Imaging unit, and measurement device

Abstract

To accurately derive a wavelength of light to acquire appropriate images.SOLUTION: A measurement device comprises: an inclined dichroic mirror 11 that transmits or reflects light from a sample in responce to a wavelength to thereby separate the light, in which an edge displacement width serving as a width of a wavelength range where transmittance and reflectance vary in responce to a change in the wavelength has a prescribed width,; a total reflection mirror 12 that reflects one of the transmitted light and reflected light in the inclined dichroic mirror; an imaging element 14 that images other of the transmitted light and reflected light in the inclined dichroic mirror in a first imaging area, and images the reflected one thereof in the total reflection mirror in a second imaging area different from the first imaging area; and a control device 80 that corrects images to be imaged in the first imaging area and second imaging area on the basis of an optical characteristic pertaining to the change in the transmittance and reflectance with respect to the wavelength in the inclined dichroic mirror.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an imaging unit and a measuring device.

Background Art

[0002] An imaging unit is known that separates light from an object according to wavelength and images the separated wavelengths in different imaging regions (see, for example, Patent Document 1). In the imaging unit described in Patent Document 1, a dichroic mirror, which is an optical element, separates the wavelengths.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The dichroic mirror described in Patent Document 1 separates light having a wavelength shorter than a certain wavelength and light having a longer wavelength based on that certain wavelength, and generally has a transmittance of 100% or 0% regardless of the wavelength. When using such a dichroic mirror, for example, when trying to separate light with a narrow wavelength width, it is conceivable that the desired separation cannot be achieved according to the wavelength. As a configuration that also supports the separation of such light with a narrow wavelength width, there is a dichroic mirror having a wide wavelength band (with an edge transition width) in which the transmittance (and reflectance) changes according to the change in wavelength. A dichroic mirror having an edge transition width can appropriately separate light with a narrow wavelength width.

[0005] Here, in a dichroic mirror having an edge transition width, for example, the optical characteristics change according to the incident angle of light. As a result, in an imaging unit using a dichroic mirror having an edge transition width, the wavelength of light cannot be accurately derived, and there is a possibility that a correct captured image cannot be obtained.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide an imaging unit and a measuring device that can accurately derive the wavelength of light and acquire an appropriate image.

Means for Solving the Problems

[0007] An imaging unit according to an aspect of the present invention separates light from an object by transmitting or reflecting it according to the wavelength, and has an edge transition width, which is the width of a wavelength band in which the transmittance and reflectance change according to the change in wavelength, having a predetermined width. A separation optical element, a reflection optical element that reflects one of the light transmitted or reflected by the separation optical element, and the other of the light transmitted or reflected by the separation optical element is imaged in a first imaging region, and the light reflected by the reflection optical element is imaged in a second imaging region different from the first imaging region. And a processing unit that corrects the images captured in the first imaging region and the second imaging region based on the optical characteristics related to the changes in the transmittance and reflectance with respect to the wavelength in the separation optical element.

[0008] In the imaging unit according to an aspect of the present invention, a separation optical element having an edge transition width having a predetermined width is used, and the captured image is corrected based on the optical characteristics related to the changes in the transmittance and reflectance with respect to the wavelength in the separation optical element. When a separation optical element having an edge transition width having a predetermined width is used, light having a narrow wavelength width can be appropriately separated. However, for example, the optical characteristics change depending on the incident angle of light with respect to the separation optical element. As a result, it may not be possible to accurately derive the wavelength of light and acquire an appropriate image. In this regard, in the imaging unit according to an aspect of the present invention, based on the optical characteristics related to the changes in the transmittance and reflectance with respect to the wavelength, that is, the characteristics related to the edge transition width of the separation optical element, the images captured in the first and second imaging regions are corrected. Therefore, it is possible to obtain a captured image corrected in consideration of the optical characteristics peculiar to the separation optical element having an edge transition width. As a result, the wavelengths of the light separated by the separation optical element (the light imaged in the first and second imaging regions) can be appropriately derived, and an appropriate (accurate) image can be acquired.

[0009] The processing unit stores in advance correction data considering the optical characteristics related to the changes in the transmittance and reflectance with respect to the wavelength in the separation optical element, and may correct the images captured in the first imaging region and the second imaging region using the correction data. According to such a configuration, based on the correction data stored in advance, the captured images can be easily and appropriately corrected.

[0010] The processing unit may receive correction data considering the optical characteristics related to the changes in the transmittance and reflectance with respect to the wavelength in the separation optical element, and correct the images captured in the first imaging region and the second imaging region using the correction data. According to such a configuration, based on the correction data obtained, for example, by software execution or input from the outside such as the Internet, the captured images can be appropriately corrected without preparing the correction data in advance.

[0011] The processing unit may correct the color spots caused by the incident angle of light on the separation optical element. When a separation optical element having an edge transition width is used, the optical characteristics of the separation optical element change according to the incident angle with respect to the separation optical element, and color spots are generated in the captured image, which is a problem. In this regard, by correcting the color spots, an appropriate image with reduced color spots can be obtained.

[0012] The processing unit may correct the shift of the detected wavelength caused by the boundary between the wavelength band where the transmittance and reflectance change according to the change in wavelength and the wavelength band where they do not change. Such a boundary has optical characteristics different from those of the wavelength band where the transmittance and the like change according to the change in wavelength. Therefore, if the wavelength is derived using the same calculation formula as that of the wavelength band where the transmittance and the like change according to the change in wavelength, the derived result may be different from the original wavelength. In this regard, by correcting the shift of the detected wavelength caused by such a boundary, the wavelength of light can be accurately derived and an appropriate image can be obtained.

[0013] The imaging unit may be a single image sensor having a first imaging region and a second imaging region. Thereby, a plurality of captured images can be obtained with a simple configuration using a single image sensor.

[0014] The measuring device according to one aspect of the present invention includes the above-described imaging unit and an analysis unit that analyzes the processing result in the imaging unit including the image corrected by the processing unit.

Advantages of the Invention

[0015] According to the present invention, the wavelength of light can be accurately derived and an appropriate image can be acquired.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0017] 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 redundant descriptions are omitted.

