Lighting system for an augmented reality metrology tool

Abstract

The embodiments described herein provide a light engine for a measurement system and a method for using the light engine. The measurement system includes a light engine operable to illuminate a first grating of an optical device. The light engine projects a pattern using light from the light engine. The light engine projects the pattern onto the first grating so that a metrology metric can be extracted from one or more images captured by a detector of the measurement system. The metrology metric is extracted by processing the images. The metrology metric determines whether the optical device meets an image quality standard.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure generally relate to optical devices for augmented, virtual, and mixed reality. More particularly, embodiments described herein provide optical engines for measurement systems and methods of using optical engines. [Background technology]

[0002] Virtual reality is generally considered to be a computer-generated simulated environment in which the user has a distinct physical presence. Virtual reality experiences can be generated in 3D and can be viewed using a head-mounted display (HMD), such as glasses, or other wearable display devices that have near-eye display panels as lenses to display a virtual reality environment that replaces the real environment.

[0003] Augmented reality, however, allows for the experience of a user still looking through the display lenses of glasses or other HMD devices to observe the surrounding environment, while simultaneously viewing images of virtual objects that are generated to display and appear as part of the environment. Augmented reality can include audio and tactile input, as well as any type of input, such as virtual images, graphics, and video, that enhance or extend the environment the user experiences. As a state-of-the-art technology, there are many challenges and design constraints associated with augmented reality.

[0004] One such challenge is measuring optical devices for image quality standards. Metrology metrics of manufactured optical devices must be obtained to ensure that image quality standards are met. However, existing measurement systems lack a desirable field of view and suffer from ghost imaging problems. Therefore, there is a need in the art for a measurement system with an improved field of view and reduced occurrence of ghost imaging, and a method for using such a measurement system. Summary of the Invention

[0005] In one embodiment, a measurement system is provided. The measurement system includes a stage operable to hold an optical device or an optical device substrate having at least one optical device disposed thereon. The measurement system further includes a light engine disposed above the stage. The light engine includes a plurality of light sources. The plurality of light sources are operable to project light of a range of wavelengths onto the optical device. The light engine further includes a first lens operable to collimate light from each of the plurality of light sources. The light engine further includes a reticle tray disposed below the plurality of light sources. The reticle tray has a plurality of reticles disposed thereon. Each of the plurality of reticles has a pattern that is projected when light is directed onto each of the plurality of reticles. The light engine further includes a second lens operable to receive the pattern projected from each of the plurality of reticles. The second lens is operable to project the pattern onto an input coupling grating of the optical device.

[0006] In another embodiment, a measurement system is provided. The measurement system includes a stage operable to hold an optical device or an optical device substrate having at least one optical device disposed thereon. The measurement system further includes a light engine disposed above the stage. The light engine includes a module operable to project one or more patterns onto the optical device. The light engine is operable to rotate and / or tilt to adjust the angle of incidence of the pattern projected onto the optical device or the optical device substrate. The measurement system further includes an alignment camera adjacent to the light engine. The alignment camera is positioned to capture one or more images of one or more alignment markers on the optical device or the optical device substrate. The measurement system further includes a reflective detector adjacent to the light engine. The reflective detector is positioned to detect the outcoupled beam projected from the optical device.

[0007] In yet another embodiment, a method is provided. The method includes projecting a pattern. The pattern is projected using light from a light engine. The light engine is disposed within a measurement system. The measurement system includes a stage disposed below the light engine. The measurement system further includes a tray disposed above the stage. The tray includes an optical device or an optical device substrate having at least one optical device disposed thereon, the optical device being operable to receive the pattern. The measurement system further includes a reflective detector oriented toward the stage. The method further includes detecting one or more images of the pattern. The images are detected when the pattern is outcoupled into the reflective detector through total internal reflection via the optical device. The method further includes processing the images to extract a metrology metric.

