Imaging unit and measuring 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 technology]

[0002] An imaging unit is known that separates light from an object according to its 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, wavelengths are separated by a dichroic mirror, which is an optical element. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2014-235332 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The dichroic mirror described in Patent Document 1 separates light with wavelengths shorter than a certain wavelength from light with wavelengths longer than a certain wavelength, and its transmittance is generally 100% or 0% regardless of wavelength. When using such a dichroic mirror, for example, if one tries to separate light with a narrow wavelength range, it is possible that the desired separation cannot be achieved depending on the wavelength. As a configuration that can handle the separation of such narrow wavelength range light, there is a dichroic mirror with a wide wavelength band (having an edge shift range) in which the transmittance (and reflectance) changes according to the change in wavelength. A dichroic mirror with an edge shift range can appropriately separate light with a narrow wavelength range.

[0005] In dichroic mirrors with edge shift, the optical properties change depending on the angle of incidence of light, for example. As a result, imaging units using dichroic mirrors with edge shift may not be able to accurately determine the wavelength of light, and may not be able to obtain accurate images.

[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 capable of accurately deriving the wavelength of light and acquiring 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 lights transmitted or reflected by the separation optical element, and the other of the lights 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. An imaging unit, and a processing unit that corrects images captured in the first imaging region and the second imaging region based on optical characteristics related to changes in 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 with a predetermined width is used, and the captured image is corrected based on optical characteristics related to changes in transmittance and reflectance with respect to the wavelength in the separation optical element. When a separation optical element having an edge transition width with a predetermined width is used, light with 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, so that the wavelength of light may not be accurately derived and an appropriate image may not be obtained. In this regard, in the imaging unit according to an aspect of the present invention, based on the optical characteristics related to changes in 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 lights separated by the separation optical element (the lights imaged in the first and second imaging regions) can be appropriately derived, and an appropriate (accurate) image can be obtained.

[0009] The processing unit stores in advance correction data that takes into account 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 that takes into account 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 the execution of software 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 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.

[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 etc. 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 etc. change according to the change in wavelength, there is a possibility that the derived result will 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. This allows for obtaining multiple images with a simple configuration using a single image sensor.

[0014] A measuring device according to one aspect of the present invention comprises the above-described imaging unit and an analysis unit that analyzes the processing results in the imaging unit, including an image corrected by a processing unit. [Effects of the Invention]

[0015] According to the present invention, the wavelength of light can be accurately determined and an appropriate image can be obtained. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic plan view showing a measuring device according to an embodiment of the present invention. [Figure 2] This is a schematic side view showing the camera system included in the measuring device shown in Figure 1. [Figure 3] This diagram illustrates the properties of light spectra and tilted dichroic mirrors. [Figure 4] This is a schematic diagram showing the correction unit. [Figure 5] This graph explains the correction of the calculated wavelength. [Figure 6] This is a flowchart of the correction method. [Figure 7] This figure illustrates the characteristics of a modified inclined dichroic mirror. [Figure 8] This diagram schematically shows a camera system relating to a modified example. [Figure 9] This diagram schematically shows a camera system relating to a modified example. [Modes for carrying out the invention]

[0017] Embodiments of the present invention will be described in detail below with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and redundant descriptions are omitted.

[0018] Figure 1 is a schematic plan view of the measuring device 1 according to this embodiment. The measuring device 1 is a camera unit (imaging unit) configured to image a sample. The measuring device 1 separates light from the sample (e.g., observation light) according to its wavelength components and images the light of each wavelength component using image sensors 14, 24, and 34 corresponding to each wavelength component. The measuring device 1 determines the quality of the sample by analyzing the images (imaging results) captured by the image sensors 14, 24, and 34. The sample may be a light-emitting element such as an LED, mini-LED, μLED, SLD element, laser element, vertical-cavity-cell-scale (VCSEL), or an OLED, or a light-emitting element whose emission wavelength is adjusted by a fluorescent material containing nanodots, etc. 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 color spot information between multiple light-emitting elements.

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

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

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

[0022] The dichroic mirror 50 is a mirror made using a special optical material, which separates light from a sample by transmitting or reflecting it according to its wavelength. For example, the dichroic mirror 50 reflects light of a specific wavelength while transmitting light of other wavelengths. Specifically, for example, the dichroic mirror 50 reflects light with a wavelength of less than 500 nm while transmitting light of other wavelengths (light with 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 that has passed through the dichroic mirror 50 is incident on the dichroic mirror 60.

