A high-precision phase deflectometry measurement system and method

Abstract

The application relates to the technical field of specular object surface measurement, in particular to a high-precision phase deflectometry measurement system and method. The system comprises a display screen used for displaying a test image, wherein the display test image is a structured light fringe image; an image acquisition device used for acquiring a mirror image of the display test image formed by a to-be-measured object surface; and a light homogenizing sheet fixedly arranged on the light exit side of the display screen, wherein the flatness of the light homogenizing sheet is less than that of the display screen. The application has at least the following beneficial effects: the light homogenizing sheet arranged in front of the display screen can improve the influence degree of the flatness of the display on the final measurement precision and reduce the error existing in the measurement result, thereby improving the measurement precision of phase deflectometry on large-size to-be-measured objects.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of specular object surface measurement, and in particular to a high-precision phase deflectometry measurement system and method. BACKGROUND

[0002] Phase deflectometry is a visual measurement method for realizing non-contact measurement of an optical surface by projecting a structured fringe on a display. The specific working principle is as follows: a sinusoidal fringe image is projected onto a measured object surface, a camera is used to shoot the sinusoidal fringe image that is modulated by the measured object surface and is curved, the curved fringe is demodulated to obtain a phase, and the phase is converted into the height of the measured object surface. In this way, measurement is performed.

[0003] The display on the market is basically a consumer-grade display. However, since the consumer has a low requirement for the screen flatness of the display in daily use, the manufacturer has a low requirement for the flatness in production due to cost and other considerations. Generally, the larger the display size of the display is, the worse the flatness is. Meanwhile, the flatness consistency of the screens in the same batch is low. In the scene of phase deflectometry measurement, in order to measure a measured object with a larger surface area, a display with a larger display size is correspondingly arranged to project a structured fringe. However, since the flatness of the display has a profound influence on the final measurement accuracy, the result measured by the method finally exists a large error. Thus, the accuracy of phase deflectometry for measuring a large-size measured object is reduced. SUMMARY

[0004] Therefore, the present application provides a high-precision phase deflectometry measurement system, which at least partially solves the problem of low accuracy of phase deflectometry for measuring a large-size measured object in the prior art.

[0005] According to one aspect of the present application, a high-precision phase deflectometry measurement system is provided, comprising:

[0006] A display screen is configured to display a test image, and the test image is a structured light fringe image.

[0007] An image acquisition device is configured to acquire a mirror image of the test image formed on the surface of the measured object.

[0008] An optical homogenization plate is fixedly arranged on the light-emitting side of the display screen, and the flatness of the optical homogenization plate is less than that of the display screen.

[0009] Further, the system further comprises:

[0010] An image generation device is electrically connected to the display screen, and the image generation device is configured to generate the test image and send the test image to the display screen.

[0011] Further, the image acquisition device is at least one.

[0012] Further, the display screen is at least one.

[0013] Further, the image acquisition device is a CCD camera.

[0014] Further, the material of the light uniformizing sheet is glass, quartz or resin, etc.

[0015] Further, the material of the light uniformizing sheet is PVC.

[0016] Further, the display screen is arranged in parallel with the light uniformizing sheet.

[0017] Further, the light uniformizing sheet comprises a light uniformizing sheet with frosted effect on one side, a light uniformizing sheet with frosted effect on both sides, or a light uniformizing sheet with frosted effect on the whole inside.

[0018] According to another aspect of the present application, there is also provided a high-precision phase deflectometry measurement method, which uses the above high-precision phase deflectometry measurement system to measure an object with a reflective surface.

[0019] The present application has at least the following beneficial effects:

[0020] By arranging a light uniformizing sheet in front of the display screen, the light emitted by the screen is first projected on the light uniformizing sheet and then projected on the surface of the measured object by the light uniformizing sheet.

[0021] In addition, since the light uniformizing sheet contains a substance or structure capable of causing diffuse reflection of light, such as a frosted structure on the surface, when the light enters the light uniformizing sheet, it will be diffusely reflected and then uniformly emitted from the exit surface. BRIEF DESCRIPTION OF DRAWINGS

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of a high-precision phase deflection measurement system according to an embodiment of this application.

[0024] Figure 2 This is a schematic diagram of the measurement results of a phase deflection measurement system without a homogenizer in another embodiment of this application.

[0025] Figure 3 This is a schematic diagram of the measurement results of a phase deflection measurement system with a homogenizer installed in another embodiment of this application.

[0026] Attached Figure

[0027] 1. Display screen; 2. Image generation device; 3. Image acquisition device; 4. Object to be tested; 5. Light stabilizer. Implementation

[0028] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0029] It should be noted that, unless otherwise specified, the following embodiments and features can be combined with each other. Furthermore, all other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without inventive effort are within the scope of protection of this disclosure.