[0008] Thus, in order that the above-described features of the present disclosure may be understood in detail, a more particular description of the present disclosure briefly summarized above will in some cases refer to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings depict merely exemplary embodiments and therefore should not be considered as limiting the scope of the present disclosure, which may admit of other equally effective embodiments. [Brief explanation of the drawings]

[0009] [Figure 1A] FIG. 2 is a front perspective view of a substrate according to embodiments described herein. [Figure 1B] 1 is a front perspective view of an optical device according to an embodiment described herein. [Figure 2] 1 is a schematic cross-sectional view of a measurement system according to an embodiment described herein. [Figure 3A] 1 is a schematic diagram of a configuration of a light engine of a measurement system according to embodiments described herein. [Figure 3B] 1 is a schematic diagram of a configuration of a light engine of a measurement system according to embodiments described herein. [Figure 3C] 1 is a schematic diagram of a configuration of a light engine of a measurement system according to embodiments described herein. [Figure 3D] 1 is a schematic diagram of a configuration of a light engine of a measurement system according to embodiments described herein. [Figure 3E] 1 is a schematic diagram of a configuration of a light engine of a measurement system according to embodiments described herein. [Figure 4] 1 is a schematic diagram of an alignment camera configuration of a measurement system according to embodiments described herein. [Figure 5] 1 is a flow diagram of a method of optical device metrology according to embodiments described herein. DETAILED DESCRIPTION OF THE INVENTION

[0010] For ease of understanding, where possible, identical reference numerals have been used to indicate identical elements common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

[0011] Embodiments of the present disclosure generally relate to optical devices for augmented, virtual, and mixed reality. More specifically, embodiments described herein provide a light engine for a measurement system and a method for using the light engine. The measurement system includes a stage operable to hold an optical device or an optical device substrate having at least one optical device disposed thereon. The measurement system further includes a light engine disposed above the stage. The light engine includes a plurality of light sources. The plurality of light sources are operable to project light of a range of wavelengths onto the optical device. The light engine further includes a first lens operable to collimate light from each of the plurality of light sources. The light engine further includes a reticle tray disposed below the plurality of light sources. The reticle tray has a plurality of reticles disposed thereon. Each of the plurality of reticles has a pattern that is projected when light is directed onto each of the plurality of reticles. The light engine further includes a second lens operable to receive the pattern projected from each of the plurality of reticles. The second lens is operable to project the pattern onto an input coupling grid of the optical device. The light engine may also include a module for projecting a pattern.

[0012] A method of using a light engine includes projecting a pattern using light from the light engine. The method further includes detecting one or more images of the pattern. The images are detected when the pattern is totally internally reflected via an optical device and outcoupled to a reflectance detector. The method further includes processing the images to extract a metrology metric.

[0013] 1A is a front perspective view of a substrate 101 according to embodiments described herein. The substrate includes a plurality of optical devices 100 disposed on a surface 103 of the substrate 101. In some embodiments that can be combined with other embodiments described herein, the optical devices 100 are waveguide combiners utilized for virtual, augmented, or mixed reality. In some embodiments that can be combined with other embodiments described herein, the optical devices 100 are planar optical devices, such as metasurfaces.

[0014] The substrate 101 may be any substrate used in the art and may be either opaque or transparent to the selected laser wavelength, depending on the intended use of the substrate 101. The substrate 101 may be made of, but is not limited to, silicon (Si), silicon dioxide (SiO), fused silica, quartz, silicon carbide (SiC), germanium (Ge), silicon germanium (SiGe), indium phosphide (InP), gallium arsenide (GaAs), gallium nitride (GaN), silicon nitride (SiN), or a sapphire-containing material. Furthermore, the substrate 101 may have a variable shape, thickness, and diameter. For example, the substrate 101 may have a diameter of about 150 mm to about 300 mm. The substrate 101 may have a circular, rectangular, or square shape. The substrate 101 may have a thickness between about 300 μm and about 1 mm. Although only nine optical devices 100 are shown on the substrate 101, any number of optical devices 100 may be disposed on the surface 103 of the substrate 101.

[0015] FIG. 1B is a front perspective view of optical device 100. It should be understood that optical device 100 described herein is an exemplary optical device, and that other optical devices may be used with or modified to achieve aspects of the present disclosure. Optical device 100 includes a plurality of optical device structures 102 disposed on a surface 103 of a substrate 101. Optical device structures 102 may be nanostructures having sub-micron dimensions, e.g., nano-sized dimensions. Regions of optical device structures 102 correspond to one or more gratings 104, such as first grating 104a, second grating 104b, and third grating 104c. In one embodiment that can be combined with other embodiments described herein, optical device 100 includes at least first grating 104a corresponding to an input coupling grating and third grating 104c corresponding to an output coupling grating. In another embodiment that can be combined with other embodiments described herein, optical device 100 also includes second grating 104b corresponding to an intermediate grating. The optical device structures 102 can be angled or binary. The optical device structures 102 can have other cross sections, including, but not limited to, circular, triangular, elliptical, regular polygonal, polygonal, and / or irregular cross sections.

