Optical sensor

Abstract

The present disclosure relates to optical sensors. The invention relates to the field of optical sensors for metrology and / or color or multispectral measurement of surfaces and objects. A multi-band measurement light is projected into a measurement plane such that the measurement light of different wavelengths or combinations of wavelengths is focused at each point within the measurement plane along a first axis extending longitudinally from the sensor. The spectral content of the measurement light reflected from the surface of the measurement object is used to determine a displacement or profile of the measurement object.

Description

Technical Field

[0001] This invention relates to the field of optical sensors, particularly sensors for measuring the displacement, two-dimensional profile, or three-dimensional shape of a measured object and / or for measuring the color or multispectral properties of the surface of the measured object. Background Technology

[0002] Optical sensors used to measure the displacement, 2D profile, or 3D shape of an object project measurement light onto the object and measure certain characteristics of the measurement light reflected from the surface of the object in order to determine the displacement, 2D profile, or 3D shape of the object.

[0003] Many such sensors degrade in performance on different types of surfaces that reflect less measurement light back to the sensor, for example, due to low reflectivity or high orientation.

[0004] Some higher-accuracy sensors project a series of spatially distinct points onto the surface of the object being measured, rather than a continuous line, to improve accuracy, because the separation of measurement light reflected from adjacent points on the line can be imperfect. However, this arrangement reduces the resolution of measurements along the nominal measurement line due to the reduced sampling of the object's surface through a series of distinct points compared to a continuous line.

[0005] Furthermore, combinations of displacement information, 2D contour information, or 3D shape information with spectral reflectance information are often required for comprehensive quality inspection in industrial manufacturing processes. However, conventional displacement, 2D, and / or 3D sensors cannot provide simultaneous spectral reflectance measurements of the surface of the object being measured, and conventional multispectral or hyperspectral imaging systems alone cannot obtain displacement, 2D contour, or 3D shape information.

[0006] These and other objectives will be better understood by referring to this application in its entirety. Not all objectives need to be satisfied by all embodiments of the invention described below or by the invention as defined in each of the claims. As those skilled in the art will understand, other technical problems or objectives besides those identified above can be solved by combinations of features listed in the claims. Summary of the Invention

[0007] This invention relates to an optical sensor for measuring the displacement or profile of a measurement object relative to a sensor.

[0008] The optical sensor includes a light source configured to emit multicolor measurement light, the multicolor measurement light comprising multiple wavelength bands. The sensor also includes a first aperture array arranged to receive the measurement light from the light source.

[0009] The sensor's first dispersive optical element is arranged to receive measurement light passing through the first aperture array and to disperse the received measurement light along a first axis on a first diffraction or scattering surface. Different wavelengths of multiple bands are dispersed from different apertures of the first aperture array onto a first region of the first diffraction or scattering surface, such that different wavelengths or combinations of wavelengths of the measurement light are focused at each point along the first axis. By pairing the first aperture array located between the light source and the object being measured with a second aperture array located between the object being measured and an image sensor for measuring light reflected from the surface of the object being measured, measurement light reflected only from the intersection of the object being measured and the measurement plane reaches the image sensor.

[0010] The sensor's objective lens assembly is configured to image the first region of the first diffractive or scattering surface onto a measurement plane. At each point in the measurement plane, different wavelengths or combinations of wavelengths of the measurement light are focused at each point along the first axis, such as in the first region of the first diffractive or scattering surface.

[0011] The objective lens assembly is also configured to focus measurement light reflected from the intersection of the measurement plane and the surface of the object being measured onto a second diffraction or scattering surface.

[0012] The sensor also includes a second dispersive optical element arranged to receive measurement light diffracted from the second diffraction or scattering surface, and configured to disperse the received measurement light on the second aperture array and focus the measurement light within the apertures of the second aperture array such that measurement light of different wavelengths passes through each aperture of the second aperture array.

[0013] A measurement spectrometer is arranged to receive measurement light passing through the second aperture array and is configured to spatially disperse the received measurement light in each band onto an image sensor such that the position of the peak wavelength of the received measurement light in each band on the image sensor corresponds to the intersection of the measurement plane and the surface of the object being measured.

[0014] According to a first embodiment of the present invention, the first aperture array and the second aperture array are arrays of slits. Measurement light passing through each slit is incident on a common area of ​​the measurement plane and spatially dispersed, wherein different combinations of wavelengths from multiple bands are focused at different positions along a first axis of the measurement plane.

[0015] By independently adjusting the transmission power of each band, high dynamic range measurement light is projected onto the measurement plane and the surface of the object being measured. Within the measurement spectrometer, an optimal band or combination of bands can be selected at each point along the second axis perpendicular to the first axis of the measurement plane, maximizing the signal-to-noise ratio within the selected bands without saturating the sensor, thus allowing the sensor to adapt to different surface types, colors, and orientations.

[0016] Alternatively, by providing uniform transmission power for each band, a multispectral image of the object can be generated based on the received measurement light when scanning the measurement plane across the surface of the object.

