JPS5849809B2 - Iroshikibetsukoudenkenshiyutsusouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color discrimination photoelectric detection device for identifying the color of an object to be detected.

Generally, to determine the color of an object to be detected, it is sufficient to separate the light from the object using an optical frequency separator such as an optical filter, but such optical frequency separators are expensive. be.

Electrical separation can be considered, but since the frequency of light is extremely high, it is not possible to directly convert it into an electrical signal and extract the frequency component corresponding to the color, so various measures are required (for example, (See Japanese Patent Publication No. 52-352 by the present applicant).

By the way, color discrimination photoelectric detection devices are used as detection devices for various automatic control devices in industry.

For example, in automatic packaging equipment for confectionery such as caramel,
A mark for cutting is attached to the wrapping paper, and the mark is detected, the paper is cut, and the wrapping paper is automatically wrapped.

Since there are other patterns drawn on the wrapping paper, this mark is set to a special color and only marks of this color are detected (
(A color discrimination photoelectric detection device is used.

Since the marks are generally small and the wrapping paper is transported at an extremely high speed, it is necessary to have a considerably fast response speed and high sensitivity.

Furthermore, as sensitivity increases, malfunctions may occur due to external noise, so it must also have excellent noise resistance.

An object of the present invention is to provide a color discrimination photoelectric detection device that satisfies the characteristics required in actual use as described above, has a fast response speed, and is resistant to external noise.

Hereinafter, an example in which the present invention is implemented using light emitting means having two different light emission colors will be described in detail with reference to the drawings.

FIG. 1 shows a block diagram of the electric circuit in this embodiment.

In FIG. 1, a light emitting diode IL1 is used as a light emitting means.
2 is used.

The light emitting diode 11 emits red light having a narrow spectrum with a center wavelength of 0.66μ and a half width, and the light emitting diode 12 emits green light with a center wavelength of 0.56μ and a narrow spectrum of half width. It has a luminous color.

The light emitting diode 11.12 is a photodetector as a light receiving means.
It is arranged along the ridge of an inverted cone having an apex of detection point 25 and extending at an angle of 45 degrees with respect to a line perpendicular to the light-receiving surface of diode (or phototransistor) 13.

The projected lights from the light emitting diodes 11 and 12 are collected by an optical system (not shown), and the spots of both projected lights overlap at the detection point 25 of the detected object 24.

The photodiode 13 is preferably one that can receive diffusely reflected light from a range that sufficiently covers the above-mentioned spot and has sufficient sensitivity in the visible light region.

The light emitting diodes 11.12 are each illuminated by the output of an oscillator 14.15 having a different oscillation frequency.

The oscillation frequency of the oscillator 14 is f1 The oscillation frequency of the oscillator 15 is f.

If so, it is preferable to select fR>fo.

Generally, light-emitting diodes that are commercially available to date have a higher luminous efficiency than those that emit red light than those that emit green light. This is because transistors have a slow response to light modulated at high frequencies.

Further, taking into account that the photodiode 13 has different sensitivity depending on the wavelength, the output of the light emitters 14 and 15 is selected to have an appropriate magnitude.

The present invention converts the output of the photodiode 13 into the AC amplifier 1.
6 and is amplified by an amplifier 16 and then separated by filters 17 and 18 as described later, the oscillation frequency fR is the oscillation frequency f.

It is necessary not to make it an integral multiple of .

For example, when fR-3KHz and f-IIIGlZ are selected, the oscillation frequency f.

The third high frequency is 3 KHz, making it difficult to separate the signals using a filter.

It is preferable that the AC amplifier 16 has a selection function such as cutting off a low frequency band, and in this case, noise resistance is enhanced.

Filters 17 and 18 are bandpass filters that pass only narrow bands of frequencies centered around the oscillation frequencies fR and fo, respectively.

The filter 17 extracts only the electrical signal from the light projected from the light emitting diode 11, and the filter 18
Since only the electric signal caused by the projected light from the light emitting diode 12 is extracted, the output of the AC amplifier 16 is a signal of frequency fR and a signal of frequency f.

The signal is separated into Since the filters 17 and 18 block noise caused by ambient light, a color discrimination photoelectric detection device that is not affected by ambient light is realized.

The signals separated by filters 17 and 18 are respectively detected by detection circuits 19 and 20 in the next stage and converted into DC signals.

The level discrimination circuits 21, 22 produce an output when their respective inputs exceed predetermined set levels, and the set levels can be changed by level adjustment means 27, 28, respectively.

Next, the output of the level discriminator 2L22 is subjected to a predetermined logical operation by the logic operation circuit 23 and processed.

The logic operation circuit 23 may be configured, for example, by a matrix circuit, or may be configured by a combination of an AND circuit, a NOT circuit, an OR circuit, or the like.

Based on the above configuration, the operation of the circuit shown in FIG. 1 will now be described with reference to the waveform diagram shown in FIG. 2.