[0016] During operation, the first grating 104a receives an incident beam of light having a certain intensity from the light engine. In one embodiment, which can be combined with other embodiments described herein, the light engine is a microdisplay. The incident beam is split by the optical device structure 102 into a T1 beam having all of the intensity of the incident beam to direct a virtual image to the intermediate grating (if utilized) or the third grating 104c. In one embodiment, which can be combined with other embodiments described herein, the T1 beam undergoes total internal reflection (TIR) ​​through the optical device 100 until it contacts the intermediate grating optical device structure 102. The intermediate grating optical device structure 102 diffracts the T1 beam into a T-1 beam, which TIRs through the optical device 100 to the third grating 104c optical device structure 102. The third grating 104c optical device structure 102 outcouples the T-1 beam into the user's eye. The outcoupled T-1 beam to the user's eye displays the virtual image generated from the light engine from the user's viewpoint, further increasing the viewing angle from which the user can observe the virtual image. In another embodiment, which can be combined with other embodiments described herein, the T1 beam is totally internally reflected (TIR) ​​through the optical device 100 until the T1 beam contacts the optical device structure 102 of the third grating 104c, where it is outcoupled to display the virtual image generated from the light engine.

[0017] To ensure that the optical device 100 meets image quality standards, metrology metrics must be acquired for the manufactured optical device 100. The metrology metrics of each individual optical device 100 are tested to ensure that predetermined values ​​are achieved. The embodiments of the measurement system 200 described herein provide the ability to acquire multiple metrology metrics with high throughput. The metrology metrics include one or more of an angular uniformity metric, a contrast metric, an efficiency metric, a color uniformity metric, a modulation transfer function (MTF) metric, a field of view (FOV) metric, a ghost image metric, and an eyebox metric.

[0018] 2 is a schematic cross-sectional view of a measurement system 200 according to embodiments described herein. The measurement system 200 includes a body 201 having a first opening 203 and a second opening 205 through which a stage 207 can be moved. The stage 207 is operable to move in the X, Y, and Z directions within the body 201 of the measurement system 200. The stage 207 includes a tray 209 that can be operable to hold the optical device 100 (as shown herein) or to hold one or more substrates 101 upon which the optical device 100 is disposed.

[0019] Measurement system 200 may be operable to acquire one or more metrology metrics including one or more of an angular uniformity metric, a contrast metric, an efficiency metric, a color uniformity metric, an MTF metric, an FOV metric, a ghost image metric, or an eyebox metric. Stage 207 and tray 209 may be transparent such that the metrology metrics acquired by measurement system 200 are not affected by the translucency of stage 207 or tray 209. Measurement system 200 is in communication with controller 220. Controller 220 may be operable to facilitate operation of measurement system 200.

[0020] Measurement system 200 includes an upper portion 204 oriented toward a top side 222 of optical device 100 and a lower portion 206 oriented toward a bottom side 224 of optical device 100. Top portion 204 of measurement system 200 includes an alignment camera 208, a light engine 210, and a reflectance detector 212. Alignment camera 208 is operable to determine the position of stage 207. Alignment camera 208 is also operable to determine the position of optical device 100 disposed on stage 207. Alignment camera 208 includes an alignment camera body 211. Light engine 210 is operable to project light. For example, light engine 210 is operable to illuminate first grating 104a of optical device 100. Light engine 210 includes a light engine body 213. In one embodiment, which can be combined with other embodiments described herein, light engine 210 projects a pattern onto first grating 104a. A reflective detector 212 detects the outcoupled beam projected from the third grating 104c of the optical device 100. The outcoupled beam may be emitted from the top side 222 or the bottom side 224 of the optical device 100. The outcoupled beam may correspond to a pattern from the light engine 210. One or more images of the pattern are detected by the reflective detector 212. A controller 220 may be used to process the one or more images of the pattern to extract individual metrology metrics.

[0021] The lower portion 206 of the measurement system 200 includes a code reader 214 and a transmission detector 216. The code reader 214 and the transmission detector are disposed on the other side of the stage 207, opposite the alignment camera 208, the optical engine 210, and the reflection detector 212. The code reader 214 is operable to read a code on the optical device 100, such as a quick response (QR) code or a barcode on the optical device 100. The code read by the code reader 214 may include identification information and / or instructions for obtaining one or more metrology metrics of the optical device 100. The transmission detector 216 detects the outcoupled beam projected from the third grating 104c through a bottom side 224 of the optical device 100. In one embodiment, which can be combined with other embodiments described herein, the transmission detector 216 is coupled to a transmission detector stage 226. The transmission detector stage 226 is operable to move the transmission detector 216 in the X, Y, and Z directions. The transmission detector stage 226 is operable to adjust the position of the transmission detector 216 to enhance detection of the outcoupled beam projected from the third grating 104c.

