Reflective object measuring method, device, equipment and medium

Abstract

The invention discloses a method, a device and equipment for measuring a reflective object and a medium. The method comprises the following steps of: obtaining second exposure time of a camera according to a group of first deformed fringe patterns acquired by the camera and a time slice principle; according to a group of second deformed fringe patterns and a group of third deformed fringe patterns collected by the camera and a Fourier slice theorem, determining a receiving range of each pixel of the camera to the pixels of the projector; a single-pixel imaging technology is used for the second deformed fringe pattern and the third deformed fringe pattern to obtain a reconstructed light transfer coefficient; determining direct illumination points of pixels of the projector one by one according to the reconstructed light transfer coefficient and a depth constraint positioning method; and collecting all the direct illumination points to complete the reconstruction of the image of the reflective object. According to the exposure method, each image does not need to be exposed independently, and image details of a bright part and a dark part can be balanced at the same time, so that the types of exposure time are reduced, the image acquisition efficiency is improved, and meanwhile, three-dimensional shape reconstruction of a low-quality image under low illumination intensity is realized.

Description

Technical Field

[0001] The present invention relates to the field of three-dimensional imaging technology, and in particular to a method, device, equipment and medium for measuring a reflective object. Background Art

[0002] With the development of digital information technology, three-dimensional imaging technology is widely used in various fields. Three-dimensional imaging technology is a new technology based on computer vision and image processing. It is a method of obtaining the size and shape information of an object by non-contact measurement of its three-dimensional morphology. However, traditional three-dimensional imaging systems generally require that the surface of the object to be measured is diffusely reflective. For objects with highly reflective surfaces, due to the high reflective characteristics, the image will be overexposed, resulting in data holes, or the stripes will be too dark due to underexposure, causing measurement errors in phase calculation.

[0003] The multiple exposure method avoids image saturation and achieves a higher signal-to-noise ratio by fusing images collected at different exposure times into one image. The core of the multiple exposure method is to collect a series of images containing information of areas with different reflectivity by adjusting the exposure time. Images taken at low exposure times can capture useful information of high reflectivity areas and avoid loss of details in these areas due to overexposure. Images taken at high exposure times can contain useful information from low reflectivity surface areas, ensuring that these areas do not appear blurred due to underexposure. By merging these images into a set of high dynamic range images, the brightest non-saturated intensity at each pixel can be selected to reconstruct a complete and clear three-dimensional morphology.

[0004] Traditional multiple-exposure fringe projection technology has the following defects: in order to obtain images with different exposure levels, each image needs to be exposed separately with a different exposure time, which limits the choice of exposure time; it is difficult to balance the image details of bright and dark areas when processing high-contrast scenes; low-light intensity projection destroys the texture of the reconstructed surface, and the image becomes dark and too noisy, which makes traditional fringe projection enhancement technology almost impossible to apply. Summary of the invention

[0005] The present invention provides a method, device, equipment and medium for measuring reflective objects, which does not require separate exposure of each image and can balance the image details of bright and dark parts at the same time, thereby reducing the types of exposure time, improving image acquisition efficiency, and realizing three-dimensional morphology reconstruction of low-quality images under low light intensity.

[0006] In a first aspect, an embodiment of the present invention provides a method for measuring a reflective object, which is implemented by using a measuring device for a reflective object, wherein the measuring device for a reflective object includes: a projector and a camera;

[0007] The method for measuring the reflective object comprises:

[0008] Control the projector to sequentially project a group of Fourier sinusoidal fringe patterns with an exposure time of a first exposure time onto the surface of the reflective object, and control the camera to sequentially collect a group of first deformed fringe patterns formed on the surface of the reflective object; wherein a group of the Fourier sinusoidal fringe patterns includes four Fourier sinusoidal fringe patterns, the fringe orders of the four Fourier sinusoidal fringe patterns are all the same, and the initial phases are all different; the Fourier sinusoidal fringe patterns include Fourier sinusoidal horizontal fringe patterns and Fourier sinusoidal vertical fringe patterns;

[0009] Obtaining a second exposure time of the camera according to a set of the first deformed fringe patterns collected by the camera and a time slice principle; wherein the second exposure time is less than the first exposure time;

[0010] Control the projector to sequentially project five groups of the Fourier sinusoidal horizontal fringe patterns and five groups of the Fourier sinusoidal vertical fringe patterns, each group having an exposure time of the second exposure time, onto the surface of the reflective object, and control the camera to sequentially collect five groups of the second deformed fringe patterns and five groups of the third deformed fringe patterns formed on the surface of the reflective object;

[0011] Determine a receiving range of each pixel of the camera for a pixel of the projector according to a set of the second deformed fringe patterns and a set of the third deformed fringe patterns collected by the camera and the Fourier slice theorem;

[0012] Obtaining a reconstructed light transfer coefficient using a single pixel imaging technique on the second deformed fringe pattern and the third deformed fringe pattern;

[0013] Determine the direct illumination points of the pixels of the projector one by one according to the reconstructed light transfer coefficient and the depth-constrained positioning method;

[0014] All the direct illumination points are collected to complete the reconstruction of the reflective object image.