[0023] The dichroic mirror 60 is a mirror made using a special optical material, which separates light from a sample by transmitting or reflecting it according to its wavelength. For example, the dichroic mirror 60 reflects light of a specific wavelength while transmitting light of other wavelengths. Specifically, for example, the dichroic mirror 60 reflects light with a wavelength of 500 nm or more and less than 650 nm, while transmitting 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 is composed of an inclined dichroic mirror 11 (separation optical element), a total reflection mirror 12 (reflection optical element), an imaging lens 13, and an image sensor 14 (imaging unit).

[0025] The tilted dichroic mirror 11 is a mirror made using a special optical material, and separates light from a sample by transmitting or reflecting it according to its wavelength. For example, the tilted dichroic mirror 11 reflects light of a specific wavelength while transmitting light of other wavelengths. Specifically, the tilted dichroic mirror 11 reflects light between 380 and 500 nm from the light below 500 nm reflected by the dichroic mirror 50, while transmitting light of other wavelengths. Figure 3 illustrates the light spectrum and the characteristics of the tilted dichroic mirror 11. In Figure 3, the horizontal axis represents wavelength, and the vertical axis represents spectral intensity (in the case of the light spectrum) and transmittance (in the case of the tilted dichroic mirror 11). As shown in the characteristic X4 of the tilted dichroic mirror 11 in Figure 3, in the tilted dichroic mirror 11, the transmittance (and reflectance) of light changes gradually in a specific wavelength band (wavelength λ1 to λ2), while in wavelength bands other than the specific wavelength band (i.e., wavelengths lower than λ1 and wavelengths higher than λ2), the transmittance (and reflectance) of light remains constant regardless of the change in wavelength. In other words, in a specific wavelength band (wavelength λ1 to λ2), the transmittance of light increases monotonically (and the reflectance decreases monotonically) in response to the change in wavelength. Since transmittance and reflectance have a negative correlation, where an increase in one leads to a decrease in the other, the term "transmittance (and reflectance)" may be omitted and simply referred to as "transmittance" below. Note that "the transmittance of light remains constant regardless of the change in wavelength" includes not only cases where it is perfectly constant, but also cases where, for example, the change in transmittance for a change of 1 nm in wavelength is 0.1% or less. At wavelengths lower than λ1, the light transmittance is approximately 0% regardless of the change in wavelength, and at wavelengths higher than λ2, the light transmittance is approximately 100% regardless of the change in wavelength. Note that "light transmittance is approximately 0%" includes transmittances of approximately 0% + 10%, and "light transmittance is approximately 100%" includes transmittances of approximately 100% - 10%. Furthermore, in the following, the width of the wavelength band in which light transmittance changes according to the change in wavelength may be explained as the "edge shift width."As described above, the tilted dichroic mirror 11 is a separating optical element having an edge shift width, which is the width of the wavelength band in which the transmittance changes according to the change in wavelength, with a predetermined width (width of wavelengths λ1 to λ2).

[0026] The total internal 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 images the light transmitted through the inclined dichroic mirror 11, and the light reflected by the inclined dichroic mirror 11 and then further reflected by the total reflection mirror 12, and guides this light to the image sensor 14.

[0028] The image sensor 14 captures light transmitted through the tilted dichroic mirror 11 in a first imaging region, and captures light reflected by the tilted dichroic mirror 11 and further reflected by the total reflection mirror 12 in a second imaging region different from the first imaging region. The image sensor 14 captures the light transmitted through the tilted dichroic mirror 11 and the light reflected by the total reflection mirror 12 by detecting the image formed by the imaging lens 13. The image sensor 14 is an image sensor for capturing light in the 380-500 nm range, and is, for example, an area image sensor such as a CCD or MOS. The image sensor 14 may also be composed of a line sensor or a TDI (Time Delay Integration) sensor. In this embodiment, the image sensor 14 is described as a single image sensor having a first imaging region and a second imaging region, but the image sensor for the first imaging region and the image sensor for 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 image sensors. The image sensor 14 outputs the image, which is the result of the image acquisition, to the control device 80.

[0029] The second imaging unit 20 includes the same configuration as the first imaging unit 10, and comprises a tilted dichroic mirror 21 (separation optical element), a total reflection mirror 22 (reflection optical element), an imaging lens 23, and an image sensor 24 (imaging unit). The tilted dichroic mirror 21 has the same configuration as the tilted dichroic mirror 11 of the first imaging unit 10, except that it reflects light between 500 and 650 nm from the light between 500 nm and 650 nm reflected by the dichroic mirror 60, while transmitting light of other wavelengths. The image sensor 24 has the same configuration as the image sensor 14 of the first imaging unit 10, except that it is an image sensor for imaging light between 500 and 650 nm.

