JPH067070B2 - Color determination device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a color determination device capable of performing color determination even when the distance to a target object changes.

[Prior Art] As a method of measuring the color of an object, there are a spectroscopic colorimetric method and a stimulus value colorimetric method. In the former method, it is possible to obtain data for each wavelength by using monochromatic light, and by using the L ^* a ^* b ^* color system specified by CIE, highly accurate color difference (Δ
Although E ^* ) can be displayed, the manufacturing cost is high and the device is large, which makes it difficult to apply to a general production line. On the other hand, the latter method is applied to many production lines where simple color identification is required because a color light receiving photodiode is used for the sensing device. Some of these are designed to display color difference like the former, but the former (ΔE ^* is 1
Compared to (/ 100 level), the performance is not good in terms of colorimetry. However, since the system is simple and the device itself is inexpensive, it is often used in a general color discrimination process.

The latter problem of this stimulus colorimetric method will be described in more detail.

The stimulus colorimetry method using a photodiode for color light reception is designed to improve the accuracy of color discrimination by blocking external light, the illuminance on the object surface is 10000 to 300001x, the distance between the light source and the object, and the light receiving unit from the object. The color was measured under conditions such as specifying the distance to. When the sensor is used under these conditions, the following problems occur in its practical use.

The condition is because the surface of the object to be measured must be completely optically isolated from the outside in order to prevent ambient light, and in that sense, the sensor section and the object are in contact with each other. Visual sensors, including color sensors, are originally
Generally, sensing is performed at a position away from the object. In the contact type, there is a risk of scratching or attaching dirt to the target object during measurement, and therefore it is preferable to measure the color under non-contact conditions as much as possible. However, even in the non-contact state, it has a correlation with the color discrimination accuracy. In general, measures such as irradiating the illuminance surface under high illuminance conditions of 10000 to 300001x to minimize the ratio of the photocurrent of the color light receiving element due to external light or putting the production line itself in a dark box are taken. Has been.

Next, when the object under high illuminance of 10000 to 300001x is sensed under the condition of 1, the aging of the light receiving element is likely to occur, which may lead to deterioration of the performance of the sensor.
The colorimetric conditions for humans are generally 500 to 15001x.
The colorimetric sensor is preferably designed to be as close to this colorimetric condition as possible.

Under the above condition, for example, if the distance changes by several mm, the error rate of color determination increases at present, which is a problem that must be improved.

[Problems to be Solved by the Invention] The present invention has been made for the purpose of ameliorating the drawbacks in the case of performing color determination using these color light receiving elements, and in particular, general fluorescent lamps and the like have been proposed. It is an object of the present invention to provide a color determination device capable of performing color determination even if the distance to a target object to be subjected to color determination changes to some extent under illumination by another illumination device.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a sensor which is arranged at an arbitrary distance from an object to be colorimetric, and a computer which processes an output of the sensor. The sensor is
The three-color separation type main sensor formed by a light-receiving element having sensitivity to tristimulus values of X, Y, and Z, and the sub-sensor formed by a light-receiving element having sensitivity to visible light are used. The chromaticity value obtained from the detected tristimulus values, the output of the sub sensor, and the ratio of the output of the sub sensor and the red component X are used as the items for color determination, and at least a plurality of these items are calculated by the computer. It employs a means of providing a function of making color judgment by comparing with a value stored in advance in a memory.

[Operation] In the color determination device having such a configuration, the white surface is placed at the position of the color measurement target object, and the distance l between the sensor and the white surface is set within an appropriate range while illuminating with a fluorescent lamp or the like. The values of the three stimulus values and the outputs of the sub-sensors obtained when the color sensor was moved with were taken into a computer, and the sensor output when an arbitrary color material was shown was obtained by changing the distance 1 in the same manner. The color judgment item, that is, the chromaticity value obtained from the tristimulus value, the output of the sub sensor, and the ratio of the output of the sub sensor and the red component X are stored in the memory of the computer.

Thus, for the color measurement target object, at least a plurality of items of the color determination items obtained by detecting the tristimulus value by the main sensor and the output of the sub sensor,
The color judgment is performed by comparing with the value stored in advance in the memory of the computer.

[Embodiment] FIG. 1 shows a configuration of an embodiment of the present invention.

As shown in FIG. 1, a colorimetric object (hereinafter referred to as “object”) 1 is placed in a dark box 2. However, the dark box does not strictly block external light. An illumination device 3 such as a fluorescent lamp is placed at a suitable distance from the object 1.
Put. Further, the sensor 4 mounted on the sensor base 5 is installed in front of the object 1 at an arbitrary distance l. The output of the sensor 4 is processed by an electric processing circuit and input to a computer.

Next, the configuration and operation of the sensor 4 and the like will be described in detail.

FIG. 2 shows a state in which the sensor 4 is viewed from the direction of the object 1. This sensor 4 is arranged at the center of a cylindrical edge frame 11, and a three color separation type main sensor 13 and a light receiving sensor 14 which is its sub sensor are patterned on a SnO ₂ -Si chip 12. ing. The edge frame 11 is provided to prevent direct light from the lighting device 3 from entering the main sensor 13 and the light receiving sensor 14, and if the shelter or the like covers the periphery of the fluorescent lamp, the surface of the object 1 is covered. If the structure is such that only the light of the fluorescent lamp is irradiated to the inside, especially the edge frame 11
Does not need.

The main sensor 13 in FIG. 2 is a light receiving element having sensitivity to tristimulus values of X, Y, and Z, and the sub sensor 14 is a light receiving element having sensitivity to visible light.

The main sensor 13 and the sub sensor 14 should be installed as close to each other as possible. With respect to this arrangement, in FIG. 2, it is drawn like a three-color separation type color light receiving element, but each sensor may be located at any position. In addition, SnO ₂ -S
The main sensor 13 and the sub sensor 14 can be integrated on the i-chip 12, but this may also be a discrete optical element, for example a photodiode. However, the discriminating ability is improved when they are brought as close as possible. In that case, it is necessary to use the optical elements of the same lot.

FIG. 3 shows an example of an electric processing circuit including a computer.

The photocurrents corresponding to the tristimulus values of X, Y, and Z received by the main sensor 13 are input to separate electric processing circuits, that is, only one electric processing circuit is shown, that is, respectively. After being converted to a voltage by the current-voltage conversion circuit, the commercial frequency of the fluorescent lamp (50H
It is input to the low-pass circuit for cutting 100Hz which is the fluctuation component due to z), and further enters the amplifier that calibrates the output voltage value, and each calibration is performed. The details of the calibration will be described later. Further, the output of the amplifier at the final stage of the electric processing circuit is input to the computer via the A / D converter.

Since the electric processing circuit has the same configuration as that of the sub sensor 14, the description of the electric processing circuit of the sub sensor 14 is omitted.

Next, the function of each of the above-described devices and the mode of color determination by them will be described.

First, after installing the illuminating device 3 such as a fluorescent lamp in an arbitrary place, the reference white surface is placed at the object position in FIG.
Each output value from the sensor 4 located at a distance of 1 from the object position is taken into a computer through an electric processing circuit. At this time, the level of the main sensor 13 corresponding to the three stimulus values of X, Y, and Z is set to the same level by the amplifier at the latter stage of the low-pass circuit in FIG. The calculator receives the output value and calculates the following chromaticity value.

Of the above equations, the former two equations correspond to x and y (x axis, y axis) of x, y chromaticity coordinates that are commonly used for evaluating colors. When the object is white, x = y = z, so that x = 0.33 and y = 0.33.

Next, in this state, the object 1 is changed from white to another arbitrary color material, the color is presented to the sensor 4, x and y for each color are calculated, and several times of sampling are performed. By doing so, the variation is checked, the range is set as a threshold value, and it is stored in the computer. In the experiment, an FET input type, low offset voltage type amplifier (input impedance 1 TΩ, input offset voltage 0.5 mV or less) is used for the current-voltage conversion circuit, and a circuit at the subsequent stage also uses an amplifier having a low offset voltage, Moreover, it was found that the color judgment of more than 30 colors is possible when using the parts with the smallest variation in resistance and capacitor.

On the other hand, the distance l from the object 1 to the sensor 4 in FIG.
In general, it is expected that there will be large changes, that is, parts that flow one after another in a certain production line will naturally have a positional deviation of several mm or more. Of course, although it depends on the amount of change in the distance, for example, when the amount of change is about 70 mm to 240 mm, it is almost impossible to make a determination with the existing discriminating apparatus.
This is because the relative spectral characteristics and sensitivity of the sensor itself, the brightness of the object 1, etc. change, and when a certain color A is shown, the computer output values x _A and y _A vary greatly,
This is because it becomes impossible to determine that the color is A.

The sub sensor 14 is for coping with such a problem, and by using the sub sensor 14, at least
13 colors or more can be discriminated under a fluorescent lamp, and l = 70 to 24
It can be performed in the range of 0 mm.

Here, the operation of the sub sensor 14 will be described in more detail.

As described above, a white surface is placed at the position of the object 1 in FIG.
, When the values of X and Y when moved within the range of l = 70 to 240 mm are taken into the computer, the output of the sub sensor 14 is also obtained, and similarly, the object 1 made of an arbitrary color material is shown. Similarly, the output of the sub sensor 14 in the case of
Store them in the computer's memory. The output of the sub-sensor 14 is approximately proportional to the total value of the three stimulus values of X, Y and Z. By using this sub-sensor output,
More accurate value can be obtained.

At the time of actual color measurement on the production line etc., for the color material flowing on the belt conveyor etc., the above sub sensor
The brightness level is constantly monitored based on the output of 14 and when it exceeds the range of the output level of the sub-sensor in the range of l = 70 to 240 mm stored in the memory of the computer, the color determination impossible signal is output. .

In addition, the values of x and y obtained from the tristimulus values of X, Y, and Z detected by the main sensor 13 and the output of the sub sensor 14, and those stored in the memory of the computer with a threshold value set in advance. The color of the coloring material is determined by comparing the value with the value. In performing this comparison, the output of the sub-sensor when the distance 1 is changed is the lightness information for that color. By setting this lightness as a threshold value and using it as an item for color determination, 10 or more colors Can be determined.