[0017] According to a second embodiment of the invention, the first aperture array and the second aperture array are pinhole arrays. The pinholes can be arranged in rows, each row extending along the aperture array in a first direction such that the aperture of each row does not overlap with the aperture of any other adjacent row in a second direction perpendicular to the first direction. In this manner, the measuring light is projected onto the surface of the object being measured in a linear fashion, such that no adjacent points on the line have the same wavelength. This improves the isolation of measuring light received from adjacent points on the surface of the object being measured within the measuring spectrometer, thereby improving the accuracy of the optical sensor.

[0018] A second aspect of the invention relates to a method for measuring the displacement and / or profile of a surface of a measurement object using the aforementioned optical sensor. The method includes measuring the peak wavelength of light in one or more bands of measurement light reflected from the intersection of the measurement plane and the surface of the measurement object; and determining the displacement and / or profile of the surface of the measurement object based on one or more measured peak wavelengths.

[0019] According to one aspect, the present invention is an optical sensor comprising: a light source configured to emit multicolor measurement light, the multicolor measurement light including multiple wavelength bands; a first aperture array arranged to receive measurement light from the light source; a first diffraction or scattering surface; a first dispersive optical element arranged to receive measurement light passing through the first aperture array and arranged to disperse the received measurement light onto a first axis on the first diffraction or scattering surface, wherein different wavelength bands of the multiple wavelength bands are dispersed from different apertures of the first aperture array onto a first region of the first diffraction or scattering surface, such that different wavelengths or combinations of wavelengths of the measurement light are focused at each point along the first axis; a second diffraction or scattering surface; and an objective lens assembly configured to focus the first... The system comprises: a first region of a diffractive or scattering surface imaged onto a measurement plane and configured to focus measurement light reflected from the intersection of the measurement plane and the surface of the object being measured onto the second diffractive or scattering surface; a second aperture array; a second dispersive optical element arranged to receive measurement light diffracted or scattered from the second diffractive or scattering surface and configured to disperse the received measurement light on the second aperture array and focus at least a portion of the measurement light into the apertures of the second aperture array such that measurement light of a single wavelength band passes through each aperture of the second aperture array; and a measurement spectrometer arranged to receive the measurement light passing through the second aperture array and to measure the spectral content of the received measurement light within each measurement wavelength band.

[0020] The measurement spectrometer can be configured to disperse the received measurement light in each band onto an image sensor such that the position of the peak wavelength of the received measurement light in each band on the image sensor corresponds to the intersection of the measurement plane and the surface of the object being measured.

[0021] The first aperture array and the second aperture array can be either a slit array or a pinhole array.

[0022] When the aperture array is a pinhole array, the apertures can be arranged in rows extending in a first direction on the aperture array, such that the apertures of each row do not overlap with the apertures of any adjacent rows in a second direction perpendicular to the first direction. Optionally, at each point along the second axis perpendicular to the first diffraction or scattering surface, the measurement light focused at each adjacent point along the second axis belongs to a different wavelength band.

[0023] The first diffraction or scattering surface may include a mask covering a region of the surface of the first diffraction or scattering surface outside the first region, or the size of the first diffraction or scattering surface may be adjusted such that the first region covers the entire surface of the first diffraction or scattering surface.

[0024] The light source of the present invention may include a plurality of sub-light sources arranged in rows, wherein each row of sub-light sources has a different spectral output, and wherein the intensity of the light emitted by each row of sub-light sources is individually adjustable in order to adjust the relative intensity of each wavelength band.

[0025] The power of the measurement light in the first band is at least twice the power of the second measurement light in the second band.

[0026] The measurement spectrometer can be configured to measure the total or maximum intensity of measurement light received from each location on the measurement plane in at least two bands, for generating a multispectral reflectance measurement result of the surface of the object being measured.

[0027] Each aperture in the first aperture array has a corresponding aperture in the second aperture array, such that measurement light passing through a given aperture in the first aperture array and reflected from the intersection of the measurement object and the measurement plane passes only through the corresponding aperture in the second aperture array.

[0028] Each point in the first region of the first diffraction or scattering surface has a corresponding point on the measurement plane and on the surface at the focal point of the measurement light of the same wavelength or combination of wavelengths on the second diffraction or scattering surface.

[0029] The first and / or second diffraction or scattering surfaces can be the surfaces of a diffraction grating.

[0030] The first and / or second dispersive optical elements may include diffraction gratings.

[0031] The optical sensor of the present invention can be used to simultaneously measure the spectral characteristics of the surface of the object being measured as well as the displacement or contour of the object being measured.

[0032] In terms of method, the present invention is a method for measuring the displacement and / or profile of a surface of a measurement object using an optical sensor as described above, the method comprising: measuring the peak wavelength of light in one or more bands of measurement light reflected from the intersection of the measurement plane and the surface of the measurement object; and determining the displacement and / or profile of the surface of the measurement object based on one or more measured peak wavelengths.

[0033] The method may further include: measuring the peak wavelength of light in one or more bands of measurement light reflected from the intersection of the measurement plane and the surface of the measurement object at one or more different portions of the surface of the measurement object; determining the profile of each of the one or more different portions of the measurement object based on one or more measured peak wavelengths; and generating a three-dimensional model of the surface of the measurement object based on the determined profiles of the different portions of the surface of the measurement object.

