JPH10311757A - Color measuring apparatus and its adjusting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform focus adjustment on a photo detector easily. SOLUTION: Spectral measurement of a reference sample wherein a high- reflectance region and a low-reflectance region are combined in a one- dimensional region, and a spectral image is obtained in a photo detector (S2). Photoelectric signals of photoelectric detectors before and after the border line of image parts for two regions are read (S3), and a maximum photoreception intensity corresponding to the high-reflectance region and a minimum photoreception intensity corresponding to the low-reflectance region are extracted (S4), and by using them a contrast index value is computed (S5). Since this value varies by a focused state, it becomes possible to perform optimum focus adjustment changing the distance between a lens and the photo detector considering the numerical value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting an optical system in a color measuring apparatus utilizing spectrometry and a color measuring apparatus using the adjusting method. Adjustment method and color in a color measurement device using spectral measurement that forms a spectral image on a photodetector in which a plurality of minute light receiving elements are two-dimensionally arranged and simultaneously obtains positional information and wavelength direction information. It relates to a measuring device.

[0002]

2. Description of the Related Art The color of an object recognized by humans is determined by three factors: the spectral distribution of a light source, the sensitivity of eyes, and the reflectance or transmittance of the object. In colorimetry, the former two factors are specified as numerical values in JIS (Japanese Industrial Standards), so that the color is obtained as an objective numerical value by measuring the reflectance or transmittance of an object using a spectrometer. be able to. In general, the color of an object to be measured is a color distribution having a two-dimensional spread. For this reason, in a spectrometer used for color measurement, it is necessary to obtain a reflectance or transmittance distribution on a two-dimensional projection surface of an object.

FIG. 6 is a block diagram of a color measuring apparatus capable of measuring the color distribution of a two-dimensional area of a sample. Light emitted from the light source 11 is reflected by a one-dimensional area extending in the Y-axis direction of the sample 2, collected by a focus-adjustable lens 12, and guided to a slit 13. The light that has passed through the slit 13 is collimated by a lens 14, wavelength-dispersed by a diffraction grating 15, and then projected onto a photodetector 18 via a secondary light removal filter 16 and a lens 17. The photodetector 18 has minute light receiving elements arranged two-dimensionally.
In the y-axis (position) direction on 8, position information in the one-dimensional area of the sample 2 is obtained, and in the λ-axis (wavelength) direction orthogonal to the y-axis, each point (micro area) in the one-dimensional area is obtained. ) Can be obtained.

A signal processor 40 calculates a reflectance distribution (spectrum) from the spectral image obtained on the photodetector 18 and an index such as a color tristimulus value based on the reflectance. Values (here, these are collectively called "color values")
And a color value calculation unit 42 for calculating the calculation result. The calculation result is sent to an output unit 44 such as a display or a printer. The operation unit 43 is used for instructing start of measurement and the like and setting of various parameters. In practice, the signal processing unit 40 is a personal computer (hereinafter referred to as “PC”).
), And various processes as described below are performed by causing the personal computer to execute a predetermined program.

When obtaining a spectral intensity distribution from a spectral image, a wavelength width Δλm with respect to a predetermined center wavelength λm is set in the λ-axis direction, and an intensity signal obtained by a plurality of light receiving elements included in the wavelength width Δλm. Are integrated or averaged. In this way, the spectral intensity distribution at a certain point in the one-dimensional area is obtained. Subsequently, the spectral intensity distribution at each point in the one-dimensional area is calculated, whereby the spectral intensity distribution of the one-dimensional area on the sample 2 is obtained. Further, the moving table 1 on which the sample 2 is mounted and the optical unit 10 including the light source 11 and the like are sequentially moved in predetermined steps in the X-axis direction while repeatedly obtaining a spectral image of a one-dimensional region, thereby obtaining a spectral image of the sample 2. The spectral intensity distribution in a two-dimensional area is measured.

