Mtf testing apparatus and mtf testing method

Abstract

The application provides an MTF testing device and an MTF testing method. The MTF testing device comprises: a sample fixing frame for fixing a device to be tested; a polarized light source assembly for projecting a polarized light pattern to the device to be tested; a plurality of imaging devices for receiving images projected by the device to be tested; and a plurality of first polarizers corresponding to the plurality of imaging devices one by one, and the first polarizers are arranged at the receiving end of the corresponding imaging devices. The MTF testing device in the embodiment of the application comprises the polarized light source assembly, which is used for projecting the polarized light pattern to the device to be tested. The polarized light pattern forms a projection image after passing through the polarized light system of the device to be tested. The projection image is received by the imaging device after passing through the first polarizer. According to the image data, the MTF of the polarized light system can be further obtained. The MTF testing device in the application can effectively measure the MTF of the polarized light system.

Description

Technical Field

[0001] This invention relates to the field of optical measurement technology, and in particular to an MTF testing device and an MTF testing method. Background Technology

[0002] The modulation transfer function (MTF) is an important parameter for evaluating the performance of optical systems, and designers frequently use it to compare the performance of different optical systems. Currently, the MTF is one of the best tools for quantitatively evaluating the overall imaging performance of an optical system in terms of resolution and contrast.

[0003] However, the MTF testing equipment in the related technology can only be used to measure unpolarized light systems, and cannot be effectively measured for polarized light systems (such as the Pancake optical system used in VR devices). Summary of the Invention

[0004] Therefore, it is necessary to provide an MTF testing device and an MTF testing method that can be used to effectively measure polarized light systems.

[0005] An embodiment of the first aspect of this application provides an MTF testing device for measuring the MTF of a device under test, wherein the device under test includes a polarized light system. The MTF testing device comprises: a sample holder for fixing the device under test; a polarized light source assembly for projecting a polarized light pattern onto the device under test; multiple imaging devices for receiving images projected by the device under test; and multiple first polarizers, wherein the multiple first polarizers and the multiple imaging devices are configured in a one-to-one correspondence, and the first polarizer is disposed at the receiving end of the corresponding imaging device.

[0006] The MTF testing device in this embodiment includes a polarized light source assembly. This assembly projects a polarized light pattern onto the device under test (DUT) mounted on a sample holder. The polarized light pattern passes through the DUT's polarization system to form a projected image. This projected image is then received by an imaging device after passing through a first polarizer. Based on the image data received by the imaging device, the MTF of the polarized light system can be further obtained. Therefore, the MTF testing device in this embodiment can effectively measure the MTF of a polarized light system.

[0007] In some embodiments of this application, the plurality of imaging devices includes a first imaging device and a second imaging device; the number of the first imaging device is one and it is disposed on the optical axis of the device under test; the number of the second imaging devices is two or more, and the second imaging devices are disposed around the first imaging device. Thus, by setting the first imaging unit and the second imaging unit, MTF measurements can be performed at different field positions.

[0008] In some embodiments of this application, the first polarizer is rotatably connected to the imaging device, allowing it to rotate around the optical axis of the imaging device. During measurement, the rotation angle of the first polarizer can be adjusted in real time, and the imaging device receives images projected by the device under test at each moment. Since the image is clearest when the output optical axis is aligned with the polarizer, obtaining the rotation angle of the first polarizer corresponding to the clearest image yields the polarization direction of the output light at the corresponding field position.

[0009] In some embodiments of this application, the polarized light source assembly includes: a backlight; a light source pattern plate disposed on the light-emitting side of the backlight, the light source pattern plate having a plurality of light-transmitting holes, the plurality of light-transmitting holes being combined to form a preset pattern; and a second polarizer disposed on the side of the light source pattern plate opposite to the backlight. Light emitted from the backlight passes sequentially through the light source pattern plate and the second polarizer to form a polarized light pattern.

[0010] In some embodiments of this application, the polarized light source assembly further includes a light homogenizer disposed between the backlight and the light source pattern board. The light homogenizer can homogenize the light emitted from the backlight, resulting in a more uniform light energy distribution. This improves the uniformity of energy distribution of the polarized light pattern emitted by the polarized light source assembly at various locations.