[0018] FIG. 1 is a plan view schematically showing a measuring device 1 according to this embodiment. The measuring device 1 is a camera unit (imaging unit) configured to be able to image a sample. The measuring device 1 separates light (for example, observation light) from the sample according to wavelength components, and images the light of each wavelength component by imaging elements 14, 24, 34 corresponding to the respective wavelength components. The measuring device 1 determines the quality of the sample by analyzing the images (imaging results) captured by the imaging elements 14, 24, 34. The sample may be, for example, a light-emitting element such as an LED, a mini-LED, a μ-LED, an SLD element, a laser element, a vertical-cavity surface-emitting laser (VCSEL), an OLED, or a light-emitting element that adjusts the emission wavelength with a fluorescent substance containing nanodots or the like. When the sample is a light-emitting element, determining the quality of the sample means, for example, determining the quality of the sample based on spot color information among a plurality of light-emitting elements.

[0019] As shown in FIG. 1, the measuring device 1 includes a camera system 2 and a control device 80 (processing unit, analysis unit). Details of the camera system 2 will be described with reference to FIG. 2 as well. FIG. 1 is a plan view of the measuring device 1 including the camera system 2, and FIG. 2 is a side view of the camera system 2.

[0020] As shown in FIGS. 1 and 2, the camera system 2 includes a first imaging unit 10, a second imaging unit 20, a third imaging unit 30, an infinity-corrected lens 40, a dichroic mirror 50, and a dichroic mirror 60. Although not shown in FIGS. 1 and 2, the camera system 2 includes an objective lens (not shown) for observing a sample and one or more band-pass filters (not shown) for removing light outside a desired wavelength range. The camera system 2 separates light into wavelength components corresponding to generally the three primary colors and images the light of each wavelength component. For example, the first imaging unit 10 images light in the range of 380 to 500 nm including a blue wavelength component. Also, the second imaging unit 20 images light in the range of 500 to 650 nm including a green wavelength component. Also, the third imaging unit 30 images light in the range of 650 to 830 nm including a red wavelength component.

[0021] The infinity-corrected lens 40 is a collimator lens that converts light from an incident sample into parallel light. The infinity-corrected lens 40 is aberration-corrected so that parallel light is obtained. The parallel light output from the infinity-corrected lens 40 enters the dichroic mirror 50.

[0022] The dichroic mirror 50 is a mirror made of a special optical material and separates light from the sample by transmitting or reflecting it according to the wavelength. The dichroic mirror 50 reflects light of a specific wavelength, for example, and transmits light of other wavelengths. Specifically, the dichroic mirror 50 reflects light having a wavelength of less than 500 nm, for example, and transmits light of other wavelengths (light having a wavelength of 500 nm or more). The light reflected by the dichroic mirror 50 is guided to the first imaging unit 10. The light transmitted through the dichroic mirror 50 enters the dichroic mirror 60.

[0023] The dichroic mirror 60 is a mirror made of a special optical material, which separates the light from the sample by transmitting or reflecting it according to the wavelength. The dichroic mirror 60 reflects light of a specific wavelength, for example, and transmits light of other wavelengths. Specifically, the dichroic mirror 60 reflects light with a wavelength of 500 nm or more and less than 650 nm, for example, and transmits light of other wavelengths (light with a wavelength of 650 nm or more). The light reflected by the dichroic mirror 60 is guided to the second imaging unit 20. The light transmitted through the dichroic mirror 60 is guided to the third imaging unit 30.

[0024] The first imaging unit 10 includes an inclined dichroic mirror 11 (separating optical element), a total reflection mirror 12 (reflecting optical element), an imaging lens 13, and an imaging element 14 (imaging unit).

[0025] The inclined dichroic mirror 11 is a mirror made of a special optical material, which separates the light from the sample by transmitting or reflecting it according to the wavelength. The inclined dichroic mirror 11 reflects light of a specific wavelength, for example, and transmits light of other wavelengths. Specifically, the inclined dichroic mirror 11 reflects light with a wavelength of 380 to 500 nm among the light with a wavelength of less than 500 nm reflected by the dichroic mirror 50, and transmits light of other wavelengths. FIG. 3 is a diagram for explaining the spectrum of light and the characteristics of the inclined dichroic mirror 11. In FIG. 3, the horizontal axis represents the wavelength, and the vertical axis represents the spectral intensity (in the case of the spectrum of light) and the transmittance (in the case of the inclined dichroic mirror 11). As shown in the characteristic X4 of the inclined dichroic mirror 11 in FIG. 3, in the inclined dichroic mirror 11, in a specific wavelength band (wavelength band of wavelength λ 1 ~λ 2 ), the transmittance (and reflectance) of light changes gently according to the change in wavelength, and in wavelength bands other than the specific wavelength band (that is, on the lower wavelength side than wavelength λ 1 and on the higher wavelength side than wavelength λ 2On the longer wavelength side), the light transmittance (and reflectance) is constant regardless of the wavelength change. In other words, in a specific wavelength band (wavelength λ 1 ~λ 2 ), the light transmittance changes monotonically (the reflectance decreases monotonically) in response to the wavelength change. Since the transmittance and the reflectance have a negative correlation, where one changes in the increasing direction while the other changes in the decreasing direction, hereinafter, there may be cases where only "transmittance" is described without describing "transmittance (and reflectance)". Note that "the light transmittance is constant regardless of the wavelength change" includes not only the case where it is completely constant but also cases where, for example, the change in transmittance with respect to a wavelength change of 1 nm is 0.1% or less. At wavelengths shorter than wavelength λ 1 the light transmittance is generally 0% regardless of the wavelength change, and at wavelengths longer than wavelength λ 2 the light transmittance is generally 100% regardless of the wavelength change. Note that "the light transmittance is generally 0%" includes a transmittance of about 0% + 10%, and "the light transmittance is generally 100%" includes a transmittance of about 100% - 10%. Also, hereinafter, the width of the wavelength band in which the light transmittance changes in response to the wavelength change may be described as the "edge transition width". As described above, the inclined dichroic mirror 11 is a separation optical element having an edge transition width, which is the width of the wavelength band in which the transmittance changes in response to the wavelength change, of a predetermined width (the width of wavelength λ 1 ~λ 2 ).