[0030] The third imaging unit 30 includes the same configuration as the first imaging unit 10, and comprises a tilted dichroic mirror 31 (separation optical element), a total reflection mirror 32 (reflection optical element), an imaging lens 33, and an image sensor 34 (imaging unit). The tilted dichroic mirror 31 has the same configuration as the tilted dichroic mirror 11 of the first imaging unit 10, except that it reflects light in the 650-830nm range that has passed through the dichroic mirror 60, while transmitting light of other wavelengths. The image sensor 24 has the same configuration as the image sensor 14 of the first imaging unit 10, except that it is an image sensor for imaging light in the 650-830nm range.

[0031] Returning to Figure 1, the control device 80 is a computer, and physically comprises memory such as RAM and ROM, a processor (arithmetic circuit) such as a CPU, a communication interface, and storage such as a hard disk. The control device 80 functions by executing programs stored in memory using the CPU of the computer system. The control device 80 may also be composed of a microcontroller or an FPGA.

[0032] The control device 80 calculates and outputs the emission wavelength centroid based on the amount of light in each pixel of the image (each pixel of the image formed within the field of view) of the image obtained from the first imaging unit 10, the second imaging unit 20, and the third imaging unit 30. Below, an example of the calculation principle of the emission wavelength centroid will be explained in detail with reference to Figure 2. Note that the calculation principle of the emission wavelength centroid 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, so below we will explain using the calculation of the emission wavelength centroid based on the imaging results of the first imaging unit 10 as an example.

[0033] As described above, the tilted dichroic mirror 11 reflects all light at wavelengths lower than λ1 and transmits all light at wavelengths higher than λ2, and the transmittance of light changes linearly with wavelength in the wavelength band λ1 to λ2. In this case, the transmittance h(λ) in relation to wavelengths λ1 and λ2 is given by equation (1) below, and the reflectance 1-h(λ) is given by equation (2) below. h(λ)=(λ-λ1) / (λ2-λ1) (1) 1-h(λ)=(λ2-λ) / (λ2-λ1) (2)

[0034] Furthermore, the wavelength λ at which the reflectance is 50% 50% It is clear that this can be shown by equation (3) below. λ 50% =(λ²+λ¹) / 2 (3)

[0035] If an emission spectrum f(λ) is shown by waveform X2 in Figure 3, and lies between λ1 and λ2, and wavelengths shorter than λ1 and longer than λ2 are negligible (for example, if the characteristics of a bandpass filter (not shown) are shown by waveform X1 in Figure 3, and the wavelength band of the emission spectrum f(λ) is limited), then assuming that the amount of reflected light and the amount of transmitted light are equal, the following equation (4) holds. ∫f(λ)h(λ)dλ=∫f(λ)(1-h(λ))dλ (4) Transforming equation (4) yields equation (5) below. 2∫f(λ)h(λ)dλ=∫f(λ)dλ (5)

[0036] Substituting equation (1) into equation (5), 2∫f(λ)(λ - λ1) / (λ2 - λ1)dλ = ∫f(λ)dλ and then dividing both sides by 2∫f(λ)dλ / (λ2 - λ1), ∫f(λ)(λ - λ1)dλ / ∫f(λ)dλ = (λ2 - λ1) / 2 ∫f(λ)λdλ / ∫f(λ)dλ = (λ2 + λ1) / 2 (6) is obtained.

[0037] Considering equation (3), it is obvious that the right side of equation (6) is λ 50% and the left side generally becomes the centroid of an arbitrary function f(λ). Let the left side of equation (6) be λ f . From the above, for any arbitrary spectrum passing through a dichroic mirror with a linearly sloped 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 FIG. 3). For the emission spectrum g(λ) as well, the entire spectrum is included between λ1 and λ2. 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 , Dg These are values ​​that can be calculated directly from the measured values. Each of these values ​​can also be expressed by the following formula. T f =∫f(λ)h(λ)dλ=∫f(λ)(λ-λ1) / (λ2-λ1)dλ (7) T g =∫g(λ)h(λ)dλ=∫g(λ)(λ-λ1) / (λ2-λ1)dλ (8) R f =∫f(λ)(1-h(λ))dλ=∫f(λ)(λ2-λ) / (λ2-λ1)dλ (9) R g =∫g(λ)(1-h(λ))dλ=∫g(λ)(λ2-λ) / (λ2-λ1)dλ (10) A f =∫f(λ)dλ (11) A g =∫g(λ)dλ (12) D f =T f -R f =2 / (λ2-λ1)*∫λf(λ)dλ-(λ2+λ1) / (λ2-λ1)*∫f(λ)dλ (13) D g =T g -R g =2 / (λ2-λ1)*∫λg(λ)dλ-(λ2+λ1) / (λ2-λ1)*∫g(λ)dλ (14)

