3D shape measuring device

Abstract

A three-dimensional shape measuring apparatus according to one embodiment includes a projector that irradiates a pattern light onto the target object; and an imaging device configured to image the target object, the imaging device including an optical system including at least one lens defining an optical axis, and a binary phase filter arranged on the optical axis of the optical system to transmit light, and configured to form an image using light that has passed through the at least one lens and the binary phase filter. The binary phase filter includes a first portion including at least one pattern extending in a circumferential direction around the optical axis, and a second portion separated from the first portion. The first portion and the second portion have different thicknesses in the optical axis direction.

Description

Technical Field

[0001] The present disclosure relates to a three-dimensional shape measurement apparatus that measures the three-dimensional shape of an object.

Background Art

[0002] Various methods for measuring a three-dimensional image of an object are utilized in industrial sites. Among them, a method of measuring a moire pattern generated by irradiating a certain pattern light on the object and then acquiring the three-dimensional image of the object is utilized. Such a moire-based three-dimensional image measurement technology is applied in various fields such as inspecting wrinkles, stains, and unevenness on the surface of manufactured products, or inspecting the quality of component mounting and soldering on semiconductor substrates.

[0003] In order to accurately measure a three-dimensional shape, a high resolution and a high depth of field of an imaging device are required. However, as the depth of field of the imaging device increases, the resolution decreases, and conversely, if the resolution is increased, the depth of field becomes shallow. Therefore, there is a trade-off relationship between the depth of field and the resolution.

Summary of the Invention

Problems to be Solved by the Invention

[0004] An embodiment of the present disclosure provides an optical element or a three-dimensional shape measurement apparatus configured to prevent or minimize a decrease in resolution while increasing the depth of an imaging device.

Means for Solving the Problems

[0005] This disclosure provides embodiments of a three-dimensional shape measuring apparatus for measuring the three-dimensional shape of an object. A typical embodiment of the three-dimensional shape measuring apparatus includes: a projector for illuminating the object with patterned light; an optical system configured to image the object and including at least one lens defining an optical axis; and an imaging device configured to form an image using the light that has passed through the at least one lens and the binary phase filter, and including a binary phase filter positioned on the optical axis of the optical system and arranged to transmit light. The binary phase filter includes a first portion including at least one pattern extending circumferentially around the optical axis, and a second portion separated from the first portion. The first portion and the second portion have different thicknesses in the direction of the optical axis.

[0006] In one embodiment, the thickness of the first portion in the optical axis direction may be smaller than the thickness of the second portion in the optical axis direction.

[0007] In one embodiment, n1 is the refractive index of air, n2 is the refractive index of the binary phase filter, and λ center When is the center wavelength of the light emitted from the projector, the difference in thickness between the first and second parts in the optical axis direction is The filename can be JPEG0007863798000001.jpg1120.

[0008] In one embodiment, the first portion may include a plurality of concentric and radially separated patterns.

[0009] In one embodiment, the at least one pattern of the first portion may include an annular pattern.

[0010] In one embodiment, the second portion may be the remaining portion of the binary phase filter after the first portion has been removed.

[0011] In one embodiment, the at least one lens may include two lenses that share the optical axis and are spaced apart from each other, and the binary phase filter may be positioned between the two lenses.

[0012] In one embodiment, the first portion may be formed by one of the following: thin film deposition, etching, imprinting, or hologram film.

[0013] In one embodiment, the patterned light may be a sine wave fringe pattern.

[0014] In one embodiment, the system may further include at least one processor configured to generate data relating to the three-dimensional shape of an object based on an image of the pattern light irradiated onto the object, which is acquired by the imaging device. [Effects of the Invention]

[0015] According to one embodiment of the present disclosure, a three-dimensional shape measuring device can have high resolution while also having a deep depth.

