JP2006208102A - Spectral colorimetry device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a precise spectral colorimetry device used for measuring a color. <P>SOLUTION: The spectral colorimetry device comprises a slit body 1 in which an entrance slit 11 for transmitting measurement light from an object to be measured passes; a collimator lens 2 for converting measurement light through the entrance slit 11 to parallel light; a reflection type diffraction grating 3 for diffracting measurement light emitted from the collimator lens 2 for reflecting at a different angle for each wavelength; an image-forming lens 4 for condensing measurement light diffracted by the reflection type diffraction grating 3; and an image pickup device 5 for imaging an image formed by measurement light condensed by the image-forming lens 4. The entrance slit 11 is formed in an arc so that an image 50 formed in the image pickup device 5 becomes straight for each wavelength. As compared with a case where the entrance slit 11 is made straight, the contribution of the incident position of measurement light to the position of the image 50 in a direction corresponding to the wavelength is suppressed, thus improving precision. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a spectrocolorimetric apparatus used for color measurement.

  Conventionally, in a spectrocolorimeter that measures the spectral distribution of a measurement light reflected by the object to be measured or radiated by the object to be measured by a diffraction grating, a light receiving element that receives the dispersed measurement light In addition to a spectral colorimetry device called a monochromator that measures the intensity of each wavelength of the measurement light by changing the wavelength that reaches the diffraction grating by rotating the diffraction grating, an image formed by, for example, a CCD is used to capture an image formed by the dispersed measurement light There has been provided a spectrocolorimeter called a polychromator capable of simultaneously measuring an intensity distribution over a certain wavelength range by imaging using an element.

  Furthermore, in the above spectrocolorimetric apparatus called a polychromator, the hole for introducing the measurement light is a straight slit that is long in the direction along the grating of the diffraction grating. There is also provided a configuration in which a shape region can be measured simultaneously (for example, see Patent Document 1). This type of spectrocolorimetric apparatus can perform scanning on the object to be measured at a higher speed than that in which the hole for introducing the measurement light has a small circular shape.

  An example of a schematic configuration of this type of spectrocolorimetric apparatus is shown in FIG. The spectrocolorimetric apparatus is a slit body 1 provided with a linear incident slit 11 that allows measurement light from a measured object T (see FIG. 6) to pass through, and the measurement light that has passed through the incident slit 11 is converted into parallel light. A collimating lens 2 as a collimating means for conversion, a reflective diffraction grating 3 that is composed of, for example, a blazed diffraction grating, diffracts measurement light emitted from the collimating lens 2 and reflects it at different angles for each wavelength, and is diffracted by the reflective diffraction grating 3 An imaging lens 4 that collects the measured light and an imaging device 5 that is made of, for example, a CCD and captures an image formed by the measurement light collected by the imaging lens 4 are provided. In addition, an imaging lens (not shown) that condenses measurement light from the object T to be measured on the entrance slit 11 is provided. Further, the collimator lens 2, the reflective diffraction grating 3, the imaging lens 4, and the image sensor 5 are each a housing that holds the slit body 1 so that light that has not passed through the entrance slit 11 does not enter the image sensor 5. (Not shown).

  As shown in FIG. 5, for example, the collimating lens 2 and the imaging lens 4 are each composed of meniscus lenses 21 and 41, convex lenses 22 and 42, and cemented lenses 23 and 43 of meniscus lenses and convex lenses. This is a single lens. In the example of FIG. 5, the collimating lens 2 and the imaging lens 4 have a common configuration and are arranged in opposite directions along the optical axis.

  Further, as shown in FIGS. 6 and 7, the collimating lens 2, the imaging lens 4, and the imaging lens are respectively held by cylindrical holders 2a, 4a, and 7a. The slit body 1, the collimator lens 2 holder 2 a, the reflective diffraction grating 3, the imaging lens 4 holder 4 a, and the case 5 a containing the image sensor 5 are fixed to a common base BA, respectively. The lens holder 7 a is fixed to the slit body 1.

  Next, the positional relationship between the above components will be described. The direction in which the gratings of the reflective diffraction grating 3 are arranged is orthogonal to the longitudinal direction of the entrance slit 11. The center of the entrance slit 11 is disposed at the object side focal point of the collimator lens 2, and the opening surface of the entrance slit 11 and the optical axis of the collimator lens 2 are orthogonal to each other. That is, the opening surface of the entrance slit 11 is located on the object plane of the collimating lens 2. As a result, the measurement light incident from the entrance slit 11 and exiting the collimator lens 2 becomes parallel light. The image sensor 5 is disposed at the image side focal point of the imaging lens 4. Further, the collimating lens 2, the imaging lens 4, and the reflective diffraction grating are arranged so that the image-side focal point of the collimating lens 2 and the object-side focal point of the imaging lens 4 are positioned at one point O on the reflective diffraction grating 3. 3 is arranged. As described above, the collimating lens 2, the reflective diffraction grating 3, and the imaging lens 4 constitute a telecentric optical system as a whole. Further, when a light beam having a central wavelength in the wavelength range assumed as measurement light is incident from the center of the entrance slit, the first-order diffracted light of this light beam is emitted onto the optical axis of the imaging lens 4. The direction of the reflective diffraction grating 3 is adjusted. For example, when visible light (wavelength 400 nm to 700 nm) is assumed as measurement light, the central wavelength is 550 nm. Further, the collimating lens 2 and the imaging lens 4 are arranged in a positional relationship in which their optical axes are orthogonal to each other at a point O on the reflective diffraction grating 3.

