A dual-frequency phase expansion method and measuring device for coded succession

Abstract

The application relates to the field of structured light three-dimensional measurement, and discloses a dual-frequency phase unwrapping method for encoding continuation, which cyclically projects absolute phase fringe sequence groups to an object, each absolute phase fringe sequence group comprises high-frequency three-step phase shift fringe images and first-step low-frequency phase shift fringe images and second-step low-frequency phase shift fringe images in low-frequency three-step phase shift fringe images, and absolute phase is calculated once per 1 or 2 phase shift fringe images corresponding to image signals. The total fringe number (N abs ) of the absolute phase fringe sequence group is 5, the absolute phase acquisition rate (f aacq ) is reduced from every 6 of the standard dual-frequency three-step phase shift method to an average of every 1.5, and the absolute phase acquisition rate is improved. In each fringe sequence group used for acquiring absolute phase, the high-frequency fringe group used for finally unwrapping absolute phase has a fringe number (N afspan ) of 4, and only two high-frequency phase shift fringe images are separated by one low-frequency phase shift fringe image, so that the measurement precision is maximally maintained.

Description

Technical Field

[0001] This application relates to the field of structured light three-dimensional measurement technology, and more specifically, to a dual-frequency phase unwrapping method and measuring device with coded succession. Background Technology

[0002] With the rapid development of informatization, automation, and intelligence in industrial manufacturing, the demand for applications that can quickly and accurately perceive the three-dimensional information of objects is also growing rapidly. In optical 3D measurement, phase measurement profilometry (PMP) is widely used due to its advantages of high precision, high resolution, and high-speed non-contact operation. In phase measurement profilometry, when solving for the relative phase using Fourier Transform Profilometry (FTP), only one fringe pattern is needed for each frequency, making it suitable for high-speed measurement scenarios. However, due to the spectral aliasing caused by reliance on the spatial information of the object's surface, Fourier Transform Profilometry is only suitable for profilometry of objects with smooth, continuous, and abrupt surfaces.

[0003] Phase-shift profilometry (PSP) relies solely on temporal information from a single pixel and offers high accuracy even when measuring objects with highly varied surface textures. Therefore, it is most widely used in structured light projection measurement of object contours. PSP obtains the absolute phase using a standard multi-frequency, multi-step phase-shift expansion method, and then reconstructs the object's three-dimensional coordinates using optical triangulation. The standard multi-step phase-shift method requires at least three phase-shift fringe images to calculate the relative phase in a sequence of phase-shift fringe images at each frequency, due to the presence of three unknowns: background intensity, modulation index, and the phase value to be determined. Currently, the multi-frequency three-step phase-shift method is widely used, with the dual-frequency three-step method requiring the fewest phase-shift fringe images and being the most widely adopted. However, even while maintaining measurement accuracy, the dual-frequency three-step method still requires projecting at least six phase-shift fringe images onto the object surface to obtain the absolute phase, making it less effective in high-speed, dynamic 3D measurement scenarios. Summary of the Invention

[0004] The purpose of this application is to provide a dual-frequency phase expansion method and measurement device for coded succession, which solves the technical problem of poor performance of the dual-frequency three-step phase shift method in high-speed dynamic three-dimensional measurement scenarios, and achieves the technical effect of improving the measurement effect of the dual-frequency three-step phase shift method in high-speed dynamic three-dimensional measurement scenarios by improving the dual-frequency three-step phase shift method.

[0005] This application provides a method for encoding and succession of dual-frequency phase unfolding. The method includes: cyclically projecting a sequence of absolute phase fringe images onto the object under test. Each absolute phase fringe sequence includes a first low-frequency phase shift fringe image and a second low-frequency phase shift fringe image from a high-frequency three-step phase shift fringe image and a low-frequency three-step phase shift fringe image; continuing the image signals corresponding to the last four phase shift fringe images of the previous absolute phase fringe sequence, and obtaining the image signal corresponding to a new phase shift fringe image, replacing the image signal corresponding to the first phase shift fringe image of the previous absolute phase fringe sequence, to obtain a new image signal corresponding to the absolute phase fringe sequence; or continuing the image signals corresponding to the last three phase shift fringe images of the previous absolute phase fringe sequence, and obtaining the image signals corresponding to two new phase shift fringe images, replacing the image signals corresponding to the first two phase shift fringe images of the previous absolute phase fringe sequence, to obtain a new image signal corresponding to the absolute phase fringe sequence; and performing phase calculation and unfolding based on the image signal corresponding to the new absolute phase fringe sequence to obtain the absolute phase.

[0006] In one possible implementation, an absolute phase fringe sequence is cyclically projected onto the object under test, comprising: cyclically projecting a characteristic dual-frequency phase-shift fringe sequence onto the object under test, wherein the characteristic dual-frequency phase-shift fringe sequence comprises a first low-frequency phase-shift fringe image and a second low-frequency phase-shift fringe image from four sets of high-frequency three-step phase-shift fringe images and three sets of low-frequency three-step phase-shift fringe images arranged sequentially; the first low-frequency phase-shift fringe image and the second low-frequency phase-shift fringe image from each set of low-frequency three-step phase-shift fringe images are inserted into the four sets of high-frequency three-step phase-shift fringe images every two high-frequency phase-shift fringe images, and the first low-frequency phase-shift fringe image from the first set of low-frequency three-step phase-shift fringe images is inserted between the first two high-frequency phase-shift fringe images from the first set of high-frequency three-step phase-shift fringe images.

[0007] In another possible implementation, acquiring the image signal corresponding to a new phase-shifted fringe image and replacing the image signal corresponding to the first phase-shifted fringe image of the previous absolute phase fringe sequence group includes: acquiring the image signal corresponding to a new high-frequency phase-shifted fringe image and replacing the image signal corresponding to the first high-frequency phase-shifted fringe image of the previous absolute phase fringe sequence group; acquiring the image signals corresponding to two new phase-shifted fringe images and replacing the image signals corresponding to the first two phase-shifted fringe images of the previous absolute phase fringe sequence group includes: continuing with the image signals corresponding to the last three phase-shifted fringe images of the previous absolute phase fringe sequence group, acquiring the image signals corresponding to a new low-frequency phase-shifted fringe image and a new high-frequency phase-shifted fringe image, and replacing the image signals corresponding to the first low-frequency phase-shifted fringe image and the first high-frequency phase-shifted fringe image of the previous absolute phase fringe sequence group.