[0006]

In the color measuring apparatus having the above structure, in order to perform highly accurate colorimetry on a sample having a fine pattern, it is necessary to project a sample image on the photodetector 18 with high contrast. . Since a high contrast is obtained when the outline of the projected image is clear, it is required to form an image on the photodetector 18 with high focus accuracy. If the focus accuracy is poor, the projected image will be blurred, optical noise will increase, and the color resolution (here, "the minimum pattern size on the sample that can perform colorimetry with a precision higher than a predetermined level") ).
Further, if all points simultaneously projected on the photodetector 18 do not have uniform contrast characteristics,
The color resolution differs depending on the position on the sample, and the accuracy of the color measurement decreases.

Therefore, conventionally, the optical path in the optical unit 10 is adjusted as follows. First, slit 1
Lens 12 so that a one-dimensional image of the sample is formed on the aperture 3
Adjust the focus. For example, a photodetector is placed at the position of the slit 13, and the lens 12 is adjusted so that the peak of the received light intensity becomes maximum. Next, the adjuster adjusts the lens 17 while watching the image (sample image) projected on the photodetector 18 so that the light wavelength-dispersed by the diffraction grating 15 is condensed on the photodetector 18 with high contrast. The distance between the light detector 18 and the light detector 18 is adjusted so that the light is focused on the light detector 18.

However, since the above-mentioned conventional adjustment method relies on visual confirmation, it is difficult to adjust the focal position to an optimum one. It is even more difficult to perform adjustment so as to obtain a uniform color resolution. Almost impossible. Also,
Since the adjustment requires skill, it was necessary for a trained person to make the adjustment.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a first object of the present invention is to perform an optimum focus adjustment while an adjuster objectively grasps the contrast of a projected image. It is an object of the present invention to provide a method for adjusting a color measuring device capable of performing the above-mentioned operations. It is a second object of the present invention to provide a color measuring apparatus in which optimal focus adjustment is automatically performed so as to obtain the best color resolution as a whole.

[0010]

Means for Solving the Problems A first invention made to solve the above-mentioned problem is that a primary light-receiving element in which a plurality of minute light receiving elements are arranged two-dimensionally is arranged in one dimension direction of a photodetector. A color measurement device that forms a spectral image by projecting an original area image and dispersing light in another dimension in wavelength, and calculating an index value that expresses a color based on a spectral intensity distribution obtained from the spectral image. In, a method of adjusting the optical system for spectroscopic measurement, a) by spectroscopically measuring a reference sample having a specific pattern that combines a high reflectivity first region and a low reflectivity second region B) projecting the spectral image on the photodetector, and b) along the direction of the position of the photodetector, the light receiving elements arranged near the boundary between the image portion for the first region and the image portion for the second region adjacent thereto. Read out the received light intensity signal, c) the first Calculating an index value indicating the contrast based on the received light intensity of the image portion with respect to the area and the received light intensity of the image portion with respect to the second region, d) using the index value, the focal point of image formation on the photodetector is calculated. The optical system is adjusted so as to be in an optimum state.

According to a second aspect of the present invention, an image of a one-dimensional area of a sample is formed in one direction of a photodetector having a plurality of minute light receiving elements arranged two-dimensionally. In a color measurement apparatus that forms a spectral image by projecting and dispersing light in another direction in wavelength and forming a color based on a spectral intensity distribution obtained from the spectral image, a) For a spectral image projected on a photodetector by spectroscopically measuring a reference sample having a specific pattern combining a first region with a high reflectivity and a second region with a low reflectivity, the photodetector Reading means for reading light intensity signals of the light receiving elements arranged in the vicinity of the boundary between the image part for the first area and the image part for the second area adjacent thereto along the position direction; b) read by the reading means Said first territory Calculating means for calculating an index value indicating contrast based on the received light intensity of the image portion with respect to the second region and the received light intensity of the image portion with respect to c) adjusting means for changing the focus of the projected image on the photodetector; d) And control means for controlling the adjusting means so that the focal point of the image formed on the photodetector is in an optimum state in accordance with the index value.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the color measuring device according to the first invention and the color measuring device according to the second invention, the focus of the projected image on the photodetector is adjusted. To perform, a reference sample having a specific pattern in which a first region of high reflectivity and a second region of low reflectivity are appropriately combined in a one-dimensional region is spectroscopically measured. For example, it is preferable that the first region be white having a substantially uniform high reflectance in the visible region, and the second region be black having a substantially uniform low reflectance in the visible region.

