JP2007093477A - Method and apparatus of calibrating color measuring device, and color measuring method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a calibrating method for highly accurately performing correction for calibrating to match a color measuring apparatus with a reference device. <P>SOLUTION: The calibrating method comprises a calibration object measuring process for acquiring a measuring value in each changed brightness by arranging the color measuring apparatus of a correction object on an optical path output from a measuring object and changing the brightness of a measuring object into two or more stages, a reference device measuring process for acquiring the measuring value in each brightness by changing the brightness of the measuring object into each same brightness as the calibration object measuring process, and a correction coefficient calculation process S8 for calculating a correction coefficient in each brightness in the color measuring apparatus of the calibration object on the basis of the calibration object measuring value in each brightness and a reference device measuring value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a calibration method, a calibration device, a color measurement method, and a color measurement device for calibrating a color measurement device such as a tristimulus value direct-reading sensor according to a reference device.

  Tristimulus direct-reading color meters, illuminance meters, and luminance meters using photodiodes are known as color measuring devices used to inspect the quality of displayed images in image display devices such as liquid crystal projectors and liquid crystal projection televisions. (For example, refer to Patent Document 1).

  At this time, since it is necessary to inspect a large number of products in the product production line, each product is normally inspected using a plurality of tristimulus value direct reading sensors. In this case, if an error occurs in the measured value between the sensors, a correct inspection cannot be performed. Therefore, it is necessary to perform calibration to eliminate the error between the sensors.

  Specifically, each single color of red, green, and blue with a certain brightness is measured with a tristimulus sensor to be calibrated and a reference device, and a correction coefficient is calculated from the obtained tristimulus values XYZ. The calibration was performed by applying it as a correction value. As the reference device, a tristimulus value type sensor that has been adjusted in advance may be used. Usually, a spectroscopic sensor capable of measuring with higher accuracy than the tristimulus value type sensor is used.

JP-A-9-49765

However, in the conventional calibration method, the correction coefficient obtained at a certain brightness is applied to all the brightness, so that an error becomes large at a point away from the calibration point. There was a problem.
That is, as shown in FIG. 11, a problem with the tristimulus value direct reading type sensor is that the characteristics of the light receiving element (such as a photodiode) are not completely linear with respect to brightness. In particular, the linearity is lost when receiving dark light. For this reason, even if the correction coefficient is obtained at one point of brightness, the error of the measurement value may increase by applying the correction coefficient at other brightnesses.

  In addition, liquid crystal panels used in projectors and the like have different transmittance ratios relative to wavelengths depending on the applied voltage. As a matter of course, the spectral shape of the output light also changes depending on the applied voltage. In other words, since the shape of the spectrum differs depending on the brightness, there is a problem that, when measuring a color, in particular, if a correction coefficient obtained by calibration at one point is applied at all brightnesses, the error becomes large.

  11A, 11B, and 11C are graphs when red (RED), green (GREEN), and blue (BLUE) single colors are measured in a liquid crystal panel whose spectrum changes depending on brightness. 3 shows the relationship between the measured values of the tristimulus value direct reading type sensor and the reference device. In these figures, a straight dotted line 100 portion is an ideal state in which each measured value is in a proportional relationship, and a solid line 101 portion represents a relationship between each measured value of the tristimulus value direct reading type sensor and the reference device. is there. A circle 102 is a measurement value measured at the brightness of one point, and when a correction coefficient for correcting this measurement value to the point 103 on the dotted line so as to have a proportional relationship is used, the other part is a dotted line 104. become that way. As shown by the dotted line 104, when the conventional correction coefficient is applied, the measured values of the tristimulus value direct reading sensor and the reference device coincide with each other at a certain brightness, but an error occurs in other portions. There was a problem that the measurement accuracy was lowered.

  The present invention has been made in view of the above-described problems, and a calibration method capable of performing correction for calibrating a color measuring device such as a tristimulus value direct-reading sensor according to a reference device with high accuracy. It is another object of the present invention to provide a calibration apparatus and a color measurement method and color measurement apparatus capable of high-precision measurement according to a reference device.

  In the color measuring device calibration method of the present invention, the color measuring device to be calibrated is arranged on the path of light output from the measured object, the brightness of the measured object is switched to two or more levels, and the brightness for each switched brightness is changed. Place the reference device on the calibration target measurement process to obtain the measurement value and the light path output from the measurement object, and switch the brightness of the measurement object to the same brightness as the calibration target measurement process. A reference unit measurement step for obtaining each measurement value, a correction factor calculation step for calculating a correction factor for each brightness in the calibration target color measurement device based on the calibration target measurement value for each brightness and the reference unit measurement value, and It is characterized by providing.

According to such a configuration, since the correction coefficient is obtained with brightness of two or more points, the measurement accuracy can be improved as compared with the case where the correction coefficient is obtained only with brightness of one point. That is, in the present invention, since the correction coefficient can be changed depending on the brightness, it is possible to obtain a correction coefficient that matches the characteristics of the light receiving element of the tristimulus value direct reading type sensor compared to the prior art, and highly accurate measurement. It can be performed.
In addition, since calibration is performed using a measurement object such as a projector that is a measurement target of the color measurement apparatus, a color measurement apparatus that inspects a measurement object whose spectrum shape changes according to the brightness, such as a liquid crystal device. High-precision measurement can be performed according to the reference device.

