Height measuring device and height measuring method

Abstract

The height measuring device of the present invention comprises: a light irradiation unit that irradiates a sample with irradiation light including a plurality of light beams at an angle inclined relative to the height direction of the sample, the plurality of light beams being arranged in a direction intersecting the optical axis direction and having different wavelengths; a camera system that detects light from the sample irradiated with the irradiation light and outputs wavelength information of the light; and a control device that calculates the height of the sample based on the wavelength information; and the camera system comprises: a tilted dichroic mirror whose transmittance and reflectance vary according to the wavelength in a specific wavelength region and separates the light from the sample by transmitting and reflecting the light; a photodetector that detects the amount of reflected light from the light reflected by the tilted dichroic mirror; a photodetector that detects the amount of transmitted light from the light that has passed through the tilted dichroic mirror; and a processing unit that calculates wavelength information based on the ratio of the amount of reflected light to the amount of transmitted light and outputs the calculated information.

Description

Technical Field

[0001] One aspect of the present invention relates to a height measuring device and a height measuring method. Background Art

[0002] As a method for measuring the height of an object, there is a known method of irradiating the object with light and detecting the light from the object to measure the height (for example, see Patent Documents 1 to 3). The height measurement methods described in Patent Documents 1 to 3 irradiate the object with light consisting of multiple light beams arranged in a direction intersecting the optical axis and having different wavelengths at an angle inclined relative to the height direction of the object, and measure the height of the object based on the wavelength of the light reflected from the object.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 7-27520

[0006] Patent Document 2: Japanese Patent Application Laid-Open No. 2007-101399

[0007] Patent Document 3: Japanese Patent Application Laid-Open No. 2009-145279 Summary of the Invention

[0008] [Problems to be solved by the invention]

[0009] In the aforementioned height measurement method, the wavelength of light from the object being measured is determined using a color imaging element. Derivation of the wavelength in this manner is affected by the color of the object itself, potentially reducing the accuracy of the resulting height measurement.

[0010] One aspect of the present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a height measuring device and a height measuring method capable of measuring the height of a measurement object with higher accuracy.

[0011] [Technical means to solve the problem]

[0012] A height measuring device according to one embodiment of the present invention comprises: a light irradiation unit for irradiating an object to be measured with irradiation light including a plurality of light beams arranged in a direction intersecting an optical axis direction and having different wavelengths, onto the object to be measured at an angle inclined relative to a height direction of the object to be measured; a light detection unit for detecting light from the object to be measured irradiated with the irradiation light and outputting wavelength information of the light; and an analysis unit for calculating the height of the object to be measured based on the wavelength information; the light detection unit comprising: an optical element having a transmittance and a reflectance that vary according to the wavelength within a specific wavelength region and that separates the light from the object to be measured by transmitting and reflecting the light; a first light detector for detecting an amount of reflected light from the light reflected by the optical element; a second light detector for detecting an amount of transmitted light from the light transmitted by the optical element; and a processing unit for calculating and outputting wavelength information based on a ratio between the amount of reflected light and the amount of transmitted light.

[0013] In one aspect of the height measuring device of the present invention, irradiation light comprising multiple light beams is directed at an oblique angle relative to the height direction of the object. The multiple light beams are arranged in a direction intersecting the optical axis and have different wavelengths. Wavelength information is derived from the light emitted from the object and output, and the height of the object is calculated based on the wavelength information. In this manner, since the irradiation light comprising multiple light beams that differ in direction intersecting the optical axis is directed at an oblique direction (at an oblique angle) relative to the object, the wavelength of the light irradiating the object changes depending on the height of the object. Therefore, by detecting the light emitted from the object and deriving the wavelength information, the height of the object can be accurately calculated based on this wavelength information. In this aspect of the height measuring device of the present invention, light is separated by an optical element whose transmittance and reflectance vary depending on wavelength. The amount of reflected light is detected from the light reflected by the optical element, and the amount of transmitted light is detected from the light transmitted by the optical element. Wavelength information is calculated based on the ratio of the amount of reflected light to the amount of transmitted light. For example, when deriving the wavelength of light from an object to be measured based on the intensity of light captured by a color imaging element, the intensity of the light captured by the color imaging element varies due to the color of the object to be measured, raising concerns that the accuracy of calculating the wavelength information of the light cannot be guaranteed. In this case, the accuracy of measuring the height of the object to be measured based on the wavelength information will also be reduced. Regarding this point, in one aspect of the height measuring device of the present invention, as described above, light is separated by an optical element whose transmittance and reflectance vary according to wavelength, and wavelength information is calculated based on the ratio of the amount of reflected light to the amount of transmitted light after separation. Therefore, the wavelength information of the light can be calculated with high accuracy without being affected by the color of the object to be measured. With such a height measuring device, the height of the object to be measured can be calculated with high accuracy based on the wavelength information of the light calculated with high accuracy.

