CN211696895U - Detection system for diffractive optical element - Google Patents

Abstract

The present application provides a detection system for a diffractive optical element, comprising: the light source is used for emitting linearly polarized light to the beam splitting part; the beam splitting part is used for splitting the received linearly polarized light into two beams of linearly polarized light which have equal amplitude and form a preset angle; the fixing part is used for fixing the diffraction optical element to be detected; the detection part is used for receiving the diffraction light beam to detect the diffraction optical element to be detected, wherein the diffraction light beam is formed by the diffraction of the diffraction optical element to be detected on two linearly polarized light beams. Just so need not to rotate or remove the DOE for the in-process that realizes the detection to the DOE in two directions, can improve the detection efficiency to the DOE on the one hand, on the other hand need not to place the DOE twice, can reduce as far as possible and cause the possibility of harm to the DOE to promote the security of diffraction optical element's detecting system in the detection process of DOE.

Description

Detection system for diffractive optical element

Technical Field

The application relates to the technical field of 3D imaging, in particular to a detection system of a diffractive optical element.

Background

A Diffractive Optical Element (DOE) is a novel Optical Element which is developed rapidly, and is widely applied to a laser projection module of a 3D (3-Dimension) depth camera, and the performance of the DOE directly affects the quality of a projection pattern, and further affects the depth imaging effect of the depth camera.

The diffraction behavior of the DOE can be divided into quasi-static zone diffraction (grating constant d < lambda/2), resonance zone diffraction (lambda/2 < d <10 lambda) and scalar diffraction zone (d >10 lambda), the difference of the three kinds of diffraction mainly results from the difference of the interaction between the light wave and the DOE, and correspondingly, the research theory of the DOE diffraction characteristics is divided into scalar diffraction theory and vector diffraction theory. The period d of a general DOE grating structure is in the same order of magnitude as the designed light wavelength lambda (lambda < d <10 lambda), the two are located in a resonance region, and the complex DOE grating structure has the characteristic of anisotropy, and the grating structure can generate a transmission loss phenomenon related to the light polarization direction.

The light sources adopted in the existing detection system of the DOE are all linearly polarized light, and during performance test of the DOE, the DOE is usually required to be tested twice, namely, the DOE is respectively detected in two directions of 0 degree and 90 degrees of rotation.

SUMMERY OF THE UTILITY MODEL

An object of the embodiments of the present application is to provide a detection system for a diffractive optical element, so as to efficiently and safely detect the diffractive optical element.

In order to achieve the above object, embodiments of the present application are implemented as follows:

in a first aspect, an embodiment of the present application provides a detection system for a diffractive optical element, including: the light source is used for emitting linearly polarized light to the beam splitting part; the beam splitting part is used for splitting the received linearly polarized light into two beams of linearly polarized light which have equal amplitude and form a preset angle; the fixing part is used for fixing the diffraction optical element to be detected; the detection part is used for receiving a diffraction light beam to detect the diffraction optical element to be detected, wherein the diffraction light beam is formed by the diffraction optical element to be detected by diffracting the two linearly polarized light beams.

In this application embodiment, the detection system of the diffractive optical element includes the beam splitting portion, and the linearly polarized light emitted by the received light source can be split into two linearly polarized light beams with equal amplitude and a preset angle, so that when the detection system of the diffractive optical element performs a performance test on the DOE, the DOE is detected according to a diffracted light beam formed by diffracting the two linearly polarized light beams by the diffractive optical element (i.e., the DOE) to be detected. Therefore, the DOE DOEs not need to be rotated or moved in the detection process of the DOE in two directions, and on the other hand, the DOE DOEs not need to be placed twice, so that the possibility of damage to the DOE can be reduced as much as possible, and the safety of the detection system of the diffractive optical element in the detection process of the DOE is improved.

With reference to the first aspect, in a first possible implementation manner of the first aspect, the preset angle is 90 °.