[0011] In some embodiments of this application, the second polarizer is a linear polarizer, a circular polarizer, or an elliptic polarizer.

[0012] In some embodiments of this application, the first polarizer is a circular polarizer, a linear polarizer, or an elliptic polarizer.

[0013] In some embodiments of this application, the MTF testing device further includes a processing unit electrically connected to each of the imaging devices, each of the imaging devices being configured to transmit image data to the processing unit, and the unit being configured to obtain the modulation transfer function (MTF) based on the image data.

[0014] An embodiment of the second aspect of this application provides an MTF testing method, the MTF testing method comprising:

[0015] The device under test is fixed to the sample holder, and the device under test includes a polarization system;

[0016] A polarized light pattern is projected onto the device under test using a polarized light source assembly;

[0017] Multiple imaging devices are provided, and each imaging device is equipped with a first polarizer at its receiving end, so that the images projected by the device under test are received by the multiple imaging devices.

[0018] Obtain the modulation transfer function (MTF) from the image data.

[0019] The MTF testing method in this embodiment provides a polarized light pattern to the device under test using a polarized light source assembly. The polarized light pattern passes through the polarized light system of the device under test to form a projected image. This projected image passes through a first polarizer and is received by an imaging device. Based on the image data received by the imaging device, the MTF of the polarized light system can be further obtained. Therefore, the MTF testing method in this embodiment can effectively measure the MTF of a polarized light system.

[0020] In some embodiments of this application, projecting a polarized light pattern onto the device under test using a polarized light source assembly includes:

[0021] A polarized light pattern is projected onto the device under test using a polarized light source assembly including a backlight, a light source pattern board, and a second polarizer. The light source pattern board is located on the light-emitting side of the backlight and has multiple light-transmitting holes that are combined to form a preset pattern.

[0022] With this setup, the light emitted from the backlight passes sequentially through the light source graphic plate and the second polarizer, thus forming a polarized light pattern.

[0023] In some embodiments of this application, the first polarizer is rotatably connected to the imaging device so that the first polarizer can rotate about the optical axis of the imaging device.

[0024] During the measurement process, the rotation angle of the first polarizer can be adjusted in real time, and the image projected by the device under test at each moment can be received through the imaging device. Since the image is clearest when the output light axis is in the same direction as the polarizer, the polarization direction of the output light at the corresponding field position can be obtained by obtaining the rotation angle of the first polarizer corresponding to the clearest image. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of an MTF testing device according to one embodiment of this application;

[0026] Figure 2This is a schematic diagram of the structure of a polarized light source component in one embodiment of this application;

[0027] Figure 3 This is a schematic diagram of the structure of the light source graphic board in one embodiment of this application;

[0028] Figure 4 This is the image when the output optical axis is aligned with the first polarizer;

[0029] Figure 5 This is the image when the output optical axis is not aligned with the first polarizer;

[0030] Figure 6 This is a flowchart illustrating the MTF testing method in one embodiment of this application.

[0031] The attached figures are labeled as follows:

[0032] 10. MTF testing equipment;

[0033] 20. Device to be tested;

[0034] 21. Polarized light system;

[0035] 100. Sample holder;

[0036] 200. Polarized light source assembly;

[0037] 210. Backlight;

[0038] 220. Light source graphic board;

[0039] 221. Light-transmitting hole;

[0040] 230. Second polarizer;

[0041] 240. Beam homogenizer;

[0042] 300. First imaging device;

[0043] 400. Second imaging device;

[0044] 500. First polarizer. Detailed Implementation

[0045] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0046] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0047] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0048] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0049] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0050] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0051] The modulation transfer function (MTF) is an important parameter for evaluating the performance of optical systems, and designers frequently use it to compare the performance of different optical systems. Currently, the MTF is one of the best tools for quantitatively evaluating the overall imaging performance of an optical system in terms of resolution and contrast.

[0052] However, existing MTF testing equipment can only be used to measure unpolarized light systems, and cannot effectively measure polarized light systems (such as the Pancake optical system used in VR devices). Therefore, it is necessary to develop a testing device that can effectively measure the MTF of polarized light systems.

[0053] Based on this, this application provides an MTF testing device 10 and an MTF testing method, which are intended to be used for effective measurement of a polarized light system 21.

[0054] like Figure 1 As shown, an embodiment of the first aspect of this application provides an MTF testing device 10 for measuring the MTF of a device 20 under test, wherein the device 20 under test includes a polarized light system 21. The MTF testing device 10 includes a sample holder 100, a polarized light source assembly 200, multiple imaging devices, and multiple first polarizers 500. The sample holder 100 is used to fix the device 20 under test, the polarized light source assembly 200 is used to project a polarized light pattern onto the device 20 under test, the imaging devices are used to receive the image projected by the device 20 under test, and the multiple first polarizers 500 and the multiple imaging devices are arranged in a one-to-one correspondence, with the first polarizer 500 disposed at the receiving end of the corresponding imaging device.

[0055] Specifically, the device under test 20 can be, for example, a lens with a polarization system 21, a lens group with a polarization system 21, or other optical devices with a polarization system 21.

[0056] The sample holder 100 is a frame that can fix the device under test 20. After the device under test 20 is installed on the sample holder 100, the device under test 20 is restricted on the sample holder 100 and cannot move or rotate freely. In this embodiment, the sample holder 100 can adopt any existing fixing frame structure that can fix the device under test 20.

[0057] A polarizer is an optical element used to generate polarized light. For example, a linear polarizer is used to generate linearly polarized light, a circular polarizer is used to generate circularly polarized light, and an elliptically polarizer is used to generate elliptically polarized light.

[0058] The MTF testing device 10 in this embodiment includes a polarized light source assembly 200. This assembly projects a polarized light pattern onto the device under test 20, which is mounted on a sample holder 100. The polarized light pattern passes through the polarization system 21 of the device under test 20 to form a projected image. This projected image passes through a first polarizer 500 and is received by an imaging device. Based on the image data received by the imaging device, the MTF of the polarization system 21 can be further obtained. Therefore, the MTF testing device 10 in this embodiment can effectively measure the MTF of the polarization system 21.

[0059] In some embodiments of this application, such as Figure 1 As shown, the plurality of imaging devices includes a first imaging device 300 and a second imaging device 400. The number of the first imaging device 300 is one and it is disposed on the optical axis of the device under test 20. The number of the second imaging devices 400 is two or more and the second imaging devices 400 are disposed around the first imaging device 300.

[0060] The first imaging device 300 is disposed on the optical axis of the device under test 20 and is used to perform MTF measurements along the optical axis. Multiple second imaging devices 400 are disposed around the first imaging device 300 and are used to perform off-axis MTF measurements. Therefore, by setting up the first imaging device 300 and the second imaging device 400, MTF measurements can be performed at different field positions.

[0061] In some embodiments of this application, both the first imaging device 300 and the second imaging device 400 are cameras. Thus, the first imaging device 300 and the second imaging device 400 can receive images projected by the device under test 20.

[0062] In some embodiments of this application, the first polarizer 500 is rotatably connected to the imaging device, allowing it to rotate around the optical axis of the imaging device. During measurement, the rotation angle of the first polarizer 500 can be adjusted in real time, and the imaging device receives the image projected by the device under test 20 at each moment. Since the image is clearest when the emitted light axis is aligned with the polarizer, obtaining the rotation angle of the first polarizer 500 corresponding to the clearest image yields the polarization direction of the emitted light at the corresponding field position. For example, Figure 4 Image 30a is shown when the output optical axis is aligned with the first polarizer 500. Figure 5 Image 30b illustrates the situation when the output optical axis is not aligned with the first polarizer 500, and the two images show a significant difference in sharpness.

[0063] In some embodiments of this application, such as Figure 2 , Figure 3 As shown, the polarized light source assembly 200 includes a backlight 210, a light source pattern plate 220, and a second polarizer 230. Specifically, the light source pattern plate 220 is disposed on the light-emitting side of the backlight 210, and the light source pattern plate 220 is provided with a plurality of light-transmitting holes 221, which are combined to form a preset pattern. The second polarizer 230 is disposed on the side of the light source pattern plate 220 opposite to the backlight 210. The light emitted from the backlight 210 passes sequentially through the light source pattern plate 220 and the second polarizer 230 to form a polarized light pattern.

[0064] Furthermore, the polarized light source assembly 200 may also include a homogenizer 240, which is disposed between the backlight 210 and the light source pattern plate 220. The homogenizer 240 can homogenize the light emitted from the backlight 210, resulting in a more uniform light energy distribution. This helps to improve the uniformity of energy distribution of the polarized light pattern emitted by the polarized light source assembly 200 at various locations.

[0065] Furthermore, the second polarizer 230 can be any one of a linear polarizer, a circular polarizer, and an elliptic polarizer, and the specific type can be selected according to actual needs.

[0066] Furthermore, the first polarizer 500 can be any one of a circular polarizer, a linear polarizer, and an elliptic polarizer, and the specific type can be selected according to actual needs.

[0067] In some embodiments of this application, the MTF testing device 10 further includes a processing unit (not shown in the figures). The processing unit is electrically connected to each imaging device, and each imaging device is configured to transmit image data to the processing unit. The processing unit is configured to obtain the modulation transfer function (MTF) based on the image data. The processing unit may be a controller storing an MTF calculation program. After receiving the image projected by the device under test 20, each imaging device transmits the corresponding image data to the processing unit. The processing unit executes the MTF calculation program based on the received image data to obtain the modulation transfer function (MTF).

[0068] It is understood that the MTF calculation method is a relatively mature existing method, therefore, this application will not describe it in detail.

[0069] An embodiment of the second aspect of this application provides an MTF testing method, such as... Figure 6 As shown, the MTF testing method includes the following steps:

[0070] Step S101: Fix the device under test 20 to the sample holder 100. The device under test 20 includes a polarization system 21.

[0071] Step S102: Project a polarized light pattern onto the device under test 20 using the polarized light source assembly 200;

[0072] Step S103: Provide multiple imaging devices, each imaging device having a first polarizer 500 at its receiving end, and receive the image projected by the device under test 20 through the multiple imaging devices;

[0073] Step S104: Obtain the modulation transfer function (MTF) based on the image data.

[0074] The MTF testing method in this embodiment utilizes a polarized light source assembly 200 to provide a polarized light pattern to the device under test 20. The polarized light pattern passes through the polarized light system 21 of the device under test 20 to form a projected image. This projected image passes through a first polarizer 500 and is received by an imaging device. Based on the image data received by the imaging device, the MTF of the polarized light system 21 can be further obtained. Therefore, the MTF testing method in this embodiment can effectively measure the MTF of the polarized light system 21.

[0075] In some embodiments of this application, the first polarizer 500 is rotatably connected to the imaging device, allowing it to rotate around the optical axis of the imaging device. During measurement, the rotation angle of the first polarizer 500 can be adjusted in real time, and the imaging device receives the image projected by the device under test 20 at each moment. Since the image is clearest when the emitted light axis is aligned with the polarizer, obtaining the rotation angle of the first polarizer 500 corresponding to the clearest image yields the polarization direction of the emitted light at the corresponding field position. For example, Figure 4 Image 30a is shown when the output optical axis is aligned with the first polarizer 500. Figure 5 Image 30b illustrates the situation when the output optical axis is not aligned with the first polarizer 500, and the two images show a significant difference in sharpness.

[0076] In some embodiments of this application, the step of projecting a polarized light pattern onto the device under test 20 using the polarized light source assembly 200 specifically includes:

[0077] A polarized light source assembly 200 including a backlight 210, a light source pattern board 220, and a second polarizer 230 (see reference) Figure 2 A polarized light pattern is projected onto the device under test 20. The light source pattern plate 220 is disposed on the light-emitting side of the backlight 210. The light source pattern plate 220 is provided with multiple light-transmitting holes 221, and the multiple light-transmitting holes 221 are combined to form a preset pattern.

[0078] With this configuration, the light emitted from the backlight 210 passes through the light source pattern plate 220 and the second polarizer 230 in sequence, thus forming a polarized light pattern.

