Full-field measurement tool for waveguide combiners and metasurfaces

Abstract

This invention provides measurement tools and methods for acquiring the full field of view optical field of an optical device in order to determine multiple measurement metrics of the optical device. [Solution] The measuring tool 100 is used to split a light ray into a first optical path 136A and a second optical path 136B. The first and second optical paths are superimposed on the superimposed light ray and sent to the detector 128. The detector measures the intensity of the superimposed light ray. The first and second equations are used in combination with the intensity measurement to determine the amplitude and phase at a reference point directly adjacent to the second surface of at least one optical device.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to metrology tools. More specifically, the embodiments described herein provide metrology tools and methods for acquiring a full-field optical field of an optical device to determine multiple metrology metrics of the optical device.

Background Art

[0002] Virtual reality is generally considered to be a computer-generated simulated environment in which a user has an apparent physical presence. A virtual reality experience can be viewed by a head-mounted display (HMD), such as glasses or other wearable display devices, having a near-eye display panel as a lens for displaying a virtual reality environment generated in 3D to replace the actual environment.

[0003] However, augmented reality enables an experience where a user can still view the surrounding environment through the display lens of glasses or other HMD devices, and can also view an image of a virtual object that is generated for display and appears as part of that environment. Augmented reality can include any type of input, such as audio and haptic inputs, as well as virtual images, graphics, and videos, that enhance or augment the environment experienced by the user. As a new technology, there are many challenges and design constraints for augmented reality.

[0004] One such challenge is obtaining a complete characterization of optical devices used for virtual and augmented reality. Measurement metrics need to be measured to ensure that the optical device design is validated and that the optical device measurement metrics are monitored. To obtain measurement metrics, multiple measurement tools are used to determine different metrics, which can be time-consuming, inefficient, and costly. When obtaining measurement metrics, it is desirable to have a measurement method that is high overall, low cost, and has low bandwidth requirements. Therefore, a single measurement tool and method capable of obtaining a complete characterization of an optical device is desirable. Thus, what is needed in the art is a measurement tool and method that obtains the full field of view optical field of an optical device in order to determine multiple measurement metrics of the optical device. [Overview of the project]

[0005] In one embodiment, a measurement tool is provided. The measurement tool includes an optical engine operable to project a ray. The measurement tool further includes a first beam splitter disposed in the path of the ray. The first beam splitter is operable to split the ray into a first optical path and a second optical path, the first optical path being operable to be incident on an optical device. The measurement tool further includes a phase modulator disposed in the second optical path. The measurement tool further includes a second beam splitter disposed in the first and second optical paths. The second beam splitter is operable to superimpose the first and second optical paths to form a superimposed optical path. The measurement tool further includes a detector disposed in the superimposed optical path. The detector is operable to record the intensity of the superimposed optical path.

[0006] In another embodiment, a measurement tool is provided. The measurement tool includes an optical engine operable to project a ray. The measurement tool further includes a first beam splitter disposed in the path of the ray. The first beam splitter is operable to split the ray into a first optical path and a second optical path. The first optical path is operable to be incident on an optical device. The measurement tool further includes a modulation module disposed in the first optical path. The modulation module is operable to change the phase, amplitude, or incident angle of the first optical path. The measurement tool further includes an inclined mirror disposed in the second optical path and a second beam splitter disposed in the first and second optical paths. The second beam splitter is operable to superimpose the first and second optical paths to form a superimposed optical path. The measurement tool further includes a detector disposed in the superimposed optical path. The detector is operable to record the intensity of the superimposed optical path.

[0007] In another embodiment, a method is provided. This method includes projecting a ray onto a first beam splitter. The first beam splitter divides the ray into a first optical path and a second optical path. The method further includes projecting the first optical path onto an optical device. The first optical path travels through the optical device, which is a metasurface or a waveguide combiner. The method further includes projecting the second optical path onto a phase modulator. The phase modulator is operable to generate one or more phase-delayed images of the second optical path. The method further includes superimposing the first and second optical paths with a second beam splitter to form a superimposed optical path. The method further includes directing the superimposed optical path to a detector. The detector is operable to record intensity measurements of the first and second optical paths. The method further includes determining the full-field optical field of an optical device at a reference point located adjacent to the surface of the optical device from which the first optical path exits the optical device. The full-field optical field is determined by performing a Fourier transform on intensity measurements to reconstruct the amplitude and phase of the first optical path at the reference point.