[0014] In the height measurement device, the first and second light detectors may be line sensors. By using line sensors, for example, the object being measured can be moved to change the imaging line while accurately capturing each imaging line. This allows for more accurate calculation of the height of the object being measured.

[0015] In the height measuring device, the light irradiation unit can irradiate the object to be measured with irradiation light including multiple beams of parallel light. By irradiating the object with parallel light, the correspondence between wavelength and height can be easily and appropriately derived, thereby enabling the height of the object to be measured to be calculated with higher accuracy.

[0016] In the height measuring device described above, the light irradiation unit may include: a light source that outputs white light; and a spectroscopic element that splits the white light output from the light source to output irradiation light consisting of multiple light beams, each having wavelengths that differ from one another in a direction intersecting the optical axis. In this manner, by splitting the white light that includes all visible light rays into individual light beams, it is possible to easily and appropriately output irradiation light consisting of multiple light beams having different wavelengths.

[0017] The height measuring device may further include a dark box that blocks light other than the light irradiated by the light irradiating unit. This configuration blocks light irrelevant to height measurement, enabling the height of the object to be measured to be calculated with greater accuracy.

[0018] The height measuring device may further include a transport unit for moving the object to be measured. With such a configuration, wavelength information of the entire object to be measured can be derived while changing the irradiation point of the irradiation light on the object to be measured, thereby measuring the height of the entire object to be measured.

[0019] One aspect of the height measurement method of the present invention includes: a light irradiation step of irradiating an object to be measured with irradiation light comprising multiple light beams arranged in a direction intersecting the optical axis and having different wavelengths; a wavelength calculation step of calculating wavelength information of light from the object to be measured based on the ratio of the amount of reflected light to the amount of transmitted light obtained by an optical element, a first photodetector, and a second photodetector. The optical element has a transmittance and reflectance that vary depending on wavelength within a specific wavelength region and separates light from the object by transmitting and reflecting the light; the first photodetector detects the amount of reflected light from light reflected by the optical element, and the second photodetector detects the amount of transmitted light from light transmitted by the optical element; and a height calculation step of calculating the height of the object to be measured based on the wavelength information. This height measurement method makes it possible to accurately calculate the height of the object to be measured based on the highly accurately calculated wavelength information of the light.

[0020] In the height measurement method described above, the light irradiation step may continuously change the irradiation point of the irradiation light on the object by moving the object, and the height calculation step may derive the shape of the object by calculating the height corresponding to each irradiation point on the object. In this height measurement method, the irradiation point of the irradiation light on the object continuously changes, thereby enabling the height of the entire object to be measured, and the shape of the object to be measured to be appropriately derived based on the height measurement results.

[0021] [Effects of the Invention]

[0022] According to the height measuring device according to one aspect of the present invention, the height of an object to be measured can be measured with higher accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 3 is a diagram schematically showing the height measuring device according to this embodiment.

[0024] Figure 2 A diagram illustrating the height measurement and shape estimation processing of a measurement object.

[0025] Figure 3 To express Figure 1 FIG. 1 is a diagram showing an example of the configuration of a light irradiation unit.

[0026] Figure 4 To schematically represent Figure 1 Diagram of the camera system shown.

[0027] Figure 5 A diagram illustrating the spectrum of light and the characteristics of a tilted dichroic mirror.

[0028] Figure 6 Flowchart showing the height measurement method according to this embodiment. DETAILED DESCRIPTION

[0029] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and duplicate descriptions are omitted.

[0030] Figure 1 This figure schematically illustrates a height measurement device 1 according to this embodiment. Height measurement device 1 irradiates a sample 100 with light and measures the height of the sample 100 based on the reflected light. Height measurement device 1 continuously changes the point of light irradiation within sample 100 to calculate the height of each region of sample 100. Ultimately, the shape of sample 100 is derived based on the heights of each region. Sample 100 can be any object whose height is to be measured, such as food or various processed products.