In this implementation, the anisotropic characteristic of the grating structure of the DOE means that the grating structure of the DOE generates transmission loss related to the polarization direction of light. That is, the DOE performance is closely related to the angle α between the polarization direction of incident light and the groove-cutting direction of the DOE grating, and generally, when the polarization direction of incident light is parallel to the groove-cutting direction of the grating, that is, the angle α is 0 degree, the DOE performance is the best, and the conversion efficiency is the highest, and when the polarization direction of incident light is perpendicular to the groove-cutting direction of the grating, that is, the angle α is 90 degrees, the DOE performance is the worst, and the conversion efficiency is the lowest. Therefore, the preset angle for detecting the performance of the DOE is set to be 90 degrees, the beam splitting part can split the received linearly polarized light into two beams of linearly polarized light which are equal in amplitude and form 90 degrees, and therefore the detection accuracy and the detection effectiveness can be guaranteed as far as possible.

With reference to the first possible implementation manner of the first aspect, in a second possible implementation manner of the first aspect, the beam splitting part is an 1/4 wave plate.

In this implementation, using the 1/4 wave plate as the beam splitting section makes it possible to split the received linearly polarized light into two linearly polarized light beams having equal amplitudes and 90 ° angles in a simple and efficient manner.

With reference to the first possible implementation manner of the first aspect, in a third possible implementation manner of the first aspect, the beam splitting section is a polarization direction rotator.

In this implementation, using the polarization direction rotator as the beam splitting section, the angle of beam splitting can be flexibly set (the preset angle can also be set to 90 °).

With reference to the first aspect, in a fourth possible implementation manner of the first aspect, the detection part includes a projection screen and a receiving device, where the projection screen is configured to receive the diffracted light beam and form an image; and the receiving device is used for acquiring the diffraction image on the projection screen and processing the diffraction image so as to determine the detection result of the diffraction optical element to be detected.

In this implementation, the detection unit includes a projection screen and a receiving device, and the receiving device can acquire the diffraction image on the projection screen and perform processing to determine the detection result of the diffractive optical element to be detected. Therefore, the diffraction optical element to be detected can be accurately detected.

With reference to the first aspect, in a fifth possible implementation manner of the first aspect, the light source is a collimated single-point laser.

In the implementation mode, the single-point laser is used as the light source, so that the part for collimating the traditional light source can be omitted, and the structure of the detection system of the diffractive optical element is favorably optimized.

With reference to the first aspect, in a sixth possible implementation manner of the first aspect, the detection system of the diffractive optical element further includes a control portion, where the control portion is respectively connected to the light source and the detection portion, and is configured to control the light source to emit linearly polarized light, and to control the detection portion to collect the diffracted light beam to detect the diffractive optical element to be detected.

With reference to the first aspect or any one of the first to the sixth possible implementation manners of the first aspect, in a seventh possible implementation manner of the first aspect, the light source, the beam splitting part, the fixing part, and the detection part are located on a same axis.

In this implementation, the light source, the beam splitting part, the fixing part and the detection part are located on the same axis, which is beneficial to ensuring the detection accuracy.

In order to make the aforementioned objects, features and advantages of the present application more comprehensible, preferred embodiments accompanied with figures are described in detail below.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments of the present application will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and that those skilled in the art can also obtain other related drawings based on the drawings without inventive efforts.

Fig. 1 is a schematic structural diagram of a laser projection module according to an embodiment of the present disclosure.

FIG. 2 shows the diffraction patterns at 0 and 90 respectively according to the embodiments of the present application.

Fig. 3 is a schematic structural diagram of a detection system of a diffractive optical element according to an embodiment of the present disclosure.

Fig. 4 is a flowchart of a detection method of a diffractive optical element according to an embodiment of the present application.

Icon: 100-a laser projection module; 101-a VCSEL light source; 102-a collimating mirror; 103-diffractive optical element; 200-a detection system for a diffractive optical element; 210-a light source; 220-a beam splitting part; 230-a fixed part; 240-a detection section; 241-a projection screen; 242 — a receiving device.

Detailed Description

The technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application.

Before describing the detection system of the diffractive optical element provided in the embodiments of the present application, a background thereof will be introduced here to facilitate understanding of the present solution.

The diffractive optical element (i.e., DOE) is a new optical element with rapid development, and can be applied to a laser projection module of a 3D depth camera. Referring to fig. 1, fig. 1 is a schematic structural diagram of a laser projection module 100 according to an embodiment of the present disclosure.

In this embodiment, the laser projection module 100 may include a VCSEL light source 101, a collimating mirror 102, and a diffractive optical element 103.