[0039] Here, normalizing the difference between transmitted and reflected light means D f to A f , D g to A g This is equivalent to dividing by . If we let R be the difference between them, then equation (15) below holds. R=D g / A g -D f / A f ={∫g(λ)λdλ / ∫g(λ)dλ-∫f(λ)λdλ / ∫f(λ)dλ}*2 / (λ2-λ1) =2(λ g -λ f ) / (λ2-λ1) (15)

[0040] Wavelength centroid λ of emission spectrum f(λ) f and the wavelength centroid λ of the emission spectrum g(λ) g If the difference between them is δλ, then equations (16) and (17) below hold. R = 2δλ / (λ² - λ¹) (16) δλ = R(λ2 - λ1) / 2 (17) As shown above, the difference between the centroids of two arbitrary spectra f(λ) and g(λ) can be obtained from calculations that take into account the amount of transmitted and reflected light.

[0041] And the centroid of f(λ) is λ 50% In this case, the amount of reflected light and the amount of transmitted light are equal, so D f This becomes 0. In other words, the wavelength centroid λ of any spectrum g(λ) g This is shown by equation (18) below. λ g =δλ+λ 50% (18)

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

[0043] Here, when determining the centroid of the wavelength of light, the derivation accuracy may decrease due to factors such as the following: Firstly, since the area around the lens of the image sensor 14 is attenuated, it may not be possible to properly determine the true centroid of the wavelength of light for pixels in such areas. Secondly, since the optical properties of the tilted dichroic mirror 11 change with the angle of incidence of light, it may not be possible to properly determine the centroid of the wavelength of light depending on the angle of incidence of light (the position of the pixel in the field of view) (color unevenness caused by the angle of incidence may occur). Thirdly, wavelength shift may occur due to the sensitivity of the lens and the image sensor 14. To address these issues, for example, it is possible to pre-calculate the angle of incidence of light to the tilted dichroic mirror 11 and perform a correction according to the angle of incidence (solution to the second issue above). Alternatively, for example, it is possible to perform shading correction by shining a uniform monochromatic laser beam onto the irradiation surface (a white object) and performing gain correction for each pixel so that it becomes uniform (solution to the first and second issues above). Furthermore, by reducing the tilt of the inclined dichroic mirror 11 and reflecting light at an angle closer to 90 degrees, it is possible to appropriately determine the centroid of the wavelength of light. In addition, the following corrections are made in this embodiment.

[0044] In other words, the control device 80 may correct the images captured in the first imaging area and the second imaging area of ​​the image sensor 14 based on the optical characteristics relating to the change in transmittance and reflectance with respect to wavelength in the tilted dichroic mirror 11. The control device 80 may, for example, pre-store correction data that takes into account the optical characteristics relating to the change in transmittance and reflectance with respect to wavelength in the tilted dichroic mirror 11, and use this correction data to correct the images captured in the first imaging area and the second imaging area. The control device 80 may receive correction data that takes into account the optical characteristics relating to the change in transmittance and reflectance with respect to wavelength in the tilted dichroic mirror 11, and use this correction data to correct the images captured in the first imaging area and the second imaging area. The control device 80 may receive the above-mentioned correction data when software is executed or when it is input from an external source such as the Internet.

[0045] The generation of the correction data described above will be explained with reference to Figures 4 and 5. Figure 4 is a schematic diagram of the correction unit 100 that generates the correction data. Figure 5 is a graph for explaining the correction of the calculated wavelength (described later). The process for generating the correction data is the same for the first imaging unit 10, the second imaging unit 20, and the third imaging unit 30, so the process for generating the correction data for the first imaging unit 10 will be explained below. As shown in Figure 4, the correction unit 100 is composed of 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. The components of the camera system 2 described above (see Figure 2) are provided downstream of the objective lens 105 of the correction unit 100 (not shown in Figure 4).

[0046] The light source 101 is, for example, a monochromatic / narrowband light source with a changeable wavelength. Alternatively, the light source 101 may be a plurality of laser light sources with different wavelengths, an SLD / LED, or a combination of a white light source and a bandpass filter. The light source 101 can select, for example, five or more wavelengths within the tilt range of the tilt dichroic mirror 11 (a range in which the transmittance (and reflectance) of light changes gradually 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. This makes the light from the light source 101 observable by the objective lens 105.