[0034] In another aspect, the present invention is a method for obtaining a multispectral image of the surface of a measurement object using an optical sensor according to any of the aspects described above, the method comprising: generating an image of the surface of the measurement object based on the intensity of measurement light in each band reflected from the intersection of different portions of the surface of the measurement object with the measurement plane.

[0035] According to the method, at least one band has a transmission power different from at least one other band, and the method further includes selecting at least one band from the bands based on the quality of detection of the bands in the spectrometer to provide measurement data for at least one measurement point on the object being measured.

[0036] In another aspect, substantially uniform transmission power can be provided for the band, and the method also includes generating multispectral data or multispectral images of the object being measured.

[0037] At least one band has a transmission power different from at least one other band, and the method further includes selecting at least one band from the bands based on the quality of detection of the bands in the spectrometer to provide measurement data for at least one measurement point on the object being measured.

[0038] On the other hand, substantially uniform transmission power can be provided for the band and also includes generating multispectral data or multispectral images of the object being measured.

[0039] The foregoing may only cover some aspects of the invention. Other, and sometimes more specific, aspects of the invention will be understood by referring to the following description of preferred and other exemplary embodiments of the invention. The following embodiments for implementing the concepts of the invention are not intended to limit the invention itself, but are merely examples embodying the inventive features of the invention. Attached Figure Description

[0040] Preferred embodiments and other embodiments of the present invention will be described with reference to the accompanying drawings, wherein:

[0041] Figure 1 A sensor according to a first embodiment of the present invention is described.

[0042] Figure 2 The spatial distribution of the spectrum generated by the first dispersive optical element on the first diffraction or scattering surface is depicted.

[0043] Figure 3 An exemplary light source that may be part of the sensor of the present invention is depicted.

[0044] Figure 4 An exemplary measurement spectrometer that may be part of the sensor of the present invention is depicted.

[0045] Figure 5 A sensor according to a second embodiment of the present invention is depicted. Detailed Implementation

[0046] This invention relates to an optical sensor for measuring the displacement or contour of an object. Such a sensor can be used to scan the surface of the object being measured in order to determine the shape of the surface.

[0047] In the optical sensor according to the invention, measuring light passes through an aperture array (e.g., an array of pinholes or slits) onto a first dispersive optical element (e.g., a first diffraction grating).

[0048] The first dispersive optical element disperses the measurement light along a first axis on the surface of the first diffractive or scattering surface. The measurement light from each aperture is dispersed along the first axis at different positional ranges. Therefore, in a first region on the surface of the first diffractive or scattering surface, different, preferably non-spectrally overlapping, wavelengths of the measurement light are incident from each aperture. As a result, at each position along the first axis, different wavelengths or combinations of wavelengths are incident.

[0049] The objective lens assembly images a first region of the first diffractive or scattering surface onto the measurement plane. Therefore, similar to light incident on the surface of the first diffractive or scattering surface, the light focused at each point along the first axis of the measurement plane comprises different wavelengths or combinations of wavelengths. In a preferred embodiment, when using an optical sensor, the object being measured is positioned such that its surface intersects the measurement plane. Measurement light is reflected from the intersection of the object's surface and the measurement plane. The measurement light reflected back towards the objective lens assembly is focused by the objective lens assembly onto the surface of the second diffractive or scattering surface.

[0050] Measurement light diffracted from the second diffraction or scattering surface is incident on the second dispersive optical element, which is configured to focus the received measurement light within the apertures of the second aperture array, such that measurement light of a single wavelength band passes through each aperture of the second aperture array. The second diffraction or scattering surface, the second dispersive optical element, and the second aperture array essentially function as opposites to the first aperture array, the first dispersive optical element, and the first diffraction or scattering surface. Each aperture of the first aperture array has a corresponding aperture in the second aperture array. Measurement light passing through a given aperture in the first aperture array and reflected from the surface of the object being measured at the intersection of the object and the measurement plane passes through the corresponding aperture in the second aperture array (and only through that corresponding second aperture). This ensures that only the measurement light reflected from the intersection of the object being measured and the measurement plane ultimately reaches the measurement spectrometer, where the spectral content of the measurement light is determined.

[0051] It will be understood that for each surface point on the first diffraction or scattering surface, there exists a corresponding point on the surface at the focal point of the measurement light of the same wavelength or combination of wavelengths on the measurement plane and on the second diffraction or scattering surface.

[0052] Since the measuring light of different wavelengths or combinations of wavelengths is focused at each position along the first axis of the measuring plane, the position where the object being measured intersects the measuring plane along the first axis corresponds to the wavelength or combination of wavelengths with the highest intensity received at the measuring spectrometer.

[0053] The same measurements can be repeated for a measurement light focused at a range along a second axis of the measurement plane, perpendicular to the first axis. These measurements at other locations along the second axis allow for the determination of the two-dimensional profile of the object being measured. By scanning the surface of the object along a third axis of the measurement plane (e.g., perpendicular to both the first and second axes), a three-dimensional model of the object's surface can be constructed.