At this time, it is preferable that the correction coefficient calculation step calculates a correction plane coefficient representing a correction plane specified by a correction target measurement value for each brightness for each brightness together with the correction coefficient.
If the correction plane coefficient is calculated together with the correction coefficient, the spatial position of the measurement value is corrected when the display image quality of a measured object such as a projector is inspected using a calibrated color measurement device. In comparison with the above, a correction coefficient for correcting the measured value can be calculated according to the brightness, and the measurement accuracy of the color measuring apparatus can be further improved.

Here, the color measurement device is configured to be able to switch the measurement range according to the brightness of the measurement object, and the calibration target measurement process and the reference instrument measurement process switch the brightness in two or more stages within each measurement range. It is preferable to perform measurement.
If measurement is performed by switching the brightness to two or more levels for each measurement range, the accuracy of the correction coefficient in each measurement range can be improved, and the measurement accuracy for each measurement range can also be improved.

At this time, when setting the brightness in each measurement range, it is preferable to set the brightness at the switching point of the measurement range. For example, when the range 1 for measuring the low illuminance area and the range 2 for measuring the high illuminance area are set, the measurement range switching point is the brightest point in the range 1 and the darkest point in the range 2. Means.
If correction coefficients are obtained using the switching points of Range 1 and Range 2 as calibration points, the measurement value error at the switching point can be reduced, and the measurement accuracy can be further improved.

Here, it is preferable that the color measuring device is a tristimulus value direct reading type color measuring device, and the reference unit is a spectral type color measuring device.
If a spectroscopic color measurement device is used as the reference device, the measurement accuracy of the reference device is improved, so that the measurement accuracy of the tristimulus value direct-reading color measurement device calibrated according to the reference device can also be improved.

Here, the measurement object includes a color lighting process for individually lighting red (RED), green (GREEN), and blue (BLUE), and the calibration target measurement process and the reference instrument measurement process individually light each color. Preferably, the correction coefficient calculating step calculates the correction coefficient for each brightness in each color.
By calculating the correction coefficient for each brightness of each color of red, green, and blue, it is possible to measure a measurement object capable of color display with high accuracy by individually controlling the lighting state of each color of red, green, and blue. .

  The calibration device for a color measuring apparatus according to the present invention includes a light path switching unit that switches and arranges a color measuring apparatus and a reference device to be calibrated on a path of light output from a measurement object, and the brightness of the measurement object is 2 Measuring object control means for switching and controlling in stages or more, calibration target measurement value acquiring means for acquiring measurement values of the color measuring device for each brightness of the measuring object, and measurement values of the reference device for measuring object brightness Reference unit measurement value acquisition means to be acquired every time, and correction coefficient calculation for calculating the correction coefficient for each brightness in the color measuring device to be calibrated based on the measurement value for the calibration target for each brightness of the measurement object and the reference unit measurement value And means.

  Also in the calibration apparatus of the present invention, since the correction coefficient is obtained with the brightness of two or more points, the measurement accuracy can be improved as compared with the case where the correction coefficient is obtained with only the brightness of one point. That is, in the present invention, since the correction coefficient can be changed depending on the brightness, it is possible to obtain a correction coefficient that matches the characteristics of the light receiving element of the tristimulus value direct reading type sensor compared to the prior art, and the highly accurate measurement. It can be performed.

  The color measurement method of the present invention is obtained in advance in a measurement value acquisition step of measuring a measurement object with a color measurement device and acquiring a measurement value, and a color measurement device calibration method according to any one of claims 1 to 5. A correction coefficient calculating step for calculating a correction coefficient for the measurement value from the correction coefficient for each brightness and the brightness of the acquired measurement value, and correcting the measurement value using the calculated correction coefficient A measurement value calculation step of outputting the measured value as measurement data.

  In the present invention, since the correction coefficient is obtained with the brightness of two or more points, the measurement accuracy can be improved as compared with the case where the correction coefficient is obtained with only the brightness of one point. That is, in the color measurement method of the present invention, since the correction coefficient can be changed depending on the brightness, it is possible to obtain a correction coefficient that matches the characteristics of the light receiving element of the tristimulus value direct reading type sensor compared to the conventional one, Highly accurate measurement can be performed.

Here, the correction coefficient calculating step includes a correction coefficient for the measurement value based on a spatial positional relationship between a correction plane coefficient corresponding to a correction coefficient for each brightness obtained in advance and a measurement point of the measurement value. Is preferably calculated.
In such a configuration, the correction plane coefficient in addition to the correction coefficient is stored for each calibrated brightness, and in the correction coefficient calculation step, the spatial positional relationship between the measurement point and each correction plane coefficient is determined. Since the correction coefficient is calculated based on this, even when the brightness of the measured value is different from the brightness at the time of calibration, it is possible to perform very high-precision correction, and to perform higher-precision measurement. it can.

