CN215114433U - Structured light three-dimensional shape measuring device based on optical phase element - Google Patents

Abstract

The utility model relates to a structured light three-dimensional shape measuring device based on an optical phase element, wherein a projection module, a carrying platform and a camera module form a structured light measuring triangular light path, the optical subsystem optical axis of the projection module and the optical subsystem optical axis of the camera module are intersected on the carrying platform, and the projection module and the camera module are focused on the carrying platform; the optical phase element is positioned on an emergent light path of the projection module; the computer module is respectively connected with the projection module and the camera module, the projection module projects the fringe pattern input by the computer to the surface of the element to be measured through the optical phase element, the fringe pattern is collected by the camera module after being reflected by the optical phase element, and the fringe pattern is input into the computer module through the data transmission control line. The measuring device effectively modulates the binaryzation or sine stripes for projection by using the optical phase element, greatly extends the projection imaging depth of field of the system on the basis of ensuring the sine consistency of an axial projection light field, and is particularly suitable for structured light dynamic and even transient three-dimensional measurement based on the projection of the binaryzation stripes.

Description

Structured light three-dimensional shape measuring device based on optical phase element

Technical Field

The utility model relates to a three-dimensional appearance's measurement technique, in particular to structured light three-dimensional appearance measuring device based on optics phase component belongs to advanced optical detection technical field.

Background

In many fields of the present society, such as reverse engineering, automatic online detection, quality control, machine vision, medical diagnosis, etc., it is often necessary to perform rapid and accurate measurement on the three-dimensional topography of a diffuse reflection surface object. The traditional and direct detection tool is a three-coordinate machine, however, the contact working mode of the detection tool has the risk of scratching a detected piece, the whole testing process is long, and especially for an object to be detected with a large size, the detection efficiency is not high. In contrast, optical methods are increasingly favored because of their rapid, non-contact advantages. The laser interferometer can realize surface detection with nanometer level precision, but is only suitable for objects with simple surface change, has small axial dynamic measurement range and higher requirement on test environment, and is not easy to realize online detection. Although the scanning white light interferometer can detect objects with discontinuous surfaces, the lateral and longitudinal measurable ranges are limited, and the system is sensitive to external vibration.

The fringe projection profilometry is a typical structured light 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 many cases, the early projection fringes are formed by laser interference, sinusoidal grating projection imaging, or the like. With the rapid development of electronic devices, especially projectors based on Liquid Crystal Display (LCD), Liquid Crystal on Silicon (LCoS), and Digital Micromirror Device (DMD) technologies, the synthesis and control of measuring stripes become more convenient. The introduction of the sine stripe phase recovery technology further improves the morphology recovery precision and the resolution. In the measurement process of fringe projection profilometry, the fast projection display of high-fidelity sine fringes is one of the targets pursued by people, and is particularly significant to some high-speed motion/transient test scenes. Compared to the other two technologies, the DMD has a significant advantage in refresh rate and thus becomes a preferred projection scheme for high/fast structured light three-dimensional measurement. Structured light projectors based on DMD generally produce sinusoidal fringes in two ways: binary Pulse Width Modulation (PWM), binary fringe defocus projection. The former is to decompose one gray scale sine stripe image which is pre-projected into N Bit images based on the PWM principle, and the sine stripe is formed by integrating N Bit images in a projection-imaging period time, wherein N is the Bit depth of the gray scale sine stripe image; the latter is to form a sinusoidal fringe by a binary fringe pattern or by using a low-pass filtering effect caused by the defocusing of the projection lens by means of a perturbation modulation (DM) technique. However, limited by the limited depth of field of the projection imaging lens, the contrast of the sine stripe is reduced along with the increase of the defocusing amount, and the high-precision acquisition of the axial large-range three-dimensional shape 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 display and acquisition of high-fidelity sine stripes within a large axial depth of field range without significantly increasing the volume and complexity of the system is becoming one of research hotspots and trends in the field of structured light three-dimensional measurement based on stripe projection.

Disclosure of Invention

The utility model discloses to prior art exist not enough, under the condition that does not show increase system volume and complexity remarkably, can effectively modulate binaryzation or sinusoidal stripe, provide one kind and realize the fast projection of high fidelity sinusoidal stripe at the big axial depth of field within range and show, acquire and solve the three-dimensional appearance measuring device of structured light.

In order to achieve the above object, the present invention provides a structured light three-dimensional shape measuring device based on an optical phase element, which comprises a projection module, an optical phase element, a loading platform, a camera module, a data transmission control line and a computer module; the projection module, the reference plane and the camera module form a structured light measuring triangular light path, an optical subsystem optical axis of the projection module and an optical subsystem optical axis of the camera module are intersected on the carrying platform, and the projection module and the camera module are focused on the carrying platform; the optical phase element is positioned on an emergent light path of the projection module, and a divergent light field emitted by the projection module uniformly covers the optical phase element; the computer module is respectively connected with the projection module and the camera module through a data transmission control line, the projection module projects the stripe pattern input by the computer to the surface of the element to be measured on the loading platform through the optical phase element, the stripe pattern is collected by the camera module after being reflected by the surface of the element to be measured, and the stripe pattern is input into the computer module through the data transmission control line.

