CN215338216U - Fringe projection three-dimensional shape measuring device based on diffractive optical element - Google Patents
Fringe projection three-dimensional shape measuring device based on diffractive optical element Download PDFInfo
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Abstract
The utility model relates to a fringe projection three-dimensional shape measuring device based on a diffractive optical element, which comprises a projection module, an object carrying platform, a camera, a data transmission control interface and a computer, wherein the object carrying platform is arranged on the projection module; the projection module utilizes three red, green and blue LED light sources, generates three-frequency sine three-step phase shift fringe light field patterns in a time-sharing manner under the control of a computer, projects the three-frequency sine three-step phase shift fringe light field patterns on the surface of an object to be measured positioned on the carrying platform, is collected by a camera after being reflected by the surface of the object to be measured, is input into the computer through a data transmission control interface, and obtains the three-dimensional shape distribution of the surface of the object to be measured through data processing. Under the conditions that devices such as silicon-based liquid crystal and the like are not used and the system volume and complexity are not remarkably increased, a diffraction optical element is used for modulating an incident light field, and a three-frequency sine three-step phase shift fringe light field pattern is formed through time-sharing rapid projection; meanwhile, on the basis of ensuring the sine consistency of the axial projection fringe light field patterns, the projection imaging depth of field of the measuring system is greatly extended.
Description
Technical Field
The utility model relates to a three-dimensional shape measurement technology, in particular to a fringe projection three-dimensional shape measurement device based on a diffraction coding phase plate, and belongs to the technical field of advanced optical detection.
Background
In many fields of current social production, such as reverse engineering, automatic on-line detection, machine vision, etc., it is often necessary to perform fast and accurate three-dimensional measurement on diffuse reflection surface objects. Optical methods are becoming popular because of their advantages such as non-contact, fast overall field, and high measurement accuracy. The fringe projection profilometry, as a typical optical three-dimensional measurement technology, has the advantages of simple system structure, no strict requirement on the external environment, large measurement dynamic range, high precision, high speed and the like, and is often applied to the detection of the three-dimensional appearance of the diffuse reflection surface object. The measuring system is generally composed of a projector, a camera and a computer; in the measurement process, the fast projection, display and acquisition of high-fidelity sine stripes are one of the targets pursued by people, and especially have great significance for some high-speed motion/transient test scenes. The early measuring fringes are mostly generated in modes of laser interference, sinusoidal grating projection imaging and the like, and the problems of inconvenient regulation and control of relevant parameters of single frames and phase shift fringes and the like exist. With the rapid development of optoelectronic devices, especially projectors based on Liquid Crystal on Silicon (LCoS) and Digital Micromirror Device (DMD) technologies, the synthesis and control of stripes for measurement become more convenient, but the quality of projected sinusoidal stripes is still susceptible to the optoelectronic performance of the projectors. In the existing fringe projection profilometry measuring process, in order to achieve the purpose of high-precision detection, a projector based on an LCoS or a DMD is usually used for projecting sine phase shift fringes, but the sine/phase shift fidelity of a monochrome/color phase shift fringe is easily influenced by the Gamma effect/color crosstalk phenomenon of electronic equipment, the high-performance LCoS or the DMD is expensive and is easily clamped by foreign suppliers, and the projected fringes often have the phenomenon of multiple reflections (namely multipath interference) on the surface of a measured object. In addition, in the existing fringe projection profilometry, the limited depth of field of a projection imaging lens is limited, and the contrast of the sine fringe is reduced along with the increase of the defocusing amount, so that the high-precision acquisition of the axial large-range three-dimensional topography is influenced. Although the corresponding projection imaging lens can be designed based on Scheimpflug law (Scheimpflug Principle) to extend the depth of field, problems such as lens assembly and additional phase distortion correction caused by oblique projection imaging exist, and the depth of field extension range is still limited. Although the projection imaging lens designed based on the double telecentric optical path can avoid the problem of oblique projection imaging, the projection imaging magnification is fixed, and the measurement field of view and the caliber/volume of the lens are mutually restricted. Therefore, how to realize fast projection and acquisition of high-fidelity sine phase-shift fringes within a large axial depth of field without using devices such as LCoS or DMD and without significantly increasing the system volume and complexity has become one of the hot points and trends of research in the fringe projection profilometry field.