[0047] When generating correction data, with the correction unit 100 described above set up, images are acquired in the first and second imaging regions of the image sensor 14 at each wavelength while changing the wavelength of light emitted from the light source 101. The effects of offset and gain unevenness due to background light, etc., may be removed. The wavelength intervals may be approximately equal. Then, based on the images of the first and second imaging regions, the control device 80 derives the wavelength centroid (calculated wavelength) at each wavelength. As shown in Figure 5(a), the control device 80 plots the wavelength λ of the light source 101 on the horizontal axis and the calculated wavelength λ' on the vertical axis. Ideally, the wavelength λ of the light source 101 and the calculated wavelength λ' are expected to have a linear relationship, but in the example shown in Figure 5(a), the calculated wavelength λ' deviates significantly from the ideal value, especially at lower wavelengths. Furthermore, as shown in Figure 5(b), the control device 80 plots the calculated wavelength λ' on the horizontal axis and the calculated wavelength λ' minus the wavelength λ of the light source 101 on the vertical axis. The control device 80 can then appropriately correct the calculated wavelength λ' on the low-wavelength side, which deviates significantly from the ideal value described above, by determining the approximate curve N of the graph in Figure 5(b) to about the fourth order, for example, using the least squares method. Specifically, the control device 80 determines 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 determines the corrected calculated wavelength by adding the calculated wavelength λ' and the value of the fourth-order equation.

[0048] The control device 80 corrects color variations caused by the angle of incidence of light on the tilted dichroic mirror 11, for example, by using the correction data described above. The control device 80 also corrects the deviation of the detected wavelength (calculated wavelength) caused by the boundary between wavelength bands where transmittance and reflectance change in response to wavelength changes and wavelength bands where they do not, for example, by using the correction data described above. Such boundaries (wavelength bands near λ1 and λ2 in Figure 3) may have different optical characteristics than the wavelength bands where the transmittance of the tilted dichroic mirror 11 changes in response to wavelength changes. Therefore, if the wavelength is derived using the same calculation formula as for the wavelength bands where transmittance changes in response to wavelength changes, the calculation result may differ from the actual wavelength. In this regard, by correcting the calculated wavelength λ' that deviates from the ideal value using the correction data described above, 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 results, including the corrected image.

[0049] Next, the correction method using the correction data described above will be explained with reference to Figure 6. Figure 6 is a flowchart of the correction method. As a prerequisite for the process shown in Figure 6, the correction unit 100 is installed upstream (before) the camera system 2.

[0050] As shown in Figure 6, first, while changing the wavelength of light emitted from the light source 101, image 1 in the first imaging area and image 2 in the second imaging area of ​​the image sensor 14 are acquired for each of the multiple measurement wavelengths (step S1).

[0051] Next, the calculated wavelength is determined from images 1 and 2 acquired in step S1 (step S2). Specifically, the wavelength centroid (calculated wavelength) at each wavelength is determined based on equations (1) to (18) described above.

[0052] Next, for each measured wavelength, the difference between the measured wavelength and the calculated wavelength is calculated (Step S3). Then, the calculated wavelength is corrected by applying a method such as the least squares method up to about the fourth order to minimize the difference (Step S4). This completes the correction method.

[0053] It should be noted that the present invention is not limited to calculating the wavelength centroid using the correction method described above. For example, a transformation map may be generated in advance by calculating a table that includes correction data, and the wavelength centroid may be calculated based on the ratio of light entering the corresponding pixels in this transformation map.

[0054] Next, the effects and advantages of this embodiment will be described.

[0055] The measuring device 1 according to this embodiment includes: an inclined dichroic mirror 11 that separates light from a sample by transmitting or reflecting it according to its wavelength and has a predetermined edge shift width which is the width of a wavelength band in which the transmittance and reflectance change according to the change in wavelength; a total reflection mirror 12 that reflects one of the light transmitted or reflected by the inclined dichroic mirror 11; an image sensor 14 that images the other of the light transmitted or reflected by the inclined dichroic mirror 11 in a first imaging area and images the light reflected by the total reflection mirror 12 in a second imaging area different from the first imaging area; and a control device 80 that corrects the images captured in the first imaging area and the second imaging area based on the optical characteristics relating to the change in transmittance and reflectance with respect to wavelength in the inclined dichroic mirror 11.

[0056] In the measuring device 1, an inclined dichroic mirror 11 having a predetermined edge shift width is used, and the captured image is corrected based on the optical characteristics of the inclined dichroic mirror 11 related to the change in transmittance and reflectance with respect to wavelength. When an inclined dichroic mirror 11 with a predetermined edge shift width is used, although it is possible to appropriately separate light with a narrow wavelength range, the optical characteristics change depending on the angle of incidence of light to the inclined dichroic mirror 11, for example, which may prevent the accurate derivation of the wavelength of light and the acquisition of an appropriate image. In this regard, in the measuring device 1 according to this embodiment, the images captured in the first and second imaging regions are corrected based on the optical characteristics related to the change in transmittance and reflectance with respect to wavelength, that is, the characteristics related to the edge shift width of the inclined dichroic mirror 11. Therefore, it is possible to acquire an image corrected considering the unique optical characteristics of the inclined dichroic mirror 11 having an edge shift width. As a result, the wavelength of the light separated by the inclined dichroic mirror 11 (light captured in the first and second imaging regions) can be appropriately derived, and an appropriate (accurate) image can be acquired.