The optical phase element of the technical proposal of the utility model comprises one of an odd-symmetric phase plate, a multilayer diffraction optical element, a refraction-diffraction mixed micro-optical element and a super lens element; the projection module comprises one of a spatial light modulator or a grating based projector.

The utility model provides a three-dimensional appearance measuring device, when measuring operating condition, the computer module passes through data transmission control line transmission to projection module with the coding parameter of binaryzation or sinusoidal stripe, generate corresponding stripe pattern, form standard sinusoidal light field pattern in the depth of field scope of axial continuation after phase coding component modulation again, project the component surface that awaits measuring that is located cargo platform, the camera module gathers the phase coding deformation stripe pattern by the component surface reflection that awaits measuring, input computer module, obtain the three-dimensional appearance distribution on component surface that awaits measuring through data processing.

Compared with the prior art, the utility model discloses a show the advantage and lie in: under the condition that the volume and the complexity of the system are not remarkably increased, the provided measuring device adopts an optical phase element to effectively modulate binary or sine stripes, greatly extends the projection imaging depth of field of the system on the basis of ensuring the sine consistency of an axial projection light field, and is particularly suitable for structured light dynamic and transient three-dimensional measurement based on binary stripe projection.

Drawings

Fig. 1 is a schematic structural diagram of a structured light three-dimensional topography measuring apparatus based on an optical phase element according to an embodiment of the present invention.

Wherein: 1. a projection module; 2. an optical phase element; 3. an original to be tested; 4. a carrier platform; 5. a camera module; 6. a data transmission control line; 7. a computer module.

Fig. 2 is the defocused projection of the existing fringe and the embodiment of the present invention provides a contrast of the sinusoidal deformation fringe pattern obtained by the structured light three-dimensional topography measuring device based on the optical phase element. Wherein: (a) the existing fringe defocusing projection effect; (b) an embodiment of the utility model provides a measuring device effect is provided.

Fig. 3 is a schematic diagram of the image data acquisition and processing flow of the structured light three-dimensional topography measuring method based on the optical phase element according to the 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 embodiments.

Example 1

Referring to fig. 1, it is a schematic structural diagram of a structured light three-dimensional topography measuring apparatus based on an optical phase element according to this embodiment. The measuring device consists of a projection module 1, an optical phase element 2, a carrying platform 4, a camera module 5, a data transmission control line 6 and a computer module 7. A classical structured light measurement triangular light path is formed among the projection module 1, the object carrying platform 4 and the camera module 5, and an optical subsystem optical axis of the projection module 1 and an optical subsystem optical axis of the camera module 5 are intersected at the object carrying platform 4; the optical phase element 2 is positioned on an emergent light path of the projection module 1 and is just uniformly covered by a divergent light field emitted by the projection module 1; the projection module 1 and the camera module 5 are both focused on the loading platform 4, and the size of a projected light Field of the projection module 1 on the loading platform 4 through the optical phase element 2 is matched with the size of a Field of view (FOV) of the camera module 5 on the loading platform 4; the computer module 7 is respectively connected with the projection module 1 and the camera module 5 through a data transmission control line 6, coding parameters of binaryzation or sine stripes are transmitted to the projection module 1 through the data transmission control line 6, the projection module 1 generates corresponding stripe patterns according to the coding parameters, standard sine light field patterns are formed in an axially extended depth of field range after being modulated by the optical phase element 2 and are projected to the surface of the element to be measured 3 on the carrying platform 4, phase coding deformation stripe patterns reflected by the surface of the element to be measured 3 are collected by the camera module 5 and are transmitted back to the computer module 7, and finally three-dimensional shape distribution of the surface of the element to be measured 3 is obtained through data processing.

In the measurement apparatus provided in this embodiment, the optical phase element may be one of an odd-symmetric phase plate, a multilayer diffraction optical element, a refraction-diffraction hybrid micro-optical element, and a superlens element; in the present embodiment, an odd-symmetric type phase plate is employed.

The projection module can be selected from one of a spatial light modulator or a grating-based projector; in an embodiment of the present invention, a projector based on a spatial light modulator is used.

Referring to fig. 2, (a) is a sinusoidal deformation fringe image obtained by defocusing projection of the conventional fringe, (b) is a sinusoidal deformation fringe image obtained by the measuring device provided in this embodiment, and the measured object is an object with five steps. Obviously through the contrast, under the condition that does not show increase system volume and complexity remarkably, the utility model discloses an original projection stripe has been modulated effectively in optics phase component's use, on the basis of guaranteeing axial projection light field sine uniformity, has greatly extended the projection imaging depth of field of system.