Disclosure of Invention
Aiming at the defects in the prior art, the utility model provides a fringe projection three-dimensional shape measuring device which can realize the rapid projection, acquisition and resolving of high-fidelity sine phase shift fringes within a large axial depth of field range under the condition of not depending on devices such as silicon-based liquid crystal on (LCoS) or Digital Micromirror Device (DMD) and the like and not obviously increasing the system volume and complexity.
In order to achieve the above object, the utility model provides a fringe projection three-dimensional shape measuring device based on a diffractive optical element, which comprises a projection module, an object carrying platform, a camera, a data transmission control interface and a computer; the projection module comprises an illumination light source subsystem, a coupling relay optical subsystem and a diffraction optical element; the illumination light source subsystem comprises an illumination light source interface circuit module and three red, green and blue three-color LED light sources, namely a red, green and blue three-color LED light source I, a red, green and blue three-color LED light source II and a red, green and blue three-color LED light source III, wherein the red, green and blue three-color LED light source I is positioned at the object space focal point of the coupling relay optical subsystem, the red, green and blue three-color LED light source II and the red, green and blue three-color LED light source III are symmetrically positioned on the object space focal plane of the coupling relay optical subsystem at two sides of the red, green and blue three-color LED light source I, and the diffractive optical element is positioned at the image space exit pupil of the coupling relay optical subsystem; the projection module, the carrying platform and the camera form a fringe projection measurement triangular light path, an optical axis of a coupling relay optical subsystem of the projection module and an optical axis of a camera lens are intersected on the carrying platform, and a diffraction optical element of the projection module and the camera lens are focused on the carrying platform; and the computer is respectively connected with the projection module and the camera through a data transmission control interface.
The utility model provides a fringe projection three-dimensional morphology measuring device based on a diffractive optical element, wherein a red, green and blue LED light source is a light source formed by combining three chips of a red LED, a green LED and a blue LED respectively, or a light source formed by a single LED chip emitting red, green and blue light.
When the three-dimensional shape measuring device based on the fringe projection of the diffractive optical element is in a measuring working state, the projection module is controlled by the computer to generate three-frequency sine three-step phase shift fringe light field patterns in a time-sharing mode, the three-frequency sine three-step phase shift fringe light field patterns are projected onto the surface of an object to be measured on the carrying platform, the three-dimensional shape patterns are collected by the camera after being reflected by the surface of the object to be measured, the three-dimensional shape patterns are input into the computer through the data transmission control interface, and the three-dimensional shape distribution of the surface of the object to be measured is obtained through data processing.
The working principle of the measuring device provided by the utility model is as follows: the projection module receives a computer instruction and rapidly lights the red, green and blue LED light sources I, II and III in sequence in a time-sharing manner, so that emergent light fields of the single-color LEDs output in a time-sharing manner are uniformly and parallelly irradiated to the diffraction optical element through the coupling relay optical subsystem; the diffraction optical element comprises three subregions I, II and III, monochromatic uniform parallel LED lights which are emitted by red, green and blue LED light sources I, II and III and pass through the coupling relay optical subsystem are respectively and correspondingly modulated, three-frequency sine three-step phase shift fringe light field patterns with the frequencies of R, G and B are sequentially formed in the range of the axially extended depth of field after the modulation of the diffraction optical element, the three-frequency sine three-step phase shift fringe light field patterns are projected to the same region on the surface of the object to be measured in a time-sharing mode, the three-frequency sine three-step phase shift deformation fringe patterns reflected by the surface of the object to be measured are sequentially collected in a time-sharing mode by the camera and transmitted to the computer, and the three-dimensional shape distribution of the surface of the object to be measured is obtained through data processing.