[0026] The total reflection mirror 12 is an optical element that reflects the light reflected by the inclined dichroic mirror 11 in the direction of the imaging lens 13.

[0027] The imaging lens 13 is a lens that forms images of the light transmitted through the inclined dichroic mirror 11 and the light reflected by the inclined dichroic mirror 11 and further reflected by the total reflection mirror 12, and guides these lights to the imaging device 14.

[0028] The imaging element 14 images the light transmitted through the inclined dichroic mirror 11 in the first imaging region, and also images the light reflected by the inclined dichroic mirror 11 and further reflected by the total reflection mirror 12 in a second imaging region different from the first imaging region. The imaging element 14 images the light transmitted through the inclined dichroic mirror 11 and the light reflected by the total reflection mirror 12 by detecting the image formed by the imaging lens 13. The imaging element 14 is an imaging element for imaging light in the range of 380 to 500 nm, and is, for example, an area image sensor such as a CCD or a MOS. Also, the imaging element 14 may be constituted by a line sensor or a TDI (Time Delay Integration) sensor. In the present embodiment, the imaging element 14 will be described as a single imaging element having a first imaging region and a second imaging region, but the imaging element related to the first imaging region and the imaging element related to the second imaging region may be provided separately (two sets may be provided). In this case, two sets of imaging lenses are also provided corresponding to the imaging elements. The imaging element 14 outputs the image, which is the imaging result, to the control device 80.

[0029] The second imaging unit 20 includes a configuration similar to the configuration included in the first imaging unit 10, and includes an inclined dichroic mirror 21 (separating optical element), a total reflection mirror 22 (reflecting optical element), an imaging lens 23, and an imaging element 24 (imaging unit). The inclined dichroic mirror 21 has the same configuration as the inclined dichroic mirror 11 of the first imaging unit 10, except that it reflects light in the range of 500 to 650 nm among the light having a wavelength of 500 nm or more and less than 650 nm reflected by the dichroic mirror 60 and transmits light of other wavelengths. Also, the imaging element 24 has the same configuration as the imaging element 14 of the first imaging unit 10, except that it is an imaging element for imaging light in the range of 500 to 650 nm.

[0030] The third imaging unit 30 includes a configuration similar to that included in the first imaging unit 10, and includes an inclined dichroic mirror 31 (separating optical element), a total reflection mirror 32 (reflecting optical element), an imaging lens 33, and an imaging element 34 (imaging unit). The inclined dichroic mirror 31 has the same configuration as the inclined dichroic mirror 11 of the first imaging unit 10, except that it reflects light with a wavelength of 650 to 830 nm among the light with a wavelength of 650 nm or more that has passed through the dichroic mirror 60 and transmits light with other wavelengths. Further, the imaging element 24 has the same configuration as the imaging element 14 of the first imaging unit 10, except that it is an imaging element for imaging light with a wavelength of 650 to 830 nm.

[0031] Returning to FIG. 1, the control device 80 is a computer, and physically includes a memory such as a RAM and a ROM, a processor (arithmetic circuit) such as a CPU, a communication interface, and a storage unit such as a hard disk. The control device 80 functions by executing a program stored in the memory by the CPU of the computer system. The control device 80 may be configured by a microcomputer or an FPGA.

[0032] Based on the imaging results obtained in each of the first imaging unit 10, the second imaging unit 20, and the third imaging unit 30, the control device 80 calculates and outputs the center of gravity of the emission wavelength based on the light amount of each pixel (each pixel of the image formed in the field of view) of the image that is the imaging result. Hereinafter, an example of the calculation principle of the center of gravity of the emission wavelength will be described in detail with reference to FIG. 2. Note that since the calculation principle of the center of gravity of the emission wavelength based on the imaging results of the first imaging unit 10, the second imaging unit 20, and the third imaging unit 30 is the same, hereinafter, the calculation of the center of gravity of the emission wavelength based on the imaging result of the first imaging unit 10 will be described as an example.

[0033] As described above, the inclined dichroic mirror 11 reflects all light on the lower wavelength side than the wavelength λ 1 and transmits all light on the higher wavelength side than the wavelength λ 2 and has a wavelength λ 1 ~λ 2Assume that in the wavelength band of, the transmittance of light changes linearly with the wavelength. In this case, for wavelengths λ 1 , λ 2 , the transmittance h(λ) is expressed by the following equation (1), and the reflectance 1 - h(λ) is expressed by the following equation (2). h(λ)=(λ - λ 1 ) / (λ 2 - λ 1 ) (1) 1 - h(λ)=(λ 2 - λ) / (λ 2 - λ 1 ) (2)

[0034] Also, it is obvious that the wavelength λ 50% at which the reflectance is 50% is expressed by the following equation (3). λ 50% =(λ 2 + λ 1 ) / 2 (3)

[0035] Suppose a certain emission spectrum f(λ) is shown by the waveform X2 in FIG. 3, is between λ 1 and λ 2 , and can be ignored at wavelengths shorter than λ 1 and longer than λ 2 (for example, when the characteristics of a band - pass filter (not shown) are shown by the waveform X1 in FIG. 3 and the wavelength band of the emission spectrum f(λ) is limited). Assuming that the amount of reflected light is equal to the amount of transmitted light, the following equation (4) holds. ∫f(λ)h(λ)dλ = ∫f(λ)(1 - h(λ))dλ (4) When equation (4) is transformed, it becomes the following equation (5). 2∫f(λ)h(λ)dλ = ∫f(λ)dλ (5)

[0036] Substituting equation (1) into equation (5), 2∫f(λ)(λ - λ 1 ) / (λ 2 - λ 1 )dλ = ∫f(λ)dλ And further dividing both sides by 2∫f(λ)dλ / (λ 2 - λ 1 ), ∫f(λ)(λ - λ 1 )dλ / ∫f(λ)dλ = (λ 2 - λ 1 ) / 2 ∫f(λ)λdλ / ∫f(λ)dλ = (λ 2 + λ 1 ) / 2 (6) becomes as follows.

[0037] Considering equation (3), it is obvious that the right - hand side of equation (6) is λ 50% , and the left - hand side generally represents the centroid of an arbitrary function f(λ). Let the left - hand side of equation (6) be λ f . From the above, for any spectrum passing through a dichroic mirror with a linearly sloping transmittance with respect to wavelength, when the transmitted light amount and the reflected light amount are equal, the centroid λ f of the spectrum is represented by λ 50% .

