Three-dimensional line spectrum confocal sensing method and device

Abstract

The present invention provides a three-dimensional line-spectral confocal sensing method and device, comprising: a light source module, a dispersive lens module, a beam splitter, an intensity detection module, a filtering module, and a spectrum detection module. The light source module utilizes dual light source input, with a single light source exhibiting high spectral uniformity within the corresponding wavelength range, thereby increasing the spectral range and improving spectral consistency. The dispersive lens module performs dispersion modulation on the illumination light of the two wavelength bands. The superposition of the two wavelength bands enables a larger axial detection range. The intensity detection module utilizes a slit and a detector to effectively record the energy distribution at the focal point of the object, obtaining a corresponding full-intensity map, enabling more accurate lateral two-dimensional measurement. The spectrum detection module utilizes a dual-spectral demodulation detection system, corresponding to the wavelength range of the dual light sources, to obtain a corresponding spectral distribution map, improving spectral resolution and axial resolution. Combining the full-intensity map from intensity detection with the spectral map from spectrum detection, line scanning is used to achieve three-dimensional measurement with higher lateral and axial resolution. Therefore, the three-dimensional line-spectral confocal sensing method and device proposed by the present invention, while building on the advantages of rapid line scanning detection, can achieve a larger axial detection range, higher lateral resolution, and higher axial resolution for three-dimensional measurement.

Description

Technical Field

[0001] The present invention relates to a precision measurement method and device, in particular to a method and device for performing three-dimensional measurement of an object surface based on spectral confocal line scanning. Background Art

[0002] With the rapid development of modern manufacturing and the rapid advancement of precision manufacturing capabilities, the demand for high-precision sensors is also increasing. Three-dimensional surface measurement methods are generally divided into traditional contact measurement and non-contact measurement. Although contact measurement has high measurement accuracy, it often scratches the surface and easily affects the device itself. For flexible materials, contact measurement can cause material deformation, resulting in inaccurate measurement results. Therefore, due to the adverse effects of contact measurement, non-contact measurement is generally adopted.

[0003] A spectral confocal sensor uses the dispersion-focusing properties of wavelength to measure and spectral demodulation to establish a relationship between wavelength and surface height. A polychromatic light source is focused at different depths according to wavelength through a dispersive lens system, forming a series of axially distributed focal points. The beam at the focal point on the object's surface is reflected with maximum energy. The spectral demodulation system then determines the wavelength at which the beam reaches its maximum intensity, thereby establishing a relationship between wavelength and surface height. Due to its high accuracy and speed, spectral confocal sensors have become an important tool for non-contact detection.

[0004] Spectral confocal sensors offer both point scanning and line scanning modes. Point scanning spectral confocal sensors offer high lateral resolution but slow scanning speeds, making them unsuitable for rapid detection. Line scanning confocal sensors, with their faster scanning speeds, are now more widely used. Line scanning confocal sensors use slits or cylindrical lenses to generate linear illumination, allowing for a larger detection range with a single detection, but also suffer from lower resolution. The spectral uniformity of the light source, two-dimensional lateral scanning detection, and the spectral demodulation system are all key factors affecting 3D measurement resolution. Summary of the Invention

[0005] In view of this, the present invention provides a three-dimensional line spectrum confocal sensing method and device for solving the problem of low measurement resolution of line scanning spectrum confocal sensors.

[0006] The present invention provides a three-dimensional line spectrum confocal sensing device, comprising: a light source module, a dispersion lens module, a beam splitter, an intensity detection module, a filtering module, and a spectrum detection module;

[0007] The light source module comprises two wide-band light sources with high spectral uniformity and a Y-shaped optical fiber, the light sources are connected via the output end of the Y-shaped optical fiber, and the output end generates linear illumination light;

[0008] The dispersive lens module includes: an achromatic collimator, a beam splitter and a focusing lens. The achromatic collimator collimates the linear illumination light within the full spectrum to generate a parallel light field. After passing through the focusing lens, the focus distribution at different depth positions is obtained. The beam splitter is used to split the light reflected by the object into a subsequent detection system.

[0009] The beam splitter is used to split the light reflected by the object into different detection systems, one part for intensity detection and the other part for spectral demodulation detection;

[0010] The intensity detection module includes: a focusing mirror, a slit, and a detector. The focusing mirror is used to focus the light reflected by the object to the slit. The slit is used to filter out-of-focus light. The detector is used to receive the light beam after passing through the slit to obtain a full intensity map.

