Surface shape measuring device

Abstract

To provide a high-resolution surface topography measuring device capable of measuring carcinoma in situ. [Solution] The light source unit generates a first light and a second light. The first light reflected from the object to be measured interferes with the second light and is detected by a photodetector. The first light irradiated onto the object to be measured is divided into multiple light beams by a structural optical system, etc., and each of the divided light beams is focused and irradiated onto the object to be measured in a line.

Description

Technical Field

[0001] The present invention relates to an apparatus for measuring the surface shape of an object.

Background Art

[0002] An interferometer capable of measuring a fine uneven shape in a non-destructive and non-invasive manner by interfering lights having a wide wavelength range such as white light is disclosed in Patent Document 1.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Since the interference system of Patent Document 1 uses an image sensor, background noise such as beams and speckles occurs. There has been a problem that background noise signals generated when the measurement target is a scattering object and background noise signals at the edge portion of the measurement target reduce the intensity of the interference light and make it difficult to acquire the shape of the measurement target.

[0005] An object of the present invention is to reduce the influence of background noise signals of a surface shape measuring apparatus and improve the detection accuracy of the surface shape.

Means for Solving the Problems

[0006] According to one aspect of the present invention, there is provided a surface shape measuring apparatus including a light source unit that forms first light and second light, and a photodetector. The photodetector includes a plurality of detection elements arranged in one dimension or two dimensions, and detects light obtained by interfering the first light irradiated to and reflected from a measurement target with the second light. The light source unit forms a plurality of light beams as the first light, condenses each of the plurality of light beams, and irradiates them in a line on the measurement target.

Effects of the Invention

[0007] According to the present invention, by focusing multiple divided light beams and arranging them in a line on the object to be measured, the influence of background noise in the surface shape measuring device can be reduced, and the detection accuracy of the surface shape can be improved. [Brief explanation of the drawing]

[0008] [Figure 1] A block diagram showing the overall configuration of the surface shape measuring device 1 of the first embodiment of the present invention. [Figure 2] A block diagram showing the configuration of the surface shape measuring device 1 according to the first embodiment. [Figure 3] In the surface shape measuring device 1 of the first embodiment, (a) an explanatory diagram showing that a light beam with a linear beam cross-section (first light 101) is irradiated onto the object to be measured 100, (b) a cross-sectional view of the object to be measured 100 in zx, (c) a perspective view of the optical path length modulator 70, (d) a diagram showing the light intensity distribution of the two-dimensional detection surface of the photodetector 80, and (e) a diagram explaining how to acquire images of the light intensity distribution of the two-dimensional detection surface of the photodetector 80 in a time series. [Figure 4] In the surface shape measuring device 1 of the first embodiment, (a) a diagram illustrating the structured optical system 300, (b) and (c) diagrams illustrating the linearly focused light beam of a comparative example and the state in which the light beam, discretized and focused by the structured optical system 300 of the first embodiment, is irradiated onto the object to be measured 100. [Figure 5] A diagram showing comb light emitted from light source 11 of a modified example of the first embodiment. [Figure 6] (a) A diagram showing the correspondence between the multiple divided luminous beams of the first light 101 in the second embodiment and the two-dimensional detection surface of the photodetector 80; (b) A diagram showing the arrangement of pixels in the divided region 60 of the two-dimensional detection surface and the pixel values; (c) A diagram showing the state in which the pixel values ​​of each pixel row 61 in region 60 are replaced with the average value of the pixel values ​​of that pixel row 61; (d) A graph plotting the position where the average value of the pixel row 61 in the y-axis direction is the maximum value as the position of the interference light. [Figure 7] A block diagram showing the overall configuration of the surface shape measuring device 1 in the embodiment. [Figure 8](a) A diagram showing the arrangement of the measurement target 100 in Example 1, (b) an image showing the detection result of the two-dimensional detection surface of the photodetector 80 in Example 1, and (c) an image showing the detection result of the two-dimensional detection surface of the photodetector 80 in the comparative example. [Figure 9] (a) is an image showing the detection results of the two-dimensional detection surface of the photodetector 80 of Example 1, and (b) is a graph plotting the pixel positions calculated by the surface shape detection unit 32 from the image in Figure 9(a). [Figure 10] (a) Image of the two-dimensional detection surface when the 100 samples of the comparative example are placed at a certain inclination angle, (b) Image of the two-dimensional detection surface when the 100 samples of the example 2 are placed at a certain inclination angle, (c) Graph plotting the error rate for each inclination angle of the sample of Example 2 relative to the optical axis. [Figure 11] (a) A photograph of the 100 sample of the measurement target with a step on its surface according to Example 3, (b) A graph showing the surface measurement results of the 100 sample of the measurement target in the comparative example, and (c) A graph showing the surface measurement results of the 100 sample of the measurement target in Example. [Modes for carrying out the invention]