[0038] Next, consider the second emission spectrum g(λ) (waveform X3 in Figure 3). For the emission spectrum g(λ) as well, the entire spectrum is included between λ 1 and λ 2 . Now, calculate the difference between the differences of the transmitted and reflected lights normalized for the emission spectra f(λ) and g(λ). Let the transmitted light of f(λ) be T f , the reflected light be R f , the total light amount be A f , and the difference between the transmitted and reflected lights be D f . Also, let the transmitted light of g(λ) be T g , the reflected light be R g , the total light amount be A g , and the difference between the transmitted and reflected lights be D g . Also, let the centroid of g(λ) be λ g . At this time, T f , R f , T g , R g are measured values, and A f , A g , D f , D g are values that can be directly calculated from the measured values. These respective values are also shown by the following equations. Tf =∫f(λ)h(λ)dλ = ∫f(λ)(λ - λ 1 ) / (λ 2 - λ 1 )dλ (7) T g =∫g(λ)h(λ)dλ = ∫g(λ)(λ - λ 1 ) / (λ 2 - λ 1 )dλ (8) R f =∫f(λ)(1 - h(λ))dλ = ∫f(λ)(λ 2 - λ) / (λ 2 - λ 1 )dλ (9) R g =∫g(λ)(1 - h(λ))dλ = ∫g(λ)(λ 2 - λ) / (λ 2 - λ 1 )dλ (10) A f =∫f(λ)dλ (11) A g =∫g(λ)dλ (12) D f = T f - R f = 2 / (λ 2 - λ 1 ) * ∫λf(λ)dλ - (λ 2 + λ 1 ) / (λ 2 - λ 1 ) * ∫f(λ)dλ (13) D g = T g - R g = 2 / (λ 2 - λ 1 ) * ∫λg(λ)dλ - (λ 2 + λ 1 ) / (λ 2 - λ 1 ) * ∫g(λ)dλ (14)

[0039] Here, normalizing the difference between the transmitted light and the reflected light means dividing D f by A f , and dividing D g by A gis equivalent to dividing by them. Let the difference between them be R, then the following equation (15) holds. R = D g / A g - D f / A f ={∫g(λ)λdλ / ∫g(λ)dλ - ∫f(λ)λdλ / ∫f(λ)dλ} * 2 / (λ 2 - λ 1 ) = 2(λ g - λ f ) / (λ 2 - λ 1 ) (15)

[0040] Let the difference between the wavelength centroids λ f of the emission spectrum f(λ) and the wavelength centroid λ g of the emission spectrum g(λ) be δλ, then the following equations (16) and (17) hold. R = 2δλ / (λ 2 - λ 1 ) (16) δλ = R(λ 2 - λ 1 ) / 2 (17) As described above, it has been shown that the difference between the centroids of any two spectra f(λ) and g(λ) can be obtained from calculations considering the transmitted light amount and the reflected light amount.

[0041] And when the centroid of f(λ) is λ 50% , the reflected light amount and the transmitted light amount are equal, so D f becomes 0. That is, the wavelength centroid λ g of any spectrum g(λ) is shown by the following equation (18). λ g = δλ + λ 50% (18)

[0042] Thus, the centroid of the emission spectrum can be calculated from the design value of the filter, the transmitted light amount, and the reflected light amount. Based on the above principle, the centroid of the wavelength of the light incident on each pixel can be obtained with high precision.

[0043] Here, when obtaining the center of gravity of the light wavelength, for example, it is conceivable that the derivation accuracy may decrease due to the following factors. First, since the periphery of the lens of the imaging device 14 is dimmed, there is a possibility that the center of gravity of the original light wavelength cannot be appropriately obtained for the pixels in such locations. Second, the optical characteristics of the inclined dichroic mirror 11 change depending on the incident angle of light. Depending on the incident angle of light (the position of the pixel within the field of view), there is a possibility that the center of gravity of the light wavelength cannot be appropriately obtained (color spots caused by the incident angle occur). Third, there is a possibility that a wavelength shift may occur due to the sensitivity of the lens and the imaging device 14. For these problems, for example, it is conceivable to calculate in advance the incident angle of light to the inclined dichroic mirror 11 and perform correction according to the incident angle (solution to the second problem above). Also, for example, it is conceivable to perform shading correction by irradiating a uniform monochromatic laser beam onto an irradiation surface (white object) and performing gain correction for each pixel so that it becomes uniform (solution to the first and second problems above). Also, by suppressing the inclination of the inclined dichroic mirror 11 and reflecting light at an angle closer to 90 degrees, it is conceivable to appropriately obtain the center of gravity of the light wavelength. Furthermore, in the present embodiment, the following correction is performed.

[0044] That is, the control device 80 may correct the images captured in the first imaging region and the second imaging region of the imaging device 14 based on the optical characteristics related to the changes in the transmittance and reflectance with respect to the wavelength in the inclined dichroic mirror 11. The control device 80 may, for example, store in advance correction data considering the optical characteristics related to the changes in the transmittance and reflectance with respect to the wavelength in the inclined dichroic mirror 11, and correct the images captured in the first imaging region and the second imaging region using the correction data. The control device 80 may receive correction data considering the optical characteristics related to the changes in the transmittance and reflectance with respect to the wavelength in the inclined dichroic mirror 11, and correct the images captured in the first imaging region and the second imaging region using the correction data. The control device 80 may receive the above-described correction data by software being executed or input from the outside such as the Internet.

[0045] Referring to FIGS. 4 and 5, the generation of the above-described correction data will be described. FIG. 4 is a diagram schematically showing a correction unit 100 that generates correction data. FIG. 5 is a graph for explaining the correction of a calculated wavelength (described later). Regarding the first imaging unit 10, the second imaging unit 20, and the third imaging unit 30, the processes related to the generation of correction data are the same. Therefore, hereinafter, the process related to the generation of correction data for the first imaging unit 10 will be described. As shown in FIG. 4, the correction unit 100 includes a light source 101, an optical fiber 102, an FC adapter 103, a diffuser plate 104, and an objective lens 105. The correction unit 100 is used when generating correction data for the camera system 2 of the measuring device 1. It is assumed that each component (see FIG. 2) of the above-described camera system 2 is provided downstream of the objective lens 105 of the correction unit 100 (not shown in FIG. 4).