[0016] According to one embodiment of this disclosure, non-contact three-dimensional shape measurement is possible without the need to directly contact a component such as a probe with the surface of a three-dimensional object. Furthermore, since the three-dimensional shape of the object can be measured while capturing images of the object in real time, the changes in the surface morphology of the object can be measured in real time. In addition, because the imaging device has a deep depth of field, objects with a relatively large area can be captured with high resolution. [Brief explanation of the drawing]

[0017] [Figure 1] This figure shows a three-dimensional shape measuring device according to one embodiment. [Figure 2] This figure shows an imaging device to which a binary phase filter that increases the depth of field according to one embodiment is applied. [Figure 3]It is a plan view of a binary phase filter according to an embodiment. [Figure 4] It is a cross-sectional view of the binary phase filter in FIG. 3 cut along line I-I'. [Figure 5] It is a flowchart of a binary phase filter optimization method according to an embodiment. [Figure 6] It is a flowchart of an embodiment in the stage of optimizing the binary phase filter in FIG. 5. [Figure 7] It is a flowchart of an embodiment in the stage of calculating the video quality in FIG. 6 and determining whether the video quality meets the target quality. [Figure 8] It is a flowchart showing the process of optimizing the binary phase filter by a particle swarm optimization algorithm according to an embodiment in the binary phase filter optimization stage in FIG. 5. [Figure 9] It is a conceptual diagram showing the depth of field when there is no binary phase filter. [Figure 10] It is a conceptual diagram showing the depth of field extended by the binary phase filter. [Figure 11] It is a conceptual diagram showing the depth of focus when there is no binary phase filter. [Figure 12] It is a conceptual diagram showing the depth of focus extended by the binary phase filter.

Modes for Carrying Out the Invention

[0018] The embodiments of the present disclosure are exemplified for the purpose of explaining the technical idea of the present disclosure. The scope of rights related to the present disclosure is not limited to the embodiments presented below or the specific descriptions related to these embodiments.

[0019] All technical and scientific terms used in this disclosure have meanings that would be generally understood by a person with ordinary skill in the art to which this disclosure pertains, unless otherwise specified. All terms used in this disclosure have been chosen for the purpose of making this disclosure clearer, and not to limit the scope of rights relating to this disclosure.

[0020] Expressions such as "includes," "equipped with," and "possess" used in this disclosure should be understood as open-ended terms that may include other embodiments, unless otherwise specified in the phrase or sentence containing such expression.

[0021] Unless otherwise specified, singular expressions described in this disclosure may include plural meanings, and this applies equally to singular expressions described in the claims.

[0022] The terms "First," "Second," etc., used in this disclosure are used to distinguish between multiple components and do not limit the order or importance of those components.

[0023] The expression "based on" as used in this disclosure is used to describe one or more factors that influence an act or action of decision, judgment, or action described in the phrase or sentence containing the expression, and the expression does not exclude any additional factors that influence an act or action of decision, judgment, or action.

[0024] Embodiments of this disclosure will be described below with reference to the attached drawings. In the attached drawings, identical or corresponding components are denoted by the same reference numerals. In the following description of embodiments, redundant descriptions of identical or corresponding components may be omitted. However, the omission of a description of a component does not mean that the component is not included in a particular embodiment.

[0025] A three-dimensional shape measuring device according to one embodiment of the present disclosure will be described below with reference to Figures 1 to 4.

[0026] Figure 1 shows a three-dimensional shape measuring device 100 according to one embodiment.

[0027] The 3D shape measuring device 100 measures the three-dimensional shape of an object by capturing an image of patterned light projected onto the object by a projector 120. In one embodiment, the 3D shape measuring device 100 includes an imaging device 110 and a projector 120. The 3D shape measuring device 100 may further include an analysis device 130.

[0028] The imaging device 110 may be configured to image the target object 200. The imaging device 110 includes an optical system having a lens that defines the optical axis. The optical system may include a binary phase filter (binary phase filter 140 in Figure 2), which will be described later. The lens may include at least one lens element. The imaging device 110 includes an image sensor. The image sensor is configured to collect light that has passed through the lens and to generate image data for the target object 200.

[0029] The projector 120 may be configured to irradiate a target object 200 with patterned light. In one embodiment, the projector 120 can irradiate the surface of the target object 200 with structured patterned light. For example, the projector 120 can irradiate the target object 200 with light in a sinusoidal fringe pattern.

[0030] The pattern light is phase-modulated as it is irradiated onto the three-dimensional surface of the object 200, and the imaging device 110 acquires an image of the phase-modulated pattern light. The analysis device 130 may include at least one processor configured to generate data related to the three-dimensional shape of the object 200 based on the image of the pattern light acquired by the imaging device 110.

