A three-dimensional measuring instrument based on fiber-coded structured light projection

Abstract

The present invention relates to the field of optics and three-dimensional measurement technology, and specifically discloses a three-dimensional measuring instrument based on fiber optic coded structured light projection, comprising: a light source unit for emitting a light beam; a structured light projection unit for transmitting the light beam through a fiber optic bundle, combining all the fiber optic bundles, encoding them by longitudinal alternating arrangement at the combined bundle end face, and projecting the coded pattern through a projection lens. The present invention adopts optical fiber illumination, and encodes by the combined bundle arrangement sequence of the fiber optic bundle to realize a sinusoidal structured light pattern, so that the three-dimensional measuring instrument based on fiber optic coded structured light projection provided by the present invention can ensure that there is a strict and accurate phase difference between the projected fringes, and obtains an accurate phase shift pattern by controlling the timing of the light source, so that the present invention can achieve higher accuracy and reliability when performing three-dimensional measurement of the object to be measured.

Description

Technical Field

[0001] The present invention relates to the field of optics and three-dimensional measurement technology, and in particular to a three-dimensional measuring instrument based on optical fiber coded structured light projection. Background Art

[0002] The structured light 3D measurement equipment based on fiber coding currently faces many problems in the fields of moving objects and micro-expressions on human faces. The DLP optical projection system has the advantages of high contrast and high precision, but since it takes 80ms to project each frame, multi-frame projection and reconstruction will affect its measurement application in moving objects and micro-variations. In addition, its complex structure and high cost also limit its application. Most structured light projection devices have practical engineering problems that are difficult to take into account in terms of system implementation and control methods.

[0003] Although the existing 3D cameras are highly integrated, the 3D face cameras on the market have problems such as high acquisition accuracy but slow speed, high cost and large size (such as the high-precision 3D full-face camera developed by Sichuan University Zhisheng Software Co., Ltd.), small infrared galvanometer 3D cameras have changed the overall design, but the maintenance cost is high, high-precision translation grating 3D face measurement cameras have high accuracy but have motion mechanisms, and their long-term life and stability must also be considered, and some have fast measurement speeds but low accuracy (such as Intel's RealSense, Obbec's Astra system, etc.). It is often expected that high-precision 3D face data can be obtained in applications in the field of face recognition to improve the 3D recognition rate.

[0004] However, while ensuring measurement accuracy, how to reduce the integrated volume, lower costs, achieve high-speed acquisition, and ultimately design a low-cost, miniaturized, high-speed, high-precision dynamic three-dimensional measurement instrument is still an important challenge in engineering implementation. Summary of the invention

[0005] In order to overcome the problems of high cost, large volume, low precision, etc. in the existing structured light three-dimensional measurement, the present invention provides a three-dimensional measuring instrument based on fiber coded structured light projection.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a three-dimensional measuring instrument based on optical fiber coded structured light projection, comprising:

[0008] A light source unit, for emitting light beams and controlling each light beam based on a timing sequence;

[0009] A structured light projection unit, used for transmitting the light beam through an optical fiber bundle, wherein one light beam corresponds to one optical fiber bundle, and all the optical fiber bundles are combined, and are encoded by longitudinally alternating arrangement at the combined end face, and the coded pattern is projected through a projection lens;

[0010] An acquisition unit, used for acquiring a surface image of the object after the coded pattern is projected on the surface of the object;

[0011] The processing unit is used to process and analyze the surface image, perform three-dimensional reconstruction on the object to be measured, and generate a three-dimensional digital entity.

[0012] According to a specific implementation, in the above three-dimensional measuring instrument, encoding is performed by longitudinally alternating arrangement on the beam-combining end surface, specifically including:

[0013] The beam combining end face is evenly divided into coupling end faces corresponding to the light beams, and the coupling end faces are respectively fixed into the coupling structure;

[0014] The fiber tails of each optical fiber bundle are arranged vertically into N columns, which are circulated in sequence until all optical fiber bundles are closely arranged in sequence to complete the encoding;

[0015] Wherein, N is a positive integer.