[0008] To allow for a more detailed understanding of the features described above, a more detailed description of the disclosure, which has been briefly summarized above, may be made by reference to embodiments partially shown in the accompanying drawings. However, it should be noted that the accompanying drawings are illustrative embodiments only and should not be considered limiting in scope, as other equally valid embodiments may be recognized. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic cross-sectional view of a measuring tool according to an embodiment described herein. [Figure 2] This is a schematic cross-sectional view of a measuring tool according to an embodiment described herein. [Figure 3]This is a flowchart of a method for determining the full-field optical field of at least one optical device according to embodiments described herein. [Modes for carrying out the invention]

[0010] For ease of understanding, the same reference numerals are used to designate the same elements common to the figures where possible. It is intended that elements and features of one embodiment may be usefully incorporated into other embodiments without further description.

[0011] Embodiments of this disclosure generally relate to measurement tools. More specifically, embodiments described herein provide measurement tools and methods for acquiring the full field of view optical field of an optical device to determine a plurality of measurement metrics of the optical device. The measurement tool includes an optical engine operable to project a ray. The measurement tool further includes a first beam splitter disposed in the path of the ray. The first beam splitter is operable to split the ray into a first optical path and a second optical path, the first optical path being operable to be incident on the optical device. The measurement tool further includes a phase modulator disposed in the second optical path. The measurement tool further includes a second beam splitter disposed in the first and second optical paths. The second beam splitter is operable to superimpose the first and second optical paths to form a superimposed optical path. The measurement tool further includes a detector disposed in the superimposed optical path. The detector is operable to record the intensity of the superimposed optical path.

[0012] Figure 1 is a schematic cross-sectional view of the measuring tool 100. In a first embodiment of the measuring tool 100, the measuring tool 100 includes a third lens 122A and a fourth lens 122B. In a second embodiment of the measuring tool 100, the measuring tool 100 includes a fifth lens 124. The measuring tool 100 includes a phase modulator 120. In a first configuration of the phase modulator 120, the phase modulator 120 is a spatial light modulator. In a second configuration of the phase modulator 120, the phase modulator 120 is a piezoelectric driven mirror. In a third configuration of the phase modulator 120, the phase modulator 120 is an inclined mirror. Either the first or second embodiment of the measuring tool 100 includes at least one phase modulator 120 from the first, second, or third configurations.

[0013] The measuring tool 100 is operable to hold the substrate 108. The substrate 108 includes at least one optical device 102 disposed on the substrate 108. The substrate 108 can be any substrate used in the art and, depending on the use of the substrate 108, may be either opaque or transparent to a selected wavelength. Furthermore, the substrate 108 may have various shapes, thicknesses, and diameters. The substrate 108 may have a circular, rectangular, or square shape. The substrate 108 is not limited in the number of optical devices 102 that may be disposed on the substrate 108. Each optical device 102 may include multiple optical device structures disposed on the substrate 108. The optical device structures may be nanostructures having submicron dimensions, for example, nanoscale dimensions.

[0014] At least one optical device 102 described herein is exemplary, and it should be understood that other optical devices may be used together or modified to achieve aspects of the disclosure. In one embodiment, which may be combined with other embodiments described herein, the optical device 102 is a waveguide combiner. Waveguide combiners may be used for virtual reality, augmented reality, or mixed reality. In embodiments where the optical device 102 is a waveguide combiner, an input coupling region may be disposed on a first surface 104 of the optical device 102. An output coupling region may be disposed on a second surface 106 of the optical device 102. The second surface 106 is on the opposite surface from the first surface 104. In another embodiment, which may be combined with other embodiments described herein, the waveguide combiner includes an input coupling region and an output coupling region on the same surface, for example, on one of the first surface 104 or the second surface 106. In another embodiment, which may be combined with other embodiments described herein, the optical device 102 is a flat optical device, such as a metasurface. The metasurface includes, but is not limited to, a lens, a diffuser, a dot matrix projector, or a sensor.