[0046] The light source 101 is, for example, a monochromatic / narrow-band light source whose wavelength can be changed. Alternatively, the light source 101 may be a plurality of laser light sources having different wavelengths, or may be an SLD / LED, or may include a white light source and a band-pass filter. The light source 101 can select, for example, five or more wavelengths at least within the tilt range of the at least tilt dichroic mirror 11 (the range in which the light transmittance (and reflectance) changes gently according to the change in wavelength). The light emitted from the light source 101 is guided to the objective lens 105 via the optical fiber 102 and the diffuser plate 104. Thereby, the light from the light source 101 can be observed by the objective lens 105.

[0047] When generating correction data, with the correction unit 100 set as described above, while changing the wavelength of the light emitted from the light source 101, images in the first imaging region and the second imaging region of the imaging device 14 are acquired at each wavelength. It is also possible to remove the effects of offsets due to background light and the like, and gain unevenness. The wavelength intervals may be approximately equally spaced. Then, based on the images of the first imaging region and the second imaging region, the control device 80 derives the wavelength centroid (calculated wavelength) at each wavelength. As shown in FIG. 5(a), the control device 80 takes the wavelength λ of the light source 101 on the horizontal axis and the calculated wavelength λ' on the vertical axis. Ideally, it is considered that there is a linear relationship between the wavelength λ of the light source 101 and the calculated wavelength λ'. However, in the example shown in FIG. 5(a), particularly on the low wavelength side, the calculated wavelength λ' deviates significantly from the ideal value. Further, as shown in FIG. 5(b), the control device 80 takes the calculated wavelength λ' on the horizontal axis and the calculated wavelength λ' - the wavelength λ of the light source 101 on the vertical axis. Then, the control device 80 obtains the approximate curve N of the graph in FIG. 5(b) up to about the fourth order by, for example, the least squares method, etc., so that the calculated wavelength λ' on the low wavelength side that deviates significantly from the ideal value as described above can be appropriately corrected. Specifically, the control device 80 obtains the corrected calculated wavelength based on the calculated wavelength λ' and the fourth-order equation of the least squares method described above. For example, the control device 80 obtains the corrected calculated wavelength by adding the calculated wavelength λ' and the value of the fourth-order equation.

[0048] The control device 80 corrects, for example, the color unevenness caused by the incident angle of light on the tilt dichroic mirror 11 by using the correction data described above. Further, the control device 80 corrects, for example, the shift of the detection wavelength (calculated wavelength) caused by the boundary between the wavelength band in which the transmittance and reflectance change and the wavelength band in which they do not change in response to the change in wavelength by using the correction data described above. Such a boundary (near λ in FIG. 3 and λ 1 in the vicinity of and λ 2The wavelength band in the vicinity of [[ID=]] may have optical characteristics different from those of the wavelength band in which the transmittance of the tilt dichroic mirror 11 changes according to the change in wavelength. Therefore, for such a boundary, if the wavelength is derived using the same calculation formula as the wavelength band in which the transmittance changes according to the change in wavelength, the calculation result may be different from the original wavelength. In this regard, by correcting the calculated wavelength λ´ deviated from the ideal value using the above-described correction data, the deviation of the detected wavelength caused by the boundary can be appropriately corrected. The control device 80 determines the quality of the sample by analyzing the processing result including the corrected image.

[0049] Next, a correction method using the above-described correction data will be described with reference to FIG. 6. FIG. 6 is a flowchart of the correction method. As a premise for implementing the processing of FIG. 6, a correction unit 100 is installed upstream (front stage) of the camera system 2.

[0050] As shown in FIG. 6, first, while changing the wavelength of the light emitted from the light source 101, for each of a plurality of measurement wavelengths, an image 1 in the first imaging region of the imaging device 14 and an image 2 in the second imaging region are acquired (step S1).

[0051] Subsequently, a calculated wavelength is obtained from the image 1 and the image 2 acquired in step S1 (step S2). Specifically, based on the above-described equations (1) to (18), the wavelength centroid (calculated wavelength) at each wavelength is obtained.

[0052] Subsequently, for each measurement wavelength, the difference between the measurement wavelength and the calculated wavelength is obtained (step S3). Then, the calculated wavelength is corrected by obtaining, for example, the least squares method up to about the fourth order so that the difference becomes minimum (step S4). The above is the correction method.

[0053] Note that the present invention is not limited to calculating the wavelength centroid using the correction method of the above-described embodiment. For example, a conversion map may be generated in advance by calculating a table including correction data, and the wavelength centroid may be calculated based on the ratio of the light entering the pixel corresponding to this conversion map.

[0054] Next, the operation and effect of this embodiment will be described.

[0055] The measuring device 1 according to this embodiment separates light from a sample by transmitting or reflecting it according to the wavelength, and has an edge transition width, which is the width of a wavelength band in which the transmittance and reflectance change according to the change in wavelength, having a predetermined width. It includes a tilt dichroic mirror 11, a total reflection mirror 12 that reflects one of the lights transmitted or reflected by the tilt dichroic mirror 11, and the other of the lights transmitted or reflected by the tilt dichroic mirror 11 is imaged in a first imaging region, and the light reflected by the total reflection mirror 12 is imaged in a second imaging region different from the first imaging region. And an imaging element 14, and a control device 80 that corrects the images captured in the first imaging region and the second imaging region based on the optical characteristics related to the changes in the transmittance and reflectance with respect to the wavelength in the tilt dichroic mirror 11.