The VCSEL light source 101 may be a two-dimensional VCSEL light source 101 arranged in a two-dimensional pattern composed of a plurality of sub-light sources, and for convenience of description, three sub-light sources are exemplarily shown in fig. 1 on a one-dimensional level, but should not be considered as a limitation of the present application. Compared with a conventional laser light source, the VCSEL light source 101 has the advantages of small size, small divergence angle, and the like, but has the characteristic that the polarization directions of the emitted laser light are not uniform, that is, the polarization directions of the emitted light of each light emitting point are not uniform. Therefore, collimation can be performed using the collimator lens 102.

Illustratively, the collimating mirror 102 may receive the light beam emitted by the VCSEL light source 101 (with non-uniform polarization direction) and collimate the light beam with a certain divergence angle (i.e., the light beam emitted by the VCSEL light source 101).

Illustratively, the diffractive optical element 103 may be configured to receive the light beam collimated by the collimating mirror 102, and project the diffracted light beam into the target space by means of light diffraction. The diffracted beam is formed by replicating the VCSEL light source 101, for example, if the VCSEL light source 101 has 100 sub-light sources and the number of replicas of the diffractive optical element 103 is 100, 10000 scattered spots are formed in the space.

And the diffraction behavior of the diffractive optical element 103 can be classified into quasi-static zone diffraction (grating constant d < λ/2), resonance zone diffraction (λ/2< d <10 λ), and scalar diffraction zone (d >10 λ), where λ is the wavelength of light. The difference between the three diffraction behaviors is mainly the difference between the interaction of the light wave and the diffractive optical element 103, and accordingly, the research theories of the diffraction characteristics of the diffractive optical element 103 are divided into two major categories, namely scalar diffraction theory and vector diffraction theory.

In the field Of structured light or light TOF (Time Of Flight) applications, the size Of the grating period d Of the diffractive optical element 103 is usually Of the same order Of magnitude as the wavelength λ (λ 940 nm). The grating structure of the diffractive optical element 103 has anisotropic characteristics, which are very similar to the characteristics of the crystalline anisotropy, meaning that the grating structure of the diffractive optical element 103 generates transmission losses that are related to the direction of polarization of the light. I.e. the performance of the diffractive optical element 103 is closely related to the angle alpha between the polarization direction of the incident light and the grating groove direction of the diffractive optical element 103. In general, when the polarization direction of incident light is parallel to the grating groove direction (i.e., α is 0 °), the performance of the diffractive optical element 103 is best and the conversion efficiency is highest; when the polarization direction of the incident light is perpendicular to the grating groove direction (i.e., α is 90 °), the performance of the diffractive optical element 103 is the worst and the conversion efficiency is the lowest.

In order to eliminate the error caused by the polarization direction of the incident light to the performance detection of the diffractive optical element 103, the diffractive optical element 103 may be detected in the direction α ═ 0 ° to obtain a diffraction pattern as shown in part a in fig. 2. Then, the diffractive optical element 103 may be rotated counterclockwise by 90 °, where α is equal to 90 °, and the diffractive optical element 103 may be detected once again, so as to obtain a diffraction spot pattern as shown in part B in fig. 2. Then, the light intensities corresponding to the light spots can be averaged to obtain a detection result. For example, black dots in the portions a and B of fig. 2 indicate spot points of the same diffraction order, and the light intensities corresponding to the points in the two diffraction patterns (the portions a and B) are averaged to obtain the light intensity corresponding to the point.

However, in the conventional detection mode, the diffractive optical element 103 needs to be rotated and detected twice, so that on one hand, the detection efficiency is not high; on the other hand, during the rotation of the diffractive optical element 103, the microstructure of the diffractive optical element 103 is easily damaged, thereby generating additional loss of the diffractive optical element 103.

In view of the above problem, referring to fig. 3, an embodiment of the present invention provides a detection system 200 for a diffractive optical element, so as to safely and efficiently detect a diffractive optical element 103.

In the present embodiment, the detection system 200 of the diffractive optical element may include: light source 210, beam splitting unit 220, fixing unit 230, and detection unit 240. Wherein the light source 210 is used to emit linearly polarized light to the beam splitting part 220. And the beam splitting part 220 may split the received linearly polarized light into two linearly polarized lights having equal amplitudes and a predetermined angle. The fixing portion 230 is used for fixing the diffractive optical element to be tested. The detection unit 240 may receive a diffracted light beam to detect the diffractive optical element to be measured, where the diffracted light beam is formed by diffracting two linearly polarized light beams by the diffractive optical element to be measured.