[0015] In a second aspect, an embodiment of the present invention further provides a measuring device for a reflective object, comprising:

[0016] An image projection and acquisition module, used to control the projector to sequentially project a group of Fourier sinusoidal fringe patterns with an exposure time of a first exposure time onto the surface of the reflective object, and simultaneously control the camera to sequentially acquire a group of first deformed fringe patterns formed on the surface of the reflective object; wherein a group of the Fourier sinusoidal fringe patterns includes four Fourier sinusoidal fringe patterns, the fringe orders of the four Fourier sinusoidal fringe patterns are all the same, and the initial phases are all different; the Fourier sinusoidal fringe patterns include Fourier sinusoidal horizontal fringe patterns and Fourier sinusoidal vertical fringe patterns;

[0017] A second exposure time acquisition module, used for obtaining a second exposure time of the camera according to a set of the first deformed fringe patterns collected by the camera and a time slice principle; wherein the second exposure time is less than the first exposure time;

[0018] The image projection and acquisition module is further used to control the projector to sequentially project five groups of the Fourier sinusoidal horizontal fringe patterns and five groups of the Fourier sinusoidal vertical fringe patterns, each group of which has an exposure time of the second exposure time, onto the surface of the reflective object, and simultaneously control the camera to sequentially acquire five groups of the second deformed fringe patterns and five groups of the third deformed fringe patterns formed on the surface of the reflective object;

[0019] a receiving range determining module, configured to determine a receiving range of each pixel of the camera to a pixel of the projector according to a set of the second deformed fringe patterns and a set of the third deformed fringe patterns collected by the camera and the Fourier slice theorem;

[0020] a reconstructed light transfer coefficient acquisition module, configured to obtain a reconstructed light transfer coefficient by using a single pixel imaging technique on the second deformed fringe pattern and the third deformed fringe pattern;

[0021] A direct illumination point acquisition module, used for determining the direct illumination points of the pixels of the projector one by one according to the reconstructed light transfer coefficient acquired by the reconstructed light transfer coefficient acquisition module and a depth constraint positioning method;

[0022] The reflective object reconstruction module is used to collect all the direct illumination points acquired by the direct illumination point acquisition module to complete the reconstruction of the reflective object image.

[0023] In a third aspect, an embodiment of the present invention further provides a reflective object measuring device, the reflective object measuring device comprising: a projector, a camera, at least one processor; and a memory in communication connection with the at least one processor;

[0024] The memory stores a computer program executable by the at least one processor, and the computer program is executed by the at least one processor so that the at least one processor can execute the method for measuring reflective objects as described in any embodiment of the first aspect.

[0025] In a fourth aspect, an embodiment of the present invention further provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a processor to implement the method for measuring a reflective object as described in any embodiment of the first aspect when executed.

[0026] The embodiments of the present invention provide a method, device, equipment and medium for measuring reflective objects. The time slicing technology is used to eliminate the need to expose each image separately, thereby reducing the types of exposure time and improving image acquisition efficiency. At the same time, short exposure time and low light intensity are used to avoid overexposure of the image. On the basis of time slicing, the direct illumination point and the indirect illumination point on the projector are separated through light transfer coefficient analysis, which effectively overcomes the problem that low-quality images cannot be used and realizes three-dimensional reconstruction of low-quality images under low light intensity. The embodiments of the present invention do not need to expose each image separately, and the exposure method can balance the image details of the bright and dark parts at the same time, thereby reducing the types of exposure time, improving image acquisition efficiency, and realizing three-dimensional morphology reconstruction of low-quality images under low light intensity.

[0027] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 A flow chart of a method for measuring a reflective object provided by an embodiment of the present invention;

[0030] Figure 2 A schematic diagram of a set of Fourier sinusoidal horizontal fringe patterns provided by an embodiment of the present invention;

[0031] Figure 3 A schematic diagram of a set of Fourier sinusoidal vertical fringe images provided by an embodiment of the present invention;

[0032] Figure 4 A flow chart of another method for measuring a reflective object provided by an embodiment of the present invention;

[0033] Figure 5 A schematic diagram of the structure of a reflective object measuring device provided by an embodiment of the present invention;

[0034] Figure 6 A schematic structural diagram of a reflective object measuring device provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0036] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0037] Figure 1 A flow chart of a method for measuring a reflective object provided by an embodiment of the present invention, wherein the method for measuring a reflective object is implemented by using a measuring device for a reflective object, and the measuring device for a reflective object includes: a projector and a camera. Figure 1 , the method for measuring a reflective object comprises the following steps:

[0038] S110, controlling the projector to sequentially project a group of Fourier sinusoidal fringe patterns with an exposure time of a first exposure time onto the surface of the reflective object, and controlling the camera to sequentially collect a group of first deformed fringe patterns formed on the surface of the reflective object.

[0039] Wherein, a set of Fourier sinusoidal fringe patterns includes four Fourier sinusoidal fringe patterns, the fringe orders of the four Fourier sinusoidal fringe patterns are the same, and the initial phases are different. The Fourier sinusoidal fringe patterns include Fourier sinusoidal horizontal fringe patterns and Fourier sinusoidal vertical fringe patterns. Exemplarily, Figure 2 A schematic diagram of a set of Fourier sinusoidal horizontal fringe patterns provided by an embodiment of the present invention, Figure 3 A schematic diagram of a group of Fourier sinusoidal vertical fringe patterns provided by an embodiment of the present invention. It should be noted that the first exposure time can be freely set by the user to make the Fourier sinusoidal fringe pattern produce overexposure.