[0008] In another possible implementation, the absolute phase is obtained by solving and unfolding the image signal corresponding to the new absolute phase fringe sequence group. This includes: solving for the high-frequency wrapping phase value and high-frequency background intensity value corresponding to the high-frequency three-step phase-shifted fringe image based on the image signal corresponding to the high-frequency three-step phase-shifted fringe image; using the high-frequency background intensity value as the low-frequency background intensity value of the first and second low-frequency phase-shifted fringe images in the low-frequency three-step phase-shifted fringe image; generating the image signal corresponding to the third low-frequency phase-shifted fringe image in the low-frequency three-step phase-shifted fringe image based on the low-frequency background intensity value and the image signals corresponding to the first and second low-frequency phase-shifted fringe images in the low-frequency three-step phase-shifted fringe image; obtaining the image signal corresponding to the low-frequency three-step phase-shifted fringe image; and determining the low-frequency wrapping phase value corresponding to the low-frequency three-step phase-shifted fringe image based on the image signal corresponding to the low-frequency three-step phase-shifted fringe image.

[0009] In another possible implementation, the method further includes: extending the range of the high-frequency wrapping phase value and the low-frequency wrapping phase value to [0, 2π], and performing phase expansion on the range of the high-frequency wrapping phase value and the low-frequency wrapping phase value after extension to [0, 2π] to obtain the absolute phase value.

[0010] In another possible implementation, the phases of each set of high-frequency three-step phase-shifted fringe images are 0°, 120° and 240°, respectively, and the phases of the first low-frequency phase-shifted fringe image and the second low-frequency phase-shifted fringe image of each set of low-frequency three-step phase-shifted fringe images are 0° and 120°, respectively.

[0011] In another possible implementation, the high-frequency wrapping phase value and high-frequency background intensity value corresponding to the high-frequency three-step phase-shifting fringe image are solved using the following formula, based on the image signal corresponding to the high-frequency three-step phase-shifting fringe image:

[0012]

[0013] Where x and y represent pixel coordinates. Let A(x,y) represent the grayscale values ​​of the image signal of the modulated high-frequency phase-shifted stripe image, and B1(x,y) represent the high-frequency background intensity value, and B1(x,y) represent the high-frequency modulation depth value. This indicates the high-frequency wrapping phase value.

[0014] In another possible implementation, the image signal corresponding to the third low-frequency phase-shifting fringe image in the low-frequency three-step phase-shifting fringe image is generated based on the low-frequency background intensity value and the image signals corresponding to the first and second low-frequency phase-shifting fringe images in the low-frequency three-step phase-shifting fringe image, using the following formula:

[0015]

[0016] in, This represents the grayscale value of the image signal corresponding to two low-frequency phase-shifted fringe images with different phases. B2(x,y) represents the grayscale value of the image signal corresponding to the low-frequency phase-shifted fringe image generated in step 3, and B2(x,y) represents the low-frequency modulation value. This indicates the low-frequency wrapping phase value.

[0017] In another possible implementation, the low-frequency wrapping phase value corresponding to the low-frequency three-step phase-shifted fringe image is determined based on the image signal corresponding to the low-frequency three-step phase-shifted fringe image using the following formula:

[0018]

[0019] This application also provides a measuring device employing the aforementioned encoded successive dual-frequency phase unfolding method, comprising: a projection module for cyclically projecting absolute phase fringe sequence groups onto the object under test, each absolute phase fringe sequence group comprising 5 absolute phase fringe images, the 5 absolute phase fringe images including a high-frequency three-step phase-shift fringe image and a first low-frequency phase-shift fringe image and a second low-frequency phase-shift fringe image from a low-frequency three-step phase-shift fringe image; and a signal acquisition module for continuing the image signals corresponding to the last 4 phase-shift fringe images of the previous absolute phase fringe sequence group and acquiring the image signal corresponding to a new phase-shift fringe image. The image signal corresponding to the first phase-shifted fringe image of the previous absolute phase fringe sequence group is replaced to obtain the image signal corresponding to the new absolute phase fringe sequence group; or it is used to continue the image signal corresponding to the last 3 phase-shifted fringe images of the previous absolute phase fringe sequence group, and obtain the image signal corresponding to the new 2 phase-shifted fringe images, replacing the image signal corresponding to the first 2 phase-shifted fringe images of the previous absolute phase fringe sequence group to obtain the image signal corresponding to the new absolute phase fringe sequence group; the data processing module is used to perform phase calculation and expansion to obtain the absolute phase based on the image signal corresponding to the new absolute phase fringe sequence group.

[0020] The beneficial effects of the embodiments in this application compared with the prior art are:

[0021] This application provides a method for encoding and succession of dual-frequency phase expansion, wherein when obtaining the absolute phase, the total number of fringe amplitudes (N) of the absolute phase fringe sequence group is... abs The number of frames is 5, and the absolute phase acquisition rate (f) is 5. aacq The acquisition rate of absolute phase is improved by reducing the number of frames from 6 to an average of 1.5 frames per step in the standard dual-frequency three-step phase-shifting method; in each fringe sequence group used to acquire absolute phase, the high-frequency fringe group used for final absolute phase unfolding spans the number of fringe frames (N). afspanThe measurement consists of four images, with only two high-frequency phase-shift fringe images spaced one low-frequency phase-shift fringe image between them, thus maximizing measurement accuracy. Attached Figure Description

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

[0023] Figure 1 A flowchart illustrating a dual-frequency phase expansion method for encoding succession provided in an embodiment of this application;

[0024] Figure 2 This is a schematic diagram of an absolute phase stripe sequence group provided in an embodiment of this application;

[0025] Figure 3 A schematic diagram of a high-frequency three-step phase-shifting fringe image provided in an embodiment of this application;

[0026] Figure 4 A schematic diagram of a first-step low-frequency phase-shift fringe image and a second-step low-frequency phase-shift fringe image provided for embodiments of this application;

[0027] Figure 5 A schematic diagram of an object modulated image corresponding to a high-frequency three-step phase-shifting fringe image provided in an embodiment of this application;

[0028] Figure 6 A schematic diagram of the modulated object image corresponding to the first step low-frequency phase-shift fringe image, the second step low-frequency phase-shift fringe image, and the generated third step low-frequency phase-shift fringe image provided in the embodiments of this application;

[0029] Figure 7 This application provides an embodiment of a wrap-around phase image of an object modulated image corresponding to a high-frequency three-step phase-shift fringe image and a low-frequency three-step phase-shift fringe image, respectively.