[0030] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this disclosure, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0031] According to one aspect of the invention, such as Figure 1 As shown, a high-precision phase deflection measurement system is provided, the system comprising:

[0032] A display screen 1 is configured to display a test image, and the test image is a structured light fringe image.

[0033] Specifically, the display screen 1 can be a screen of a consumer-grade display that is commercially available on the market. Generally, the larger the display size of the display screen 1, the worse the flatness of the display screen 1. Specifically, for a 27-inch display, the flatness is usually about 1 mm. The flatness error will result in a low flatness of the projected test image, which will directly affect the final measurement result.

[0034] However, the display screen 1 has a greater selection advantage due to its high display quality, easy availability and low cost.

[0035] Further, the system further comprises:

[0036] An image generation device 2 is electrically connected to the display screen 1. The image generation device 2 is configured to generate a test image and send the test image to the display screen 1.

[0037] The image generation device can be an existing device with image generation capability, such as a computer, a tablet computer, a workstation, etc. Correspondingly, the generated test image can also be a structured fringe pattern used in the existing phase deflectometry.

[0038] An image acquisition device 3 is configured to acquire a mirror image of the test image formed on the surface of the object 4 to be measured.

[0039] Preferably, the image acquisition device 3 can be a CCD (Charge Coupled Device) camera.

[0040] A light homogenizing sheet 5 is fixedly arranged on the light emitting side of the display screen 1. The flatness of the light homogenizing sheet 5 is less than the flatness of the display screen 1.

[0041] Further, the display screen 1 and the light homogenizing sheet 5 are arranged in parallel. The minimum distance β between the display screen 1 and the light homogenizing sheet 5 satisfies the following condition: β ∈ [0 mm, 10 mm]. More preferably, β = 0 mm.

[0042] For the positional relationship between the light homogenizing sheet 5 and the display screen 1, it is generally better that the light homogenizing sheet 5 is closer to the display screen 1 and the parallelism between the light homogenizing sheet 5 and the display screen 1 is higher. Because, after the light is emitted from the screen, it is deflected by various media to form a light with a divergence angle. Thus, when the light is incident on the light homogenizing sheet 5 again, it will be refracted in the light homogenizing sheet 5. Correspondingly, the image will be deformed due to the refraction, which will affect the final calculation accuracy. Therefore, in order to minimize the error caused by refraction, the light homogenizing sheet 5 needs to be arranged as close to the display screen 1 as possible.

[0043] The light uniforming sheet 5 can be fixed on the light emitting side of the display screen 1 by means of adhesion or clamping, etc. For example, a limiting frame can be arranged, and then the limiting frame can be fixed on the display by means of adhesion or screws, and the light uniforming sheet is clamped between the limiting frame and the display. This fixing mode can fix the light uniforming sheet 5 by uniformly clamping the edges of the light uniforming sheet 5. Thus, the deformation of the light uniforming sheet 5 during fixing can be reduced, and the flatness can be further ensured.

[0044] As another possible embodiment of the present application, the image acquisition device 3 is at least one. Further, the display screen 1 is at least one.

[0045] According to the above configuration between the number of the image acquisition device 3 and the display screen 1, the system can be used in single camera single screen phase deflectometry, multi-camera single screen phase deflectometry, single camera multi-screen phase deflectometry, and multi-camera multi-screen phase deflectometry. The adaptability of the system structure is higher, and the application range is wider.

[0046] As another possible embodiment of the present application, the material of the light uniforming sheet 5 is glass, quartz or resin, etc. Further, the material of the light uniforming sheet 5 is PVC.

[0047] The above materials can all play the effect of light uniforming. The light uniforming sheet 5 made of quartz and glass has better flatness ensured by the processing technology. The light uniforming sheet 5 made of resin has lower use cost.

[0048] Further, the light uniforming sheet 5 includes the light uniforming sheet 5 with frosted effect on one side, or the light uniforming sheet 5 with frosted effect on both sides, or the light uniforming sheet 5 with frosted effect on the whole inside. The thickness λ of the light uniforming sheet 5 satisfies the following condition: λ∈[20μm, 5cm].

[0049] In order to reduce the error caused by refraction, the frosted effect can be arranged at different positions of the light uniforming sheet 5. Thus, the light can be diffused, and the emission can be more uniform.

[0050] Since the light is refracted in the light uniforming sheet 5, and the light path of the refracted light is increased, the deformation of the image formed on the light emitting side of the light uniforming sheet 5 is also magnified. Therefore, in order to reduce the error caused by this factor, the thickness of the light uniforming sheet 5 should be as small as possible, i.e. the propagation path of the refracted light should be as small as possible. However, if the light uniforming sheet 5 is too thin, the strength of the light uniforming sheet 5 will be low, and thus the light uniforming sheet 5 is easy to deform or even break during fixing. Therefore, generally, the thickness of the light uniforming sheet 5 should be increased with the increase of the area of the light uniforming sheet 5.