[0031] Figure 2 1 is a diagram illustrating the height measurement and shape estimation process of the sample 100. In the height measurement method and shape estimation method implemented by the height measurement device 1 of this embodiment, as shown in FIG. Figure 2 As shown, light containing multiple wavelengths is irradiated obliquely onto sample 100. The reflected light from sample 100 is separated by an inclined dichroic mirror 22 (described below) via a lens 21 (described below). The separated light is detected by photodetectors 23 and 24 (described below), which serve as line sensors or the like. Based on the brightness (light intensity) distribution of the light detected by each photodetector 23 and 24, the wavelength information of the light at each irradiation point is restored. The height at each irradiation point is calculated based on the wavelength information, and the shape of sample 100 is restored based on the height at each irradiation point. Details will be described below.

[0032] like Figure 1 As shown, the height measuring device 1 includes a light irradiation unit 10 , a camera system 20 (light detection unit), a control device 30 (analysis unit), a dark box 40 , and a belt conveyor 50 (transport unit).

[0033] The belt conveyor 50 is a transport unit that moves the sample 100. By moving the sample 100 in one horizontal direction, the belt conveyor 50 changes the irradiation point of the sample 100 with the irradiation light (the irradiation light emitted by the light irradiation unit 10). The belt conveyor 50 includes a belt unit 52 that carries the sample 100 and moves in the aforementioned direction, and an actuator 51 that actuates the belt unit 52. The actuator 51 is controlled by the control unit 31 (described below) of the control device 30.

[0034] The dark box 40 houses at least the light irradiation unit 10, the camera system 20, and a portion of the belt conveyor 50 (specifically, the point where light from the light irradiation unit 10 is irradiated onto the sample 100 placed on the belt conveyor 50) of the components of the height measuring device 1, and is arranged to prevent external light from affecting the housed components. The dark box 40 blocks light other than the light irradiated from the light irradiation unit 10 as light irradiating the sample 100.

[0035] The light irradiation unit 10 irradiates the sample 100 (measurement object) with irradiation light including a plurality of light beams arranged in a direction intersecting the optical axis direction and having different wavelengths at an angle inclined relative to the height direction of the sample 100. Figure 1As shown, among the irradiation light irradiated from the light irradiation unit 10 to the sample 100, flat light beams Li1, Li2, ... LiX (X is a positive integer) of different wavelengths are arranged without gaps along a direction intersecting the optical axis direction. The angle of inclination relative to the height direction of the sample 100 is an angle other than the vertical direction, and more specifically, an angle other than the vertical and horizontal directions (an angle in the oblique direction). By irradiating the sample 100 with such irradiation light, a point on the sample 100 is irradiated with a color that varies according to the height (only one of the flat light beams Li1, Li2, ... LiX). Therefore, by observing the light reflected from the sample 100, the height of the irradiated point of the sample 100 can be derived. The light irradiation unit 10 irradiates the sample 100 with irradiation light including multiple light beams as parallel light. The light irradiation unit 10 includes, for example, a light source 11 and spectroscopic elements 12 and 13. In this way, the light irradiation unit 10 includes two spectroscopic elements 12 and 13 as elements related to the spectroscopic analysis of light.

[0036] The light source 11 is, for example, a white light source that outputs white light, such as a white LED (Light Emitting Diode), a lamp light source, a supercontinuum light source, or a laser-excited white light source. The light source 11 may also be a light source that outputs light other than white light. The light emitted from the light source 11 includes wavelengths that can be reflected and scattered by the sample 100, and is selected based on the sample 100. The light source 11 outputs light of a wavelength included in a specific wavelength range (a wavelength range in which the transmittance and reflectance of the tilted dichroic mirror 22 vary depending on the wavelength) of the tilted dichroic mirror 22 (described below) included in the camera system 20. Figure 5 Graphs illustrating the relationship between the characteristics of the tilted dichroic mirror 22 and the wavelength of light emitted from the light source 11 . Figure 5 In FIG, the horizontal axis represents the wavelength, and the vertical axis represents the transmittance of the tilted dichroic mirror 22. Figure 5 As shown in the characteristic X4 of the tilted dichroic mirror 22, in the tilted dichroic mirror 22, in the specific wavelength region X1, the transmittance (and reflectance) of light changes smoothly according to the wavelength change, and in the wavelength region outside the specific wavelength region, the transmittance (and reflectance) of light is constant regardless of the wavelength change. In other words, in the specific wavelength band (the wavelength band of λ1 to λ2), the transmittance of light changes in a monotonically increasing manner (the reflectance changes in a monotonically decreasing manner) according to the wavelength change. Figure 5 As shown, the light X2 outputted from the light source 11 includes light of wavelengths included in the specific wavelength region X1. That is, the light source 11 outputs light of a broad spectrum including the specific wavelength region X1.