Then, the measurement light that has passed through the incident slit 11 is converted into parallel light by the collimator lens 2, diffracted by the reflective diffraction grating 3, and condensed by the imaging lens 4. A streak-like image 50 corresponding to the shape is formed. In FIG. 4, only one image 50 is drawn for the sake of simplicity, but actually, a plurality of images 50 for each wavelength included in the measurement light are formed. The image 50 is formed at a position farther from the slit body 1 as the wavelength is longer and the diffraction order is larger. That is, the position of the image 50 in the direction in which the gratings of the reflective diffraction grating 3 are arranged (left and right direction in FIG. 4) corresponds to the wavelength of the light included in the measurement light. Therefore, the image 50 picked up by the image pickup device 5 shows the spectral distribution of the measurement light with respect to the position in the direction corresponding to the longitudinal direction of the incident slit 11 in the long thin region facing the incident slit 11 in the object T to be measured. ing. Then, the object T is scanned by moving the object T relative to the slit body 1 in the short direction (left-right direction in FIG. 4) of the entrance slit 11 indicated by the arrow A2 in FIG. It is possible.
Japanese Patent Laid-Open No. 11-101692

  Here, the measurement light (hereinafter referred to as “incident”) is incident from the longitudinal end of the incident slit 11 and enters the image sensor 5 through a path such as B → O → B ′ → B ″ or C → O → C ′ → C ″. , Referred to as “end measurement light”) and measurement light (hereinafter referred to as “end measurement light”) that is incident from the center in the longitudinal direction of the entrance slit 11 and enters the image pickup device 5 along the path of A → O → A ′ → A ″. The angle formed with respect to the grating of the reflective diffraction grating 3 when entering the reflective diffraction grating 3 is different from that of the central measurement light. Therefore, even if the reflection angle as viewed from the direction along the grating of the reflective diffraction grating 3 (vertical direction in FIG. 4) is the same, the optical path difference between adjacent gratings is the difference between the edge measurement light and the center measurement light. Different. For this reason, even if they have the same wavelength and the same diffraction order, if the positions incident on the entrance slit 11 are different as in the central measurement light and the end measurement light, the direction from the direction along the grating of the reflective diffraction grating 3 is different. Different diffraction angles. As a result, the positions of the images at both ends in the longitudinal direction of the entrance slit 11 are shifted in the direction in which the gratings of the reflective diffraction gratings 3 are arranged with respect to the position of the image at the center in the longitudinal direction. This shift increases as the incident position of the measurement light is closer to the longitudinal end of the incident slit 11, and the image 50 connected to the image sensor 5 has an arc shape as a whole for each wavelength.

  For example, consider a case where the central measurement light is incident on the reflection type diffraction grating 3 from a direction perpendicular to the reflection type diffraction grating 3. In this case, the edge measurement light enters the reflective diffraction grating 3 from a direction that is not perpendicular to the reflective diffraction grating 3. That is, even if the reflection angles viewed from the direction along the grating of the reflective diffraction grating 3 are the same, the optical path difference between adjacent gratings is longer for the end measurement light than for the center measurement light. Therefore, the edge measurement light has a smaller diffraction angle as viewed from the direction along the grating of the reflective diffraction grating 3 than the central measurement light having the same diffraction order and wavelength in the reflective diffraction grating 3. . That is, the end measurement light behaves as if it has a shorter wavelength than the actual wavelength with respect to the reflective diffraction grating 3 when viewed from the direction along the grating of the reflective diffraction grating 3. As a result, the images at both ends in the longitudinal direction of the entrance slit 11 are shifted to the short wavelength side (left side in FIG. 4), and the image 50 connected to the image sensor 5 has an arc shape as a whole for each wavelength. The arc-shaped curvature ρ includes the wavelength λ, the diffraction order m, the diffraction angle β of the central measurement light in the reflective diffraction grating 3, the lattice constant d of the reflective diffraction grating 3, and the object of the imaging lens 4. It is expressed by the following equation using the focal length (front focal length) f.

