JPS6039974B2 - optical inspection - Google Patents

Description

[Detailed Description of the Invention] <<Field of the Invention>> This invention is a method for discriminating the color of an object to be inspected by irradiating the same part of an object with two types of light of different colors and measuring the reflected light or transmitted light. This invention relates to an optical inspection device using two-color light that performs such operations.

《Background of the Invention》 For example, the epidermis of a fruit such as a mandarin orange is irradiated with green light and red light, and the pigment of the epidermis is determined from the ratio of the amount of reflection of both rays, and the ripeness of the fruit can be examined based on this. Optical inspection devices have been proposed to detect abnormally discolored and damaged fruit.

Although such an inspection is not so difficult in principle, many problems arise when implementing the above inspection in, for example, a fruit sorting line where oranges are conveyed on a conveyor.

In particular, in order to perform hue inspection on each part of the object to be inspected in a short time, multiple systems of light source sections, light receiving sections, and signal processing sections are required, so it is extremely important to keep each section simple. This poses a major challenge.

For this reason, in the present invention, first, the object to be inspected is irradiated with light of different colors from two types of light sources, and the reflected light (or transmitted light) is received by a common light receiving element. Compared to the method of separating two types of reflected light (or transmitted light) using a dichroic mirror or the like and receiving each light with a separate light receiving element, the optical configuration of the light receiving section and the signal processing section are simpler. I tried to make it look like this.

However, the method of simply lighting two types of light sources in pulses alternately and distributing the output of the light receiving element in synchronization with the lighting timing is to calculate the ratio of the amount of reflection (or amount of transmission) of the two colors of light. This requires a relatively complex circuit system using sample-hold circuits, division circuits, etc., and the difference in the timing of irradiation of the two colors of light reduces measurement accuracy when the object to be inspected vibrates. There is a drawback that is a major cause of this.

<Objective of the Invention> The object of the invention is to provide an optical inspection device that does not require a sample-hold circuit or a division circuit, and can directly obtain digital data corresponding to the ratio of both reflected or transmitted light beams. There is a particular thing.

<<Structure of the Invention>> This invention irradiates an object to be inspected with a first light beam having a predetermined color, and a second light beam having a color different from the first light beam, which is delayed from the first light beam. An illuminator that irradiates the same area with a light beam for a certain period of time with both optical axes aligned, and then stops irradiating both light beams at the same time; the amount of detection light obtained by reflection or transmission from the object to be inspected; a single photoelectric converter that outputs an electrical signal corresponding to the three photoelectric converters, and outputs a voltage at a first level when the first light beam is irradiated; an amplifier that outputs a second level voltage when the first and second light beams are superimposed; a calibrator for calibrating the output voltage; an integrator for integrating the output of the amplifier circuit after being calibrated by the calibrator;
A time information output device that outputs time information according to a ratio between a voltage difference between level voltages and the first level voltage.

<Description of Embodiments> Hereinafter, an embodiment of the present invention will be described in detail based on the accompanying drawings.

In FIG. 1, IG is a light emitting element that generates green light, I
R is a light emitting element that generates red light, and the light from these light emitting elements IG and IR is made to coincide with each other through a half mirror 2, and irradiates the same part of the object to be inspected 3 under the same conditions. The reflected light from the object to be inspected 3 is received by a single light receiving element 4 and photoelectrically converted, and the output of the light receiving element 4 is amplified by an amplifier 5.

The lighting of the light emitting elements IG and IR is controlled by the timing control circuit 6, and the lighting timing is as shown in G and R in FIG. (t, → ra), then, while the light emitting element IR remains lit, the light emitting element IG is also turned on, emitting red light and green light at the same time (ra → t3), and both the light emitting elements IG, IR The lighting mode of turning off the light and stopping the irradiation of both light beams (ra) is repeated at regular intervals. Therefore, "the above amplifier (that is, the light receiving element 4
), as shown in a of FIG.
Here, the voltage Vr corresponds to the amount of reflection of red light, and the period t
At 2 → et al., the voltage Vr corresponding to the amount of reflection of the green light is added to the voltage Vr by a number of volts, resulting in a voltage Vr + Vg, and after the time point et al., it becomes zero again.

Further, 7 indicates an integrator, which is composed of an operational amplifier 8, a capacitor C and a resistor R that determine an integration constant, and an integration gate 9 consisting of an analog switch that controls the integration operation. The output of the amplifier 5 is supplied to the input terminal via a coupling capacitor 10 for a DC gate.

Further, an analog switch 11 for clamping the input of the integrator 7 to zero is connected between the input terminal of the integrator 7 and the ground, and this analog switch 11 and the integration gate 9 are controlled by the timing control circuit 6 to controlled as follows.

