JPH061215B2 - Optical system for projecting color sensor - Google Patents

Description

Detailed Description of the Invention 【Technical field】

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light projecting optical system of a color sensor for performing product classification by color, work instruction, color management, etc. in a factory production line.

BACKGROUND ART As a color sensor, a product shown in FIG. 4 has hitherto been available as a product. The three types shown in (a), (b), and (c) of the figure have basically the same optical system, and include a xenon light-emitting lamp L and
A reflecting surface 10 surrounding this, a diffusion plate 11 arranged in an opening of a space surrounded by the reflecting surface 10, and a xenon light-emitting lamp L.
A light-shielding plate 12 that blocks direct light from the diffuser 11 to
A light receiving optical fiber 8 that receives the light reflected by the surface of the DUT 1 that has passed through the diffuser plate 11 and sends it to the light receiving element, and a reference light that receives the light from the diffuser plate 11 and sends it to other light receiving elements. It is composed of an optical fiber 9. Here, the reference light is received by monitoring the light emission amount in the xenon light emitting lamp L and correcting the light receiving element output that receives the light from the object to be measured with the reference light element output. This is to stabilize the color measurement, in other words, to stabilize the light emission amount of the xenon light emitting lamp L. However, this color sensor has the following problems. That is, in the optical system of the color sensor, the light emitted to the DUT 1 through the diffusion plate 11 and the reference light entering the optical fiber 9 are not exactly the same. In order to stabilize the light emission amount of the lamp L, it is necessary to further increase the capacity of the discharge capacitor to reduce the variation in the light emission amount. However, if the capacity of the discharge capacitor is increased, the number of times of light emission becomes less than once per second, which is not suitable for color detection of the measured object flowing through the production line. Of course, if the capacity of the discharge capacitor is reduced, light can be emitted several tens of times per second, but at this time, the variation in the amount of light emission becomes large and the discharge path in the xenon light-emitting lamp L emits light every time. Since the light distribution pattern fluctuates due to the change to, the light irradiated to the DUT 1 and the light entering the optical fiber 9 for reference light change at different rates, and the correction by the reference light is sufficient. Can't go to. By increasing the capacity of the power supply circuit, it is possible to increase the number of times of light emission per second while keeping the capacity of the discharge capacitor large, but this leads to increase in size and cost.

[Object of the Invention]

The present invention has been made in view of the above points, and an object thereof is to increase the number of times of light emission per unit time of a xenon light emitting lamp by reducing the capacity of a discharge capacitor.
Another object of the present invention is to provide an optical system for projecting a color sensor that can sufficiently stabilize color measurement by correction with reference light.