In order to ensure the detection accuracy, the light source 210, the beam splitting part 220, the fixing part 230, and the detection part 240 may be located on the same axis. Of course, the fixing portion 230 is not limited to this, and for example, the fixing portion 230 does not need to be located on the same axis as the light source 210, the beam splitting portion 220, and the detection portion 240, and only needs to be located on the same axis as the light source 210, the beam splitting portion 220, and the detection portion 240 in the case of detecting the diffractive optical element to be detected, which is provided on the fixing portion 230.

Illustratively, to ensure the accuracy of the detection, the linearly polarized light emitted by the light source 210 needs to be collimated. Therefore, the light source 210 may be a collimated single-point laser, and the single-point laser is used as the light source, so that a part for collimating the conventional light source can be omitted, which is beneficial to optimizing the structure of the detection system of the diffractive optical element.

Of course, the light source 210 may also be a conventional light source (the polarization direction of the emitted light beam is not uniform), such as a VCSEL light source, and in order to obtain collimated linearly polarized light, the light source 210 may further include a collimating mirror for collimating the linearly polarized light emitted by the VCSEL light source. Therefore, the type of the light source 210 can be selected according to actual needs without limitation. In addition, in the description of the VCSEL light source and the collimating mirror being divided into the light source 210, the description is only for convenience of illustration, and in some other realizable manners, the VCSEL light source and the collimating mirror may be respectively used as independent parts in the detection system 200 of the diffractive optical element, which is not limited herein.

In order to achieve safe and efficient detection of the diffractive optical element, the beam splitting part 220 may be configured to split the received linearly polarized light into two linearly polarized light beams with equal amplitude and a preset angle, for example. After the beam splitting part 220 splits the received linearly polarized light into two linearly polarized lights which have equal amplitudes and form a preset angle, when the diffractive optical element to be detected is detected, the detection of the diffractive optical element to be detected in different directions can be realized in one detection process, and the diffractive optical element to be detected does not need to be moved or rotated in the detection process layer.

On the one hand, the detection efficiency of the diffraction optical element to be detected can be improved, on the other hand, the diffraction optical element to be detected does not need to be rotated, the damage to the microstructure of the diffraction optical element to be detected in the rotating process can be effectively avoided, the possibility of damage to the diffraction optical element to be detected is reduced as much as possible, and the safety of the detection system 200 of the diffraction optical element in the detection process of the diffraction optical element to be detected is improved.

In order to ensure the accuracy of the detection of the diffractive optical element, the preset angle may be 90 ° (see the above for the principle). The 90 ° may be within a certain error range, for example, within 0.1 °, but should not be construed as a limitation, and the error range may be set according to actual needs.

It should be noted that, the preset angle is 90 ° and is determined based on the currently effective detection method, and when it is determined that other angles can achieve good detection effects, the preset angle may also be set to be a corresponding angle, so that the present application should not be limited herein.

In order to realize that the beam splitting part 220 splits the received linearly polarized light into two linearly polarized light beams with equal amplitude and 90 °, the beam splitting part 220 may adopt 1/4 wave plate. Of course, when the preset angle is other angles, the slide implementing the angle may be selected as the beam splitting part 220, and is not limited herein. In this way, the received linearly polarized light can be simply and efficiently split into two linearly polarized lights with equal amplitude and 90 degrees. In addition, the 1/4 wave plate is selected, the structure and the arrangement mode of the detection system 200 of the diffraction optical element are simple, and the cost is low.

Specifically, when the 1/4 wave plate is used for beam splitting, it is first possible to make the linearly polarized light emitted from the light source 210 perpendicularly incident on the 1/4 wave plate and adjust the polarization direction of the light to be at an angle of 45 ° with respect to the optical axial plane of the 1/4 wave plate. At this time, after the linearly polarized light enters the 1/4 wave plate, two linearly polarized lights with equal amplitudes and mutually perpendicular directions are generated, the amplitudes of the two linearly polarized lights are I × cos45 ° and I × sin45 °, wherein I is an incident light amplitude, and the two linearly polarized lights with equal amplitudes and mutually perpendicular directions can be incident on the diffraction optical element to be detected, so that the diffraction optical element to be detected forms a diffraction light beam to be projected outwards, so that the detection part 240 receives the diffraction light beam, and the detection of the diffraction optical element to be detected is realized.