[0037] Back to Figure 1Spectroscopic elements 12 and 13 split the white light output from light source 11 into rainbow colors by wavelength, thereby outputting irradiation light consisting of a plurality of flat light beams Li1, Li2, ..., LiX, each having wavelengths that differ from one another in a direction intersecting the optical axis. Spectroscopic element 12 receives the white light output from light source 11 and outputs the light toward spectroscopic element 13. Spectroscopic element 13 receives the light output from spectroscopic element 12 and outputs the irradiation light as parallel light toward sample 100.

[0038] Figure 3 2 is a diagram showing a configuration example of the light irradiation unit 10 . Figure 3 The light irradiation unit 10 shown in (a) includes diffraction gratings 12a and 13a as the spectroscopic elements 12 and 13. The diffraction gratings 12a and 13a output light beams of different wavelengths so that they are more effectively bent as the wavelength becomes longer. The diffraction grating 13a may also be a lens. Figure 3 The light irradiation unit 10 shown in (b) includes prisms 12b and 13b as the spectroscopic elements 12 and 13. The prisms 12b and 13b output light beams of various wavelengths in a manner that bends shorter wavelengths more effectively, depending on the refractive index of each wavelength. Furthermore, the prism 13b may also be a lens. The following description will be based on the case where the spectroscopic elements 12 and 13 are diffraction gratings 12a and 13a.

[0039] Back to Figure 1 The camera system 20 detects light from the sample 100 irradiated with the irradiation light from the light irradiation unit 10 and outputs wavelength information of the light. The camera system 20 is disposed at a position where it can detect light from the sample 100 . Figure 4 To schematically represent Figure 1 FIG. 20 is a diagram of a camera system 20 shown in FIG. Figure 4 As shown, the camera system 20 includes a lens 21 , a tilted dichroic mirror 22 (optical element), photodetectors 23 and 24 (a first photodetector and a second photodetector), bandpass filters 25 and 26 , and a processing unit 27 .

[0040] The lens 21 is a lens that focuses the incident light from the sample 100. The lens 21 can be arranged in the front stage (upstream) of the tilted dichroic mirror 22, or in the area between the tilted dichroic mirror 22 and the photodetectors 23 and 24. The lens 21 can be a finite focus lens or an infinite focus lens. When the lens 21 is a finite focus lens, the distance from the lens 21 to the photodetectors 23 and 24 is set to a specified value. When the lens 21 is an infinite focus lens, the lens 21 is a collimating lens that converts the light from the sample 100 into parallel light, and aberration correction is performed in a manner to obtain parallel light. The light output from the lens 21 is incident on the tilted dichroic mirror 22.

[0041] The tilted dichroic mirror 22 is an optical element made of a special optical material, and transmits and reflects light from the sample 100 according to wavelength, thereby separating the light. The tilted dichroic mirror 22 is configured so that the transmittance and reflectance of light vary according to wavelength within a specific wavelength range.

[0042] Figure 5 Graphs illustrating the spectrum of light and the characteristics of the tilted dichroic mirror 22 . Figure 5 In FIG, the horizontal axis represents wavelength, and the vertical axis represents spectral intensity (when the spectrum of light) and transmittance (when the dichroic reflector 22 is tilted). Figure 5 As shown in characteristic X4 of the tilted dichroic mirror 22, within a specific wavelength range (the wavelength range λ1 to λ2), the transmittance (and reflectance) of light in the tilted dichroic mirror 22 varies smoothly with wavelength. In wavelength ranges outside this specific wavelength range (i.e., on the low-wavelength side below wavelength λ1 and the high-wavelength side above wavelength λ2), the transmittance (and reflectance) of light remains constant regardless of wavelength. Transmittance and reflectance have an inverse correlation; as one increases, the other decreases. Therefore, the term "transmittance (and reflectance)" may be used below, rather than simply "transmittance." Furthermore, the phrase "light transmittance remains constant regardless of wavelength" encompasses not only completely constant conditions but also, for example, conditions where the transmittance changes by less than 0.1% with a 1 nm wavelength change. On the lower wavelength side (below wavelength λ1), light transmittance is approximately 0% regardless of wavelength. On the higher wavelength side (below wavelength λ2), light transmittance is approximately 100% regardless of wavelength. Furthermore, "light transmittance of approximately 0%" includes transmittances of approximately 0% + 10%, and "light transmittance of approximately 100%" includes transmittances of approximately 100% - 10%.

