Optical measurement system

Abstract

The present invention relates to a displacement sensor, such as one used in a 3D sensor for measuring the three-dimensional shape of an object. A diffraction grating is used to reduce the angle of incidence of the measurement light onto an optical sensor, such as an image sensor, thereby improving the performance of the optical sensor. The displacement sensors of the present invention include triangulation-based sensors and coaxial sensors.

Description

Technical Field

[0001] The present invention relates to a displacement sensor such as used in a 3D sensor for measuring, for example, the three-dimensional shape of an object.

Background Art

[0002] In many displacement sensors and 3D profile sensors known in the art, in order to determine the shape of an object, light is projected onto the measurement object, and the light reflected from the surface of the measurement object is measured. The incident angle of light on the image sensor in many such devices is offset from zero. Image sensors such as CCDs and APSs are not designed to operate at such angles, and as a result, their performance deteriorates. In triangulation-based devices, the incident angle can be reduced by increasing the triangulation angle, but this strategy is limited by the physical constraints of the system. For example, since the sensor would occupy the same space as the measurement object, it is not possible to increase the triangulation angle up to 90 degrees. Also, increasing the triangulation angle has an undesirable side effect that the shadow of the reflected light caused by a change in the height of the measurement object becomes larger. The larger the triangulation angle, the smaller the height change that causes the shadow. Furthermore, the magnification that leads to image enlargement causes further rotation of the intermediate image plane, increasing the incident angle of light on the image sensor when placed on the intermediate image plane, and essentially precluding the use of such magnification that could otherwise be useful for improving the accuracy of the sensor.

Summary of the Invention

[0003] A first aspect of the present invention relates to a sensor for measuring the displacement of the surface of a measurement object with respect to the sensor. The sensor is · a light source configured to project measurement light within a measurement plane, such that when the sensor is used, the measurement light is reflected from the surface of the measurement object at the intersection of the surface of the measurement object with the measurement plane; A first intermediate optical system positioned along a first measurement axis and configured to focus the measurement light reflected from the first side of the measurement surface onto an intermediate image plane, A second intermediate optical system positioned along a second measurement axis and configured to focus the measurement light reflected from the second side of the measurement surface onto an intermediate image plane, • At least one diffraction grating aligned with an intermediate image plane, wherein reflected measurement light is incident on the surface of the diffraction grating and is diffracted along a third measurement axis, A third intermediate optical system positioned along the third measurement axis and configured to focus the diffracted measurement light onto the sensor image plane, A light sensor is configured to measure the diffracted measurement light incident on the light sensor, and is aligned with the sensor's image plane, such that the diffracted measurement light is focused on the light sensor. It holds.

[0004] The angle of incidence of the measurement light from the first measurement axis on the diffraction grating can be greater than the diffraction angle of the measurement light from the first measurement axis on the diffraction grating, and the angle of incidence of the measurement light from the second measurement axis on the diffraction grating can be greater than the diffraction angle of the measurement light from the second measurement axis on the diffraction grating.

[0005] The measuring surface can be defined by the intersection of the focal plane of the intermediate image plane via the first intermediate optical system and the volume from which the measurement light is projected along the measurement axis. The sensor according to claim 1.

[0006] The focal plane of the intermediate image plane through the second intermediate optical system can be coplanar and overlap with the focal plane of the intermediate image plane through the first intermediate optical system.

[0007] The measurement light reflected from the first side of the measurement surface can enter the first portion of the diffraction grating, and the measurement light reflected from the second side of the measurement surface can enter the second portion of the diffraction grating.

[0008] The above-mentioned at least one diffraction grating may have two diffraction gratings, the first portion of the at least one diffraction grating may be provided by a first diffraction grating, and the second portion of the at least one diffraction grating may be provided by a second diffraction grating.

[0009] Light diffracted from the first part of the diffraction grating can be focused onto the first part of the light sensor, and light diffracted from the second part of the diffraction grating can be focused onto the second part of the light sensor.

[0010] The first and second parts of the diffraction grating can not overlap.

[0011] The first and second parts of the light sensor can be made to not overlap.

[0012] The first measurement axis can be offset from the projection axis by a first triangulation angle, and the second measurement axis can be offset from the projection axis by a second triangulation angle.

[0013] The first triangulation angle may be the same as the second triangulation angle.

[0014] The first triangulation angle and the second triangulation angle may be different.

[0015] The wavelength or wavelength range of the light source, the pitch of the grooves or slits of the diffraction grating, and the first and second triangulation angles may be configured such that the third measurement axis is perpendicular to the diffraction plane.

[0016] The first intermediate optical system may have a first subset, a first specular reflector, and a second subset, which may be configured such that the measurement light reflected on the first side of the measuring surface enters the first subset of the first intermediate optical system, exits the first subset of the first intermediate optical system, is reflected by the first specular reflector at a first reflection angle, enters the second subset of the first intermediate optical system, and exits the second subset of the first intermediate optical system, so that the measurement light is focused on the intermediate image plane.

[0017] The second intermediate optical system can have a first subset, a second mirror reflector, and a second subset, and the measurement light reflected on the second side of the measurement surface enters the first subset of the second intermediate optical system, exits the first subset of the second intermediate optical system, is reflected by the second mirror reflector at a second reflection angle, enters the second subset of the second intermediate optical system, and exits the second subset of the second intermediate optical system, and the measurement light can be configured to be focused on the intermediate image plane.

[0018] The magnifications of the first subset of the first intermediate optical system, the second subset of the first intermediate optical system, the first subset of the second intermediate optical system, and the second subset of the second intermediate optical system, the first reflection angle, and the second reflection angle can be configured such that the focal plane of the intermediate image plane via the second intermediate optical system is in the same plane as and overlaps the focal plane of the intermediate image plane via the first intermediate optical system.

[0019] The first intermediate optical system and the second intermediate optical system can be arranged mirror-symmetrically with respect to the measurement surface.

[0020] The light source can further have an optical element for forming projection light within the measurement surface.

[0021] The light source can be configured to project a line of light extending across the measurement surface onto the measurement object.

[0022] The light source can be configured to project one or more light points onto the measurement object.

[0023] The light source can be a laser or an LED.

[0024] The light sensor can be an image sensor such as a charge-coupled device or an active pixel sensor, for example.

[0025] The light sensor can be positioned such that the incident angle of the measurement light diffracted onto the light sensor is basically zero.

[0026] The diffraction angle of the measurement light from the diffraction grating can basically be zero.

[0027] One or both of the first intermediate optical system and the second intermediate optical system can have a magnification other than 1.

[0028] In this context, "basically zero" can mean that the magnitude of the angle is less than 5 degrees.

[0029] The diffraction grating can be a transmission diffraction grating, or the diffraction grating can be a reflection diffraction grating.

[0030] The diffraction grating can be a curved diffraction grating, and the curvature of the diffraction grating is the same as the curvature of the intermediate image plane.