[0079] Furthermore, the polarized light source assembly 200 may also include a homogenizer 240, which is disposed between the backlight 210 and the light source pattern plate 220. The homogenizer 240 can homogenize the light emitted from the backlight 210, resulting in a more uniform light energy distribution. This helps to improve the uniformity of energy distribution of the polarized light pattern emitted by the polarized light source assembly 200 at various locations.

[0080] In some embodiments of this application, the step of providing multiple imaging devices specifically includes:

[0081] A first imaging device 300 and two or more second imaging devices 400 are provided, wherein the first imaging device 300 is disposed on the optical axis of the device under test 20, and the second imaging devices 400 are disposed around the first imaging device 300.

[0082] In this embodiment, the first imaging device 300 is disposed on the optical axis of the device under test 20 for performing MTF measurements along the optical axis. Multiple second imaging devices 400 are disposed around the first imaging device 300 for performing off-axis MTF measurements. Thus, by configuring the first imaging device 300 and the second imaging device 400, MTF measurements can be performed at different field positions.

[0083] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0084] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. An MTF testing device for measuring the MTF of a device under test, wherein the device under test includes a polarized light system, characterized in that, The MTF testing equipment includes: A sample holder is used to fix the device under test; A polarized light source assembly is used to project a polarized light pattern onto the device under test; Multiple imaging devices, wherein the imaging devices are used to receive images projected by the device under test; and Multiple first polarizers are provided, and the multiple first polarizers and the multiple imaging devices are respectively arranged in a one-to-one correspondence. The first polarizer is disposed at the receiving end of the corresponding imaging device. The first polarizer is rotatably connected to the imaging device so that the first polarizer can rotate around the optical axis of the imaging device. The polarized light source component includes: Backlight; A light source graphic board, wherein the light source graphic board is disposed on the light-emitting side of the backlight, and the light source graphic board is provided with multiple light-transmitting holes, the multiple light-transmitting holes being combined to form a preset pattern; and A second polarizer is disposed on the side of the light source graphic plate opposite to the backlight.

2. The MTF testing equipment according to claim 1, characterized in that, The plurality of imaging devices includes a first imaging device and a second imaging device; The first imaging device is one in number and is positioned on the optical axis of the device under test; The number of the second imaging devices is two or more, and the second imaging devices are arranged around the first imaging device.

3. The MTF testing equipment according to claim 1, characterized in that, The polarized light source assembly also includes a light homogenizer, which is disposed between the backlight and the light source graphic board.

4. The MTF testing equipment according to claim 1, characterized in that, The second polarizer is a linear polarizer, a circular polarizer, or an elliptic polarizer; And / or, the first polarizer is a circular polarizer, a linear polarizer, or an elliptic polarizer.

5. The MTF testing equipment according to claim 1, characterized in that, The MTF testing equipment further includes a processing unit, which is electrically connected to each of the imaging devices. Each of the imaging devices is configured to transmit image data to the processing unit, and the unit is configured to obtain the modulation transfer function (MTF) based on the image data.

6. An MTF testing method, characterized in that, The MTF testing equipment described in any one of claims 1-5 is used, and the MTF testing method includes: The device under test is fixed to the sample holder, and the device under test includes a polarization system; A polarized light pattern is projected onto the device under test using a polarized light source assembly; Multiple imaging devices are provided, and each imaging device is equipped with a first polarizer at its receiving end, so that the images projected by the device under test are received by the multiple imaging devices. Obtain the modulation transfer function (MTF) from the image data.

7. The MTF testing method according to claim 6, characterized in that, The step of projecting a polarized light pattern onto the device under test using a polarized light source assembly includes: A polarized light pattern is projected onto the device under test using a polarized light source assembly including a backlight, a light source pattern board, and a second polarizer. The light source pattern board is located on the light-emitting side of the backlight and has multiple light-transmitting holes that are combined to form a preset pattern.

8. The MTF testing method according to claim 6, characterized in that, The first polarizer is rotatably connected to the imaging device so that the first polarizer can rotate about the optical axis of the imaging device.

Images