Compared with the prior art, the utility model has the remarkable advantages that: the provided measuring device uses a diffraction optical element to modulate an incident light field without the help of devices such as silicon-based liquid crystal on silicon (LCoS) or a digital micromirror element (DMD) and the like and without obviously increasing the volume and the complexity of a system, and forms a three-frequency sine three-step phase shift fringe light field pattern by time-sharing rapid projection; meanwhile, on the basis of ensuring the sine consistency of the axial projection fringe light field patterns, the projection imaging depth of field of the measuring system is greatly extended.
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FIG. 1 is a schematic structural diagram of a fringe projection three-dimensional topography measuring apparatus based on a diffraction-encoded phase plate according to an embodiment of the present invention;
wherein: 1. a projection module; 2. an object to be tested; 3. a carrier platform; 4. a camera; 5. a data transmission control line; 6. a computer; 11. an illumination light source interface circuit module; 121. a red, green and blue three-color LED light source I; 122. a red, green and blue three-color LED light source II; 123. a red, green and blue three-color LED light source III; 13. a coupling relay optical subsystem; 14. a diffractive optical element; 141. a diffractive optical element subregion I; 142. a diffractive optical element subregion II; 143. a diffractive optical element subregion III.
Fig. 2 is a schematic workflow diagram of fringe projection three-dimensional topography measurement based on a diffraction-encoded phase plate for measurement according to an embodiment of the present invention.
Fig. 3 is a schematic flowchart of a fringe projection three-dimensional topography measurement based on a diffraction-encoded phase plate, which uses an absolute phase recovery algorithm based on a deep neural network during measurement according to an embodiment of the present invention.
Detailed Description
The technical solution of the present invention will be further described in detail with reference to the accompanying drawings and examples.
Example 1
Referring to fig. 1, it is a schematic structural diagram of a fringe projection three-dimensional topography measuring apparatus based on a diffraction-encoded phase plate according to this embodiment. The measuring device consists of a projection module 1, an object platform 3, a camera 4, a data transmission control line 5 and a computer 6; the projection module 1 consists of an illumination light source subsystem, a coupling relay optical subsystem 13 and a diffraction optical element 14; the illumination light source subsystem consists of an illumination light source interface circuit module 11, a red-green-blue three-color LED light source I121, a red-green-blue three-color LED light source II 122 and a red-green-blue three-color LED light source III 123; a red, green and blue three-color LED light source I in the illumination light source subsystem is positioned at the object focus of the coupling relay optical subsystem 13, a red, green and blue three-color LED light source II and a red, green and blue three-color LED light source III are symmetrically positioned on the object focus plane of the coupling relay optical subsystem 13 at two sides of the red, green and blue three-color LED light source I, and the diffractive optical element 14 is positioned at the image exit pupil position of the coupling relay optical subsystem; the projection module, the carrying platform and the camera form a fringe projection measurement triangular light path, an optical axis of a coupling relay optical subsystem of the projection module and an optical axis of a camera lens are intersected on the carrying platform, and a diffraction optical element of the projection module and the camera lens are focused on the carrying platform; the computer 6 is connected with the projection module 1 and the camera 4 through a data transmission control line 5 respectively, the projection module generates a three-frequency sine three-step phase shift stripe light field pattern according to computer instructions in a time sharing mode, projects the three-frequency sine three-step phase shift stripe light field pattern on the surface of the object to be measured 2 on the carrying platform, is collected by the camera after being reflected by the surface of the object to be measured, and is input into the computer through the data transmission control line.
When the measuring device provided by this embodiment is in a working state, the projection module 1 sequentially and rapidly lights the red, green and blue three-color LED light sources i 121, ii 122 and iii 123 according to the instruction of the computer 6, so that the emergent light fields of the individual color LEDs lighted in a time-sharing manner are respectively uniformly and parallelly irradiated to the corresponding sub-areas i 141, ii 142 and iii 143 on the diffractive optical element 14 through the coupling relay optical subsystem 13; after being modulated by the diffractive optical element 14, three-frequency sine three-step phase shift fringe light field patterns with the frequencies of R, G and B are sequentially formed in the axially extended depth of field range and are projected to the same area on the surface of the object 2 to be measured in a time-sharing manner, the camera 4 sequentially collects three-frequency sine three-step phase shift deformation fringe patterns reflected by the surface of the object 2 to be measured in a time-sharing manner and transmits the three-frequency sine three-step phase shift deformation fringe patterns to the computer 6, and three-dimensional shape distribution of the surface of the object 2 to be measured is obtained through data processing.