When the reference sample is spectrally measured, a striped pattern extending in the wavelength direction corresponding to the first and second regions appears in the spectral image projected on the photodetector. For this reason, when the light receiving signals of the light receiving elements arranged along the position direction so as to cross the stripe pattern are read, a relatively large light receiving intensity is obtained in the image portion corresponding to the first region, and the image portion corresponding to the second region is read. In this case, a relatively small received light intensity can be obtained. Therefore, the difference (or ratio) of the received light intensity between the image portion corresponding to the first region and the image portion corresponding to the second region adjacent thereto is calculated for each first region. Then, based on the difference between the received light intensities, an index value indicating the contrast near the boundary between the image portion corresponding to the first region and the image portion corresponding to the second region adjacent thereto is calculated and displayed. .
When the projected image on the photodetector is out of focus, the contrast is deteriorated because the image portions are influenced by each other in the vicinity of the boundary. Therefore, while looking at the displayed index value, for example, the position of the photodetector can be moved back and forth to find the best focus position.

According to the method for adjusting the color measuring device according to the first aspect of the invention, the contrast on the photodetector is displayed as an objective numerical value. The optical system can be easily adjusted so that As a result, high color resolution can be obtained during color measurement.

In general, the contrast differs depending on the position on the photodetector, and therefore, the image portion corresponding to the different first region in the same position direction and the same first region at different wavelengths. In the vicinity of the image part,
Each has a different light receiving intensity. Therefore, in order to make the contrast most uniform over the entire photodetector, a value indicating the variation in contrast is calculated based on the index values of the contrast obtained at a plurality of locations on the photodetector. It is preferable to adjust the focus while checking the value. By doing so, the variation in contrast on the photodetector is reduced, and as a result, more accurate colorimetry with less variation in color resolution can be performed.

[0016] The color measuring apparatus according to the second invention comprises:
An adjusting means for changing the focal point of the projection image on the photodetector is provided, and the control means controls the adjusting means according to the index value calculated by the arithmetic means as described above. The adjusting means is
For example, an adjusting mechanism that slides the photodetector itself back and forth with respect to the wavelength dispersing means so that the distance from the wavelength dispersing means such as a diffraction grating to the photodetector can be changed.
Further, a lens mechanism which is inserted between the wavelength dispersion means and the photodetector and which can adjust the focal length can be used. Therefore, according to the color measuring apparatus according to the second aspect of the present invention, the adjustment is automatically performed so that the optimum focus state is obtained on the photodetector, so that troublesome adjustment labor and time can be saved.
In addition, there is no adjustment error depending on the skill level of the adjuster.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a color measuring apparatus based on a method for adjusting a color measuring apparatus according to the first invention will be described below with reference to FIGS. FIG. 1 is a configuration diagram of a main part of the color measurement device of the present embodiment. The light receiving signal of each light receiving element constituting the photodetector 18 is read by the reading unit 21 of the adjustment processing unit 20 and input to the arithmetic unit 22. The calculation unit 22 performs a calculation process described later on the received light signal, and sends the obtained numerical information to the display unit 31. The display unit 31 is a display or the like, and displays the numerical information in a predetermined format on the screen. The function of the adjustment processing unit 20 can be realized by causing a personal computer to execute a predetermined program, similarly to the signal processing unit 40 of FIG.

FIG. 2A is a plan view showing an example of a reference sample used for focus adjustment in this embodiment. The whole is black with very low reflectance (preferably closer to 0%) in the entire visible region, has a narrow width in the Y direction at three locations Y1, Y2, and Y3, and is extremely high in the entire visible region. It has a white region showing the reflectance (preferably closer to 100%).

Hereinafter, the procedure of the focus adjustment in the color measuring apparatus of the present embodiment will be described with reference to the flowchart of FIG. The focus adjustment by the lens 12 with respect to the opening of the slit 13 is performed in advance by a conventional method.