[0031] For example, when light with a fringe pattern is shone onto the object 200, the imaging device 110 can capture a fringe pattern that is phase-modulated by the object's height distribution. The processor can calculate the phase modulation using fringe analysis techniques (including Fourier transform methods, phase stepping, and spatial phase detection techniques). The processor can use an appropriate phase unwrapping algorithm to obtain a continuous phase distribution and correct and convert the acquired continuous phase distribution into actual 3D height information. However, in this disclosure, the method for analyzing the pattern that has been shone onto the object 200 and modulated to generate data relating to the 3D shape may be implemented in a manner different from that described above.

[0032] To accurately measure a three-dimensional shape, the patterned light illuminating the object 200 must be acquired with high resolution (or resolving power). Resolution is an indicator of the imaging capability of the imaging device, and refers to the ability to distinguish between two objects that are far apart from each other. On the other hand, the depth of field of the imaging device 110 refers to the area in the image that can be considered in focus. In order to clearly measure the image of the patterned light illuminating the surface of the three-dimensional object 200, the depth of field of the imaging device 110 must be deep enough to cover the range of distances between the three-dimensional shape and the imaging device 110 (or extended).

[0033] Figure 2 shows an imaging device 110 to which a binary phase filter 140 for increasing depth of field according to one embodiment is applied. Referring to Figure 2, when a projector (for example, the projector 120 in Figure 1) illuminates the first region 201, second region 202, and third region 203 of the object 200 with patterned light, the imaging device 110 must capture an image of the patterned light with high resolution across all regions in order for the three-dimensional shape of the object 200 to be accurately measured. In other words, the depth of field of the imaging device 110 should be set so as to cover the first region 201 to the third region 203 shown above. For example, if we define the image pattern of patterned light illuminating a first region 201 at a first distance d1 from the imaging device 110 as "A", the image pattern of patterned light illuminating a second region 202 at a second distance d2 as "B", and the image pattern of patterned light illuminating a third region 203 at a third distance d3 as "C", then in order for "A", "B", and "C" to be clearly imaged, the depth of field of the imaging device 110 must include at least the interval corresponding to the first distance d1 to the third distance d3.

[0034] On the other hand, depth of field is inversely proportional to the numerical aperture (or aperture value) of the lens, and resolution is proportional to the numerical aperture of the lens. Therefore, there is a problem that resolution decreases when depth of field is extended. In one embodiment, a binary phase filter 140 may be applied to extend depth of field while preventing or minimizing the decrease in resolution. In one embodiment, the imaging device 110 may include the binary phase filter 140. The binary phase filter 140 may optically interact with the optical elements constituting the optical system. In this disclosure, the optical system may be understood as a concept including the binary phase filter 140. That is, the binary phase filter 140 can constitute part of the optical system of the imaging device 110. For example, referring to Figure 2, the binary phase filter 140 may be placed between a first lens 111 and a second lens 112 arranged along the optical axis O. However, Figure 2 is merely an exemplary form in which the binary phase filter 140 is placed inside the imaging device 110, and the imaging device 110 of this disclosure is not limited to the illustrated embodiment.

[0035] By including a binary phase filter 140 in the imaging device 110, all three-dimensional surfaces (e.g., first region 201 to third region 203) within the range of first distance d1 to third distance d3 can be imaged with high resolution.

[0036] Figure 3 is a plan view of a binary phase filter 140 according to one embodiment. Figure 4 is a cross-sectional view of the binary phase filter 140 of Figure 3, cut along line I-I'.

[0037] The binary phase filter 140 may include a first portion 141 containing at least one pattern extending circumferentially around the optical axis O, and a second portion 142 separated from the first portion 141. The at least one pattern may include an annular pattern. For example, the first portion 141 may include a first pattern 141a and a second pattern 141b. In the binary phase filter 140, the second portion 142 may be defined as the portion excluding the first portion 141.

[0038] The first part 141 may include a plurality of patterns that are spaced apart from each other and concentric. The plurality of patterns may be spaced apart from each other radially. At least one of the plurality of patterns may be annular patterns. As an example, the first part may consist of a circular pattern defined as having an inner diameter of 0 and at least one annular pattern. As another example, the first part may consist only of a plurality of annular patterns.

[0039] Multiple patterns may have different widths (differences between inner and outer diameters). Multiple patterns may have different inner diameters. For example, referring to Figures 3 and 4, the first part 141 may include a first pattern 141a and a second pattern 141b. The first pattern 141a and the second pattern 141b are radially separated from each other and are concentric.