[0030] Figure 8 This application provides an embodiment of the final unfolded absolute phase map corresponding to a high-frequency three-step phase-shifting fringe image and a low-frequency three-step phase-shifting fringe image. Detailed Implementation

[0031] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0032] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0033] As used in this application specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if detected [the described condition or event]" may be interpreted, depending on the context, as meaning "once determined," "in response to determination," "once detected [the described condition or event]," or "in response to detection [the described condition or event]."

[0034] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0035] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0036] When measuring the contour of an object, the dual-frequency three-step phase-shifting method requires at least six phase-shifting fringe images to be projected onto the object surface to obtain the absolute phase while maintaining measurement accuracy. This makes the dual-frequency three-step phase-shifting method perform poorly in high-speed dynamic 3D measurement scenarios.

[0037] Based on the above reasons, this application provides a dual-frequency phase unwrapping method with coded succession. This method includes: cyclically projecting an absolute phase fringe sequence group onto the object under test. Each absolute phase fringe sequence group includes a first low-frequency phase shift fringe image and a second low-frequency phase shift fringe image from a high-frequency three-step phase shift fringe image and a low-frequency three-step phase shift fringe image; continuing the image signals corresponding to the last four phase shift fringe images of the previous absolute phase fringe sequence group, and obtaining the image signal corresponding to a new one phase shift fringe image, replacing the image signal corresponding to the first one phase shift fringe image of the previous absolute phase fringe sequence group, to obtain the image signal corresponding to a new absolute phase fringe sequence group; or continuing the image signals corresponding to the last three phase shift fringe images of the previous absolute phase fringe sequence group, and obtaining the image signals corresponding to two new phase shift fringe images, replacing the image signals corresponding to the first two phase shift fringe images of the previous absolute phase fringe sequence group, to obtain the image signal corresponding to a new absolute phase fringe sequence group; and performing phase calculation and unwrapping based on the image signal corresponding to the new absolute phase fringe sequence group to obtain the absolute phase. The dual-frequency phase expansion method for encoding succession in the embodiments of this application, the total number of fringe amplitudes (N) of the absolute phase fringe sequence group. abs The number of frames is 5, and the absolute phase acquisition rate (f) is 5. aacq The acquisition rate of absolute phase is improved by reducing the number of frames from 6 to an average of 1.5 frames per step in the standard dual-frequency three-step phase-shifting method; in each fringe sequence group used to acquire absolute phase, the high-frequency fringe group used for final absolute phase unfolding spans the number of fringe frames (N). afspan The measurement consists of four images, with only two high-frequency phase-shift fringe images spaced one low-frequency phase-shift fringe image between them, thus maximizing measurement accuracy.

[0038] In some scenarios, the dual-frequency phase expansion method with coded succession according to the embodiments of this application can be applied to the surface contour measurement of objects, which greatly improves the absolute phase acquisition rate and enables fast and high-precision measurement of object contours during high-speed movement. It has a better performance in high-speed dynamic three-dimensional measurement scenarios.

[0039] The following describes in detail, with specific examples, a dual-frequency phase expansion method for encoding succession provided in the embodiments of this application.

[0040] Figure 1 A flowchart illustrating a dual-frequency phase expansion method for encoding succession provided in this application embodiment is shown below. Figure 1 As shown, the dual-frequency phase expansion method for this encoding succession includes S110 to S130, and S110 to S130 will be explained in detail below.

[0041] S110. Project an absolute phase fringe sequence group onto the object under test in a cyclic manner. Each absolute phase fringe sequence group includes a high-frequency three-step phase-shift fringe image and a low-frequency three-step phase-shift fringe image, specifically the first low-frequency phase-shift fringe image and the second low-frequency phase-shift fringe image.

[0042] When acquiring the absolute phase, an absolute phase fringe sequence group can be cyclically projected onto the object under test. The absolute phase fringe sequence group is a set of phase fringe images used to acquire the absolute phase. Each absolute phase fringe sequence group includes a high-frequency three-step phase-shift fringe image and two low-frequency three-step phase-shift fringe images, such that the total number of fringe amplitudes (N) in the absolute phase fringe sequence group is [missing information]. abs There are 5 images.

[0043] When obtaining the absolute phase, a new absolute phase fringe sequence can be obtained through the cyclic projection of the absolute phase fringe sequence group. The absolute phase can be solved and calculated based on the first and second low-frequency phase shift fringe images in the high-frequency three-step phase shift fringe images and the low-frequency three-step phase shift fringe images in the new absolute phase fringe sequence group.

[0044] S120. Continue the image signals corresponding to the last 4 phase-shifted fringe images of the previous absolute phase fringe sequence group, and obtain the image signal corresponding to the new 1 phase-shifted fringe image. Replace the image signal corresponding to the first 1 phase-shifted fringe image of the previous absolute phase fringe sequence group to obtain the image signal corresponding to the new absolute phase fringe sequence group; or continue the image signals corresponding to the last 3 phase-shifted fringe images of the previous absolute phase fringe sequence group, and obtain the image signals corresponding to the new 2 phase-shifted fringe images. Replace the image signals corresponding to the first 2 phase-shifted fringe images of the previous absolute phase fringe sequence group to obtain the image signal corresponding to the new absolute phase fringe sequence group.

[0045] In high-speed 3D measurement scenarios, the standard dual-frequency three-step phase-shifting method requires obtaining the absolute phase once every 6 dual-frequency three-step phase-shifting images, resulting in poor performance of the standard dual-frequency three-step phase-shifting method in high-speed 3D measurement scenarios.

[0046] In this embodiment, the image signal corresponding to the last four phase-shifted fringe images of the previous absolute phase fringe sequence group can be continued, and the image signal corresponding to the new phase-shifted fringe image can be obtained. This new image signal is then used to replace the image signal corresponding to the first phase-shifted fringe image of the previous absolute phase fringe sequence group. In other words, the image signal corresponding to the last four phase-shifted fringe images of the previous absolute phase fringe sequence group is reused, and the image signal corresponding to the first phase-shifted fringe image of the previous absolute phase fringe sequence group is replaced with the new image signal to obtain the new image signal corresponding to the absolute phase fringe sequence group.