[0022] In operation, a metrology metric is obtained by illuminating the first grating 104a of the optical device 100 using the light engine 210. The light engine 210 projects a pattern onto one or more optical devices 100. The incoupled light TIRs until the light is outcoupled (e.g., reflected or transmitted) from the optical device 100. The pattern is imaged as one or more images by the reflectance detector 212. The one or more images may correspond to a red channel, a green channel, and a blue channel. The one or more images may also correspond to one or more different metrology metrics. The one or more images are full-field images.

[0023] 3A is a schematic diagram of a first configuration 300A of light engine 210 of measurement system 200 according to embodiments described herein. First configuration 300A includes a first light source 302A, a second light source 302B, a third light source 302C, a first mirror 304A, a second mirror 304B, a first lens 306, a reticle tray 308, and a second lens 310. First light source 302A, second light source 302B, third light source 302C, first mirror 304A, second mirror 304B, first lens 306, reticle tray 308, and second lens 310 are disposed within light engine body 213.

[0024] The first light source 302A is operable to project a first light corresponding to a first wavelength or a first range of wavelengths. In one embodiment that can be combined with other embodiments described herein, the first light source 302A is a light emitting diode (LED). In another embodiment that can be combined with other embodiments described herein, the first wavelength or first range of wavelengths is 620 nm to 750 nm, which corresponds to red light. The first light is directed to a first lens 306.

[0025] The second light source 302B can be operated to project second light corresponding to a second wavelength or a second range of wavelengths. In one embodiment that can be combined with other embodiments described herein, the second light source 302B is an LED. In another embodiment that can be combined with other embodiments described herein, the second wavelength or second range of wavelengths is 495 nm to 570 nm, which corresponds to green light. The second light source 302B projects the second light onto the first mirror 304A. The first mirror 304A can be operated to direct the second light towards the first lens 306.

[0026] The third light source 302C can be operated to project third light corresponding to a third wavelength or a third range of wavelengths. In one embodiment that can be combined with other embodiments described herein, the third light source 302C is an LED. In another embodiment that can be combined with other embodiments described herein, the third wavelength or third range of wavelengths is 450 nm to 495 nm, which corresponds to blue light. The third light source 302C projects the third light onto the second mirror 304B. The second mirror 304B can be operated to direct the third light toward the first lens 306.

[0027] The first light source 302A, the second light source 302B, and the third light source 302C are not limited to the orientation and position shown in FIG. 3A . For example, the first light source 302A can be configured to project a first light onto the first mirror 304A or the second mirror 304B. In one embodiment, which can be combined with other embodiments described herein, the first light source 302A, the second light source 302B, and the third light source 302C are point or extended light sources. The first mirror 304A and the second mirror 304B can be operable to reflect any range of wavelengths projected toward the first mirror 304A and the second mirror 304B. The first mirror 304A and the second mirror 304B can be dichroic mirrors.

[0028] The first light, the second light, and the third light are directed to a first lens 306. In one embodiment that can be combined with other embodiments described herein, the first lens 306 is a collimation lens. The first lens 306 can operate to collimate light, such as the first light, the second light, or the third light, as it passes through the first lens 306. The first lens 306 collimates the light such that the light has an optical diameter of about 10 mm to about 50 mm. This optical diameter corresponds to the field of view of the measurement system 200. In some embodiments that can be combined with other embodiments described herein, the light sources 302A, 302B, and 302C are extended light sources positioned to direct light to the first lens 306 to reduce the spatial coherence of the illumination. In some embodiments that can be combined with other embodiments described herein, the first lens 306 is removed from the light engine 210 to improve throughput.

[0029] The reticle tray 308 contains reticles 322 (i.e., a first reticle 322A, a second reticle 322B, and a third reticle 322C). The first lens 306 collimates light toward the reticles 322 on the reticle tray 308. The first reticle 322A, the second reticle 322B, and the third reticle 322C can each include a pattern that is projected onto the first grating 104a of the optical device 100. The first reticle 322A, the second reticle 322B, and the third reticle 322C can each include a different pattern. The pattern is projected when one of the first light source 302A, the second light source 302B, and the third light source 302C projects light onto the reticle 322 so that the reticle 322 is illuminated. The pattern then illuminates the first grating 104a, which corresponds to the input coupling grating of the optical device 100. The reticle tray 308 is operable to move in one or more of the X, Y, and Z directions. Thus, the reticle tray 308 can be adjusted during operation of the methods described herein so that light is projected through one of the first reticle 322A, the second reticle 322B, and the third reticle 322C. The reticle tray 308 is adjusted in the Z direction to improve the quality of the projected pattern. For example, adjusting the reticle tray 308 in the Z direction can change the angle and intensity of light incident on the reticle 322.

[0030] Each of the patterns on the first reticle 322A, the second reticle 322B, and the third reticle 322C may correspond to a different metrology metric determined by the measurement system 200. For example, each individual pattern on the reticle 322 may determine a respective metrology metric. In some embodiments, which may be combined with other embodiments described herein, the metrology metric may correspond to the same pattern. In other embodiments, which may be combined with other embodiments described herein, the metrology metric may require extraction of multiple patterns. Furthermore, each of the patterns on the first reticle 322A, the second reticle 322B, and the third reticle 322C may correspond to multiple metrology metrics. Therefore, multiple reticles 322 are required to obtain different metrology metrics for the optical device 100. The reticle tray 308 is not limited to three reticles 322. The reticle tray 308 can be operable to hold more than three reticles 322 or less than three reticles 322. For example, there can be an array of reticles 322 disposed on the reticle tray 308.

[0031] The first light, the second light, and the third light are directed from the reticle 322 to the second lens 310. In one embodiment, which can be combined with other embodiments described herein, the second lens 310 is an eyepiece. The second lens 310 can operate to direct a pattern from the reticle 322 to the first grating 104a. The second lens 310 transforms the pattern so that the first grating 104a can receive the pattern. The pattern projected from the reticle 322 undergoes TIR until the pattern is outcoupled from the third grating 104c. The third grating 104c corresponds to the out-coupling grating.

[0032] 3B is a schematic diagram of a second configuration 300B of light engine 210 of measurement system 200 according to embodiments described herein. Second configuration 300B includes white light source 302D, first lens 306, color filter tray 312, reticle tray 308, and second lens 310. White light source 302D, first lens 306, color filter tray 312, reticle tray 308, and second lens 310 are disposed within light engine body 213.

[0033] The white light source 302D can be operated to project white light corresponding to a certain range of wavelengths. In one embodiment, which can be combined with other embodiments described herein, the white light source 302D is an LED. In another embodiment, which can be combined with other embodiments described herein, the wavelength range is 390 nm to 750 nm, which corresponds to white light. The color filter tray 312 includes a first color filter 314A, a second color filter 314B, and a third color filter 314C. The first color filter 314A can be operated to filter the white light so that a first wavelength or a first range of wavelengths of a first light is projected onto the optical device 100. The second color filter 314B can be operated to filter the white light so that a second wavelength or a second range of wavelengths of a second light is projected onto the optical device 100. The third color filter 314C can be operable to filter white light such that a third wavelength or third range of wavelengths of the third light is projected onto the optical device 100. The color filter tray 312 can be operable to move in one or more of the X, Y, and Z directions during operation of the methods described herein such that light is projected through one of the first color filter 314A, the second color filter 314B, and the third color filter 314C.

[0034] The white light source 302D directs white light through a first lens 306 onto a color filter tray 312. The color filter tray converts the white light into filtered light, such as the first light, second light, or third light described above. This light is directed to a reticle tray 308 to project a corresponding pattern onto a reticle 322, as described above with reference to the first configuration 300A. The pattern is directed to a second lens 310, which converts the pattern so that it can be received by the first grating 104a. The pattern projected from the reticle 322 undergoes TIR until it is outcoupled from a third grating 104c, which corresponds to an out-coupling grating.

[0035] 3C is a schematic diagram of a third configuration 300C of the light engine 210 of the measurement system 200 according to embodiments described herein. The third configuration 300C includes a display module 316 and a second lens 310. The display module 316 and the second lens 310 are disposed within the light engine body 213. The display module 316 may include a microLED module, a liquid crystal on silicon (LCOS) module, a digital light processing (DLP) module, or a laser projection module. The display module 316 may be operable to project a pattern onto the first grating 104a of the optical device 100. The display module 316 may be operable to project multiple different patterns onto the first grating 104a. Each pattern projected by the display module 316 may correspond to a different metrology metric determined by the measurement system 200. Each pattern may correspond to a red channel, a green channel, and a blue channel. The second lens 310 transforms the pattern so that the first grating 104a can receive the pattern. Each pattern projected from the display module 316 TIRs until the pattern is outcoupled from the third grating 104c, which corresponds to the out-coupling grating.