In the measuring apparatus provided in this embodiment, the diffractive optical element during measurement includes three sub-regions i 141, ii 142, and iii 143, which respectively modulate the monochromatic uniform parallel LED lights emitted by the red, green, and blue LED light sources i 121, ii 122, and iii 123 passing through the coupling relay optical subsystem 13, sequentially form the phase shift fringe light field patterns i, ii, and iii of the red, green, and blue colors within the axially extended depth of field, that is, correspondingly modulate to generate three-frequency sinusoidal three-step phase shift fringe light field patterns with frequencies of R, G and B, and project the three-frequency sinusoidal three-step phase shift fringe light field patterns onto the same region on the surface of the object 2 to be measured.
In the measuring device provided by this embodiment, the red, green and blue LED light source may be a light source composed of three chips, namely, a red LED, a green LED and a blue LED, or a light source composed of a single LED chip capable of emitting three colors of red, green and blue; in this embodiment, a light source is used which is formed by a single LED chip capable of emitting three colors of red, green, and blue, respectively.
In this embodiment, the coupling relay optical subsystem 13 is a single optical lens.
The flow of the fringe projection three-dimensional topography measuring method based on the diffraction-encoded phase plate adopted by the embodiment is shown in fig. 2 by using the device shown in fig. 1, and the method comprises the following steps:
The projection module and the camera are respectively connected with a computer through a data transmission control line, and the optical axis of the coupling relay optical subsystem of the projection module and the optical axis of the camera lens are adjusted to intersect with the loading platform to form a fringe projection measurement triangular optical path; and adjusting the diffractive optical element of the projection module and the camera lens to focus on the carrying platform, wherein the projection area of the projection module on the carrying platform through the diffractive optical element is matched with the size of the field area of the camera on the carrying platform.
And 102, calibrating the device and training a deep neural network model.
Deriving to obtain a system imaging measurement model based on fringe projection profilometry and a diffraction optical phase coding technical principle; based on a system imaging measurement model, using a three-dimensional object with known height distribution to calibrate and obtain a phase-height conversion relation function of the measuring device; based on a system imaging measurement model, in combination with a phase-height conversion relation calibration result of a measurement device, a series of known three-dimensional distributed virtual model objects are used for simulating and generating three-frequency sine three-step phase shift deformation fringe graphs with the frequencies of R, G and B respectively, and a model driving method is adopted for training a deep neural network-based multipath interference separator R, G and a deep neural network-based multipath interference separator B respectively.
And step 103, projecting and collecting the fringe pattern.
Placing an object to be measured in a central area of a common view field of a projection module and a camera on an object carrying platform; a lighting source Interface circuit module in a projection module is controlled by using matched developed Graphical User Interface (GUI) software on a computer through a data transmission control line, red, green and blue LED light sources I, II and III are rapidly lightened in sequence, and emergent light fields of the monochromatic LEDs lightened in a time-sharing manner are uniformly and parallelly irradiated to corresponding sub-areas I, II and III on the diffraction optical element through a coupling relay optical subsystem; after being modulated by the diffractive optical element, three-frequency sine three-step phase shift fringe light field patterns with the frequencies of R, G and B are sequentially formed in the range of the axially extended depth of field, the three-frequency sine three-step phase shift fringe light field patterns are projected to the same area on the surface of the object to be measured in a time-sharing mode, the three-frequency sine three-step phase shift deformation fringe patterns reflected by the surface of the object to be measured are sequentially collected in a time-sharing mode by the camera, and the three-frequency sine three-step phase shift deformation fringe patterns are transmitted to the computer through the data transmission control line.
And 104, reconstructing a stripe diagram phase and a three-dimensional surface shape.