[0009] One embodiment of the present invention will be explained using diagrams.

[0010] In this invention, the scattering component is suppressed and the accuracy of shape measurement is improved by structuring the irradiation light of the surface shape measuring device. Specifically, multiple light beams are formed as the first light irradiated onto the object to be measured, and the structured light obtained by focusing each of the multiple light beams is irradiated onto the object to be measured in a line. As a result, the scattering component contained in the detected light can be suppressed compared to when linear light is irradiated onto the object to be measured, and thus the detection sensitivity can be improved. Therefore, it becomes possible to measure objects and areas of objects that could not be measured accurately when linear light was irradiated.

[0011] <<First Embodiment>> The surface shape measuring device 1 of the first embodiment will be described below.

[0012] FIG. 1 is a diagram showing the overall configuration of the surface shape measurement device 1, and FIG. 2 is a diagram showing the configuration of the interference system 10. FIGS. 3(a) to (e) are diagrams for explaining the interference system 10, and FIGS. 4(a) to (c) are diagrams for explaining the structured optical system 300.

[0013] As shown in FIG. 1, the surface shape measurement device 1 includes an interference system 10 that measures the shape of the surface of the measurement object 100, an image generation unit 31, a surface shape detection unit 32, a display unit 34, and a control unit 35.

[0014] <Interference system 10, Structured optical system 300> The configurations of the interference system 10 and the structured optical system 300 will be described with reference to FIGS. 2 to 4.

[0015] The interference system 10 includes a light source 11 that emits broadband light, an optical path length modulator 70, an optical system (21 to 28), a photodetector 80, and a structured optical system 300.

[0016] The light source 11 and the optical system (21 to 28) form a light source unit, and form a first light 101 irradiated to the measurement object 100 and a second light 102 irradiated to the optical path length modulator 70. In the present embodiment, in the interference system 10, a structured optical system 300 is arranged that divides the light beam emitted from the light source 11 to form a plurality of light beams, condenses each of the plurality of light beams, and irradiates them in a row on the measurement object 100.

[0017] However, the present embodiment is not limited to a configuration in which the light beam emitted from the light source 11 is divided by the structured optical system 300, and the light source 11 itself may be configured to emit a plurality of light beams. For example, as the light source 11, a plurality of micro light sources such as VCSEL (Vertical-Cavity Surface-Emitting Laser diode) arranged side by side can be used as an example. By using such a light source 11, it is possible to irradiate the measurement object 100 with a plurality of light beams emitted from a plurality of micro light sources arranged in a row.

[0018] The photodetector 80 has a configuration in which multiple detection elements are arranged in two dimensions, and the multiple detection elements constitute a two-dimensional detection surface. The photodetector 80 detects light that is the result of interference between the first light 101 and the second light 102 reflected from the object to be measured 100. Note that when scanning the photodetector 80 relative to the interference light, the detection elements of the photodetector 80 can be arranged in one dimension.

[0019] The light source 11 emits broadband light, such as low-coherence light like LED light, supercontinuum light, or short-pulse laser light.

[0020] The optical system (21-28) includes a mirror 21, a neutral density filter 22, a beam expander 23, a beam splitter 24, a cylindrical lens 25, and a focusing lens 26, arranged in order along the optical axis 91 between the light source 11 and the object to be measured 100. An optical path length modulator 70 is positioned on the optical axis 92, which is branched from the optical axis 91 by the beam splitter 24. Focusing lenses 27 and 28 are positioned between the beam splitter 24 and the optical path length modulator 70.

