JPH067069B2 - Color determination device with gloss - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] Generally, gloss refers to the amount of specular reflection of light incident on an object surface and the sharpness of a specular reflection image. The present invention relates to a color determination device that considers only the magnitude of regular reflection amount.

[Prior Art] Generally, a glossy object causes total internal reflection. FIG. 8A shows such a form, which is usually called specular reflection, and the incident light beam φ ₁ exhibits reflection so as to form an image.

On the other hand, when the object loses its luster, diffuse reflection occurs as shown in FIG. 8B, and the reflected light flux φ _S, that is, the light amount on the light receiving surface on the light receiving side, decreases. In the case of this diffuse reflection, the image is not formed in the direction of the reflection center line AP at the angle θ ₁ ′ (= θ ₁ ) from the normal line NP. Further, in various target objects such as metal, the spectral reflectance changes depending on the wavelength of the incident light source.

Therefore, the incident light flux φ _I and the reflected light flux φ _S in the case of FIG. 8 are actually the values φ _Iλ , φ which change depending on the wavelength.
_The specular reflectance ρ _S, which is represented by _{Sλ and} is a general evaluation method of glossiness, is exactly as shown in the following equation.

Furthermore, in equation (1), since the actual light receiving element has spectral sensitivity, substituting that term yields Is established. Here, S (λ) is the spectral sensitivity of the light receiving element. λ ₁ and λ ₂ indicate the wavelength range of the light receiving element.

Explaining the definition of glossiness measurement, the glossiness measurement methods include specular glossiness Gs and contrast glossiness Gc,
The specular gloss Gs considered here is obtained by the following equation, where ρ _OS is the specular reflectance from the glass surface (completely reflecting surface) having a refractive index of 1.567.

Furthermore, when Gs (θ) is calculated in relation to equation (2), Becomes In the formula (4), φ _{OS λ} has a refractive index of 1.567.
Of the light flux reflected from the glass surface, θ indicates an incident angle and a reflection angle.

When the color of such a glossy surface is detected, the amount of light entering the light receiving element changes due to the influence of the gloss, and therefore accurate color determination cannot be performed.

For example, the degree of baking in the baking process of bread in a bakery is generally judged by the color, but when observing this color, there is gloss caused by applying oil or the like to the bread and baking, and the accurate color is I can't judge. To deal with this, a method of observing the color through frosted glass can be considered, but this method cannot determine the degree of fine burning.

Further, there is a similar problem in the test of glossy paint.

[Problems to be Solved by the Invention] In the present invention, the gloss of a target object is measured, and the light amount on the light receiving surface of the light receiving element due to the effect of the gloss is detected, and the object color can be determined from this detected amount. The present invention intends to provide a simple color determination device as described above.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the color determination device of the present invention measures a wave of light emitted from a light source unit arranged on an object to be measured and a slit from the light source unit. The light source that irradiates the object and the light receiver that receives the reflected light from the measured object are optically isolated, and at the same time, covered by a cover that does not allow disturbance light to enter the measurement point of the measured object. In the irradiation unit, the light from the light source unit is made parallel light through the slit and the lens and then can be projected onto the object to be measured, and in the light receiving unit, a sensor that receives light in the specular reflection direction of the parallel light is provided. A color sensor and a visible light sensor are arranged side by side in the above sensor, and a computing device for computing the color wavelength of the object to be measured based on its output is connected to these sensors. To be done.

[Operation] When light is emitted from the light source onto the object to be measured, and the reflected light is received by the visible light sensor and the color sensor, calibration is performed in advance to calculate based on each sensor output. It is possible to determine the color of the object to be measured by calculation in the device. In this case, since the ambient light is prevented from entering the measurement point on the object to be measured by the cover, color determination can be performed by a simple and inexpensive device without using a particularly bright light source.

[Embodiment] FIG. 1 shows an embodiment of the color determination apparatus of the present invention. In this color determination device, the light source unit 2,
An irradiating section 3 and a light receiving section 4 are provided, installed so that the light between these sections respectively projects at a certain angle, and a cover 5 is provided to prevent disturbance light from entering the measurement point of the measured object 1. It is provided.

The above parts 2, 3, 4 are optically isolated by a slit 7 and a shelter 8, respectively. The position of the slit 7 is set so as to come to the focal point of the lens 9 provided in the irradiation unit 3, and the slit itself has a vertically long slit shape.
Further, the lens 9 has a role of making a light ray incident on the object 1 into a parallel light ray, and is further provided with a polarization preventing filter 10 for preventing polarization. On the other hand, in the light receiving section 4, a sensor 12 is provided and connected to an external arithmetic unit 13.

The accuracy of the sensor 12 can be improved by designing the lens diameter as small as possible according to the size of the sensor 12. Although not necessary, the anti-polarization filter 10 has a function of linearly irradiating the irradiation surface of the object with light energy. Furthermore, a cushion is provided between the cover 5 and the object 1.
14 is provided to prevent damage to the object and at the same time, measures are taken to block external light.

When the object 1 is irradiated with the light from the light source 15 in this state, the object 1 is irradiated with the light in a vertically elongated shape in proportion to the slit shape. If the shelter 8 is installed perpendicularly to the object surface between the irradiation unit 3 and the light receiving unit 4, when the object is a perfect reflection surface, its optical path is θ ₁ = θ ₁ ′.
And the radiant energy is concentrated in the direction of θ ₁ ′.

Next, the configuration of the sensor 12 will be described.

The sensor 12 shown in FIG. 2A has three light receiving sensors 2 on a straight line.
It is configured by arranging 1,22,23. Of these three sensors, the sensor 21 at the center is a color sensor, and the sensors 22 and 23 at both ends are visible light sensors sensitive to visible light.

