Optical measuring apparatus and method

Abstract

The present invention relates to the field of optical measuring devices, and more particularly to displacement sensors, 3D sensors, or roughness sensors for measuring the position and / or shape or thickness of an object to be measured. Measuring light is projected onto the object to be measured after being filtered by a first Fabry-Perot filter, and at each point on the measuring surface, the filtered measuring light has a locally unique wavelength or combination of wavelengths in at least one direction within the measuring surface. Measuring light reflected from the surface of the object to be measured is filtered by a second Fabry-Perot filter to remove measuring light that has not been reflected from the intersection of the object to be measured and the measuring surface.

Description

Technical Field

[0001] The present invention relates to the field of optical measurement devices, and more particularly to displacement sensors, three-dimensional sensors for measuring the position and / or shape or thickness of a measurement object, or roughness sensors for measuring the surface roughness of an object.

Background Art

[0002] In many displacement sensors and three-dimensional profile sensors known in the prior art, light is projected onto a measurement object, the light reflected from the surface of the measurement object is measured, and the shape of the object is determined. In many such devices, the angle of incidence of light on an image sensor is offset from zero. Image sensors such as CCDs and APSs are not designed to operate at such angles, and as a result, performance deteriorates. In triangulation-based devices, the angle of incidence can be decreased by increasing the triangulation angle, but this strategy is limited by the physical constraints of the system. For example, the triangulation angle cannot be increased to 90 degrees because the sensor would occupy the same space as the measurement object. Further, increasing the triangulation angle has the undesirable side effect of increasing the occlusion of the reflected light due to changes in the height of the measurement object. The greater the triangulation angle, the smaller the change in height that causes occlusion. Further, the magnification that results in image enlargement causes further rotation of the intermediate image plane, and when the image sensor is disposed on the intermediate image plane, it effectively precludes the use of such magnification that may be useful for increasing the angle of incidence of light and improving the accuracy of the sensor.

Summary of the Invention

[0003] A first aspect of the invention relates to a sensor for measuring the displacement of a surface of a measurement object relative to the sensor. The sensor includes: · A light source configured to emit measurement light; · A first Fabry-Perot filter configured to filter the measurement light so that all parallel light has the same wavelength or combination of wavelengths; A first optical system configured to focus filtered measurement light onto a measurement plane, wherein the filtered measurement light at each point on the measurement plane has a locally unique wavelength or combination of wavelengths in at least one direction within the measurement plane; A second optical system configured to receive filtered measurement light reflected from the surface of the object being measured and to focus the measurement light reflected from the measurement surface at infinity; • A second Fabry-Perot filter configured to filter out measurement light that was not reflected from the measurement surface; • A sensor lens configured to focus the measurement light, filtered by a second Fabry-Perot filter, onto the sensor plane; A light sensor positioned on the sensor surface and configured to measure light filtered by a second Fabry-Perot filter.

[0004] The illumination axis extends from the light source to the measurement surface, and the measurement axis extends from the measurement surface to the light sensor. The first Fabry-Perot filter may be positioned relative to the illumination axis at a first Fabry-Perot filter tilt angle defined between the illumination axis and the normal vector of the first Fabry-Perot filter, and the second Fabry-Perot filter may be positioned relative to the measurement axis at a second Fabry-Perot filter tilt angle defined between the measurement axis and the normal vector of the second Fabry-Perot filter.

[0005] The first Fabry-Perot filter angle may be a non-zero angle.

[0006] The second Fabry-Perot filter angle may be a non-zero angle.

[0007] The rotation direction of the first Fabry-Perot filter tilt angle may be opposite to the rotation direction of the second Fabry-Perot filter tilt angle. In this configuration, the first and second optical systems may be mirror-image symmetric with respect to a plane of symmetry that is parallel to and aligned with the measuring surface, and the first Fabry-Perot filter angle and the second Fabry-Perot filter may have the same size.

[0008] The rotation direction of the tilt angle of the first Fabry-Perot filter may be the same as the rotation direction of the tilt angle of the second Fabry-Perot filter. In this configuration, the first and second optical systems may be mirror-image symmetric with respect to a plane of symmetry perpendicular to the measurement surface, and the first Fabry-Perot filter angle and the second Fabry-Perot filter may have the same size.

[0009] The spacing between internal reflective surfaces and the refractive index of the layers in the first Fabry-Perot filter may be the same as the spacing between internal reflective surfaces and the refractive index of the layers in the second Fabry-Perot filter.

[0010] When the sensor is in use, the measurement light incident on the optical sensor may have a locally unique wavelength or combination of wavelengths in at least one direction within the sensor plane. The term "locally unique" means that the wavelength or combination of wavelengths of the measurement light at each point in the plane is different from the wavelength or combination of wavelengths of the measurement light incident on all other points along at least one axis present in the plane.

[0011] The light sensor may be divided into multiple regions physically or logically, and each region may be sensitive to a single wavelength or a single combination of wavelengths of the light being measured. The regions of the light sensor may be individual pixels or groups of pixels.

[0012] The light source may be a diffuse, multicolor light source.

[0013] The light source and the first Fabry-Perot filter may be configured such that light is incident on each point in the illumination area on the surface of the first Fabry-Perot filter with a range of angles and wavelengths.

[0014] The light source may further include a light source lens configured to correct the angle of incidence of the measurement light so that the measurement light is incident within an angular range at each point in the illumination area of ​​the first Fabry-Perot filter.

[0015] The light source may include a series of parallel emission lines configured such that the measurement light is incident on the surface of the first Fabry-Perot filter as a series of parallel lines. Alternatively, the light source may be a surface light source that emits light from its entire surface.

[0016] In one configuration, the first optical system may include a first lens, and the second optical system may include a second lens. In this context, the lenses may be single lenses or composite lenses. The focal planes of the first and second lenses may be coplanar and overlapping within the measuring plane.

[0017] The first lens may be tilted with respect to the illumination axis by a first lens angle, and as a result, the focal plane of the first lens is tilted with respect to the illumination axis by the first lens angle. The second lens may be tilted with respect to the measurement axis by a second lens angle, and as a result, the focal plane of the second lens is tilted with respect to the measurement axis by the second lens angle.

[0018] The first lens angle is defined by the angle between the optical axis of the first lens and the illumination axis, and the second lens angle is defined by the angle between the optical axis of the second lens and the measurement axis.