[0011] The filtering module includes: a focusing mirror, a slit and a collimating mirror. The focusing mirror is used to focus the light reflected by the object to the slit. The slit is used to filter out-of-focus light. The collimating mirror is used to collimate the light after passing through the slit and enter the subsequent spectral demodulation system.

[0012] The spectrum detection module includes: a dichroic mirror and a dual-spectrum demodulation detection system. The dichroic mirror is used to separate the light beams in the wavelength ranges λ1 to λ2 and λ2 to λ3 corresponding to the dual light sources and transmit them to the corresponding spectral spectrometer. The spectral spectrometer is used to split the light beams in the wavelength ranges λ1 to λ2 and λ2 to λ3. Two detectors are respectively used to receive the light field distribution after the corresponding spectral splitting. Different pixels correspond to different wavelengths to obtain the corresponding spectrum diagram.

[0013] Combining the full intensity image obtained by the intensity detection module and the spectrum image obtained by the spectrum detection module, the three-dimensional information of the object can be obtained more accurately through line scanning;

[0014] In some embodiments, the light source in the light source module of the three-dimensional line spectrum confocal sensing device can be an LED or a white light laser, and the wavelength ranges of the light source are λ1~λ2 and λ2~λ3 respectively, and have a highly consistent intensity distribution within the corresponding wavelength ranges.

[0015] In some embodiments, the dispersion lens in the dispersion lens module of the three-dimensional line spectrum confocal sensing device can use a lens group to achieve axial dispersion focusing, or can use an aspheric lens to achieve axial dispersion focusing. At the same time, the aspheric lens can reduce the number of lenses and simplify the optical structure.

[0016] In some embodiments, the detector in the intensity detection module of the three-dimensional line spectrum confocal sensing device can be a COMS, CCD or photomultiplier tube array, which is used to record the intensity of the light field after passing through the slit and obtain a full-intensity image.

[0017] In some embodiments, the spectral detection module of the three-dimensional line spectrum confocal sensing device includes two spectral demodulation systems corresponding to the λ1~λ2 and λ2~λ3 band ranges respectively. The spectral spectrometer used can be a linear gradient filter, a grating and a prism. After passing through the spectral spectrometer, light beams of different wavelengths are received by different pixels of the detector. The detector can be CMOS and CCD.

[0018] In addition, the present invention also discloses a three-dimensional line spectrum confocal sensing method for achieving three-dimensional measurement of an object, which is characterized by comprising:

[0019] Step 1: Use a light source module to generate linear illumination light with high spectral consistency, with wavelengths ranging from λ1 to λ2 and λ2 to λ3 respectively;

[0020] Step 2: axially disperse the linear beam using a dispersive lens module, so that beams of different wavelengths are focused at different depths;

[0021] Step 3: Use a beam splitter to split the light reflected by the object into different detection systems, one part for intensity detection and the other for spectral demodulation detection;

[0022] Step 4: The intensity detection system is used to obtain a signal that has not been spectrally demodulated, and records the intensity image of the light beam reflected from the object;

[0023] Step 5, using a filtering module to obtain a light beam having a wavelength corresponding to the focal point on the surface of the object being measured after passing through the slit;

[0024] Step 6: Use the spectrum demodulation detection module to obtain the light beam passing through the filter module, perform spectral decomposition on it, record the distribution of different wavelengths, and obtain the corresponding spectrum diagram;

[0025] Step 7: Using the obtained intensity map and spectrum map, the surface of the object is scanned by line scanning to obtain more accurate three-dimensional data of the object's morphology.

[0026] Compared with the prior art, the embodiments of the present invention have the following advantages:

[0027] The present invention proposes a three-dimensional line spectrum confocal sensing method and device that uses two light sources of different wavelength bands coupled through a Y-type optical fiber to provide linear light illumination. The two light sources have high spectral uniformity in the corresponding wavelength band range, which increases the axial detection range, and adopts a corresponding dual-spectral demodulation system to obtain higher axial resolution. The dual-spectral demodulation system obtains corresponding spectral images by performing wavelength splitting on the light beam reflected from the object and entering different spectral demodulation detection systems, making full use of the capabilities of the spectral splitting device and the pixels of the detector to improve the axial resolution. The intensity detection system is used without spectral demodulation, and a two-dimensional lateral intensity image is obtained, and the lateral resolution will be correspondingly higher. Combining the spectral map obtained by the dual-spectral demodulation detection system and the full-intensity image obtained by the intensity detection system, the three-dimensional information of the object with higher resolution is reconstructed through line scanning. The three-dimensional line spectrum confocal sensing method and device proposed in the present invention adopts two light sources of different wavelength bands for illumination on the basis of online scanning high-speed measurement, providing linear light with high spectral uniformity. The corresponding spectrum image is obtained by the dual-spectral demodulation detection system and combined with the full-intensity image obtained by the intensity detection system, realizing three-dimensional measurement of objects with a larger detection range, higher axial resolution, and higher lateral resolution. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 1 is a schematic structural diagram of a three-dimensional line spectrum confocal sensing device according to an embodiment of the present invention;

[0029] Figure 2 Schematic diagram of light dispersion in a dispersion lens module according to an embodiment of the present invention;

[0030] Figure 3 is a schematic diagram of intensity recording in an intensity detection module in an embodiment of the present invention;

[0031] FIG4( a ) is a schematic diagram of spectral splitting using a linear gradient filter in an embodiment of the present invention;

[0032] FIG4( b ) is a schematic diagram of spectral splitting using a prism in an embodiment of the present invention;

[0033] FIG4( c ) is a schematic diagram of using a grating for spectral splitting in an embodiment of the present invention. DETAILED DESCRIPTION

[0034] Combine Figure 1 As shown, the specific structure of a three-dimensional line spectrum confocal sensing device of the present invention includes: a light source module 10, a dispersion lens module 20, a beam splitter 30, an intensity detection module 40, a filtering module 50, and a spectrum demodulation module 60.

[0035] The light source module 10 includes two light sources 11 with a wavelength range of λ1 to λ2 and a light source 12 with a wavelength range of λ2 to λ3, both of which have high spectral uniformity, and a Y-type optical fiber 13. The input end of the Y-type optical fiber 13 connects the light source 11 and the light source 12, and the output end generates linear illumination light.

[0036] The dispersive lens module 20 includes: an achromatic collimator 21, a beam splitter 22, and a focusing lens 23. The achromatic collimator 21 collimates the linear illumination light within the full spectrum to generate a parallel light field. After passing through the focusing lens 23, the focus distribution at different depth positions is obtained. The beam splitter 22 is used to split the light reflected by the object into a subsequent detection system.

[0037] The beam splitter 30 is used to split the light reflected by the object into different detection systems, one part is used for intensity detection, and the other part is used for spectral demodulation detection system;

[0038] The intensity detection module 40 includes: a focusing mirror 41, a slit 42 and a detector 43. The focusing mirror 41 is used to focus the light reflected by the object to the slit 42. The slit 42 is used to filter out-of-focus light. The detector 43 is used to receive the light beam after passing through the slit to obtain a full intensity image.

[0039] The filtering module 50 includes a focusing mirror 51, a slit 52, and a collimating mirror 53. The focusing mirror 51 is used to focus the light reflected by the object to the slit 52. The slit 52 is used to filter out-of-focus light. The collimating mirror 53 is used to collimate the light after passing through the slit and enter the subsequent spectral demodulation system.

[0040] The spectral detection module 60 includes: a dichroic mirror 61, a spectral spectrometer 62, a detector 63, a spectral spectrometer 64, and a detector 65. The dichroic mirror 61 is used to separate the wavelength ranges λ1 to λ2 and λ2 to λ3 corresponding to the dual light sources to the corresponding spectral spectrometers respectively. The spectral spectrometer 62 is used to split the light beams in the wavelength ranges λ1 to λ2. The detector 63 is used to receive the light field distribution after spectral spectrometry, and different pixels correspond to different wavelengths to obtain the corresponding spectrum. The spectral spectrometer 64 is used to split the light beams in the wavelength ranges λ1 to λ2. The detector 65 is used to receive the light field distribution after spectral spectrometry, and different pixels correspond to different wavelengths to obtain the corresponding spectrum.

[0041] By combining the full intensity image obtained by the intensity detection module and the spectrum image obtained by the spectrum detection module, the three-dimensional information of the object can be obtained more accurately through line scanning.