  Here, in the correction coefficient calculation step, when the spatial position of the measurement point is larger than the correction plane when the brightness is brightest, the correction coefficient for the brightest case is selected, and the brightness is When the spatial position of the measurement point is smaller than the correction plane in the darkest case, the correction coefficient in the darkest case is selected, and the spatial position of the measurement point is between two correction planes It is preferable to calculate a correction coefficient by calculating a distance between the measurement point and each correction plane and adding a correction coefficient corresponding to each correction plane according to the ratio of the distance.

  According to such a configuration, particularly when the spatial position of the measurement point is between two correction planes, the distance between the measurement point and each correction plane is calculated, and each correction is performed according to the ratio of the distance. Since the correction coefficient is calculated by adding the correction coefficient corresponding to the plane, the correction coefficient corresponding to the brightness can be calculated, and the accuracy during color measurement can be improved.

  The color measurement apparatus of the present invention includes a correction coefficient storage unit that stores a correction coefficient for each brightness, a measurement value acquisition unit that measures a measurement target and acquires a measurement value that is color information, and the brightness measurement unit. Correction coefficient calculation means for calculating a correction coefficient for the measurement value from the correction coefficient and the brightness of the measurement value, the measurement value is corrected using the calculated correction coefficient, and the corrected measurement value is used as measurement data. And a measurement value calculation means for outputting.

Here, the correction coefficient storage means stores a correction coefficient for each brightness and a correction plane coefficient corresponding to the correction coefficient, and the correction coefficient calculation means is based on the measurement value in color information space coordinates. It is preferable to obtain a measurement point and calculate a correction coefficient for the measurement value based on a spatial positional relationship between the measurement point and each correction plane coefficient.
Each of these color measuring devices can achieve the same effects as the color measuring method.

FIG. 1 is a block diagram showing a configuration of a calibration apparatus according to an embodiment of the present invention.
As shown in FIG. 1, the calibration device 1 includes a calibration stage 4 on which a tristimulus value direct-reading sensor 2 and a reference device 3 are mounted as a color measurement device to be calibrated, a projector 5 as a measurement object, A tristimulus value direct-reading sensor 2, a reference device 3, a calibration stage 4, and a control device 10 that controls the projector 5 are configured.

As shown in FIG. 2, the tristimulus value direct reading sensor 2 includes a diffusion plate 21, RGB filters 22, a photodiode (photoelectric conversion element) 23, a primary correction circuit 24, and a secondary correction circuit 25. Is something.
The light emitted toward the tristimulus value direct-reading sensor 2 passes through the diffusion plate 21 and passes through the RGB filters 22. The light passing through each filter 22 is converted into an electrical signal by the photodiode 23. The converted electrical signal is subjected to amplifier adjustment on the primary correction circuit 24. At this time, the measurement range is determined by the gain of the amplifier. Then, the RGB signal is converted into tristimulus values XYZ by the secondary correction circuit 25. The tristimulus values XYZ are appropriately displayed on a display screen provided in the tristimulus value direct reading type sensor 2 and are configured to be output from an output terminal to an external control device 10. Therefore, the tristimulus value direct reading sensor 2 is configured to be able to directly read and output the color information of the emitted light as the tristimulus value XYZ.

As the reference device 3, a spectroscopic color measuring device capable of measuring a color with higher accuracy than the tristimulus value direct reading type sensor 2 is usually used, but a tristimulus value direct reading type sensor serving as a reference may be used. The measurement data of the reference device 3 can also be output to the control device 10 via the output terminal.
The reason why the tristimulus value direct reading sensor 2 is calibrated according to the reference device 3 is as follows. The tristimulus value direct reading type sensor 2 is less expensive than the spectroscopic type sensor. Therefore, if the tristimulus value direct reading type sensor 2 is used in the inspection process in the production line of the projector 5 or the like, many tristimulus value direct reading type sensors 2 can be prepared and the efficiency of the inspection process can be improved. At this time, by calibrating each tristimulus value direct reading type sensor 2 in accordance with the reference device 3, the variation (error) of the measured values of each tristimulus value direct reading type sensor 2 can be eliminated. It is possible to correctly evaluate the inspection object.

  The calibration stage 4 is configured to be slidable according to an instruction from the control device 10. Thereby, the tristimulus value direct reading type sensor 2 and the reference unit 3 on the calibration stage 4 can be alternately arranged on the front surface of the projector 5.

  The projector 5 is a measurement object that is measured and evaluated by the calibrated tristimulus value direct-reading sensor 2, and is a general projector that uses a liquid crystal element. The drive is controlled by the control device 10 during the calibration process. Yes.

Here, when the tristimulus value direct-reading sensor 2 is calibrated, it is also possible to calibrate using a calibration light source.
However, when measuring and evaluating a device using a liquid crystal element such as the projector 5 with the tristimulus value direct-reading sensor 2, the device to be measured is calibrated as in this embodiment. Is preferred.
That is, since the transmittance of the liquid crystal with respect to the wavelength varies depending on the applied voltage, the spectral shape of the light output varies depending on the applied voltage. There is no problem when a spectral sensor capable of grasping the spectral shape of light is used, but when measuring using the tristimulus direct reading sensor 2, the RGB balance of the light output from the projector 5 depending on the brightness. Will affect the measurement chromaticity obtained.
Therefore, in the present embodiment, the brightness of the projector 5 is switched to two or more stages and the tristimulus value direct-reading sensor 2 is calibrated to prepare a correction coefficient corresponding to each brightness as described later. And the above problem can be solved. Therefore, calibration is performed using the projector 5 to be measured.