[0031] The sensor can be configured to identify the local maximum light intensity on the optical sensor and calculate the distance to the surface of the measurement object based on the position of the local maximum light intensity.

[0032] The sensor can be configured to measure the reflectivity of the surface of the measurement object based on the magnitude of the corresponding local intensity peak.

[0033] The sensor can be configured to identify a plurality of local maximum light intensities on the optical sensor where each local maximum light intensity corresponds to the reflection of the measurement light from the transparent layer of the measurement object, and calculate the distance to each transparent layer of the measurement object based on the position of the local maximum light intensity.

[0034] A second aspect of the present invention relates to a sensor for measuring the displacement of the surface of a measurement object with respect to the sensor. The sensor is · a light source configured to project measurement light in the measurement plane along the projection axis, such that when the sensor is used, the measurement light is reflected from the surface of the measurement object at the intersection of the surface of the measurement object with the measurement plane, A first intermediate optical system positioned along a first measurement axis and configured to focus the measurement light reflected from the measurement surface onto an intermediate image plane, wherein the first measurement axis is coaxial with the projection axis, A diffraction grating aligned with an intermediate image plane, wherein reflected measurement light is incident on the surface of the diffraction grating, and the measurement light is diffracted along a second measurement axis, A second intermediate optical system positioned along the second measurement axis and configured to focus the diffracted measurement light onto the sensor image plane, A light sensor is configured to measure the diffracted measurement light incident on the light sensor, and is aligned with the sensor's image plane, such that the diffracted measurement light is focused on the light sensor. It holds.

[0035] The diffraction angle of the measurement light from the diffraction grating can be smaller than the angle of incidence of the measurement light onto the diffraction grating.

[0036] The diffraction grating can be coplanar with the measurement surface.

[0037] The diffraction grating can be Ronchi-ruled.

[0038] Diffraction gratings can operate in both reflection and transmission modes.

[0039] The thickness of the diffraction grating can be less than 500 μm.

[0040] The diffraction grating can further be configured to diffract the measurement light along a third measurement axis, the third measurement axis being coaxial with the second measurement axis and extending from the opposite side of the diffraction grating, and the sensor can further A third intermediate optical system positioned along the third measurement axis and configured to focus the diffracted measurement light onto the second sensor image plane, A second photosensor is aligned with the image plane of a second sensor, and the diffracted measurement light is focused on the second photosensor, and the second photosensor is configured to measure the diffracted measurement light incident on the second photosensor, It may have.

[0041] The sensor further, A second diffraction grating positioned so as to be mirror-symmetric with respect to the measurement surface, • At least one reflector configured to reflect measurement light from a first side of the measurement surface onto a first diffraction grating, and measurement light from a second side of the measurement surface onto a second diffraction grating, It may have.

[0042] The second intermediate optical system may be configured to focus the light diffracted from the first diffraction grating and the light diffracted from the second diffraction grating onto the sensor image plane.

[0043] The optical path length between the measuring surface and the optical sensor for measurement light from the first side of the measuring surface can be the same as the optical path length between the measuring surface and the optical sensor for measurement light from the second side of the measuring surface.

[0044] The second intermediate optical system may further include a beam combiner for coupling the measurement light from a first side of the measurement surface with the measurement light from a second side of the measurement surface, so that the measurement light from both sides of the measurement surface is incident on the photosensor.

[0045] Measurement light from the first side of the measuring surface can be incident on the first part of the light sensor, and measurement light from the second side of the measuring surface can be incident on the second part of the light sensor.

[0046] The first and second parts of the light sensor can be different, non-overlapping parts of the light sensor.

[0047] The light source may further include optical elements for forming projected light within the measurement surface.

[0048] The light source may be configured to project a line of light extending across the measurement surface onto the object being measured.

[0049] The light source may be configured to project one or more points of light onto the object to be measured.

[0050] The light source may be a laser or an LED.

[0051] The optical sensor may be an image sensor such as a charge-coupled device or an active pixel sensor.

[0052] The light sensor can be positioned such that the angle of incidence of the measured light diffracted onto the light sensor is essentially zero.

[0053] The diffraction angle of the light measured from the diffraction grating can be essentially zero.

[0054] One or both of the first and second intermediate optical systems may have a magnification of a value other than 1.

[0055] In this context, "basically zero" can mean that the angle is less than 5 degrees.

[0056] A diffraction grating can be a transmission diffraction grating, or it can be a reflection diffraction grating.

[0057] A diffraction grating can be a curved diffraction grating, and the curvature of the diffraction grating is the same as the curvature of the intermediate image plane.

[0058] The sensor may be configured to identify the local maximum light intensity on the light sensor and to calculate the distance to the surface of the object being measured based on the location of the local maximum light intensity.

[0059] The sensor may be configured to measure the reflectance of the surface being measured based on the magnitude of the corresponding local intensity peak.

[0060] The sensor may be configured to identify multiple local maximum light intensity points on the light sensor, where each local maximum light intensity point corresponds to the reflection of the measured light from the transparent layer of the object being measured, and to calculate the distance to each transparent layer of the object being measured based on the location of the local maximum light intensity points.

[0061] A further aspect of the present invention relates to a method for measuring the displacement of a surface to be measured relative to a sensor of any of the preceding claims. The method comprises identifying a local maximum light intensity on an optical sensor and calculating the distance to the surface to be measured based on the location of the local maximum light intensity.

[0062] A further aspect of the present invention relates to a method for measuring the thickness of a transparent film. The method comprises projecting measurement light onto the transparent film using one of the sensors described above, and determining the distance on the photosensor between at least two maximum intensity values ​​resulting from the reflection of the measurement light from the surface of the transparent film.

[0063] A further aspect of the present invention relates to a 3D sensor having any of the above-described sensors.

[0064] A further aspect of the present invention relates to a method for measuring the three-dimensional shape of an object to be measured. The method comprises repeatedly measuring the two-dimensional profile of the object to be measured using the 3D sensor described above at different positions on the object, and generating output data having a plurality of measured two-dimensional profiles and the displacement between the measured two-dimensional profiles.

[0065] A further aspect of the present invention relates to a method for generating a three-dimensional model of a measurement target. The method comprises measuring the three-dimensional shape of a measurement target in accordance with the method for measuring the three-dimensional shape of a measurement target described above, and generating a three-dimensional model of the measurement target by processing a plurality of measured two-dimensional profiles of the measurement target and the displacements between the measured two-dimensional profiles. [Brief explanation of the drawing]

[0066] [Figure 1] This is a schematic diagram of a sensor according to the first embodiment of the present invention. [Figure 1A] Figure 1 is a perspective view showing a portion of the sensor. [Figure 1B] This is a schematic diagram showing the diffraction angle and incident angle from the diffraction grating in the sensor of the present invention. [Figure 2] This is a schematic diagram of a sensor according to a second embodiment of the present invention. [Figure 3] This is a schematic diagram of a sensor according to a third embodiment of the present invention. [Figure 4] This is a schematic diagram of a sensor according to a fourth embodiment of the present invention. [Modes for carrying out the invention]

[0067] The term "sensor" as used herein refers to an individual element or a larger system that outputs a signal corresponding to the characteristics of a measured state of an object or environment. For example, optical sensors such as CCDs (charge-coupled devices) or APSs (active pixel sensors) can be used to measure light incident on the sensor, particularly images, while composite sensors such as 3D profile measuring sensors may include a sensor such as a CCD or APS, as well as other elements such as optical systems and light sources used in conjunction with the CCD or APS.