[0040] The aforementioned patterns include patterns with an inner diameter of 0. For example, if the inner diameter of the first pattern 141a is 0, contrary to the illustration, the first pattern 141a may be a circular pattern. Also, in the illustrated embodiment, the first part 141 includes two patterns 141a and 141b, but this is merely an example, and it may include one or three or more patterns.

[0041] In one embodiment, the first part 141 and the second part 142 may be configured such that the optical phase difference between the light passing through the first part 141 and the light passing through the second part 142 reaching a single point is 180° (degrees).

[0042] In one embodiment, the first part 141 and the second part 142 may be configured such that the optical path difference between the light passing through the first part 141 and the light passing through the second part 142, of the light reaching a single point, is half the center wavelength of the light emitted from the light source (for example, light emitted from the projector 120).

[0043] In one embodiment, the light passing through either the first section 141 or the second section 142 may have a phase difference of 180° compared to the light passing through the other section 141 or the second section 142, due to a phase-only spatial light modulator (SLM) and a grating light bulb (GLV). Here, it is assumed that the light passing through the first section 141 and the light passing through the second section 142 reach the same point.

[0044] In one embodiment, the optical path difference between the first portion 141 and the second portion 142 may be embodied by a physical step difference between the first portion 141 and the second portion 142. For example, referring to Figure 4, the binary phase filter 140 may have different thicknesses in the first portion 141 and the second portion 142. The physical step difference between the first portion 141 and the second portion 142 may be embodied by methods such as imprinting, thin film deposition, wet / dry etching, or hologram film deposition.

[0045] In one embodiment, the first portion 141 and the second portion 142 may have different thicknesses in the direction aligned with the optical axis O (or in the direction of the optical axis). For example, the thickness t1 of the first portion 141 in the direction of the optical axis may be smaller than the thickness t2 of the second portion 142 in the direction of the optical axis.

[0046] In one embodiment, the thickness difference (t2-t1) between the first part 141 and the second part 142 may be determined such that the path difference between the light passing through the first part 141 and the light passing through the second part 142, out of the light reaching a single point, is half the central wavelength.

[0047] For example, the difference in thickness (Δt) between the first part 141 and the second part 142 may be determined by mathematical formula 1.

[0048]

number

[0049] n1 is the refractive index of air, n2 is the refractive index of the binary phase filter 140, and λ center This is the center wavelength of the light emitted from projector 120. (λ) center The spectrum (intensity by wavelength) of light emitted from projector 120 can be calculated using mathematical formula 2.

[0050]

number

[0051] f(λ) is the spectral flux at wavelength λ.

[0052] On the other hand, the binary phase filter 140 shown in Figures 3 and 4 is merely an exemplary embodiment, and the binary phase filter 140 of this disclosure is not limited thereto.

[0053] In one embodiment, the binary phase filter 140 may be configured to extend the depth of field while preventing or minimizing a decrease in resolution. In one embodiment, the binary phase filter 140 may be designed to be optimized for the optical system to which it is applied. In one embodiment, optimization of the binary phase filter 140 can result in an imaging device 110 capable of capturing a three-dimensional surface with a target resolution (or resolution) in a target depth of field range.

[0054] The binary phase filter optimization method applied to the 3D shape measurement imaging device 110 will be described below with reference to Figures 5 to 8.

[0055] Figure 5 is a flowchart of a binary phase filter optimization method according to one embodiment. Figure 6 is a flowchart of one embodiment of the steps for optimizing the binary phase filter in Figure 5. Figure 7 is a flowchart of one embodiment of the video quality calculation step 231 and the step 233 for determining whether the video quality conforms to the target quality in Figure 6. Figure 8 is a flowchart of the process of optimizing the binary phase filter using the particle swarm optimization algorithm according to one embodiment of the binary phase filter optimization step 230 in Figure 5.

[0056] In the flowcharts shown in Figures 5 to 8, process stages, method stages, and algorithms are described in a sequential order; however, these processes, methods, and algorithms may be configured to operate in any appropriate order. In other words, the stages of the processes, methods, and algorithms described in the various embodiments of this disclosure do not need to be performed in the order described herein. Furthermore, even if some stages are described as being performed non-simultaneously, in other embodiments, some of those stages may be performed simultaneously. Moreover, the illustrative examples of processes in the drawings do not mean that the illustrated processes are excluded from other variations and modifications, nor do they mean that any illustrated process or any of its stages is essential to one or more of the various embodiments of this disclosure, nor do they mean that the illustrated processes are preferred.