[0051] Preferably, λ = 200 μm or λ = 500 μm. When the area of the light uniformity sheet 5 is 25 to 30 inches, the thickness of the light uniformity sheet 5 is 200 μm, which has a better error elimination effect. When the area of the light uniformity sheet 5 is 30 to 50 inches, the thickness of the light uniformity sheet 5 is 500 μm, which has a better error elimination effect.

[0052] Specifically, an existing 27-inch consumer display screen is selected as the display screen 1. The flatness of the display screen 1 is 1.0 mm measured by a three-coordinate measuring machine. Then, the light uniformity sheet 5 made of organic glass with a flatness of 0.2 mm is cut to the size of the display area and uniformly covers the surface of the display. The high-precision phase deflectometry measurement system in the application is formed by using the light uniformity sheet 5. At the same time, a control group is set up, which is different from the experimental group in that it lacks the light uniformity sheet 5.

[0053] Then, the same HUD (head-up display) mirror mold is measured by using the control group and the experimental group, and the corresponding measurement results are shown in Figure 2 and Figure 3 As can be seen from the figures, before the light uniformity sheet is added, the peak-to-valley value of the surface shape measurement error is 52 μm; after the light uniformity sheet is added by using the technology of the application, the flatness of the display light emitting surface is converted from 1.0 mm of the display itself to 0.2 mm of the surface layer of the organic glass light uniformity sheet 5. After improving the flatness of the display, the peak-to-valley value of the surface shape measurement error is reduced to 8 μm, which is obviously improved.

[0054] According to another aspect of the application, a high-precision phase deflectometry measurement method is also provided, which uses the high-precision phase deflectometry measurement system to measure an object with a reflective surface.

[0055] The beneficial effects of the method are mainly brought by the high-precision phase deflectometry measurement system, which will not be repeated here.

[0056] The above is only a specific embodiment of the application, but the protection scope of the application is not limited thereto, and any changes or replacements that can be easily thought of by those skilled in the art within the technical range disclosed by the application should be covered within the protection scope of the application. Therefore, the protection scope of the application should be subject to the protection scope of the claims.

Claims

1. A high precision phase deflectometry measurement system, characterized in that, The application relates to a high-precision phase deflection measurement system. The system comprises: a display screen for displaying a test image, wherein the display test image is a structured light fringe image; an image acquisition device for acquiring a mirror image of the display test image formed on the surface of a measured object; and a light homogenizing sheet fixedly arranged on the light emitting side of the display screen, wherein the flatness of the light homogenizing sheet is less than that of the display screen, the display screen and the light homogenizing sheet are arranged in parallel, and the minimum distance beta between the display screen and the light homogenizing sheet satisfies the condition: beta is in the range of 0mm to 10mm. The light homogenizing sheet contains a substance or structure capable of causing light to be diffused, so that the light can be prevented from being refracted obviously in the light homogenizing sheet, thereby reducing the refractive deviation introduced to phase information. After the light is emitted from the screen, the light is deflected by various media to form a light with divergence, so that the light is refracted in the light homogenizing sheet when the light enters the light homogenizing sheet.

2. A high precision phase deflectometry measurement system according to claim 1, characterized in that, The system further comprises: an image generation device electrically connected with the display screen, wherein the image generation device is used for generating the display test image and sending the display test image to the display screen.

3. The high precision phase deflectometry measurement system of claim 1, wherein, The image acquisition device is at least one.

4. A high precision phase deflectometry measurement system according to claim 3, wherein, The display screen is at least one.

5. The high precision phase interferometry measurement system of claim 1, wherein, The image acquisition device is a CCD camera.

6. The high precision phase interferometry measurement system of claim 1, wherein, The material of the light homogenizing sheet is organic glass, quartz or resin.

7. The high precision phase interferometry measurement system of claim 1, wherein, The light homogenizing sheet comprises a light homogenizing sheet with a frosted effect on a single side, a light homogenizing sheet with a frosted effect on both sides or a light homogenizing sheet with a frosted effect on the whole inside, and the thickness lambda of the light homogenizing sheet satisfies the condition: lambda is in the range of 20um to 5cm.

8. A high precision phase deflectometry measurement system according to claim 6, wherein, The material of the light homogenizing sheet is PVC.

9. A high precision phase deflectometry measurement method, characterized in that, The high-precision phase deflection measurement system is used for measuring an object with a reflective surface.

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