[0054] The optical sensor according to the invention will be described in more detail below with reference to the accompanying drawings.

[0055] Figure 1An optical sensor 100 according to a first embodiment of the present invention is depicted. A light source 101 emits measurement light composed of multiple different wavelength bands. (Described below) Figure 3 The light source 101 is described in more detail. The light source may consist of multiple sub-light sources, each of which emits a smaller number of wavelengths (e.g., a single wavelength) of measurement light.

[0056] Light source 101 illuminates aperture array 102, in Figure 1 In one embodiment, the aperture array 102 is an array of slits such that at least one band of the measurement light passes through each slit. For example, different bands may pass through each slit, or all bands may pass through all slits. In a first embodiment of the invention, to measure the contour of a measurement object, the sensor 100 projects a continuous line of measurement light onto the surface of the measurement object. The sensor 100 can also be used as a displacement sensor, in which case, instead of a line, the light from each aperture can be projected onto the surface of the measurement object by replacing the slit array 102 with an array of pinhole apertures arranged in a single column, as described below.

[0057] The first dispersive optical element 103 is arranged such that measurement light passing through the slit is incident on the dispersive optical element 103 (e.g., a diffraction grating), and the measurement light of each wavelength band is dispersed by the dispersive optical element 103 onto the first diffraction or scattering surface 104. This is in Figure 2 The following describes the process in more detail. The first dispersive optical element 103 may include a first diffraction grating as a dispersive element and intermediate optical elements 103a, 103b, such as lenses. Alternatively, prisms or a combination of gratings and prisms may be used to provide the desired dispersion of the measurement light. Similarly, more or fewer lenses than lenses 103a and 103b may be used.

[0058] Figure 2 The diagram illustrates dispersed measurement light 104i-104v from different slits in a slit array (such as slit array 102) on a diffracting or scattering surface 104. Spectrum 104i corresponds to measurement light from the first slit, spectrum 104ii corresponds to measurement light from the second slit, and so on. Within each spectrum 104i-104v, the measurement light is dispersed along the first axis FA; that is, within each spectrum, at each position along the first axis FA, a different wavelength of measurement light is incident. Figure 2 In the diagram, for illustrative purposes only, the different spectra 104i-104v of the dispersed measurement light are shown as perpendicularly spaced from each other and perpendicularly spaced from the first diffraction or scattering surface 104. In practice, each spectrum 104i-104v coincides with the surface of the diffraction grating 104. Figure 2The illustration shows five spectra 104i-104v. However, it will be understood that the following discussion can be generalized to any number of slits. In this illustration, each spectrum 104i-104v consists of five different wavelength bands AE. The arrangement of the slits in the slit array and the characteristics of the first dispersive optical element are chosen such that the different wavelength bands of each spectrum 104i-104v are incident on a first region 104a of the first diffraction or scattering surface. As a result, at each location along the first axis FA, a different wavelength or combination of wavelengths is incident. Since a single wavelength band is incident on region 104a from each slit of the slit array, the complete spectrum AE of the measured light does not necessarily have to pass through each slit. In fact, as discussed in... Figure 3 To explain in more detail, the light source can be configured to project a single band of measurement light through each slit of the slit array.

[0059] like Figure 2 As shown, the surface of the first diffraction or scattering surface 104 can be covered by a mask 104b outside region 104a. In this way, measurement light not incident in region 104a is attenuated. Alternatively, the first diffraction or scattering surface 104 can have the same size as region 104a.

[0060] At least a portion of the measurement light incident on the first diffraction or scattering surface 104 is diffracted toward the objective lens assembly 105. The first diffraction or scattering surface 104 is preferably a diffraction grating, configured such that measurement light diffracted from one or more diffraction modes is directed toward the objective lens assembly 105. When using a diffraction grating, it can be a reflection grating or a transmission grating. However, a simple scattering surface can also be used, such that some of the measurement light incident on a first region 104a of the first diffraction or scattering surface 104 is directed toward the objective lens assembly 105.

[0061] The objective lens assembly 105 is configured to image region 104a of the diffraction surface of the first diffraction or scattering surface 104 onto the measurement plane 106. Therefore, since different wavelength combinations are incident at each location within region 104a along the first axis FA of the first diffraction or scattering surface, these different wavelength combinations will also be imaged along the first axis of the measurement plane 106 (e.g., as shown in the image). Figure 1 The measurement plane can be defined as the plane in which the region of the diffraction grating 104a is focused by the objective lens assembly 105. The size of the measurement plane in the Z direction depends on the focal length of the objective lens assembly 105. In practice, due to imperfections in real-world optical systems, the measurement plane 106 has a position perpendicular to the first axis (e.g., parallel to the Z-axis). Figure 1 The non-zero thickness is measured along the Y-axis (as shown).

[0062] In use, the sensor is arranged such that the measurement plane 106 intersects the surface of the object being measured, MO, and the measurement light is reflected with the highest intensity from the surface of the object being measured, MO, at the intersection of the object being measured and the measurement plane 106, where the measurement light is focused. At least a portion of the measurement light reflected from the surface of the object being measured, MO, is reflected back to the objective lens assembly 105, where it is focused by the objective lens assembly 105 onto the surface of the second diffraction or scattering surface 107. The second diffraction or scattering surface 107 is configured to diffract or scatter at least a portion of the measurement light focused thereon toward the second dispersive optical element 108. Similar to the first diffraction or scattering surface 104, the second diffraction or scattering surface 107 is preferably a diffraction grating, which is configured such that measurement light diffracted from one or more diffraction modes is guided toward the second dispersive optical element 108. When using a diffraction grating, it can be a reflection grating or a transmission grating. However, a simple scattering surface can also be used, such that some of the measurement light incident on the second diffraction or scattering surface 107 is directed toward the second dispersive optical element 108.

[0063] Similar to the first dispersive optical element 103, the second dispersive optical element 108 may include a first diffraction grating as a dispersive element and intermediate optical elements 108a, 108b, such as lenses. The second dispersive optical element 108 receives measurement light diffracted or scattered from the second diffraction or scattering surface and disperses the received measurement light onto the surface of the second slit array 109, such that measurement light of a single wavelength band passes through each slit of the second slit array 109.

[0064] The second diffraction or scattering surface 107, the second dispersive optical element 108, and the second aperture array 109 essentially function in the opposite manner to the first slit array 102, the first dispersive optical element 103, and the first diffraction or scattering surface 104. This arrangement ensures that only measurement light of the desired wavelength band passes through the second slit array 109 to reach the measurement spectrometer 110. The optical path between the second diffraction or scattering surface 107 and the second slit array 109 may include one or more lenses or other optical components, such as... Figure 1 Lenses 108a and 108b, as shown, are used to properly focus the measurement light of each wavelength band onto the slit array 109. Figure 5 As shown, the slits of the first slit array 102 and the second slit array 109 do not need to be precisely aligned in the X-axis direction. The sensor of the present invention can still function if the slits are oriented at an angle in the XZ plane. Such an arrangement can be compensated for by post-processing the signal output from the sensor, for example, in control software.

[0065] In one example, such as Figure 1As shown, the objective lens assembly 105 includes an input lens 105a, a reflector 105b, an objective lens 105c, and an output lens 105d. The input lens 105a and objective lens 105c image a region 104a of the surface of the first diffraction or scattering surface 104 onto the measurement plane 106 via the reflector 105b. The objective lens 105c and output lens 105d image the measurement plane 106 onto the surface of the second diffraction or scattering surface 107. Alternative arrangements can be used, for example, where the reflector 105b is located in the path of the measurement light reflected from the measurement plane 106, rather than in the path of the measurement light projected from the light source 101 onto the measurement plane. Generally, any arrangement of the components that achieves the above functions can be used.

[0066] When the objective lens assembly 105 has the same focal length for the measurement light diffracted and focused onto the measurement plane 106 from the first diffraction or scattering surface 104 and the reflected measurement light received from the measurement plane 106 and focused onto the second diffraction or scattering surface 107, the arrangement of the first slit array 102, the first dispersive optical element 103, and the first diffraction or scattering surface 104 (and any intermediate lenses 103a, 103b or other optical components in the optical path between the first slit array 102 and the first diffraction or scattering surface 104) can be the same as the arrangement of the second slit array 109, the second dispersive optical element 108, and the second diffraction or scattering surface 107 (and any intermediate lenses 108a, 108b or other optical components in the optical path between the second slit array 109 and the second diffraction or scattering surface 107). Alternatively, the focal lengths of the input lens 105a, the objective lens 105c, and the output lens 105d may not all be the same. In this configuration, the sensor of the present invention still functions as described above and below, but the arrangement of the first slit array 102, the first dispersive optical element 103, and the first diffraction or scattering surface 104 (and any intermediate lenses 103a, 103b or other optical components in the optical path between the first slit array 102 and the first diffraction or scattering surface 104) will differ from the arrangement of the second slit array 109, the second dispersive optical element 108, and the second diffraction or scattering surface 107 (and any intermediate lenses 108a, 108b or other optical components in the optical path between the second slit array 109 and the second diffraction or scattering surface 107).

[0067] The measurement light passing through the second slit array 109 is received by the measurement spectrometer 110, which will be discussed below. Figure 4In more detail, the measurement spectrometer 110 measures the peak wavelength of the measurement light in each band passing through the second slit array 109. Since the focused wavelength of the measurement light in each measurement band is distributed along a first direction of the measurement plane 106, the peak wavelength of the measurement light reflected from the surface of the object being measured in each measurement band depends on the position where the surface of the object being measured intersects the measurement plane along that first direction. Therefore, by measuring the peak wavelength in one or more measurement bands, the distance of the object being measured MO from the sensor 100 can be determined.