DISCLOSURE OF THE INVENTION

The present invention, therefore, provides a xenon light-emitting lamp, a spherical reflecting mirror that places the xenon light-emitting lamp at the center of curvature, a collimator lens that makes the light from the xenon light-emitting lamp into parallel light rays, and a semitransparent light that divides the parallel light rays into two directions. For the reference light that guides one of the light separated by the mirror and the semitransparent mirror to the DUT, and the other of the light separated by the semitransparent mirror to the reference light receiving element It is characterized by being composed of a lens, so that the same light as the light directed to the object to be measured can be extracted as the reference light. The present invention will be described in detail below with reference to the illustrated embodiments.
The figure shows an embodiment of the present invention. A spherical reflecting mirror 2 for placing the xenon light emitting lamp L at the center of curvature is installed behind the xenon light emitting lamp L, and in front of the xenon light emitting lamp L. A collimator lens 3 that emits direct light from the xenon light-emitting lamp L or light reflected by the spherical reflecting mirror 2 as parallel rays is installed. Spherical reflector 2
In order to form an inverted image of the xenon light emitting lamp L at the same position as the xenon light emitting lamp L.
Even if the discharge path at is different for each light emission, the inverted image formed by the spherical reflecting mirror 2 contributes to the stabilization of the light distribution pattern. A semitransparent mirror 4 is installed in front of the collimator lens 3, and in front of the semitransparent mirror 4, a lens 50 that temporarily focuses the light that has passed through the semitransparent mirror 4 and a parallel light beam are formed again. A light projecting lens 5 including a lens 51 that sends the light to the surface of the DUT 1 is installed. Since the diaphragm 52 is installed in front of the lens 50, the light projected onto the surface of the DUT 1 by the light projecting lens 5 is a projection of the image of the diaphragm 52. A lens 6 is installed on the side of the semitransparent mirror 4 to collect reflected light from the semitransparent mirror 4 and send it to the reference light receiving element Sr composed of a photodiode via an optical fiber 7. In addition, the light condensed by the lens 6 receives the light receiving element Sr.
However, since the xenon light-emitting lamp L requires a high voltage for its light emission,
At the point of the shield or the point of shielding the light from the xenon light emitting lamp L, the light receiving element Sr is formed by using the optical fiber 7.
Is preferred. Also, as the semi-transparent mirror 4,
It is not necessary to use one that divides the transmitted light and the reflected light into equal parts, and the reflected light used as the reference light may be less than the transmitted light that illuminates the DUT 1. With the projection optical system configured as described above, a light-receiving lens 20 and a light-receiving element including a photodiode array with a color separation filter are provided directly above the DUT 1 to which light is obliquely irradiated. 21 and 21 are installed. In order to see the performance of the light projecting optical system, as shown in FIG. 2, a light receiving lens 20 and one end of an optical fiber 27 for guiding light to a light receiving element 22 formed of a photodiode are provided on the optical axis of the light projecting lens 5. Installed, the current of the light receiving element Sr for reference light −
Output V ₁ through the voltage conversion integration amplifier 25 and output V ₃ through the current-voltage conversion integration amplifier 26 of the light receiving element 22
When compared with, the variation in the value of V ₃ / V ₁ is ±
It was 1-2%. Further, the illuminance distribution on the DUT 1 was also substantially uniform, with a deviation of 1 to 2% within the colorimetric area (maximum diameter 10 mm) at the stop 52. 3 (a), (b) and (c) show the light receiving element 2 with the color separation filter.
2 shows the color fabric algorithm for determining from the output of 1 whether or not the object to be measured has the desired color. When the output currents for red, green, and blue in the light receiving element 21 formed of a photodiode array are I _R , I _G , and I _B , these are passed through a current-voltage conversion integrating amplifier and voltage values V _R ', V _G ', _{V B'} to convert. Further, when the voltage conversion output of the reference light-receiving element Sr and Vref, as the color parameter, obtains the _{V R = V R '/ Vref} V G = V G' / Vref V B = V B '/ Vref. When a photodiode array with a color separation filter is used as the reference light receiving element Sr, the voltage conversion output for each color of the light receiving element Sr is V
_R ref, _{V G} ref, When _{V B} ref, as the color parameter, obtains the _{V R = V R '/ VV} R ref V G = V G' / VV G ref V B = V B '/ VV B ref. For this color parameter, FIG. 3 (a) obtains a second parameter of _{r = V R / S g =} V G / S ( although _{S = V R + V G +} V B), 2 -dimensional r and g It is shown that whether or not the color is the desired color is determined by whether or not the values of both r and g parameters obtained from the measurement result are included in the preset ranges A, B, and C in the area. In the same figure (b), in the three-dimensional space of V _R , V _G , and V _B , the vector Vt based on the above-mentioned parameters obtained from the measurement result and the desired color having the allowable value in the range of the direction angle α are shown. It is shown that determination as to whether or not to obtain is performed based on the difference θ in the direction angle with the vector Vo. Further than that shown in FIG. 3 _{(c), V R, V} G, 3 of _{V B}
In the dimensional space, the three-dimensional distance is obtained by the above parameters obtained from the measurement result, and whether or not the color is the desired color is determined depending on whether the distance is within a predetermined range.

【The invention's effect】

As described above, in the present invention, a part of the light sent from the xenon light-emitting lamp to the object to be measured through the collimator lens is taken out as a reference light by the semitransparent mirror, and the irradiation light of the object to be measured is used. Since the same light can be extracted as the reference light, the ratio of the irradiation light of the DUT to the reference light is stable even if the capacity of the discharge capacitor for the xenon light-emitting lamp is reduced and the number of times of light emission per second is increased. In addition, it is possible to perform accurate color measurement.

[Brief description of drawings]

FIG. 1 is a front view of an embodiment of the present invention, FIG. 2 is a front view showing the same test condition, and FIGS. 3 (a), (b) and (c) are characteristic diagrams showing color detection algorithms, respectively. 4 (a), (b) and (c) are sectional views of a conventional example, in which 1 is an object to be measured, 2 is a spherical reflecting mirror, 3 is a collimator lens, 4 is a semitransparent mirror, 5
Is a projecting lens, 6 is a lens, L is a xenon lamp,
Sr represents a light receiving element for reference light.

Claims (1)

[Claims] 1. A xenon light-emitting lamp, a spherical reflecting mirror that places the xenon light-emitting lamp at the center of curvature, a collimator lens that makes light from the xenon light-emitting lamp into parallel rays, and a semitransparent mirror that divides the parallel rays into two directions. And a light projecting lens for irradiating the DUT with one of the light beams split by the semitransparent mirror, and a reference light lens for guiding the other of the light beams split by the semitransparent mirror to the reference light receiving element. An optical system for projecting a color sensor, comprising: