CN116569028A - Illumination system for AR metrology tool - Google Patents

Abstract

Embodiments described herein provide light engines for measurement systems and methods of using the light engines. The measurement system includes a light engine operable to illuminate a first grating of the optical device. The light engine projects a pattern by light from the light engine. The light engine projects a pattern onto the first grating such that metrology metrics can be extracted from one or more images captured by a detector of the measurement system. These metrology metrics are extracted by processing the image. These metrology metrics determine whether the optical device meets image quality criteria.

Description

Illumination system for AR metrology tool

Background

Technical Field

Embodiments of the present disclosure generally relate to optical devices for augmented reality, virtual reality, and mixed reality. More particularly, embodiments described herein provide a light engine of a measurement system and a method of using the light engine.

Background

Virtual reality is generally considered a computer-generated simulated environment in which a user has a significant physical presence. The virtual reality experience can be generated in 3D and viewed through a Head Mounted Display (HMD), such as glasses or other wearable display device with a near-eye display panel as a lens, to display a virtual reality environment that replaces the actual environment.

However, augmented reality enables an experience in which a user is able to see through the display lenses of glasses or other HMD devices to view the surrounding environment, and also see virtual object imagery generated for display and rendering as part of the environment. Augmented reality can include any type of input, such as audio and tactile input, as well as virtual imagery, graphics, and video that enhance or augment the environment experienced by the user. As an emerging technology, augmented reality has many challenges and design limitations.

One such challenge is measuring the optics for image quality criteria. To ensure that the image quality criteria are met, a metrology (metric) of the finished optical device must be obtained. However, existing measurement systems lack the desired field of view and suffer from ghost imaging (imaging). Accordingly, what is needed in the art are measurement systems and methods of using the measurement systems having improved fields of view and reduced occurrence of ghost images.

Disclosure of Invention

In one embodiment, a measurement system is provided. The measurement system includes a stage operable to hold an optical device or to hold 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 to the optical device over a range of wavelengths. 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 (reticle) holder disposed below the plurality of light sources. The reticle carrier is provided with a plurality of reticles. Each of the plurality of reticles has a pattern that will be projected when the light is directed to each of the plurality of reticles. The light engine further includes a second lens operable to receive the pattern projected from each reticle of the plurality of reticles. The second lens is operable to project the pattern to an in-coupling grating of the optical device.

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 to the optical device. The light engine is operable to rotate and/or tilt to adjust an angle of incidence of the pattern projected toward 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 marks on the optical device or the optical device substrate. The measurement system further includes a reflection detector adjacent to the light engine. The reflective detector is positioned to detect an out-coupled (outcoupled) light beam projected from the optics.

In yet another embodiment, a method is provided. The method includes projecting a pattern. The pattern is projected by light from the light engine. The light engine is arranged in a measurement system. The measurement system includes a stage disposed below the light engine. The measurement system further includes a bracket disposed on the stage. The carrier includes an optical device or an optical device substrate having at least one optical device disposed thereon, and the optical device is 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 image is detected when the pattern undergoing total internal reflection by the optical device is outcoupled to the reflection detector. The method further includes processing the image to extract a metrology metric.

Drawings

So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

Fig. 1A is a perspective front view of a substrate according to embodiments described herein.

Fig. 1B is a perspective front view of an optical device according to embodiments described herein.

Fig. 2 is a schematic cross-sectional view of a measurement system according to embodiments described herein.

Fig. 3A-3E are schematic diagrams of configurations of light engines of measurement systems according to embodiments described herein.

Fig. 4 is a schematic diagram of a configuration of an alignment camera of a measurement system according to embodiments described herein.

Fig. 5 is a flow chart of an optical device metrology method according to embodiments described herein.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

Detailed Description

Embodiments of the present disclosure generally relate to optical devices for augmented reality, virtual reality, and mixed reality. More particularly, embodiments described herein provide a light engine of a measurement system and a method of using the light engine. The measurement system includes a stage operable to hold an optical device or to hold 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 to the optical device over a range of wavelengths. 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 carrier disposed below the plurality of light sources. The reticle carrier has a plurality of reticles disposed thereon. Each of the plurality of reticles has a pattern that is to be projected when the light is directed to each of the plurality of reticles. The light engine further includes a second lens operable to receive the pattern projected from each reticle of the plurality of reticles. The second lens is operable to project the pattern to an in-coupling grating of the optical device. The light engine may also include a module to project a pattern.

The method of using the light engine includes projecting a pattern through light from the light engine. The method further includes detecting one or more images of the pattern. The image is detected when the pattern undergoing total internal reflection by the optical device is outcoupled to the reflection detector. The method further includes processing the image to extract a metrology metric.

Fig. 1A is a perspective front view of a substrate 101 according to embodiments described herein. The substrate comprises a plurality of optical devices 100, the plurality of optical devices 100 being arranged on a surface 103 of the substrate 101. In some implementations (which can be combined with other implementations described herein), the optical device 100 is a waveguide combiner for virtual reality, augmented reality, or mixed reality. In some embodiments, which can be combined with other embodiments described herein, the optical device 100 is a flat optical device, such as a metasurface (metasurface).

The substrate 101 can be any substrate used in the art and can be opaque or transparent to the selected laser wavelength depending on the use of the substrate 101. The substrate 101 includes, but is not limited to, silicon (Si), silicon dioxide (SiO) ₂ ) Fused silica, quartz, silicon carbide (SiC), germanium (Ge), silicon germanium (SiGe), indium phosphide (InP), gallium arsenide (GaAs), gallium nitride (GaN), silicon nitride (SiN), or sapphire-containing materials. In addition, the substrate 101 may have different shapes, thicknesses, and diameters. For example, the substrate 101 may have a diameter of about 150mm to about 300 mm. The substrate 101 may have a circular, rectangular, or square shape. The substrate 101 may have a thickness of between about 300 μm to about 1 mm. Although only nine optical devices 100 are shown on the substrate 101, any number of optical devices 100 may be provided on the surface 103 of the substrate 101.

Fig. 1B is a perspective front view of the optical device 100. It will be understood that the optical device 100 described herein is an exemplary optical device and that other optical devices may be used or modified to achieve aspects of the present disclosure. The optical device 100 includes a plurality of optical device structures 102 disposed on a surface 103 of a substrate 101. The optical device structure 102 may be a nanostructure having a sub-micron dimension (e.g., a nano-sized dimension). The area of the optic structure 102 corresponds to one or more gratings 104, such as a first grating 104a, a second grating 104b, and a third grating 104c. In one embodiment (which can be combined with other embodiments described herein), the optical device 100 includes at least a first grating 104a corresponding to an in-coupling grating and a third grating 104c corresponding to an out-coupling grating. In another embodiment (which can be combined with other embodiments described herein), the optical device 100 also includes a second grating 104b corresponding to the intermediate grating. The optic structure 102 may be angled or binary. The optic structure 102 may have other cross-sections including, but not limited to, circular, triangular, elliptical, regular polygonal, irregular polygonal, and/or irregularly shaped cross-sections.

In operation, the first grating 104a receives incident light beams from the light engine, which have an intensity. 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 optics structure 102 into a T1 beam having the full intensity of the incident beam to direct the virtual image to the intermediate grating (if used) or the third grating 104c. In one embodiment, which can be combined with other embodiments described herein, the T1 beams undergo Total Internal Reflection (TIR) by the optical device 100 until the T1 beams contact the optical device structure 102 of the intermediate grating. The intermediate grating's optics structure 102 diffracts these T1 beams into T-1 beams, which undergo TIR through the optics 100 to the third grating's 104c optics structure 102. The optics structure 102 of the third grating 104c outcouples these T-1 beams to the user's eye. The T-1 beam that is outcoupled to the user's eye displays the virtual image generated from the light engine from the user's perspective (superpositive) and further increases the viewing angle from which the user can view the virtual image. In another embodiment, which can be combined with other embodiments described herein, the T1 beams undergo Total Internal Reflection (TIR) by the optical device 100 until the T1 beams contact the optical device structure 102 of the third grating 104c and are outcoupled to display a virtual image generated from the light engine.

To ensure that the optical device 100 meets the image quality standard, a metrology measurement of the manufactured optical device 100 must be taken. The metrology metrics of each optical device 100 are tested to ensure that a predetermined value is achieved. Embodiments of the measurement system 200 described herein provide the ability to obtain multiple metrology metrics with increased throughput. The metrology metrics include one or more of the following: angle uniformity metrics, contrast metrics, efficiency metrics, color uniformity metrics, modulation Transfer Function (MTF) metrics, field of view (FOV) metrics, ghost image metrics, and eye box (eye box) metrics.

Fig. 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, the body 201 having a first opening 203 and a second opening 205 to allow a stage 207 to move therethrough. Stage 207 is operable to move in the X-direction, Y-direction, and Z-direction in body 201 of measurement system 200. The stage 207 includes a carrier 209 that is operable to hold the optical device 100 (as shown herein) or one or more substrates 101 on which the optical device 100 is disposed.

The measurement system 200 is operable to obtain one or more metrology metrics, including one or more of: angle uniformity metrics, contrast metrics, efficiency metrics, color uniformity metrics, MTF metrics, FOV metrics, ghost image metrics, or eye box metrics. The stage 207 and the carrier 209 may be transparent such that metrology measurements taken by the measurement system 200 are not affected by the translucency of the stage 207 or the carrier 209. The measurement system 200 communicates with a controller 220. The controller 220 is operable to facilitate operation of the measurement system 200.

The measurement system 200 includes an upper portion 204 and a lower portion 206, the upper portion 204 being oriented toward a top side 222 of the optical device 100 and the lower portion 206 being oriented toward a bottom side 224 of the optical device 100. The upper portion 204 of the measurement system 200 includes an alignment camera 208, a light engine 210, and a reflection detector 212. The alignment camera 208 is operable to determine the position of the stage 207. The alignment camera 208 is also operable to determine the position of the optical device 100 disposed on the stage 207. Aligning camera 208 includes aligning camera body 211. The light engine 210 is operable to project light. For example, the light engine 210 is operable to illuminate the first grating 104a of the optical device 100. The light engine 210 includes a light engine body 213. In one embodiment (which can be combined with other embodiments described herein), the light engine 210 projects a pattern to the first grating 104a. The reflection detector 212 detects the outcoupled light beam projected from the third grating 104c of the optical device 100. These out-coupled light beams may emanate from either the top side 222 or the bottom side 224 of the optical device 100. These out-coupled light beams may correspond to a pattern from the light engine 210. One or more images of the pattern are detected by the reflection detector 212. One or more images of the pattern may be processed by the controller 220 to extract various metrology metrics.

The lower portion 206 of the measurement system 200 includes an encoder 214 and a transmission (transmission) detector 216. The code reader 214 and the transmission detector are positioned opposite the alignment camera 208, the light engine 210, and the reflection detector 212 on the other side of the stage 207. The code reader 214 is operable to read a code of the optical device 100, such as a Quick Response (QR) code or a bar code (barcode) of the optical device 100. The code read by the code reader 214 may include identification information and/or instructions for retrieving one or more metrology metrics of the optical device 100. The transmission detector 216 detects the outcoupled light beam projected from the third grating 104c through the 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-direction, the Y-direction, and the Z-direction. The transmission detector stage 226 is operable to adjust the position of the transmission detector 216 to enhance detection of the outcoupled light beam projected from the third grating 104c.

In operation, metrology metrics are obtained by illuminating the first grating 104a of the optical device 100 with the light engine 210. The light engine 210 projects a pattern to one or more optical devices 100. The in-coupled light undergoes TIR until it is out-coupled (e.g., reflected or transmitted) out of the optical device 100. The pattern is captured as one or more images by the reflectance detector 212. The one or more images may correspond to red, green, and blue channels. The one or more images may also correspond to one or more different metrology metrics. The one or more images are full-field images.

Fig. 3A is a schematic diagram of a first configuration 300A of the light engine 210 of the measurement system 200 according to embodiments described herein. The first configuration 300A includes a first light source 302A, a second light source 302B, a third light source 302C, a first mirror (mirror) 304A, a second mirror 304B, a first lens 306, a reticle carrier 308, and a second lens 310. The first light source 302A, the second light source 302B, the third light source 302C, the first mirror 304A, the second mirror 304B, the first lens 306, the reticle carrier 308, and the second lens 310 are disposed in the light engine body 213.

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

The second light source 302B is operable to project second light corresponding to a second wavelength or a second wavelength range. In one embodiment (which can be combined with other embodiments described herein), the second light source 302B is an LED. In another embodiment (which can be combined with other embodiments described herein), the second wavelength or second wavelength range is 495nm to 570nm corresponding to green light. The second light source 302B projects second light toward the first mirror 304A. The first mirror 304A is operable to direct the second light toward the first lens 306.

The third light source 302C is operable to project third light corresponding to a third wavelength or a third wavelength range. In one embodiment (which can be combined with other embodiments described herein), the third light source 302C is an LED. In another embodiment (which can be combined with other embodiments described herein), the third wavelength or third wavelength range is 450nm to 495nm corresponding to blue light. The third light source 302C projects third light toward the second mirror 304B. The second mirror 304B is operable to direct third light toward the first lens 306.

The first, second, and third light sources 302A, 302B, and 302C are not limited to the orientations and positions shown in fig. 3A. For example, the first light source 302A may be configured to project first light to 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 sources or extended sources. The first mirror 304A and the second mirror 304B are 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 may be dichroic mirrors.

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

The reticle carrier 308 includes 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 reticle 322 on the reticle carrier 308. Each of the first reticle 322A, the second reticle 322B, and the third reticle 322C may include a pattern to be projected to the first grating 104a of the optical device 100. Each of the first reticle 322A, the second reticle 322B, and the third reticle 322C may include different patterns. The pattern is projected when one of the first, second, and third light sources 302A, 302B, and 302C projects light to the reticle 322 such that the reticle 322 is illuminated. The pattern then illuminates the first grating 104a. The first grating 104a corresponds to an in-coupling grating of the optical device 100. Reticle carrier 308 is operable to move in one or more of an X-direction, a Y-direction, and a Z-direction. Thus, the reticle bracket 308 can be adjusted such that light is projected through one of the first reticle 322A, the second reticle 322B, and the third reticle 322C during operation of the methods described herein. Reticle carrier 308 is adjusted in the Z direction to improve the quality of the pattern to be projected. For example, adjusting the reticle bracket 308 in the Z direction may change the angle and intensity of light incident on the reticle 322.

Each of the patterns of the first reticle 322A, the second reticle 322B, and the third reticle 322C may correspond to a different metrology metric to be determined by the measurement system 200. For example, each respective pattern of reticle 322 may allow a respective metrology metric to be determined. In some embodiments (which can be combined with other embodiments described herein), these metrology metrics can correspond to the same pattern. In other embodiments (which can be combined with other embodiments described herein), these metrology metrics may require more than one pattern to be extracted. In addition, each pattern of the patterns of the first reticle 322A, the second reticle 322B, and the third reticle 322C may correspond to a plurality of metrology metrics. Thus, multiple reticles 322 are required to obtain different metrology metrics for the optical device 100. The reticle carrier 308 is not limited to three reticles 322. The reticle carrier 308 is operable to hold more or less than three reticles 322. For example, an array of reticles 322 can be provided on the reticle carrier 308.

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 lens (eyesource). The second lens 310 is operable to direct the pattern from the reticle 322 to the first grating 104a. The second lens 310 transforms the pattern such that the first grating 104a can receive the pattern. The pattern projected from reticle 322 undergoes TIR until it is outcoupled from third grating 104c. The third grating 104c corresponds to an out-coupling grating.

Fig. 3B is a schematic diagram of a second configuration 300B of the light engine 210 of the measurement system 200 according to embodiments described herein. The second configuration 300B includes a white light source 302D, a first lens 306, a color filter holder 312, a reticle holder 308, and a second lens 310. The white light source 302D, the first lens 306, the color filter holder 312, the reticle holder 308, and the second lens 310 are disposed in the light engine body 213.

The white light source 302D is operable to project white light corresponding to a range of wavelengths. In one embodiment (which can be combined with other embodiments described herein), white light source 302D is an LED. In another embodiment (which can be combined with other embodiments described herein), the wavelength range is 390nm to 750nm, which corresponds to white light. The color filter holder 312 includes a first color filter 314A, a second color filter 314B, and a third color filter 314C. The first color filter 314A is operable to allow white light to be filtered such that a first wavelength or first range of wavelengths of first light to be projected to the optical device 100 is projected to the optical device 100. The second color filter 314B is operable to allow white light to be filtered such that a second wavelength or a second range of wavelengths of the second light is projected to the optical device 100. The third color filter 314C is operable to allow white light to be filtered such that a third wavelength or third range of wavelengths of third light is projected to the optical device 100. The color filter carriage 312 is operable to move in one or more of an X-direction, a Y-direction, and a Z-direction such that light is projected through one of the first color filter 314A, the second color filter 314B, and the third color filter 314C during operation of the methods described herein.

The white light source 302D directs white light through the first lens 306 and to the color filter carrier 312. The color filter holder converts the white light into filtered light, such as the first light, the second light, or the third light described above. The light is directed to the reticle bracket 308 to project a pattern corresponding to the reticle 322, as described above with reference to the first configuration 300A. The pattern is directed to the second lens 310. The second lens 310 transforms the pattern such that the first grating 104a can receive the pattern. The pattern projected from reticle 322 undergoes TIR until it is outcoupled from third grating 104c. The third grating 104c corresponds to an out-coupling grating.

Fig. 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 in the light engine body 213. The display module 316 includes a micro LED module, a Liquid Crystal On Silicon (LCOS) module, a Digital Light Processing (DLP) module, or a laser projection module. The display module 316 is operable to project a pattern onto the first grating 104a of the optical device 100. The display module 316 is operable to project a plurality of different patterns onto the first grating 104a. Each pattern projected by the display module 316 may correspond to a different metrology metric to be determined by the measurement system 200. Each pattern may correspond to red, green, and blue channels. The second lens 310 transforms the pattern such that the first grating 104a can receive the pattern. Each pattern projected from display module 316 undergoes TIR until it is outcoupled from third grating 104c. The third grating 104c corresponds to an out-coupling grating.

Fig. 3D is a schematic diagram of a fourth configuration 300D of the light engine 210 of the measurement system 200 according to embodiments described herein. The fourth configuration 300D includes a laser module 318 disposed in 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 a plurality of different patterns onto the first grating 104a. Each pattern projected by the laser module 318 may correspond to a different metrology metric to be determined by the measurement system 200. Each pattern may correspond to red, green, and blue channels. The pattern may be projected to a single pixel of the first grating 104a. The laser module 318 scans over the first raster 104a such that the pattern is projected onto a plurality of pixels of the first raster 104a. Each pattern projected from laser module 318 undergoes TIR until it is outcoupled from third grating 104c. The third grating 104c corresponds to an out-coupling grating.

Fig. 3E is a schematic diagram of a fifth configuration 300E of the light engine 210 of the measurement system 200 according to 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 in the light engine body 213. In one embodiment (which can be combined with other embodiments described herein), the module 320 can be the display module 316. In another embodiment (which can be combined with other embodiments described herein), the module 320 can 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 along with the color filter holder 312) and a reticle 322 on the reticle holder 308. The module 320 is operable to be rotated and/or tilted. Rotation of the module 320 allows the angle of incidence of the light projected from the module 320 to be adjusted. For example, the module 320 is rotated and/or tilted by a rotary table. The module 320 is operable to project a plurality of different patterns onto the first grating 104a. Each pattern projected by module 320 may correspond to a different metrology metric to be determined by measurement system 200. Each pattern may correspond to red, green, and blue channels. The second lens 310 transforms the pattern such that the first grating 104a can receive the pattern. By rotating and/or tilting the module 320, ghost imaging may be reduced. Ghost imaging is reduced because the reflection of the pattern projected onto the first grating 104a is not reflected directly back to the module 320 and the second lens 310. In addition, rotation and/or tilting of the module 320 will provide field of view expansion for the measurement system 200. For example, rotation and/or tilting of the module 320 provides a field of view between about 10 degrees and about 120 degrees.

The configurations 300A-300E of the light engine 210 are all operable to be employed in the measurement system 200. The configuration 300A to 300E of the light engine 210 to be used in the measurement system 200 is determined by the design of the optical device 100. Further, the configurations 300A-300E can be selected based on the intended use of the optical device 100 to be measured by the measurement system 200. For example, the fields of view of the configurations 300A-300E should match the field of view to be used by the optical device 100. The configurations 300A-300E are designed for a measurement system 200 having a field of view between about 10 degrees and about 120 degrees.

Fig. 4 is a schematic diagram of an arrangement 400 of alignment cameras 208 of measurement system 200 according to embodiments described herein. The alignment camera 208 includes one or more cameras 401 disposed therein. One or more cameras 401 capture one or more images of one or more alignment marks 407 on the optical device 100. The one or more images are processed in the controller 220 to determine the position and orientation of the optical device 100. One or more images based on the alignment marks 407 may generate a scan path along the optical device 100 for the measurement system 200. The scan path is operable to correct for misalignment (misalignment) of the optical device 100. The alignment camera 208 is operable to correct any misalignment of the optical device 100 relative to the light engine 210 and the reflection detector 212. Misalignment correction via one or more alignment marks 407 allows the light engine 210 to accurately project a pattern onto the first grating 104a. For example, alignment marks 407 allow the field of view to be aligned with first grating 104a. Thus, having the field of view aligned with the first grating 104a and substantially equal to the width of the first grating 104a improves the overall efficiency of the measurement system 200 by effectively incoupling light into the first grating 104a.