[0047] In this embodiment, the image signals corresponding to the last three phase-shifted fringe images of the previous absolute phase fringe sequence group can be continued, and the image signals corresponding to the new two phase-shifted fringe images can be obtained to replace the image signals corresponding to the first two phase-shifted fringe images of the previous absolute phase fringe sequence group. That is, the image signals corresponding to the last three phase-shifted fringe images of the previous absolute phase fringe sequence group are reused, and the image signals corresponding to the first two phase-shifted fringe images of the previous absolute phase fringe sequence group are replaced with the new two phase-shifted fringe images to obtain the image signals corresponding to the new absolute phase fringe sequence group.

[0048] By using the above-mentioned encoding and replacement method to obtain the image signal corresponding to the absolute phase stripe sequence group, the absolute phase can be obtained once every 1.5 dual-frequency three-step phase-shifting images on average, which greatly improves the absolute phase acquisition rate.

[0049] S130. Perform phase calculation and expansion to obtain the absolute phase based on the image signal corresponding to the new absolute phase stripe sequence group.

[0050] After obtaining the image signal corresponding to the new absolute phase stripe sequence group, phase calculation and unfolding can be performed to obtain the absolute phase.

[0051] The beneficial effect of the above implementation method is that, in absolute phase acquisition, the total number of fringe amplitudes (N) of the absolute phase fringe sequence group is reduced. abs The number of frames is 5, and the absolute phase acquisition rate (f) is 5. aacq The absolute phase acquisition rate is greatly improved by reducing the number of frames from 6 to an average of 1.5 in the standard dual-frequency three-step phase shift method.

[0052] The beneficial effect of the above implementation method is that, in each fringe sequence group used to obtain the absolute phase, the high-frequency fringe group used to finally unfold the absolute phase spans the number of fringe amplitudes (N). afspan The measurement consists of four images, with only two high-frequency phase-shift fringe images spaced one low-frequency phase-shift fringe image between them, thus maximizing measurement accuracy.

[0053] In some implementations, the absolute phase fringe sequence is cyclically projected onto the object under test, including: cyclically projecting a characteristic dual-frequency phase-shift fringe sequence onto the object under test. The characteristic dual-frequency phase-shift fringe sequence includes four sets of high-frequency three-step phase-shift fringe images and three sets of low-frequency three-step phase-shift fringe images, with the first low-frequency phase-shift fringe image and the second low-frequency phase-shift fringe image from each set of low-frequency three-step phase-shift fringe images inserted into the four sets of high-frequency three-step phase-shift fringe images every two high-frequency phase-shift fringe images. Furthermore, the first low-frequency phase-shift fringe image from the first set of low-frequency three-step phase-shift fringe images is inserted between the first two high-frequency phase-shift fringe images from the first set of high-frequency three-step phase-shift fringe images.

[0054] When cyclically projecting an absolute phase fringe sequence onto the object under test, a characteristic dual-frequency phase-shift fringe sequence can be cyclically projected onto the object under test. The characteristic dual-frequency phase-shift fringe sequence includes four sets of high-frequency three-step phase-shift fringe images arranged in sequence and the first and second low-frequency phase-shift fringe images from three sets of low-frequency three-step phase-shift fringe images. Each set of high-frequency three-step phase-shift fringe images includes three high-frequency phase-shift fringe images projected in sequence. The four sets of high-frequency three-step phase-shift fringe images contain a total of 12 high-frequency phase-shift fringe images. At the same time, the first and second low-frequency phase-shift fringe images from the three sets of low-frequency three-step phase-shift fringe images contain a total of 6 low-frequency phase-shift fringe images.

[0055] In the characteristic dual-frequency phase-shift fringe sequence, the first and second low-frequency phase-shift fringe images in each group of low-frequency three-step phase-shift fringe images are inserted into four groups of high-frequency three-step phase-shift fringe images every two high-frequency phase-shift fringe images. Furthermore, the first low-frequency phase-shift fringe image in the first group of low-frequency three-step phase-shift fringe images is inserted between the first two high-frequency phase-shift fringe images in the first group of high-frequency three-step phase-shift fringe images. This arrangement of the characteristic dual-frequency phase-shift fringe sequence facilitates the acquisition of new absolute phase fringe sequence groups, and the absolute phase acquisition rate (f...) aacq The number of frames required for the standard dual-frequency three-step phase-shifting method has been reduced from 6 frames to an average of 1.5 frames. On average, an absolute phase can be acquired once every 1.5 phase-shifted fringe images, which greatly improves the absolute phase acquisition rate.

[0056] Figure 2 This is a schematic diagram of an absolute phase stripe sequence group provided in an embodiment of this application, as shown below. Figure 2 As shown, in the absolute phase fringe sequence group, three high-frequency three-step phase-shifted fringe images can be obtained through I... H1 I H2 I H3 This indicates that the first and second low-frequency phase-shifting fringe images in the three low-frequency three-step phase-shifting fringe images can be obtained through I... L1 IL2 express.

[0057] Figure 3 A schematic diagram of a high-frequency three-step phase-shifting fringe image provided in an embodiment of this application is shown below. Figure 3 As shown, the spacing between the individual grating fringes in the high-frequency three-step phase-shifting fringe image is relatively small; Figure 4 A schematic diagram of a first-step low-frequency phase-shift fringe image and a second-step low-frequency phase-shift fringe image provided for embodiments of this application, as shown below. Figure 4 As shown, in the first and second low-frequency phase-shifting fringe images of the three low-frequency three-step phase-shifting fringe images, the spacing between the grating fringes in the low-frequency phase-shifting fringe images is relatively large.

[0058] Figure 5 This is a schematic diagram of a modulated image of an object corresponding to a high-frequency three-step phase-shift fringe image provided in an embodiment of this application. Figure 6 A schematic diagram of the modulated object image corresponding to the first step low-frequency phase-shift fringe image, the second step low-frequency phase-shift fringe image, and the generated third step low-frequency phase-shift fringe image provided in this application embodiment is shown below. Figure 5 and Figure 6 As shown, the image signal is obtained after the object modulates the phase-shifting fringe image. The spacing between the grating stripes in the modulated image of the object corresponding to the high-frequency three-step phase-shifting fringe image is smaller, while the spacing between the grating stripes in the modulated image of the object corresponding to the low-frequency phase-shifting fringe image is larger.