[0057] The control device 80 pre-stores correction data that takes into account the optical characteristics related to the change in transmittance and reflectance with respect to wavelength in the tilted dichroic mirror 11, and may use this correction data to correct the images captured in the first imaging area and the second imaging area. With this configuration, the captured images can be easily and appropriately corrected based on the pre-stored correction data.

[0058] The control device 80 may receive correction data that takes into account the optical characteristics related to the change in transmittance and reflectance with respect to wavelength in the tilted dichroic mirror 11, and use this correction data to correct the images captured in the first imaging area and the second imaging area. With this configuration, the captured images can be appropriately corrected without having to prepare correction data in advance, based on correction data obtained, for example, by the execution of software or input from an external source such as the internet.

[0059] The control device 80 may correct color variations caused by the angle of incidence of light on the tilted dichroic mirror 11. When a separating optical element with an edge shift width is used, the optical properties of the tilted dichroic mirror 11 change depending on the angle of incidence on the tilted dichroic mirror 11, which causes color variations in the captured image. In this regard, by correcting the color variations, it is possible to obtain an appropriate image with reduced color variations.

[0060] The control device 80 may correct the deviation in the detected wavelength caused by the boundary between wavelength bands where transmittance and reflectance change in response to wavelength changes and wavelength bands where they do not change. Such boundaries have different optical properties than wavelength bands where transmittance and other properties change in response to wavelength changes. Therefore, if the wavelength is derived using the same calculation formula as for wavelength bands where transmittance and other properties change in response to wavelength changes, the derived result may differ from the original wavelength. In this respect, by correcting the deviation in the detected wavelength caused by such boundaries, the wavelength of light can be accurately derived and an appropriate image can be obtained.

[0061] The image sensor 14 may be a single image sensor having a first imaging region and a second imaging region. This allows multiple images to be obtained with a simple configuration using a single image sensor.

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

[0063] In this configuration, the tilted dichroic mirror placed in front of the area sensor, which is the image sensor, has a wavelength range (edge ​​transition width) in which the transmittance (and reflectance) of light changes in accordance with the change in wavelength, which corresponds to all three RGB colors, for example, 400 to 900 nm.

[0064] Figure 7 illustrates the characteristics of a modified tilted dichroic mirror. In Figure 7, the horizontal axis represents wavelength, and the vertical axis represents transmittance (in the case of a tilted dichroic mirror) and spectral intensity (in the case of a light spectrum). In the example shown in Figure 7, in a specific wavelength band (the 400-900 nm wavelength band), the transmittance (and reflectance) of light changes gradually in accordance with the change in wavelength, while in wavelength bands other than this specific wavelength band (i.e., wavelengths lower than 400 nm and wavelengths higher than 900 nm), the transmittance (and reflectance) of light remains constant regardless of the change in wavelength. As shown in Figure 7, in this tilted dichroic mirror, the wavelength band (edge ​​transition width) in which the transmittance (and reflectance) of light changes in accordance with the change in wavelength includes all of the wavelength bands containing red wavelength components (wavelength bands shown on the right in Figure 7), wavelength bands containing green wavelength components (wavelength bands shown in the center in Figure 7), and wavelength bands containing blue wavelength components (wavelength bands shown on the left in Figure 7).

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

[0066] As shown in Figure 8, the camera system 90A includes an inclined dichroic mirror 91 (separation optical element), a finite focus lens (finite distance correction lens) 92A, a bandpass 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 focuses light (emission) from the sample 150 (object) being observed. The distance from the finite focus lens 92A to the area sensor 94, and the distance from the finite focus lens 92A to the area sensor 95 are predetermined values. The light that has passed through the finite focus lens 92A is incident on the inclined dichroic mirror 91.

[0068] The bandpass filter 93 is, for example, provided upstream of the finite focus lens 92A and is a filter that removes light outside a predetermined wavelength range. The bandpass filter 93 removes light with wavelengths outside the range of 400 to 900 nm, for example. Multiple bandpass filters 93 may be provided. The bandpass filter 93 may be provided in the region shown by the dashed line in Figure 8, that is, the region downstream of the finite focus lens 92A and upstream of the inclined dichroic mirror 91, or it may be provided in the region upstream of the area sensors 94 and 95 and downstream of the inclined dichroic mirror 91. When a bandpass filter 93 is provided upstream of each of the area sensors 94 and 95, the two bandpass filters 93, 93 are made to have the same characteristics. In addition, the camera system 90A may be equipped with multiple bandpass filters 93 configured to be switchable according to the light from the sample 150. In this case, each of the multiple bandpass filters 93 filters a different wavelength band from the others (details will be explained later).