[0015] The measurement tool 100 is operable to measure the full-field optical field of at least one optical device 102. The method described herein improves throughput, reduces storage and bandwidth requirements, and lowers the costs associated with the analysis of optical devices. The full-field optical field includes the amplitude and phase of light rays. The full-field optical field provides direct information about the optical device 102 by measuring the full-field optical field in parallel. Measurement metrics can be obtained from the full-field optical field to ensure that the design of the optical device 102 is validated and that optical device measurement metrics are monitored. Embodiments of the measurement tool 100 described herein provide the ability to obtain multiple measurement metrics with increased throughput. Measurement metrics include one or more of the following for waveguide combiners: angular uniformity metric, contrast metric, efficiency metric, color uniformity metric, modulation transfer function (MTF) metric, field of view (FOV) metric, ghost image metric, or eyebox metric. Measurement metrics include one or more of the following for metasurfaces: efficiency metric, point spread function (PSF) metric, or phase error metric.

[0016] The measurement tool 100 includes an optical engine 110, a first beam splitter 112, a second beam splitter 114, a mirror 116, a third beam splitter 118, a phase modulator 120, a first lens 126, and a detector 128. In some embodiments, which may be combined with other embodiments described herein, the measurement tool 100 includes one or more of a linear polarizer 130, a second lens 132, a pinhole 134, and an auxiliary lens 142. In a first embodiment of the measurement tool 100, the measurement tool 100 includes a third lens 122A and a fourth lens 122B. In a second embodiment of the measurement tool 100, the measurement tool 100 includes a fifth lens 124.

[0017] The optical engine 110 is operable to project a light ray onto the first beam splitter 112. In one embodiment, which can be combined with other embodiments described herein, the optical engine 110 is a light-emitting diode (LED) or a laser. In another embodiment, which can be combined with other embodiments described herein, the optical engine 110 includes a display module. The display module is operable to project a pattern onto the optical device 102. The display module may include a micro-LED module, a liquid crystal on silicon (LCOS) module, a digital photoprocessing (DLP) module, or a laser projection module. In yet another embodiment, which can be combined with other embodiments described herein, the light ray is incident on a linear polarizer 130 before contacting the first beam splitter 112. The linear polarizer 130 is operable to linearly polarize the incoming light ray. The linear polarizer 130 may be a half-wave plate.

[0018] A first beam splitter 112 splits the light ray into a first optical path 136A and a second optical path 136B. An optical device 102 is positioned in the first optical path 136A. The optical device 102 can be any suitable optical device, such as a waveguide combiner or a metasurface. The first optical path 136A is directed towards the optical device 102 to be measured. The first optical path 136A is incident on the first surface 104 of the optical device 102. In some embodiments, a modulation module 113 is positioned adjacent to the first surface 104. The modulation module 113 is operable to change the phase, amplitude, or incident angle of the first optical path 136A.

[0019] In an embodiment where the optical device 102 is a waveguide combiner, as shown in Figure 1, the first optical path 136A is incident on the input coupling region. The first optical path 136A passes through the waveguide combiner. The first optical path 136A exits from the output coupling region of the waveguide combiner. Although Figure 1 shows the optical device 102 as a waveguide combiner, the optical device 102 can be any suitable optical device, such as a metasurface. In an embodiment where the optical device 102 is a metasurface, the first optical path 136A is incident on the first surface 104 of the metasurface. The first optical path 136A is directed towards the center point 144 of the metasurface. The first optical path 136A passes through the metasurface and exits from the center point 144 of the metasurface.

[0020] The first optical path 136A is operable to incident on the mirror 116. The mirror 116 is positioned along the first optical path 136A, adjacent to the second surface 106 of the optical device 102. The mirror 116 is operable to direct the first optical path 136A towards the first lens 126. The first lens 126 is operable to direct the first optical path 136A towards the third beam splitter 118. In one embodiment, which can be combined with other embodiments described herein, the first lens 126 may be positioned between the second surface 106 and the mirror 116. In another embodiment, which can be combined with other embodiments described herein, the first lens 126 may be positioned between the mirror 116 and the third beam splitter 118, as shown in Figure 1. The first lens 126 is a relay lens. In another embodiment, which may be combined with other embodiments described herein, the auxiliary lens 142 is positioned between the optical device 102 and the mirror 116. The auxiliary lens 142 is a relay lens.

[0021] The second optical path 136B is incident on the second beam splitter 114. In one embodiment, which can be combined with other embodiments described herein, one or both of the second lens 132 and the pinhole 134 are positioned between the first beam splitter 112 and the second beam splitter 114 in the second optical path 136B. The second optical path 136B may pass through one or both of the second lens 132 and the pinhole 134. The second lens 132 is a relay lens. The pinhole 134 is operable to act as a low-pass filter for the second optical path 136B. The second beam splitter 114 is positioned adjacent to the phase modulator 120. The second beam splitter 114 is operable to direct the second optical path 136B toward the phase modulator 120.