[0040] Optionally, the Fourier sinusoidal horizontal fringe pattern and the Fourier sinusoidal vertical fringe pattern satisfy: Among them, P φis the Fourier sinusoidal horizontal fringe pattern or the Fourier sinusoidal vertical fringe pattern, (u′, ν′) is the pixel of the projector, (k, l) is the spatial frequency of the camera, (M, N) is the resolution of the camera, φ is the initial phase of the Fourier sinusoidal horizontal fringe pattern or the Fourier sinusoidal vertical fringe pattern, and the values ​​of φ include 0, π / 2, π, and 3π / 2; a is the average intensity of the Fourier sinusoidal horizontal fringe pattern or the Fourier sinusoidal vertical fringe pattern, and b is the contrast of the Fourier sinusoidal horizontal fringe pattern or the Fourier sinusoidal vertical fringe pattern. The fringe orders of the five groups of Fourier sinusoidal horizontal fringe patterns are 8, 16, 24, 32, and 40 respectively; the initial phases of the four Fourier sinusoidal horizontal fringe patterns in each group are 0, π / 2, π, and 3π / 2 respectively. The fringe orders of the five groups of Fourier sinusoidal vertical fringe images are 8, 16, 24, 32, and 40, respectively; the initial phases of the four Fourier sinusoidal vertical fringe images in each group are 0, π / 2, π, and 3π / 2, respectively.

[0041] S120: Obtain a second exposure time of the camera according to a set of first deformed fringe patterns collected by the camera, wherein the second exposure time is shorter than the first exposure time.

[0042] It should be noted that after the grayscale values ​​of a set of first deformed fringe images collected by the camera are superimposed pixel by pixel and divided by 4, the number of pixels of each grayscale value can be obtained. The number of pixels of each grayscale value can be aggregated to obtain a histogram, the horizontal axis of the histogram is the grayscale value (0-255), and the vertical axis is the number of pixels (that is, how many pixels are this grayscale value). The histogram can help analyze the grayscale changes in the image, and then help determine the optimal binarization grayscale threshold (threshold level). If the grayscale value of the object and the background are obviously contrasted, the grayscale histogram will contain a bimodal histogram, that is, there will generally be two peaks in the histogram, which are the foreground and background of the image. The foreground causes the number of grayscale values ​​in a certain grayscale interval to increase sharply, which will produce a peak. Similarly, the background causes the number of grayscale values ​​in another grayscale interval to increase sharply, which will produce another peak. The valley between the two peaks corresponds to a relatively small number of pixels near the edge of the object. The minimum value between these two peaks is generally the dividing point of the optimal binarization, and the foreground and background can be well separated by this dividing point. In an embodiment of the present invention, the horizontal coordinate of the first valley of the histogram is defined as the first grayscale value, and the ratio of the maximum grayscale value (the grayscale value is 255) to the first grayscale value is defined as the optimal number of acquisition groups when the exposure time is the first exposure time. The first exposure time is used to project the optimal number of Fourier sinusoidal fringe patterns, and at this time, the exposure time of each group of Fourier sinusoidal fringe patterns is shorter. The short exposure time is defined as the second exposure time of the camera. The second exposure time is used to acquire a group of Fourier sinusoidal fringe patterns, which can balance the exposure of the image details of the bright and dark parts at the same time and improve the image acquisition efficiency.

[0043] S130, controlling the projector to project five groups of Fourier sinusoidal horizontal fringe patterns and five groups of Fourier sinusoidal vertical fringe patterns, each with an exposure time of the second exposure time, onto the surface of the reflective object in sequence, and at the same time controlling the camera to sequentially collect five groups of second deformed fringe patterns and five groups of third deformed fringe patterns formed on the surface of the reflective object.

[0044] Among them, in an embodiment of the present invention, time slicing technology is used to set the total exposure time of a group of Fourier sinusoidal fringe patterns as the second exposure time, thereby eliminating the need to expose each image separately, reducing the types of exposure times and improving image acquisition efficiency.

[0045] S140, determining a receiving range of each pixel of the camera to a pixel of the projector according to a set of second deformed fringe patterns and a set of third deformed fringe patterns collected by the camera and the Fourier slice theorem.

[0046] It should be noted that, based on a set of second deformed fringe patterns and a set of third deformed fringe patterns collected by the camera, the Fourier slicing principle can be used to locate the receiving range of each pixel of the camera to the pixel of the projector. Specifically, first, according to the complex number conversion rule of the four-step phase-shift projection mode, the first Fourier coefficient of the Fourier sinusoidal horizontal fringe pattern and the second Fourier coefficient of the Fourier sinusoidal vertical fringe pattern can be obtained. Then, the first Fourier coefficient and the second Fourier coefficient are respectively subjected to a one-dimensional discrete Fourier transform to obtain the first projection function and the second projection function. Finally, the area where the values ​​of the first projection function and the second projection function exceed the preset noise threshold is determined as the receiving range of each pixel of the camera to the pixel of the projector.

[0047] S150, obtaining a reconstructed light transfer coefficient using a single pixel imaging technique for the second deformed fringe pattern and the third deformed fringe pattern.

[0048] Specifically, first, the third Fourier coefficient of the third projection function of the second deformed fringe pattern and the third deformed fringe pattern is obtained according to the Fourier slice theorem, and then the first light transmission coefficient is obtained according to the discrete Fourier inverse transform principle for the third Fourier coefficient, and finally the first light transmission coefficient is introduced into the proportional factor to obtain the reconstructed light transmission coefficient. It can be understood that by repeating the reconstruction process for each pixel of the camera, the reconstructed light transmission coefficient containing the proportional coefficient can be solved. Therefore, the light originally coming from different positions of the light source and mixed together can be decomposed, which provides the premise and basis for three-dimensional reconstruction under global illumination interference.

[0049] S160 , determining the direct illumination points of the pixels of the projector one by one according to the reconstructed light transfer coefficient and the depth constraint positioning method.