[0043] Back to Figure 4 Photodetectors 23 and 24 detect the light separated by the tilted dichroic mirror 22. Photodetectors 23 and 24 are, for example, one-dimensional line sensors. Photodetector 23 detects the amount of light transmitted through the tilted dichroic mirror 22. Photodetector 24 detects light reflected from the tilted dichroic mirror 22. The wavelength ranges to which photodetectors 23 and 24 are sensitive correspond to the specific wavelength region where the transmittance (and reflectance) of light in the tilted dichroic mirror 22 changes depending on wavelength.

[0044] The bandpass filter 25 is disposed between the tilted dichroic mirror 22 and the photodetector 23. The bandpass filter 26 is disposed between the tilted dichroic mirror 22 and the photodetector 24. The bandpass filters 25 and 26 may be, for example, filters that remove light in wavelength regions other than the specific wavelength region (a wavelength region in which the transmittance and reflectance of light in the tilted dichroic mirror 22 vary depending on the wavelength).

[0045] The processing unit 27 calculates wavelength information based on the ratio of the amount of transmitted light detected by the photodetector 23 to the amount of reflected light detected by the photodetector 24, and outputs the information to the control device 30. In this height measuring device 1, the light irradiated onto a point on the sample 100 moved by the belt conveyor 50 is monochromatic. That is, the light irradiated onto a point on the sample 100 is only one of the irradiation light beams, which includes multiple light beams with different wavelengths, and is monochromatic. If the wavelength of the irradiated light (the wavelength to be derived) is λ, the amount of transmitted light is T, and the amount of reflected light is R, the wavelength shift parameter S is expressed by the following equation (1).

[0046] S=(T-R) / (T+R) (1)

[0047] Here, if the wavelength at which the reflectivity of the tilted dichroic mirror 22 reaches 100% is λ1, and the wavelength at which the transmittance reaches 100% is λ2, then based on the characteristic that the rate of change of the tilted dichroic mirror changes linearly with respect to the wavelength, it is clear that the wavelength λ at which the transmittance is 50% is λ2. 50％ = (λ1+λ2) / 2. At this time, the wavelength shift parameter S becomes 0. Therefore, the change amount when the wavelength shifts Δλ is expressed by the wavelength shift parameter S as shown in the following equation (2). In addition, the wavelength λ is expressed by the following equation (3).

[0048] Δλ=S(λ2-λ1) / 2 (2)

[0049] λ=λ 50％ +Δλ (3)

[0050] The processing unit 27 outputs the wavelength (wavelength information) derived using these equations to the control device 30 .

[0051] Back to Figure 1The control device 30 is a computer, physically comprising memories such as RAM (Random Access Memory) and ROM (Read Only Memory), a processor (calculation circuit) such as a CPU (Central Processing Unit), a communication interface, and a storage unit such as a hard disk. The control device 30 functions by utilizing the computer system's CPU to execute programs stored in the memory. The control device 30 may also be comprised of a microcomputer or an FPGA (Field Programmable Gate Array).

[0052] The control device 30 includes a control unit 31, a calculation unit 32, and a display unit 33. The control unit 31 controls the various components of the height measuring device 1. Specifically, the control unit 31 controls the camera system 20 and the actuator 51 of the belt conveyor 50. The control unit 31 adjusts the conveying speed of the belt conveyor 50 by controlling the actuator, thereby controlling the line rate of the photodetectors 23 and 24 within the camera system 20, such as line sensors.

[0053] The calculation unit 32 calculates the height of the sample 100 (the height of a point on the sample 100 irradiated with the irradiation light) based on the wavelength information derived by the processing unit 27. The calculation unit 32 calculates the height of the sample 100 based on the pitch D of the diffraction grating, the wavelength λ, and the distance L between the spectroscopic elements 12 and 13. Currently, the irradiation light is parallelized by the spectroscopic elements 12 and 13, which are diffraction gratings. Therefore, the height h per wavelength is expressed by the following equation (4), and the height H of the sample 100 is expressed by the following equation (5). Furthermore, θ is the tilt angle of the light relative to the spectroscopic element 13, and Φ is the angle at which the irradiation light is tilted from the horizontal direction.