[0057] Referring to Figure 5, the binary phase filter optimization method includes a step 210 for selecting an initial phase filter. The binary phase filter optimization method includes a step 230 for optimizing the binary phase filter based on the initial phase filter. The binary phase filter optimization method includes a step 250 for determining the optimized binary phase filter as the final binary phase filter.

[0058] In one embodiment, prior to optimizing the binary phase filter, the binary phase filter may be represented in matrix form. The radius of the circle corresponding to the boundary between the first part 141 and the second part 142 may be set as a variable. For example, a matrix The binary phase filter, represented as JPEG0007863798000004.jpg642, has a radius of The circle in JPEG0007863798000005.jpg631 may be the boundary between the first part 141 and the second part 142, which correspond to a phase filter where they are adjacent. The variables that constitute the binary phase filter are ( JPEG0007863798000006.jpg630) may be selected or determined to have a value between 0 and the pupil radius in the conditional expression. The values ​​of the variables that define the binary phase filter are adjusted through an optimization process, and when the optimal solution is determined, the optimal binary phase filter may be determined by the values ​​of the variables.

[0059] Referring to Figure 6, step 230, which optimizes the binary phase filter, may include step 231, which calculates the image quality based on the current binary phase filter. In step 231, the image quality may be numerically evaluated. When step 231 is performed for the first time, the current binary phase filter may be determined in the initial binary phase filter selection step 210 of Figure 5.

[0060] The aforementioned step 230 may include a step 233 in which it is determined whether or not the video quality conforms to the target quality. In step 233, it may be determined whether or not to adjust the binary phase filter based on whether or not the video quality based on the current phase filter conforms to the target quality.

[0061] Step 230 may include step 235, which adjusts the binary phase filter if the image quality does not conform to the target quality in step 233. In this disclosure, adjusting the binary phase filter means adjusting the values ​​of the variables that define the binary phase filter. After step 235, step 231 is performed again. In this process, the binary phase filter may be adjusted several times. "Current binary phase filter" means the most recent binary phase filter at the time a particular step is performed. For example, in the first step 233, the current binary phase filter is the initial binary phase filter, and in step 233 performed after step 235, the current binary phase filter is the binary phase filter adjusted in step 235.

[0062] If the video quality matches the target quality in step 233, step 230, which optimizes the binary phase filter, is terminated. In this case, step 250, in which the current binary phase filter is determined to be the final binary phase filter, may be performed.

[0063] Referring to Figure 7, in one embodiment, the system function of the optical system constituting the imaging device (for example, the imaging device 110 in Figure 1), and the optical transfer function calculated from the system function may be used to evaluate the image quality. Here, the system function is the system function of the optical system excluding the binary phase filter.

[0064] A system function is a function that simulates the optical system included in an imaging device, and includes information about the optical elements that make up the optical system, excluding the binary phase filter. For example, a system function may include information about the number of lenses that make up the optical system, the shape of the lenses (convex or concave), the spacing between lenses, the refractive index of the lenses, the Abbe number of the lenses, the aperture, filters, etc. System functions may be provided by optical design software such as Zemax, CodeV, LightTools, ASAP, and TracePro.

[0065] The performance of an optical system (i.e., the quality of the image captured by the optical system) may be evaluated by the convolution of the point spread function (PSF) and the image. The optical transfer function (OTF) has a Fourier transform relationship with the point spread function, and both functions may be calculated from the system function. By convolution of the point spread function calculated using the system function corresponding to a specific optical system with a test image, an image of a test target captured using that optical system can be reproduced. As test images, for example, "USAF 1951," "Ronchi Ruling," and "Star," which are designed to help evaluate and correct the performance of the image system, may be used.

[0066] The performance of the system function may be evaluated by replicating an image using an optical transfer function and evaluating the quality of the replicated image. The quality of the image may be quantified from the replicated image as an evaluation value related to image quality, and the quality of the image may be evaluated based on the quality evaluation value. The method for evaluating the quality of the image may include a full-reference evaluation method that refers to an undistorted image, or a no-reference evaluation method that does not refer to an undistorted image. Full-reference evaluation methods may include MSE (mean square error), PSNR (peak signal to noise ratio), SSIM (structure similarity), etc. No-reference evaluation methods may include BRISQUE (Blind / Referenceless Image Spatial Quality Evaluator), NIQE (Natural Image Quality Evaluator), PIQE (Perception-based Image Quality Evaluator), etc.