[0021] A structured optical system 300 is positioned between the focusing lens 26 and the object to be measured 100. The structured optical system 300 divides the light focused by the focusing lens 26 into multiple light beams, focuses each of the divided light beams, and illuminates the object to be measured 100 in a line. Here, as the structured optical system 300, a cylindrical array is used in which multiple cylindrical lenses are arranged in a direction perpendicular to the long axis of the cylindrical lenses, as shown in Figure 4(a).

[0022] Light emitted from the light source 11 is reflected by the mirror 21, attenuated by the neutral density filter 22, then the beam diameter is expanded by the beam expander 23, a portion of which is reflected in the direction of the optical axis 92 by the beam splitter 24, and the remaining light passes through the beam splitter 24 and travels along the optical axis 91. The light traveling along the optical axis 91 is focused in the y-axis direction by the cylindrical lens 25 and the focusing lens 26, and the cross-sectional shape of the beam is transformed into a linear beam of light that is long in the first direction (x-axis direction). This linear beam of light, as the first beam 101, is irradiated as the first beam 101 onto a linear measurement area 100a of the measurement target 100 that is parallel to the x-axis and at a predetermined position in the y-axis direction, as shown in Figure 3(a).

[0023] At this time, as shown in Figure 2, a cylindrical array is arranged as a structured optical system 300 between the focusing lens 26 and the object to be measured 100. As shown in Figures 4(a) to (c), the structured optical system 300 divides the first light 101 irradiated onto the object to be measured 100 into multiple light beams in a first direction (x-axis direction), focuses each divided light beam, and irradiates the object to be measured 100 in a line at predetermined intervals in the first direction (x-axis direction). As a result, multiple light beams of the first light 101, discretized in the x-axis direction, irradiate the object to be measured 100.

[0024] Multiple beams of light from the first light 101 irradiated onto the measurement area 100a of the object to be measured 100 are reflected by the surface of the irradiated measurement area 100a.

[0025] As schematically shown in Figures 3(b) and 4(c) of the cross-sectional view of the zx plane, the position (depth) in the z-axis direction of the linear measurement area 100a parallel to the x-axis direction of the measurement target 100 changes depending on the position in the x-axis direction if there are irregularities on the surface or if the surface is inclined. Therefore, the reflected light from the measurement area 100a of the multiple luminous beams of the discretized first light 101 has different optical path lengths for each of the multiple luminous beams.

[0026] As shown in Figure 4(c), the discretized first light 101 reflected at the measurement site 100a of the object to be measured 100 passes through the cylindrical array of the structured optical system 300 again, but in the opposite direction to when it was irradiated. At this time, the NA (numerical aperture) of each cylindrical lens constituting the cylindrical array of the structured optical system 300 is smaller than the NA of the focusing lens 26 when there is no cylindrical lens array. Therefore, when the first light 101 is reflected at the measurement site 100a of the object to be measured 100, only a smaller portion of the scattered light can enter the structured optical system 300 compared to when there is no structured optical system 300. Thus, the amount of scattered light that reaches the photodetector 80 can be limited, and the speckle of the light intensity caused by scattered light can be reduced.

[0027] The reflected light of the first light 101 that has passed through the structured optical system 300 is further expanded in the y-axis direction by passing through the focusing lens 26 and the cylindrical lens 25 in sequence, and is incident on the beam splitter 24, reflected, and irradiated onto the two-dimensional detection surface of the photodetector 80.

[0028] Meanwhile, the light emitted from the light source 11 that is reflected in the direction of the optical axis 92 by the beam splitter 24 passes through the focusing lenses 27 and 28 and reaches the optical path length modulator 70.

[0029] The optical path length modulator 70 changes the optical path length according to a predetermined one-dimensional position (y-axis direction) on the beam cross-section by reflecting the irradiated light beam. In this case, the optical path length modulator 70 uses a stepped reflecting element with a number of steps in a predetermined direction (y-axis direction), as shown in Figure 3(c).