As shown in FIG. 2b, the analog switch 11 is turned ON at t2 during the period when only the red light emitting element IR is lit.
Therefore, during this period, regardless of the output of the amplifier 5, the integrator 7
When the input of the amplifier 5 is forcibly clamped to zero and the analog switch 11 is turned off at a certain point, the change in the output of the amplifier 5 is input to the integrator 7 via the coupling capacitor 10.

Therefore, as shown in c in FIG. 2, the input voltage of the integrator 7 is zero until time t2, and in the period t3, the change after time t, that is, the voltage +Vg, becomes Vg.
-(Vr+Vg)=-Vr. That is, period L→
The output of the amplifier 5 is level-shifted and input to the integrator 7 so that the output voltage Vr of the amplifier 5 becomes a zero input to the integrator 7. In addition, in the figure, the rising point at which the analog switch 11 is turned on is slightly delayed from time t, but this is to clearly show the action of the koto clamp, and is not limited to this. It is sufficient that zero clamping is completed by time t.

As shown in FIG. 2d, the integration gate 9 is turned off for a sufficiently long period of time from time t2 to time t4 after time t3, and the integrator 7 operates only during that period from t2 to t4, and the input signal is Integration is performed, otherwise the integration gate 9 is ON and the integrator 7 is inactive and its output voltage is kept at zero.

Therefore, as shown in e in Figure 2, the output voltage of the integrator 7 is kept at zero until time t2, and since the input voltage Vg is integrated from time t2 to t2, the output voltage is proportional to the output voltage Vg. Since the output voltage decreases in the negative direction at a rate of change, and then the input voltage -Vr is integrated from time point 0 to L, the output voltage increases in the positive direction with a change amount proportional to Vr.

Here, in the integration process at time t, the output voltage of the integrator 7 becomes zero (crosses the zero bell) until 'Vgdt='Vrdt, and from -
If t2=To (constant) and tx-upper3=Tx, then TX
=Fortress T.

Therefore, the time Tx is proportional to the ratio of the voltage Vr and the voltage Vg.

Therefore, in order to determine the above-mentioned time information correction x, the output of the integrator 7 is first introduced into the comparator 12, and as shown at f in FIG. 2, the output of the integrator 7 is negative.

A signal that becomes high level during the period tx is obtained. Then, the output of the comparator 12, a signal obtained by inverting the lighting signal R of the red light emitting element IR by the inverter 3, a control signal d to the integrating gate 9, and an oscillator that generates a relatively high frequency clock pulse. 14 into the AND gate 15, thereby causing the time t
3 to oscillator 1 from AND gate 15 only during the period of
4 clock pulses are output. Furthermore, using the lighting signal R as a reset signal, the AND gate 1 is activated by the counter 16 operating as shown in h in FIG.
The above time Tx can be measured by counting the clock pulses output from the counter 6, and the output of the counter 6 is the ratio of the voltage Vte to the voltage Vg, that is, the amount of red light reflected by the inspected object 3 and the green light It corresponds to the ratio of the amount of reflection. <<Effects of the Invention>> As explained in detail above, the inspection apparatus according to the present invention can perform an inspection in which an object to be inspected is irradiated with light of two different colors and the ratio of the amount of reflection (or amount of transmission) of each is determined. , measurement can be carried out with an extremely simple optical configuration and signal processing using a simple circuit method, and it is also possible to perform high-speed measurement and to achieve high precision with little influence from vibrations of the test object. It has various effects such as being able to perform measurements.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is a timing chart of each main part in FIG. IG, IR...Light emitting element, 3...Object to be inspected, 4...
Light receiving element, 5... Sensitizer, 6... Timing control circuit, 7... Integrator, IQ... Coupling capacitor, il... Analog switch, 12...・・・
... Comparator, 14 ... Oscillator, 16 ... Counter. Figure 1 Figure 2

Claims (1)

[Claims] 1 A first light beam having a predetermined color is irradiated onto the object to be inspected, and a second light beam having a color different from the first light beam is irradiated for a certain period of time, delayed from the first light beam, and An illuminator that aligns both optical axes, irradiates the same area overlappingly, and then stops irradiating both beams at the same time; Outputs an electrical signal corresponding to the amount of detection light obtained by reflection or transmission from the object to be inspected; a single photoelectric converter; connected to an output terminal of the photoelectric converter, outputting a voltage at a first level when the first light beam is irradiated; an amplifier for outputting a second level of voltage when the first voltage from the amplifier is superimposed;
a calibrator that calibrates the output voltage of the amplifier so that the level voltage becomes a zero level voltage; an integrator that integrates the output of the amplifier circuit after being calibrated with the calibrator; and an output voltage of the integrator. and a time information output device that outputs time information according to the ratio of the voltage difference between the first and second level voltages and the first level voltage based on the above. Inspection equipment.