[0068] Throughout the following explanation, the terms “perpendicular,” “basically perpendicular,” “zero angle,” and “basically zero angle” are used to refer to the alignment of different optical elements with respect to the optical axis, vector, and other optical elements. To be understood, “perpendicular” and “zero angle” are impossible to actually achieve and represent idealized versions of the system depicted in the schematic diagrams described below. The terms “basically perpendicular” and “basically zero angle” are used to reflect this reality. When such terms and phrases are used, the intended range of these terms is broader than their strictly idealized meaning. Both “perpendicular” and “basically perpendicular” preferably mean 90 degrees ± 1 degree, but can also include 90 degrees ± 2, 3, 4, 5, or 10 degrees. Both “zero angle” and “basically zero angle,” or other similar terms, preferably mean 0 degrees ± 1 degree, but can also include 0 degrees ± 2, 3, 4, 5, or 10 degrees.

[0069] The term "imaging" as used here means measuring the light received by a sensor, and in particular, measuring the intensity of the light received by each pixel or other unit of the sensor.

[0070] The term "optical sensor" used here refers to a sensor that can measure the intensity of light received at different locations on its surface.

[0071] To avoid misunderstanding, it should be noted that the optical systems depicted in the drawings are by their nature schematic, and the relative sizes and shapes of optical elements such as lenses should not be considered as limitations on the optical elements used to carry out the present invention.

[0072] Figure 1 shows a schematic representation of a sensor 100 according to the first embodiment of the present invention.

[0073] Sensor 100 measures the displacement of the surface of the object to be measured 111 within the measuring surface 112 by measuring the light reflected from the object to be measured 111 at the intersection of the surface of the object to be measured 111 and the measuring surface 112. To avoid misunderstanding, it should be noted that the object to be measured 111 is not part of the sensor of this invention. The measuring surface will be illustrated and described in more detail with reference to Figure 1A.

[0074] The sensor 100 includes a light source 101, such as a laser or light-emitting diode, but any suitable light source can be used. Preferably, the spectral bandwidth of the light source is limited such that the range of angles of diffraction of light from the diffraction grating 106, which will be described in more detail below, is equal to or smaller than the range of angles from which the third intermediate optical system 108 can accept light. This limitation is optional, but increases the intensity of the measurement light received by the sensor 110 at a given power output of the light source 101, resulting in a more energy-efficient sensor.

[0075] The light source emits measurement light along the projection axis 102. For example, light emitted from the light source 101 can be projected across a plane, thereby projecting a line of light onto the object to be measured 111. However, the light emitted from the light source 101 onto the object to be measured 111 can take any preferred form from which a profile can be reconstructed, such as a series of dots (i.e., dotted lines), a series of smaller lines (i.e., dashed lines), or any combination of these two, as long as the two-dimensional shape of the intersection of the object to be measured 111 and the measurement surface 112 can be reconstructed from the projected light. The principle of the present invention is also applicable to sensors that use only a single point of light.

[0076] The arrangement of the light source 101 and the measurement surface 112 is shown in more detail in Figure 1A. Figure 1A is a perspective view showing some of the same elements as in Figure 1. The light source 101 emits measurement light, which is shaped into an appropriate form by the optical element 101a and projected across the object to be measured 111. Figure 1A shows that the measurement light is projected across the entire object to be measured, but this is not mandatory, nor is it mandatory that the object to be measured occupies the entire width of the measurement light. When the measurement light is incident on the object to be measured 111, it is reflected from the object to be measured 111 and appears as a line on the object to be measured. Theoretically, the measurement surface 112 is defined by the overlap between the focal plane of the intermediate image plane 105 (shown in Figure 1) via the first intermediate optical system 103a, the focal plane of the intermediate image plane 105 via the second intermediate optical system 103b, and the surface onto which the measurement light is projected. In practice, the light is projected not as an idealized two-dimensional plane, but as a three-dimensional volume with a small depth. The measurement surface 112 is therefore defined as the overlap between this three-dimensional volume onto which the measurement light is projected and the focal plane of the intermediate image plane 105 via the first intermediate optical system 103a and the focal plane of the intermediate image plane 105 via the second intermediate optical system 103b. When light is reflected from the surface of the object to be measured 111 within the measurement surface 112, the reflected light is measured to ultimately determine the displacement of the surface of the object to be measured 111 relative to the light source, or, if the object to be measured is a transparent film, to determine the thickness of the object to be measured 111.

[0077] Returning to Figure 1, the projection axis 102 is defined by the idealized direction along which light is emitted from the light source 101. The light projected by the light source 101 onto the surface of the object to be measured 111 is reflected from the surface of the object to be measured 111 in multiple directions, either specularly or non-specularly, i.e., reflected by diffuse reflection, also called non-specular reflection or scattering. A portion of the reflected light enters the first intermediate optical system 103a, which is located on the first measurement axis 104a. The first measurement axis 104a is offset from the projection axis 102 by a triangulation angle 113a. The first intermediate optical system 103a is configured to focus the projected measurement light reflected from the surface of the object to be measured 111 onto the intermediate image plane 105. According to the Scheimpflug principle, the measuring surface 112 is offset from the lens angle of the first intermediate optical system 103a by an angle corresponding to the first triangulation angle 113a. Therefore, the image plane of the measuring surface formed by the first intermediate optical system 103, i.e., the intermediate image plane 105, is also offset from the lens plane of the first intermediate optical system. Consequently, the magnitude of the angular offset of the intermediate image 105 with respect to the first measuring axis 104a depends on the first triangulation angle 113a and the magnification of the first intermediate optical system 103a.

[0078] The first intermediate optical system 103a consists of a first subset 121a of the first intermediate optical system, a first specular reflector 122a, and a second subset 123a of the first intermediate optical system. A portion of the measurement light reflected from the surface of the object to be measured 111 enters the first subset 121a of the first intermediate optical system, is reflected by the specular reflector 122a, and then enters the second subset 123a of the first intermediate optical system. The light exiting from the second subset 123a of the first intermediate optical system is incident on the diffraction grating 106.