[0056] In the measuring device 1, a tilt dichroic mirror 11 having an edge transition width with a predetermined width is used, and the captured images are corrected based on the optical characteristics related to the changes in the transmittance and reflectance with respect to the wavelength in the tilt dichroic mirror 11. When a tilt dichroic mirror 11 having an edge transition width with a predetermined width is used, although light with a narrow wavelength width can be appropriately separated, for example, the optical characteristics change depending on the incident angle of the light with respect to the tilt dichroic mirror 11. As a result, there is a possibility that the wavelength of the light cannot be accurately derived and an appropriate image cannot be obtained. In this regard, in the measuring device 1 according to this embodiment, based on the optical characteristics related to the changes in the transmittance and reflectance with respect to the wavelength, that is, the characteristics related to the edge transition width of the tilt dichroic mirror 11, the images captured in the first and second imaging regions are corrected. Therefore, it is possible to obtain a captured image corrected in consideration of the optical characteristics peculiar to the tilt dichroic mirror 11 having an edge transition width. As a result, the wavelengths of the light separated by the tilt dichroic mirror 11 (the light imaged in the first and second imaging regions) can be appropriately derived, and an appropriate (accurate) image can be obtained.

[0057] The control device 80 stores in advance correction data considering the optical characteristics related to the changes in the transmittance and reflectance with respect to the wavelength in the tilt dichroic mirror 11, and may correct the images captured in the first imaging region and the second imaging region using the correction data. According to such a configuration, based on the correction data stored in advance, the captured images can be easily and appropriately corrected.

[0058] The control device 80 may receive correction data considering the optical characteristics related to the changes in the transmittance and reflectance with respect to the wavelength in the tilt dichroic mirror 11, and correct the images captured in the first imaging region and the second imaging region using the correction data. According to such a configuration, based on the correction data obtained, for example, by software execution or input from the outside such as the Internet, the captured images can be appropriately corrected without preparing the correction data in advance.

[0059] The control device 80 may correct the color spots caused by the incident angle of light on the tilt dichroic mirror 11. When a separation optical element having an edge transition width is used, the optical characteristics of the tilt dichroic mirror 11 change according to the incident angle on the tilt dichroic mirror 11, and the problem is that color spots occur in the captured image. In this regard, by correcting the color spots, an appropriate image with reduced color spots can be obtained.

[0060] The control device 80 may correct the shift of the detected wavelength caused by the boundary between the wavelength band where the transmittance and reflectance change according to the change in wavelength and the wavelength band where they do not change. Such a boundary has optical characteristics different from those of the wavelength band where the transmittance and the like change according to the change in wavelength. Therefore, if the wavelength is derived using the same calculation formula as that of the wavelength band where the transmittance and the like change according to the change in wavelength, the derived result may be different from the original wavelength. In this regard, by correcting the shift of the detected wavelength caused by such a boundary, the wavelength of light can be accurately derived and an appropriate image can be obtained.

[0061] The imaging device 14 may be a single imaging device having a first imaging region and a second imaging region. Thereby, a plurality of captured images can be obtained with a simple configuration using a single imaging device.

[0062] As described above, the embodiments of the present invention have been described, but the present invention is not limited to the above embodiments. For example, in the above embodiments, it has been described that the light from the sample is separated into light including a red wavelength component, light including a green wavelength component, and light including a blue wavelength component (RGB) by the dichroic mirrors 50 and 60 and each is imaged by a different imaging unit, but the present invention is not limited to this. That is, the light from the observation object (sample) may be imaged without being separated into the three colors of RGB.

[0063] In such a configuration, the inclined dichroic mirror provided in front of the area sensor which is an imaging device has a wavelength band (edge transition width) in which the light transmittance (and reflectance) changes according to the change in wavelength corresponding to all of the three colors of RGB, and is, for example, 400 to 900 nm.

[0064] FIG. 7 is a diagram for explaining the characteristics of the inclined dichroic mirror according to the modification. In FIG. 7, the horizontal axis represents the wavelength, and the vertical axis represents the transmittance (in the case of the inclined dichroic mirror) and the spectral intensity (in the case of the spectrum of light). In the example shown in FIG. 7, in a specific wavelength band (the wavelength band of 400 to 900 nm), the light transmittance (and reflectance) changes gently according to the change in wavelength, and in the wavelength bands other than the specific wavelength band (that is, the lower wavelength side than 400 nm and the higher wavelength side than 900 nm), the light transmittance (and reflectance) is constant regardless of the change in wavelength. As shown in FIG. 7, in the inclined dichroic mirror, the wavelength band (edge transition width) in which the light transmittance (and reflectance) changes according to the change in wavelength includes all of the wavelength band of the light including the red wavelength component (the wavelength band shown on the right side in FIG. 7), the wavelength band of the light including the green wavelength component (the wavelength band shown in the center in FIG. 7), and the wavelength band of the light including the blue wavelength component (the wavelength band shown on the left side in FIG. 7).

[0065] An example of a camera system (imaging unit) using an inclined dichroic mirror having the characteristics shown in FIG. 7 will be described with reference to FIG. 8. FIG. 8 is a diagram schematically showing a camera system 90A according to a modified example.

[0066] As shown in FIG. 8, the camera system 90A includes an inclined dichroic mirror 91 (separating optical element), a finite focus lens (finite conjugate lens) 92A, a band-pass filter 93, an area sensor 94 (second imaging unit), and an area sensor 95 (first imaging unit).

[0067] The finite focus lens 92A is a lens that condenses light (emission) from a sample 150 (object) that is the observation target. The distances from the finite focus lens 92A to the area sensor 94 and from the finite focus lens 92A to the area sensor 95 are set to predetermined values. The light that has passed through the finite focus lens 92A is incident on the inclined dichroic mirror 91.

[0068] The band-pass filter 93 is provided, for example, in the front stage (upstream) of the finite focus lens 92A and is a filter that removes light outside a predetermined wavelength range. The band-pass filter 93 removes light having a wavelength outside the range of, for example, 400 to 900 nm. A plurality of band-pass filters 93 may be provided. The band-pass filter 93 may be provided in the region indicated by the broken line in FIG. 8, that is, in the region of the rear stage (downstream) of the finite focus lens 92A and the front stage (upstream) of the inclined dichroic mirror 91, or may be provided in the region of the front stage (upstream) of the area sensors 94 and 95 and the rear stage (downstream) of the inclined dichroic mirror 91. When band-pass filters 93 are provided in the front stages of the area sensors 94 and 95, respectively, the two band-pass filters 93, 93 have the same characteristics as each other. Further, the camera system 90A may be provided with a plurality of band-pass filters 93 configured to be switchable according to the light from the sample 150. In this case, the plurality of band-pass filters 93 each have a different wavelength band to be filtered from each other (details will be described later).

