JPS6125281A - Color marksensor - Google Patents

Abstract

PURPOSE:To detect exactly a mark and to make various detection possible by slanting a light receiving optical system light axis against a light projecting optical system light axis, and amplifying the output of a photodetecting element for signal light and the output of photodetecting element for referential light. CONSTITUTION:Angle theta is set between the light axis of a light emitting optical system from lamp l and the light axis of a photodetecting fiber PD2 optical system, and threby, the light normally reflected on the surface of object M doesn't project to the photodetecting optical system, but only diffused light reflected on the surface of an object M is projected and detected. Amplifiers AP1, AP2 and comparators CP1, CP2 form a wind comparator to compare the amplified output voltage with the output voltage of amplifier AP1, and its threshold valve is decided by the output voltage of amplifier AP2, and the width of wind is decided by the adjustment of a variable resistance VR1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a color mark sensor used to automatically detect marks on an object surface.

[Background technology]

A conventional color mark sensor has an optical system as shown in FIG. 4 and a circuit as shown in FIG. 5. In the optical system shown in FIG. 4, the light emitted from the lamp 2 becomes approximately parallel light through the lens L1, and is focused onto the object surface M by the lens L.

The light (signal light) reflected on this object plane M is transmitted through the lens L! Once converted into parallel light, approximately half of the amount of reflected light received by the half mirror HM is reflected toward the lens "J" and L3, and is collected by this lens L onto the second light receiving element PD1. Further, a part of the light from the lamp 2 is received via the aperture A by the second light receiving element PD for reference light. In the circuit shown in FIG. 5, operational amplifiers OPt and O'Pz constitute a signal processing circuit for the outputs of the light receiving elements FD, . . . PD2.

Now, a method for detecting marks on the object plane M will be explained. Therefore, it is assumed that the mark has a lower reflectance than the base of the object surface M. First, illuminate the base of the mark with a light spot,
At that time, the diaphragm A is opened and closed to detect both photodetectors PD, , FD.
, the output currents of the first light receiving element PD1 are set to be approximately the same and the output of the first light receiving element PD1 is slightly larger, and at this time, the output of the circuit of FIG. 5 becomes %H,I. Next, illuminate the mark with the projected light spot, open and close the aperture #)A again, and select both photodetectors PD, ,
Set so that the outputs of PD and PD are almost the same. After this, the aperture A is set at the center of the position determined by both of the setting operations described above. By doing this, the output voltage Vout of the operational amplifier OP1 when the mark is detected is changed to the operational amplifier OP! The comparator threshold value V
This means that it is set to be lower than c. Therefore, when the projected light spot is illuminated on the underlying part of the object surface M, which has a higher reflectance than the mark, the output voltage VOut exceeds the threshold voltage Vc and the detection output becomes %LI.When the mark is detected, %HI- output is generated, and marks can be automatically detected.

However, in the conventional example described above, since the configuration was such that the specularly reflected light from the object surface M was received, marks etc. when the object surface M was a glossy surface had a small difference in the amount of reflected light. In addition to the problem that it is difficult to detect the lamp, when extracting analog output using the circuit shown in Fig. There is a problem in that it is not possible to correct for variations in the amount of light, and there is also a problem in that it is not possible to detect only marks with a certain reflectance.

Figure 6 shows an example of an optical system using conventional optical fibers FA, FA, where at least on the light emitting/receiving surface side, light is received in a donut shape around the light emitting optical fiber FA. Optical fiber FA for use is arranged and lamp! And on the light receiving element FD1 side, both optical fibers FA, , -FA, ,
The light receiving element PD is separated from the light receiving element 2 and faces the light receiving element PD, respectively. However, in such a conventional example, the distance d between the tip of the optical fiber FA, %FA and the sampling surface M is 0.
．． The distance d is extremely short at 5 to 1.5 mm, and if this distance d fluctuates, there is a risk that the tips of the optical fibers FA, FA2 may come into contact with the object plane M, making installation difficult.

[Purpose of the invention]

The first object of the present invention is to provide a color mark sensor that can accurately detect marks without being affected even when the object surface is a glossy surface. A second purpose is to enable selective detection of the marks, and a third purpose is to make setting and installation extremely easy for those using optical fibers.