[0036] 3D is a schematic diagram of a fourth configuration 300D of the light engine 210 of the measurement system 200 in accordance with embodiments described herein. The fourth configuration 300D includes a laser module 318 disposed within the light engine body 213. The laser module 318 may be one of a laser projection module or a laser scanning module. The laser module 318 is operable to project a pattern onto the first grating 104a of the optical device 100. The laser module 318 is operable to project multiple different patterns onto the first grating 104a. Each pattern projected by the laser module 318 may correspond to a different metrology metric determined by the measurement system 200. Each pattern may correspond to a red channel, a green channel, and a blue channel. The pattern may be projected onto a single pixel of the first grating 104a. The laser module 318 is scanned across the first grating 104a such that the pattern is projected onto multiple pixels of the first grating 104a. Each pattern projected from the laser module 318 TIRs until the pattern is outcoupled from the third grating 104c, which corresponds to the out-coupling grating.

[0037] 3E is a schematic diagram of a fifth configuration 300E of the light engine 210 of the measurement system 200 in accordance with embodiments described herein. The fifth configuration 300E includes a module 320 and a second lens 310. The module 320 and the second lens 310 are disposed within the light engine body 213. In one embodiment that can be combined with other embodiments described herein, the module 320 may be a display module 316. In another embodiment that can be combined with other embodiments described herein, the module 320 may include a light source (i.e., the first light source 302A, the second light source 302B, the third light source 302C, or the white light source 302D with the color filter tray 312) and a reticle 322 on the reticle tray 308. The module 320 can be operated to rotate and / or tilt. By rotating the module 320, the angle of incidence of the light projected from the module 320 can be adjusted. For example, the module 320 can be rotated and / or tilted using a rotational stage. The module 320 can operate to project multiple different patterns onto the first grating 104a. Each pattern projected by the module 320 can correspond to a different metrology metric determined by the measurement system 200. Each pattern can correspond to a red channel, a green channel, and a blue channel. The second lens 310 transforms the pattern so that the first grating 104a can receive it. Rotating and / or tilting the module 320 can reduce ghost imaging. Ghost imaging can be reduced by reflecting the pattern projected onto the first grating 104a rather than directly back to the module 320 and the second lens 310. Additionally, rotating and / or tilting the module 320 can provide an expanded field of view for the measurement system 200. For example, rotating and / or tilting the module 320 can provide a field of view between approximately 10 degrees and approximately 120 degrees.

[0038] Configurations 300A-300E of light engine 210 are all operable to be utilized with measurement system 200. The configurations 300A-300E of light engine 210 used in measurement system 200 are determined by the design of optical device 100. Furthermore, configurations 300A-300E can be selected based on the intended use of optical device 100 to be measured by measurement system 200. For example, the field of view of configurations 300A-300E should match the field of view that will be used with optical device 100. Configurations 300A-300E are designed for measurement systems 200 having a field of view between about 10 degrees and about 120 degrees.

[0039] FIG. 4 is a schematic diagram of an alignment camera 208 configuration 400 of the measurement system 200 according to embodiments described herein. The alignment camera 208 includes one or more cameras 401 disposed therein. The one or more cameras 401 capture one or more images of one or more alignment markers 407 on the optical device 100. The one or more images are processed in the controller 220 to determine the location and orientation of the optical device 100. A scan path for the measurement system 200 can be generated along the optical device 100 based on the one or more images of the alignment markers 407. The scan path can operate to correct for misalignment of the optical device 100. The alignment camera 208 can operate to correct for any misalignment of the optical device 100 relative to the light engine 210 and the reflectance detector 212. Correcting the misalignment via the one or more alignment markers 407 enables the light engine 210 to accurately project a pattern onto the first grating 104a. For example, alignment marker 407 provides a field of view for alignment with first grating 104a. Thus, by aligning the field of view with first grating 104a and making it substantially equal to the width of first grating 104a, the overall efficiency of measurement system 200 is improved by effectively in-coupling light into first grating 104a.