[0019] The first lens angle may be equal to the second lens angle.

[0020] The first and second lenses may be arranged symmetrically with respect to the measuring surface.

[0021] In another configuration, the first optical system may include a first irradiation optical system configured to focus the filtered measurement light on a first focal plane, an irradiation diffraction grating aligned with the first focal plane and configured such that the filtered measurement light forms a focus across the entire irradiation diffraction grating, and a second irradiation optical system configured to focus the measurement light diffracted by the irradiation diffraction grating on a measurement surface. The second optical system may include a first measurement optical system configured to focus the measurement light reflected from the measurement surface on a first image plane, a measurement diffraction grating aligned with the first image plane and configured such that the reflected measurement light forms a focus across the entire measurement diffraction grating, and a second measurement optical system configured to focus the measurement light diffracted by the measurement diffraction grating at infinity.

[0022] The mean incident angle of the measurement light with respect to the irradiation diffraction grating may be substantially zero, and the mean diffraction angle of the light from the measurement diffraction grating may be substantially zero. The term "substantially zero" means that the magnitude of the angle is less than 5 degrees.

[0023] In any of the above configurations, the irradiation axis and the measurement axis may be on the opposite side of the measurement surface.

[0024] Alternatively, the irradiation axis and the measurement axis may be on the same side of the measurement surface.

[0025] The angle between the irradiation axis and the measurement surface may be greater than 45 degrees, less than 35 degrees, less than 25 degrees, or less than 15 degrees.

[0026] The angle between the measurement axis and the measurement surface may be greater than 45 degrees, less than 35 degrees, less than 25 degrees, or less than 15 degrees.

[0027] The angle between the irradiation axis and the measurement surface may be the same as the angle between the measurement axis and the measurement surface.

[0028] The angle between the measurement axis and the measurement surface is 90 degrees.

[0029] In yet another configuration, the first optical system may include a first illumination optical system configured to focus filtered measurement light onto a first focal plane, an illumination diffraction grating aligned with the first focal plane and configured so that filtered measurement light is focused across the entire illumination diffraction grating, and a second illumination optical system configured to focus the measurement light diffracted by the illumination diffraction grating onto the measurement surface. The second optical system may include a second lens, i.e., a single lens or a composite lens, and the focal plane of the second lens may be coplanar with and overlapping with the measurement surface.

[0030] A second aspect of the invention relates to a sensor device for measuring the surface shape of an object to be measured. The sensor device includes the aforementioned sensor, a stage for holding the object to be measured, and a moving mechanism configured to move the sensor along a first movement vector relative to the stage, or a moving mechanism configured to move the stage along a first movement vector relative to the sensor. The measuring surface is offset from the first movement vector by a measuring surface offset angle.

[0031] The measurement surface offset angle may be 5 degrees or less, 6 degrees or less, 7 degrees or less, 8 degrees or less, 9 degrees or less, or 10 degrees or less.

[0032] The stage may be a conveyor belt, and the moving mechanism may be a conveyor mechanism.

[0033] A third aspect of the invention relates to a method. The method includes positioning an object to be measured at a first position relative to the sensor described above, such that the surface of the object to be measured intersects with the measuring surface, and measuring the intensity of light received by the optical sensor.

[0034] The method may further include repositioning the object to be measured from a first position to a second position, the change in the position of the object to be measured being defined by a first displacement vector, and measuring the intensity of light received by a light sensor.

[0035] The method may further include determining the displacement of a first set of points, consisting of one or more points on the surface of an object, by identifying the locations of one or more light intensity peaks measured by a light sensor when the object is in a first position.

[0036] The method may further include determining the displacement of a second set of points, consisting of one or more points on the surface of the object being measured, by identifying the locations of one or more light intensity peaks measured by the optical sensor when the object being measured is in a second position.

[0037] The method may further include generating a three-dimensional model of the object to be measured by combining the displacements of a first set of points, the displacements of a second set of points, and a first displacement vector.

[0038] The method may further include determining the thickness of the transparent layer of the object being measured by calculating the distance between at least two different light intensity peaks on the light sensor.

[0039] A fourth aspect of the invention relates to measuring the displacement of the surface of an object relative to a sensor, measuring the profile of an object, measuring the three-dimensional shape of an object, and / or measuring the thickness of a transparent layer of an object, using the sensor described above. [Brief explanation of the drawing]

[0040] [Figure 1] This is a schematic diagram of the first optical sensor. [Figure 2] This is a schematic diagram of the second optical sensor. [Figure 3] This is a schematic diagram of the third optical sensor. [Figure 4] This is a schematic diagram of the fourth optical sensor. [Modes for carrying out the invention]

[0041] The present invention relates to an apparatus, system, and method for measuring the displacement of an object relative to a sensor, or an apparatus, system, and method for measuring the surface roughness of an object. Both types of sensors employ the same basic principle. That is, the measurement light is filtered using a Fabry-Perot filter before being projected onto the object, so that at each point on the measurement plane intersecting the object, the measurement light has a locally unique wavelength or combination of wavelengths in the distance measurement direction. The measurement light reflected from the surface of the object is then filtered by a second Fabry-Perot filter to remove the measurement light not reflected from the measurement plane. The basic operation of the apparatus and method for measuring the displacement of an object relative to a sensor, or the apparatus and method for measuring the surface roughness of an object, is described in relation to claim 1, but the basic principle of using the Fabry-Perot filter described above is common to all embodiments of the present invention.

[0042] In this context, "filtering" or "attenuating" does not mean completely removing measurement light reflected from outside the measurement surface, but rather reducing the intensity of that light. As described below, high-finesse Fabry-Perot filters can more effectively filter out measurement light not reflected from the measurement surface, leading to more accurate measurements, but the present invention also works with relatively low-finesse Fabry-Perot filters or filters.

[0043] The sensor 100 in Figure 1 includes a light source 101 configured to emit polychromatic measurement light. The emitted measurement light may have a relatively narrow bandwidth or emit light over a broad spectrum, but the spectrum must be sufficiently broad to pass through the first Fabry-Perot filter 102 (details below). The term “measurement light” is used throughout this specification, but the device is not limited to electromagnetic radiation in the visible wavelength range and may include infrared, ultraviolet or other wavelengths depending on the specific application.