[0054] h=L*tanθ=L*λ / √(D 2 -λ 2 ) (4)

[0055] H=hcosΦ (5)

[0056] Calculation unit 32 can also derive the shape of sample 100 by calculating the height corresponding to each irradiation point on sample 100. For example, when light detectors 23 and 24 are line sensors, the height is measured for each line. Therefore, by continuously calculating the height of each line, the three-dimensional shape of sample 100 can be derived. Furthermore, when prisms are used as spectroscopic elements 12 and 13, the refractive index difference for each wavelength depends on the refractive index of the glass and cannot be simply calculated. Therefore, the height is calculated not by the mathematical formula described above, but by conversion using a pre-acquired table or by approximation using an approximation curve.

[0057] The display unit 33 displays information related to the height of the sample 100 calculated by the calculation unit 32. The display unit 33 displays, for example, the detection results (imaging results) of the light detectors 23 and 24 and information on the height of the sample 100. Furthermore, the display unit 33 may also display the shape (restored shape) of the sample 100 derived from the height corresponding to each irradiation point.

[0058] Secondly, refer to Figure 6 A description will be given of a height measurement method performed by the height measurement device 1 of this embodiment. Figure 6 Flowchart showing the height measurement method according to this embodiment.

[0059] In the height measurement method of this embodiment, as Figure 6 As shown, the sample 100 is irradiated with irradiation light from an oblique direction while being moved by the belt conveyor 50 (step S1: light irradiation step). The irradiation light includes a plurality of light beams arranged in a direction intersecting the optical axis and having different wavelengths.

[0060] Next, wavelength information of the light is calculated based on the reflected light from the sample 100 (step S2: wavelength calculation step). Specifically, the wavelength information is calculated based on the ratio between the amount of transmitted light and the amount of reflected light separated by the tilted dichroic mirror 22.

[0061] Next, the height of the sample 100 is calculated based on the wavelength information (step S3: height calculation step). In the height calculation step, the shape of the sample 100 can also be restored (derived) by calculating the height corresponding to each irradiation point on the sample 100, which changes due to the movement of the sample 100. The above is the height measurement method implemented by the height measurement device 1.

[0062] Next, the effects of the height measurement device 1 and the height measurement method according to the present embodiment will be described.

[0063] The height measuring device 1 of this embodiment includes: a light irradiation unit 10, which irradiates the sample 100 with irradiation light including multiple light beams at an angle inclined relative to the height direction of the sample 100, the multiple light beams being arranged in a direction intersecting the optical axis direction and having different wavelengths; a camera system 20, which detects light from the sample 100 irradiated with the irradiation light and outputs wavelength information of the light; and a control device 30, which calculates the height of the sample 100 based on the wavelength information; and the camera system 20 has: a tilted dichroic mirror 22, whose transmittance and reflectance vary according to the wavelength in a specific wavelength region, and separates the light from the sample 100 by allowing the light to pass through and reflect the light; a light detector 24, which detects the amount of reflected light from the light reflected by the tilted dichroic mirror 22; a light detector 23, which detects the amount of transmitted light from the light that has passed through the tilted dichroic mirror 22; and a processing unit 27, which calculates the wavelength information based on the ratio of the amount of reflected light to the amount of transmitted light and outputs it.