[0079] If an image sensor were simply placed on the intermediate image plane 105 to measure light reflected from the object to be measured 111, the light incident on the image sensor would be received at the intermediate image plane angle 114. However, image sensors such as CCDs and APSs are generally not designed to operate at oblique angles, resulting in reduced performance. Even simpler optical sensors, such as those in position detection devices, experience reduced performance as the incident angle increases. The incident angle 114a of light on the intermediate image plane 105 can be reduced by increasing the triangulation angle, but this strategy is limited by the physical constraints of the system. For example, the first intermediate optical system 103a and the intermediate image plane 105 occupy the same space as the object to be measured 111, making it impossible to increase the triangulation angle to 90 degrees. Furthermore, increasing the triangulation angle has the undesirable side effect of increasing the shadow of reflected light along the first measurement axis 104a due to the change in height on the surface profile of the object to be measured in the direction perpendicular to the measurement plane. The larger the triangulation angle, the smaller the change in height that produces a shadow. Furthermore, image magnification causes further rotation of the intermediate image plane, further increasing the angle of incidence of light to the image sensor or other light sensor when positioned on the intermediate image plane, and otherwise essentially hinders the use of magnification, which could be useful for improving the accuracy of the sensor.

[0080] The sensor of the present invention solves these problems by changing the propagation angle of light relative to the image plane 105 using one or more diffraction gratings, thereby enabling the use of the optical sensor at a smaller angle and thereby improving its performance.

[0081] In the embodiment shown in Figure 1, the diffraction grating 106 is aligned with the intermediate image plane 105 such that the measurement light reflected from the surface of the object to be measured 111 focuses onto the surface of the diffraction grating 106 and is incident upon it; that is, the surface of the diffraction grating 106 is aligned with the intermediate image plane 105. In some embodiments, the diffraction grating 106 is a planar diffraction grating. In other embodiments, the diffraction grating 106 may have a slight curvature to account for the deformation of the image plane 105 due to the non-ideal characteristics of the first intermediate optical system 103. In the embodiment of Figure 1, the diffraction grating 106 is a reflection diffraction grating, but it is understood that a transmission diffraction grating may be used instead.

[0082] A diffraction grating having grooves or a slit pitch d (also called groove or slit distance) is given by the diffraction grating formula: d(sinθ i -sinθ m According to ) = ±mλ, the angle θ i The incident light of wavelength λ is diffracted at a diffraction angle θ m Diffraction is performed, where m is the number of modes m ∈ N = {0, 1, 2, 3, ...}. Incident angle θ i and diffraction angle θ m It is defined in the opposite direction to a plane (also called the grating normal) that is parallel to the grooves or slits of the diffraction grating and extends perpendicularly to the plane of the diffraction grating.

[0083] A diffraction grating with 1800 lines / mm and the angle of incidence θ for light of different wavelengths λ within the blue region of visible wavelengths. i Table 1 provides exemplary values ​​for the diffraction angle θ1 in the m=1 mode. As can be seen, when the incident angle is 54 degrees, that is, when the triangulation angle 113 and the intermediate image plane angle 114 are 36 degrees (assuming the first intermediate optical system 103 has a magnification of 1), light with a wavelength of approximately 450 nm has a diffraction angle close to zero. Such a large angle has a significant impact on the performance of the light sensor when it is placed on the intermediate image plane 105. [Table 1]

[0084] Figure 1B shows in more detail the diffraction of light reflected from the surface of the object being measured 111. Angle 141 is the maximum half-angle of light from the measurement surface that exits the first intermediate optical system 103a and focuses on the surface of the diffraction grating 106. Angle 142 is the difference between the first measurement axis 104 and the third measurement axis 107. Arrows 143a and 143b indicate the minimum and maximum diffraction angles for the measurement light of the first wavelength. Angle 144a and 144b indicate the minimum and maximum diffraction angles for the measurement light of the second wavelength. For example, if the half-angle 141 is 20 degrees and the angle 142 between the first and second measurement axes is 60 degrees, then the diffraction angle in the first diffraction mode (i.e., m=1) of 400 nm light from an 1800 lines / mm diffraction grating is -15.4 degrees along arrow 143a, i.e., at an incident angle of 40 degrees, and 4.4 degrees along arrow 143b, i.e., at an incident angle of 80 degrees. For 500 nm light, the diffraction angle in the first diffraction mode (m=1) from the same diffraction grating over the same input angle range is -4.9 degrees along arrow 144a (at an incident angle of 40 degrees) and 14.9 degrees along arrow 144b (at an incident angle of 80 degrees). Therefore, in this example, if the third intermediate optical system 108 has an input cone half-angle 145 of 15.4 degrees, all light that focuses on the diffraction grating between 400 nm and 500 nm will enter the third intermediate optical system 108 and ultimately be incident on the photosensor 110. Thus, it can be seen that limiting the spectral bandwidth of the light source 101 to the wavelengths diffracted from the diffraction grating by the angle within the input cone of the third intermediate optical system 108 leads to improved device efficiency because the maximum amount of measurement light emitted from the light source is incident on the photosensor 110. However, it should be understood that this is not an essential feature of the present invention, and broader or narrower spectral wavelengths may be used with the sensor of the present invention.

[0085] Furthermore, a non-spectral reflector may be used instead of the diffraction grating 106 in the intermediate image plane 105. However, the use of a properly aligned and configured diffraction grating increases the intensity of light propagating along the second measurement axis compared to a non-spectral reflector, such as a flat diffuse reflector.

[0086] Returning to Figure 1, a second measuring axis 104b extends from the opposite side of the measuring surface 112, and the second intermediate optical system 103b is positioned along the second measuring axis 104b, as described above with respect to the first intermediate optical system 103a and the first measuring axis 104a. Similar to the first intermediate optical system 103a, the second intermediate optical system 103b is configured to focus the light reflected from the measuring surface 112 onto the intermediate image plane 105, i.e., onto the surface of the diffraction grating 106. The above description of the configuration of the first intermediate optical system 103a and its elements along the first measuring axis 104a applies equally to the configuration of the second intermediate optical system 103b and its elements along the second measuring axis 104b.

[0087] Although the configuration shown in Figure 1 is presented as mirror symmetry, it is not essential that the first intermediate optical system 103a and the second intermediate optical system 103b have such symmetry. By arranging the first intermediate optical system 103a and the second intermediate optical system 103b mirror symmetry, the structure and manufacturing of the sensor are simplified, but the only necessary constraint is that the image planes of the measurement surface, which are focused by the measurement light received from the measurement surface 112, through the first intermediate optical system 103a and the second intermediate optical system 103b, are coplanar with each other and with the surface of the diffraction grating 106. In fact, it may be advantageous to adopt an asymmetric configuration, i.e., a configuration in which the first triangulation angle 113a is different from that of the second triangulation angle 113b. This can be achieved by changing the magnification of the first subset 121b of the second intermediate optical system 103b and the second subset 123b of the second intermediate optical system 103b in comparison to the magnification of the corresponding subset in the first intermediate optical system 103a.

[0088] Light focused onto the diffraction grating 106 by the first intermediate optical system 103a can be incident on the first portion of the diffraction grating, and light focused onto the diffraction grating 106 by the second intermediate optical system 103b can be incident on the second portion of the diffraction grating. The first and second portions of the diffraction grating 106 do not overlap, which allows the images of the measurement surface formed on the diffraction grating from each side of the measurement surface to be easily distinguishable.