[0069] The inclined dichroic mirror 91 is a mirror made of a special optical material, which separates the light from the sample 150 by transmitting and reflecting it according to the wavelength, and is a mirror in which the transmittance and reflectance change in a predetermined wavelength range. In the inclined dichroic mirror 91, as shown in FIG. 7, the wavelength band (edge transition width) in which the light transmittance (and reflectance) changes according to the change in wavelength includes all of the wavelength bands of the light including the red wavelength component, the light including the green wavelength component, and the light including the blue wavelength component. That is, the "predetermined wavelength range" of the inclined dichroic mirror 91 described above includes all of the wavelength bands of the light including the red wavelength component, the light including the green wavelength component, and the light including the blue wavelength component.

[0070] The area sensor 94 images the light reflected by the inclined dichroic mirror 91. The area sensor 95 images the light transmitted by the inclined dichroic mirror 91. The wavelength ranges in which the area sensors 94 and 95 have sensitivity correspond to the wavelength band (edge transition width) in which the light transmittance (and reflectance) changes according to the change in wavelength in the inclined dichroic mirror 91. The area sensors 94 and 95 are, for example, monochrome sensors or color sensors (details will be described later). The imaging results (images) by the area sensors 94 and 95 are output to a control device (not shown). The processing for obtaining the wavelength centroid, the correction processing, and the determination processing of the quality of the sample in the control device (not shown) may be the same as the processing in the control device 80 described in the embodiment, for example.

[0071] The correction process will be described. When light is incident obliquely (when it is not at the pupil position of the objective lens), the light incident on each pixel passes through only a part rather than the whole, and there is a possibility that the transmitted wavelength will shift due to non-uniformity patches in the in-plane of the tilt dichroic mirror 91 and the band-pass filter 93. On the contrary, when light from multiple directions is incident on the tilt dichroic mirror 91, if the wavelength characteristics are distorted from a straight line, there is an effect of smoothing the wavelength characteristics. As a countermeasure against the non-uniformity patches in the in-plane of the tilt dichroic mirror 91 and the band-pass filter 93, it is conceivable to measure and correct the shift amount from the incident wavelength by previously uniformly irradiating light of the same wavelength within the field of view and calculating the in-plane wavelength distribution.

[0072] As specific embodiments of the above-described camera system 90A, for example, the three embodiments described below can be considered.

[0073] First, the camera system 90A may be configured to include one type of band-pass filter 93 (the range of the wavelength band to be filtered is one type) and area sensors 94 and 95 which are monochrome sensors. In this case, the band-pass filter 93 removes light having a wavelength outside the range of, for example, 400 to 900 nm. In such a configuration, RGB three colors may be mixed in the light incident on the area sensors 94 and 95. In this case, a control device (not shown) obtains the averaged wavelength centroid in the light of the wavelength band transmitted through the band-pass filter 93 (light in which RGB three colors are mixed). Also, when light in mutually different wavelength bands (light of each of RGB) is spatially separated (when they do not overlap on the image), the control device (not shown) can obtain the wavelength centroid with high accuracy for each wavelength band. Specifically, regarding the wavelength centroid of the color of each pixel of a TV, a display, etc., it can be obtained with high accuracy in units of nm according to this embodiment.

[0074] Second, the camera system 90A may include a plurality of types of band-pass filters 93 having different wavelength bands to be filtered from each other, and area sensors 94 and 95 which are monochrome sensors. In this case, the plurality of types of band-pass filters 93 are provided so as to be insertable and removable (switchable) in accordance with the light emission from the sample 150. In such a configuration, when light emission having a broad spectrum (with overlap) is output from the sample 150, by switching and using the plurality of types of band-pass filters 93, a control device (not shown) can obtain the wavelength centroid of only the light in a specific wavelength band (the wavelength band corresponding to each band-pass filter 93). That is, when a band-pass filter 93 that removes light having wavelengths other than the wavelength band of the red wavelength component (for example, 700 to 900 nm) is set, the control device (not shown) obtains the wavelength centroid of only the red wavelength component, and when a band-pass filter 93 that removes light having wavelengths other than the wavelength band of the green wavelength component (for example, 550 to 700 nm) is set, the control device obtains the wavelength centroid of only the green wavelength component, and when a band-pass filter 93 that removes light having wavelengths other than the wavelength band of the blue wavelength component (for example, 400 to 550 nm) is set, the control device obtains the wavelength centroid of only the blue wavelength component. Specifically, for example, for a light source that realizes a white LED using a blue LED and a fluorescent agent, with the second configuration, it is possible to obtain the wavelength centroid of only the blue LED and the wavelength centroid of only the fluorescent agent.

[0075] Thirdly, the camera system 90A may include a band-pass filter 93 of one type (the range of the wavelength band to be filtered is one type) and area sensors 94 and 95 that are color sensors. In this case, the band-pass filter 93 removes light having wavelengths outside the range of, for example, 400 to 900 nm. In such a configuration, RGB three colors may be mixed in the light incident on the area sensors 94 and 95 that are color sensors. A Bayer filter (a filter of three RGB colors) is mounted on each pixel of the color sensor. Thereby, each light-receiving element of the area sensors 94 and 95 that are color sensors can acquire light having only a red wavelength component, light having only a green wavelength component, and light having only a blue wavelength component, respectively. According to such a configuration, for a color represented by the superposition of a plurality of wavelengths, the wavelength centroid can be appropriately obtained (that is, the inspection can be appropriately performed). Usually, the colors of printing and light emission are formed by the superposition of three RGB colors according to the human eye. For each color superposed in this way, by calculating the wavelength centroid, the mixed color can be accurately inspected. Note that as the imaging unit, a hyperspectral camera may be further combined to simultaneously inspect the centroids of more wavelengths. The hyperspectral camera is composed of, for example, a spectroscope and an imaging unit.

[0076] Another example of a camera system (imaging unit) using an inclined dichroic mirror having the characteristics shown in FIG. 7 will be described with reference to FIG. 9. FIG. 9 is a diagram schematically showing a camera system 90B according to another modification. Hereinafter, differences from the configuration shown in FIG. 8 will be mainly described.