[0044] The measurement light emitted from the light source 101 is incident on the first Fabry-Perot filter 102. The light source 101 is preferably a diffuse surface light source, emitting light from various points on its surface over a wide angular range. Therefore, the measurement light incident on the first Fabry-Perot filter 102 is associated with an angular range. The light source 101 may be a single light source or multiple light sources. The light source 101 may emit light from its entire surface or may include multiple parallel emission lines.

[0045] In this context, the term “Fabry-Perot filter” preferably refers to an etalon with a fixed distance between reflectors, but other types of Fabry-Perot filters, such as interference filters and interferometers with adjustable distances between reflectors, can also be used. The wavelength of light transmitted through a Fabry-Perot filter is defined by the distance l between reflectors, the refractive index n of the materials between the reflectors, and the angle θ of incidence of the light to the Fabry-Perot filter. The transmission peak occurs when the optical path length 2nl cos α of the light reflected between the reflectors is an integer multiple of the wavelength λ of the incident light. Therefore, when the refractive index n and the distance l between reflectors are fixed, the wavelength of light transmitted through a Fabry-Perot interferometer depends on the angle α of incidence of the light within the Fabry-Perot filter, i.e., the angle with respect to the reflector surface. Thus, when measurement light is incident on the first Fabry-Perot filter 102, some of the light incident at different angles is not filtered by the first Fabry-Perot filter 102.

[0046] Since the angle of incidence of the measurement light and the angle of exit from the Fabry-Perot filter are essentially the same, all parallel light filtered by the first Fabry-Perot filter 102 has the same wavelength or combination of wavelengths.

[0047] As shown in Figure 1, the normal vector of the first Fabry-Perot filter 102 is offset by an angle of 131 from the illumination axis 121 extending from the light source 101 to the measurement surface 152.

[0048] The tilt of the first Fabry-Perot filter 102 can be defined by axial angle representation. In this case, the axis of rotation is defined by a unit vector, the direction of rotation of the first Fabry-Perot filter is indicated by the sign (i.e., positive or negative) of the unit vector according to the right-hand rule, and the magnitude of the rotation is indicated by an angle. Using this definition, the tilt angle 131 can be described by a unit vector extending parallel to the Y-axis. The angle is measured between the illumination axis 121 and the normal vector of the Fabry-Perot filter 102, i.e., the angle 131 shown in Figure 1.

[0049] The filtered light is focused on the measuring surface 152 through the first optical system 103. In the embodiment of Figure 1, the first optical system 103 is depicted as a single lens, but in reality it may be a composite lens, or a composite optical system including optical elements other than lenses, as shown in Figure 3. Where the term “lens” is used herein, it means a single lens or a composite lens unless otherwise specified. In either case, the function of the first optical system is the same: to focus the light filtered by the first Fabry-Perot filter onto the measuring surface. All parallel light is focused on the focal plane of the first optical system, i.e., the same point on the measuring surface 152, and since all parallel light has the same wavelength or combination of wavelengths due to filtering by the Fabry-Perot filter, the light focused on any point on the measuring surface 152 has the same wavelength or combination of wavelengths.

[0050] The measurement light, filtered by the first Fabry-Perot filter 102 and focused by the first optical system 103, is reflected from the surface of the object to be measured 151. The intensity of the reflected light is maximum at the point where the surface of the object to be measured 151 intersects with the measurement surface 152, i.e., where the measurement light focuses on the surface of the object to be measured 151. The measurement light is usually scattered, i.e., diffusely reflected from the surface of the object to be measured 151. A portion of this reflected measurement light enters the second optical system 104. The second optical system 104, like the first optical system 103, is positioned so that its focal plane aligns with the measurement surface 152. As a result, the measurement light reflected from the measurement surface 152 is focused to infinity by the second optical system 104. In other words, light rays reflected from a point on the measurement surface 152 propagate parallel to each other after passing through the second lens 104. In the embodiment of Figure 1, the second optical system 104 is a lens, but as shown in Figure 3, the second optical system 104 may be a composite optical system. In either case, the function of the second optical system is the same: to focus the light reflected from the intersection of the object being measured and the surface being measured to infinity, and to ensure that all light rays entering the second optical system from a single point on the surface being measured propagate in parallel after exiting the second optical system.

[0051] This reflected measurement light is focused to infinity by the second optical system 104 and then incident on the second Fabry-Perot filter 105. The second Fabry-Perot filter 105 is configured to filter out measurement light that has not been reflected from the measurement surface. Since all light focused on a point on the measurement surface 152 has the same wavelength or combination of wavelengths, the light rays propagating parallel from the second optical system 104 have the same wavelength or combination of wavelengths. Therefore, when light reflected from the measurement surface 152 is incident on the second Fabry-Perot filter 105 at a specific angle of incidence, the light has the same wavelength or combination of wavelengths and can pass through the second Fabry-Perot filter. On the other hand, light reflected from other parts of the measurement object 151 that do not intersect with the measurement surface 152 generally does not have the same wavelength and is filtered by the second Fabry-Perot filter 105.

[0052] Filtering of the reflectance measurement light by the second Fabry-Perot filter 105 can be achieved by selecting an appropriate tilt angle 132 of the second Fabry-Perot filter 105. Similar to the axial angle representation used for the tilt angle 131 of the first Fabry-Perot filter 102 described above, the tilt angle 132 can be described by a unit vector extending parallel to the Y-axis. The angle is measured between the measurement axis 122 and the normal vector of the second Fabry-Perot filter 105, i.e., the angle 132 shown in Figure 1.

[0053] This configuration is particularly effective when the wavelength or combination of wavelengths of light focused at each point on the measuring surface is locally unique in at least one direction within the measuring surface. In other words, it is desirable that the wavelength or combination of wavelengths of light focused at points located along at least one axis within the measuring surface is unique. Preferably, this axis is parallel to the Z-axis shown in the drawing. To put it another way, at each point on the measuring surface having the same Y-coordinate, light of different wavelengths or combinations of wavelengths is focused.

[0054] The performance of the optical sensor 100, that is, its ability to measure the height of the object to be measured 151 (position on the Z-axis at each Y-coordinate), is improved when the wavelength or combination of wavelengths of light focused at each point on the measuring surface 152 is unique among points having the same Y-coordinate. Therefore, it is desirable that the angle 131 of the first Fabry-Perot filter 102 is set with respect to the illumination axis 121 and the entire angular range used so that the wavelength or combination of wavelengths of light focused at each point on the measuring surface is unique among points having the same Y-coordinate.