The control device 10 includes a general computer including a CPU, a memory, and the like, and includes the following units that are executed by incorporating a predetermined program.
That is, the control device 10 includes a stage control unit 11 that controls the movement of the calibration stage 4, a measurement object control unit 12 that controls the lighting state of the projector 5 that is a measurement object, and three color measurement devices that are calibration objects. The measurement value acquisition means 13 for acquiring the measurement value of the stimulus value direct-reading sensor 2, that is, the tristimulus value XYZ, the reference device measurement value acquisition means 14 for acquiring the measurement value of the reference device 3, and the measurement values Correction coefficient calculation means 15 for calculating a correction coefficient based on the measurement value storage means for storing the calibration target measurement value and the reference instrument measurement value acquired by the calibration target measurement value acquisition means 13 and the reference instrument measurement value acquisition means 14 16 and the correction coefficient calculated by the correction coefficient calculation means 15 and the brightness of the projector 5 set by the measured object control means 12 when the correction coefficient is calculated are stored in association with each other. That and a correction coefficient storing means 17.

  Therefore, in this embodiment, the calibration stage 4 and the stage control means 11 constitute light path switching means for switching and arranging the tristimulus value direct reading type sensor 2 and the reference unit 3 on the light path from the projector 5. Has been.

Next, a calibration method of the tristimulus value direct reading type sensor 2 in the calibration device 1 of the present embodiment will be described based on the flowcharts of FIGS.
First, the inspector sets the tristimulus value direct-reading sensor 2 and the reference device 3 on the calibration stage 4 (step 1, hereinafter, step is abbreviated as “S”).

Next, the inspector operates the control device 10 to start the calibration work of the tristimulus value direct reading type sensor 2.
First, the control device 10 sets the brightness (applied voltage of the light source lamp) of the projector 5 to a predetermined brightness 1 by the measured object control means 12 (S2), and lights red (RED) (S3).
Then, the control apparatus 10 performs the measurement process process using the tristimulus value direct-reading type sensor 2 and the reference device 3 (S10).

In the measurement processing step S10, the stage control means 11 of the control device 10 slides the calibration stage 4 so that the tristimulus value direct reading type sensor 2 comes to the front of the projector 5 (S11).
Then, the calibration target measurement value acquisition unit 13 of the control device 10 acquires the measurement value measured by the tristimulus value direct reading sensor 2, that is, the tristimulus value XYZ, and stores it in the measurement value storage unit 16 (S12).

Next, the stage control means 11 of the control device 10 slides the calibration stage 4 so that the reference unit 3 comes to the front of the projector 5 (S13).
Then, the reference unit measurement value acquisition unit 14 of the control device 10 acquires the measurement value measured by the reference unit 3, that is, the tristimulus value XYZ, and stores it in the measurement value storage unit 16 (S14).
As described above, the measured values obtained by the tristimulus value direct reading sensor 2 and the reference device 3 having a predetermined brightness (for example, brightness 1) and a predetermined color (for example, RED) are acquired and stored, and the measurement processing step S10 is completed. To do.

Subsequently, the measured object control means 12 of the control device 10 controls the projector 5 to light green (GREEN) with the predetermined brightness 1 (S4).
And the control apparatus 10 performs again the measurement process process using the tristimulus value direct reading type | mold sensor 2 and the reference | standard device 3 (S10). As a result, the measurement values obtained by the tristimulus value direct reading sensor 2 and the reference unit 3 of GREEN having the brightness 1 are acquired and stored.

Next, the measured object control means 12 of the control device 10 controls the projector 5 to light blue (BLUE) with the predetermined brightness 1 (S5).
And the control apparatus 10 performs again the measurement process process using the tristimulus value direct reading type | mold sensor 2 and the reference | standard device 3 (S10). Thereby, each measurement value by the tristimulus value direct-reading sensor 2 and the reference unit 3 of brightness 1 and BLUE is acquired and stored.

Next, the control device 10 determines whether the brightness of the projector 5 controlled by the measured object control means 12 is “brightness 1” (S6).
If the brightness is 1, the brightness of the projector 5 controlled by the measured object control means 12 is set to “brightness 2” (S7).

And the control apparatus 10 performs said S3-S6 again. That is, by sequentially turning on each color of red, green, and blue at “brightness 2” and repeating the measurement processing step S10, measured values (tristimulus values) of each color (R, G, B) of “brightness 2” ) Is acquired and stored in the measured value storage means 16.
In S6, since the brightness is “brightness 2”, “No” is determined.

Then, the control apparatus 10 calculates a correction coefficient and a correction plane coefficient by the correction coefficient calculation means 15 (S8). That is, the correction coefficient calculation means 15 includes a color conversion matrix M that becomes a correction coefficient from the measurement value of the tristimulus value direct reading sensor 2 and the measurement value of the reference device 3 stored in the measurement value storage means 16, and the correction plane coefficient a. , B, c, d are obtained.
For example, the correction coefficient calculation means 15 obtains the color conversion matrix M ₁ when measured with “brightness 1” in RED, GREEN, and BLUE single colors by the following equation (1).