[0022] The phase modulator 120 is operable to change the phase of the second optical path 136B. In a first configuration of the phase modulator 120, the phase modulator 120 is a spatial light modulator. In a second configuration of the phase modulator 120, the phase modulator 120 is a piezoelectric driven mirror. In a third configuration of the phase modulator 120, the phase modulator 120 is an inclined mirror. The phase modulator 120 changes the phase of the second optical path 136B. The second optical path 136B is directed to a third beam splitter 118. The phase modulator 120 generates one or more phase-modulated images of the second optical path 136B. In embodiments having the first or second configuration, one or more phase-delayed images may be produced. In embodiments having the third configuration, one or more linear phase-delayed images may be produced.

[0023] In the first embodiment, the third lens 122A and the fourth lens 122B are arranged along the second optical path 136B. The third lens 122A is adjacent to the phase modulator 120. The fourth lens 122B is adjacent to the detector 128. In the second embodiment, the fifth lens 124 is arranged along the second optical path 136B. To direct the second optical path 136B within the measurement tool 100, the first embodiment utilizes the third lens 122A and the fourth lens 122B, and the second embodiment utilizes the fifth lens 124. The third lens 122A, the fourth lens 122B, and the fifth lens 124 are relay lenses.

[0024] The third beam splitter 118 is operable to direct the first optical path 136A and the second optical path 136B toward the detector 128. The third beam splitter 118 superimposes the first optical path 136A and the second optical path 136B onto a superimposed optical path. The detector 128 is operable to obtain an intensity measurement value of the superimposed optical path. The detector 128 is operable to utilize the intensity measurement value to reconstruct the full-field optical field at the reference point 138. The reference point 138 is located directly adjacent to the second surface 106. The reference point 138 is located adjacent to the surface of the optical device 102 from which the first optical path 136A exits the optical device. The measurement metric of the optical device 102 is derived from the full-field optical field during post-processing. The measurement tool 100 communicates with a controller 140 that is operable to control the operation of the measurement tool 100.

[0025] FIG. 2 is a schematic cross-sectional view of a measurement tool 200. The measurement tool 200 is operable to hold a substrate 108. The substrate 108 includes at least one optical device 102 disposed thereon.

[0026] At least one optical device 102 described in this specification is an exemplary optical device, and it should be understood that other optical devices can be used together or modified to achieve the aspects of the present disclosure. In one embodiment, which can be combined with other embodiments described herein, the optical device 102 is a waveguide combiner. The waveguide combiner can be utilized for virtual reality, augmented reality, or mixed reality. In an embodiment where the optical device 102 is a waveguide combiner, an input coupling region can be disposed on a first surface 104 of the optical device 102. An output coupling region can be disposed on a second surface 106 of the optical device 102. The second surface 106 is on the surface opposite to the first surface 104. In another embodiment, which can be combined with other embodiments described herein, the waveguide combiner includes an input coupling region and an output coupling region on the same surface, for example, one of the first surface 104 or the second surface 106. In yet another embodiment, which can be combined with other embodiments described herein, the optical device 102 is a flat optical device, such as a metasurface.

[0027] The measurement tool 200 is operable to measure the full-field optical field of at least one optical device 102. The full-field optical field of the optical device 102 provides a complete characterization of the optical device 102. The full-field optical field includes the amplitude and phase of light rays. The full-field optical field provides direct information about the optical device 102 by measuring the full-field optical field in parallel. Measurement metrics can be obtained from the full-field optical field to ensure that the design of the optical device 102 is verified and the optical device measurement metrics are monitored. Embodiments of the measurement tool 200 described herein provide the ability to obtain multiple measurement metrics with increased throughput. The measurement metrics include, for a waveguide combiner, 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, or an eyebox metric, and, for a metasurface, one or more of an efficiency metric, a point spread function (PSF) metric, a modulation transfer MTF metric, or a phase error metric.