[0050] It can be understood that for any camera pixel, two points can be located on the projection plane, and the direct illumination will be located on the connecting line between these two points in the object being measured. In this way, the search area of ​​the direct illumination point can be constrained to a short line, avoiding the ambiguity in the dual-chip positioning and speeding up the search. Specifically, first, the absolute phase is determined using Gray coding and phase shifting methods, and then the length-limiting polar line is determined based on the absolute phase. Finally, the direct illumination point of the projector pixel is determined based on the length-limiting polar line.

[0051] S170, gathering all direct illumination points to complete the reconstruction of the reflective object image.

[0052] The embodiment of the present invention adopts the time slicing technology, which does not need to expose each image separately, reduces the types of exposure time, improves the image acquisition efficiency, and adopts short exposure time and low light intensity to avoid overexposure of the image. On the basis of time slicing, the direct illumination point and the indirect illumination point on the projector are separated through light transfer coefficient analysis, which effectively overcomes the problem that low-quality images cannot be used, and realizes the three-dimensional reconstruction of low-quality images under low light intensity. The embodiment of the present invention does not need to expose each image separately, and the exposure method that can balance the image details of the bright and dark parts at the same time, thereby reducing the types of exposure time, improving the image acquisition efficiency, and realizing the three-dimensional morphology reconstruction of low-quality images under low light intensity.

[0053] Figure 4 A flow chart of a method for measuring a reflective object provided by an embodiment of the present invention, referring to Figure 4 , the method for measuring a reflective object comprises the following steps:

[0054] S410, controlling the projector to sequentially project a group of Fourier sinusoidal fringe patterns with an exposure time of a first exposure time onto the surface of the reflective object, and controlling the camera to sequentially collect a group of first deformed fringe patterns formed on the surface of the reflective object.

[0055] Wherein, a set of Fourier sinusoidal fringe patterns includes four Fourier sinusoidal fringe patterns, the fringe orders of the four Fourier sinusoidal fringe patterns are all the same, and the initial phases are all different; the Fourier sinusoidal fringe patterns include Fourier sinusoidal horizontal fringe patterns and Fourier sinusoidal vertical fringe patterns;

[0056] S420, obtaining a second exposure time of the camera according to a set of first deformed fringe patterns collected by the camera; wherein the second exposure time is shorter than the first exposure time.

[0057] S430, controlling the projector to project five groups of Fourier sinusoidal horizontal fringe patterns and five groups of Fourier sinusoidal vertical fringe patterns, each with an exposure time of the second exposure time, onto the surface of the reflective object in sequence, and at the same time controlling the camera to sequentially collect five groups of second deformed fringe patterns and five groups of third deformed fringe patterns formed on the surface of the reflective object.

[0058] S440, determining a receiving range of each pixel of the camera to a pixel of the projector according to a set of second deformed fringe patterns and a set of third deformed fringe patterns collected by the camera and the Fourier slice theorem.

[0059] S450: Obtain a reconstructed light transfer coefficient using a single pixel imaging technique on the second deformed fringe pattern and the third deformed fringe pattern.

[0060] S460 , determining the direct illumination points of the pixels of the projector one by one according to the reconstructed light transfer coefficient and the depth constraint positioning method.

[0061] S470: Gather all direct illumination points to complete the reconstruction of the reflective object image.

[0062] Optionally, based on the above embodiment, continue to refer to Figure 4 , step S420 includes:

[0063] S421, superimposing the grayscale values ​​of a group of first deformed fringe images collected by the camera pixel by pixel and dividing the result by 4 to obtain the number of pixels for each grayscale value.

[0064] S422: Gather the number of pixels of each gray value into a histogram.

[0065] S423. Define the abscissa of the first valley of the histogram as the first grayscale value.

[0066] S424. Obtain the optimal number of acquisition groups according to the maximum grayscale value and the first grayscale value.

[0067] S425. Obtain a second exposure time of the camera according to the first exposure time and the optimal number of acquisition groups.

[0068] The embodiment of the present invention uses a histogram to analyze the grayscale changes in the image, defines the horizontal coordinate of the first valley of the histogram as the first grayscale value, and defines the ratio of the maximum grayscale value (the grayscale value is 255) to the first grayscale value as the optimal number of acquisition groups when the exposure time is the first exposure time. The first exposure time is used to project the optimal number of Fourier sinusoidal fringe images, and at this time, the exposure time of each group of Fourier sinusoidal fringe images is short. The short exposure time is defined as the second exposure time of the camera, and a group of Fourier sinusoidal fringe images is acquired with the second exposure time, which can balance the exposure of the image details of the bright and dark parts at the same time, and improve the image acquisition efficiency.

[0069] Optionally, based on the above embodiment, step S440 includes:

[0070] S441. Calculate according to the Fourier slice theorem a set of second deformed fringe patterns and a set of third deformed fringe patterns acquired by the camera to obtain a first Fourier coefficient of a first projection function of the second deformed fringe pattern and a second Fourier coefficient of a second projection function of the third deformed fringe pattern.

[0071] Specifically, the first Fourier coefficient Second Fourier coefficient

[0072] in, It is the first response value of the camera when Fourier sinusoidal horizontal fringe pattern is projected onto a reflective object; is the second response value of the camera when the Fourier sinusoidal vertical fringe pattern is projected onto the reflective object, φ is the initial phase of the Fourier sinusoidal horizontal fringe pattern or the Fourier sinusoidal vertical fringe pattern, and the values ​​of φ include 0, π / 2, π and 3π / 2.

[0073] S442, performing one-dimensional discrete Fourier transform on the first Fourier coefficient and the second Fourier coefficient respectively to obtain a first projection function and a second projection function.