[0067] Referring to Figures 6 and 7, step 231 for calculating image quality may, in one embodiment, include step 241 for calculating the overall system function for the optical system to which the binary phase filter is currently applied. The system function of the optical system excluding the binary phase filter is fixed, or if the current binary phase filter is changed during optimization, the overall system function changes accordingly.

[0068] Step 231 may include step 243, which calculates the optical transfer function in the target depth of field interval from the overall system function calculated in step 241 above. From the overall system function, one or more optical transfer functions that can replicate a subject in the target depth of field from the optical system may be derived. For example, when the target depth of field interval is at a distance of d1 to d2 from the optical system, n+1 optical transfer functions may be calculated that can replicate a subject at a distance of d1, d1+(d2-d1)*1 / n, d1+(d2-d1)*2 / n, ..., d1+(d2-d1)*(n-1) / n, and d2 from the optical system. In this disclosure, an optical transfer function that can replicate a subject at a specific distance (d) means an optical transfer function whose result, when convoluted with a test image, is configured to replicate the result of an imaging device capturing a test image at the corresponding distance (d) from the imaging device.

[0069] The aforementioned step 231 may include a step 245 in which an image of a test image is reproduced in the target depth range based on the optical transfer function calculated in the step 243 above. In step 245, an image of a test image within a distance range corresponding to the target depth of field from the imaging device may be reproduced by combining a plurality of optical transfer functions corresponding to the target depth range with the test image. If a plurality of optical transfer functions corresponding to the target depth of field have been calculated in step 243, the image reproduction may be performed using all of the plurality of optical transfer functions.

[0070] Step 231 may include step 247, which calculates a quality evaluation value based on the image previously copied in step 245. Step 230 may include step 249, which calculates the cost corresponding to the difference between the quality evaluation value calculated in step 247 and the target quality evaluation value.

[0071] In step 249, the performance of the imaging device in the target depth range may be evaluated based on the optical transfer function for the target depth range. In this disclosure, evaluating the performance of the imaging device (or image quality) means calculating a quality evaluation value that indicates whether the image quality is high or low. The image of the test image may be copied in the target depth range based on the optical transfer function, and the quality evaluation value may be calculated based on the copied image. It may be determined whether the quality evaluation value in the target depth range is close to the target quality evaluation value. In this disclosure, the difference between the quality evaluation value in the target depth range and the target quality evaluation value may be referred to as "cost". If the current quality evaluation value is close to the target quality evaluation value, the cost approaches 0, which indicates excellent image quality. Therefore, in this disclosure, "cost" may also be understood as a type of quality evaluation value. When the cost becomes sufficiently small, the current binary phase filter can be determined to be the final binary phase filter.

[0072] The cost (y) may be calculated, for example, by mathematical formula 3.

[0073]

number

[0074] f is the video quality evaluation value, f0 is the target video quality evaluation value. JPEG0007863798000008.jpg76 is the binary phase filter matrix in the tth iteration, z is the index assigned according to the distance between the imaging device and the target object 200, and λ is the regularization coefficient. For example, the quality evaluation value of the video that replicates the test image at a position corresponding to the lower limit of the target depth of field interval is The file is JPEG0007863798000009.jpg615, and the quality evaluation value of the video is a reproduction of a test image located at the upper limit of the target depth of field interval. The filename can be JPEG0007863798000010.jpg615.

[0075] Step 261 is one of the steps 233 in which the image quality in Figure 6 is determined to conform to the target quality. In step 261, it is determined whether the cost (y) has reached its minimum value, and depending on the result, further optimization may be performed or the optimization may be terminated. Reaching the minimum value of cost (y) means that the cost will not decrease significantly further (or beyond a specified critical value), or the cost will become zero. If optimization is performed, the binary phase filter may be adjusted in step 235 in a direction that minimizes the cost (y).