[0055] As described above, the first Fabry-Perot filter 102 is preferably tilted by rotating it around an axis parallel to the measurement plane and perpendicular to the irradiation axis 121 with respect to the irradiation axis 121. In the illustration in Figure 1, this axis is the Y-axis. In the embodiment of Figure 1, the rotation axis of the first Fabry-Perot filter 102 and the rotation axis of the first lens 103 are parallel. The offset angle 131 is measured in the ZX plane.

[0056] The angle of incidence of light to the first Fabry-Perot filter 102, i.e., the angle of incidence, may be restricted to only positive or negative angles in order to avoid light of the same wavelength or combination of wavelengths being transmitted at two different angles of incidence.

[0057] The reflected filter measurement light emitted from the second Fabry-Perot filter enters the sensor lens 106 and is focused on the sensor plane, i.e., the focal plane of the sensor lens 106. Again, since the angle of incidence to the Fabry-Perot filter and the angle of exit of the light transmitted through the second Fabry-Perot filter are the same, the reflected measurement rays from a single point on the measurement surface 152 have the same wavelength or combination of wavelengths, propagate parallel to the sensor lens 106, and are focused on the same point on the sensor plane.

[0058] The image sensor 107 is positioned on the sensor surface, with its effective surface aligned with the sensor surface, so that the reflected filter measurement light is focused on the effective surface of the image sensor. The image sensor may be a CCD (charge-coupled device), CMOS (complementary metal-oxide-semiconductor), other APS (active pixel sensor), or line scan camera.

[0059] By measuring the intensity of light received at each point (e.g., each pixel) of the image sensor, the shape of the object to be measured 151 can be determined at the intersection with the measurement surface 152.

[0060] An image sensor can be physically or logically divided into multiple regions, such as individual pixels or groups of pixels. Each region is sensitive to only a single wavelength or combination of wavelengths, or a narrow range of wavelengths or combinations of wavelengths.

[0061] By filtering the measurement light and the light reflected from the measurement surface 152 using the first and second Fabry-Perot filters 102 and 105, a very sharp and narrow image is formed on the image sensor 107, enabling more accurate measurement of the profile of the object being measured 151. The position of this line on the sensor 107 depends on the intersection point of the surface of the object being measured 151 and the measurement surface 152.

[0062] As shown in Figure 1, the optical axis of the lens of the first optical system 103 is offset by an angle of 143 from the illumination axis 121 extending from the light source 101 to the measurement surface 152. As a result, the measurement surface 152, defined by the overlapping focal planes of the first optical system 103 and the second optical system 104, is tilted with respect to the illumination axis 121. The optical axis of the lens of the second optical system 104 is also offset by an angle of 144 with respect to the measurement axis 122 extending from the measurement surface to the image sensor. If lenses with the same focal length are used for the first optical system 103 and the second optical system 104, angle 143 is equal to angle 144. The tilt angle of lens 103 also tilts the angle of the focal plane of lens 103, i.e., the measurement surface 152. The tilt angles of lenses 103 and 104 are aligned so that their focal planes coincide with each other.

[0063] The first and second Fabry-Perot filters 102, 105 may be adjusted so that the measurement light reflected from the measurement surface 152 passes through the second Fabry-Perot filter 105. This can be achieved by adjusting the angle 131 of the first Fabry-Perot filter with respect to the irradiation axis 121, or by adjusting the angle 132 of the second Fabry-Perot filter with respect to the measurement axis 122, or by adjusting both angles 131 and 132. Alternatively, if a Fabry-Perot interferometer or interferometer filter with an adjustable reflector distance is used, this can be used to ensure the performance of the device and can be used in addition to, or as an alternative to, the relative angle adjustment of the Fabry-Perot filters. It is preferable to use an etalon or other Fabry-Perot filter with a fixed reflector distance, which usually requires adjustment only once during the manufacturing process. For example, the angle adjustment of one or both Fabry-Perot filters 102, 105 can be achieved by screws that adjust the angle of the Fabry-Perot filters.

[0064] The ability to adjust the device by changing the angle of the reflectors and / or the distance between reflectors allows for a simpler and less demanding manufacturing process, as minor imperfections can be corrected after production.

[0065] The reflectivity of the reflective surface within the Fabry-Perot filter determines the width of the transmission peak of the Fabry-Perot filter in the frequency (or wavelength) region. A Fabry-Perot filter with a narrow transmission peak, i.e., a high Q value, is said to have high finesse. By using a high-finesse Fabry-Perot filter, the accuracy of the sensor of the present invention is improved. This is because the filtering of the measurement light reflected from outside the measurement surface by the second Fabry-Perot filter 105 is improved, resulting in a narrower intensity peak on the sensor 107. However, if the transmission peaks of the Fabry-Perot filters 102 and 105 are narrow, more precise matching of the first and second Fabry-Perot filters 102 and 105 is required to ensure the desired overlap of the transmission peaks. Therefore, the ability to precisely adjust the angles of the Fabry-Perot filters 102 and 105 as described above makes it possible to use a high-finesse Fabry-Perot filter.

[0066] In the embodiment shown in Figure 1, the first Fabry-Perot filter 102, the first optical system 103, the second optical system 104, and the second Fabry-Perot filter 105 are arranged mirror-symmetrically with respect to the measuring surface 152. In this case, the focal lengths of the first optical system 103 and the second optical system 104 are the same, and the interreflector distance and the refractive index of the interreflector material in the first Fabry-Perot filter 102 and the second Fabry-Perot filter 105 are also the same. The inclination angles 131 and 132 of the first and second Fabry-Perot filters 102 and 105 are also the same, but their rotation directions are opposite. That is, one Fabry-Perot filter 102 and 105 are rotated clockwise, and the other is rotated counterclockwise.

[0067] It is understood that perfect mirror-image symmetry between the illumination optical system and the measurement optical system is not required, even if the first optical system 103 has the same optical properties as the second optical system 104, and the first Fabry-Perot filter 102 has the same optical properties as the second Fabry-Perot filter 105. In particular, the positions of each Fabry-Perot filter 102, 105 are adjustable along their respective illumination or measurement axes, and can be adjusted without changing the incident or exit angle of the measurement light. Therefore, the positions of the Fabry-Perot filters 102, 105 do not need to be identical, but it is sufficient that the magnitudes of the inclination angles 131 and 132 are the same.