In addition, light sources with different light wavelengths can correspond to 1/4 wave plates with different designs, wherein the 1/4 wave plate plays the role of: the incident beam is decomposed into two linearly polarized light beams with equal amplitude and mutually perpendicular polarization directions, namely the polarization directions are respectively along the directions of 0 degree and 90 degrees. After the two linearly polarized light beams are diffracted, the light intensity of the diffracted light beam (or the diffracted image) detected by the detection part 240 is equal to the average value of the light intensity of the light beam when the diffraction optical element to be tested is tested along 0 degrees and 90 degrees respectively when the 1/4 wave plates are not added.

For example, the beam splitting part 220 may also select a polarization direction rotator to split the received linearly polarized light into two linearly polarized light beams with equal amplitude and a preset angle. For example, the received linearly polarized light is split into two linearly polarized lights having equal amplitudes and an angle of 90 ° using a polarization direction rotator.

Using the polarization direction rotator as the beam splitting part 220, the angle of beam splitting can be flexibly set. Generally, the polarization direction rotator can continuously rotate the polarization direction of linearly polarized incident light by at least 180 degrees, no mechanical motion is generated, and the adjustable range is very flexible. The polarization direction rotator can ensure that the minimum extinction ratio is greater than 1000:1 in the whole rotation range. There are a variety of polarization rotators (e.g., liquid crystal polarization rotators), and the polarization of an incident beam is controlled by the polarization rotator, for example, by scanning in 1 ° step from 0 ° to 180 °, and a diffracted beam (or a diffracted image) can be detected by the detecting unit 240 to record the change in the light intensity. The recorded data can be used to obtain not only the average value of the light intensities of the light beams of 0 ° and 90 °, but also the maximum light intensity value and the minimum light intensity value to calculate the Polarization Dependent Loss (PDL), which is a parameter for describing the sensitivity of the performance of the diffractive optical element to be measured to the Polarization state of the incident light beam.

In this embodiment, the fixing portion 230 is used for placing the diffractive optical element to be measured, and may be a clamping member, a fitting member, or the like, so as to fix the diffractive optical element to be measured, which is not limited herein.

In this embodiment, the detection part 240 may include a projection screen 241 and a receiving device 242, wherein the projection screen 241 may receive the diffracted light beam and image; the receiving device 242 may be configured to acquire a diffraction image on the projection screen 241 and process the diffraction image to determine a detection result of the diffractive optical element to be detected, so as to accurately detect the diffractive optical element to be detected. The receiving device 242 may include an image sensor and an image processing device, so that the diffraction image on the projection screen 241 is obtained by the image sensor, and the image processing device can detect the diffractive optical element to be detected according to the diffraction image.

In the present embodiment, in order to achieve efficient operation of the detection system 200 of the diffractive optical element, the detection system 200 of the diffractive optical element may further include a control section. The control part may be connected to the light source 210 and the detection part 240, respectively, for controlling the light source 210 to emit linearly polarized light, and for controlling the detection part 240 to collect diffracted light beams to detect the diffractive optical element to be detected.

Based on the same concept, the embodiment of the application also provides a detection method applied to the detection system of the diffractive optical element.

Referring to fig. 4, fig. 4 is a flowchart illustrating a method for inspecting a diffractive optical element according to an embodiment of the present disclosure. In this embodiment, the detection method of the diffractive optical element may include: step S10, step S20, step S30, and step S40.

In order to realize efficient and safe detection of the diffractive optical element to be detected, a detection system of the diffractive optical element can be used for detecting the diffractive optical element to be detected.

For example, the diffractive optical element to be tested may be placed at a corresponding position on the fixed part, and the detection system of the diffractive optical element may be calibrated. For example, the parameters of the components and the distances between the components in the detection system in which the diffractive optical element is arranged are such as to produce sharp and sharp images.

After calibration of the detection system of the diffractive optical element, the detection system may perform step S10.

Step S10: linearly polarized light is emitted to the beam splitting part through the light source.

For example, when the light source adopts a VCSEL light source and a collimator to obtain collimated linearly polarized light, the detection system may control the light source to emit preset linearly polarized light, and after being collimated by the collimator, the collimated linearly polarized light is emitted to the beam splitting part.

After emitting the linearly polarized light to the beam splitting section, the detection system may perform step S20.