[0077] As shown in FIG. 9, the camera system 90B includes an inclined dichroic mirror 91 (separating optical element), an infinite focus lens (infinity-corrected lens) 92B, a band-pass filter 93, an area sensor 94 (second imaging unit), an area sensor 95 (first imaging unit), and imaging lenses 96 and 97. The inclined dichroic mirror 91 and the area sensors 94 and 95 are the same as these configurations in the camera system 90A described above.

[0078] The infinity focus lens 92B is a collimator lens that converts light (emission) from a sample 150 (object) to be observed into parallel light. The infinity focus lens 92B is aberration-corrected so that parallel light can be obtained. The parallel light output from the infinity focus lens 92B enters the inclined dichroic mirror 91.

[0079] The imaging lens 96 is a lens that forms an image of the light transmitted through the inclined dichroic mirror 91 on the area sensor 94. The imaging lens 97 is a lens that forms an image of the light transmitted through the inclined dichroic mirror 91 on the area sensor 95.

[0080] The band-pass filter 93 is provided, for example, at the subsequent stage (downstream) of the infinity focus lens 92B and the previous stage (upstream) of the inclined dichroic mirror 91, and is a filter that removes light outside a predetermined wavelength range. The band-pass filter 93 removes light having a wavelength outside the range of, for example, 400 to 900 nm. A plurality of band-pass filters 93 may be provided. The band-pass filter 93 may be provided in the region indicated by the broken line in FIG. 9, that is, in the region at the previous stage (upstream) of the infinity focus lens 92B, or may be provided in the region at the previous stage (upstream) of the area sensors 94 and 95 and the subsequent stage (downstream) of the imaging lenses 96 and 97, or may be provided in the region at the previous stage (upstream) of the imaging lenses 96 and 97 and the subsequent stage (downstream) of the inclined dichroic mirror 91. Note that the band-pass filters 93 provided at the previous stage of the area sensors 94 and 95 have the same characteristics as each other, and the band-pass filters 93 provided at the previous stage of the imaging lenses 96 and 97 have the same characteristics as each other.

[0081] Regarding such a camera system 90B using the infinity focus lens 92B, as a specific aspect, the above-described three aspects similar to those of the camera system 90A can be considered.

[0082] As described above, the camera system (imaging unit) according to the modification example separates light from an object by transmitting and reflecting it according to the wavelength, and includes a separation optical element whose transmittance and reflectance change within a predetermined wavelength range, a first imaging unit that images the light transmitted through the separation optical element, and a second imaging unit that images the light reflected by the separation optical element.

[0083] In this way, by using a separation optical element whose transmittance and reflectance change according to the wavelength, it is possible to appropriately separate light with a narrow wavelength width, and it is possible to appropriately obtain the wavelength centroid according to the imaging result in the imaging unit. Further, unlike the aspect described in the embodiment, since the light that has passed through the separation optical element can be directly received by the imaging unit (the first imaging unit and the second imaging unit), miniaturization of the camera system can be realized.

[0084] Also, in the camera system according to the modification example, the wavelength ranges in which the first imaging unit and the second imaging unit have sensitivity correspond to the wavelength range in which the transmittance and reflectance change in the separation optical element. According to such a configuration, it is possible to appropriately acquire the change (difference) in wavelength from the imaging result in the imaging unit, and it is possible to appropriately obtain the wavelength centroid.

[0085] In addition, the camera system according to the modification example includes a plurality of types of band-pass filters configured to be switchable according to light from an object. For example, when light emission with a broad spectrum (with overlap) is output from the object, by switching and using a plurality of types of band-pass filters, a control device (not shown) can obtain the wavelength centroid of light only in a specific wavelength band (a wavelength band corresponding to each band-pass filter). That is, when a band-pass filter that removes light with wavelengths other than the wavelength band of the red wavelength component is set, the control device (not shown) obtains the wavelength centroid of only the red wavelength component. When a band-pass filter that removes light with wavelengths other than the wavelength band of the green wavelength component is set, the control device obtains the wavelength centroid of only the green wavelength component. When a band-pass filter that removes light with wavelengths other than the wavelength band of the blue wavelength component is set, the control device can obtain the wavelength centroid of only the blue wavelength component.

Explanation of Signs

[0086] 1…Measuring device (imaging unit), 11, 21, 31…Tilt dichroic mirror (separating optical element), 12, 22, 32…Total reflection mirror (reflective optical element), 14, 24, 34…Image sensor (imaging unit), 80…Control device (processing unit, analysis unit).

Claims

1. a separation optical element that separates light from an object by transmitting or reflecting the light according to the wavelength, and has a predetermined wavelength range that is the width of a wavelength band in which the transmittance and reflectance change linearly according to the change in wavelength; a first area sensor that captures an image of light transmitted through the separation optical element; a second area sensor that captures an image of the light reflected by the separation optical element; A filter provided in a stage preceding or succeeding the separation optical element; The filter removes light outside the predetermined wavelength range at the separation optical element.

2. The imaging unit according to claim 1 , wherein the filter is provided in a stage preceding the separation optical element.

3. 3. The imaging unit according to claim 2, wherein the filters are a plurality of bandpass filters each filtering a different wavelength band.

4. 4. The imaging unit of claim 3, wherein the plurality of bandpass filters include a bandpass filter that removes light of wavelengths other than the wavelength band of a red wavelength component, a bandpass filter that removes light of wavelengths other than the wavelength band of a green wavelength component, and a bandpass filter that removes light of wavelengths other than the wavelength band of a blue wavelength component.

5. the filter includes a first band-pass filter provided downstream of the separation optical element and upstream of a first area sensor, and a second band-pass filter provided downstream of the separation optical element and upstream of a second area sensor, 2. The imaging unit according to claim 1, wherein the first band-pass filter and the second band-pass filter have the same characteristics.

6. The imaging unit according to any one of claims 1 to 5, wherein the filter removes light outside the range of 400 to 900 nm.

7. 6. The imaging unit according to claim 1, wherein the first area sensor and the second area sensor are both monochrome sensors.

8. 6. The imaging unit according to claim 1, further comprising a processing unit that corrects color spots caused by an incident angle of light with respect to the separation optical element and the filter.

Images