[0040] 5 is a flow diagram of a method 500 of optical device metrology according to embodiments described herein. Method 500 can be utilized to project a pattern onto first grating 104a of optical device 100. Method 500 can be utilized with any of configurations 300A-300E of light engine 210. In one embodiment, which can be combined with other embodiments described herein, light engine 210 can be operatively disposed on a rotational stage such that light engine 210 can be rotated and / or tilted as needed during method 500.

[0041] In operation 501, a pattern is projected. The pattern is projected via the light engine 210. As shown in a first configuration 300A, light can be projected by a first light source 302A. The light can be directed from the first light source 302A to a first lens 306 to collimate the light. As shown in a second configuration 300B, light can be projected from a white light source 302D that passes through a first color filter 314A of a color filter tray 312. The light can be directed from the white light source 302D to a first lens 306 to collimate the light. As shown in a third configuration 300C, the light can be projected by a display module 316. As shown in a fourth configuration 300D, the light can be projected by a laser module 318. As shown in a fifth configuration 300E, the light can be projected by a module 320. The light corresponds to a wavelength or a range of wavelengths.

[0042] In some embodiments, which can be combined with other embodiments described herein, as shown in first configuration 300A and second configuration 300B, reticle tray 308 is arranged so that light is projected onto reticle tray 308. Reticle tray 308 is arranged so that one of first reticle 322A, second reticle 322B, or third reticle 322C of multiple reticles 322 arranged on reticle tray 308 can receive light from first lens 306. Reticle 322 is selected based on one or more metrology metrics to be determined. A pattern corresponding to one of first reticle 322A, second reticle 322B, or third reticle 322C is projected onto first grating 104a of optical device 100. The designed pattern can be guided to first grating 104a via second lens 310. Second lens 310 is an eyepiece. In other embodiments, which may be combined with other embodiments described herein, the pattern is generated by one of the display module 316, the laser module 318 or the module 320, as shown in the third configuration 300C, the fourth configuration 300D and the fifth configuration 300E, respectively.

[0043] In operation 502, one or more images of the pattern are detected. The one or more images of the pattern are captured by the reflectance detector 212. The pattern undergoes TIR until the pattern is outcombined (e.g., reflected or transmitted) and captured by the reflectance detector 212 as one or more images. The one or more images are processed to extract a metrology metric. The images are full-field images. The one or more images can be processed in the controller 220 (shown in FIG. 2). The controller 220 can be a remote controller 220 operable to receive the one or more images. The controller 220 can include a central processing unit (CPU) configured to process computer-executable instructions stored in a memory. The computer-executable instructions can include an algorithm configured to extract the metrology metric. For example, the controller 220 can be configured to perform an embodiment of the method 500 described herein, such as processing one or more images to determine a value for a metrology metric corresponding to each pattern captured in the one or more images. Those skilled in the art will recognize that one or more elements of controller 220 may be located remotely and accessed over a network.

[0044] In operation 503, operations 501 and 502 are repeated for subsequent patterns. Each subsequent pattern can be projected with light corresponding to a wavelength or range of wavelengths. For example, each pattern can be a red channel, a green channel, or a blue channel. As shown in FIGS. 3A and 3B, first configuration 300A and second configuration 300B each include a reticle tray 308 so that each subsequent pattern can correspond to a different reticle 322. As shown in FIGS. 3C-3E, third configuration 300C, fourth configuration 300D, and fifth configuration 300E each include a display module 316, a laser module 318, or a module 320 so that each subsequent pattern can be generated by display module 316, laser module 318, or module 320, respectively. In one embodiment, which can be combined with other embodiments described herein, each subsequent pattern is different from the preceding pattern. In another embodiment, which can be combined with other embodiments described herein, each subsequent pattern is the same as the preceding pattern.

[0045] In summary, a measurement system light engine and a method for using the light engine are described herein. The measurement system includes a light engine operable to illuminate a first grating of an optical device. The light engine projects a pattern onto the first grating so that metrology metrics can be extracted from one or more images captured by a detector of the measurement system. The metrology metrics determine whether the optical device meets image quality standards. The light engine is operable to rotate and tilt so that ghost imaging can be reduced. Additionally, an alignment camera of the measurement system allows misalignments to be corrected within the measurement system.

[0046] While the foregoing is directed to embodiments of the present disclosure, other embodiments of the disclosure may be devised without departing from the basic scope thereof, the scope of which is determined by the claims that follow.