[0030] The light whose optical path length has been modulated by the optical path length modulator 70 passes through the focusing lenses 28, 27 and the beam splitter 24 as a second beam 102 and is irradiated onto the two-dimensional detection surface of the photodetector 80.

[0031] The optical path length modulator 70 is not limited to a stepped reflective element; a diffraction grating can also be used. The groove shape of the diffraction grating can be any shape; for example, a sawtooth, sinusoidal, or rectangular shape can be used. When a diffraction grating is used as the optical path length modulator 70, diffracted light of a predetermined order is used as the second light 102 and irradiated onto the object to be measured 100. Therefore, the diffraction grating is arranged so that its main plane is inclined with respect to the optical axis 92, and the wavefront of the diffracted light of a predetermined order used as the second light 102 reaches the surface of the object to be measured 100. In this case, it is preferable to incline the diffraction grating so that the wavefront of the diffracted light of a predetermined order, which is the second light 102, is irradiated onto the surface of the object to be measured 100 at an angle parallel or nearly parallel.

[0032] The focusing lenses 28 and 27 align the direction in which the optical path length of the second light 102 is changing (y-axis direction) with the direction in which the light reflected from the object being measured 100 is magnified (y-axis direction) on the two-dimensional detection surface of the photodetector 80 (see Figure 3(d)).

[0033] As a result, on the two-dimensional detection surface of the photodetector 80, the first light 101, which is reflected light from a linear measurement area 100a parallel to the x-axis direction of the object to be measured 100 and is amplified in the y-axis direction, and the second light 102, whose optical path length is changing in the y-axis direction, interfere with each other, and the intensity of the interference light is detected on the two-dimensional plane of the photodetector 80.

[0034] Here, the first light 101 is discretized in the x-axis direction by the structured optical system 300, and therefore the interference light detected on the two-dimensional detection surface of the photodetector 80 is also discretized in the x-axis direction. In other words, the emission lines of the interference light detected on the two-dimensional detection surface of the photodetector 80 become dashed lines discretized in the x-axis direction, as shown in Figure 3(d).

[0035] <Image generation unit 31> The image generation unit 31 generates an image using the output of detection elements arranged on the two-dimensional detection surface of the photodetector 80 as pixel values.

[0036] The intensity of the interference light is maximized when the optical path length of the first light 101 matches the optical path length of the second light 102, which is modulated in the y-axis direction. Therefore, on the two-dimensional detection surface of the photodetector 80, the y-axis position where the light intensity is maximized for each x-axis position, as shown in Figure 3(d), indicates the position (depth, z-direction) on the surface of the measurement area 100a of the object to be measured 100.

[0037] Therefore, as shown in Figure 3(d), the z-axis direction irregularities of the measurement area 100a of the measurement target 100 can be detected as the position of the interference light emission lines in the y-axis direction from the output image of the two-dimensional detection surface of the photodetector 80.

[0038] The image generation unit 31 repeats the operation of acquiring the output image of the two-dimensional detection surface of the photodetector 80 as described above, while moving the object to be measured 100 in the y-axis direction relative to the first light 101, as shown in Figure 3(a). In this way, the image generation unit 31 can acquire a two-dimensional image of the photodetector 80 while sequentially moving the measurement area 100a of the object to be measured 100 in the y-axis direction.

[0039] <Surface shape detection unit 32> The surface shape detection unit 32 can detect the unevenness in the z-axis direction of a linear measurement area 100a parallel to the x-axis direction of the measurement target 100 by determining the position in the y-axis direction where the light intensity is maximum at each x-axis position in each image generated by the image generation unit 31. From a single image, the unevenness shape in the z-axis direction of a single linear measurement area 100a along the x-axis direction can be obtained.

[0040] The surface shape detection unit 32 obtains the three-dimensional shape of the surface (xy plane) of the measurement target 100 by determining the uneven shape of linear measurement areas 100a parallel to the x-axis direction from all images acquired while relatively moving the measurement target 100 in the y-axis direction, and arranging them in the y-axis direction.