[0068] Figure 3 The light source 101 is described in more detail. Figure 3 The light source 101 shown is an example of a light source using a row of sub-light sources, each with a different emission spectrum, which can be used with sensor 100. Other examples that can be used alternatively include white light regional light sources, as described above. Figure 3 The light source 101 includes multiple sub-light sources 101a-101f, which are arranged in rows on a substrate 101g (e.g., a PCB). Each row of sub-light sources 101a-101f includes multiple sub-light sources having substantially the same emission spectrum; for example, each sub-light source in sub-light sources 101a-101f is an LED, and the LEDs in each row have the same type / color. Figure 3 In the depicted example, the diffuser 101h is arranged adjacent to the sub-light source 101h to provide a more uniform light intensity across each row of sub-light sources 101a-101f, i.e., to smooth the peaks and troughs of the emitted power along each row. Other types of beam homogenization optical systems than the diffuser can be used. The light-collecting lens 101i can be located in the path of the measurement light between the diffuser 101h and the first slit array 102 to focus the measurement light from the sub-light sources 101a-101f onto the first slit array.

[0069] Each row of sub-light sources 101a-101f can emit measurement light including one or more bands of measurement light projected onto region 104a of the first diffraction or scattering surface 104 and thus focused onto the measurement plane 106. Therefore, the power of one or more bands can be independently adjusted relative to the power of other bands, such that at least one band has a different transmission power than at least one other band, and preferably, the transmission power of each band used in the measurement is different from the transmission power of each other band. This allows for measurements with a high dynamic range. This arrangement is particularly advantageous for measuring displacement / profile at different points on a measurement object that may be dark, poorly reflective, or highly tilted relative to the angle of incidence of the measurement light. While high-power measurement light projected onto the measurement object can saturate the sensor in portions of the measurement object where the measurement light is well reflected (e.g., those near the angle of incidence perpendicular to the measurement light), lower-power measurement bands still allow the collection of measurement light reflected from the surface without saturating the sensor in the region where that band is projected onto the sensor (as explained in more detail below). On the other hand, for surfaces with poor reflectivity, such as those closer to the incident angle parallel to the measurement light, lower power measurement bands may not produce a sufficiently strong signal on the sensor surface. In this case, higher power measurement bands no longer saturate the sensor and can provide a clear signal. The use of multiple measurement bands of different powers allows displacement / profile determination based on the optimal band, i.e., the band that provides the best signal-to-noise ratio without saturating the sensor. Specifically, the displacement or profile of the object can be determined by using measurement light of different bands or combinations of different bands at different points in the measurement plane (i.e., different points on the surface of the object being measured). In other words, at each point in the measurement plane corresponding to different columns of pixels on the image sensor, a band or combination of bands with the optimal power level is selected based on the detection quality of a given band, i.e., a band or combination of bands that provides a high signal-to-noise ratio without saturating the sensor, and used for displacement or profile measurement.

[0070] Alternatively, the power output of each row of sub-light sources 101a-101f can be controlled to provide a relatively uniform spectral power distribution. In this case, the absolute amount of reflected measurement light received and measured at the measurement spectrometer 110 can also be used to determine the spectral reflectance measurement results of the measurement object MO, and can ultimately be used to generate a multispectral or hyperspectral image of the surface of the measurement object while measuring the contour and 3D shape of the measurement object.

[0071] Figure 4 The measuring spectrometer 110 of sensor 100 is described in more detail. Figure 4The measurement spectrometer 110 shown is an example of a measurement spectrometer based on a diffraction grating that can be used with the sensor 100. Alternatively, a prism-based or... Figure 4 The arrangement shown is different from other arrangements of spectrometers, as long as they can perform the function of measuring the peak wavelength of the reflected measurement light in each band, as described in more detail below.

[0072] The measuring spectrometer 110 includes an image sensor 110a, such as a monochrome area camera, on which measuring light is projected through a spectrometer diffraction grating 110b and other optical elements of the measuring spectrometer 110 (such as lenses 110c, 110d).

[0073] Figure 4 The surface of image sensor 110a is also shown. Solid lines on the surface indicate the positions of intensity peaks in the measured light reflected from each band and projected onto the surface of image sensor 110a by the optical elements 110b-110d of the measurement spectrometer. Dashed lines indicate different regions on the surface of image sensor 110a onto which measurement light of different bands may be projected. Within each region, the vertical position of the intensity peak (as shown) is related to the wavelength of the intensity peak and therefore to the Z position of the surface of the object to be measured MO within measurement plane 106, and the horizontal position of each point (as shown) corresponds to the X position of measurement plane 106 from which the measurement light is reflected. Therefore, by measuring the vertical position of the received measurement light with the highest intensity within each region of the image sensor at each horizontal position on the image sensor, the position where the surface of the object to be measured MO intersects with measurement plane 106 within measurement plane 106 can be determined.

[0074] Furthermore, by measuring the contour of the object MO at different locations on the surface of the object (separated by known displacements and possible orientation changes), the 3D shape of the surface of the object can be reconstructed.