[0042] The three-dimensional line-spectral confocal sensing method and device uses two light sources with different wavelength ranges as input. These ranges, such as 400nm-550nm and 550nm-700nm, respectively, exhibit high spectral uniformity, facilitating subsequent spectral demodulation and increasing the spectral range. A dispersive lens axially disperses the two wavelength ranges separately. For example, the corresponding dispersion ranges for the 400nm-550nm and 550nm-700nm bands are both 0.6mm, and the combined total dispersion range is 1.2mm. The corresponding spectral detection module achieves higher resolution. For example, if a detector with 1500 lateral pixels is used, the spectral range corresponding to a single pixel in a single wavelength range is 0.1nm. In comparison, using a single spectral demodulation system, under the same spectral range and detector conditions, the spectral range corresponding to a single pixel is 0.2nm. Acquiring a full-intensity image fully utilizes the detector pixels, allowing line scanning to capture a complete surface image of the object. Furthermore, combined with the spectral map obtained by the spectral detection system, it provides depth information, enabling complete three-dimensional measurement.

[0043] Combine Figure 2 As shown, the dispersive lens module 20 of the three-dimensional line spectrum confocal sensing device includes a dispersive lens 23 for generating axial dispersion. Light beams of different wavelengths are focused at different depths. Combined with the wavelength ranges λ1-λ2 and λ2-λ3 of the light source module 10, a larger axial dispersion range is achieved. The dispersive lens 23 can be a combination of multiple lenses or an aspherical lens.

[0044] Combine Figure 3 As shown, intensity detection module 40 includes a focusing lens 41, a slit 42, and a detector 43. The light beam reflected from the object passes through focusing lens 41 and slit 42 before entering detector 43. Detector 43, which can be a CMOS, CCD, or linear array detector, records the energy distribution along the slit to obtain a full intensity map. Through line scanning, complete two-dimensional information about the object's surface can be obtained. Acquiring a full intensity map facilitates constructing a higher-resolution two-dimensional image of the object.

[0045] As shown in Figure 4, the spectral spectrometer 62 includes various forms, including (a) linear gradient filter for spectral spectrometry, (b) prism dispersion for spectral spectrometry, and (c) grating dispersion for spectral spectrometry. (a) A linear gradient filter is used for spectral splitting to obtain light field distributions of different wavelengths, which has the advantage of a simple device. (b) A prism 621 is used for spectral splitting, and then the light of different wavelengths is focused on different pixels of the detector through a focusing lens 622. (c) A grating 621 is used for spectral splitting, and then the light of different wavelengths is focused on different pixels of the detector through a reflective focusing lens 622. After passing through the spectral spectrometer, the light intensities of different wavelengths are recorded by different pixels to obtain corresponding spectral graphs.

[0046] This embodiment further provides a three-dimensional line spectrum confocal sensing method, which includes the following steps:

[0047] Step 1: Use a light source module to generate linear illumination light with high spectral consistency, with wavelengths ranging from λ1 to λ2 and λ2 to λ3 respectively;

[0048] Step 2: axially disperse the linear beam using a dispersive lens module, so that beams of different wavelengths are focused at different depths;

[0049] Step 3: Use a beam splitter to split the light reflected by the object into different detection systems, one part for intensity detection and the other for spectral demodulation detection;

[0050] Step 4: The intensity detection system is used to obtain a signal that has not been spectrally demodulated, and records the intensity image of the light beam reflected from the object;

[0051] Step 5, using a filtering module to obtain a light beam having a wavelength corresponding to the focal point on the surface of the object being measured after passing through the slit;

[0052] Step 6: Use the spectrum demodulation detection module to obtain the light beam passing through the filtering module, perform spectral decomposition on it, record the distribution of different wavelengths, and obtain the corresponding spectrum diagram.

[0053] Step 7: Using the obtained intensity map and spectrum map, the surface of the object is scanned by line scanning to obtain more accurate three-dimensional data of the object's morphology.

[0054] Compared with the prior art, the embodiments of the present invention have the following advantages:

[0055] 1. Two light sources with high spectral consistency are used for band illumination, which increases the axial detection range.

[0056] 2. Combined with the dual-spectrum demodulation system, corresponding to dual-band illumination, dual-band detection is achieved to obtain higher axial resolution.

[0057] 3. Combining intensity detection and spectral detection, and adopting line scanning, it can achieve more accurate three-dimensional measurement of object shape based on high-speed detection.