When the coordinator places the reference sample 3 shown in FIG. 2A at a predetermined position on the moving table 1 (step S1) and performs a predetermined operation on the operation unit 30, the reference sample 3 Is irradiated, and a spectral image as shown in FIG. 2B is projected on the photodetector 18 (step S2). That is,
A plurality of linear patterns appear extending in the λ-axis direction with respect to the three white regions Y1, Y2, and Y3. The reference sample 3 may be incorporated in the apparatus in advance, and may be automatically installed at a position where spectrometry can be performed by a predetermined operation to start measurement.

The reading section 21 is arranged on a column in the y-axis direction of a predetermined wavelength, in a region y1, y2,.
The light receiving signal of the light receiving element of the photodetector 18 near y3 is read. Here, λ1, λ2, and λ2 on the spectral image of FIG.
At three wavelengths of λ3, signals near the regions y1, y2, and y3 are read. Therefore, in this case, there are nine reading locations of λn * yn (n = 1 to 3) (step S3). When the light receiving signal is read out in this manner, the area y
In the vicinity of the pattern corresponding to 1, y2, y3, FIG.
Waveforms as shown in FIG. That is,
The light reception intensity S is high in an image portion corresponding to a white region having a high reflectance, and the light reception intensity S is low in an image portion corresponding to a black region having a low reflectance.

When the focus of the projected image of the photodetector 18 is good and the boundary between the white area and the black area is clear, FIG.
As shown in (a), the width of the pattern with respect to the white area is relatively narrow, and the peak value is high. For this reason,
The difference between the maximum value Smax and the minimum value Smin of the received light intensity increases. Conversely, if the focus is not appropriate and the image formation is unclear, the two are affected by each other in the vicinity of the boundary between them, and FIG.
As shown in (b), the fluctuation of the received light intensity S near the boundary line becomes gentle, and the peak value of the pattern with respect to the white region becomes low. For this reason, the maximum value S of the received light intensity
The difference between max and the minimum value Smin is reduced.

The arithmetic section 22 receives the light-receiving signal read out as described above, extracts the maximum value Smax and the minimum value Smin of the light-receiving intensity (step S4), and calculates an index value C representing the contrast by the following equation. (Step S5). C = (Smax-Smin) / (Smax + Smin) That is, the index value C is 1 or less, and the maximum value Smax
Is closer to 1 as the difference between the minimum value and the minimum value Smin is larger. The index value C may be sent to the display unit 31 as it is, and may be displayed on the screen of the display unit 31 as a numerical value or a graph. However, since the index values C calculated from the light receiving signals obtained from the nine locations are generally different from each other, simply displaying all the index values together gives a uniform contrast while viewing the index values. It is not easy to adjust.

Then, the arithmetic section 22 calculates an index value reflecting the variation of the average deviation weight of the nine index values C (step S6), and the display section 31 displays the variation index along with each contrast index value C. The value is also displayed at the same time (step S7). Each index value fluctuates when the adjuster shifts the position of the photodetector 18 in the z direction. For example, the position of the photodetector 18 is adjusted so that the variation index value is minimized (step S8). In practice, if the numerical value displayed on the display unit 31 fluctuates in a very short cycle, it is difficult for the adjuster to read the numerical value. Therefore, the numerical value may be displayed by performing appropriate integration or averaging in the time direction. In this way, the focus on the photodetector 18 can be optimized.

Next, an embodiment of the color measuring apparatus according to the second invention will be described with reference to FIG. In this embodiment, an index value representing the contrast is obtained according to the same procedure as in the above embodiment. Further, in the color measuring device of this embodiment,
A moving mechanism 19 composed of a motor or the like is attached to the photodetector 18 so that the photodetector 18 slides in the z direction. When the photodetector 18 slides, the distance between the lens 17 and the photodetector 18 changes, so that the focal point on the photodetector 18 changes. The drive control unit 23 receives the above-described contrast index value from the calculation unit 22 and provides a control signal to the moving mechanism 19. That is, the photodetector 18, the readout unit 21, the arithmetic unit 22, the drive control unit 23,
The moving mechanism 19 forms a feedback loop,
The distance between the lens 17 and the photodetector 18 is adjusted so as to optimize the focus as follows.