[0069] The tilted dichroic mirror 91 is a mirror made using a special optical material that separates light from sample 150 by transmitting and reflecting it according to its wavelength, and its transmittance and reflectance change within a predetermined wavelength range. In the tilted dichroic mirror 91, as shown in Figure 7, the wavelength range (edge ​​transition width) in which the transmittance (and reflectance) of light changes according to the change in wavelength includes all of the wavelength ranges of light containing red wavelength components, green wavelength components, and blue wavelength components. In other words, the "predetermined wavelength range" of the tilted dichroic mirror 91 described above includes all of the wavelength ranges of light containing red wavelength components, green wavelength components, and blue wavelength components.

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

[0071] The correction process will now be explained. When light is incident at an angle (not at the pupil position of the objective lens), the light incident on the tilted dichroic mirror 91 and bandpass filter 93 will only partially transmit light rather than the entire amount. This can cause a problem where the transmitted wavelength shifts due to unevenness in the in-plane uniformity of the tilted dichroic mirror 91 and bandpass filter 93. Conversely, if the wavelength characteristics are distorted from a straight line due to light from multiple directions incident on the tilted dichroic mirror 91, this process has the effect of smoothing the wavelength characteristics. As a countermeasure against unevenness in the surface uniformity of the tilted dichroic mirror 91 and bandpass filter 93, it is conceivable to pre-calculate the in-plane wavelength distribution by uniformly incident light of the same wavelength within the field of view, and then measure and correct the shift from the incident wavelength.

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

[0073] Firstly, the camera system 90A may be configured to include a bandpass filter 93 of one type (with a single range of wavelengths to be filtered) and area sensors 94 and 95, which are monochrome sensors. In this case, the bandpass filter 93 removes light with wavelengths outside the range of, for example, 400 to 900 nm. In such a configuration, the light incident on the area sensors 94 and 95 may contain a mixture of the three RGB colors. In this case, the control device (not shown) determines the averaged wavelength centroid of the light in the wavelength band that has passed through the bandpass filter 93 (light containing a mixture of the three RGB colors). Furthermore, when light of different wavelength bands (each of the RGB lights) is spatially separated (does not overlap in the image), the control device (not shown) can determine the wavelength centroid for each wavelength band with high precision. Specifically, the wavelength centroid of the color of each pixel of a TV or display can be determined with high precision in nm units according to this embodiment.

[0074] Secondly, the camera system 90A may be configured to include multiple types of bandpass filters 93 that filter different wavelength bands from each other, and area sensors 94 and 95 which are monochrome sensors. In this case, the multiple types of bandpass filters 93 are provided so that they can be turned in and out (switched) in accordance with the emission from the sample 150. In such a configuration, when the sample 150 outputs emission with a broad spectrum (with superposition), the control device (not shown) can determine the wavelength centroid of light only in a specific wavelength band (wavelength band corresponding to each bandpass filter 93) by switching between the multiple types of bandpass filters 93. In other words, the control device (not shown) determines the wavelength centroid of only the red wavelength component when a bandpass filter 93 is set to remove light of wavelengths other than the red wavelength component wavelength band (e.g., 700-900 nm), determines the wavelength centroid of only the green wavelength component when a bandpass filter 93 is set to remove light of wavelengths other than the green wavelength component wavelength band (e.g., 550-700 nm), and determines the wavelength centroid of only the blue wavelength component when a bandpass filter 93 is set to remove light of wavelengths other than the blue wavelength component wavelength band (e.g., 400-550 nm). Specifically, for a light source that realizes a white LED using a blue LED and a fluorescent agent, the second configuration makes it possible to determine the wavelength centroid of only the blue LED and the wavelength centroid of only the fluorescent agent.

[0075] Thirdly, the camera system 90A may be configured to include a bandpass filter 93 of one type (with one range of wavelengths to be filtered) and area sensors 94 and 95, which are color sensors. In this case, the bandpass filter 93 removes light with wavelengths outside the range of 400 to 900 nm, for example. In such a configuration, the light incident on the area sensors 94 and 95, which are color sensors, may be a mixture of the three RGB colors. Each pixel of the color sensor is equipped with a Bayer filter (a filter for the three RGB colors). As a result, each photodetector element of the area sensors 94 and 95 can acquire light with only the red wavelength component, light with only the green wavelength component, and light with only the blue wavelength component, respectively. With such a configuration, the wavelength centroid can be appropriately determined for colors that are represented by a superposition of multiple wavelengths (i.e., appropriate inspection can be performed). Normally, the colors of printing and emission are made by superimposing the three RGB colors to match the human eye. By calculating the wavelength centroid for each of the superimposed colors in this way, mixed colors can be inspected with high accuracy. Furthermore, by combining a hyperspectral camera as the imaging unit, the centroids of more wavelengths can be inspected simultaneously. A hyperspectral camera is composed of, for example, a spectrometer and an imaging unit.