[0064] In the height measurement device 1 of this embodiment, irradiation light consisting of multiple light beams, arranged in a direction intersecting the optical axis and having different wavelengths, is directed at sample 100 at an angle oblique to the height direction of sample 100. Wavelength information is derived from the light emitted from sample 100 and output, and the height of sample 100 is calculated based on the wavelength information. In this manner, since the irradiation light, consisting of multiple light beams that differ in a direction intersecting the optical axis, is directed at sample 100 from an oblique direction (at an oblique angle), the wavelength of the light irradiating sample 100 varies depending on the height of sample 100. Therefore, wavelength information is derived by detecting the light emitted from sample 100, and the height of sample 100 can be accurately calculated based on this wavelength information. In this embodiment, the height measurement device 1 uses an inclined dichroic mirror 22, whose transmittance and reflectance vary depending on wavelength, to separate light. The amount of reflected light is detected from the light reflected by the inclined dichroic mirror 22, and the amount of transmitted light is detected from the light that has passed through the inclined dichroic mirror 22. Wavelength information is then calculated based on the ratio of the amount of reflected light to the amount of transmitted light. For example, when deriving the wavelength of light from the object being measured based on the intensity of light captured by a color imaging element, the intensity of the light captured by the color imaging element varies depending on the color of the object being measured, leading to concerns that the accuracy of calculating the wavelength information of the light cannot be guaranteed. In this case, the accuracy of measuring the height of the object being measured based on the wavelength information will also be reduced. Regarding this point, in the height measuring device 1 of this embodiment, as described above, light is separated by a tilted dichroic mirror 22 whose transmittance and reflectance vary according to wavelength, and wavelength information is calculated based on the ratio of the amount of reflected light to the amount of transmitted light after separation. Therefore, the wavelength information of the light can be calculated with high accuracy without being affected by the color of the sample 100 itself. According to this height measuring device 1, the height of the sample 100 can be calculated with high accuracy based on the highly calculated wavelength information of the light. The calculation accuracy can be improved by, for example, correcting the characteristic strain of the filter or the transmittance of the lens. For example, when the "specific wavelength region" (the wavelength region in which the transmittance and reflectance vary according to the wavelength) of the tilted dichroic mirror 22 is designed to be 400nm to 700nm, the error can be set to about 1nm.

[0065] In the height measuring device 1 described above, the light detectors 23 and 24 may be line sensors. By using line sensors, for example, the sample 100 is moved to change the imaging line while each imaging line is accurately imaged. This allows the height of the sample 100 to be calculated with higher accuracy.

[0066] In the height measuring device 1, the light irradiation unit 10 may irradiate the sample 100 with irradiation light including a plurality of parallel light beams. By irradiating with parallel light, the correspondence between wavelength and height can be easily and appropriately derived, thereby allowing the height of the sample 100 to be calculated with higher accuracy.

[0067] In the height measuring device 1 described above, the light irradiation unit 10 may include a light source 11 that outputs white light; and spectroscopic elements 12 and 13 that split the white light output from the light source 11 to output irradiation light consisting of multiple light beams, each having wavelengths that differ from one another in a direction intersecting the optical axis. In this manner, by splitting the white light that includes all visible light rays into individual light beams, it is possible to easily and appropriately output irradiation light consisting of multiple light beams having different wavelengths.

[0068] The height measuring device 1 further includes a dark box 40 that blocks light other than the light irradiated to the sample 100 by the light irradiation unit 10. With this configuration, light irrelevant to height measurement is blocked, allowing the height of the sample 100 to be calculated with higher accuracy.

[0069] The height measuring device 1 may further include a belt conveyor 50 for moving the sample 100. This configuration allows the height of the entire sample 100 to be measured by deriving wavelength information of the entire sample 100 while changing the irradiation point of the irradiation light on the sample 100.

[0070] The height measurement method of this embodiment includes: a light irradiation step of irradiating sample 100 with irradiation light consisting of multiple light beams arranged in a direction intersecting the optical axis and having different wavelengths, at an angle inclined relative to the height direction of sample 100; a wavelength calculation step of calculating wavelength information of light from sample 100 based on the ratio of the amount of reflected light to the amount of transmitted light obtained by light detector 24 and light detector 23. The light detector 24 detects the amount of reflected light from light reflected by tilted dichroic mirror 22, and the light detector 23 detects the amount of transmitted light from light transmitted by tilted dichroic mirror 22. The tilted dichroic mirror 22 has a transmittance and reflectance that vary depending on the wavelength within a specific wavelength region and separates the light from sample 100 by transmitting and reflecting the light; and a height calculation step of calculating the height of sample 100 based on the wavelength information. According to this height measurement method, the height of sample 100 can be calculated with high accuracy based on the wavelength information of the light calculated with high accuracy.

[0071] In the height measurement method described above, in the light irradiation step, the irradiation point of the irradiation light on the sample 100 may be continuously changed by moving the sample 100, and in the height calculation step, the shape of the sample 100 may be derived by calculating the height corresponding to each irradiation point on the sample 100. In this height measurement method, the irradiation point of the irradiation light on the sample 100 is continuously changed, thereby enabling the height of the entire sample 100 to be measured, and the shape of the sample 100 to be appropriately derived based on the result of the height measurement.