[0074] Specifically, the first projection function h x (u′;u,v)=IDFT[H x (k)]; the second projection function is h y (u′;u,v)=IDFT[H y (l)] where IDFT[·] represents one-dimensional discrete Fourier transform, H x (k) is the first Fourier coefficient, H y (l) is the second Fourier coefficient.

[0075] S443: Determine that the area where the values ​​of the first projection function and the second projection function both exceed the preset noise threshold is the receiving range of each pixel of the camera for the pixel of the projector.

[0076] Exemplarily, the preset noise threshold may include 10. The preset noise threshold may be obtained according to the edge detection theorem, and the edge boundary is determined specifically according to the jump of the gray value.

[0077] Optionally, based on the above embodiment, S450 includes:

[0078] S451. Calculate according to the Fourier slice theorem a group of second deformed fringe patterns and a group of third deformed fringe patterns collected by the camera to obtain third Fourier coefficients of the third projection functions of the second deformed fringe patterns and the third deformed fringe patterns.

[0079] Specifically, the third Fourier coefficient Among them, Iφ (u, v; k, l) is the third response value of the camera when the Fourier sinusoidal fringe pattern is projected onto a reflective object, φ is the initial phase of the Fourier sinusoidal horizontal fringe pattern or the Fourier sinusoidal vertical fringe pattern, and the values ​​of φ include 0, π / 2, π, and 3π / 2.

[0080] S452. Obtain the reconstructed light transmission coefficient according to the inverse discrete Fourier transform principle.

[0081] Specifically, the light transmission coefficient is reconstructed in, Stands for two-dimensional inverse discrete Fourier transform.

[0082] It should be noted that the reconstructed light transmission coefficient is the transmission coefficient from any point (u′, ν′) on the projector image plane to a point (u, v) on the camera image plane with a scale factor added.

[0083] In the embodiment of the present invention, the reconstructed light transmission coefficient is obtained for each pixel of the camera, and the light originally coming from different positions of the light source and mixed together can be decomposed, which provides the premise and basis for three-dimensional reconstruction under global illumination interference.

[0084] Optionally, based on the above embodiment, step S460 includes:

[0085] S461. Determine the absolute phase using Gray coding and phase shift method.

[0086] It should be noted that Gray coding is a set of number series, each number is represented by binary, and there is only one bit different between any two numbers. According to the required number of bits (such as 4 bits, 5 bits, etc.), the corresponding Gray coding stripe pattern is generated. These patterns will be projected onto the object to be measured. Use a camera to shoot the deformed Gray code stripe image modulated by the object, and pre-process the collected deformed Gray code stripe image and the second deformed stripe image and the third deformed stripe image provided in the above embodiment, such as denoising, binarization, etc., to extract useful information. The wrapped phase (relative phase) of each pixel is calculated using the phase shift method. The calculated wrapped phase is combined with the corresponding Gray code value, and a specific algorithm (such as a complementary code measure) is used to ensure that the phase shift is correctly unfolded to obtain the absolute phase. Using the absolute phase information obtained, combined with the system calibration parameters and the principle of trigonometric method, the three-dimensional coordinates of the object to be measured can be calculated, thereby realizing three-dimensional reconstruction.

[0087] S462. Determine the length-limiting polar line according to the absolute phase.

[0088] It should be noted that the embodiment of the present invention can measure the precise pixel position P of the camera's pixel directly illuminated in the projection plane according to the Gray coding and phase shift method. p (up , v p ), so that according to the camera pixel point P in the nearest plane p1 (u p1 , v p1 ) and the point P in the farthest plane p2 (u p2 , v p2 ) can eliminate ambiguous candidates. Φ v (u c , v c ) and Φ h (u c , v c ) is, m / f u is the fringe period of the Fourier sinusoidal horizontal fringe pattern, n / f v is the fringe period of the Fourier sinusoidal vertical fringe pattern.

[0089] S463. Determine the direct illumination point of the pixel of the projector according to the length limiting polar line.

[0090] It can be understood that the direct illumination point is located at the point P of the camera pixel in the nearest plane p1 (u p1 , v p1 ) and the point P in the farthest plane p2 (u p2 , v p2 ) listed in the constraint epipolar lines, the search area of ​​the direct illumination point can be constrained to a short line, avoiding the ambiguity in the dual-chip positioning and speeding up the search.

[0091] In summary, the embodiment of the present invention adopts the time slicing technology without exposing each image separately, reduces the types of exposure time, improves the image acquisition efficiency, and adopts short exposure time and low light intensity to avoid overexposure of the image. On the basis of time slicing, the direct illumination point and the indirect illumination point on the projector are separated by light transfer coefficient analysis, which effectively overcomes the problem that low-quality images cannot be used, and realizes the three-dimensional reconstruction of low-quality images under low light intensity. The embodiment of the present invention does not need to expose each image separately, and can simultaneously balance the exposure method of the image details of the bright and dark parts, thereby reducing the types of exposure time, improving the image acquisition efficiency, and realizing the three-dimensional morphology reconstruction of low-quality images under low light intensity. In addition, the embodiment of the present invention adopts a histogram to analyze the grayscale changes in the image, defines the abscissa of the first valley of the histogram as the first grayscale value, and defines the ratio of the maximum grayscale value (grayscale value is 255) to the first grayscale value as the optimal acquisition group number for the exposure time of the first exposure time. The first exposure time is used to project the optimal number of Fourier sinusoidal fringe patterns. At this time, the exposure time of each group of Fourier sinusoidal fringe patterns is short. This short exposure time is defined as the second exposure time of the camera. The second exposure time is used to collect a group of Fourier sinusoidal fringe patterns, which can balance the exposure of the image details of the bright and dark parts at the same time and improve the image acquisition efficiency. The reconstructed light transmission coefficient is obtained for each pixel of the camera, and the light originally mixed from different positions of the light source can be decomposed, which provides the premise and basis for three-dimensional reconstruction under global illumination interference. The search area of ​​the direct illumination point is constrained to a short line, which avoids the fuzzy points in the dual-chip positioning and speeds up the search speed.