[0089] It should be understood that, while a single diffraction grating 106 is referred to here, as depicted in Figure 1, the function of the diffraction grating 106 may be performed by two separate diffraction gratings aligned with the intermediate image plane 105 if the light focused by the first intermediate optical system 103a and the second intermediate optical system 103b is incident on different parts of the diffraction grating.

[0090] When multiple diffraction gratings are used instead of a single diffraction grating 106, each diffraction grating may have a different pitch, thereby changing the diffraction angle of light incident at a given angle. Thus, different triangulation angles 113b or different magnifications can be used in the second intermediate optical system 103b, while still allowing the light diffracted from the two gratings to propagate essentially parallel to each other, and thus enabling focusing on the light sensor 110 when a single light sensor 110 is used.

[0091] As described above with respect to Figure 1B, the measurement light diffracted by the diffraction grating 106 enters the third intermediate optical system 108 located on the third measurement axis 107. The third measurement axis 107 is preferably basically perpendicular to the surface of the diffraction grating 106, i.e., basically parallel to the grating normal. In this context, “basically parallel” means within 5 degrees of perpendicular. Similarly, “basically coaxial” means within 5 degrees of parallel. When the third measurement axis 107 is basically perpendicular to the surface of the diffraction grating, as described above, the performance of the photosensor 110 is improved so that the light diffracted from the diffraction grating from both the first side of the measurement surface (i.e., along the first measurement axis 104a) and the second side of the measurement surface (i.e., along the second measurement axis 104b) can be focused across the photosensor 110.

[0092] A third intermediate optical system 108 is configured to focus the diffracted light from the diffraction grating 106 onto the sensor image plane 109. The image of the light projected onto the object to be measured 111 is focused on the intermediate image plane 105, that is, on the diffraction grating 106. Therefore, according to Scheinproof's principle, when the magnification of the third intermediate optical system is 1, the angle of the sensor image plane 109 with respect to the third measurement axis 107 is the same as the angle of the intermediate image plane 105 with respect to the third measurement axis 107.

[0093] The optical sensor 110 is positioned so that its active surface is aligned with the sensor image plane 109, and the diffracted measurement light is focused across the optical sensor 110.

[0094] When light reflected from the first side of the measuring surface 112 and reaching the diffraction grating 106 via the first intermediate optical system 103a is incident on the first portion of the diffraction grating, and when light reflected from the second side of the measuring surface 112 and reaching the diffraction grating 106 via the second intermediate optical system 103b is incident on the second portion of the diffraction grating, the light reflected from each side of the measuring surface 112 ultimately incident on the photosensor 110 in the first and second portions as well. Therefore, the photosensor 110 may also be replaced by two separate photosensors corresponding to the first and second portions. However, the use of a single photosensor, as with the use of a single diffraction grating, greatly simplifies the construction and calibration of the sensor 100.

[0095] The light sensor may be, for example, an image sensor such as a CCD (charge-coupled device) or APS (active pixel sensor), a position detection device, or any suitable sensor capable of measuring the intensity of light received at different positions on its surface.

[0096] If the third measurement axis 107 is essentially parallel to the grid normal, any magnification can be used in the second intermediate optical system 108 without changing the angle of the sensor image plane 109. The magnification can enable more accurate measurement of the shape of the light projected onto the object to be measured 111. Furthermore, since the performance of the light sensor 110 is no longer constrained by the triangulation angles 113a / 113b, smaller triangulation angles 113a / 113b can be used, enabling the sensor 100 to measure the shape of the object to be measured 111 having surface features with a higher aspect ratio without shadowing.

[0097] Furthermore, diffraction modes other than the m=1 mode can be used. The m=-1 mode provides the same diffracted light intensity as the m=1 mode and can therefore be used with the same preference as the m=1 mode. Light diffracted in modes higher than m=±1 has a lower intensity but can still be used as described above and is still preferable to use a simple diffuse reflector instead of a diffraction grating. To maximize the intensity of the diffracted light, a blaze diffraction grating may be used, in which case the light source 101 can be a monochromatic or narrowband light source having a center wavelength equal to the blaze wavelength of the diffraction grating.

[0098] Furthermore, the diffraction grating 106 may be curved. In practice, the image plane 105 may be slightly curved due to the non-ideal characteristics of the first intermediate optical system 103, especially when low-quality lenses are used. The curvature of the diffraction grating 106 is preferably the same as the curvature of the image plane 105, such that the light received from the measuring surface 112 is in focus at every point on the diffraction grating 106 from which it is incident.

[0099] In the simplest example, where a single point of light is projected onto the surface of the object to be measured 111, the measurement light received from each side of the measurement surface 112 is incident on the photosensor 110. The position of the maximum light intensity on the photosensor 110 for the light from each side of the measurement surface corresponds to the displacement of the illumination point on the surface of the object to be measured 111 relative to the sensor 100. If other light sources are used, such as a series of points, the position of the maximum light intensity corresponds to the displacement of each illumination point on the surface of the object to be measured 111 relative to the sensor. If lines of light are used, the maximum intensity at each pixel in each column or row corresponds to the displacement of the illumination area on the surface of the object to be measured 111 relative to the sensor 100.

[0100] Figure 2 shows a sensor 200 according to a second embodiment of the present invention. Similar to sensor 100, sensor 200 uses a diffraction grating 206 to enable an incident angle of light of virtually zero on the optical sensor 210. However, unlike the triangulation sensor 100 described above, sensor 200 is a coaxial sensor, that is, the first measurement axis 204 is coaxial with the projection axis 202, or in other words, the first measurement axis 204 is located within the measurement surface 212.

[0101] Sensor 200 includes a light source 201 as described above with respect to sensor 100. The light source 201 may include one or more optical elements, either integrally as part of the light source 201, or arranged along an axis along the projection axis 202 in the path of light emitted from the light source 201. Measurement light can be projected onto the measurement object 211 such that a line of light is projected onto the measurement object 211. However, the light emitted from the light source 201 within the measurement surface 212 on the measurement object 211 can take any preferred form of light as described above with respect to sensor 100. The spectral bandwidth of the light source 201 in Figure 2, and the spectral bandwidth of other coaxial embodiments described later, may be limited based on the half-angle of the cone of light entering the second intermediate optical system, as described above with respect to Figure 1B.

[0102] A reflector 201a may be provided to position the light source 201 away from the first measurement axis 204. The reflector 201a may be positioned within the first intermediate optical system 203, as shown in Figure 2, in which case the lens of the first intermediate optical system 203 positioned between the reflector 201a and the object to be measured 211 may have an aperture that allows light from the light source 201 to pass through without being refracted by the lens. Alternatively, the lens may not have an aperture and instead be shaped to form the light projected onto the measurement surface, as shown in Figure 2. As a further alternative, the reflector 201b may be positioned outside the first intermediate optical system 203, for example, between the first intermediate optical system 203 and the object to be measured 211, as shown in Figures 3 and 4. The position and orientation of the light source 201 and the reflector 201b can be arbitrarily selected, as long as the measurement light is still projected onto the measurement surface 212. Since the reflector 201b can be much smaller in size than the light source 201, it can be positioned almost entirely within the blind spot of the sensor 200, which is aligned with the measuring surface 212 and the projection axis 202.

[0103] The measurement light projected onto the object to be measured 211 within the measurement surface 212 is scattered (i.e., diffusely reflected) from the surface of the object to be measured. At least a portion of the reflected light is reflected back toward the sensor 200, and in particular toward the first intermediate optical system 203. The first intermediate optical system 203 is located on the first measurement axis 204, which is aligned with the measurement surface.

[0104] The measurement light entering the first measurement optical system 203 is focused onto an intermediate image plane 205, which is aligned with the measurement surface 212. When the measurement light is reflected from the object to be measured 211 at different heights within the measurement surface, i.e., at points closer to or further from the first intermediate optical system 203, the corresponding position of the focused light within the intermediate image plane 205 changes accordingly. The light is focused onto the intermediate image plane 210 from both sides of the plane.

[0105] The diffraction grating 206 is aligned with the intermediate image plane 205 such that the focused image of the projected light is incident on the planar surface of the diffraction grating 206; that is, the planar surface of the diffraction grating 206 is aligned with the intermediate image plane 205. The measurement light reflected from the object to be measured 211 and diffracted by the diffraction grating 206 is diffracted along a second measurement axis 207 that is basically perpendicular to the intermediate image plane 205.

[0106] The diffraction grating 206 can be a reflection diffraction grating, a transmission diffraction grating, or it may be capable of operating in both reflection and transmission modes. For example, a diffraction grating capable of operating in both reflection and transmission modes is a Ronchi ruler. A diffraction grating capable of operating in both reflection and transmission modes must be sufficiently thin so that the light incident on both sides of the grating does not deviate significantly from the focal point, and so that the light diffracted in transmission mode does not align with the light transmitted in reflection mode. The diffraction grating can therefore have a thickness of 500 μm or less.

[0107] The second intermediate optical system 208 is positioned along the second measurement axis 207 and configured to focus the diffracted light from the diffraction grating 206 onto the sensor image plane 209. The image of the light projected onto the object to be measured 211 is focused onto the intermediate image plane 205, i.e., onto the diffraction grating 206, so the angle of the sensor image plane 209 with respect to the second measurement axis 207 is the same as the angle of the intermediate image plane 205 with respect to the second measurement axis 207. The light sensor 210 is positioned so that its surface is aligned with the sensor image plane 209 and the image of the light projected onto the object to be measured 211 is focused across the active surface of the light sensor 210. Therefore, the angle of incidence of light onto the light sensor 210 is equal to the diffraction angle of the light from the diffraction grating 206, i.e., the light sensor 210 is positioned basically perpendicular to the direction of the incident light. In this case as well, an incident angle of basically zero for the measurement light onto the light sensor 210 is optimal. However, as explained above, any reduction in the incident angle of light onto the light sensor 210 compared to the incident angle of light onto the diffraction grating 206 will result in an improvement in the performance of the sensor 200.

[0108] If the diffraction grating can operate in both reflection and transmission modes, the sensor may also include a third intermediate optical system positioned along a third measurement axis 207b, configured to focus diffracted light from a second side of the diffraction grating 206 onto a second sensor image plane 209b. In the same manner as described above for the photosensor 210, the second photosensor 210b is positioned such that its surface is aligned with the second sensor image plane 209b and the image of light projected onto the object to be measured 211 is in focus across the active surface of the second photosensor 210b. The third intermediate optical system 208b and the second photosensor operate in the same manner as the second intermediate optical system 208 and the photosensor 210, although they are mirror-symmetric with respect to the intermediate image plane 205.

[0109] Alternatively, the diffraction grating 206 may be a reflective diffraction grating that diffracts light incident on the intermediate image plane 205 from a first side, and a second reflective diffraction grating may be aligned parallel to the diffraction grating 206 to diffract light incident on the intermediate image plane 205 from a second side. In this case, the sensor may also include a third intermediate optical system positioned along a third measurement axis, configured to focus diffracted light from the second side of the diffraction grating 206 onto the second sensor image plane and the second photosensor, as described above with respect to diffraction gratings that can operate in both transmission and reflection modes. The third measurement axis extends from the intermediate image plane 205 coaxially with the second measurement axis 207, i.e., perpendicular to the intermediate image plane 205, and the third intermediate optical system and the second photosensor operate in the same manner as the second intermediate optical system 208 and the photosensor 210, although they are mirror symmetric with respect to the intermediate image plane 205.

[0110] It should be understood that the third intermediate optical system 208b and other elements, positioned along the third measurement axis 207b, are optional mechanisms and are not required for the basic function of the sensor 200.

[0111] Figure 3 is a schematic diagram of a sensor 300 according to a third embodiment of the present invention. Similar to sensors 100 and 200, sensor 300 uses diffraction gratings 306a and 306b to enable a virtually zero incidence angle of measurement light onto the optical sensor 310. Similar to sensor 200, sensor 300 is a coaxial sensor, that is, the first measurement axis 304 is coaxial with the projection axis 302, or in other words, the first measurement axis 304 lies within the measurement surface 312.

[0112] Sensor 300 includes a light source 301, which may be the same as that described above with respect to Figures 1, 1A, and 2. The light source 301 may include one or more optical elements, either integrally as part of the light source 301, or arranged along an axis along the projection axis 302 in the path of light emitted from the light source 301, in order to shape the light projected onto the object to be measured 311. The light emitted from the light source 301 may be emitted into the measuring surface 312, traversing the entire measuring surface 312, resulting in a line of light projected onto the object to be measured 311. However, the light emitted from the light source 301 within the measuring surface 312 onto the object to be measured 311 can take any preferred form of light, as described above with respect to sensors 100 and 200. Furthermore, as described above with respect to sensor 200, a reflector 301a may be provided to position the light source 301 away from the first measuring axis 304. The possible positions and orientations of the reflector 301a relative to the first intermediate optical system 303 are the same as those described above with respect to the reflector 201b of the sensor 200 and the first intermediate optical system 203.

[0113] The measurement light projected onto the object to be measured 311 within the measurement surface 312 is scattered (i.e., diffusely reflected) from the surface of the object to be measured. A portion of the reflected light is reflected towards the sensor 300, and in particular towards the first intermediate optical system 303. The first intermediate optical system 303 is located on the first measurement axis 304, which is aligned with the measurement surface.