The drive controller 23 controls the moving mechanism 19 so that the photodetector 18 moves stepwise within a predetermined range in the z direction. Each time the photodetector 18 moves and temporarily stops, the calculation unit 22 calculates the contrast index value and the variation index value as described above. Then, after the scanning within the predetermined range is completed, the drive control unit 23 controls the moving mechanism 19 so that the photodetector 18 moves to a position where the best focus state is obtained. Further, the contrast index value and the variation index value are calculated again while being moved in smaller steps than the previous movement in the vicinity of the position, and a position where the focus is best in a predetermined range in the vicinity is found.
In this way, the focus can be automatically adjusted to be optimal. Note that, instead of moving the position of the photodetector 18, a mechanism for adjusting the focus of the lens 17 may be provided.

It should be noted that the above embodiment is merely an example, and it is apparent that modifications and modifications can be made as appropriate within the scope of the present invention.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part of a color measurement device using a method for adjusting a color measurement device according to a first invention.

FIG. 2A is a diagram illustrating an example of a reference sample used for adjustment of the color measurement device, and FIG. 2B is a diagram illustrating a spectral image of the reference sample.

FIG. 3 is a flowchart showing a procedure of an adjustment method of the color measurement device.

FIG. 4 is a waveform chart showing an example of a light receiving signal read from a photodetector.

FIG. 5 is a configuration diagram of a main part of a color measurement device according to a second invention.

FIG. 6 is a configuration diagram of a general color measurement device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Moving table 3 ... Reference sample 10 ... Optical unit 11 ... Light source 13 ... Slit 12, 14, 17 ... Lens 15 ... Diffraction grating 18 ... Photodetector 19 ... Moving mechanism 20 ... Adjustment processing part 21 ... Readout part 22 ... Calculation Unit 23: Drive control unit 31: Display unit

Claims (2)

[Claims] 1. A spectroscopic method comprising: projecting a one-dimensional region image of a sample in one dimension of a photodetector having a plurality of minute light receiving elements arranged two-dimensionally; and dispersing light by wavelength dispersion in the other dimension. A method of adjusting an optical system for spectral measurement in a color measuring apparatus that forms an image and calculates an index value that expresses color based on a spectral intensity distribution obtained from the spectral image, comprising: B) projecting a spectral image on a photodetector by spectrally measuring a reference sample having a specific pattern in which a first area of reflectivity and a second area of low reflectivity are combined, and b) a position direction of the photodetector. Along, read out the light receiving intensity signal of the light receiving element arranged near the boundary of the image portion for the first region and the image portion for the second region adjacent thereto, c) the light receiving intensity of the image portion for the first region and the second Receiving image parts for two regions Calculating an index value indicating contrast based on the intensity and d) using the index value to adjust the optical system so that the focus of image formation on the photodetector is in an optimal state. Adjustment method of the color measuring device. 2. A spectrometer by projecting a one-dimensional area image of a sample in one dimension direction of a photodetector having a plurality of microphotodetectors arranged two-dimensionally and dispersing light in another dimension direction. An image is formed, and in a color measurement device that calculates an index value expressing a color based on the spectral intensity distribution obtained from the spectral image, a) a first region having a high reflectance and a second region having a low reflectance. For a spectral image projected on a photodetector by spectroscopically measuring a reference sample having a specific pattern obtained by combining the above, an image portion for the first region and an adjacent portion thereof along the position direction of the photodetector. Reading means for reading out the received light intensity signals of the light receiving elements arranged in the vicinity of the boundary of the image part with respect to the second area, and b) reading the received light intensity of the image part with respect to the first area read out by the reading means and Image section Calculating means for calculating an index value indicating contrast based on the received light intensity of the minute, c) adjusting means for changing the focus of the projected image on the photodetector, d) according to the index value, on the photodetector And a control means for controlling the adjusting means so that the focal point of the imaging is in an optimum state.