[0092] Figure 5 A schematic diagram of a reflective object measuring device provided by an embodiment of the present invention, referring to Figure 5 The device includes: an image projection and acquisition module 510, a second exposure time acquisition module 520, a receiving range determination module 530, a reconstructed light transfer coefficient acquisition module 540, a direct illumination point acquisition module 550 and a reflective object reconstruction module 560.

[0093] In the embodiment of the present invention, the image projection and acquisition module 510 is used to control the projector to sequentially project a group of Fourier sinusoidal fringe patterns with an exposure time of the first exposure time onto the surface of the reflective object, and at the same time control the camera to sequentially acquire a group of first deformed fringe patterns formed on the surface of the reflective object; wherein a group of Fourier sinusoidal fringe patterns includes four Fourier sinusoidal fringe patterns, and the fringe orders of the four Fourier sinusoidal fringe patterns are all the same, and the initial phases are all different; the Fourier sinusoidal fringe patterns include Fourier sinusoidal horizontal fringe patterns and Fourier sinusoidal vertical fringe patterns. The second exposure time acquisition module 520 is used to obtain the second exposure time of the camera according to the group of first deformed fringe patterns acquired by the camera; wherein the second exposure time is less than the first exposure time. The image projection and acquisition module 510 is also used to control the projector to sequentially project five groups of Fourier sinusoidal horizontal fringe patterns and five groups of Fourier sinusoidal vertical fringe patterns, each group of which has an exposure time of the second exposure time, onto the surface of the reflective object, and at the same time control the camera to sequentially acquire five groups of second deformed fringe patterns and five groups of third deformed fringe patterns formed on the surface of the reflective object. The receiving range determination module 530 is used to determine the receiving range of each pixel of the camera to the pixel of the projector according to a set of second deformed fringe patterns and a set of third deformed fringe patterns collected by the camera and the Fourier slice theorem. The reconstructed light transfer coefficient acquisition module 540 is used to obtain the reconstructed light transfer coefficient using the single pixel imaging technology for the second deformed fringe pattern and the third deformed fringe pattern. The direct illumination point acquisition module 550 is used to determine the direct illumination points of the pixels of the projector one by one according to the reconstructed light transfer coefficient obtained by the reconstructed light transfer coefficient acquisition module and the depth constraint positioning method. The reflective object reconstruction module 560 is used to collect all the direct illumination points obtained by the direct illumination point acquisition module to complete the reconstruction of the reflective object image.

[0094] The reflective object measuring device provided in the embodiment of the present invention can execute the reflective object measuring method provided in any embodiment of the present invention, and has functional modules and beneficial effects corresponding to the execution method. For contents not described in detail in the embodiment of the present invention, reference can be made to the reflective object measuring device provided in the above embodiment.

[0095] Figure 6 A schematic diagram of a reflective object measuring device provided by an embodiment of the present invention, referring to Figure 6 The embodiment of the present invention further provides a reflective object measuring device, including a projector 61, a camera 62 and a processing device 60. The projector 61 and the camera 62 are both connected to the processing device 60. Figure 6 The processing device 60 includes a memory 602, a processor 601, and a computer program stored in the memory 602 and executable on the processor. When the processor 601 executes the program, the method in the above embodiment is implemented. Figure 6 A block diagram of an exemplary processing device suitable for use in implementing embodiments of the present invention is shown. Figure 6 The processing device 60 shown is only an example and should not limit the functionality and scope of use of the embodiments of the present invention. Figure 6 As shown, the processing device 60 is in the form of a general computing device. The components of the processing device 60 may include but are not limited to: one or more processors 601, a system memory 602, and a bus 603 connecting different system components (including the system memory 602 and the processor 601).

[0096] Bus 603 represents one or more of several types of bus structures, including a memory bus or memory controller, a peripheral bus, an accelerated graphics port, a processor or a local bus using any of a variety of bus structures. For example, these architectures include but are not limited to Industry Standard Architecture (ISA) bus, Micro Channel Architecture (MAC) bus, Enhanced ISA bus, Video Electronics Standards Association (VESA) local bus and Peripheral Component Interconnect (PCI) bus.

[0097] The processing device 60 typically includes a variety of computer system readable media. These media can be any available media that can be accessed by the processing device 60, including volatile and non-volatile media, removable and non-removable media.

[0098] System memory 602 may include computer system readable media in the form of volatile memory, such as random access memory (RAM) 604 and / or cache memory 605. Processing device 60 may further include other removable / non-removable, volatile / non-volatile computer system storage media. By way of example only, storage system 606 may be used to read and write non-removable, non-volatile magnetic media ( Figure 6 not shown, usually called a "hard drive"). Although Figure 6 Not shown in the figure, a disk drive for reading and writing to a removable non-volatile disk (e.g., a "floppy disk"), and an optical disk drive for reading and writing to a removable non-volatile optical disk (e.g., a CD-ROM, a DVD-ROM, or other optical media) may be provided. In these cases, each drive may be connected to the bus 603 via one or more data medium interfaces. The system memory 602 may include at least one program product having a set (e.g., at least one) of program modules that are configured to perform the functions of the embodiments of the present invention.

[0099] A program / utility 608 having a set (at least one) of program modules 607 may be stored, for example, in system memory 602, such program modules 607 including, but not limited to, an operating system, one or more application programs, other program modules, and program data, each of which or some combination may include an implementation of a network environment. Program modules 607 generally perform the functions and / or methods of the embodiments described herein.

[0100] The processing device 60 may also communicate with one or more external devices 609 (e.g., a keyboard, a pointing device, a display 610, etc.), one or more devices that enable a user to interact with the device, and / or any device that enables the processing device 60 to communicate with one or more other computing devices (e.g., a network card, a modem, etc.). Such communication may be performed through an input / output (I / O) interface 611. Furthermore, the processing device 60 may also communicate with one or more networks (e.g., a local area network (LAN), a wide area network (WAN), and / or a public network, such as the Internet) through a network adapter 612. Figure 6 As shown, the network adapter 612 communicates with other modules of the processing device 60 via the bus 603. It should be understood that, although not shown in the figure, other hardware and / or software modules can be used in conjunction with the processing device 60, including but not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data backup storage systems.

[0101] The processor 601 executes various functional applications and data processing by running programs stored in the system memory 602 .

[0102] An embodiment of the present invention further provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the method described in the above embodiment can be implemented.

[0103] The computer storage medium of the embodiment of the present invention can adopt any combination of one or more computer-readable media. The computer-readable medium can be a computer-readable signal medium or a computer-readable storage medium. The computer-readable storage medium can be, for example, but not limited to: an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device or device, or any combination of the above. More specific examples (non-exhaustive list) of computer-readable storage media include: an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. In this document, a computer-readable storage medium can be any tangible medium containing or storing a program, which can be used by an instruction execution system, device or device or used in combination with it.

[0104] Computer-readable signal media may include data signals propagated in baseband or as part of a carrier wave, which carry computer-readable program code. Such propagated data signals may take a variety of forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. Computer-readable signal media may also be any computer-readable medium other than a computer-readable storage medium, which may send, propagate, or transmit a program for use by or in conjunction with an instruction execution system, apparatus, or device.

[0105] The program code embodied on the computer readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.

[0106] Computer program code for performing the operations of the present invention may be written in one or more programming languages ​​or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, C++, and conventional procedural programming languages ​​such as "C" or similar programming languages. The program code may be executed entirely on the user's computer, partially on the user's computer, as a separate software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0107] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, combinations and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A method for measuring a reflective object, characterized in that: The method is implemented by using a measuring device for reflective objects, wherein the measuring device for reflective objects comprises: a projector and a camera; The method for measuring the reflective object comprises: Control the projector to sequentially project a group of Fourier sinusoidal fringe patterns with an exposure time of a first exposure time onto the surface of the reflective object, and control the camera to sequentially collect a group of first deformed fringe patterns formed on the surface of the reflective object; wherein a group of the Fourier sinusoidal fringe patterns includes four Fourier sinusoidal fringe patterns, the fringe orders of the four Fourier sinusoidal fringe patterns are all the same, and the initial phases are all different; the Fourier sinusoidal fringe patterns include Fourier sinusoidal horizontal fringe patterns and Fourier sinusoidal vertical fringe patterns; Obtaining a second exposure time of the camera according to a set of the first deformed fringe patterns collected by the camera; wherein the second exposure time is less than the first exposure time; Control the projector to sequentially project five groups of the Fourier sinusoidal horizontal fringe patterns and five groups of the Fourier sinusoidal vertical fringe patterns, each group having an exposure time of the second exposure time, onto the surface of the reflective object, and control the camera to sequentially collect five groups of the second deformed fringe patterns and five groups of the third deformed fringe patterns formed on the surface of the reflective object; Determine a receiving range of each pixel of the camera for a pixel of the projector according to a set of the second deformed fringe patterns and a set of the third deformed fringe patterns collected by the camera and the Fourier slice theorem; Obtaining a reconstructed light transfer coefficient using a single pixel imaging technique on the second deformed fringe pattern and the third deformed fringe pattern; Determine the direct illumination points of the pixels of the projector one by one according to the reconstructed light transfer coefficient and the depth-constrained positioning method; All the direct illumination points are collected to complete the reconstruction of the reflective object image.

2. The method for measuring a reflective object according to claim 1, characterized in that: The Fourier sinusoidal horizontal fringe pattern and the Fourier sinusoidal vertical fringe pattern satisfy: Among them, P φ is the Fourier sinusoidal horizontal fringe pattern or the Fourier sinusoidal vertical fringe pattern, (u′, v′) is the pixel of the projector, (k, l) is the spatial frequency of the camera, (M, N) is the resolution of the camera, φ is the initial phase of the Fourier sinusoidal horizontal fringe pattern or the Fourier sinusoidal vertical fringe pattern, and the value of φ includes 0, π / 2, π and 3π / 2; a is the average intensity of the Fourier sinusoidal horizontal fringe pattern or the Fourier sinusoidal vertical fringe pattern, and b is the contrast of the Fourier sinusoidal horizontal fringe pattern or the Fourier sinusoidal vertical fringe pattern; The fringe orders of the five groups of Fourier sinusoidal horizontal fringe images are 8, 16, 24, 32, and 40 respectively; the initial phases of the four Fourier sinusoidal horizontal fringe images in each group are 0, π / 2, π, and 3π / 2 respectively; The fringe orders of the five groups of the Fourier sinusoidal vertical fringe images are 8, 16, 24, 32, and 40 respectively; the initial phases of the four Fourier sinusoidal vertical fringe images in each group are 0, π / 2, π, and 3π / 2 respectively.