The embodiment provides a structured light three-dimensional topography measurement method based on an optical phase element by using the device shown in fig. 1, wherein the image data acquisition and processing flow is shown in fig. 3, and the method comprises the following steps:

(1) assembling and adjusting a measuring device: the projection module 1 and the camera module 5 are respectively connected with a computer module 7 through a data transmission control line 6, and the optical axis of the optical subsystem of the projection module 1 and the optical axis of the optical subsystem of the camera module 5 are adjusted to be intersected with the loading platform 4, so that a classical structured light measurement triangular light path is formed; the optical phase element 2 is arranged on an emergent light path of the projection module 1, so that a divergent light field just emitted by the projection module 1 is uniformly covered; adjusting the projection module 1 and the camera module 5 to focus on the loading platform 4, wherein the size of the projected light Field of the projection module 1 on the loading platform 4 through the optical phase element 2 is matched with the size of the Field of view (FOV) of the camera module 5 on the loading platform 4; the device under test 3 is placed on the stage 4 in the central area of the common FOV of the projection module 1 and the camera module 5.

(2) Projection and acquisition of fringe pattern: based on the structured light stripe trigonometry measurement principle, calibrating to obtain a phase-height conversion relation function of the measurement device; calibrating a Point Spread Function (PSF) of the measuring device by using a star Point method; a computer module 7 sets coding parameters of binaryzation or sine stripes by using matched developed Graphical User Interface (GUI) software based on Python, and transmits the coding parameters to a projection module 1 through a data transmission control line 6; then the projection module 1 generates corresponding stripe patterns for measurement according to the coding parameters, forms standard sinusoidal light field patterns in the axially extended depth of field range after being modulated by the optical phase element 2 and projects the standard sinusoidal light field patterns on the surface of the element 3 to be measured, and phase coding deformed stripe patterns reflected by the surface of the element 3 to be measured are collected by the camera module 5 and transmitted back to the computer module 7.

(3) Demodulation and surface shape reconstruction of the fringe pattern: combining the PSF calibrated in the step (2), processing the obtained phase coding deformation stripe pattern by adopting a phase coding stripe phase demodulation algorithm, and calculating to obtain a corresponding wrapping phase; obtaining Phase distribution related to the three-dimensional shape of the element to be detected 3 by using a Phase unwrapting technology; and (3) reconstructing the three-dimensional shape distribution of the surface of the element to be measured 3 from the phase distribution according to the phase-height conversion relation function of the measuring device obtained by pre-calibration in the step (2).

In the phase encoding fringe phase demodulation algorithm in step (3) of this embodiment, a convolution removing algorithm is first used in combination with the measurement device PSF calibrated in step (2) to obtain a sinusoidal deformation fringe pattern with enhanced contrast and sinusoid, and then a corresponding wrapped phase distribution is obtained by processing with a wrapped phase demodulation algorithm.

The deconvolution algorithm in the phase coding fringe phase demodulation algorithm adopted in the step (3) is one of a deconvolution algorithm based on mathematical model filtering (such as Wiener filtering, Richardson-Lucy filtering, Alternating Direction Multiplier Method (ADMM) and the like), a deconvolution algorithm based on deep learning neural network, and a deconvolution algorithm based on a mixture of the mathematical model filtering and the deep learning neural network. In the embodiment of the present invention, the deconvolution algorithm based on the alternative direction multiplier method ADMM is adopted.

The wrapped phase demodulation algorithm in the phase coding stripe phase demodulation algorithm in the step (3) adopts one of wrapped phase space domain demodulation, wrapped phase time domain demodulation and wrapped phase space-time domain hybrid demodulation algorithms; the embodiment of the utility model provides an in, adopt parcel phase place time domain demodulation algorithm.

The Phase Unwrapping technique in the step (3) is one of Spatial Phase Unwrapping (SPU), Temporal Phase Unwrapping (TPU) and Spatial-Temporal hybrid Phase Unwrapping techniques; the embodiment of the utility model provides an in, adopt time domain phase place expansion algorithm.

Claims (3)

1. A structured light three-dimensional shape measuring device based on an optical phase element is characterized in that: the system comprises a projection module, an optical phase element, a loading platform, a camera module, a data transmission control line and a computer module; the projection module, the reference plane and the camera module form a structured light measuring triangular light path, an optical subsystem optical axis of the projection module and an optical subsystem optical axis of the camera module are intersected on the carrying platform, and the projection module and the camera module are focused on the carrying platform; the optical phase element is positioned on an emergent light path of the projection module, and a divergent light field emitted by the projection module uniformly covers the optical phase element; the computer module is respectively connected with the projection module and the camera module through a data transmission control line, the projection module projects the stripe pattern input by the computer to the surface of the element to be measured on the loading platform through the optical phase element, the stripe pattern is collected by the camera module after being reflected by the surface of the element to be measured, and the stripe pattern is input into the computer module through the data transmission control line.

2. The apparatus according to claim 1, wherein the apparatus comprises: the optical phase element comprises one of an odd-symmetric phase plate, a multilayer diffraction optical element, a refraction-diffraction mixed micro-optical element and a super-lens element.

3. The apparatus according to claim 1, wherein the apparatus comprises: the projection module comprises one of a spatial light modulator or a grating based projector.

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