[0068] The apparatus 100 may be configured to include an additional lens between the light source 101 and the first Fabry-Perot filter 102 to ensure that light is incident across the entire surface of the first Fabry-Perot filter 102 within an angular range. This makes it possible to use a smaller or less diffusive light source. This can be achieved, for example, by placing the light source outside the focal plane of the additional lens. When the light source is small, a larger angular range from the light source to the focusing lens is required to obtain the same angle and power distribution in the first Fabry-Perot filter 102.

[0069] The bandwidth of the light source 101 may be limited based on the offset (tilt) angle of the first Fabry-Perot filter 102 and the incident angle range of the Fabry-Perot filter 102 in order to ensure local uniqueness of the wavelength or combination of wavelengths that are in focus on the measurement surface and / or sensor surface.

[0070] Limiting the light source bandwidth can be achieved by using a suitable narrowband light source such as an LED, or by additionally filtering the light emitted from the broadband light source 101 before it is incident on the measurement surface 152.

[0071] Alternatively, if a broadband light source is used, the measurement light can be filtered to an appropriate wavelength range at any position between the light source 101 and the sensor 107, ensuring local uniqueness of the wavelength or combination of wavelengths that are focused on the sensor surface.

[0072] Figure 2 shows a second optical sensor 200, which operates in essentially the same manner as described above with respect to the displacement sensor 100 in Figure 1. Equivalent features of both devices are indicated by similar reference numerals. For example, 101 and 201 both represent the light sources described above.

[0073] Sensor 200 differs from displacement sensor 100 in that the illumination axis 221 and the measurement axis 222 are located on the same side of the measurement surface 252. In the embodiment shown in Figure 2, both the first optical system 203 and the second optical system 204 are inclined lenses, and the inclination direction of each lens with respect to the illumination axis 221 or the measurement axis 222 is opposite to the inclination direction of the corresponding lens in displacement sensor 100.

[0074] To accommodate the fact that the illumination axis and measurement axis are on the same side of the measurement surface 252, one of the offset angles 231 and 232 of the Fabry-Perot filters 202 and 205 is inverted with respect to the illumination axis 221 or the measurement axis 222, respectively, compared to the corresponding angles 131 and 132 in the sensor 100. In other words, in the sensor 200, the rotation direction of both Fabry-Perot filters 202 and 205 is the same, and both are either clockwise or both are counterclockwise, as defined by the Y axis in Figure 2.

[0075] Such reversal of the wavelength scale direction in the irradiation and measurement sections cannot be achieved with conventional confocal sensors that use, for example, prisms or diffraction gratings. Therefore, by using a Fabry-Perot filter with such opposite tilt angles, the configuration shown in Figure 2 (and Figure 4 described below) becomes possible.

[0076] Furthermore, the entire apparatus 200 is tilted with respect to the surface of the object being measured 251, and the measuring surface 252 is tilted at a small angle, for example, less than 10 degrees, with respect to the surface of the object being measured 251. Alternatively, the tilt of the apparatus 200 may be defined with respect to the stage that holds the object being measured, or with respect to the motion vectors by which the sensor and the stage move relative to each other. In either case, the measuring surface 252 is consequently nearly parallel to the surface of the object being measured 251, and relatively small changes in the height of the object being measured 251 result in large changes at the intersection of the measuring surface 252 and the surface of the object being measured. This leads to large changes in the position of maximum light intensity on the image sensor 207.

[0077] One advantage of this sensor configuration is that the illumination angle and measurement angle, i.e., the angle between the illumination axis 221 and the measurement surface 252, and the angle between the measurement axis 222 and the measurement surface, can be very large. This results in a large triangulation angle effect, which makes the spatial separation of different wavelengths very large compared to the change in height of the object being measured. Even very small differences in the height of the object's surface cause the same wavelength of light rays in the receiver and imager to be spatially separated. As a result, the lines in the receiving camera become sharper compared to when the illumination angle and measurement angle are small.

[0078] This sensor 200 can also be a highly sensitive area 3D scanning sensor if it scans the surface along the X-axis, as shown in Figure 2, and calculates the correct three-dimensional coordinates using the known X-coordinates of the measurement points corresponding to the measured Z-coordinates. This method allows for obtaining accurate three-dimensional coordinates of the surface using a nearly horizontal measurement plane direction.

[0079] As an alternative to the embodiment shown in Figure 2, when the illumination axis 221 extends perpendicularly from the measurement surface 252, the optical axis of the lens of the first optical system 203 is not offset from the illumination axis 221. In this case, the magnification of the optical system or the characteristics of the Fabry-Perot filters for illumination and imaging are appropriately modified to match the wavelength or combination of wavelengths for illumination and imaging at the measurement surface. Such a configuration reduces the overall size of the sensor 200 and mitigates the negative optical effects caused by tilting the lens 203 relative to the illumination axis 221. As yet another alternative, when the measurement axis 222 extends perpendicularly from the measurement surface 252, the optical axis of the lens of the second optical system 204 is not offset from the measurement axis 222.

[0080] Figure 3 shows a third optical sensor 300, which corresponds to the optical displacement sensor 100 described above with respect to Figure 1, but differs in that the first optical system 303 and the second optical system 304 include multiple lenses and diffraction gratings.

[0081] In particular, the first optical system 303 includes a first illumination optical system 311, an illumination diffraction grating 312, and a second illumination optical system 313. The first illumination optical system 311 is configured to focus the light filtered by the Fabry-Perot filter 302 onto the first focal plane. The first illumination optical system may be a single lens, a compound lens, or another optical system suitable for performing this function. The illumination diffraction grating 312 is aligned with the first focal plane so that the measurement light filtered by the first Fabry-Perot filter 302 is focused across the entire illumination diffraction grating. The second illumination optical system 313 is configured to focus the light diffracted by the illumination diffraction grating 312 onto the measurement surface 352.

[0082] Since all parallel rays emitted from the first Fabry-Perot filter 302 have the same wavelength or combination of wavelengths, the measurement light focused on each point of the first focal plane by the first illumination optical system 311 has the same wavelength or combination of wavelengths.