Furthermore, in order to increase the number of judgment colors, consideration is given to increase the number of judgments of blue colors. Explaining the method, the blue system has a relatively low absolute sensitivity of the sensor and is a color that is relatively difficult to determine. For example, when determining “purple blue” and “blue”, x of x and y is simply determined. It is difficult to discriminate only by the value of (red line). The reason for this is that the values of x and y are all relative values, and (x + y + z = 1).
As the value of becomes smaller, the values of y and z become relatively larger. This is because the blue component appears very emphasized in both blue and purple, and the red component is not so different.

In order to cover this situation, in the present invention, the ratio between the output S of the sub sensor 14 and the red component X is taken and used as a reference for discrimination between blue and purple systems. Of course, the comparison between the ratio obtained by the detection by the main sensor 13 and the sub sensor 14 and the value previously stored in the memory of the computer will be performed by the computer. Thus, the greater the purple component, the greater the X / S. By using this value as a reference for determination, it is possible to determine 13 or more colors even if the distance between the sensor 4 and the object 1 is changed to 70 to 240 mm under normal illumination such as a fluorescent lamp. .

Table 1 shows the judgment items when the target color is 13 colors. All values of x, y, z and S, X / S may be stored in the program of the computer, but since the program becomes long, it is better to suppress the judgment items as much as possible. The ∘ mark in Table 1 indicates the judgment items actually used to distinguish each color in the table. These circles are obtained by experiments for the purpose of reducing the determination time as much as possible.

Therefore, in the color determination of various objects, the upper and lower limit values of each determination item from white to blue in Table 1 obtained through the electric processing circuit (FIG. 1) in advance, that is, from white to blue in the table, For each color, the distance between the sensor 4 and the object 1 is changed from the lower limit (70 mm) to the upper limit (240 mm), and the upper and lower limits of the judgment items marked with ○ in the table are stored in the memory of the computer. Next, in the actual judgment, the values of the five judgment items obtained from the outputs of the main sensor and the sub sensor are the upper and lower limit values of the judgment items marked with a circle of any color stored in the memory of the computer. By checking for range, the color of the object is identified in a very simple way.

FIG. 4 to FIG. 8 show the results of the experiment, in which R, G, B, S, when 13 color materials are shown under the illumination of the fluorescent lamp while changing the distance l. And X / S are shown. As can be seen from these figures, for example, using the data in FIG. 4, red can be distinguished from other colors relatively easily, but it is difficult to distinguish yellow and pink. By using the data in FIGS. 5 and 6, it is possible to easily discriminate between yellow and pink. However, it is difficult to discriminate a large number of colors only with R, G, and B, and it is understood that the discrimination ability including blue and purple can be enhanced by adding S and X / S as discrimination items. .

Generally, the chromaticity value can be obtained only from the output of the main sensor, but as a result of the distance between the sensor and the measurement object being limited, it becomes impossible to make a determination due to a change in the distance,
There is a need to increase the illuminance of the light source more than necessary. The present invention solves this problem by the above means.

That is, when obtaining the chromaticity value, X + Y + Z is generally treated as a part of the total light amount, but this is not the total light amount.
Further, X / (X + Y + Z) is conveniently calculated because the calculated value is treated as an anonymous number. Then, the ratio X / S of the outputs of the red component of the sub sensor indicating the total light amount and the main sensor
Is obviously different from X / (X + Y + Z). Here, the reason why the output of red is targeted is that the output of the red component is large, and a subtle difference of red is effective in the determination in the stomach or the like.

Further, as shown in FIG. 4 to FIG. 8, by adding a comparison item in which a difference actually occurs as a color determination item, it is possible to take a large range of the upper limit value and the lower limit value of each item. Redundancy with respect to measurement conditions is significantly improved, and color determination is possible even under bad lighting conditions such as fluorescent lighting.

[Effects of the Invention] According to such a color determination device of the present invention, even if the distance to the target object to be subjected to color determination varies to some extent under illumination by a general illumination device such as a fluorescent lamp, The color determination can be performed, and the color determination can be performed by a relatively simple and inexpensive device.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention, FIG. 2 is a front view of a sensor, FIG. 3 is a block diagram showing an example of an electric processing circuit including a computer, and FIGS. 4 to 8 relate to the present invention. It is a diagram which shows the result of an experiment. 1 ... Object, 4 ... Sensor, 13 ... Main sensor, 14 ... Sub sensor

Claims (1)

[Claims] 1. A sensor for arranging a color measurement target object at an arbitrary distance and a computer for processing the output of the sensor, wherein the sensor receives light having sensitivity to tristimulus values of X, Y and Z. The three-color separation type main sensor formed by the elements and the sub-sensor formed by the light receiving element having sensitivity to visible light, and the computer calculates the chromaticity value obtained from the tristimulus value detected by the main sensor and the sub-sensor. Sensor output,
And the ratio of the output of the sub-sensor and the red component X is used as the item for color determination, and a function for performing color determination by comparing at least a plurality of items with values stored in advance in the memory of the computer is provided. A color determination device characterized by being provided.