[0041] Furthermore, as shown in Figure 3(a), the operation of moving the object to be measured 100 in the y-axis direction relative to the first light 101 can be achieved by moving the object to be measured 100, or by moving the irradiation position of the first light 101 on the object to be measured 100 in the y-axis direction. In the latter case, this can be achieved by oscillating an optical system that moves the first light 101 in the y-axis direction, such as the mirror 21. For this purpose, a motor for oscillating the optical system can be provided in the interference system 10.

[0042] <Display section 34> The display unit 34 displays the surface shape of the measurement target 100 determined by the surface shape detection unit 32.

[0043] <Control Unit 35> The control unit 35 synchronizes the timing of the light source 11 emitting light with the timing of the photodetector 80 detecting interference light. The control unit 35 also controls the movement of the object to be measured 100 in the y-axis direction relative to the first light 101.

[0044] <Effects of the First Embodiment> As described above, the surface shape measuring device of this embodiment detects interference light obtained by interfering a first broadband white light with a second broadband light. When the difference in optical path length is used as a variable, the intensity of the detected interference light becomes a correlated waveform. The width of the correlated waveform narrows inversely proportional to the bandwidth of the broadband light. Therefore, in this embodiment, the resolution can be increased by using broadband light. As a result, the surface can be detected as a narrow emission line in the y-axis direction (corresponding to the depth position in the z-axis direction) of the two-dimensional detection surface of the photodetector 80 (see paragraph 0005 of Japanese Patent No. 5740701).

[0045] Furthermore, since the surface shape measuring device of this embodiment structures (discretizes) the first light 101 by the structured optical system 300, it is possible to suppress the scattered light generated when the first light 101 is irradiated onto the object to be measured 100 from reaching the photodetector 80. Therefore, it is possible to suppress the occurrence of speckle in the image detected on the detection surface of the photodetector 80.

[0046] As a result, even in cases where the surface of the object to be measured 100 is rough or has steps, resulting in a lot of scattered light and speckle, and where the surface irregularities are difficult to detect with the conventional linear first light 101, the introduction of structured light makes it possible to accurately detect the surface shape.

[0047] Furthermore, by structuring (discretizing) the first light 101, the light irradiation intensity to a single measurement point can be increased. This increases the intensity of the interference light detected by the photodetector 80, thereby improving the sensitivity of detecting surface irregularities.

[0048] <Variation> In the first embodiment, the light source 11 was configured to emit broadband light, but the broadband light may also be comb light, which is divided into multiple frequency (wavelength) bands in a comb-like manner, as shown in Figure 5.

[0049] By using comb light, the depth direction (z-axis direction) of the object to be measured 100 can be divided into multiple detection ranges equal to the number of interference orders, and these can be superimposed and displayed on the same two-dimensional detection surface of the photodetector 80. In particular, if we focus on the strong reflection or scattering light from the surface, even if the surface position is outside the detection range of one interference order, it will fall within the detection range of another interference order and can be detected. In other words, it becomes possible to detect interference light over a wide detection range at different positions in the y-axis direction on the detection surface of the photodetector 80.

[0050] <<Second Embodiment>> A surface shape measuring device 1 of the second embodiment will be described with reference to Figure 6.

[0051] The surface shape measuring device 1 of the second embodiment has the same configuration as the first embodiment, but the process by which the surface shape detection unit 32 detects the surface shape from the image generated by the image generation unit 31 differs from that of the first embodiment.

[0052] Figure 6(a) shows the correspondence between the multiple luminous beams of the divided first light 101 and the two-dimensional detection surface of the photodetector 80. Figure 6(b) shows the arrangement of pixels in the divided region 60 of the two-dimensional detection surface and the pixel values, and Figure 6(c) shows the state in which the pixel values ​​of each pixel row 61 in region 60 are replaced with the average value of the pixel values ​​of that pixel row 61. Figure 6(d) is a graph plotting the position where the average value of the pixel row 61 in the y-axis direction is maximum, as the position of the interference light.