[0083] The surface of the irradiation diffraction grating 312 is aligned with the first focal plane of the first irradiation optical system 311. The diffraction angle θ of the light from the diffraction grating. m These are the grooves or slit pitch d of the diffraction grating (also called groove or slit spacing), the wavelength λ of the incident light, and the angle of incidence θ. i According to this, the lattice equation

[0084]

number

[0085] This is determined by the following: Here, m is the mode number, and m∈N={0,1,2,3…}. Incident angle θ i and diffraction angle θ m The direction is defined with respect to a plane parallel to the grooves or slits of the diffraction grating, and in the opposite direction with respect to a plane extending perpendicular to the planar surface of the diffraction grating (also called the grating normal).

[0086] The filtered measurement light is diffracted from the surface of the illumination diffraction grating 312 toward the second illumination optical system 313. The second illumination optical system 313 focuses the light diffracted from the surface of the illumination diffraction grating 312 onto the measurement surface 352. In other words, in an optical system consisting of the illumination diffraction grating 312, the second illumination optical system 313, and the measurement surface 352, the illumination diffraction grating 312 is located on the object plane, the lens plane is defined by the second illumination optical system 313, and the measurement surface 352 is located on the image plane defined by the Schein-Proof principle.

[0087] The angle 312 between the illumination diffraction grating 312 and the optical axis 321b extending to the measurement surface 352 is determined by the diffraction of light from the diffraction grating. Preferably, the second illumination optical system 313 is positioned so that as many diffracted light as possible is incident on the second illumination optical system 313 and therefore focused on the measurement surface 352. This is achieved when as many diffraction modes as possible across the wavelength range and incident angle range of the light incident on the illumination diffraction grating 312 are incident on the second illumination optical system 313. Thus, the angle 312 and the angle of the measurement surface 352 with respect to the optical axis 321b can be adjusted by changing the wavelength of the light used for measurement light emitted from the light source 301, or by changing characteristics such as the grooves or slit pitch of the diffraction grating.

[0088] In Figure 3, the second illumination optical system 313 is shown as a composite lens, but in reality, it may be any suitable optical system that performs the function of focusing light from the diffraction grating surface on the measurement surface.

[0089] In combination, the first optical system 303 of the displacement sensor 300 performs the same function as the first optical system 103 of the displacement sensor 100 and the first optical system 203 of the sensor 200. That is, it focuses the measurement light filtered by the first Fabry-Perot filter onto the measurement surface, which is inclined with respect to the illumination axes 121, 221, 321a and 321b extending from the light source or the first Fabry-Perot filter to the measurement surface.

[0090] Changing the angle of the measurement surface 352 relative to the irradiation axis 321b using a diffraction grating allows for a more accurate distribution of the wavelength of the measurement light on the measurement surface 352 than simply tilting the lens as shown in Figure 1. Tilting the lens exacerbates the imperfections of the lens and can cause wavelength blurring on the measurement surface.

[0091] The second optical system 304 of the displacement sensor 300 includes a first measuring optical system 314, a measuring diffraction grating 315, and a second measuring optical system 316. The first measuring optical system 314 is configured to focus the measurement light reflected from the measuring surface 352 onto the first image plane. The measuring diffraction grating 315 is aligned with the first image plane so that the measurement light reflected from the measuring surface 352 and focused by the first measuring optical system 314 is focused across the entire surface of the measuring diffraction grating 315. The measurement light diffracted from the measuring diffraction grating 315 is incident on the second measuring optical system 316, which is configured to focus the measurement light diffracted from the measuring diffraction grating 315 to infinity.

[0092] Similar to the situation described above with respect to the first optical system 304, in an optical system consisting of a measuring surface 352, a first measuring optical system 314, and a measuring diffraction grating 315, the measuring surface 352 is located on the object plane, the lens plane is defined by the first measuring optical system 314, and the measuring diffraction grating 315 is located on the image plane according to the Scheinproof principle.

[0093] The second measuring optical system 316 is configured to focus the measurement light diffracted by the measuring diffraction grating 315 to infinity. Therefore, the second measuring optical system 316 is positioned so that the focal plane of the lens aligns with the surface of the diffraction grating, i.e., the first image plane.

[0094] Again, in combination, the second optical system 304 of the displacement sensor 300 performs the same function as the second optical system 104 of the displacement sensor 100 and the second optical system 204 of the sensor 200. That is, it focuses the measurement light reflected from the measurement surface to infinity.

[0095] In Figure 3, both the irradiation diffraction grating 312 and the measurement diffraction grating 315 are shown as reflective diffraction gratings, but one or both may be transmission diffraction gratings.

[0096] Preferably, the optical properties of the first illumination optical system 311 are the same as those of the second measurement optical system 316, the optical properties of the illumination diffraction grating 312 are the same as those of the measurement diffraction grating 315, and the optical properties of the second illumination optical system 313 are the same as those of the first measurement optical system 314. In this configuration, the first optical system 303 and the second optical system 304 are arranged symmetrically with respect to the measurement surface 352. Furthermore, the first optical system 303 and the second optical system 304 can be manufactured using the same parts or group of parts, which simplifies the manufacture of the displacement sensor and improves its accuracy.

[0097] Figure 4 shows the fourth sensor 400, which uses the same composite optical system as the displacement sensor 300, with the first optical system 403 and the second optical system 404. Similar to the sensor 200, the illumination axis 421b and the measurement axis 422b are located on the same side of the measurement surface 452. This is achieved by rotating the first and second optical systems by 180 degrees with respect to the illumination axis 421b and the measurement axis 422b, respectively, compared to the displacement sensor 300. As described above with respect to Figure 2, the offset angles 431 and 432 of the Fabry-Perot filters 402 and 405 are in opposite signs, reversing the wavelength scales of the illumination and measurement sections of the sensor. Apart from these rotations and the reverse tilt of the Fabry-Perot filters, the configuration and advantages of the sensor 400 are the same as those of the displacement sensor 300. The sensor 400 essentially functions in the same way as described above with respect to the sensor 200.

[0098] Any of the displacement sensors described above can be used as three-dimensional sensors to measure the three-dimensional shape of an object being measured. A three-dimensional model of the object can be constructed by imaging the measurement light projected at multiple locations on the object. In practice, displacement measurements are performed repeatedly or continuously as the object passes through the measurement surface. This can be achieved by moving the sensor relative to a stationary object or by moving the object relative to the sensor (for example, on a conveyor belt). Each measurement can be considered to measure the profile of a cross-sectional slice of the object, and the three-dimensional shape of the object can be reconstructed by combining these profile measurements with the known displacements between each measurement.