[0076] Referring to Figures 6 and 8, in one embodiment, the binary phase filter adjustment step 235 may be performed using a PSO (particle swarm optimization) algorithm. Step 235 may include a step 281 for setting up N initial binary phase filters. Step 235 may include a step 283 for evaluating the image quality for each of the N current binary phase filters. Step 235 may include a step 285 for determining whether the best image quality evaluated in step 283 conforms to the target quality. If the image quality did not conform to the target quality in step 285, step 235 may include a step 287 for adjusting the N binary phase filters using the PSO algorithm.

[0077] PSO (Progressive Optimization System) involves multiple agents (or particles) exchanging information with each other while simultaneously combining stored information to find the optimal solution. Because the agents optimize themselves by exchanging information with one another, even if one agent converges to a local optimum, the entire system of agents can converge to a global optimum.

[0078] In one embodiment, a binary phase filter having j components is a matrix It can be expressed as JPEG0007863798000011.jpg641, but in the PSO algorithm, multiple binary phase filters are optimized in parallel. When N binary phase filters are used, they are, It may be expressed as JPEG0007863798000012.jpg644. In step 281 above, the N initial binary phase filters are It is acceptable to set it to JPEG0007863798000013.jpg645. The values ​​that make up JPEG0007863798000014.jpg645 may be determined arbitrarily or predetermined.

[0079] In one embodiment, the steps of evaluating the video quality 283 until the highest video quality conforms to the target quality, determining whether the video quality conforms to the target quality 285, and adjusting the binary phase filters 287 may be repeated sequentially. In step 287, N binary phase filters are adjusted in parallel. For example, when step 287 is repeated for the (t+1)th time, the i-th (i=1,2,3,...,N)-th binary phase filter may be adjusted based on the local best solution of the i-th binary phase filter up to the tth time and the global best solution of the entire binary phase filter up to the tth time.

[0080] In step 287 above, the local best solution of the i-th binary phase filter means the historical best solution of the i-th binary phase filter that showed the best quality evaluation value (or minimum cost) during the t adjustment process. After undergoing t adjustments, the i-th binary phase filter The image may have solutions such as JPEG0007863798000015.jpg653, and the solution that exhibits the highest quality rating (or lowest cost) among them may be defined as the local best solution of the i-th binary phase filter.

[0081] In step 287, the global best solution of the overall binary phase filter represents the best solution in the history of the binary phase filter, showing the best result value after t adjustment processes. Through t adjustments, the binary phase filter, JPEG0007863798000016.jpg642;...; The solution may be as follows: JPEG0007863798000017.jpg644. The solution that exhibits the highest quality evaluation value (or the lowest cost) among them may be defined as the global best solution for the overall binary phase filter.

[0082] For example, the (t+1)th adjustment of the binary phase filter performed in step 287 may be determined by mathematical formulas 4 and 5.

[0083]

number

[0084]

number

[0085] JPEG0007863798000020.jpg712 is the i-th binary phase filter matrix having j components after t adjustments, JPEG0007863798000021.jpg612 is the value used to adjust the binary phase filter matrix in the tth adjustment, where r1 and r2 are random numbers between 0 and 1, and c1 and c2 are the cognitive coefficient and social coefficient, respectively. JPEG0007863798000022.jpg614 is the local best solution of the i-th binary phase filter after the t-th adjustment. JPEG0007863798000023.jpg714 represents the global highest solution among all binary phase filters after the t-th adjustment.

[0086] In step 287, the image quality of the binary phase filter adjusted by the PSO algorithm is evaluated again in step 283, and in step 285, it may be determined whether the image quality conforms to the target quality. Based on the result of step 285, a further adjustment step 287 may be performed, or the optimization may be completed. Once the optimization is complete, in step 289, the binary phase filter that conforms to the target quality may be determined to be the final binary phase filter.

[0087] The depth extension function using binary phase filters will be explained below with reference to Figures 9 to 12.

[0088] Figure 9 is a conceptual diagram showing the depth of field without a binary phase filter, and Figure 10 is a conceptual diagram showing the depth of field extended by a binary phase filter.

[0089] Figure 9 shows the result of photographing the object 200 with the imaging device 110 without a binary phase filter. The depth of field of the imaging device 110 covers only the second region 202, so only "B" in the second region 202 is clearly photographed, while the photographic results for the first region 201 and the third region 203 ("A" and "C") are not clear.

[0090] On the other hand, Figure 10 shows that the depth of field is extended by the binary phase filter 140. The depth of field of the imaging device 110 covers not only the second region 202 but also the first region 201 and the third region 203, so that all shapes ("A", "B", and "C") in the first region 201, the second region 202, and the third region 203 can be captured clearly.