[0053] In the second embodiment, as shown in Figure 6(a), the surface shape detection unit 32 divides the image of the two-dimensional detection surface of the photodetector 80 generated by the image generation unit 31 into regions of the two-dimensional detection surface that each of the multiple beams of light 101 divided by the structured optical system 300 reaches, in the first direction (x-axis direction). As a result, as shown in Figure 6(a), multiple regions 60 are set in the image of the two-dimensional detection surface, each having a width in the x-axis direction corresponding to the width of the divided beams of light 101 (for example, several pixels to tens of pixels, corresponding to a width of several μm on the measurement target 100), and a length in the y-axis direction corresponding to the total length of the two-dimensional detection surface.

[0054] The surface shape detection unit 32 calculates the average value of multiple pixels constituting a pixel row 61 (row direction in Figure 6(b)) arranged in a first direction (x-axis direction) within the divided region 60, as shown in Figure 6(b), and replaces the value of each pixel in that pixel row with the calculated average value (see Figure 6(c)). For all pixel rows 61 within the region 60, the average value is calculated for each, and the average value is replaced with the pixel value of each pixel in that pixel row 61 (see Figure 6(c)).

[0055] The surface shape detection unit 32 compares the average values ​​of all pixel rows 61 in the second direction (y-axis direction) of the divided region 60 and selects the pixel row 61a with the largest average value. The y-axis position of the selected pixel row 61a is the position in the region 60 where interference light between the first light 101 and the second light 102 is detected.

[0056] The surface shape detection unit 32 performs the above process for all regions 60 divided in Figure 6(a), and calculates the position of the interference light in the y-axis direction for each region 60.

[0057] The surface shape detection unit 32 plots the position of the interference light in the y-axis direction calculated for each region 60 on a graph with x and y axes as two axes. In this case, the x-axis direction is set to the position of the representative pixel 62 in the x-axis direction of region 60. In Figure 6(d), the representative pixel 62 is set to the pixel located in the center of the x-axis direction of region 60.

[0058] By processing in this way, even if some pixel values ​​show larger values ​​due to speckle, they are averaged out, thus suppressing their impact on the position detection of interfering light. Therefore, the position detection of interfering light can be performed stably while suppressing the effects of speckle.

[0059] Therefore, according to the second embodiment, in addition to the effects achieved by the surface shape measuring device 1 of the first embodiment, it is possible to further suppress speckle and stably detect the interference position.

[0060] In the second embodiment, the pixel values ​​are averaged across the pixel rows of region 60, which reduces the resolution. However, the effect of resolution improvement due to speckle removal is greater, so by performing the processing of the surface shape detection unit 32 in the second embodiment, the resolution of shape measurement of the object to be measured 100 can be improved. Furthermore, the reduction in resolution can be suppressed by narrowing the spacing of the light beams that divide the first light 101.

[0061] In the surface shape measuring device 1 of the second embodiment, the configuration, operation, and effects other than those described above are the same as those of the surface shape measuring device 1 of the first embodiment, so a description will be omitted. [Examples]

[0062] Examples of the present invention will be described below.

[0063] In this example, the surface shape of 100 samples was measured using the surface shape measuring device 1 shown in Figure 7. The pitch of the cylindrical lenses in the cylindrical array of the structured optical system 300 was set to 800 μm.

[0064] <Example 1> As in Example 1, a rough metal plate was used as the sample for measurement 100, as shown in Figure 8(a). The surface of the sample was tilted to the optical axis of the first light 101, and measurement was performed using the surface shape measuring device 1 shown in Figure 7. The image detected by the two-dimensional detection surface of the photodetector 80 is shown in Figure 8(b).

[0065] As shown in Figure 8(b), on the two-dimensional detection surface, the interference signal appeared quantized at intervals of 814 μm.

[0066] In contrast, as a comparative example, a rough metal plate was similarly measured as the object to be measured 100 using a device that was the same as the surface shape measuring device 1 shown in Figure 7 but without the structured optical system 300. Figure 8(c) shows the image detected by the two-dimensional detection surface of the photodetector 80 of the comparative example device.

[0067] The image in Figure 8(b) of Example 1 shows that, on the two-dimensional detection surface of the photodetector 80, the divided first light 101 is quantized at intervals of 800 μm and clearly detected, and the surface position of the object to be measured 100 could be accurately detected by the position of the interference light in the y-axis direction. In contrast, the image in Figure 8(c) of the comparative example shows that the interference light is clearly detected in the central region in the x-axis direction of the two-dimensional detection surface of the photodetector 80, but there were parts where the interference light was unclear at both ends in the x-axis direction.

[0068] Furthermore, using the image in Figure 8(b) of Example 1, the surface shape detection unit 32 of Example 2 was used to set a region 60, and the average value of the pixel rows within the region 60 was calculated. The position with the largest average pixel value in the y-axis direction was defined as the position of the interference light and plotted, as shown in Figure 9(b). The plotted position closely matched the emission line of the interference light shown in the image in Figure 9(a) (the same image as Figure 8(b)).

[0069] <Example 2> As Example 2, a rough metal plate was used as the sample for measurement 100, and the inclination angle of the sample surface with respect to the optical axis of the first light 101 was changed from 0 degrees to 10 degrees (0 degrees being defined as when the sample surface is perpendicular to the optical axis of the first light 101), and an image of the two-dimensional detection surface of the photodetector 80 was acquired at each inclination angle.

[0070] From the obtained two-dimensional image of the photodetector 80's detection surface, an approximate straight line of interference light emission was determined. Pixels with bright spots appearing at a certain distance or more from the approximate straight line were identified as errors, and the ratio of error pixels to the total number of pixels on the approximate straight line was calculated as the error rate.

[0071] As a comparative example, images were acquired in the same manner using a surface shape measuring device without the structured optical system 300, and the error rate was calculated.

[0072] Figures 10(a) and (b) show images of the two-dimensional detection surface when the sample is placed at a certain inclination angle. Figure 10(a) is an image of a comparative example, and Figure 10(b) is an image of Example 2.

[0073] In the comparative example, Figure 10(a) shows a bright line appearing at a distance from the approximation curve, resulting in multiple speckles. However, in the image of Example 2, Figure 10(b), no speckles are present.

[0074] Furthermore, Figure 10(c) shows a graph plotting the error rate for each tilt angle of the sample relative to the optical axis. As shown in Figure 10(c), the surface shape measuring device 1 of the embodiment showed a significantly improved error rate compared to the comparative example. In particular, when the tilt angle of the sample was 5 degrees or less, the error rate was 0%.

[0075] As described above, it was confirmed that the surface shape measuring device 1 of the embodiment equipped with the structured optical system 300 has improved sensitivity to the inclined surface of the object to be measured 100.

[0076] <Example 3> As Example 3, a metal plate with a step on its surface (step gauge) was used as the sample for measurement target 100 (see Figure 11(a)). The longitudinal direction of the step was positioned parallel to the x-axis direction in Figure 3(a) (the longitudinal direction of the measurement area 100a), and the surface shape was measured at 5 μm intervals in the y-axis direction while moving (sweeping) the measurement target 100 in the y-axis direction. The height of the step in the sample for measurement target 100 was 300 μm.

[0077] Figures 11(b) and (c) are graphs showing the measured surface height (position in the z direction) at a certain position in the x-axis direction of the sample of the object to be measured 100, for each position in the y-axis direction of the object to be measured 100. Figure 11(c) shows the results measured with the surface shape measuring device 1 of the example, and Figure 11(b) shows the results measured with the surface shape measuring device of the comparative example which does not have a structured optical system 300.

[0078] Because the longitudinal direction of the step is positioned parallel to the x-axis direction (the longitudinal direction of the measurement area 100a), in both measurement results in Figure 11(b) and (c), a height difference of 300 μm was accurately detected at positions away from the step. However, at the location of the step, areas where the surface shape could not be accurately measured (dead zones) occurred due to the influence of light diffraction caused by the step.

[0079] The width of the insensitive region (y-axis direction) was 130 μm in the example, as shown in Figure 11(c), while it was 220 μm in the comparative example, as shown in Figure 11(b). In the example, a reduction of 90 μm was achieved by arranging the structured optical system 300.

[0080] This is likely due to the reduction in scattering components caused by the placement of the structured optical system 300, which enabled measurements even at low signal intensities.