[0028] The measurement tool 200 includes an optical engine 210, a first beam splitter 212, a second beam splitter 218, a mirror 216, an inclined mirror 220, a first lens 222A, a second lens 222B, an auxiliary lens 242, and a detector 228. The optical engine 210 is operable to project a light ray onto the first beam splitter 212. In one embodiment, which may be combined with other embodiments described herein, the optical engine 210 is a light-emitting diode (LED) or a laser. In another embodiment, which may be combined with other embodiments described herein, the optical engine 210 includes a display module. The display module is operable to project a pattern onto the optical device 102. The display module may include a micro-LED module, a liquid crystal on silicon (LCOS) module, a digital photoprocessing (DLP) module, or a laser projection module.

[0029] The first beam splitter 212 splits the light ray into a first optical path 236A and a second optical path 236B. The optical device 102 is positioned in the first optical path 236A. The optical device 102 may be any suitable optical device, such as a waveguide combiner or a metasurface. The first optical path 236A is directed towards the optical device 102 to be measured. The first optical path 236A is incident on the first surface 104 of the optical device 102. In some embodiments, which may be combined with other embodiments described herein, a first modulation module 213 and a second modulation module 214 are positioned adjacent to the first surface 104 of the optical device 102. The first modulation module 213 and the second modulation module 214 are positioned on either side of the optical device 102. The first modulation module 213 and the second modulation module 214 are operable to change the phase, amplitude, or incident angle of the first optical path 236A.

[0030] In an embodiment where the optical device 102 is a metasurface, as shown in Figure 2, the first optical path 236A is incident on the first surface 104 of the metasurface. The first optical path 236A is directed towards the center point 144 of the metasurface. The first optical path 236A passes through the metasurface and exits from the center point 144 of the metasurface. Although Figure 2 shows the optical device 102 as a metasurface, the optical device 102 can be any suitable optical device, such as a waveguide combiner.

[0031] In an embodiment where the optical device 102 is a waveguide combiner, as shown in Figure 1, the first optical path 236A is incident on the input coupling region. The first optical path 236A passes through the waveguide combiner. The first optical path 236A exits from the output coupling region of the waveguide combiner.

[0032] The first optical path 236A is operable to incident on the mirror 216. An auxiliary lens 242 is positioned between the optical device 102 and the mirror 216. The auxiliary lens 242 is a relay lens. The mirror 216 is positioned along the first optical path 236A, adjacent to the second surface 106 of the optical device 102. The mirror 216 is operable to direct the first optical path 236A towards the second beam splitter 218.

[0033] The second optical path 236B is incident on the tilt mirror 220. The tilt mirror 220 is operable to change the phase of the second optical path 236B. The tilt mirror 220 changes the phase of the second optical path 236B. The second optical path 236B is directed towards the second beam splitter 218. The tilt mirror 220 generates one or more linear phase-delayed images of the second optical path 236B. The first lens 222A and the second lens 222B are positioned along the second optical path 236B. The first lens 222A is adjacent to the tilt mirror 220. The second lens 222B is adjacent to the detector 228. The first lens 222A and the second lens 222B are relay lenses.

[0034] The second beam splitter 218 is operable to direct the first optical path 236A and the second optical path 236B toward the detector 228. The second beam splitter 218 superimposes the first optical path 236A and the second optical path 236B into superimposed optical paths. The detector 228 is operable to acquire intensity measurements of the superimposed optical paths. The detector 228 is operable to use the intensity measurements to reconstruct the full-field optical field at reference point 238. Reference point 238 is located directly adjacent to the second surface 106. Reference point 238 is located adjacent to the surface of the optical device 102 from which the first optical path 236A exits the optical device 102. The measurement metric of the optical device 102 is derived from the full-field optical field during post-processing. The measurement tool 200 communicates with a controller 140 that is operable to control the operation of the measurement tool 200.

[0035] Figure 3 is a flowchart of method 300 for determining the full-field optical field of at least one optical device 102. At least one optical device 102 is disposed on a substrate 108 disposed in a measuring tool 100. For ease of explanation, method 300 is described with respect to the measuring tool 100 as shown in Figure 1. A controller 140 of the measuring tool 100 is operable to facilitate the operation of method 300. Method 300 is operable to be performed in conjunction with the measuring tool 200.

[0036] In operation 301, a light ray is projected. The light ray is projected from the optical engine 110 to the first beam splitter 112. The first beam splitter 112 splits the light ray into a first optical path 136A and a second optical path 136B.