Claims

1. 1. A measurement system comprising: a stage operable to hold an optical device or to hold an optical device substrate having at least one optical device disposed thereon; a light engine disposed above the stage, a plurality of light sources operable to project light of a range of wavelengths onto the optical device; a first lens operable to collimate the light from each of the plurality of light sources; a reticle tray positioned below the plurality of light sources, the reticle tray having a plurality of reticles positioned thereon, each reticle of the plurality of reticles having a pattern that is projected when the light is directed onto the each reticle of the plurality of reticles; a second lens operable to receive the pattern projected from each of the plurality of reticles, the second lens operable to project the pattern onto an input coupling grating of the optical device; a light engine including A measurement system comprising:

2. The measurement system of claim 1 , wherein the optical engine is coupled to a rotation stage, the rotation stage operable to rotate or tilt the optical engine.

3. 2. The measurement system of claim 1, wherein the plurality of light sources comprises a first light source operable to project wavelengths in a first range of 620 nm to 750 nm, a second light source operable to project wavelengths in a second range of 495 nm to 570 nm, and a third light source operable to project wavelengths in a third range of 450 nm to 495 nm.

4. 10. The measurement system of claim 1, further comprising an alignment camera adjacent to the light engine, the alignment camera operable to capture one or more images of one or more alignment markers on the optical device or on the optical device substrate.

5. The measurement system of claim 1 , wherein the light engine includes a plurality of mirrors operable to direct the light from the plurality of light sources to the first lens.

6. The measurement system of claim 1 , further comprising a reflective detector adjacent to said light engine, said reflective detector positioned to detect said pattern projected from each of said plurality of reticles.

7. 2. The measurement system of claim 1, further comprising a transmission detector positioned on an opposite side of the stage from the optical engine, the transmission detector operable to detect the pattern projected from each of the plurality of reticles.

8. 1. A measurement system comprising: a stage operable to hold an optical device or to hold an optical device substrate having at least one optical device disposed thereon; a light engine disposed above the stage, 1. A module operable to project one or more patterns onto the optical device, wherein the light engine is operable to rotate and / or tilt to adjust the angle of incidence of the one or more patterns projected onto the optical device or the optical device substrate. a light engine including: an alignment camera adjacent to the light engine, the alignment camera positioned to capture one or more images of one or more alignment markers on the optical device or on the optical device substrate; a reflective detector adjacent to the light engine, the reflective detector positioned to detect an outcoupled beam projected from the optical device; A measurement system comprising:

9. 9. The measurement system of claim 8, wherein the light engine further comprises a second lens operable to receive the one or more patterns, the second lens operable to project the one or more patterns onto an input coupling grating of the optical device.

10. The measurement system of claim 8 , wherein the patterns can correspond to a red channel, a green channel, and a blue channel, respectively.

11. 9. The measurement system of claim 8, wherein the module is a micro LED module, a liquid crystal on silicon (LCOS) module, a digital light processing (DLP) module, or a laser projection module operable to project the one or more patterns.

12. The measurement system of claim 8 , wherein the module is a laser projection module or a laser scanning module operable to project the one or more patterns.

13. 9. The measurement system of claim 8, wherein the field of view of the light engine is between about 10 degrees and about 100 degrees.

14. The measurement system of claim 8 , wherein the stage is transparent.

15. 1. A method comprising: projecting a pattern, the pattern being projected using light from a light engine, the light engine being disposed within a measurement system, the measurement system comprising: a stage disposed below the optical engine; a tray disposed above the stage, the tray having an optical device or an optical device substrate with at least one optical device disposed thereon, the optical device operable to receive the pattern; a reflective detector oriented toward the stage; projecting a pattern having a detecting one or more images of the pattern, the one or more images being detected when the pattern undergoes total internal reflection through the optical device and is outcoupled into the reflectance detector; processing the one or more images to extract metrology metrics; A method comprising:

16. The method of claim 15 , wherein an optical width of the light is substantially equal to a width of an input coupling grating of the optical device.

17. The method of claim 15 , further comprising rotating or tilting the light engine when projecting the light.

18. The method of claim 15 , further comprising utilizing an alignment camera of the measurement system to correct for misalignment of the optical device relative to the light engine.

19. 16. The method of claim 15, wherein the metrology metrics include one or more of an angular uniformity metric, a contrast metric, an efficiency metric, a color uniformity metric, a modulation transfer function (MTF) metric, a field of view (FOV) metric, a ghost image metric, and an eyebox metric.

20. The method of claim 15 further comprising repeating the method for subsequent patterns.

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