[0058] The above description is only an example of a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A three-dimensional line spectrum confocal sensing device, characterized in that: include: Light source module, dispersion lens module, beam splitter, intensity detection module, filter module, spectrum detection module; The light source module is used to generate linear lighting light with high spectral uniformity and a wide spectral range; The dispersion lens module is used to axially disperse the linear illumination light so that light of different wavelengths is focused at different depths; The beam splitter is used to split the reflected light from the object in proportion and send it to different detection systems; The intensity detection module is used to receive light reflected from the object and record the full intensity image after passing through the focal plane slit; The filtering module is used to filter the light reflected from the object so that the light in the wavelength range of the focus position can enter the subsequent spectrum detection system; The spectrum detection module is used to receive the light beam after passing through the filtering module, and through spectrum demodulation, record the intensity distribution of different wavelengths to obtain the corresponding spectrum diagram; The light source module includes: two light sources with different wavelengths, the wavelength ranges being λ1 to λ2 and λ2 to λ3 respectively. The light sources can be LEDs or white light lasers. The illumination light output by the two light sources has a certain wavelength range and a highly consistent intensity distribution within this wavelength range. The light source module further includes: a Y-shaped optical fiber, the input end of the Y-shaped optical fiber is connected to the light source, and the output end is coupled together to generate linear light illumination; The intensity detection module includes: a focusing mirror, a slit and a detector. The focusing mirror is used to focus the light reflected by the object to the slit. The slit is used to filter out-of-focus light. The detector is used to receive the light beam after passing through the slit to obtain a full intensity map.

2. A three-dimensional line spectrum confocal sensing device according to claim 1, characterized in that: The dispersive lens module includes: an achromatic collimator, a beam splitter and a focusing lens. The achromatic collimator collimates the linear illumination light within the full spectrum to generate a parallel light field. After passing through the focusing lens, the focus distribution at different depth positions is obtained. The beam splitter is used to split the light reflected by the object to a subsequent detection system.

3. A three-dimensional line spectrum confocal sensing device according to claim 2, characterized in that: The dispersion lens group also includes: the focusing lens can be an aspherical focusing lens, which can obtain a larger focus distribution range in the depth direction and can control the aberration within a smaller range.

4. A three-dimensional line spectrum confocal sensing device according to claim 1, characterized in that: The beam splitter is generally a semi-transparent and semi-reflective mirror, which is used to separate the light reflected from the object, one of which enters the intensity detection module and the other enters the filter.

5. A three-dimensional line spectrum confocal sensing device according to claim 1, characterized in that: The filtering module includes: a focusing mirror, a slit and a collimating mirror. The focusing mirror is used to focus the light reflected by the object to the slit, the slit is used to filter out-of-focus light, and the collimating mirror is used to collimate the light after passing through the slit and enter the subsequent spectral demodulation system.

6. A three-dimensional line spectrum confocal sensing device according to claim 1, characterized in that: The spectrum detection module includes: a dichroic mirror and a dual-spectrum demodulation detection system. The dichroic mirror is used to separate the light beams in the wavelength ranges λ1 to λ2 and λ2 to λ3 corresponding to the dual light sources and transmit them to the corresponding spectral spectrometer. The spectral spectrometer is used to split the light beams in the wavelength ranges λ1 to λ2 and λ2 to λ3. The two detectors are respectively used to receive the light field distribution after the corresponding spectral splitting. Different pixels correspond to different wavelengths to obtain the corresponding spectrum diagram.

7. A method for three-dimensional measurement of an object using the device according to claim 1, characterized in that: The following steps are involved: Step 1: Use a light source module to generate linear illumination light with high spectral consistency, with wavelengths ranging from λ1 to λ2 and λ2 to λ3 respectively; Step 2: axially disperse the linear beam using a dispersive lens module, so that beams of different wavelengths are focused at different depths; Step 3: Use a beam splitter to split the light reflected by the object into different detection systems, one part for intensity detection and the other for spectral demodulation detection; Step 4: The intensity detection system is used to obtain a signal that has not been spectrally demodulated, and records the intensity image of the light beam reflected from the object; Step 5, using a filtering module to obtain a light beam having a wavelength corresponding to the focal point on the surface of the object being measured after passing through the slit; Step 6: Use the spectrum demodulation detection module to obtain the light beam passing through the filter module, perform spectral decomposition on it, record the distribution of different wavelengths, and obtain the corresponding spectrum diagram; Step 7: Using the obtained intensity map and spectrum map, the surface of the object is scanned by line scanning to obtain more accurate three-dimensional data of the object's morphology.

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