3. The method for measuring a reflective object according to claim 1, characterized in that: The obtaining the second exposure time of the camera according to a set of the first deformed fringe patterns collected by the camera comprises: Superimposing the grayscale values ​​of a set of the first deformed fringe images collected by the camera pixel by pixel and dividing the result by 4 to obtain the number of pixels for each grayscale value; Gather the number of pixels for each gray value into a histogram; defining the abscissa of a first valley of the histogram as a first grayscale value; Obtaining the optimal number of acquisition groups according to the maximum grayscale value and the first grayscale value; The second exposure time of the camera is obtained according to the first exposure time and the optimal number of acquisition groups.

4. The method for measuring a reflective object according to claim 1, characterized in that: Determining the receiving range of each pixel of the camera to the pixel of the projector according to a set of the second deformed fringe patterns and a set of the third deformed fringe patterns collected by the camera and the Fourier slice theorem includes: Calculating according to the Fourier slice theorem based on a group of the second deformed fringe patterns and a group of the third deformed fringe patterns collected by the camera to obtain a first Fourier coefficient of a first projection function of the second deformed fringe pattern and a second Fourier coefficient of a second projection function of the third deformed fringe pattern; Performing one-dimensional discrete Fourier transform on the first Fourier coefficient and the second Fourier coefficient to obtain the first projection function and the second projection function; It is determined that an area in which the values ​​of the first projection function and the second projection function both exceed a preset noise threshold is a reception range of each pixel of the camera for the pixel of the projector.

5. The method for measuring a reflective object according to claim 4, characterized in that: The first Fourier coefficient The second Fourier coefficient The first projection function h x (u′;u,v)=IDFT[H x (k)]; The second projection function is h y (u′;u,v)=IDFT[H y (l)]; in, is a first response value of the camera when the Fourier sinusoidal horizontal fringe pattern is projected onto the reflective object; is the response value of the camera when the Fourier sinusoidal vertical fringe pattern is projected onto the reflective object, φ is the initial phase of the Fourier sinusoidal horizontal fringe pattern or the Fourier sinusoidal vertical fringe pattern, and the values ​​of φ include 0, π / 2, π and 3π / 2; IDFT[·] represents one-dimensional discrete Fourier transform.

6. The method for measuring a reflective object according to claim 1, characterized in that: The step of obtaining the reconstructed light transfer coefficient by using the single pixel imaging technology on the second deformed fringe pattern and the third deformed fringe pattern comprises: Obtain third Fourier coefficients of third projection functions of the second deformed fringe patterns and the third deformed fringe patterns by calculating according to the Fourier slice theorem based on a group of the second deformed fringe patterns and a group of the third deformed fringe patterns collected by the camera; The reconstructed light transmission coefficient is obtained according to the discrete Fourier inverse transform principle.

7. The method for measuring a reflective object according to claim 1, characterized in that: The step of determining the direct illumination points of the pixels of the projector one by one according to the reconstructed light transfer coefficient and the depth-constrained positioning method comprises: Determine absolute phase using Gray coding and phase shift methods; Determine the length-limiting polar line according to the absolute phase; The direct illumination point of the pixel of the projector is determined according to the length limiting epipolar line.

8. A measuring device for reflective objects, characterized in that: include: An image projection and acquisition module, used to control the projector to sequentially project a group of Fourier sinusoidal fringe patterns with an exposure time of a first exposure time onto the surface of the reflective object, and simultaneously control the camera to sequentially acquire a group of first deformed fringe patterns formed on the surface of the reflective object; wherein a group of the Fourier sinusoidal fringe patterns includes four Fourier sinusoidal fringe patterns, the fringe orders of the four Fourier sinusoidal fringe patterns are all the same, and the initial phases are all different; the Fourier sinusoidal fringe patterns include Fourier sinusoidal horizontal fringe patterns and Fourier sinusoidal vertical fringe patterns; A second exposure time acquisition module, used to obtain a second exposure time of the camera according to a set of the first deformed fringe patterns collected by the camera; wherein the second exposure time is less than the first exposure time; The image projection and acquisition module is further used to control the projector to sequentially project five groups of the Fourier sinusoidal horizontal fringe patterns and five groups of the Fourier sinusoidal vertical fringe patterns, each group of which has an exposure time of the second exposure time, onto the surface of the reflective object, and simultaneously control the camera to sequentially acquire five groups of the second deformed fringe patterns and five groups of the third deformed fringe patterns formed on the surface of the reflective object; a receiving range determining module, configured to determine a receiving range of each pixel of the camera to a pixel of the projector according to a set of the second deformed fringe patterns and a set of the third deformed fringe patterns collected by the camera and the Fourier slice theorem; a reconstructed light transfer coefficient acquisition module, configured to obtain a reconstructed light transfer coefficient by using a single pixel imaging technique on the second deformed fringe pattern and the third deformed fringe pattern; A direct illumination point acquisition module, used for determining the direct illumination points of the pixels of the projector one by one according to the reconstructed light transfer coefficient acquired by the reconstructed light transfer coefficient acquisition module and a depth constraint positioning method; The reflective object reconstruction module is used to collect all the direct illumination points acquired by the direct illumination point acquisition module to complete the reconstruction of the reflective object image.

9. A measuring device for reflective objects, characterized in that: The reflective object measuring device comprises: a projector, a camera, at least one processor; and a memory in communication connection with the at least one processor; The memory stores a computer program executable by the at least one processor, and the computer program is executed by the at least one processor so that the at least one processor can execute the method for measuring a reflective object according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a processor to implement the method for measuring a reflective object according to any one of claims 1 to 7 when executed.

Images