[0016] According to a specific implementation, in the above three-dimensional measuring instrument, the processing unit is used to process and analyze the surface image, specifically including:

[0017] The phase shift correction algorithm is used to output the truncated phase map and texture map, and feature point detection is performed;

[0018] A point cloud is generated according to the detected features, and then combined with the truncated phase map and the texture map to generate a three-dimensional digital entity of the object being measured.

[0019] According to a specific implementation, in the above three-dimensional measuring instrument, the processing unit is further used to denoise the surface image using an adaptive contrast enhancement algorithm.

[0020] According to a specific implementation, in the above three-dimensional measuring instrument, the acquisition unit uses left and right dual-channel synchronous cameras, which are respectively arranged on both sides of the projection lens.

[0021] According to a specific implementation, in the above three-dimensional measuring instrument, the processing unit is further used to use random unknown phase shift fringe phase solution to obtain the collected surface image by the collection unit, so that the object under test obtains the correct unfolding phase.

[0022] According to a specific implementation, in the above three-dimensional measuring instrument, the acquisition unit adopts a synchronous camera, which is arranged on the same plane as the projection lens.

[0023] According to a specific implementation, in the above three-dimensional measuring instrument, the light beams emitted by the light source unit include two beams or three beams; the coding pattern corresponds to the light beams, including a two-step phase shift pattern and a three-step phase shift pattern.

[0024] According to a specific embodiment, in the above three-dimensional measuring instrument, the instrument further includes a display unit for displaying the surface image and the three-dimensional digital entity

[0025] According to a specific implementation, in the above three-dimensional measuring instrument, in the structured light projection unit, the diameter of the beam combining end face matches the imaging range of the projection lens.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention adopts optical fiber illumination, and encodes the order of arrangement of optical fiber bundles to realize sinusoidal structured light pattern, so that the three-dimensional measuring instrument provided by the present invention can ensure that the projected coded pattern has a strict and accurate phase difference, and obtains an accurate phase shift pattern by timing control of the light source, so that the present invention has significant characteristics such as high speed, high precision and high reliability when performing three-dimensional measurement of the object to be measured, and can overcome the three-dimensional acquisition, measurement and identification of moving objects. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic diagram of a projection effect provided by an embodiment of the present invention;

[0029] Figure 2 A schematic diagram of the actual effect of projecting the object to be tested provided by an embodiment of the present invention;

[0030] Figure 3 A schematic diagram of a modulation pattern collected by a left-view camera provided in an embodiment of the present invention;

[0031] Figure 4 A schematic diagram of a modulation pattern collected by a right-view camera provided in an embodiment of the present invention;

[0032] Figure 5 A schematic diagram of a three-dimensional model established according to an embodiment of the present invention;

[0033] Figure 6 A schematic diagram of the structure of a three-dimensional measuring instrument based on fiber-coded structured light projection provided by an embodiment of the present invention;

[0034] Figure 7 A schematic diagram of the structure of an optical fiber bundle type arbitrarily movable casting and mining unit provided in an embodiment of the present invention;

[0035] Figure 8 A schematic diagram of the structure of a binocular stereoscopic vision projection and acquisition three-dimensional instrument unit based on an optical fiber bundle provided in an embodiment of the present invention;

[0036] Fig. 9 A schematic diagram of a light beam at the rear end of the beam combination provided by an embodiment of the present invention;

[0037] Fig.10 A schematic diagram of sinusoidal structured light provided by an embodiment of the present invention;

[0038] Fig.11 A schematic diagram of phase extraction and phase unwrapping provided by an embodiment of the present invention;

[0039] Fig.12 A schematic diagram of truncating a phase image and a texture image and performing feature point detection provided by an embodiment of the present invention;

[0040] Fig.13 A schematic diagram of generating a three-dimensional effect of an object to be measured provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below in conjunction with test examples and specific implementation methods. However, this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments, and all technologies realized based on the content of the present invention belong to the scope of the present invention.