[0059] like Figure 2 As shown, the characteristic dual-frequency phase-shift fringe sequence includes 18 phase-shift fringe images, and the characteristic dual-frequency phase-shift fringe sequence S can be represented in the following form:

[0060] S = I H1 I L1 ;I H2 ;I H3 I L2 ;I H1 ;I H2 I L1 ;I H3 ;I H1 I L2 ;I H2 ;I G3 I L1 ;I H1 ;I H2 I L2 ;I G3

[0061] The beneficial effect of the above implementation method is that, through the arrangement of the above-mentioned characteristic dual-frequency phase-shifting stripe sequence, it is convenient to obtain a new absolute phase stripe sequence group, which can be reduced to an average of one absolute phase stripe sequence group every 1.5 dual-frequency three-step phase-shifting images, that is, an absolute phase can be obtained once every 1.5 dual-frequency three-step phase-shifting images, which greatly improves the absolute phase acquisition rate.

[0062] In some implementations, obtaining the image signal corresponding to a new phase-shifted fringe image and replacing the image signal corresponding to the first phase-shifted fringe image of the previous absolute phase fringe sequence group includes: obtaining the image signal corresponding to a new high-frequency phase-shifted fringe image and replacing the image signal corresponding to the first high-frequency phase-shifted fringe image of the previous absolute phase fringe sequence group.

[0063] like Figure 2 As shown, when acquiring the image signal corresponding to a new high-frequency phase-shift fringe image and replacing the image signal corresponding to the first high-frequency phase-shift fringe image of the previous absolute phase fringe sequence group, for images including high-frequency phase-shift fringe image I... H1 Low-frequency phase-shifting fringe image I L1 High-frequency phase-shifting fringe image I H2 High-frequency phase-shifting fringe image I H3 and low-frequency phase-shifted fringe image I L2 From the previous absolute phase fringe sequence group, a new high-frequency phase-shifted fringe image I can be obtained. H1 The corresponding image signal replaces the first high-frequency phase-shifted fringe image I of the previous absolute phase fringe sequence group. H1 The corresponding image signal, for the previous absolute phase fringe sequence group of low-frequency phase-shifted fringe image I L1 High-frequency phase-shifting fringe image I H2 High-frequency phase-shifting fringe image I H3 and low-frequency phase-shifted fringe image I L2 Multiplexing yields an image I including low-frequency phase-shifted fringes. L1 High-frequency phase-shifting fringe image I H2 High-frequency phase-shifting fringe image I H3 Low-frequency phase-shifting fringe image I L2 and high-frequency phase-shifted fringe image I H1 The image signal corresponding to the absolute phase stripe sequence group.

[0064] In some implementations, the image signals corresponding to the two new phase-shifted fringe images are obtained and replaced with the image signals corresponding to the first two phase-shifted fringe images of the previous absolute phase fringe sequence group. This includes: continuing with the image signals corresponding to the last three phase-shifted fringe images of the previous absolute phase fringe sequence group, obtaining the image signals corresponding to a new low-frequency phase-shifted fringe image and a new high-frequency phase-shifted fringe image, and replacing the image signals corresponding to the first low-frequency phase-shifted fringe image and the first high-frequency phase-shifted fringe image of the previous absolute phase fringe sequence group.

[0065] like Figure 2 As shown, when acquiring the image signals corresponding to a new high-frequency phase-shift fringe image and a new low-frequency phase-shift fringe image, and replacing the image signals corresponding to the first low-frequency phase-shift fringe image and the first high-frequency phase-shift fringe image of the previous absolute phase fringe sequence group, for the low-frequency phase-shift fringe image I... L1 High-frequency phase-shifting fringe image I H2 High-frequency phase-shifting fringe image I H3 Low-frequency phase-shifting fringe image I L2 and high-frequency phase-shifted fringe image I H1 From the previous absolute phase fringe sequence group, a new low-frequency phase-shifted fringe image I can be obtained. L1 And a new high-frequency phase-shifted fringe image I H2 The corresponding image signal replaces the first high-frequency phase-shifted fringe image I of the previous absolute phase fringe sequence group. H2 And the first low-frequency phase-shifted fringe image I L1 The corresponding image signal is the high-frequency phase-shifted fringe image I of the previous absolute phase fringe sequence group. H3 Low-frequency phase-shifting fringe image I L2 and high-frequency phase-shifted fringe image I H1 Multiplexing yields an image I including a high-frequency phase-shifted fringe. H3 Low-frequency phase-shifting fringe image I L2 High-frequency phase-shifting fringe image I H1 High-frequency phase-shifting fringe image I H2 and low-frequency phase-shifted fringe image I L1 The image signal corresponding to the next absolute phase stripe sequence group.

[0066] like Figure 2 The high-frequency phase-shifted fringe image I shown is... H1 Low-frequency phase-shifting fringe image I L1 High-frequency phase-shifting fringe image I H2 High-frequency phase-shifting fringe image I H3 and low-frequency phase-shifted fringe image I L2 The corresponding absolute phase fringe sequence group is displayed enclosed in solid square brackets, high-frequency phase-shift fringe image IH1 Low-frequency phase-shifting fringe image I L1 High-frequency phase-shifting fringe image I H2 High-frequency phase-shifting fringe image I H3 and low-frequency phase-shifted fringe image I L2 The absolute phase value of the corresponding absolute phase stripe sequence group is φ n .

[0067] like Figure 2 The low-frequency phase-shifted fringe image I shown is... L1 High-frequency phase-shifting fringe image I H2 High-frequency phase-shifting fringe image I H3 Low-frequency phase-shifting fringe image I L2 and high-frequency phase-shifted fringe image I H1 The corresponding absolute phase fringe sequence group is represented by dashed square brackets, and the low-frequency phase-shift fringe image I L1 High-frequency phase-shifting fringe image I H2 High-frequency phase-shifting fringe image I H3 Low-frequency phase-shifting fringe image I L2 and high-frequency phase-shifted fringe image I H1 The absolute phase value of the corresponding absolute phase fringe sequence group is φ n+1 .

[0068] like Figure 2 The high-frequency phase-shifted fringe image I shown is... H3 Low-frequency phase-shifting fringe image I L2 High-frequency phase-shifting fringe image I H1 High-frequency phase-shifting fringe image I H2 and low-frequency phase-shifted fringe image I L1 The corresponding absolute phase fringe sequence group is represented by a dotted, dashed, square bracket. High-frequency phase-shifting fringe image I H3 Low-frequency phase-shifting fringe image I L2 High-frequency phase-shifting fringe image I H1 High-frequency phase-shifting fringe image I H2 and low-frequency phase-shifted fringe image I L1 The absolute phase value of the corresponding absolute phase fringe sequence group is φ n+2 .