[0099] The sensor can also be used for multilayer measurements. For example, it can be used to measure the thickness of a transparent film. When measurement light is reflected from the surface of each layer of the transparent film, identifiable intensity peaks are generated. Then, if the refractive index of each layer is known, the thickness can be calculated based on the distance between two consecutive peaks.

[0100] Furthermore, if the optical sensor is an image sensor such as a CCD, APS, or CMOS sensor, it can simultaneously measure displacement as described above and acquire a normal 2D image of the surface of the object being measured.

Claims

1. Sensors (100, 200, 300, 400) for measuring the displacement of the surface of a measuring object (151, 251, 351, 451) relative to the sensor, wherein the sensor includes: Light sources (101, 201, 301, 401) configured to emit measurement light; A first Fabry-Perot filter (102, 202, 302, 402) configured to filter the measurement light so that all parallel light has the same wavelength or combination of wavelengths; A first optical system (103, 203, 303, 403) configured to focus filtered measurement light onto the measurement surface (152, 252, 352, 452); Here, at each point on the measurement surface, the filtered measurement light has a locally unique wavelength or combination of wavelengths in at least one direction within the measurement surface; A second optical system (104, 204, 304, 404) configured to receive filtered measurement light reflected from the surface of the object being measured and to focus the measurement light reflected from the measurement surface to infinity; Second Fabry-Perot filters (105, 205, 305, 405) configured to filter out measurement light that is not reflected from the measurement surface; Sensor lenses (106, 206, 306, 406) configured to focus the measurement light filtered by the second Fabry-Perot filter onto the sensor surface; and Image sensors (107, 207, 307, 407) are positioned on the sensor surface and configured to measure light filtered by a second Fabry-Perot filter.

2. The sensor according to claim 1: The irradiation axes (121, 221, 321a-b, 421a-b) extend from the light source (101, 201, 301, 401) to the measurement surface (152, 252, 353, 452); The measurement axes (122, 222, 322a-b, 422a-b) extend from the measurement surface to the image sensors (107, 207, 307, 407); The first Fabry-Perot filter (102, 202, 302, 402) is positioned with respect to the illumination axis at the first Fabry-Perot filter tilt angle (131, 231, 331, 431) defined between the illumination axis and the normal vector of the first Fabry-Perot filter; A sensor in which a second Fabry-Perot filter (105, 205, 305, 405) is positioned relative to the measurement axis at a second Fabry-Perot filter tilt angle (132, 232, 332, 432) defined between the measurement axis and the normal vector of the second Fabry-Perot filter.

3. A sensor according to claim 2, wherein the first Fabry-Perot filter angle (131, 231, 331, 431) is a non-zero angle.

4. A sensor according to claim 2 or 3, wherein the second Fabry-Perot filter angle (132, 232, 332, 432) is a non-zero angle.

5. A sensor according to any one of claims 2 to 4, wherein the rotation direction of the first Fabry-Perot filter tilt angle (131, 331) is opposite to the rotation direction of the second Fabry-Perot filter tilt angle (132, 332).

6. A sensor according to claim 5, wherein a first optical system (103, 303) and a second optical system (104, 304) are arranged in mirror symmetry with respect to a plane of symmetry that is parallel and aligned with the measuring surface, and the first Fabry-Perot filter angle (131, 331) and the second Fabry-Perot filter angle (132, 332) are of the same magnitude.

7. A sensor according to any one of claims 2 to 4, wherein the rotation direction of the first Fabry-Perot filter tilt angle (231, 431) is the same as the rotation direction of the second Fabry-Perot filter tilt angle (232, 432).

8. A sensor according to claim 7, wherein a first optical system (203, 403) and a second optical system (204, 404) are arranged in mirror symmetry with respect to a plane of symmetry perpendicular to the measuring surface, and the first Fabry-Perot filter angle (231, 431) and the second Fabry-Perot filter angle (232, 432) are of the same magnitude.

9. The sensor according to any one of claims 1 to 8, wherein the inter-internal reflective surface distance and refractive index of the layers of the first Fabry-Perot filter (102, 202, 302, 402) are the same as the inter-internal reflective surface distance and refractive index of the layers of the second Fabry-Perot filter (105, 205, 305, 405).

10. The sensor according to any one of claims 1 to 9, wherein when the sensor is in use, the measurement light incident on the image sensor (107, 207, 307, 407) has a locally unique wavelength or combination of wavelengths in at least one direction within the sensor surface.

11. The sensor according to any one of claims 1 to 10, wherein "locally unique" means that the wavelength or combination of wavelengths of the measured light at each point in the plane is different from the wavelength or combination of wavelengths of the measured light at all other points along at least one axis in the plane.

12. The sensor according to claim 10 or 11, wherein the image sensor (107, 207, 307, 407) is divided physically or logically into multiple regions, and each region is sensitive only to measurement light of a single wavelength or a combination of single wavelengths.

13. The sensor according to claim 12, wherein the regions of the image sensor (107, 207, 307, 407) are individual pixels or groups of pixels.

14. The sensor according to any one of claims 1 to 13, wherein the light source (101, 201, 301, 401) is a diffusive polychromatic light source.

15. The sensor according to claim 14, wherein the light sources (101, 201, 301, 401) and the first Fabry-Perot filters (102, 202, 302, 402) are configured such that light is incident on each point of the illumination area on the surface of the first Fabry-Perot filter within an angular range and a wavelength range.

16. The sensor according to claim 15, wherein the light sources (101, 201, 301, 401) further include light source lenses, the light source lenses being configured to modify the angle of incidence of the measurement light to the surface of the first Fabry-Perot filter such that the measurement light is incident on each point in the illumination area of ​​the first Fabry-Perot filter within an angular range.

17. The sensor according to any one of claims 1 to 16, wherein the light source (101, 201, 301, 401) includes a series of parallel light rays, and the measurement light is incident on the surface of a first Fabry-Perot filter (102, 202, 302, 402) as a series of parallel rays.

18. The sensor according to any one of claims 1 to 17, wherein the first optical system includes a first lens (103, 203), the second optical system includes a second lens (104, 204), and the focal planes of the first lens and the second lens are coplanar and overlapping within the measuring plane (152, 252).