If the color sensor 21 is an R, B, G separation type color sensor, rather than arranging on a straight line in this way, as shown in FIG. It is better to arrange the green color sensors 25, 26, 27. Naturally, the slit shape shown in FIG. 1 also changes accordingly.

The major difference between the sensors shown in FIGS. 2A and 2B is the difference between one or two visible light sensors. Both measure the light quantity, but in FIG. 2A, the average value of a pair of visible light sensor outputs is taken as the light quantity. If rough measurement is sufficient, naturally one visible light sensor in FIG. 2A can be measured as shown in FIG. 2B. In the following, only the case of using the sensor of FIG. 2A will be described.

At the time of measurement, in order to calibrate the sensor, glass having a refractive index of 1.567 is used as the object. In general, it is difficult to keep such a glass in stock because of problems such as maintenance. Therefore, it is preferable to substitute a white surface having a known spectral reflectance. Hereinafter, it is referred to as a drift white surface. When the device shown in FIG. 1 shows a standard white surface, the outputs of the visible light sensors 22 and 23 among the outputs of the sensor 12 are Energy related to is output. Assuming that the spectral characteristic of this visible light sensor has an ideal characteristic of exhibiting a rectangular shape as shown in FIG. 3, it can be considered that the outputs of the two visible light sensors are almost the amount of light on the color sensor. it can. Further, the color sensor 21 determines the reference voltage value so that it becomes white. In the case of FIG. 2B, adjustment is performed so that all the R, B, and G color sensor outputs are equalized. After performing these calibrations, the measurement described below is started.

FIG. 4 shows the average value output of the two visible light sensors 22 and 23 for the standard white surface (solid line) and an arbitrary measured object (broken line). The more glossy the measured object is, the closer the height B of the broken line is to A. Conversely, when the gloss is lost, diffuse reflection occurs on the object irradiation surface, the amount of light on the light receiving surface decreases, and the height B of the broken line becomes smaller. This ratio is almost the same as in Eq. (4). That is, Therefore, the output value of the visible light sensor is used to perform the operation of the equation (6) in the operation device 13 of FIG. 1, and the rough glossiness of the object to be measured can be obtained from the result.

Next, a method of discriminating colors using the ratio in the above formula (6) will be described.

When distinguishing colors, the output of the color sensor 21 is known in advance by a spectral characteristic measuring device for monochromatic light (fifth aspect).
Figure), and the output of the sensor will be corrected from that value. At the same time, the spectral characteristics of the visible light sensors 22 and 23 can be calculated by the apparatus for measuring the spectral characteristics of monochromatic light, and the values are also stored in the arithmetic unit 13.

In FIG. 6, the solid line shows the spectral characteristic (height α (λ)) of the spectral characteristic measuring device for monochromatic light, and the broken line shows the measured value when an arbitrary measured object is shown. The output of the color sensor 21 when an arbitrary object is shown is x, and the output x is a value calculated from the sensor output of FIG. 6 in the same manner as (6). When the value obtained by multiplying the reciprocal of is the value Xn, the wavelength λn corresponding to Xn at that time in the graph of FIG.

This color wavelength λn is calculated based on the output of the sensor 12
It is obtained by the calculation in 13.

Next, the case of the three-color separation type color sensor shown in FIG. 2B will be described. In this case, it is not necessary to calibrate with the monochromatic light spectral characteristic measuring device.

The output ratio when the standard white surface is shown is red, blue,
Assuming R, B, and G for the green sensor respectively, This is because the R, B, G outputs can be converted into xy chromaticity coordinates by obtaining When calculating equation (6), the above values are equal due to the standard white surface (0.3)
The calibration can be completed by adjusting the output of the sensor.

After the calibration is completed, the output characteristics of each color sensor when an arbitrary object is shown are as shown by broken lines R, B, and G in FIG.
Multiplying this output by the reciprocal of Gs (λ) obtained by the method (6), the values become R ', B', G ', and by substituting the values into the following formula, the true x, y chromaticity is obtained. The coordinates are calculated.

The above-mentioned device is not for measuring the luminous flux accurately, but was developed for the purpose of simply measuring the color of an object that has dimness.

[Effects of the Invention] According to the color determination apparatus of the present invention described in detail above, a simple apparatus can easily perform color determination of a glossy object, which is impossible with the conventional method.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a color determination device of the present invention, FIGS. 2A and 2B are front views of a sensor used in the color determination device,
3 to 7 are diagrams for explaining the operation of the arithmetic unit according to the present invention, and FIGS. 8A and 8B are explanatory diagrams for general light reflection. 1 ... Object to be measured, 2 ... Light source part, 3 ... Irradiation part, 4 ... Light receiving part, 5 ... Cover, 7 ... Slit, 12 ... Sensor, 13 ... Computing device, 15 ... Light source , 21, 25-27 ・ ・ Color sensor, 22,23,24 ・ ・ Visible light sensor.

Claims (1)

[Claims] 1. A light source section arranged on an object to be measured, an irradiation section for irradiating the object to be measured with light projected from the light source section through a slit, and a light receiving section for receiving reflected light from the object to be measured. At the same time as being optically isolated, the measurement point of the object to be measured is covered with a cover that does not allow disturbance light to enter, and in the light source section and the irradiation section, the light from the light source section is converted into parallel light through a slit and a lens, and then the While making it possible to project on the measurement object, in the light receiving unit, a sensor that receives it in the specular reflection direction of the parallel light is arranged, and in the sensor, a color sensor and a visible light sensor are provided in parallel, A device for determining a color with gloss, characterized in that a computing device for computing the color wavelength of an object to be measured based on its output is connected to these sensors.