[0069] The beneficial effect of the above implementation method is that the absolute phase fringe sequence group can be easily obtained through two methods, which makes it easier to obtain a new absolute phase fringe sequence group. The absolute phase fringe sequence group can be obtained once every 1.5 dual-frequency three-step phase-shifting images on average, that is, the absolute phase can be obtained once every 1.5 dual-frequency three-step phase-shifting images on average, which greatly improves the absolute phase acquisition rate.

[0070] In some implementations, in S130 above, phase calculation and expansion are performed on the image signal corresponding to the new absolute phase stripe sequence group to obtain the absolute phase, including S131 to S132. S131 to S132 will be explained in detail below.

[0071] S131. Based on the image signal corresponding to the high-frequency three-step phase-shifting fringe image, solve for the high-frequency wrapping phase value and high-frequency background intensity value corresponding to the high-frequency three-step phase-shifting fringe image.

[0072] like Figure 5 As shown, Figure 5 Figures (a), (b), and (c) in the figure represent the image signals corresponding to high-frequency phase-shifted fringe images with different phases. After obtaining the image signals corresponding to the three high-frequency phase-shifted fringe images with different phases arranged in sequence, the high-frequency wrapping phase value and the high-frequency background intensity value can be determined.

[0073] Figure 7 This application provides an embodiment of a wrap-around phase image of an object modulated image corresponding to a high-frequency phase-shifting fringe image and a low-frequency phase-shifting fringe image, as shown in the example. Figure 7 As shown in Figure (a), the wrapped phase image of the object modulated image corresponding to the high-frequency three-step phase-shifting fringe image can be obtained (a).

[0074] S132. The high-frequency background intensity value is used as the low-frequency background intensity value of the first and second low-frequency phase-shifting fringe images in the low-frequency three-step phase-shifting fringe image. Based on the low-frequency background intensity value and the image signals corresponding to the first and second low-frequency phase-shifting fringe images in the low-frequency three-step phase-shifting fringe image, the image signal corresponding to the third low-frequency phase-shifting fringe image in the low-frequency three-step phase-shifting fringe image is generated. The image signal corresponding to the low-frequency three-step phase-shifting fringe image is obtained. Based on the image signal corresponding to the low-frequency three-step phase-shifting fringe image, the low-frequency wrapping phase value corresponding to the low-frequency three-step phase-shifting fringe image is determined.

[0075] When calculating the image signal of the low-frequency group, the high-frequency background intensity value can be used as the low-frequency background intensity value. Then, the image signal corresponding to the third low-frequency phase-shifting fringe image in the low-frequency three-step phase-shifting fringe image can be generated based on the image signals corresponding to the first low-frequency phase-shifting fringe image and the second low-frequency phase-shifting fringe image in the low-frequency three-step phase-shifting fringe image.

[0076] like Figure 6 As shown, the first step low-frequency phase-shift fringe image and the second step low-frequency phase-shift fringe image are respectively Figure 7 As shown in Figures (a) and (b), the image signal corresponding to the third low-frequency phase-shifting fringe image in the generated low-frequency three-step phase-shifting fringe image is: Figure 7 As shown in Figure (c).

[0077] After obtaining the image signals corresponding to the three low-frequency three-step phase-shift fringe images, the low-frequency wrapping phase value can be determined based on the low-frequency background intensity value and the image signals corresponding to the three low-frequency three-step phase-shift fringe images. For example... Figure 7 As shown in Figure (b), the wrapped phase image of the object modulated image corresponding to the low-frequency three-step phase-shifting fringe image can be obtained (b).

[0078] The beneficial effect of the above implementation method is that, since the difference between the high-frequency background intensity value and the low-frequency background intensity value can be ignored, the high-frequency background intensity value can be used as the low-frequency background intensity value, which can conveniently generate the image signal corresponding to the third low-frequency phase-shifting fringe image in the three low-frequency three-step phase-shifting fringe images.

[0079] The beneficial effect of the above implementation method is that, based on the image signals corresponding to the first and second low-frequency phase-shifting fringe images in the low-frequency three-step phase-shifting fringe image, the image signal corresponding to the third low-frequency phase-shifting fringe image in the low-frequency three-step phase-shifting fringe image can be generated quickly, thus enabling the calculation of low-frequency wrapping phase values.

[0080] In some implementations, the above method further includes: extending the value range of the high-frequency wrapped phase value and the low-frequency wrapped phase value to [0, 2π], and performing phase expansion on the value range of the high-frequency wrapped phase value and the low-frequency wrapped phase value after extension to [0, 2π] to obtain the absolute phase value.

[0081] In some implementations, the phases of each set of high-frequency three-step phase-shifted fringe images are 0°, 120° and 240°, respectively, and the phases of the first low-frequency phase-shifted fringe image and the second low-frequency phase-shifted fringe image of each set of low-frequency three-step phase-shifted fringe images are 0° and 120°, respectively.

[0082] In some implementations, the high-frequency wrapping phase value and high-frequency background intensity value corresponding to the high-frequency three-step phase-shifting fringe image can be solved using formulas (1) to (5) based on the image signal corresponding to the high-frequency three-step phase-shifting fringe image:

[0083]

[0084] In formulas (1) to (5), x and y represent pixel coordinates. Let A(x,y) represent the grayscale values ​​of the image signal of the modulated high-frequency phase-shifted stripe image, and B1(x,y) represent the high-frequency background intensity value, and B1(x,y) represent the high-frequency modulation depth value. This indicates the high-frequency wrapping phase value.

[0085] In some implementations, the image signal corresponding to the third low-frequency phase-shifting fringe image in the low-frequency three-step phase-shifting fringe image is generated based on the low-frequency background intensity value and the image signals corresponding to the first and second low-frequency phase-shifting fringe images in the low-frequency three-step phase-shifting fringe image using formulas (6) to (9).

[0086]

[0087] In formulas (6) to (9), This represents the grayscale value of the image signal corresponding to two low-frequency phase-shifted fringe images with different phases. B2(x,y) represents the grayscale value of the image signal corresponding to the generated third-phase low-frequency phase-shifted fringe image, and B2(x,y) represents the low-frequency modulation value. This indicates the low-frequency wrapping phase value.