19. The sensor according to claim 18: The illumination axis extends from the light source (101, 201) to the measurement surface (152, 252); The measurement axis extends from the measurement surface to the image sensor (107, 207); The first lens is inclined with respect to the illumination axis at a first lens angle (143, 243), and the focal plane of the first lens is inclined with respect to the illumination axis at a first lens angle; A sensor in which the second lens is tilted with respect to the measurement axis at a second lens angle (144, 244), and the focal plane of the second lens is tilted with respect to the measurement axis at the second lens angle.

20. The sensor according to claim 19, wherein the first lens angle is defined by the angle between the optical axis of the first lens (103, 203) and the illumination axis, and the second lens angle is defined by the angle between the optical axis of the second lens (104, 204) and the measurement axis.

21. The sensor according to claim 19 or 20, wherein the first lens angle (143, 243) is equal to the second lens angle (144, 244).

22. The sensor according to claim 21, wherein the first lens (103, 203) and the second lens (104, 204) are arranged in mirror symmetry with respect to the measuring surface (152, 252).

23. The sensor according to any one of claims 18 to 22, wherein the first lens is a composite lens and / or the second lens is a composite lens.

24. A sensor according to any one of claims 1 to 17, wherein the first optical system includes: A first illumination optical system (311, 411) configured to focus the filtered measurement light onto the first focal plane; Irradiation diffraction gratings (312, 412) aligned to the first focal plane such that filtered measurement light is focused across the entire irradiation diffraction grating; A second illumination optical system (313, 413) is configured to focus the measurement light diffracted by the illumination diffraction grating onto the measurement surface (352, 452); And the second optical system includes the following: A first measuring optical system (314, 414) configured to focus the measuring light reflected from the measuring surface onto the first image plane; A measurement diffraction grating (315, 415) aligned with the first image plane such that the reflected light is focused across the entire measurement diffraction grating; A second measurement optical system (316, 416) is configured to focus the measurement light diffracted by the measurement diffraction grating to infinity.

25. The sensor according to claim 23, wherein the average incident angle of the measurement light incident on the irradiation diffraction grating (312, 412) is essentially zero, and the average diffraction angle of the measurement light diffracted from the measurement diffraction grating (315, 415) is essentially zero.

26. The sensor according to claim 24, wherein "essentially zero" means that the magnitude of the angle is less than 5 degrees.

27. A sensor according to any one of claims 1 to 25: The illumination axis extends from the light source (101, 301) to the measurement surface (152, 352); The measurement axis extends from the measurement surface to the image sensor (107, 307); A sensor in which the irradiation axis and the measurement axis are located on opposite sides of the measurement surface.

28. A sensor according to any one of claims 1 to 25: The illumination axis extends from the light source (201, 401) to the measurement surface (252, 452); The measurement axis extends from the measurement surface to the image sensor (207, 407); A sensor in which the irradiation axis and the measurement axis are located on the same side of the measurement surface.

29. The sensor according to claim 27, wherein the angle between the irradiation axis (221, 421b) and the measuring surface (252, 452) is greater than 45 degrees, less than 35 degrees, less than 25 degrees, or less than 15 degrees.

30. The sensor according to claim 27 or 28, wherein the angle between the measuring axis (222, 422b) and the measuring surface (252, 452) is greater than 45 degrees, less than 35 degrees, less than 25 degrees, or less than 15 degrees.

31. The sensor according to any one of claims 27 to 29, wherein the angle between the irradiation axis (221, 421b) and the measuring surface (252, 452) is the same as the angle between the measuring axis and the measuring surface.

32. The sensor according to claim 27 or 28, wherein the angle between the measuring axis (222, 422b) and the measuring surface is 90 degrees.

33. The sensor according to claim 31, wherein the first optical system includes: A first illumination optical system (311, 411) configured to focus the filtered measurement light onto the first focal plane; Irradiation diffraction gratings (312, 412) aligned to the first focal plane such that filtered measurement light is focused across the entire irradiation diffraction grating; A second illumination optical system (313, 413) is configured to focus the measurement light diffracted by the illumination diffraction grating onto the measurement surface (352, 452); The sensor comprises a second optical system including a second lens, the focal plane of which is coplanar with and overlapping the measuring surface.

34. A sensor for measuring the surface shape of an object, comprising: The sensor according to any one of claims 27 to 32; A stage for holding the object to be measured; A moving mechanism configured to move a sensor along a first movement vector relative to a stage, or to move a stage along a first movement vector relative to a sensor; Here, the measuring surface (252, 452) is offset by the measuring surface offset angle with respect to the first movement vector.

35. The sensor according to claim 33, wherein the measurement surface offset angle is 5 degrees or less, 6 degrees or less, 7 degrees or less, 8 degrees or less, 9 degrees or less, or 10 degrees or less.

36. The sensor according to claim 33 or 34, wherein the stage is a conveyor belt and the moving mechanism is a conveyor mechanism.

37. Method: The object to be measured is positioned at a first position relative to the sensor, so that the surface of the object intersects with the measurement surface; A method for measuring the intensity of light received by an optical sensor.

38. The method according to claim 37, further comprising: The object to be measured is repositioned from the first position to the second position, and the change in the position of the object to be measured is defined by the first displacement vector; A method for measuring the intensity of light received by an optical sensor.

39. A method according to claim 37 or 38, further comprising: A method for determining the displacement of one or more points on the surface of an object by identifying the positions of one or more intensity peaks of light measured by a light sensor when the object is in a first position.

40. The method according to claim 39, further comprising: A method for determining the displacement of one or more second points on the surface of a measurement object by identifying the positions of one or more intensity peaks of light measured by a light sensor when the measurement object is in a second position.

41. The method according to claim 40, further comprising: A method for generating a three-dimensional model of a measured object by combining the displacement of one or more first points, the displacement of one or more second points, and a first displacement vector.

42. The method according to claim 37, further comprising: A method for determining the thickness of the transparent layer of an object to be measured by calculating the distance between at least two different intensity peaks on a light sensor.

43. A use of the sensor according to any one of claims 1 to 36, wherein the sensor is used to measure the displacement of the surface of an object to be measured relative to the sensor, to measure the profile of an object to be measured, to measure the three-dimensional shape of an object to be measured, and / or to measure the thickness of a transparent layer of an object to be measured.

Images