[0075] In addition to measuring the displacement and / or profile of the surface of the object being measured (MO), sensor 100 can also be used to capture or measure the spectral characteristics of the object's surface in each band of the measurement light, such as reflectance. Sensor 100 can perform the measurement of this spectral characteristic simultaneously with displacement / profile measurement. For this purpose, all bands of the measurement light preferably have substantially uniform power, allowing reflectance data to be accurately combined to create an image. For example, when using the red, green, and blue bands of visible light, a color image of the object's surface can be generated while scanning the object's profile. When using measurement light with more bands, multispectral reflectance data can be obtained. In alternative embodiments, the sensor can be used only to measure the spectral characteristics of the object's surface, such as obtaining a color or multispectral image, without measuring the object's displacement or profile. However, even when only the spectral characteristics of the object's surface are output, distance can still be measured by the sensor to calibrate the measurement results of the spectral characteristics, as explained in more detail below. The sensor of this invention is particularly advantageous for obtaining color or multispectral images of the surface of a measured object because the resulting image is focused at all points within the measurement plane, i.e., independent of the distance from the surface of the measured object to the sensor. This always-focused imaging is unattainable by conventional imaging methods.

[0076] When measuring the spectral properties of a surface, the received intensity depends on the optical power and spectral content of the measurement light projected onto the object, the optical efficiency of the sensor at different wavelengths, and the spectral reflectance of the surface of the object (i.e., the thing being measured). Consequently, the received intensity is also highly dependent on the distance between the object and the sensor. The effects of optical efficiency and illumination power can be compensated for by calibrating the sensor. This calibration can be performed by measuring the intensity received from a surface with known reflectivity (e.g., a white surface) at different measurement distances. The reference sample can be an absolute reference with accurately known reflectivity across all wavelengths in the measurement light band, or it can be a reference surface with known relative reflectivity across all wavelengths in the band. The calibration process can also include measuring the wavelength peaks within each band for all distances within the measurement area. The smoothness of the sensor's spectral sensitivity or the smoothness of the spectral content of the illumination intensity is not critical or necessary, as these can be corrected through calibration.

[0077] The sensor of this invention can also be used to measure the distance and color of multilayer films, and to determine the film thickness in a similar manner. In the case of multilayer films, there may be multiple local maxima in the spectral measurement results of the reflected measurement light, corresponding to the reflection of the measurement light from the interface of each layer of the multilayer film.

[0078] Figure 5A sensor 200 according to a second embodiment of the present invention is depicted. (As described above) Figure 1 Compared to sensor 100, sensor 200 uses an array of points or pinhole apertures 202, 209 instead of slit arrays 102, 109. Sensors that use only a single point or an array of discrete points to measure the displacement of a measured object are generally more accurate than those that use continuous lines because each point is spatially isolated from any other point. However, using an array of single points or discrete points significantly reduces the sensor's resolution along the direction in which the points are distributed, because the displacement of points on which the light does not fall cannot be measured at all. Figure 5 The sensor 200 uses aperture arrays 202 and 209 to project line measurement light onto a measurement plane 106, i.e., onto the object being measured, where each adjacent point on the line has a wavelength from a different band of the non-overlapping bands of the measurement light. In other words, each point of the projected measurement light is spectrally isolated from its neighbors and spatially isolated from other points having wavelengths in the same band. By also using spectral isolation between adjacent points, these points can be arranged more closely in space compared to using spatial isolation alone. Therefore, the sensor of this embodiment reduces crosstalk between adjacent points, increases the accuracy of displacement measurement at each point, and allows for increased resolution along the projection line of the point.

[0079] Figure 5 An exemplary arrangement of point / pinhole apertures on aperture array 202 is shown. As in the first embodiment, each slit in the slit array corresponds to a different wavelength band, such as... Figure 5 As shown, each position along direction D2 corresponds to a different wavelength band. Each position along direction D1 corresponds to a different position along the line projected onto the measurement plane, perpendicular to the direction of spectral dispersion of the point within the measurement plane 106. That is, each position along direction A on the aperture array 202 corresponds to a different position along the X-axis, such as... Figure 5 As shown.

[0080] The arrangement of apertures in aperture array 202 is exemplary. Any other arrangement of point or pinhole apertures can be used, as long as no apertures are directly adjacent along the direction corresponding to the spatial position in the measurement plane (i.e., direction A).

[0081] In another alternative, other types of apertures besides point or pinhole apertures can be used. For example, a combination of pinhole aperture and slit aperture can be used. In this way, by spatially and spectrally isolating discrete points in the measurement plane, some bands can be used to generate high-accuracy displacement measurements, while other bands can be projected onto the measurement plane along a continuous line through the slit aperture to provide continuous spectral reflectance data, for example, for simultaneously generating an image of the surface of the object being measured.

[0082] In the foregoing description, exemplary modes for carrying out the invention have been described by way of example. However, the scope of the claims should not be limited by these examples, but should be given the broadest interpretation consistent with the entire specification. Therefore, the specification and drawings are to be regarded as illustrative rather than restrictive.