[0088] In some implementations, the low-frequency wrapping phase value corresponding to the low-frequency three-step phase-shifting fringe image is determined based on the image signal corresponding to the low-frequency three-step phase-shifting fringe image using formula (10):

[0089]

[0090] The low-frequency wrapping phase value can be calculated using formula (10).

[0091] In some implementations, after the wrapping phase is extended to [0, 2π], a direct expansion method can be used to obtain the absolute phase value, which can be calculated using formula (11):

[0092]

[0093] In formula (11), round represents the round function, and φ1 represents the absolute phase value.

[0094] In some implementations, the heterodyne expansion method can be used. For example, when the projected high-frequency phase-shifted fringe image is 64 Hz and the low-frequency phase-shifted fringe image is 63 Hz, the absolute phase value can be solved according to formulas (12) to (14):

[0095]

[0096]

[0097] In formulas (12) to (14), λ1 represents the differential phase value (equivalent to 1-frequency phase), λ2 represents the high-frequency wavelength (number of pixels per cycle), and λ3 represents the low-frequency wavelength (number of pixels per cycle). eq φ1 represents the differential phase wavelength, and φ1 represents the absolute phase value.

[0098] In some implementations, embodiments of this application also provide a measuring device that employs the above-described coded sequential dual-frequency phase expansion method, including a projection module, a signal acquisition module, and a data processing module.

[0099] During operation, the projection module is used to cyclically project an absolute phase fringe sequence group onto the object under test. Each absolute phase fringe sequence group includes 5 absolute phase fringe images, which include the first and second low-frequency phase shift fringe images in the high-frequency three-step phase shift fringe image and the low-frequency three-step phase shift fringe image.

[0100] During operation, the signal acquisition module is used to continue the image signals corresponding to the last four phase-shifted fringe images of the previous absolute phase fringe sequence group, and acquire the image signal corresponding to the new one phase-shifted fringe image, replacing the image signal corresponding to the first one phase-shifted fringe image of the previous absolute phase fringe sequence group to obtain the image signal corresponding to the new absolute phase fringe sequence group; or it is used to continue the image signals corresponding to the last three phase-shifted fringe images of the previous absolute phase fringe sequence group, and acquire the image signals corresponding to the new two phase-shifted fringe images, replacing the image signals corresponding to the first two phase-shifted fringe images of the previous absolute phase fringe sequence group to obtain the image signal corresponding to the new absolute phase fringe sequence group.

[0101] During operation, the data processing module is used to solve for the phase and expand the image signal corresponding to the new absolute phase stripe sequence to obtain the absolute phase.

[0102] The beneficial effects of the embodiments of this application have been described in the above methods and will not be repeated here.

[0103] It should be noted that the information interaction and execution process between the above-mentioned devices / units are based on the same concept as the method embodiments of this application. For details on their specific functions and technical effects, please refer to the method embodiments section, and they will not be repeated here.

[0104] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0105] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0106] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0107] In the embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0108] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0109] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A dual frequency phase unwrapping method encoding continuation, characterized in that, The method comprises: Circulating the absolute phase fringe sequence group to the object to be measured, each absolute phase fringe sequence group comprising high-frequency three-step phase shift fringe images and first-step low-frequency phase shift fringe images and second-step low-frequency phase shift fringe images in low-frequency three-step phase shift fringe images; Continuing the image signals corresponding to the last 4 phase shift fringe images of the previous absolute phase fringe sequence group, and obtaining the image signals corresponding to the new 1 phase shift fringe image, replacing the image signals corresponding to the first 1 phase shift fringe image of the previous absolute phase fringe sequence group, to obtain the image signals corresponding to the new absolute phase fringe sequence group; or continuing the image signals corresponding to the last 3 phase shift fringe images of the previous absolute phase fringe sequence group, and obtaining the image signals corresponding to the new 2 phase shift fringe images, replacing the image signals corresponding to the first 2 phase shift fringe images of the previous absolute phase fringe sequence group, to obtain the image signals corresponding to the new absolute phase fringe sequence group; Solving and unwrapping the phase according to the image signals corresponding to the new absolute phase fringe sequence group to obtain the absolute phase; Circulating the absolute phase fringe sequence group to the object to be measured, comprising: Circulating the characteristic double-frequency phase shift fringe sequence to the object to be measured, the characteristic double-frequency phase shift fringe sequence comprising 4 groups of high-frequency three-step phase shift fringe images and first-step low-frequency phase shift fringe images and second-step low-frequency phase shift fringe images in 3 groups of low-frequency three-step phase shift fringe images arranged in sequence, the first-step low-frequency phase shift fringe images and the second-step low-frequency phase shift fringe images in each group of low-frequency three-step phase shift fringe images being inserted into the 4 groups of high-frequency three-step phase shift fringe images every 2 high-frequency phase shift fringe images, and the first-step low-frequency phase shift fringe image in the first group of low-frequency three-step phase shift fringe images being inserted between the first 2 high-frequency phase shift fringe images in the first group of high-frequency three-step phase shift fringe images; Obtaining the image signals corresponding to the new 1 phase shift fringe image, replacing the image signals corresponding to the first 1 phase shift fringe image of the previous absolute phase fringe sequence group, comprising: Obtaining the image signals corresponding to the new 1 high-frequency phase shift fringe image, replacing the image signals corresponding to the first 1 high-frequency phase shift fringe image of the previous absolute phase fringe sequence group; Obtaining the image signals corresponding to the new 2 phase shift fringe images, replacing the image signals corresponding to the first 2 phase shift fringe images of the previous absolute phase fringe sequence group, comprising: Continuing the image signals corresponding to the last 3 phase shift fringe images of the previous absolute phase fringe sequence group, obtaining the image signals corresponding to the new 1 low-frequency phase shift fringe image and the new 1 high-frequency phase shift fringe image, and replacing the image signals corresponding to the first 1 low-frequency phase shift fringe image and the first 1 high-frequency phase shift fringe image of the previous absolute phase fringe sequence group; Solving and unwrapping the phase according to the image signals corresponding to the new absolute phase fringe sequence group to obtain the absolute phase, comprising: Solving the high-frequency wrapped phase value and the high-frequency background intensity value corresponding to the high-frequency three-step phase shift fringe image according to the image signals corresponding to the high-frequency three-step phase shift fringe image; The high-frequency background intensity value is taken as a low-frequency background intensity value of a first-step low-frequency phase shift fringe image and a second-step low-frequency phase shift fringe image in the low-frequency three-step phase shift fringe image, an image signal corresponding to a third-step low-frequency phase shift fringe image in the low-frequency three-step phase shift fringe image is generated according to the low-frequency background intensity value and the image signals corresponding to the first-step low-frequency phase shift fringe image and the second-step low-frequency phase shift fringe image in the low-frequency three-step phase shift fringe image, and an image signal corresponding to the low-frequency three-step phase shift fringe image is obtained, and a low-frequency wrapped phase value corresponding to the low-frequency three-step phase shift fringe image is determined according to the image signal corresponding to the low-frequency three-step phase shift fringe image.