ρ = (f · d / (m · λ)) cos β (Formula 1)
When the image 50 is distorted in an arc shape as described above, when the position of the image 50 and the wavelength are associated with each other with the measurement light at the center as a reference, the wavelength error increases as the position is closer to the end in the longitudinal direction of the entrance slit 11. turn into.

  The present invention has been made in view of the above-described reasons, and an object thereof is to provide a spectrocolorimetric apparatus with improved accuracy.

  According to the first aspect of the present invention, there is provided a slit body provided with an entrance slit for allowing measurement light from the object to be measured to pass through, collimating means for converting the measurement light that has passed through the entrance slit into parallel light, and collimation means for making parallel light. Equipped with a diffraction grating that diffracts the converted measurement light and an image sensor that captures an image formed by the measurement light diffracted by the diffraction grating. An image formed by connecting the measurement light to the image sensor is linear for each wavelength. It is characterized by being formed in an arc shape that becomes

  According to the present invention, compared with the case where the incident slit is formed in a linear shape, the contribution of the incident position of the measurement light to the position of the image in the direction corresponding to the wavelength is suppressed, so that the accuracy is improved.

  According to a second aspect of the present invention, a light guide composed of a plurality of optical fibers in which incident ends on which measurement light from the object to be measured is incident are linearly arranged, and measurement light emitted from the light guide is converted into parallel light. A collimating unit; a diffraction grating that diffracts the measurement light converted into parallel light by the collimating unit; and an image sensor that captures an image formed by the measurement light diffracted by the diffraction grating. In the optical fiber constituting the light guide, the emission ends from which the measurement light is emitted are arranged in an arc shape so that an image to be connected to the imaging element has a linear shape for each wavelength.

  According to this invention, since the contribution of the incident position of the measurement light to the position of the image in the direction corresponding to the wavelength is suppressed as compared with the case where the emission ends of the optical fibers constituting the light guide are arranged in a linear shape, Accuracy is improved. Also, since the incident end of the optical fiber is arranged in a linear shape, the region to be measured at the same time in the object to be measured becomes a linear shape. Therefore, compared to the case where the incident end of the optical fiber is arranged in a curved shape, The correspondence between the position in the image and the position in the image is simple and easy to use.

  The present invention provides a light composed of a plurality of optical fibers in which an entrance slit is formed in an arc shape or an output end is arranged in an arc shape so that an image formed by measuring light on an image sensor has a linear shape for each wavelength. Since the guide is provided, the contribution of the incident position of the measurement light to the position of the image in the direction corresponding to the wavelength is suppressed, so that the accuracy is improved.

  The best mode for carrying out the present invention will be described below with reference to the drawings. In addition, since the basic composition of each following embodiment is respectively common with a prior art example, about the common part, the same code | symbol is attached | subjected and description is abbreviate | omitted.

(Embodiment 1)
In the present embodiment, as shown in FIG. 1, the position of each part of the entrance slit 11 is shifted in a direction to cancel the position shift of both ends of the image 50 connected to the image sensor 5 in the conventional example.

  For example, when the measurement light incident on the center of the entrance slit 11 enters the reflective diffraction grating 3 from a direction perpendicular to the grating, the shape of the entrance slit 11 is connected to the image sensor 5 in the conventional example. The arc shape of the image 50 is bent in a direction opposite to the arc shape, that is, in a direction approaching the imaging element 5 (rightward in FIG. 1) as it approaches the end in the longitudinal direction. The width dimension of the entrance slit 11 is 20 μm, for example.

  Here, the curvature of the arc shape of the entrance slit 11 is such that the image 50 connected to the image sensor 5 has a linear shape for each wavelength. Specifically, for example, using the formula 1 shown in the conventional example, λ is the center wavelength of the assumed wavelength range of the measurement light, m is 1, and β is along the grating of the reflective diffraction grating 3 Obtained by substituting the incident angle of the measurement light with respect to the reflective diffraction grating 3 as viewed from the vertical direction (vertical direction in FIG. 1) and the image focal length (rear focal length) of the collimating lens 2 into f, respectively. Let ρ be the curvature of the arc shape of the entrance slit 11. When the interfocal distance L (see FIG. 5) of the collimating lens 2 and the imaging lens 4 is 50.6 mm, the arc-shaped curvature radius of the entrance slit 11 is, for example, 52.4 mm.

  According to the above configuration, the image 50 connected to the imaging device 5 by the measurement light has a linear shape for each wavelength, and the linear shape is a direction in which the gratings of the reflective diffraction grating 3 are arranged, that is, a direction corresponding to the wavelength (FIG. 1). Since the correspondence relationship between the position of the image 50 in the direction corresponding to the wavelength and the wavelength of the measurement light is substantially constant regardless of the incident position of the measurement light on the incident slit 11, The accuracy is improved as compared with the case where the entrance slit 11 has a linear shape.