[0076] Another example of a camera system (imaging unit) using an inclined dichroic mirror having the characteristics shown in Figure 7 will be described with reference to Figure 9. Figure 9 is a schematic diagram of a camera system 90B relating to another modified example. The differences from the configuration shown in Figure 8 will be mainly explained below.

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

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

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

[0080] The bandpass filter 93 is provided, for example, downstream of the infinity focus lens 92B and upstream of the inclined dichroic mirror 91, and is a filter that removes light outside a predetermined wavelength range. The bandpass filter 93 removes light with wavelengths outside the range of 400 to 900 nm, for example. Multiple bandpass filters 93 may be provided. The bandpass filter 93 may be provided in the region shown by the dashed line in Figure 9, that is, in the region upstream of the infinity focus lens 92B, or in the region upstream of the area sensors 94 and 95 and downstream of the imaging lenses 96 and 97, or in the region upstream of the imaging lenses 96 and 97 and downstream of the inclined dichroic mirror 91. The bandpass filters 93 provided upstream of the area sensors 94 and 95 are made to have the same characteristics, and the bandpass filters 93 provided upstream of the imaging lenses 96 and 97 are made to have the same characteristics.

[0081] Similar to the camera system 90A, the three embodiments described above are also possible for the camera system 90B using the infinity focus lens 92B.

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

[0083] Thus, by using a separation optical element whose transmittance and reflectance change according to wavelength, even light with a narrow wavelength range can be appropriately separated, and the wavelength centroid can be appropriately determined according to the imaging results in the imaging unit. Furthermore, unlike the embodiment described above, the light that has passed through the separation optical element can be received directly by the imaging unit (first imaging unit and second imaging unit), thus enabling miniaturization of the camera system.

[0084] Furthermore, in the modified camera system, the wavelength ranges to which the first and second imaging units are sensitive correspond to the wavelength ranges in which the transmittance and reflectance of the separating optical element change. With this configuration, the change (difference) in wavelength can be appropriately obtained from the imaging results of the imaging unit, and the wavelength centroid can be appropriately determined.

[0085] Furthermore, the modified camera system includes multiple types of bandpass filters that can be switched according to the light from the object. For example, when the object emits light with a broad spectrum (superposition), the control device (not shown) can determine the wavelength centroid of light only in a specific wavelength band (wavelength band corresponding to each bandpass filter) by switching between multiple types of bandpass filters. That is, the control device (not shown) can determine the wavelength centroid of only the red wavelength component when a bandpass filter that removes light of wavelengths other than the red wavelength component is set, determine the wavelength centroid of only the green wavelength component when a bandpass filter that removes light of wavelengths other than the green wavelength component is set, and determine the wavelength centroid of only the blue wavelength component when a bandpass filter that removes light of wavelengths other than the blue wavelength component is set. [Explanation of Symbols]

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

Claims

1. A separating optical element that separates light from an object by transmitting or reflecting it according to its wavelength, and has a predetermined wavelength range which 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 images the light transmitted through the aforementioned separating optical element, A second area sensor that captures light reflected by the aforementioned separating optical element, A filter provided prior to the aforementioned separating optical element, The system comprises a reflective optical element provided between the separating optical element and the second area sensor, The filter removes light outside the predetermined wavelength range in the separating optical element. The light reflected by the separating optical element is further reflected by the reflecting optical element and guided to the second area sensor. An imaging unit further comprising a processing unit that corrects color variations caused by the angle of incidence of light to the separating optical element and the filter based on correction data that takes into account the optical characteristics of the separating optical element related to changes in transmittance and reflectance with respect to wavelength.

2. The imaging unit according to claim 1, wherein the filter includes a plurality of bandpass filters, each filtering different wavelength bands from one another and configured to be switchable and selectable according to the light from the object.

3. The imaging unit according to claim 2, wherein the plurality of bandpass filters include a bandpass filter that removes light of wavelengths other than the wavelength band of the red wavelength component, a bandpass filter that removes light of wavelengths other than the wavelength band of the green wavelength component, and a bandpass filter that removes light of wavelengths other than the wavelength band of the blue wavelength component.

4. The imaging unit according to claim 1, wherein the filter removes light outside the range of 400 to 900 nm.

5. The imaging unit according to any one of claims 1 to 4, wherein both the first area sensor and the second area sensor are monochrome sensors.

Images