[0091] In other words, when photographing the target object 200 using the imaging device 110 in Figure 9, the binary phase filter 140 described in Figures 1 to 4 may be applied in order to clearly photograph all of the first region 201, the second region 202, and the third region 203, and the binary phase filter 140 may be designed by the optimization method shown in Figures 5 to 8.

[0092] Figure 11 is a conceptual diagram showing the depth of focus without a binary phase filter, and Figure 12 is a conceptual diagram showing the depth of focus extended by a binary phase filter.

[0093] Although this disclosure describes a method by which the binary phase filter 140 extends the depth of field, the binary phase filter 140 may also be used to extend the depth of focus. The depth of focus is the range in which the image plane is considered to be in focus.

[0094] Referring to Figures 11 and 12, the appearance of the focal point may change depending on whether or not the binary phase filter 140 is present. Figures 11 and 12 show how light emitted from a point source is refracted by the optical system 300 and then focuses. The further the focal shape is from the direction of light propagation u, the longer the focus interval, which means a deeper depth of field. When the binary phase filter 140 is present, the focus interval s2 may be extended compared to the focus interval s1 when the binary phase filter 140 is absent. Using the binary phase filter 140, even if the focus interval is extended from s1 to s2, the extension of the focal shape in the direction v perpendicular to the direction of light propagation u is suppressed, so the focus can remain sharp even if the depth of field is extended.

[0095] Although the above method has been described with reference to specific embodiments, the method can also be embodied as computer-readable code on a computer-readable recording medium. A computer-readable recording medium includes any type of recording device on which data readable by a computer system is stored. Examples of computer-readable recording media may include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage device, etc. Furthermore, the computer-readable recording medium may be distributed across a network of connected computer systems, and the computer-readable code may be stored and executed in a distributed manner. Functional programs, code, and code segments for embodying the above embodiments can be readily inferred by programmers in the art to which this disclosure belongs.

[0096] While the technical concept of this disclosure has been explained above through some embodiments and examples shown in the attached drawings, it should be understood that various substitutions, modifications, and alterations may be made without departing from the technical concept and scope of this disclosure as understandable to a person with ordinary skill in the art to which this disclosure pertains. Furthermore, such substitutions, modifications, and alterations should be considered to fall within the scope of the attached claims.

Claims

1. A three-dimensional shape measuring device for measuring the three-dimensional shape of an object, A projector that irradiates the target object with patterned light, The imaging device includes an optical system configured to image the target object, having at least one lens defining an optical axis and a binary phase filter positioned on the optical axis to transmit light, and configured to form an image using the light that has passed through the at least one lens and the binary phase filter, The binary phase filter includes a first portion having at least one pattern extending circumferentially around the optical axis, and a second portion separated from the first portion, wherein the first portion and the second portion have different thicknesses in the direction of the optical axis aligned with the optical axis. When n1 is the refractive index of air, n2 is the refractive index of the binary phase filter, and λcenter is the center wavelength of the light emitted from the projector, the difference in thickness between the first part and the second part in the optical axis direction is: And, The at least one lens includes two lenses that share the optical axis and are spaced apart from each other, The binary phase filter is positioned between the two lenses in a three-dimensional shape measuring device.

2. The three-dimensional shape measuring device according to claim 1, wherein the thickness of the first portion in the optical axis direction is smaller than the thickness of the second portion in the optical axis direction.

3. The three-dimensional shape measuring apparatus according to claim 1, wherein the first part includes a plurality of concentric and radially separated patterns.

4. The three-dimensional shape measuring device according to claim 1, wherein the at least one pattern of the first portion includes an annular pattern.

5. The three-dimensional shape measuring apparatus according to claim 1, wherein the second part is the remaining part of the binary phase filter after removing the first part.

6. The three-dimensional shape measuring apparatus according to claim 1, wherein the first part is formed by one of thin film deposition, etching, imprinting, or hologram film.

7. The three-dimensional shape measuring apparatus according to claim 1, wherein the pattern light is a sine wave fringe pattern.

8. The three-dimensional shape measuring apparatus according to claim 1, further comprising at least one processor configured to generate data related to the three-dimensional shape of an object based on an image of the pattern light irradiated onto the object, acquired by the imaging device.

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