Step S20: the received linearly polarized light is split into two linearly polarized light beams with equal amplitude and a preset angle through the beam splitting part, and the two linearly polarized light beams are projected to the diffraction optical element to be measured fixed through the fixing part.

For example, the detection system may split the received collimated linearly polarized light into two linearly polarized light beams having equal amplitudes and a preset angle (e.g., 90 °) by the beam splitting part, and project the two linearly polarized light beams to the diffraction optical element to be measured fixed by the fixing part.

After projecting the two linearly polarized light beams to the diffractive optical element to be measured fixed by the fixing part, the inspection system may perform step S30.

Step S30: and diffracting the two linearly polarized light beams with preset angles through the diffraction optical element to be detected, and projecting the diffracted light beams generated by diffraction to the detection part.

For example, the detection system may diffract two linearly polarized light beams at a predetermined angle (e.g., 90 °) through the diffractive optical element to be detected, and project the diffracted light beams generated by diffraction to the detection portion.

After the diffracted beam generated by the diffraction is projected to the detection part, the detection system may perform step S40.

Step S40: and receiving the diffracted light beams by the detection part so as to detect the diffraction optical element to be detected.

For example, the detection system may receive the diffracted light beam through the detection portion to detect the diffractive optical element to be detected.

Specifically, the detection system can receive the diffracted light beam through the projection screen of the detection part and form an image, acquire a diffraction image on the projection screen through the receiving device, and process the diffraction image to determine a detection result of the diffractive optical element to be detected. For example, a diffraction image is acquired from an image sensor by an image processing device of the receiving apparatus in the detection section (the image sensor detects the diffraction image on the projection screen), and then the diffraction image is processed and calculated to detect the performance of the diffractive optical element to be measured.

It should be noted that by the detection method of the diffractive optical element provided in the embodiment of the present application, detection of multiple optical properties of the diffractive optical element to be detected can be achieved.

By way of example, the detection of the number of spots of the diffractive optical element to be measured can be achieved: for the DOE (diffractive optical element) applied to the structured light depth camera, the main function of the DOE is to serve as a light beam splitter, and a light spot array image formed by a plurality of light spot points is formed. The quality of the DOE design directly affects the number of split spots and the diffraction effect of the suppression orders. The full-field diffraction image can be collected firstly, then each light spot of the full-field diffraction image is extracted, the number of the spots is counted, and the number of the spots is output as a result. If the number of blobs DOEs not match the preset number of blobs (e.g., the number of blobs is not satisfactory), the DOE is determined not to have reached its associated index.

By way of example, the detection of the diffraction efficiency of the diffractive optical element to be detected can be realized: the diffraction efficiency is the ratio of the total intensity of diffracted beams after the DOE is emitted to the intensity of incident beams on the DOE, and reflects the diffraction effect of the DOE. The higher the diffraction efficiency, the lower the power consumption requirements of the light source will be for generating a diffraction beam pattern of the same intensity.

It is often difficult to directly measure the total intensity of the diffracted beam by means of a quantitative measurement of the diffraction effect of the DOE. Therefore, the diffraction efficiency can be calculated by adopting an indirect method in the scheme, for example, the extraction of the pixel value is carried out on the acquired full-field diffraction image. Specifically, the pixel values with the size above the threshold value in each level of the spot image of the full-field diffraction image can be extracted according to the preset threshold value of the pixel values, and then the ratio of the sum of the gray values of each level of the spot image of the full-field diffraction image to the total gray value of the full-field image is used as the diffraction efficiency, so that the indirect detection of the diffraction efficiency is realized.

By way of example, the detection of the zero order size of the diffractive optical element to be detected can be realized: the zero order size may represent the ratio of the spot energy of the zero order to the spot energy of the adjacent first order. Here, the zero-order uniformity (i.e. zero-order size) may also be detected by using an indirect detection method, for example, pixel values exceeding a preset pixel threshold value in pixel values corresponding to the zero-order light spot and each light spot of an adjacent order may be extracted respectively according to the acquired full-field diffraction image and by combining the preset pixel threshold value, and a ratio of a sum of gray values of the extracted zero-order light spots to a gray average value of the light spots of the adjacent order may be used as the zero-order size.