[0037] In operation 302, the first optical path 136A is projected to incident on the optical device 102. In embodiments where the optical device 102 is a waveguide combiner, the first optical path 136A is incident on the input coupling region corresponding to the first surface 104. The first optical path 136A passes through the optical device 102. The first optical path 136A exits from the output coupling region of the optical device 102. The waveguide combiner is positioned so that the first optical path 136A can operate to incident on the input coupling region of the waveguide combiner. In embodiments where the optical device 102 is a metasurface, the first optical path 136A is incident on the first surface 104 of the metasurface. The first optical path 136A is directed to the center point 144 of the metasurface. The first optical path 136A passes through the metasurface and exits through the center point 144 of the metasurface and through the second surface 106. The metasurface is positioned so that it is operable to allow the first optical path 136A to enter the center point 144 of the metasurface. The first optical path 136A is directed towards the detector 128.

[0038] In operation 303, one or more phase-modulated images are produced. In one embodiment, which can be combined with other embodiments described herein, one or more phase-modulated images are phase-delayed images. The second optical path 136B is incident on the phase modulator 120 to produce one or more phase-delayed images. In the first and second configurations of the phase modulator 120, the phase modulator 120 is a spatial light modulator or a piezoelectric driven mirror. When the phase modulator 120 is in the first or second configuration, the phase modulator 120 is operable to generate one or more phase delays of the second optical path 136B. For example, four phase-delayed images of the second optical path 136B (i.e., 0.5π, π, 1.5π, 2π) are provided to the detector 128 and recorded. Each phase-delayed image will modify the intensity of the first optical path 136A and the second optical path 136B on the detector 128. Furthermore, three or more phase-delayed images reduce the impact of noise on the detector 128. In a third configuration of the phase modulator 120, the phase modulator 120 is an inclined mirror.

[0039] In another embodiment, which may be combined with other embodiments described herein, one or more phase-modulated images are linear phase-delayed images. When the phase modulator 120 is in the third configuration, an inclined mirror is utilized. The inclined mirror forms one or more linear phase-delayed images with linear phase changes. The inclined mirror is angled at a predetermined angle so that one or more linear phase-delayed images can be formed without aliasing. The linear phase-delayed images of the second optical path 136B are provided to the detector 128.

[0040] In operation 304, the first optical path 136A and the second optical path 136B are superimposed. The first optical path 136A and the second optical path 136B are superimposed by the third beam splitter 118. The first optical path 136A and the second optical path 136B are superimposed to form a superimposed optical path. The superimposed optical path is incident on the detector 128. The first lens 126 relays the first optical path 136A to the detector 128. In some embodiments, the fourth lens 122B also relays the reference field to the detector 128. The second lens 132 relays the optical field of one or more phase-delayed images from the phase modulator 120 to the detector 128. In some embodiments, the third lens 122A or the fifth lens 124 also relays the optical field of one or more phase-delayed images to the detector 128.

[0041] In operation 305, the full-field optical field of the optical device 102 at reference point 138 is determined. Reference point 138 is located directly adjacent to the second surface 106. In one embodiment, which can be combined with other embodiments described herein, reference point 138 is located in the output coupling region of the optical device 102. The full-field optical field provides a complete characterization of the optical device 102. Determining the full-field optical field at reference point 138 includes determining the amplitude and phase at reference point 138. In one embodiment, which can be combined with other embodiments described herein, the phase profile can be directly compared with the design of the optical device 102 and thus provide feedback to the manufacturing process. Detector 128 records intensity measurements of the superimposed optical paths to determine the amplitude and phase. When the phase modulator 120 is in the first or second configuration, the first equation can be used to determine the intensity measurement I(x,y;Φ) of the superimposed rays. I(x,y;Φ)=I1(x,y)+I2(x,y)cos(Ψ(x,y)+Φ) Here, I1 is the intensity measurement of the first optical path 136A, I2 is the intensity measurement of the second optical path 136B, Φ is the phase of one or more phase-delayed images provided by the phase modulator 120, and Ψ is the phase of the first optical path 136A at the reference point 138. I1 and I2 contain amplitude information at the reference point 138. By changing the phase Φ of the phase-delayed image with the phase modulator 120, multiple different images are used to solve for the amplitude and phase Ψ at the reference point 138. For example, the Fourier transform of (x, Φ) will reconstruct the amplitude and phase Ψ at the reference point 138. The amplitude and phase Ψ at the reference point 138 correspond to the full-field optical field.