[0114] The first intermediate optical system 303 also includes a specular reflector 303b, which is aligned with the measuring surface 312 such that measurement light that enters the first intermediate optical system after being reflected from the first side of the measuring surface 312 is reflected by the first side of the specular reflector 303b, and measurement light that enters the first intermediate optical system after being reflected from the second side of the measuring surface 312 is reflected by the second side of the specular reflector 303b. As shown in Figure 3, the specular reflector 303b may have a triangular prism shape, with one vertex of the triangular cross-section aligned with the measuring surface 312 and the first measuring axis 304. However, it is understood that multiple specular reflectors 303b may be used instead, for example, a separate reflector may be provided for measurement light from each side of the measuring surface 312. Therefore, one or more reflectors 303b are configured to reflect the measurement light reflected from the first side of the measurement surface 312 in a first direction, and to reflect the measurement light reflected from the second side of the measurement surface 312 in a second direction.

[0115] Therefore, the measurement light received by the sensor is divided into a "first side" and a "second side" based on the side of the measurement surface 312 from which it is reflected from the surface of the object to be measured 311. On the first side, the measurement light that enters the first measurement optical system 303, 303a after being reflected from the object to be measured 311 on the first side of the measurement surface is focused onto the first intermediate image plane 305a. On the second side, the measurement light that enters the first measurement optical system 303, 303a after being reflected from the object to be measured 311 on the second side of the measurement surface is focused onto the second intermediate image plane 305b.

[0116] On the first side, the first diffraction grating 306a is aligned with the first intermediate image plane 305a such that the focused image of the projected light is incident on the planar surface of the first diffraction grating 306a; that is, the planar surface of the first diffraction grating 306a is aligned with the first intermediate image plane 305a. The measurement light reflected from the object to be measured 311 and diffracted by the first diffraction grating 306a is diffracted along a second measurement axis 307a that is basically perpendicular to the first intermediate image plane 305a. On the second side, the second diffraction grating 306b is aligned with the second intermediate image plane 305b such that the focused image of the projected light is incident on the planar surface of the second diffraction grating 306b; that is, the planar surface of the second diffraction grating 306b is aligned with the second intermediate image plane 305b. The measurement light reflected from the object to be measured 311 and diffracted by the second diffraction grating 306b is diffracted along a third measurement axis 307b that is essentially perpendicular to the second intermediate image plane 305b. The first and second diffraction gratings 306a and 306b are preferably reflection diffraction gratings.

[0117] The second intermediate optical system 308 is positioned along the second measurement axes 307a and 307b and combines the measurement light diffracted from the first diffraction grating 306a and the measurement light diffracted from the second diffraction grating 306b within the coupled measurement axis 307, while focusing the diffracted light onto the sensor image plane 309. Thus, the second intermediate optical system 308 may include one or more reflectors and beam combiners, as shown in Figure 3. Preferably, the optical path length between the object to be measured 311 and the sensor image plane 309 on the first side is equal to the optical path length between the object to be measured 311 and the sensor image plane 309 on the second side, so that the light received from each side at any given time on the sensor 310 aligned with the sensor image plane 309 corresponds to the same position on the surface of the object to be measured 311. Different path lengths may be used, but this can complicate calculations because the light received simultaneously from each side will not correspond to exactly the same measurement point on the object to be measured 311. Within these limits, any preferred configuration of the second intermediate optical systems 308, 308b may be used in conjunction with the present invention. In practice, for this reason as well, the arrangement of the first intermediate optical systems 303, 303a and the first and second diffraction gratings 306a, 306b is preferably symmetrical with respect to the measuring surface 312. Furthermore, the first and second diffraction gratings can have the same groove pitch such that the diffraction angles of each grating are the same, in which case both gratings 306a, 306b may use the same order of diffraction mode, or one may use the m=1 diffraction mode and the other the m=-1 diffraction mode, for example, both may use the m=1 diffraction mode or both may use the m=-1 diffraction mode.

[0118] In the sensor 300 shown in Figure 3, the first diffraction grating 306a and the second diffraction grating 306b are aligned so that their planar diffraction surfaces are perpendicular to the measuring surface 312 and parallel to each other, in order to enable the use of 90-degree reflection within the second intermediate optical system 308a. However, it should be understood that other angles and configurations may be used, as long as the optical path length remains the same, as shown in Figure 4, for example.

[0119] The optical sensor 310 is positioned such that its surface is aligned with the sensor image plane 309 and the diffracted measurement light is focused on the optical sensor 310. As with sensors 100 and 200, the average angle of incidence of light onto the optical sensor 310 is smaller than the average angle of incidence of measurement light onto the diffraction grating 106. Preferably, the normal vector of the optical sensor, which is defined as a vector extending perpendicularly from the planar surface of the optical sensor, is aligned with the angle of incidence of light incident on the optical sensor 310.

[0120] Preferably, light diffracted from the first diffraction grating 306a is incident on the first portion of the photosensor 310, and light diffracted from the second diffraction grating 306b is incident on the second portion of the photosensor 310. Preferably, the first and second portions of the photosensor do not overlap, and each can be, for example, half of the surface of the photosensor 310. This arrangement is naturally achieved in the configuration shown in Figure 3. As a result, the measurement light received from each side of the measurement surface 312 can be easily distinguished in the output signal of the photosensor 310. Alternatively, the photosensor 310 may be replaced by two separate photosensors, each of which is sized and positioned so that light diffracted from the corresponding diffraction grating is incident on it.

[0121] Figure 4 is a schematic diagram of a sensor 400 according to a fourth embodiment of the present invention. The embodiment in Figure 4 corresponds to the embodiment in Figure 3, which has a second intermediate optical system 408, 408a with a different configuration. Instead of the reflector and beam combiner configuration shown in Figure 3, a single beam combiner 408a is used. To enable this configuration, the angles of the reflector 403a of the first intermediate optical system, as well as the angles of the first diffraction grating 406a and the second diffraction grating 406b, are adjusted in comparison to the corresponding components of the sensor 300. Similar to the sensor 300, the second intermediate optical system combines the measurement light diffracted from each diffraction grating and focuses the measurement light onto the photosensor 410 in the sensor image plane 409, where the shape can be measured to determine the profile of the object to be measured.

[0122] All of the sensors described above can be used as 3D sensors to measure the three-dimensional shape of an object. A 3D model of the object can be constructed by imaging the measurement light projected onto the object at multiple locations on the object. In practice, displacement measurements are performed repeatedly or continuously as the object moves across the measurement surface, which 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 as measuring the profile of a cross-sectional slice of the object, and the 3D shape of the object can be reconstructed from these profile measurements by combining them with the known displacement between each measurement.

[0123] The sensor can also be used for multilayer measurements, such as measuring the thickness of a transparent film. The reflection of measurement light from the surface of each layer of the transparent film generates distinguishable intensity peaks, and if the refractive index of the layer is known, the thickness can be calculated based on the distance between two sequential peaks.

[0124] Furthermore, if the optical sensor is an image sensor such as a CCD or APS, the optical sensor can simultaneously capture a conventional 2D image of the surface of the object being measured while also measuring the displacement as described above.