[0072] Furthermore, as other technologies for measuring the shape (convexity and concavity) of the object to be measured, there are methods using structured light and methods using TOF (Time Of Flight) sensors. In the method using structured light, a straight line light is irradiated on the object to be measured and a camera is used to observe from an oblique direction, thereby measuring the shape of the object to be measured. However, this method requires the use of a two-dimensional sensor, so the measurement speed is slowed down and the processing load is increased compared to the case of using a one-dimensional sensor such as a line sensor. In addition, in the method using a TOF sensor, a pulsed light is irradiated on the object to be measured, and the concavity and convexity of the object to be measured is measured based on the time point when the pulsed light is output and the time required for the pulsed light to be reflected from the object to be measured. However, in this method, it is difficult to increase the pixel size due to the characteristic of measuring an extremely short time, and thus it is not suitable for observing small shapes. In this respect, the shape measurement method implemented by the height measurement device 1 of this embodiment can speed up the measurement speed and reduce the processing load compared to the comparative examples, and thus can also properly measure small shapes.

[0073]

Explanation of symbols

[0074] 1: Height measuring device

[0075] 10:Light irradiation part

[0076] 11: Light Source

[0077] 12,13: Spectral element

[0078] 20: Camera system (light detection unit)

[0079] 22: Tilt dichroic mirror (optical element)

[0080] 23, 24: Photodetectors (first photodetector, second photodetector)

[0081] 25,26: Bandpass filter

[0082] 27: Processing Department

[0083] 30: Control device (analysis unit)

[0084] 40: Camera Obscura

[0085] 50: Belt conveyor (transportation unit)

[0086] 100: Sample (measurement object).

Claims

1. A height measuring device comprising: a light irradiation unit for irradiating the object to be measured with irradiation light including a plurality of light beams arranged in a direction intersecting the optical axis direction and having different wavelengths, at an angle inclined with respect to a height direction of the object to be measured; a light detecting unit that detects light from the measurement object irradiated with the irradiation light and outputs wavelength information of the light; and an analyzing unit for calculating the height of the measurement object based on the wavelength information, The light detection unit has: an optical element whose transmittance and reflectance vary according to wavelength in a specific wavelength region and which separates light from the object by transmitting and reflecting the light; a first light detector for detecting an amount of reflected light from the light reflected by the optical element; a second photodetector for detecting an amount of transmitted light from the light having passed through the optical element; and A processing unit calculates and outputs the wavelength information based on a ratio of the reflected light amount to the transmitted light amount.

2. The height measuring device according to claim 1, wherein: The first photodetector and the second photodetector are line sensors.

3. The height measuring device according to claim 1 or 2, wherein: The light irradiation unit irradiates the measurement object with the irradiation light including the plurality of light beams as parallel light.

4. The height measuring device according to any one of claims 1 to 3, wherein: The light irradiation unit has: a light source that outputs white light; and The spectroscopic element splits the white light output from the light source to output the irradiation light including a plurality of light beams having wavelengths different from each other in a direction intersecting the optical axis direction.

5. The height measuring device according to any one of claims 1 to 4, wherein: The device further includes a dark box that blocks light other than the light irradiated to the object to be measured by the light irradiation unit.

6. The height measuring device according to any one of claims 1 to 5, wherein: The device further includes a conveying unit for moving the object to be measured.

7. A method for measuring height, comprising: a light irradiation step of irradiating the object to be measured with irradiation light including a plurality of light beams arranged in a direction intersecting the optical axis direction and having different wavelengths, at an angle inclined with respect to a height direction of the object to be measured; a wavelength calculation step of calculating wavelength information of light from the measurement object based on a ratio of an amount of reflected light to an amount of transmitted light obtained by an optical element having a transmittance and a reflectance that vary depending on the wavelength within a specific wavelength region and that separates the light from the object by transmitting and reflecting the light, a first photodetector that detects an amount of reflected light from the light reflected by the optical element, and a second photodetector that detects an amount of transmitted light from the light that has passed through the optical element; and A height calculation step is to calculate the height of the measurement object based on the wavelength information.

8. The height measurement method according to claim 7, wherein: In the light irradiation step, the irradiation point of the irradiation light in the measurement object is continuously changed by moving the measurement object. In the height calculation step, the shape of the measurement object is derived by calculating the height corresponding to each of the irradiation points in the measurement object.

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