[Disclosure of the invention]

(Example 1) Figure 1 shows an optical system according to a first example of the present invention. As a result, the light specularly reflected by the object surface M does not enter the light-receiving optical system, and only the diffusely reflected light from the object surface M can be detected by the light-receiving optical system. K is used so that marks can be detected without being affected by the gloss of M. AI in the figure,
A! There are many apertures on the reference beam side and signal beam side, respectively. FIG. 2 shows a circuit according to an embodiment of the present invention, which is different from the conventional circuit shown in FIG. The two comparators cp1 and CP are used to configure the window comparator, and the inside of the window can be set using the variable resistor VR1. By turning off the switch SW1 in the window comparator, In order to operate in the same way, it is possible to extract the zero level signal of both the signal light and the reference light, and it is also possible to separate it into several stages using an external comparator. 1
,lamp! The light intensity fluctuations can be detected by the output of the reference light, so light intensity fluctuations can be easily corrected.

In this embodiment circuit of FIG. 2, an amplifier AP.

AP2 amplifies the outputs of the light receiving elements PD1 and PD2, respectively, and comparators cp, , cp2 and amplifier A
A window comparator is constructed to compare the output voltages of P, and its threshold value is determined by the output voltage of AP2, and during the window, it is determined by adjusting the variable resistor VR. The output voltage of the amplifier AP can be adjusted by adjusting the amount of light incident on the photodetector PD using the aperture A.
ry.

It constitutes a current source of 2 transistors, and is a voltage regulator for an AVR.
These are analog 0 output terminals for 3 to 6 transistors, 5O1RO signals and reference light. Thus, the method of using the embodiment shown in FIGS. 1 and 2 as a sensor is completely the same as that of the conventional example described above.
When W1 is open, the operation is substantially the same as in the conventional example. In addition, when the switch SW is closed, the window comparator functions and becomes a trap so that only marks within a preset arbitrary reflectance range can be detected.

(Embodiment 2) FIG. 3 shows an optical system of a second embodiment of the present invention, in which the same signal amplification/processing circuit as in the embodiment of FIG. 2 is used. In the embodiment shown in FIG. 3, optical fibers FA, FA, FA, and
A self-focusing lens L is arranged at the tip of A 0 and F A 2, so that the optical axis of the projected light reaching the object plane A has an angle of θ. Gold focusing lens L. 1.L
O! Assuming that the refractive index distribution constant of ``B1 is n, the lens length is Z, and the dimensions of each part in the optical system are as shown in the diagram, the relationship between dimension stones 0 and J3 is as follows. , and the relationship between the dimensions !□ and 12 is as follows.-Furthermore, the dimensions r1 and r are !rl = roXm:rOX'.Thus, in the case of this example, the self-focusing lens JL.l, the dimension between the tip surface of LO2 and the object plane M can be made relatively large, which has the effect of making it easier to adjust the installation of the optical system, as well as the above-mentioned This embodiment has the same effects as the first embodiment.

〔Effect of the invention〕

As described above, in the present invention, the optical axis of the light-receiving optical system is tilted with respect to the optical axis of the light-emitting optical system so that only the diffusely reflected light from the object surface is received by the light-receiving optical system. Even if the surface is a glossy surface, it is not affected by this.
It has the effect of accurately detecting marks, and it also amplifies the output of the first light receiving element for receiving the signal light and the output of the second light receiving element for serving as the reference optical system using separate amplifiers. However, since the output of both amplifiers is used to discriminate the signals, it is possible to detect marks in an arbitrary reflectance range, making it possible to detect only marks of a specific color. This has the effect of enabling a variety of detection methods and easily applying it to multicolor discrimination.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the optical system of the first embodiment of the present invention, and FIG.
3 is a schematic diagram of the optical system of the second embodiment of the present invention, FIG. 4 is a schematic diagram of the optical system of the conventional example, and FIG.
This figure is the same circuit diagram as above, and FIG. 6 is a schematic diagram of another conventional optical system, with PD, , PD! are first and second light-receiving elements, AP, and AP are amplifiers, respectively.

Claims (3)

[Claims] (1) The optical axis of the light-receiving optical system is tilted with respect to the optical axis of the light-emitting optical system so that only the diffusely reflected light from the object surface is received by the light-receiving optical system, and the first light-receiving element for receiving signal light is A color mark sensor characterized in that the output and the output of a second light receiving element for receiving reference light are amplified by separate amplifiers, and signal discrimination processing is performed based on the outputs of these amplifiers. (2) When performing signal discrimination processing, the outputs of the two amplifiers are input to a window comparator so that it can be determined whether or not the amount of received and reflected light is within the width of an appropriate threshold level. Claim 1 characterized by
Color mark sensor described in section. (3) The color mark sensor according to claim 1, wherein the light projecting optical system and the light receiving optical system are constituted by an optical fiber and a self-focusing lens at the tip thereof.