By way of example, the detection of the global uniformity of the diffractive optical element to be measured can also be achieved: global uniformity is used to measure the intensity uniformity of each diffraction order in the full-field diffraction image. Here, the global uniformity can also be detected by indirect detection. Specifically, the gray level can be adjusted according to a preset gray level thresholdExtracting pixel values of light spot pixels at each level in the full-field diffraction image, wherein the gray value of each light spot pixel is greater than a preset gray threshold value, and the maximum value (I)_max) And a minimum value (I)_min) The sum of the maximum value and the minimum value of the difference ratio is the global uniformity:

wherein, uniformity represents the global uniformity of the diffractive optical element to be measured.

Illustratively, the detection of the polarization dependent loss of the diffractive optical element to be detected can also be realized. Polarization dependent loss is a phenomenon of transmission loss of an optical device related to the polarization state of light, and is the maximum transmission difference value of the optical device or system in all polarization states, and is defined by the following formula:

wherein, T_maxRepresenting the maximum light intensity, T, in all polarization states_minRepresenting the minimum light intensity in all polarization states.

Of course, by using the detection system and the detection method for the diffractive optical element provided in the embodiment of the present application, other optical properties of the diffractive optical element to be detected may also be detected, which are not described in detail herein, but these should not be considered as limitations to the present application.

In summary, the embodiment of the present application provides a detection system for a diffractive optical element, which includes a beam splitting portion in the detection system for the diffractive optical element, and the beam splitting portion can split linearly polarized light emitted by a received light source into two linearly polarized light beams with equal amplitudes and a preset angle, so that when a performance test of a DOE is performed on the detection system for the diffractive optical element, the diffraction beam formed by diffracting the two linearly polarized light beams is performed according to a diffractive optical element (i.e., DOE) to be tested, and the DOE is detected. Just so need not to rotate or remove the DOE for the in-process that realizes the detection to the DOE in two directions, can improve the detection efficiency to the DOE on the one hand, on the other hand need not to place the DOE twice, can reduce as far as possible and cause the possibility of harm to the DOE to promote the security of diffraction optical element's detecting system in the detection process of DOE.

In the embodiments provided in the present application, it should be understood that the disclosed system and method may be implemented in other ways. The above-described system embodiments are merely illustrative, and for example, the division of the components is merely an exemplary division, and other division ways may be implemented in practice. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection of devices or units through some communication interfaces, and may be in an electrical, mechanical or other form.

In addition, the components described separately may or may not be physically separated, and the components shown may or may not be physical units, and some or all of the components may be selected according to actual needs to achieve the purpose of the embodiment.

In this document, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions.

The above description is only an example of the present application and is not intended to limit the scope of the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims (8)

1. A detection system for a diffractive optical element, comprising: a light source, a beam splitting part, a fixing part and a detection part,

the light source is used for emitting linearly polarized light to the beam splitting part;

the beam splitting part is used for splitting the received linearly polarized light into two beams of linearly polarized light which have equal amplitude and form a preset angle;

the fixing part is used for fixing the diffraction optical element to be detected;

the detection part is used for receiving a diffraction light beam to detect the diffraction optical element to be detected, wherein the diffraction light beam is formed by the diffraction optical element to be detected by diffracting the two linearly polarized light beams.

2. The diffractive optical element detection system according to claim 1, wherein the preset angle is 90 °.

3. The diffractive optical element detection system according to claim 2, wherein the beam splitting section is an 1/4 wave plate.

4. The detection system of a diffractive optical element according to claim 2, characterized in that said beam splitting section is a polarization direction rotator.

5. The detection system of a diffractive optical element according to claim 1, characterized in that said detection section includes a projection screen and a receiving device,

the projection screen is used for receiving the diffracted light beams and imaging;

and the receiving device is used for acquiring the diffraction image on the projection screen and processing the diffraction image so as to determine the detection result of the diffraction optical element to be detected.

6. The diffractive optical element detection system according to claim 1, wherein the light source is a collimated single point laser.

7. The detection system of a diffractive optical element according to claim 1, characterized in that the detection system of a diffractive optical element further comprises a control section,

the control part is respectively connected with the light source and the detection part and used for controlling the light source to emit linearly polarized light and controlling the detection part to collect the diffraction light beam so as to detect the diffraction optical element to be detected.

8. The detection system of a diffractive optical element according to any one of claims 1 to 7, characterized in that the light source, the beam splitting portion, the fixing portion, and the detection portion are located on the same axis.

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