[0042] When the phase modulator 120 is in the third configuration, the second equation is equal to the superimposed light ray intensity measurement I(x,y;Φ x,y ) can be used to determine. I(x,y;Φ)=I1(x,y)+I2(x,y)cos(Ψ(x,y)+Φ x,y ) Here, I1 is the intensity measurement of the first optical path 136A, I2 is the intensity measurement of the second optical path 136B, Φ is the phase of the linear phase-delayed image provided by the phase modulator 120, and Ψ is the phase of the first optical path 136A at the reference point 138. I1 and I2 contain amplitude information at the reference point 138. The tilted mirror moves the phase-delayed image Φ into the higher frequency domain. This image is used to solve for the amplitude and phase Ψ at the reference point 138. For example, the Fourier transform of (x, Φ) reconstructs the amplitude and phase Ψ at the reference point 138. The amplitude and phase Ψ at the reference point 138 correspond to the full-field optical field.

[0043] In one embodiment, which may be combined with other embodiments described herein, when the optical device 102 is a waveguide combiner, the full-field optical field at reference point 138 may be examined to determine its correlation with the image quality of the waveguide combiner. Furthermore, full-field optics may be used to monitor the uniformity of the optical device structure across the waveguide combiner. To monitor the uniformity of the optical device structure across the waveguide combiner, including limit dimensions, depth, trench filling, overcoating, etc., variations between each waveguide combiner are collected and compiled into a library of empirical data.

[0044] In operation 306, the measurement metric is determined. The full-field optical field at reference point 138 is determined in operation 305. The measurement metric of the optical device 102 is derived from the full-field optical field during post-processing. The measurement metric may be used to predict the performance of the optical device in the far field. The measurement metric may be used to verify the optical device design and monitor the performance of the optical device. In embodiments where the optical device 102 is a waveguide combiner, the measurement metric may include, but is not limited to, one or more of the following: angular uniformity metric, contrast metric, efficiency metric, color uniformity metric, modulation transfer function (MTF) metric, field of view (FOV) metric, ghost image metric, or eyebox metric. In embodiments where the optical device 102 is a metasurface, the measurement metric may include, but is not limited to, one or more of the following: efficiency metric, point spread function (PSF) metric, MTF metric, or phase error metric. The ability to derive any desired measurement metric from a single physical measurement improves throughput, reduces storage and bandwidth requirements, and lowers the costs associated with analysis using the optical device 102.

[0045] In summary, a measurement tool and method for acquiring the full-field optical field of an optical device to determine multiple measurement metrics of the optical device are provided herein. The measurement tool is used to split a ray into a first optical path and a second optical path. The first optical path travels through at least one optical device, such as a metasurface or waveguide combiner, and is directed to a detector. The second optical path is directed to a phase modulator. One or more phase-modulated images of the second optical path are captured by the detector. The first and second optical paths are superimposed on a superimposed ray and sent to the detector. The detector measures the intensity of the superimposed ray. The first and second equations are used in combination with the intensity measurements to determine the amplitude and phase Ψ at a reference point directly adjacent to the second surface of at least one optical device. The amplitude and phase Ψ correspond to the full-field optical field of the optical device. Measurement metrics can be derived from the full-field optical field. The method described herein improves throughput, reduces storage and bandwidth requirements, and lowers the costs associated with the analysis of optical devices.

[0046] The above applies to embodiments of the present disclosure, but other embodiments of the present disclosure may be devised without departing from its basic scope, the scope of which is determined by the following claims.

Claims

1. It is a measuring tool, A light engine capable of projecting light rays, A first beam splitter disposed in the path of the light ray, wherein the first beam splitter is operable to split the light ray into a first optical path and a second optical path, and the first optical path is operable to be incident on an optical device, A phase modulator disposed in the second optical path, A second beam splitter disposed in the first optical path and the second optical path, wherein the second beam splitter is operable to overlap the first optical path and the second optical path in order to form an overlapping optical path, A detector disposed in the superimposed optical path, wherein the detector is operable to record the intensity of the superimposed optical path. A measuring tool equipped with these features.

2. The measurement tool according to claim 1, wherein the optical device is a waveguide combiner, and the waveguide combiner is arranged to operate so that the first optical path is incident on the input coupling region of the waveguide combiner.