  Incidentally, in a comparative experiment conducted by the present inventor, when the entrance slit 11 has a linear shape, an image 50 bent into an arc shape as shown in FIG. The same measurement light was corrected to a linear shape as shown in FIG.

(Embodiment 2)
In this embodiment, as shown in FIG. 3, instead of the slit body 1, as shown by an arrow A1, a plurality of optical fibers in which incident ends on which measurement light from the object T is incident are arranged in a linear shape A light guide 6 comprising 61 is provided. The light guide 6 is held in a housing (not shown) in which, for example, the collimating lens 2, the reflective diffraction grating 3, the imaging lens 4, and the image sensor 5 are housed, and light that has not passed through the light guide 6 is captured by the image sensor. 5 so as not to be incident. In the optical fiber 61, the emission ends from which the measurement light is emitted are arranged in a direction along the grating of the reflective diffraction grating 3 (up and down direction in FIG. 3), and the measurement light emitted from the central optical fiber 61 is transmitted through the collimating lens 2. It passes on the optical axis. Further, the optical fibers 61 do not cross each other, and the order in which the optical fibers 61 are arranged is the same on the incident end side and the outgoing end side.

  Further, the image 50 connected to the image pickup device 5 by the measurement light has a linear shape for each wavelength, and the linear shape is a direction in which the gratings of the reflective diffraction grating 3 are arranged, that is, a direction corresponding to the wavelength (left-right direction in FIG. 3). The emission ends of the optical fibers 61 are arranged in an arc shape so as to be orthogonal to the optical axis. For example, when the measurement light emitted from the central optical fiber 61 is incident on the reflective diffraction grating 3 from a direction perpendicular to the grating, the emission end of the optical fiber 61 is connected to the image sensor 5 in the conventional example. They are arranged in an arc shape that is bent in a direction opposite to the arc shape of the image, that is, in a direction approaching the image sensor 5 (rightward in FIG. 3) as it approaches the end in the longitudinal direction. The curvature of the arc shape can be determined in the same manner as the curvature of the arc shape of the entrance slit 11 in the first embodiment.

  According to the above configuration, the correspondence between the position of the image 50 in the direction corresponding to the wavelength and the wavelength of the measurement light is substantially constant regardless of the position of the measurement light incident on the light guide 6. The accuracy is improved as compared with the case where the emission ends are arranged in a linear shape.

  Further, unlike the first embodiment, the region simultaneously measured on the object T to be measured has a linear shape, so that the correspondence between the position on the object T to be measured and the position on the image 50 is simpler than in the first embodiment. So easy to use.

  Note that the image 50 is desirably a linear shape orthogonal to the direction corresponding to the wavelength as in the first embodiment or the present embodiment, but the wavelength 50 may be a linear shape that is not orthogonal to the direction corresponding to the wavelength. Since the contribution of the incident position of the measurement light to the image position in the direction corresponding to is linear and correction by calculation is easy, the accuracy can be improved.

It is a schematic block diagram which shows Embodiment 1 of this invention. It is a photograph which shows an effect same as the above, (a) shows the picture imaged by the image sensor before application of the present invention, and (b) shows the image imaged by the image sensor for the same measurement light after application of the present invention. Show. It is a schematic block diagram which shows Embodiment 2 of this invention. It is a schematic block diagram which shows a prior art example. It is explanatory drawing which shows an optical system same as the above. It is a perspective view which shows the same as the above. It is the partially broken perspective view which shows the principal part same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Slit body 2 Collimating lens 3 Reflection type diffraction grating 5 Image pick-up element 6 Light guide 11 Incident slit 50 Image 61 Optical fiber T Measured object

Claims (2)

A slit body provided with an entrance slit for passing measurement light from the object to be measured, a collimating means for converting the measurement light that has passed through the entrance slit into parallel light, and diffracting the measurement light converted into parallel light by the collimating means And an imaging element that captures an image formed by measurement light diffracted by the diffraction grating,
A spectrocolorimetric apparatus, wherein the entrance slit is formed in an arc shape so that an image formed by measuring light on the image sensor is linear for each wavelength. A light guide composed of a plurality of optical fibers in which measurement light beams from an object to be measured are incident and arranged in a straight line; a collimating means for converting the measurement light emitted from the light guide into parallel light; and a collimating means. A diffraction grating that diffracts the measurement light converted into parallel light, and an imaging element that captures an image formed by the measurement light diffracted by the diffraction grating;
The output end from which the measurement light is emitted is arranged in an arc shape in the optical fiber that constitutes the light guide so that the image that the measurement light that has passed through the light guide is connected to the image sensor has a linear shape for each wavelength. Spectral color measuring device.