However, in the equation (1), the measured value at the time of RED measurement is X _1-R , Y _1-R , Z _1-R , and the measured value at the time of GREEN measurement is X _1-G , Y _1-G , Z _1- The measurement values at the time of _G and BLUE measurement are X _1-B , Y _1-B and Z _1-B, and the measurement values of the reference devices at that time are X _REF1-R , Y _REF1-R , Z _REF1-R , respectively. Let _XREF1-G , _YREF1-G , _ZREF1-G , _XREF1-B , _YREF1-B , and _ZREF1-B .

Further, correction plane counts a ₁ , b ₁ , c ₁ , and d ₁ when measured at “brightness 1” in RED, GREEN, and BLUE single colors are defined as shown in Expression (2).

Next, the correction coefficient calculation means 15 obtains the color conversion matrix M ₂ and the correction plane counts a ₂ , b ₂ , c ₂ , and d ₂ using the measurement values measured at “brightness 2”.
In the case where measurement is performed at other brightness, the color conversion matrix M and the correction plane coefficients a, b, c, d are similarly obtained for every measured brightness.

The correction coefficient calculation means 15 stores the obtained correction coefficient (color conversion matrix M) and correction plane coefficient in the correction coefficient storage means 17 (S8).
Note that correction coefficient storage means may be provided inside the tristimulus value direct reading sensor 2 so that the correction coefficient and the correction plane coefficient may be directly stored in the tristimulus value direct reading sensor 2.
Further, in the case where an inspection control device for controlling the tristimulus value direct-reading sensor 2 arranged on the production line of the projector 5 is provided, a correction coefficient storage means is provided in the inspection control device so that a correction coefficient or a correction plane is provided. The coefficient may be stored. That is, in the case of a commercially available general tristimulus value direct reading type sensor, a correction coefficient storage means is not usually prepared. For this reason, the correction coefficient storage means may be provided in the inspection control apparatus that controls the tristimulus value direct reading type sensor 2. The control device 10 may be used as an inspection control device as it is.

By calculating such a correction coefficient, as shown in FIG. 6, the measurement points 111 and 112 having brightness 1 and 2 are corrected to points 113 and 114 on the dotted line 100, respectively, and the tristimulus value direct reading type is obtained. The measured value of the sensor 2 can be adjusted to the reference device 3.
Thus, the calibration process for matching the measured value of the tristimulus value direct reading sensor 2 with the measured value of the reference device 3 is completed. Therefore, in this embodiment, in each flowchart shown in FIGS. 4 and 5, the calibration target measurement process is configured by S2 to S7, S11, and S12, and similarly, the reference instrument measurement process is configured by S2 to S7, S13, and S14. In S8, the correction coefficient calculation step is configured.

Next, a color measurement method using the tristimulus value direct-reading sensor 2 for which calibration work has been completed will be described.
In this embodiment, as shown in FIG. 7, a commercially available general tristimulus value direct reading sensor 2 is used, and an output value (tristimulus value) from the tristimulus value direct reading sensor 2 is configured by a computer. The inspection control device 30 performs processing.
Therefore, the inspection control device 30 includes an inspection target control unit 31 that controls the projector 5A to be inspected, and a correction coefficient storage unit 32 that stores the corrected correction coefficient and correction plane coefficient of the tristimulus value direct-reading sensor 2. A measurement value acquisition means 33 for acquiring a measurement value (tristimulus value) of the tristimulus value direct reading sensor 2, a correction coefficient or a correction plane coefficient stored in the correction coefficient storage means 32, and the acquired measurement value A correction coefficient calculation means 34 for calculating a correction coefficient using the correction value, and a measurement value calculation means 35 for correcting the measurement value using the calculated correction coefficient and outputting the measurement data calculated by the correction.
Further, an inspection result output device 36 such as a display or a printer for displaying the measurement values (tristimulus values) output by the measurement value calculation means 35 is connected to the inspection control device 30.

  It is assumed that the correction coefficient storage means 32 stores a correction coefficient and a correction plane coefficient when calibration is performed at two points of “brightness 1” and “brightness 2”. At this time, it is assumed that “brightness 2” has higher illuminance than “brightness 1”.

The inspection control device 30 first controls the driving of the projector 5A by the inspection object control means 31 (S31).
Next, the measurement value acquisition means 33 acquires the color information (measurement value) of the inspection object (projector 5A) measured by the tristimulus value direct reading sensor 2 (S32). The correction coefficient calculation unit 34 calculates a correction coefficient (color conversion matrix M) using the acquired color information (tristimulus value XYZ) and the correction coefficient and correction plane coefficient stored in the correction coefficient storage unit 32. (S33). Then, the measurement value calculation means 35 calculates the measurement value by correcting it using the calculated correction coefficient, and outputs the calculated measurement value to the inspection result output device 36 (S34).
Therefore, in this embodiment, the measurement value acquisition step of the color measurement method is configured in S32, the correction coefficient calculation step is configured in S33, and the measurement value calculation step is configured in S34.

