing a collimator having a tapered cavity or aperture using a process such as additive manufacturing (step 802). As discussed above, the tapered opening may have a tapered cone shape or a tapered pyramid shape. In step 804, a pixel is produced from a powdered resin or ceramic material. The example pixel has a shape corresponding to the shape of the cavity of the collimator. In some examples, the pixel is produced in series with the example collimator (alone or as a single-piece component) using an additive manufacturing process. In some examples, method 800 continues in step 806 by positioning the pixel within the cavity. Step 806 is only required when the pixel is produced separately from the collimator. The pixel is then hardened or melted within the cavity in step 808. Step 808 may include sintering, hot isostatic pressing, or any other suitable means of melting or hardening the material of the pixel in the cavity. The method continues with step 810, which includes grinding away the bottom layer of the collimator to expose the bottom of the pixel, which can be done using any means capable of grinding the material of the collimator. Finally, a reflective coating is added to the top surface of the pixel. The reflective coating can be applied using an adhesive, or can be an epoxy with reflective pigments that harden in the top surface of the pixel (step 812). Additionally, in some examples, the method may include the step of adhering the photodiode to the bottom surface using, for example, an adhesive or any other suitable means of adhering the photodiode to the scintillator and collimator (step 814). The method 800 is completed.

[0038] Figures 1 to 7An example configuration with relative positioning of each component is shown. In at least one example, if it is shown as being in direct contact or directly coupled to each other, such elements may be referred to as being in direct contact or directly coupled, respectively. Similarly, in at least one example, the elements shown as being adjacent or adjacent to each other may be adjacent or adjacent to each other, respectively. For example, components placed in coplanar contact with each other may be referred to as being in coplanar contact. For another example, in at least one example, elements positioned to be spaced apart from each other and having only space therebetween without other components may be described and referenced as such. For another example, elements shown as being located above / below each other, located on opposite sides of each other, or located on the left / right side of each other may be described and referenced as such relative to each other. In addition, as shown in the figure, in at least one example, the topmost element or the point of the element may be referred to as the "top" of the component, and the bottommost element or the point of the element may be referred to as the "bottom" of the component. As used herein, top / bottom, upper / lower, upper / lower may be relative to the vertical axis of the figure, and may be used to describe the position of the elements relative to each other in the figure. Thus, in one example, the element shown as being located above other elements is positioned vertically above other elements. For another example, the shapes of elements depicted in the figures may be referred to as having those shapes (e.g., such as being rounded, straight, planar, curved, rounded, chamfered, angled, etc.). Furthermore, in at least one example, elements shown as intersecting each other may be referred to as intersecting elements or intersecting each other. Additionally, in one example, elements shown as being within another element or shown as being outside another element may be described and referred to as such.

[0039] As used herein, the elements or steps listed in the singular and beginning with the word "one" or "a kind of" should be understood as not excluding a plurality of said elements or steps, unless such exclusion is explicitly stated. In addition, the reference to "an embodiment" of the present invention is not intended to be interpreted as excluding the existence of additional embodiments that also include the cited features. In addition, unless explicitly stated to the contrary, the embodiment of "including", "comprising" or "having" an element or multiple elements with a specific characteristic may include additional such elements without the characteristic. The terms "including" and "in..." are used as the concise language equivalents of the corresponding terms "including" and "wherein". In addition, the terms "first", "second" and "third" etc. are only used as marks, and are not intended to impose numerical requirements or specific positional order on their objects.

[0040] This written description uses examples to disclose the invention, including the best mode, and also to enable a person skilled in the relevant art to practice the invention, including making and using any devices or systems and performing any included methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to a person skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insignificant differences from the literal language of the claims.

Claims

1. A method for manufacturing a collimator, the method comprising: Additive manufacturing of collimator arrays with multiple tapered cavities; positioning a plurality of scintillator pixels within the collimator array, wherein each scintillator pixel of the plurality of scintillator pixels is positioned within one of the tapered cavities; as well as The plurality of scintillator pixels are hardened within the tapered cavity.

2. The method of claim 1 further comprising using additive manufacturing to produce the compact pixels. 3 . The method of claim 1 , wherein positioning a plurality of pixels within the collimator array comprises additively manufacturing each of the scintillator pixels within each of the plurality of tapered cavities. 4 . The method of claim 1 , further comprising grinding a bottom layer of the collimator array to expose a bottom surface of the scintillator pixels. 5 . The method of claim 1 , further comprising applying a reflective coating to a top layer of each of the scintillator pixels.

6. The method of claim 5, wherein the reflective coating is a reflective or pigment-filled epoxy. 7 . The method of claim 5 , wherein the reflective coating is adhered to the top layer of each of the scintillator pixels.

8. The method of claim 1, wherein the collimator array is additively manufactured using tungsten.

9. The method of claim 1, wherein each scintillator pixel is a compact powdered ceramic material.

10. The method of claim 1, wherein each scintillator pixel is additively manufactured using a ceramic material.

11. The method of claim 1 , wherein positioning the plurality of scintillator pixels comprises pouring a liquid ceramic material into the plurality of tapered cavities.

12. The method of claim 1, wherein hardening the plurality of scintillator pixels comprises sintering.

13. The method of claim 1, wherein hardening the plurality of scintillator pixels comprises hot isostatic pressing.

14. A collimator for X-ray radiation, the collimator comprising: a collimator array comprising a plurality of cavities, wherein each cavity of the plurality of cavities comprises a tapered wall, and wherein the collimator array is additively manufactured; a scintillator comprising a plurality of pixels, each pixel of the plurality of pixels being positioned with one of the plurality of cavities of the collimator array; and A reflector is positioned on top of each pixel in the plurality of pixels.

15. The collimator of claim 14, wherein the collimator array is additively manufactured using tungsten.

16. The collimator of claim 14, wherein the plurality of pixels are additively manufactured using ceramics.

17. The collimator of claim 14, wherein the tapered wall of each cavity of the plurality of cavities forms a frusto-conical cavity in which each pixel is positioned.

18. The collimator of claim 14, wherein the tapered walls of the plurality of cavities are in-focus.

19. The collimator of claim 14, wherein the reflector is a reflective or pigment filled epoxy.

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