3. The measuring tool according to claim 1, wherein the optical device is a metasurface, and the metasurface is arranged such that the first optical path is incident on the central point of the metasurface.

4. The measurement tool according to claim 1, wherein the phase modulator is one of a spatial light modulator, a piezoelectric driven mirror, or an inclined mirror.

5. The measurement tool according to claim 1, wherein the optical engine projects a laser.

6. The measurement tool according to claim 1, wherein the phase modulator is operable to change the phase of the second optical path.

7. A first lens disposed in the first optical path, wherein the first lens is operable to relay the first optical path, A second lens disposed in the second optical path, wherein the second lens is operable to relay the second optical path, A third lens disposed in the second optical path, wherein the third lens is operable to relay the second optical path, A fourth lens disposed in the second optical path, wherein the fourth lens is operable to relay the second optical path. The measuring tool according to claim 1, further comprising:

8. The measuring tool according to claim 1, further comprising a linear polarizer capable of operating to polarize the aforementioned light ray.

9. The measuring tool according to claim 1, further comprising an auxiliary lens disposed in the first optical path, wherein the auxiliary lens is operable to relay the first optical path.

10. It is a measuring tool, A light engine capable of projecting light rays, A first beam splitter disposed in the path of the light ray, wherein the first beam splitter is operable to split the light ray into a first optical path and a second optical path, and the first optical path is operable to be incident on an optical device, A modulation module disposed in the first optical path, wherein the modulation module is operable to change the phase, amplitude, or incident angle of the first optical path, An inclined mirror arranged in the optical path of the second prepared, A second beam splitter disposed in the first optical path and the second optical path, wherein the second beam splitter is operable to overlap the first optical path and the second optical path in order to form an overlapping optical path, A detector disposed in the superimposed optical path, wherein the detector is operable to record the intensity of the superimposed optical path. A measuring tool equipped with these features.

11. The measurement tool according to claim 10, wherein the optical device is a waveguide combiner, and the waveguide combiner is arranged to operate so that the first optical path is incident on the input coupling region of the waveguide combiner.

12. The measuring tool according to claim 10, wherein the optical device is a metasurface, and the metasurface is arranged such that the first optical path is incident on the central point of the metasurface.

13. A first lens disposed in the second optical path, wherein the first lens is operable to relay the second optical path, A second lens disposed in the second optical path, wherein the second lens is operable to relay the superimposed optical paths, An auxiliary lens disposed in the second optical path, wherein the second lens is operable to relay the second optical path, and The measuring tool according to claim 10, further comprising:

14. Projecting a light ray onto a first beam splitter, wherein the first beam splitter divides the light ray into a first optical path and a second optical path, Projecting the first optical path onto an optical device, wherein the first optical path proceeds through the optical device, and the optical device is a metasurface or a waveguide combiner, Projecting the second optical path onto a phase modulator, wherein the phase modulator is operable to generate one or more phase-delayed images of the second optical path, In order to form superimposed optical paths, the first optical path and the second optical path are superimposed by a second beam splitter, Orienting the superimposed optical paths toward a detector, wherein the detector is operable to record intensity measurements of the first optical path and the second optical path, Determining the full field of view optical field of the optical device at a reference point located adjacent to the surface of the optical device from which the first optical path exits the optical device, wherein the full field of view optical field is determined by performing a Fourier transform on the intensity measurement in order to reconstruct the amplitude and phase of the first optical path at the reference point. Methods that include...

15. The method according to claim 14, further comprising determining a measurement metric, wherein the measurement metric is determined from the full field of view optical field during post-processing.

16. The method according to claim 15, wherein the measurement metric includes one or more of the following: angular uniformity metric, contrast metric, efficiency metric, color uniformity metric, modulation transfer function (MTF) metric, field of view (FOV) metric, ghost image metric, or eyebox metric.

17. The method according to claim 14, wherein the full-field optical field is determined in a high-frequency region.

18. The method according to claim 14, wherein each of the one or more phase-delayed images modifies the intensity measurement value of the superimposed optical path on the detector.

19. The method according to claim 14, further comprising arranging the optical device such that the optical device is a waveguide combiner and is operable to cause the first optical path to be incident on the input coupling region of the optical device.

20. The method according to claim 14, further comprising arranging the optical device such that the optical device is the metasurface and the first optical path is incident on the central point of the optical device.

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