Next, the correction coefficient calculation step S33 executed by the correction coefficient calculation means 34 will be described.
When the color conversion matrix (correction coefficient) obtained by the “brightness 1” calibration is M ₁ and the color conversion matrix obtained by the “brightness 2” calibration is M ₂ , the color conversion matrix M is as shown in FIG. The case is divided into 3 patterns. At this time, each correction plane can be expressed by the correction plane coefficients a, b, c, and d. M = M ₁ when the spatial position of the measurement value is larger than the correction plane obtained with “brightness 2”, and M when the spatial position of the measurement value is smaller than the correction plane obtained with the brightness 1 = M ₂ , when the spatial position of the measurement point is between the correction plane obtained with brightness 1 and the correction plane obtained with brightness 2, an intermediate correction value M is calculated between M ₁ and M ₂ To do.

Then, in the measurement value calculation step S34, the measurement value calculation means 35 applies the case-dependent color conversion matrix M to the equation (3), and finally calculates the corrected measurement values X _OUT , Y _OUT , Z _OUT . Ask. However, the measured values obtained are X, Y, and Z.

Hereinafter, a specific calculation method of the color conversion matrix M by the correction coefficient calculation unit 34 will be described.
In order to calculate the color conversion matrix M, it is necessary to know where the measured point is relative to the correction plane. Therefore, as shown in FIG. 10, the obtained measurement value (measurement point P) is plotted in the XYZ space coordinates. At this time, intersection points P ₁ and P ₂ when a perpendicular is dropped from the measurement point P toward each correction plane are obtained.
That is, the measurement value obtained above is P = (X, Y, Z), and the intersection point P ₁ when the perpendicular is dropped from the measurement point P to the “brightness 1” correction plane is expressed by the following equation (4). It can be obtained by solving the simultaneous equations.

Similarly, the intersection point P ₂ when a perpendicular is dropped from the measurement point P to the “brightness 2” correction plane is obtained, and the position of the measurement point P from the obtained intersection points P ₁ and P ₂ is verified. Specifically, the distances D, D ₁ and D ₂ from the origin are calculated at the measurement point P and the intersection points P ₁ and P ₂ , and the positional relationship between the measurement point and the correction plane is obtained based on the magnitude relationship.

From the distances D, D ₁ and D ₂ obtained as described above, the respective color conversion matrices M are obtained by the following equation (5). Here, e ₁ is the distance between the measurement point P and the low illuminance (brightness 1) correction plane, and e ₂ is the distance between the measurement point P and the high illuminance (brightness 2) correction plane.

By adopting the obtained color conversion matrix M in the equation (3), the measured value measured by the tristimulus value direct reading type sensor 2 can be corrected to the measured value matched with the reference device 3, and finally Tristimulus values X _OUT , Y _OUT and Z _OUT can be obtained.

According to this embodiment, there are the following effects.
(1) When the tristimulus value direct-reading sensor 2 is calibrated according to the reference device 3, the measured value is not calibrated and calibrated with only one brightness as in the prior art, but switched to a plurality of brightness levels. The tristimulus value direct-reading sensor 2 and the reference device 3 measure each brightness, and the correction coefficient is calculated for each brightness. Therefore, the light receiving element (photodiode 23) of the tristimulus value direct-reading sensor 2 is calculated. A correction coefficient suitable for the characteristics can be obtained. For this reason, the measurement error of the tristimulus value direct-reading sensor 2 can be reduced and more accurate measurement can be realized as compared with the conventional case where calibration is performed with only one brightness.

(2) Further, the tristimulus value direct reading sensor 2 is calibrated by measuring the light from the projector 5 to be measured by the tristimulus value direct reading type sensor 2 and the reference device 3, and the measurement target Calibration is performed using the projector 5. For this reason, even when measuring devices such as liquid crystal panels that change the spectral shape of the output light when the gradation is varied, calibration can be performed in a state that reflects the change in the spectral shape. it can. Therefore, the tristimulus value direct-reading sensor 2 calibrated in this embodiment can realize highly accurate chromaticity measurement for the projector 5 to be measured.

(3) Furthermore, in this embodiment, when the tristimulus value direct reading sensor 2 is calibrated, the correction plane coefficients for the respective brightnesses 1 and 2 are also stored, and the calibrated tristimulus value direct reading sensor 2 is stored. When the measurement target is measured, the measured values are plotted in XYZ spatial coordinates, the positional relationship between each correction plane and the measurement point P is obtained, and the color conversion matrix M is obtained according to the positional relationship. For this reason, even if the brightness of the actual measurement object is different from the brightness 1 and 2 at the time of calibration, a correction coefficient (color conversion matrix M) corresponding to the brightness is calculated and used by linear interpolation. Therefore, highly accurate chromaticity measurement can be realized.

(4) Since the correction coefficient is calculated according to the brightness at the time of measurement, the brightness switching when the tristimulus value direct-reading sensor 2 is calibrated according to the reference device 3 is the same as that of the present embodiment. Thus, sufficient effects can be obtained even in two stages. Therefore, it is not necessary to perform the calibration process by switching the brightness to three or more levels, and the calibration process of the tristimulus value direct reading type sensor 2 can be performed easily and in a short time.

The present invention is not limited to the above embodiment.
For example, in the above-described embodiment, the calibration is performed only with the two levels of brightness 1 and 2, but the calibration process may be performed by switching the brightness to three or more levels. The more brightness steps, the longer the calibration process takes, but the accuracy of the correction coefficient is improved, and the calibrated tristimulus value direct reading sensor 2 can perform chromaticity measurement with higher accuracy.
However, in the above-described embodiment, the color conversion matrix M is corrected by linear interpolation between the brightness levels 1 and 2, so that sufficient measurement accuracy is ensured even if calibration is performed with only the brightness levels 1 and 2 at two points. it can.

  In the embodiment, when the measured value is between brightness 1 and 2, the color conversion matrix M is calculated by linear interpolation based on the distance from the measurement point P to each correction plane. Other interpolation methods such as spline interpolation may be employed.

In the embodiment, after setting the brightness to “brightness 1”, each color is sequentially switched to perform the measurement processing step S10. For example, in the state where red is lit, each brightness 1, 2 is set. The measurement processing step S10 may be performed while switching the lighting, and then the measurement processing step S10 may be performed by changing the lighting color and sequentially switching the brightness.
Furthermore, in the tristimulus value direct-reading sensor 2 to be calibrated, after the measurement values are acquired by sequentially switching the brightness and color, the calibration stage 4 may be moved to perform the measurement in the reference device 3.
In short, it is only necessary to obtain the measured values of the tristimulus value direct-reading sensor 2 and the reference device 3 for each color and brightness, and the order is not limited to the above embodiment.

  The light path switching means is not limited to the one that moves the calibration stage 4, but may be one that uses a reflecting mirror or the like that moves on the projector 5 side or switches the light path from the projector 5.

Further, when the tristimulus value direct-reading sensor 2 is configured to be able to switch the measurement range, the calibration process may be performed by switching the brightness in two or more steps for each measurement range.
In this case, it is preferable to perform the calibration process by setting the brightness of the measurement range switching point. For example, when the tristimulus value direct-reading sensor 2 is configured to be switchable between a range 1 for measuring a low illuminance region and a range 2 for measuring a high illuminance region, the brightest point in the range 1 and the other points Switch to a point (preferably the darkest point or its neighboring point so that the change in brightness is large), and in range 2 the darkest point and other points (preferably the brightest so that the change in brightness is large) Switching to a point or a point in the vicinity thereof, and the calibration process may be performed by measuring with the tristimulus value direct reading sensor 2 and the reference unit 3.
If correction coefficients are obtained using the switching points of Range 1 and Range 2 as calibration points, the measurement value error at the switching point can be reduced, and the measurement accuracy can be further improved.

  In the above embodiment, calibration is performed using the projector 5 to be measured. However, calibration may be performed by measuring a standard light source or the like with the tristimulus value direct-reading sensor 2 and the reference unit 3. However, when a measurement object whose spectrum changes according to brightness, such as a liquid crystal product such as a liquid crystal projector 5, a liquid crystal projection television, or a liquid crystal monitor, is to be measured as in the above embodiment. This is particularly effective in that it can be calibrated taking into account changes in the spectrum.

In the above-described embodiment, the inspection control device 30 is provided, and the correction coefficient calculation unit 34 and the measurement value calculation unit 35 of the inspection control device 30 calculate the correction coefficient according to the brightness of the measurement value and the measurement value of the calculated correction coefficient. The tristimulus value direct reading sensor 2 is provided with the correction coefficient storage means 32, the correction coefficient calculation means 34, and the measurement value calculation means 35, and the tristimulus value direct reading sensor 2 calculates the correction coefficient. Application processing to the measurement value may also be performed.
However, when the inspection control device 30 is used as in the above-described embodiment, a general tristimulus value direct-reading sensor 2 that does not include the correction coefficient storage unit 32, the correction coefficient calculation unit 34, and the measurement value calculation unit 35 is used. Therefore, there is an advantage that the measured values can be accurately corrected in various types of tristimulus value direct reading type sensors 2.

The tristimulus value direct-reading sensor 2 calibrated according to the present invention is not limited to the one used for quality evaluation of liquid crystal products, but can be used for color evaluation of various things.
Furthermore, the calibration method of the present invention is not limited to a tristimulus value direct-reading color meter, but can be applied to a tristimulus value direct-reading illuminometer / luminance meter, chromaticity calibration of 3 CCD cameras, and the like.

Further, the calibration method of the present invention is not limited to the calibration of the tristimulus value direct-reading type color measuring apparatus, but can be used for the calibration of other types of color measuring apparatuses.
In short, the calibration method, calibration device, color measurement method, and color measurement device of the present invention can be used for inspection of display devices such as liquid crystal panels, plasma displays, and EL displays, and display devices and products using them. Needless to say, even if these are used, they are not excluded from the scope of the present invention.