[0042] This invention is a new technical exploration of structured light measurement, which can replace the expensive and complex structured light projection system of traditional optical machines. The present invention uses fiber optic coding to project multi-frame sinusoidal structured light with a fixed phase difference as the measurement medium. The inter-frame phase difference can be strictly and stably controlled by a clever coding method, and the integrated design of projection and sampling forms an arbitrary movable detection unit. It greatly expands the application scenarios of traditional three-dimensional measurement. It is suitable for small spaces, such as oral tooth measurement, endoscope system application, etc.

[0043] The present invention uses electronic switches to select corresponding projection channels in time-sharing order. It has simple control, fast switching speed, stable and reliable, no need for installation and adjustment, good maintainability and other good performances. Fiber optic projection replaces the traditional high-cost optical projector projection device, which greatly reduces the technical difficulty in control and significantly reduces the cost. The lighting system adopts a fiber optic system to improve the utilization rate of the light source, thereby improving the contrast of the projected stripes. The projection effect is projected by an actual prototype device, and after projection acquisition, edge analysis, phase unwrapping and calibration, as well as image processing and algorithm verification, it is shown that the present invention has a good effect and meets the design expectations.

[0044] Please refer to Figure 1 , which shows a schematic diagram of the projection effect provided by an embodiment of the present invention, and Figure 2 , which shows a schematic diagram of the actual effect of the projection of the object to be tested provided by an embodiment of the present invention.

[0045] The three-dimensional measuring instrument based on fiber coded structured light projection provided by the present invention is to obtain a high-precision three-dimensional measurement entity model. The independently designed phase shift encoding and adaptive calibration method used by the present invention, as well as the method for obtaining an accurate phase shift pattern, are the key technologies of the technical solution of the present invention.

[0046] The effect is verified by measuring and 3D reconstruction of the human face surface: the effect of the binocular stereoscopic vision projection 3D instrument unit based on the optical fiber bundle, please refer to Figure 3 , which shows a schematic diagram of a modulation pattern collected by a left-view camera provided in an embodiment of the present invention, please refer to Figure 4 , which shows a schematic diagram of the modulation pattern collected by the right-view camera provided by an embodiment of the present invention. Through multiple measurements and algorithm processing, the established three-dimensional model is as follows Figure 5 As shown, and compared with the high-precision 3D laser scanner.

[0047] The present invention adopts an integrated design of projection and acquisition, which increases the convenience of application and adaptability to multiple scenarios. The present invention can project multiple groups of sinusoidal structured light with fixed phase difference at high speed and perform measurements, while controlling the camera for synchronous acquisition, that is, by controlling the optical fiber coding to project stable structured light through illumination, and after modulation by the measured object, the image is collected for three-dimensional digital entity measurement.

[0048] In the existing 3D measurement and recognition systems, structured light 3D measurement has a very broad application prospect in public security, finance, transportation and other civil fields due to its non-contact, high recognition rate and high anti-counterfeiting performance. It is one of the important core technologies for building intelligent public service platforms, smart cities and safe cities. As we all know, the premise for the rapid development of structured light 3D measurement is to have highly integrated, high-speed and high-precision 3D projection acquisition equipment.

[0049] At present, the technology and application of high speed and high precision are still imperfect, and the measurement practicability of special scenes and special materials is not strong.

[0050] The existing high-precision 3D reconstruction methods are mainly based on structured light 3D measurement profilometry, which is based on the principles of active structured light and triangulation. The complex surface of the face is usually used as the detection object to evaluate its effect. Among them, the fringe projection profilometry (FPP) is considered to have the most development advantages and market prospects, which can be used to measure dynamic objects. There are two most commonly used schemes in FPP. One is Fourier transform profilometry (FTP), which is a representative single-frame scheme that only requires one frame of fringe to complete 3D reconstruction, which is very suitable for high-speed 3D measurement. However, due to the limitations of bandpass filtering and parameter selection, the measurement accuracy of this method is relatively low compared to multi-frame phase shift. The FTP method is more challenging to achieve automatic processing in complex dynamic scenes where the object shape changes over time. The other is phase shift profilometry (PSP). Compared with FTP, PSP is known for its higher accuracy, greater resolution, lower complexity and insensitivity to ambient light. Therefore, PSP is more suitable for the acquisition of high-speed and high-precision 3D face data.

[0051] On this basis, the most commonly used technical solutions are optical projection, that is, DLP projection components or LCOS projection devices, etc., which have complex systems and high costs.

[0052] However, while ensuring measurement accuracy, how to reduce the integrated volume, lower costs, achieve high-speed acquisition, and ultimately design a low-cost, miniaturized, high-speed, high-precision dynamic three-dimensional measurement instrument is still an important challenge in engineering implementation.

[0053] The following is a further introduction and description of a three-dimensional measuring instrument based on fiber coded structured light projection provided by the present invention in conjunction with specific implementations.

[0054] Please refer to Figure 6 , which shows a schematic structural diagram of a three-dimensional measuring instrument based on fiber coded structured light projection provided by an embodiment of the present invention, including:

[0055] A light source unit, for emitting light beams and controlling each light beam based on a timing sequence;

[0056] A structured light projection unit, used for transmitting the light beam through an optical fiber bundle, wherein one light beam corresponds to one optical fiber bundle, and all the optical fiber bundles are combined, and are encoded by longitudinally alternating arrangement at the combined end face, and the coded pattern is projected through a projection lens;

[0057] An acquisition unit, used for acquiring a surface image of the object after the coded pattern is projected on the surface of the object;

[0058] The processing unit is used to process and analyze the surface image, perform three-dimensional reconstruction on the object to be measured, and generate a three-dimensional digital entity.

[0059] The present invention uses optical fiber bundles as important components for structured light transmission and encoding for three-dimensional measurement, designs the overall architecture of an optical fiber structured light projection system for non-digital optical machines, uses an all-in-one optical fiber bundle to achieve pattern encoding, performs asynchronous illumination at each branch structure, and alternately arranges the items at the beam-combining end through each optical fiber bundle. When the light source is asynchronously turned on, the output end of the beam-combining end forms alternating light and dark areas, and then projects the pattern into the real three-dimensional measurement space through a projection lens. The present invention can project multiple groups of (sinusoidal) structured light with high contrast and low noise in a time-sharing manner for three-dimensional measurement and modeling applications.

[0060] The present invention is different from the traditional optical machine DMD projection device. It is a simple and easy-to-control spatial structure light projection unit. Its multi-frame sinusoidal structure light phase encoding and modulation are realized by using the arrangement and combination of optical fibers and the asynchronous drive of the light source. It does not rely on complex stripe projection control programs, and is also different from mechanical drag displacement optical fibers and pre-aligned phase projectors. It uses a projector without mechanical moving parts. The light source used can be an infrared light source, which can be used with an infrared camera for non-sensing measurement, or it can be used in the visible light band or blue light band for object measurement. It only needs to be used with the corresponding sensor and the corresponding band filter. The light source projection realizes the projection channel selection and phase shift mechanism through high-speed electronic switches, and cooperates with the camera for synchronous acquisition to realize the precise pattern encoding and projection functions that can only be completed by complex electronic optical systems such as projection optical machines. The production process does not require high-precision installation and adjustment, and large-scale batch production can be achieved at low cost, which can achieve considerable economic benefits.

[0061] In a possible implementation, the projection lens and the lens of the acquisition unit use the same parameters and models to eliminate the influence factors such as distortion that cause errors as much as possible. Specifically, the light source unit includes an LED light source, an aperture and a light source coupling system (collecting lens, etc.) and a structural linking component, which is used to project the optical fiber bundle in the structured light projection unit to form a combined optical fiber structure arranged according to the design.

[0062] Specifically, in one possible implementation, in the above three-dimensional measuring instrument, the acquisition unit uses a left and right dual-channel synchronous camera, which is respectively arranged on both sides of the projection lens. In another possible implementation, the acquisition unit uses a synchronous camera, which is arranged on the same plane as the projection lens.

[0063] Based on the three-dimensional measuring instrument provided by the present invention, the embodiment of the present invention can develop two design frameworks according to the application scenario requirements:

[0064] 1) Fiber-optic bundle type movable three-dimensional measurement instrument unit for small spaces or micro targets;

[0065] 2) A binocular stereo vision projection and acquisition three-dimensional instrument unit based on an optical fiber bundle for a three-dimensional object in free space (the face surface is used as a test example in the embodiment of the present invention).

[0066] In a possible implementation, a light source unit projects a three-in-one light beam as an example. Figure 7 , which shows a schematic diagram of the structure of the optical fiber bundle type arbitrarily movable projection and sampling unit provided by an embodiment of the present invention. The unit design is a three-dimensional measuring instrument based on structured light projection of three-in-one optical fiber coding. The design is theoretically calculated and experimentally verified. The design adopts three-in-one (three-step phase shift) coding, but is not limited to three-in-one (three-in-one-out). The same theory can be extended to multi-in-one, corresponding to multi-step phase shift coding. The present invention does not require complex control, and only needs to alternately turn on and off the light source corresponding to each channel and control the camera synchronization signal collection. No complex projection optical machine is required to generate patterns. Considering the decrease in the sinusoidality of the pattern formed by the entire bright and dark stripes caused by the small gap in the arrangement of the optical fiber beam, the embodiment of the present invention needs to arrange the optical fibers in each column tightly. At the same time, the projection lens will smooth the small defocus according to the projection effect, and the bright and dark boundary edge position will be denoised after image acquisition in the later stage. In one possible implementation, after the system is connected, the distance between the projection lens and the beam-combining end face can be fine-tuned according to the sinusoidal effect. The design itself has the property of being adjustable and adaptable in order to better solve the sinusoidal nature of the projection to improve the measurement effect and accuracy.

[0067] Please refer to Figure 8 , which shows a schematic structural diagram of a binocular stereoscopic vision projection and acquisition three-dimensional instrument unit based on optical fiber bundles provided in an embodiment of the present invention.

[0068] Furthermore, in a possible implementation, the embodiment of the present invention takes three-in-one fiber coding as an example to specifically explain how to implement coding between multiple frames of sinusoidal fringes and their projection control and camera synchronous acquisition.

[0069] Specifically, the three-in-one (all-in-one) optical fiber structure coding design is as follows:

[0070] Combination Figure 8 Among them, LED1, LED2, and LED3 are used as light sources, and LED1, LED2, and LED3 are controlled to be coupled sequentially into the corresponding incident end faces of the optical fiber bundle. When the three-in-one (multi-in-one) optical fiber is manufactured, the manufacturing process is arranged and coded so that each branch is arranged alternately in a sequence on the beam-combining end face. That is, each time the light sources are turned on in sequence, the items on the beam-combining end face form a sinusoidal fringe image with alternating light and dark and sequential transversely. With the synchronous acquisition of the camera, three frames (multiple frames) of standard phase-shifted fringes can be formed, which can be used for phase unwrapping and three-dimensional reconstruction.

[0071] Please refer to Fig. 9 , which shows a schematic diagram of the beam of the combined end face provided by an embodiment of the present invention; because there are multiple groups of alternating arrangements, the algorithm requirement of sinusoidality is considered, that is, the entire end face needs to form a sinusoidal pattern with evenly alternating light and dark when each light source is turned on. The embodiment of the present invention considers using an optical fiber with a suitable numerical aperture to solve this problem, as shown in the specific example. Fig.10 As shown: vertical exit end face, vertical column arrangement axis direction observation, the three-way branch on the exit end face column arrangement as shown Fig.10 Taking channel 2 as an example, when light source 2 is on, all columns with the order of 2 are lit. According to the selection of appropriate optical fiber numerical aperture, a certain emission angle will be generated at the exit fiber tail. Specifically, it is calculated by a=arcsin (NA), which will form an effect that the width of the bright and dark areas is nearly equal. At this time, the columns with the order of 1 and 3 are both dark areas, and a continuous sinusoidal structured light pattern can be formed on the column items.

[0072] According to the requirements of the multi-frame sinusoidal structured light algorithm, multiple frames of sinusoidal stripes are required to satisfy an equally spaced phase shift relationship. Therefore, the light source is driven to switch on and off in sequence, and the synchronous camera is controlled to perform acquisition processing, phase unwrapping and reconstruction to form three-dimensional point cloud data.

[0073] Coding of fiber bundles for fiber structured light three-dimensional instrument and its engineering implementation method:

[0074] Usually, the diameter of single-mode optical fiber for optical communication applications is 4~10μm. Mature products on the market are selected and combined with the needs of designing sinusoidal patterns. It is preferred to use 5μm single-mode optical fiber bundles as the basic material, and multimode optical fiber can also be used. Considering the short transmission distance, the transmission loss can be ignored, and the length can be customized according to the application. After calculation, the diameter and number of the total optical fiber bundle are determined according to the imaging range of the rear end face of the projection lens. The rear end of the optical fiber bundle is divided into three bundles corresponding to the coupling end face of the light source, and each is fixed in the coupling structure. Then take the fiber tail in the LED1 path and arrange it longitudinally into N columns. After calculation and balance with the empirical value, take N=3 (fixed tooling, wavy groove fixture against the surface). Then take the fiber tail in the LED2 path and arrange it longitudinally into N columns, and then take the fiber tail in the LED3 path and arrange it longitudinally into N columns, and cycle in sequence until all the optical fiber bundles are closely arranged in sequence to complete the coding production.

[0075] It is understandable that the total diameter and number of fiber bundles are determined according to the imaging range of the rear end face of the projection lens, including the total number of fibers determined according to the applicable target surface parameters of the rear end of the projection lens, that is, the maximum target surface D compatible with the lens / fiber diameter d=total number of fibers n. According to the three-in-one, that is, the output fiber end, the number of fiber coupling ends divided into each light source during the fiber manufacturing process should be n / 3, that is, the light source beam and coupling lens for light source coupling are designed according to this size.

[0076] Similarly, the above three-in-one light beam processing can be applied to two-in-one, that is, the light source unit emits two light beams, which will not be repeated here.

[0077] In the embodiment of the present invention, three-channel optical fiber encoding with fixed phase is mainly used to perform spatial projection of time-sharing sinusoidal structured light, and the sinusoidal fringe pattern modulated by the target is synchronously collected by a camera. The specific steps are as follows:

[0078] 1) The integrated fiber optic projection acquisition device should face the object to be measured. Only by controlling the lighting sources in the three channels to switch on and off in sequence and controlling the camera to capture synchronously can three modulated patterns be obtained.

[0079] 2) Each time a frame is projected, the left and right cameras capture images synchronously to form multiple spatial modulation patterns with a certain phase shift for the left view L0, L1, L2 and the right view R0, R1, R2.

[0080] 3) After the calibrated optical system architecture is used to sample the object to be measured, the collected images are processed and analyzed, and spatial calculations of the three-dimensional images are performed.

[0081] 4) Generate point cloud, corresponding texture stitching, etc. to form reconstruction information of three-dimensional digital entity in space.

[0082] Specifically, in the image processing part (using projected face acquisition as a test verification scenario):

[0083] 1) Phase extraction and phase unwrapping, please refer to Fig.11 .

[0084] Specifically, M (M ≥ 3) fringe images can be used to complete 3D reconstruction. The algorithm uses facial feature points as prior knowledge, uses a phase adjustment algorithm to determine the precise phase order difference K, adjusts the relative phase to the same phase reference through a phase adjustment relationship of 2Kπ, and then performs sub-pixel stereo matching to ultimately achieve high-precision 3D face reconstruction.

[0085] 2) The phase shift correction algorithm outputs the truncated phase map and texture map and performs feature point detection. Please refer to Fig.12 .

[0086] Specifically, the corresponding phase matching pair is found in the truncated phase according to the detected (face) feature points. The (face) feature point coordinates are extracted from the texture image pair ( x L,i , y L,i )and( x R,i , y R,i ), the phase corresponding to the truncated phase is Φ L ( xL,i ,y L,i ) and Φ R ( x R,i ,y R,i ), i is the number of feature points. Each detected feature point has its own inherent properties, and the feature points at the corresponding positions of (left and right faces) can be considered as a set of feature point pairs. Since the acquired modulated image has been level-corrected, the phase pairs corresponding to the coordinates of the (face) feature point pairs on the truncated phase can be considered as a set of phase matching pairs. The phase matching pairs corresponding to the feature point pairs (Φ L ( x L,i ,y L,i ) and Φ R ( x R,i , y R,i )) and divide it by 2π to get the corresponding stripe order difference of each group of (face) feature points K i ( x , y ).

[0087] (1)

[0088] Through voting strategies K i ( x , y ) based on which the final fringe order difference is obtained K The phase adjustment algorithm is used to adjust the relative phase of the left camera as a reference. According to formulas (2) and (3), the absolute phase of the right camera is added with 2. K After π, the left and right relative phases are adjusted to the same phase reference, and then sub-pixel phase matching is performed to finally obtain high-precision three-dimensional (face) data.

[0089] (2)

[0090] (3)

[0091] 3) To generate a 3D effect, please refer to Fig.13 .

[0092] The present invention optimizes the optical fiber coupling optical system of the light source, adopts the design of the object side telecentric optical path, the collimating lens and the aperture can adjust the lighting angle, improves the light energy utilization rate and lighting uniformity of the lighting system, improves the contrast of the projected fringes, and uses the lens to project the image of the optical fiber lighting onto the surface of the object. The present invention is an innovative design with independent research and development design, and is a new research based on relevant technical theories to solve the factors of technical limitations such as foreign DLP. The integrated structure of optical fiber casting and sampling used in the present invention can arbitrarily move the optical fiber coding casting and sampling structure, which is also a new design mode, which increases the flexibility of the three-dimensional measuring instrument and broadens the application scenarios, and is suitable for small spaces, such as oral tooth measurement, endoscope system application, etc. The present invention fully ensures that there is a strict and accurate phase difference between the projected fringes through clever optical fiber arrangement and encoding methods, and electronic switching meets high-speed measurement. At the same time, there is no motion mechanism, thereby increasing the reliability of measurement. The present invention uses the independently designed phase shift encoding and adaptive calibration method, and the method of obtaining an accurate phase shift pattern is one of the key technologies of the technical solution of the present invention. The invention has been rigorously tested and verified, which shows that the invention has superior performance. Compared with the traditional stripe structured light measurement, it has significant features such as high speed, high precision and high reliability. After testing, its three-frame projection-acquisition time is less than 10ms, which can overcome the three-dimensional acquisition measurement and recognition of moving objects. After multiple measurements, the three-dimensional accuracy is close to 0.1mm, which is better than similar measurement products.

[0093] Furthermore, the present invention obtains the correct unfolding phase through phase solution of random unknown phase shift fringes. This algorithm not only solves the problem that the relative phase obtained by the stereo camera through the spatial phase unfolding algorithm cannot be directly used for stereo matching due to different phase references; and only three phase shift modes are required, so that the method has low sensitivity to dynamic scenes and can be applied to dynamic (face) measurement. The optical fiber output end has a certain divergence angle and defocus adjustment to increase sinusoidality and further improve the accuracy of three-dimensional modeling. This is verified by the three-frame phase shift device preferred in this article. This method is not limited by complex algorithms such as projection frequency and measurement depth range.

[0094] Furthermore, the present invention uses adaptive contrast enhancement ACE for denoising, and the algorithm uses unsharp mask technology: first, the image is divided into two parts. One is the low-frequency unsharp mask part, which can be obtained by low-pass filtering (smoothing, blurring technology) of the image. The other is the high-frequency component, which can be obtained by subtracting the unsharp mask from the original image. Then the high-frequency part is amplified (the set of amplification factors is the contrast gain CG) and added to the unsharp mask, and finally an enhanced image is obtained. The strategy of restoring the original signal as much as possible and removing coarse noise points.

[0095] It can be understood that the processing unit provided in the embodiment of the present invention can be composed of high-performance artificial intelligence computing and processing devices such as a central processing unit (CPU), a graphics processing unit (GPU), and a field programmable gate array (FPGA) to realize image processing functions.

[0096] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A three-dimensional measuring instrument based on fiber coded structured light projection, characterized in that: The instrument comprises: A light source unit, for emitting light beams and controlling each light beam based on a timing sequence; A structured light projection unit, used for transmitting the light beam through an optical fiber bundle, wherein one light beam corresponds to one optical fiber bundle, and all the optical fiber bundles are combined, and are encoded by longitudinally alternating arrangement at the combined end face, and the coded pattern is projected through a projection lens; An acquisition unit, used for acquiring a surface image of the object after the coded pattern is projected on the surface of the object; A processing unit, used for processing and analyzing the surface image, performing three-dimensional reconstruction on the object to be measured, and generating a three-dimensional digital entity; Among them, the longitudinal alternating arrangement is used for encoding at the beam combining end face, specifically including: The beam combining end face is evenly divided into coupling end faces corresponding to the light beams, and the coupling end faces are respectively fixed into the coupling structure; The fiber tails of each optical fiber bundle are arranged longitudinally into N columns, which are circulated in sequence until all optical fiber bundles are closely arranged in sequence to complete the encoding; Wherein, N is a positive integer.

2. A three-dimensional measuring instrument based on fiber coded structured light projection according to claim 1, characterized in that: The processing unit is used to process and analyze the surface image, specifically including: The phase shift correction algorithm is used to output the truncated phase map and texture map, and feature point detection is performed; A point cloud is generated according to the detected features, and then combined with the truncated phase map and the texture map to generate a three-dimensional digital entity of the object being measured.

3. A three-dimensional measuring instrument based on fiber coded structured light projection according to claim 1, characterized in that: The processing unit is further configured to denoise the surface image using an adaptive contrast enhancement algorithm.

4. A three-dimensional measuring instrument based on fiber coded structured light projection according to claim 1, characterized in that: The acquisition unit adopts a left and right dual-channel synchronous camera, which is respectively arranged on both sides of the projection lens.

5. A three-dimensional measuring instrument based on fiber coded structured light projection according to claim 4, characterized in that: The processing unit is also used to use random unknown phase shift fringes to solve the surface image acquired by the acquisition unit, so that the object under test obtains a correct unfolding phase.

6. A three-dimensional measuring instrument based on fiber coded structured light projection according to claim 1, characterized in that: The acquisition unit adopts a synchronous camera and is arranged on the same plane as the projection lens.

7. The three-dimensional measuring instrument based on fiber coded structured light projection according to claim 1, characterized in that: The light beams emitted by the light source unit include two beams or three beams; the coding pattern corresponds to the light beams, including a two-step phase shift pattern and a three-step phase shift pattern.

8. The three-dimensional measuring instrument based on fiber coded structured light projection according to claim 1, characterized in that: The apparatus further comprises a display unit for displaying the surface image and the three-dimensional digital entity.

9. The three-dimensional measuring instrument based on fiber coded structured light projection according to claim 1, characterized in that: In the structured light projection unit, the diameter of the beam combining end surface matches the imaging range of the projection lens.

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