Claims

1. A sensor for measuring the displacement of the surface of an object to be measured, wherein the displacement is relative to the sensor, A light source (101) configured to project measurement light into the measuring surface (112), wherein when the sensor is used, the light source is configured such that the measurement light is reflected from the surface of the object to be measured at the intersection of the measuring surface and the surface of the object to be measured, A first intermediate optical system (103a) is positioned along the first measurement axis (104a) and configured to focus the measurement light reflected from the first side of the measurement surface onto the intermediate image plane (105), The at least one diffraction grating (106) is aligned with the intermediate image plane, and the reflected measurement light is incident on the surface of the diffraction grating so as to focus, and the measurement light is diffracted along the second measurement axis (107), A second intermediate optical system (108) is positioned along the second measurement axis and configured to focus the diffracted measurement light onto the sensor image plane (109), The optical sensor (110) is aligned with the sensor image plane, and the diffracted measurement light is configured to focus on the optical sensor, and the optical sensor is configured to measure the diffracted measurement light incident on the optical sensor. A sensor having

2. The sensor according to claim 1, wherein the measuring surface (112) is defined by the intersection of the focal plane of the intermediate image plane (105) via the first intermediate optical system (103a) and a volume onto which measuring light is projected along the projection axis (102).

3. The sensor according to claim 1, further comprising a third intermediate optical system (103b) positioned along a third measurement axis and configured to focus the measurement light reflected from the second side of the measurement surface onto the intermediate image plane.

4. The sensor according to claim 3, wherein the focal plane of the intermediate image plane (105) via the third intermediate optical system (103b) is coplanar and overlaps with the focal plane of the intermediate image plane via the first intermediate optical system (103a).

5. The sensor according to claim 3, wherein the measurement light reflected from the first side of the measurement surface (112) is incident on the first portion of the diffraction grating (106), and the measurement light reflected from the second side of the measurement surface is incident on the second portion of the diffraction grating.

6. The sensor according to claim 5, wherein light diffracted from the first portion of the diffraction grating (106) is focused on the first portion of the photosensor (110), and light diffracted from the second portion of the diffraction grating is focused on the second portion of the photosensor.

7. The sensor according to claim 3, wherein the first measuring axis is offset from the projection axis by a first triangulation angle (113a), and the third measuring axis is offset from the projection axis by a second triangulation angle (113b).

8. The first intermediate optical system (103a) comprises a first subset (121a), a first specular reflector (122a), and a second subset (123a), wherein the measurement light reflected from the first side of the measurement surface (112) enters the first subset of the first intermediate optical system, exits the first subset of the first intermediate optical system, is reflected by the first specular reflector at a first reflection angle (115a), enters the second subset of the first intermediate optical system, and exits the second subset of the first intermediate optical system, so that the measurement light is focused on the intermediate image plane (105). The third intermediate optical system (103b) comprises a first subset (121b), a second specular reflector (122b), and a second subset (123b), wherein the measurement light reflected on the second side of the measurement surface enters the first subset of the third intermediate optical system, exits the first subset of the third intermediate optical system, is reflected by the second specular reflector at a second reflection angle (115b), enters the second subset of the third intermediate optical system, and exits the second subset of the third intermediate optical system, so that the measurement light is focused on the intermediate image plane. The sensor according to claim 3.

9. The sensor according to claim 3, wherein the first intermediate optical system (103a) and the third intermediate optical system (103b) are arranged mirror-symmetrically with respect to the measuring surface (112).

10. A sensor (200) for measuring the displacement of the surface of an object to be measured, wherein the displacement is relative to the sensor, A light source (201) configured to project measurement light into a measuring surface (212) along a projection axis (202), wherein when the sensor is used, the light source is configured such that the measurement light is reflected from the surface of the object to be measured at the intersection of the measuring surface and the surface of the object to be measured, A first intermediate optical system (203) is positioned along a first measurement axis (204) and configured to focus the measurement light reflected from the measurement surface onto an intermediate image plane (205), wherein the first measurement axis is coaxial with the projection axis. A diffraction grating (206) aligned with the intermediate image plane, wherein the reflected measurement light is incident on the surface of the diffraction grating in focus, and the measurement light is diffracted along a second measurement axis (207a), A second intermediate optical system (208a) is positioned along the second measurement axis and configured to focus the diffracted measurement light onto the sensor image plane (209a), The optical sensor (210a) is aligned with the sensor image plane, and the diffracted measurement light is configured to focus on the optical sensor, and the optical sensor is configured to measure the diffracted measurement light incident on the optical sensor. A sensor having

11. The sensor according to claim 10, wherein the diffraction angle of each ray of the measurement light from the diffraction grating is smaller than the incidence angle of each ray of the measurement light to the diffraction grating.

12. The sensor according to claim 10, wherein the diffraction grating (206) is coplanar with the measuring surface (212).

13. The sensor according to claim 12, wherein the diffraction grating (206) operates in both reflection mode and transmission mode.

14. The sensor according to claim 13, wherein the thickness of the diffraction grating (206) is less than 500 μm.

15. The diffraction grating (206) is further configured to diffract the measurement light along a third measurement axis (207b), the third measurement axis being coaxial with the second measurement axis (207a) and extending from the opposite side of the diffraction grating, and the sensor further A third intermediate optical system (208b) is positioned along the third measurement axis and configured to focus the diffracted measurement light onto the second sensor image plane (209b), A second photosensor (210b) is aligned with the second sensor image plane, and the diffracted measurement light is focused on the second photosensor, and the second photosensor is configured to measure the diffracted measurement light incident on the second photosensor, The sensor according to claim 10, having the following features.

16. The sensor further, A second diffraction grating (306b, 406b) is positioned so as to be mirror-symmetric with respect to the measurement surface to the first diffraction grating (306a, 406a), At least one reflector (303a, 403a) is configured to reflect measurement light from the first side of the measurement surface (312, 412) onto the first diffraction grating, and to reflect measurement light from the second side of the measurement surface onto the second diffraction grating, It has, The second intermediate optical system is configured to focus the light diffracted from the first diffraction grating and the light diffracted from the second diffraction grating onto the sensor image plane. The sensor according to claim 10.

17. The sensor according to claim 16, wherein the optical path length between the measuring surface (312, 412) and the optical sensor (310, 410) for measurement light from the first side of the measuring surface is the same as the optical path length between the measuring surface and the optical sensor for measurement light from the second side of the measuring surface.

18. The sensor according to claim 16, wherein the second intermediate optical system (308, 408) further includes a beam combiner for coupling the measurement light from the first side of the measuring surface and the measurement light from the second side of the measuring surface so that the measurement light from both sides of the measuring surface is incident on the light sensor.

19. The sensor according to claim 1 or 10, wherein the diffraction grating is a curved diffraction grating, and the curvature of the diffraction grating is the same as the curvature of the intermediate image plane.

20. The sensor according to claim 1 or 10, wherein the sensor is configured to identify a plurality of local maximum light intensity points on the light sensor, each of which corresponds to the reflection of measurement light from the transparent layer of the object to be measured, and to calculate the distance to each transparent layer of the object to be measured based on the location of the local maximum light intensity points.

Images