The block block diagram of the calibration apparatus by embodiment of this invention. The block block diagram of a tristimulus value direct-reading type sensor. The block block diagram of the control apparatus of a calibration apparatus. The flowchart which shows the procedure of the calibration method in a calibration apparatus. The flowchart which shows the measurement process process in a calibration method. The graph which shows the relationship between each measured value of a tristimulus value direct-reading type sensor and a reference | standard device. The block block diagram of a color measuring device. The flowchart which shows the color measurement method in a color measuring device. The figure explaining the case classification of a color conversion matrix. The figure explaining the spatial position of a measurement point. The graph which shows the relationship between each measured value of the tristimulus value direct-reading type sensor and reference | standard device in the conventional calibration method.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Calibration apparatus, 2 ... Tristimulus value direct reading type sensor, 3 ... Reference | standard, 4 ... Calibration stage, 5 ... Projector, 10 ... Control apparatus, 11 ... Stage control means, 12 ... Measuring object control means, 13 ... Calibration object Measurement value acquisition means, 14 ... reference device measurement value acquisition means, 15 ... correction coefficient calculation means, 16 ... measurement value storage means, 17 ... correction coefficient storage means, 30 ... inspection control device, 31 ... inspection object control means, 32 ... Correction coefficient storage means 33... Measurement value acquisition means 34. Correction coefficient calculation means 35. Measurement value calculation means 36.

Claims (11)

A calibration target measurement step of arranging a color measuring device to be calibrated on the path of light output from the measurement object, switching the brightness of the measurement object to two or more levels, and obtaining a measurement value for each switched brightness;
A reference device measuring step that arranges a reference device on the path of light output from the measured object, switches the brightness of the measured object to the same brightness as the calibration target measuring step, and acquires a measurement value for each brightness When,
A correction coefficient calculation step of calculating a correction coefficient for each brightness in the color measuring device to be calibrated based on the measurement values for calibration and the reference unit measurement values for each brightness;
A method for calibrating a color measuring apparatus, comprising: The color measuring device calibration method according to claim 1,
The color correction apparatus calibration method, wherein the correction coefficient calculation step calculates a correction plane coefficient representing a correction plane specified by a correction target measurement value for each brightness for each brightness together with the correction coefficient. In the calibration method of the color measuring device according to claim 1 or 2,
The color measuring device is configured to be able to switch the measurement range according to the brightness of the measurement object,
A calibration method for a color measuring apparatus, wherein the calibration target measurement step and the reference device measurement step perform measurement by switching the brightness in two or more steps within each measurement range. In the calibration method of the color measuring device according to any one of claims 1 to 3,
The color measuring apparatus is a tristimulus value direct reading type color measuring apparatus, and the reference device is a spectral type color measuring apparatus. In the calibration method of the color measuring device according to any one of claims 1 to 4,
A color lighting process for individually lighting red, green, and blue in the measurement object,
The calibration object measurement step and the reference device measurement step are executed each time each color is lit individually,
The color correction apparatus calibration method, wherein the correction coefficient calculation step calculates a correction coefficient for each color brightness. A light path switching means for switching and arranging the color measuring device and the reference device to be calibrated on the light path output from the measurement object;
A measured object control means for controlling the brightness of the measured object by switching between two or more stages;
Calibration target measurement value acquisition means for acquiring the measurement value of the color measurement device for each brightness of the measurement object;
Reference device measurement value acquisition means for acquiring the measurement value of the reference device for each brightness of the measurement object;
A correction coefficient calculating means for calculating a correction coefficient for each brightness in the color measuring device to be calibrated based on the measurement value for calibration and the measurement value for the reference device for each brightness of the measurement object;
A calibration apparatus for a color measuring apparatus, comprising: A measurement value acquisition step of measuring a measurement object with a color measurement device and acquiring a measurement value;
6. The correction coefficient for the measurement value is calculated from the correction coefficient for each brightness obtained in advance in the color measuring device calibration method according to claim 1 and the brightness of the acquired measurement value. A correction coefficient calculation step;
A measurement value calculation step of correcting the measurement value using the calculated correction coefficient, and outputting the corrected measurement value as measurement data;
A color measuring method comprising: The color measurement method according to claim 7,
The correction coefficient calculation step calculates a correction coefficient for a measurement value based on a spatial positional relationship between a correction plane coefficient corresponding to a correction coefficient for each brightness obtained in advance and a measurement point of the measurement value. A color measurement method characterized by the above. The color measurement method according to claim 8,
The correction coefficient calculation step includes
When the spatial position of the measurement point is larger than the correction plane when the brightness is brightest, select the correction coefficient for the brightest case,
When the spatial position of the measurement point is smaller than the correction plane when the brightness is the darkest, select the correction coefficient for the darkest case,
When the spatial position of the measurement point is between two correction planes, the distance between the measurement point and each correction plane is calculated, and a correction coefficient corresponding to each correction plane is added according to the ratio of the distance. And a correction coefficient is calculated. Correction coefficient storage means for storing a correction coefficient for each brightness;
A measurement value acquisition means for measuring a measurement object and acquiring a measurement value that is color information;
Correction coefficient calculation means for calculating a correction coefficient for the measurement value from the correction coefficient for each brightness and the brightness of the measurement value;
A measurement value calculating means for correcting the measurement value using the calculated correction coefficient and outputting the corrected measurement value as measurement data;
A color measuring device comprising: The color measuring device according to claim 10.
The correction coefficient storage means stores a correction coefficient for each brightness and a correction plane coefficient corresponding to the correction coefficient,
The correction coefficient calculation means calculates a measurement point based on the measurement value in color information space coordinates, and calculates a correction coefficient for the measurement value based on a spatial positional relationship between the measurement point and each correction plane coefficient. Characteristic color measuring device.