[0081] Therefore, by using the surface shape measuring device 1 of the embodiment, scattering components that caused a decrease in sensitivity can be suppressed, the dead zone of the stepped portion of the measurement target 100, which was previously difficult to measure, can be narrowed, and the measurable range can be expanded. [Explanation of Symbols]

[0082] 1. Surface shape measuring device 10 Interferential Systems 11 Light source 21 Mirror 22 Neutral Density Filters 23 Beam Expander 24 Beam Splitter 25 Cylindrical Lens 26 Focusing lens 27. Focusing lens 28 Focusing lens 31 Image generation unit 32 Surface shape detection unit 34 Display section 35 Control Unit 70 Optical path length modulator 80 Photodetectors 91 Optical axis 92 Optical axis 100 items to measure 100a Measurement site 101 The First Light 102 The Second Light 300 Structured optics

Claims

1. It has a light source unit that forms a first light and a second light, and a photodetector, The photodetector includes a plurality of detection elements arranged in one or two dimensions, and detects light resulting from the interference of the first light and the second light that are irradiated onto the object to be measured and reflected. The surface shape measuring device is characterized in that the light source unit forms a plurality of light beams as the first light, focuses each of the plurality of light beams, and irradiates the object to be measured in a line.

2. A surface shape measuring device according to claim 1, wherein the light source unit comprises a light source and a structured optical system, The structured optical system is positioned between the light source and the object to be measured, and is characterized by dividing the light beam emitted from the light source into a plurality of light beams, focusing each of the plurality of light beams to form the first light, and irradiating the object to be measured in a line.

3. A surface shape measuring device according to claim 2, The photodetector includes a plurality of detection elements, the detection elements are arranged in two dimensions, and constitute a two-dimensional detection surface. The light source unit further comprises an optical path length modulator and an optical system, and the light source emits broadband light. The optical system forms a linear beam with a cross-sectional shape that is long in the first direction from a portion of the light beam emitted from the light source, and irradiates the optical path length modulator with the remaining portion of the light beam. The structured optical system is positioned between the optical system and the object to be measured, and divides the linear beam of light, which has a cross-sectional shape of the beam formed by the optical system and is long in the first direction, into multiple beams in the first direction, and focuses each of the multiple beams of light to illuminate the object to be measured in a line as the first light. The optical path length modulator generates a second light by changing the optical path length of the other portion of the light beam according to a predetermined one-dimensional position on the beam cross-section. The optical system causes the optical system to detect interference light between the reflected light of the first light and the second light on the object to be measured, on the two-dimensional detection surface of the photodetector by spreading the cross-section of the beam of reflected light from the first light, which is irradiated onto the object to be measured in a line, in a second direction perpendicular to the first direction, and by causing the second light, whose optical path length has been changed by the optical path length modulator, to be incident on the two-dimensional detection surface of the photodetector such that the one-dimensional direction in which the optical path length has been changed coincides with the second direction, thereby causing the optical system to detect interference light between the reflected light of the first light and the object to be measured and the second light. A surface shape measuring device characterized by the following features.

4. A surface shape measuring device according to claim 2, wherein the structured optical system includes a cylindrical array in which a plurality of cylindrical lenses are arranged in a direction perpendicular to the long axis of the cylindrical lenses.

5. A surface shape measuring device according to claim 2, characterized in that the structured optical system is arranged such that a plurality of light beams reflected by the object to be measured pass through the structured optical system toward the photodetector in the opposite direction to the direction of irradiation.

6. A surface shape measuring device according to claim 3, wherein the optical path length modulator is an element having a stepped reflective surface or a diffraction grating.

7. A surface shape measuring device according to claim 3, further comprising an image generation unit and a surface shape detection unit, The image generation unit generates a two-dimensional image having two sides corresponding to the first direction and the second direction from the detection results of the two-dimensional detection surface of the photodetector. The surface shape measuring device is characterized in that the surface shape detection unit determines the surface position of the object to be measured by detecting the detection position of the interference light in the second direction on the image.

8. A surface shape measuring device according to claim 7, wherein the surface shape detection unit divides the image into regions corresponding to the divided plurality of light beams in the first direction, calculates the average value for each pixel row arranged in the first direction within the divided region, and sets the position in the second direction of the divided region where the average value is largest as the detection position of the interference light.

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