2. The method of claim 1, wherein, The method further comprises: The value range of the high frequency wrapped phase value and the low frequency wrapped phase value is extended to and the value range of the high frequency wrapped phase value and the low frequency wrapped phase value after the extension to is phase unwrapped to obtain an absolute phase value.

3. The method of claim 2, wherein, Phases of each group of high-frequency three-step phase shift fringe images are 0°, 120° and 240° respectively, and phases of a first-step low-frequency phase shift fringe image and a second-step low-frequency phase shift fringe image of each group of low-frequency three-step phase shift fringe images are 0° and 120° respectively.

4. The method of claim 3, wherein, A high-frequency wrapped phase value and a high-frequency background intensity value corresponding to the high-frequency three-step phase shift fringe image are solved according to the image signal corresponding to the high-frequency three-step phase shift fringe image by the following formula: wherein, denotes a pixel coordinate, , , denote the gray value of the image signal of the modulated high-frequency phase-shift fringe pattern, respectively, denotes a high-frequency background intensity value, denotes a high-frequency modulation depth value, denotes a high-frequency wrapping phase value.

5. The method of claim 4, wherein, An image signal corresponding to the third-step low-frequency phase shift fringe image in the low-frequency three-step phase shift fringe image is generated according to the low-frequency background intensity value and the image signals corresponding to the first-step low-frequency phase shift fringe image and the second-step low-frequency phase shift fringe image in the low-frequency three-step phase shift fringe image by the following formula: in, , This represents the grayscale value of the image signal corresponding to two low-frequency phase-shifted fringe images with different phases. This represents the grayscale value of the image signal corresponding to the low-frequency phase-shifted fringe image generated in step 3. Indicates the low-frequency modulation value. This indicates the low-frequency wrapping phase value.

6. The method of claim 5, wherein, A low-frequency wrapped phase value corresponding to the low-frequency three-step phase shift fringe image is determined according to the image signal corresponding to the low-frequency three-step phase shift fringe image by the following formula: 。 7. A measuring device, characterized by The method is applied to the coding continuation of the double-frequency phase unwrapping method in any one of claims 1 to 6, comprising: The projection module is configured to project a sequence of absolute phase fringe groups cyclically to the object to be measured, each sequence of absolute phase fringe groups comprising five absolute phase fringe images, and the five absolute phase fringe images comprising high-frequency three-step phase shift fringe images and first-step low-frequency phase shift fringe images and second-step low-frequency phase shift fringe images in low-frequency three-step phase shift fringe images; the projection module is configured to project a sequence of characteristic double-frequency phase shift fringes cyclically to the object to be measured, the sequence of characteristic double-frequency phase shift fringes comprising four groups of high-frequency three-step phase shift fringe images and first-step low-frequency phase shift fringe images and second-step low-frequency phase shift fringe images in three groups of low-frequency three-step phase shift fringe images arranged in sequence, the first-step low-frequency phase shift fringe images and the second-step low-frequency phase shift fringe images in each group of low-frequency three-step phase shift fringe images being inserted into the four groups of high-frequency three-step phase shift fringe images every two high-frequency phase shift fringe images, and the first-step low-frequency phase shift fringe image in the first group of low-frequency three-step phase shift fringe images being inserted between the first two high-frequency phase shift fringe images in the first group of high-frequency three-step phase shift fringe images. The signal acquisition module is configured to splice image signals corresponding to the last four phase shift fringe images of the previous absolute phase fringe sequence group, acquire image signals corresponding to a new phase shift fringe image, replace image signals corresponding to the first phase shift fringe image of the previous absolute phase fringe sequence group, and obtain image signals corresponding to a new absolute phase fringe sequence group; or splice image signals corresponding to the last three phase shift fringe images of the previous absolute phase fringe sequence group, acquire image signals corresponding to two new phase shift fringe images, replace image signals corresponding to the first two phase shift fringe images of the previous absolute phase fringe sequence group, and obtain image signals corresponding to a new absolute phase fringe sequence group; acquire image signals corresponding to a new phase shift fringe image, replace image signals corresponding to the first phase shift fringe image of the previous absolute phase fringe sequence group, including acquiring image signals corresponding to a new high-frequency phase shift fringe image, and replacing image signals corresponding to the first high-frequency phase shift fringe image of the previous absolute phase fringe sequence group; acquire image signals corresponding to two new phase shift fringe images, and replace image signals corresponding to the first two phase shift fringe images of the previous absolute phase fringe sequence group, including splicing image signals corresponding to the last three phase shift fringe images of the previous absolute phase fringe sequence group, acquiring image signals corresponding to a new low-frequency phase shift fringe image and a new high-frequency phase shift fringe image, and replacing image signals corresponding to the first low-frequency phase shift fringe image and the first high-frequency phase shift fringe image of the previous absolute phase fringe sequence group; The data processing module is configured to perform phase solving and unwrapping to obtain absolute phase according to image signals corresponding to the new absolute phase fringe sequence group, solve high-frequency wrapped phase values and high-frequency background intensity values corresponding to the high-frequency three-step phase shift fringe image according to image signals corresponding to the high-frequency three-step phase shift fringe image, take the high-frequency background intensity values as low-frequency background intensity values of the first low-frequency phase shift fringe image and the second low-frequency phase shift fringe image in the low-frequency three-step phase shift fringe image, generate image signals corresponding to the third low-frequency phase shift fringe image in the low-frequency three-step phase shift fringe image according to the low-frequency background intensity values and image signals corresponding to the first low-frequency phase shift fringe image and the second low-frequency phase shift fringe image in the low-frequency three-step phase shift fringe image, obtain image signals corresponding to the low-frequency three-step phase shift fringe image, and determine low-frequency wrapped phase values corresponding to the low-frequency three-step phase shift fringe image according to the image signals corresponding to the low-frequency three-step phase shift fringe image.

Images