Claims

1. An optical sensor, comprising: A light source is configured to emit multicolor measurement light, the multicolor measurement light comprising multiple wavelength bands; A first aperture array is arranged to receive measurement light from the light source; First diffraction or scattering surface; A first dispersive optical element is arranged to receive measurement light passing through the first aperture array and to disperse the received measurement light onto a first axis on the first diffraction or scattering surface, wherein different wavelengths of the plurality of bands are dispersed from different apertures of the first aperture array onto a first region of the first diffraction or scattering surface, such that different wavelengths or combinations of wavelengths of the measurement light are focused at each point along the first axis. Second diffraction or scattering surface; An objective lens assembly is configured to image the first region of the first diffraction or scattering surface onto a measurement plane, and is configured to focus measurement light reflected from the intersection of the measurement plane and the surface of the object being measured onto the second diffraction or scattering surface. Second aperture array; A second dispersive optical element is arranged to receive measurement light diffracted or scattered from the second diffraction or scattering surface, and is configured to disperse the received measurement light on the second aperture array and focus at least a portion of the measurement light into the apertures of the second aperture array, such that measurement light of a single wavelength band passes through each aperture of the second aperture array; and A measurement spectrometer is arranged to receive measurement light passing through the second aperture array and to measure the spectral content of the received measurement light within each measurement band.

2. The optical sensor of claim 1, wherein the measurement spectrometer is configured to disperse the received measurement light in each band onto an image sensor such that the position of the peak wavelength of the received measurement light in each band on the image sensor corresponds to the intersection of the measurement plane and the surface of the object being measured.

3. The optical sensor of claim 1, wherein the first aperture array and the second aperture array are slit arrays.

4. The optical sensor of claim 1, wherein the first aperture array and the second aperture array are pinhole arrays.

5. The optical sensor as claimed in claim 4, wherein... The apertures of the first aperture array and the second aperture array are arranged in rows extending in a first direction on the aperture array, such that the aperture of each row does not overlap with the aperture of any adjacent row in a second direction perpendicular to the first direction.

6. The optical sensor of claim 5, wherein at each point along the second axis perpendicular to the first diffraction or scattering surface, the measurement light focused at each adjacent point along the second axis belongs to a different wavelength band.

7. The optical sensor of claim 1, wherein the first diffraction or scattering surface comprises a mask covering a region of the surface of the first diffraction or scattering surface outside the first region, or wherein the size of the first diffraction or scattering surface is adjusted such that the first region covers the entire surface of the first diffraction or scattering surface.

8. The optical sensor of claim 1, wherein the light source comprises a plurality of sub-light sources arranged in rows, wherein each row of sub-light sources has a different spectral output, and wherein the intensity of the light emitted by each row of sub-light sources is individually adjustable to adjust the relative intensity of each wavelength band.

9. The optical sensor of claim 1, wherein the first power of the measurement light in the first band is at least twice the second power of the measurement light in the second band.

10. The optical sensor of claim 1, wherein the measuring spectrometer is further configured to measure the total intensity or maximum intensity of measuring light received from each location on the measuring plane in at least two wavelength bands, for generating a multispectral reflectance measurement result of the surface of the object being measured.

11. The optical sensor of claim 1, wherein each aperture in the first aperture array has a corresponding aperture in the second aperture array, such that measurement light passing through a given aperture in the first aperture array and reflected from the intersection of the measurement object and the measurement plane passes only through the corresponding aperture in the second aperture array.

12. The optical sensor of claim 1, wherein each point in the first region of the first diffraction or scattering surface has a corresponding point on the measurement plane and on the surface at the focal point of the measurement light of the same wavelength or combination of wavelengths of the second diffraction or scattering surface.

13. The optical sensor of claim 1, wherein the first diffraction or scattering surface is the surface of a diffraction grating, and / or wherein the second diffraction or scattering surface is the surface of a diffraction grating.

14. The optical sensor of claim 1, wherein the first dispersive optical element comprises a first diffraction grating for dispersive measurement light, and / or wherein the second dispersive optical element comprises a second diffraction grating for dispersive measurement light.

15. The optical sensor of claim 1, wherein the optical sensor is an optical sensor for simultaneously measuring the spectral characteristics of the surface of the object being measured and the displacement or profile of the object being measured.

16. A method for measuring the displacement and / or contour of a surface of a measurement object using an optical sensor as described in claim 1, the method comprising: Measure the peak wavelength of light in one or more bands reflected from the intersection of the measurement plane and the surface of the object being measured; as well as The displacement and / or profile of the surface of the measured object are determined based on one or more measured peak wavelengths.

17. The method of claim 16, further comprising: The peak wavelength of light reflected from the intersection of the measurement plane and the surface of the measurement object is measured at one or more different portions of the surface of the measurement object, within one or more wavelength bands. The profile of each of the one or more different parts of the measured object is determined based on one or more measured peak wavelengths; as well as A three-dimensional model of the surface of the measured object is generated based on the determined contours of different portions of the surface of the measured object.

18. A method for obtaining a multispectral image of the surface of a measurement object using an optical sensor as described in claim 1, the method comprising: An image of the surface of the object being measured is generated based on the intensity of measurement light in each band reflected from the intersection of different portions of the surface of the object with the measurement plane.

19. The method of claim 16, wherein at least one band has a transmission power different from at least one other band, the method further comprising selecting at least one band from the bands based on the quality of detection of the bands in the spectrometer to provide measurement data for at least one measurement point on the object being measured.

20. The method of claim 16, wherein substantially uniform transmission power is provided for the band, and the method further comprises generating multispectral data or a multispectral image of the object being measured.

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