Fig. 5 is a flow chart of a method 500 of optical device metrology according to embodiments described herein. The method 500 may be employed to project a pattern onto the first grating 104a of the optical device 100. The method 500 may be employed by any of the configurations 300A-300E of the light engine 210. In one embodiment (which can be combined with other embodiments described herein), the light engine 210 is operable to be disposed on a rotating table such that the light engine 210 can be rotated and/or tilted as desired during the method 500.

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

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

In operation 502, one or more images of the pattern are detected. The one or more images of the pattern are captured by the reflection detector 212. The pattern undergoes TIR until it is outcoupled (e.g., reflected or transmitted) and captured as one or more images by the reflection detector 212. The one or more images are processed to extract a metrology metric. These images are global images. The one or more images may be processed in a controller 220 (illustrated in fig. 2). The controller 220 may be a remote controller 220 operable to receive the one or more images. The controller 220 may include a Central Processing Unit (CPU) configured to process computer-executable instructions stored in memory. The computer-executable instructions may include an algorithm (algorithm) configured to extract a metric. For example, the controller 220 is configured to perform embodiments of the method 500 described herein, such as processing one or more images to determine values of metrology metrics corresponding to individual patterns captured in the one or more images. Those skilled in the art will appreciate that one or more elements of controller 220 may be located remotely and accessed via a network.

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

In summary, light engines of measurement systems and methods of using the light engines are described herein. The measurement system includes a light engine operable to illuminate a first grating of the optical device. The light engine projects a pattern onto the first grating such that metrology metrics can be extracted from one or more images captured by a detector of the measurement system. The metrology metric determines whether the optical device meets an image quality criterion. The light engine is operable to rotate and tilt such that ghost imaging may be reduced. In addition, an alignment camera of the measurement system allows for misalignment correction in the measurement system.

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

Claims (20)

1. A measurement system, comprising:

a stage operable to hold an optical device or an optical device substrate having at least one optical device disposed thereon; and

a light engine disposed above the stage, the light engine comprising:

a plurality of light sources operable to project light to the optical device over a range of wavelengths;

a first lens operable to collimate the light from each of the plurality of light sources;

a reticle carrier disposed below the plurality of light sources, the reticle carrier having a plurality of reticles disposed thereon, each of the plurality of reticles having a pattern,

the pattern is to be projected when the light is directed to each reticle of the plurality of reticles; and

a second lens operable to receive the pattern projected from each reticle of the plurality of reticles, the second lens operable to project the pattern to an in-coupling grating of the optical device.

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

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

4. 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 marks on the optical device or on the optical device substrate.

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

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

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

8. A measurement system, comprising:

a stage operable to hold an optical device or an optical device substrate having at least one optical device disposed thereon;

a light engine disposed above the stage, the light engine comprising:

a module operable to project one or more patterns to the optical device, wherein

The light engine is operable to rotate and/or tilt to adjust the orientation of the optical device or the optical device

Placing an incident angle of the pattern projected by the substrate;

an alignment camera adjacent to the light engine, the alignment camera positioned to capture one or more images of one or more alignment marks on the optical device or the optical device substrate; and

a reflective detector adjacent to the light engine, the reflective detector positioned to detect the outcoupled light beam projected from the optical device.

9. The measurement system of claim 8, wherein the light engine further comprises a second lens operable to receive the pattern, the second lens operable to project the pattern to an in-coupling grating of the optical device.

10. The measurement system of claim 8 wherein the patterns may each correspond to red, green, and blue channels.

11. The measurement system of claim 8, wherein 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. 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. A method, comprising:

a projection pattern projected by light from a light engine disposed in a measurement system having:

a stage disposed below the light engine;

a carrier disposed on the stage, the carrier having 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; and

a reflective detector oriented toward the stage;

detecting one or more images of the pattern, the images being detected when the pattern undergoing total internal reflection by the optical device is outcoupled to the reflection detector; and

the images are processed to extract metrology metrics.

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

17. The method of claim 15, further comprising: the light engine is rotated or tilted when the light is projected.

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

19. The method of claim 15, wherein the metrology metrics include one or more of: angle uniformity metrics, contrast metrics, efficiency metrics, color uniformity metrics, modulation Transfer Function (MTF) metrics, field of view (FOV) metrics, ghost image metrics, and eye box metrics.

20. The method of claim 15, further comprising: the method is repeated for subsequent patterns.