Processing the obtained three-frequency sine three-step phase shift deformation fringe pattern by using an absolute phase recovery algorithm based on a deep neural network, and calculating to obtain absolute phase distribution related to the three-dimensional morphology of the object to be detected; and reconstructing to obtain the three-dimensional topography distribution of the surface of the object to be measured according to the phase-height conversion relation function of the measuring device obtained by pre-calibration in the step 102.
In the absolute phase recovery algorithm based on the deep neural network in step 104 of this embodiment, the process is shown in fig. 3, three multipath interference separators trained in step 102 based on the deep neural network are used to process the three-step sinusoidal phase-shift deformation fringe pattern of the three frequencies obtained in step 103, respectively, to separate a three-step sinusoidal phase-shift deformation fringe pattern of the three frequencies directly diffusely reflected by the surface of the object to be measured, which does not contain multipath interference, and then a three-step random phase-shift algorithm is used to calculate the wrapping phase of each frequency on the basis of suppressing the phase-shift error, and finally a multi-frequency heterodyne phase expansion algorithm is used to obtain the absolute phase distribution.
In this embodiment, the frequency of the tri-frequency sinusoidal three-step phase shift fringe light field pattern in steps 102 and 103 is optimized and selected according to the chinese remainder theorem, so that the number of fringes of the camera in the field area on the objective platform after the three-time optical heterodyne operation is 1; in the embodiment, the number of the full-field stripes in the measurement area is selected to be 70, 64 and 59; the three-frequency sine three-step phase shift fringe light field pattern is three-step phase shift with equal step length, and the phase shift amount of each step is
。
Claims (2)
1. A fringe projection three-dimensional shape measuring device based on a diffraction optical element is characterized in that: the system comprises a projection module, an object carrying platform, a camera, a data transmission control interface and a computer;
the projection module comprises an illumination light source subsystem, a coupling relay optical subsystem and a diffraction optical element; the illumination light source subsystem comprises an illumination light source interface circuit module and three red, green and blue three-color LED light sources, namely a red, green and blue three-color LED light source I, a red, green and blue three-color LED light source II and a red, green and blue three-color LED light source III, wherein the red, green and blue three-color LED light source I is positioned at the object space focal point of the coupling relay optical subsystem, the red, green and blue three-color LED light source II and the red, green and blue three-color LED light source III are symmetrically positioned on the object space focal plane of the coupling relay optical subsystem at two sides of the red, green and blue three-color LED light source I, and the diffractive optical element is positioned at the image space exit pupil of the coupling relay optical subsystem;
the projection module, the carrying platform and the camera form a fringe projection measurement triangular light path, an optical axis of a coupling relay optical subsystem of the projection module and an optical axis of a camera lens are intersected on the carrying platform, and a diffraction optical element of the projection module and the camera lens are focused on the carrying platform;
and the computer is respectively connected with the projection module and the camera through a data transmission control interface.
2. The fringe projection three-dimensional topography measuring device based on the diffractive optical element as claimed in claim 1, wherein: the red, green and blue LED light source is a light source formed by combining three chips of a red LED, a green LED and a blue LED respectively, or a light source formed by emitting a single LED chip of three colors of red, green and blue.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115187649A (en) * | 2022-09-15 | 2022-10-14 | 中国科学技术大学 | Three-dimensional measurement method, system, equipment and storage medium for resisting strong ambient light interference |
| CN116105632A (en) * | 2023-04-12 | 2023-05-12 | 四川大学 | Self-supervision phase unwrapping method and device for structured light three-dimensional imaging |
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2021
- 2021-07-14 CN CN202121601151.4U patent/CN215338216U/en active Active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115187649A (en) * | 2022-09-15 | 2022-10-14 | 中国科学技术大学 | Three-dimensional measurement method, system, equipment and storage medium for resisting strong ambient light interference |
| CN116105632A (en) * | 2023-04-12 | 2023-05-12 | 四川大学 | Self-supervision phase unwrapping method and device for structured light three-dimensional imaging |
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