Figure 2 C, D, A1, B1, A2, A3, B2. B3
are the output C1 of the photodiode 13, the output D1 of the AC amplifier 16, the output A1 of the filter 17, and the output B of the filter 18.
1. Output A2 of the detection circuit 19, Output A3 of the level discrimination circuit 21, Output B2 of the detection circuit 20, Level discrimination circuit 22
(A3/B3) represents the logical product of A3 and the negation of B3, and (A3, B3) represents the logical product of the negative of A3 and B3.

The operation of the circuit shown in FIG. 1 when a detected object 24 having red and green marks on a white object passes in the direction of the arrow is as follows.

When the detection point 25 falls on a white part of the object to be detected 24, the red and green projection light from the light emitting diode 11 and the green projection light from the light emitting diode 12 are both scattered and reflected by the white background. The light of the photo
The light is received by the diode 13 and an output C is generated.

The output C of this photodiode 13 is connected to the AC amplifier 16.
The signal is amplified by D to become an output D, which is then separated by filters 17 and 18.

The output A1 of the filter 17 is a signal based on the red projection light from the light emitting diode 11, and the output B1 of the filter 18 is
is a signal generated by green projection light from the light emitting diode 12.

These outputs A1, B1 are then respectively detected by detection circuits 19.20, and when the outputs of these detection circuits 19.20 exceed a predetermined set level, level discrimination circuits 21.
22 outputs outputs A3 and B3, respectively.

If the logical operation circuit 23 performs a logical product (A3·B3) of the output A3 and the output B3, a white detection signal is obtained.

In this embodiment, since red and green marks on a white object are detected, the logical product (A3.B3) is not calculated.

Next, if there is a red mark at the detection point 25, only the projected light from the light emitting diode 11 will be transmitted to the photo diode 13.
Since the light is received by the level discrimination circuit 21, only the output A3 from the level discrimination circuit 21 is generated.

Therefore, when the logic operation circuit 23 calculates the logical product (A3, B3) of the negation of A3 and B3, a red mark detection signal is output.

When there is a green mark at the detection point 25, only the light projected from the light emitting diode 12 is received by the photo diode 13, and only the output B3 of the level discrimination circuit 22 is generated.

Therefore, the logical product of the negation of A3 and B3 (A3・B
By performing the calculation in 3), a green mark detection signal can be obtained.

In addition to the above logical operation, a colored mark on a white object can be detected by performing a logical AND operation (A3·B3) between output A3 and output B3.

Also, the logical product (A
Various combinations are possible, such as a black detection signal is obtained by calculating the output A3 and output B3, and a detection signal for a colored mark on a black object is obtained by calculating the logical sum (A3+B3) of the output A3 and the output B3. sell.

Furthermore, if a light emitting means emitting blue light is provided and the same operation as in the above embodiment is performed, the color discrimination ability will be further improved.

FIG. 3 shows a partially cutaway plan view of the color discrimination photoelectric detection device in the above embodiment.

31 and 32 are light emitting diodes that emit red and green light, respectively, and 33 is a photo diode as a light receiving element.

As mentioned above, the light emitting diodes 31, 32 are placed along the ridge of an inverted cone with a 45 DEG extension.

35 is a printed circuit board in which the electric circuit section 26 shown in FIG. 1 is incorporated.

As described above with respect to one embodiment, according to the present invention, the electrical signals from the light receiving element 13 are separated by the electrical bandpass filters 17 and 18, so that the response speed is determined by the response of the light receiving element 13. The speed can be increased to the limit (light-emitting diodes generally have a faster response speed).

In other words, the bandpass filter is PLL (Phase
If a LockedLoop) circuit or the like is used, extremely high selectivity can be obtained, and the frequencies of the oscillators 14 and 15 can be made fairly close to each other, and these frequencies can also be brought close to the limit of the response speed of the light receiving element 13. It is.

Furthermore, if the degree of amplification of the AC amplifier 16 is increased, the sensitivity will become higher, but even if the sensitivity is high, it will not become weak against noise.

This is because, as described above, the bandpass filters 17 and 18 have a narrow band and a high degree of selectivity, so that all noise at frequencies other than this certain frequency can be blocked.

Note that in the above embodiment, the red and green light emitting diodes 11
．． 12, but it is also possible to use light emitting elements that emit light of three or more different colors, such as by adding a blue light emitting diode.

[Brief explanation of the drawing]

FIG. 1 shows a block line diagram showing an embodiment of the present invention.
FIG. 2 is an operational waveform diagram of the above embodiment, and FIG. 3 is a partially cutaway plan view of the above embodiment. 11, 12, 31. 32... Light emitting diode,
13.33...Photodiode, 14.1
5...Oscillator, 16...AC amplifier,
17.18...Filter, 19,20...Detection circuit, 21.22...Level discrimination circuit, 23
...Logic operation circuit, 24, 34 ... Detected object, 25 ... Detection point, 26 ... Electric circuit section, 27. 28...Level adjustment means, 35...Printed circuit board.

Claims (1)

[Claims] 1. A plurality of oscillators that oscillate at different frequencies, and a plurality of oscillators that each have a different unique emission wavelength, are lit with currents of different frequencies based on the respective oscillation outputs, and project light onto an object to be detected. A light-emitting element, a light-receiving element that receives diffusely reflected light from the object to be detected and converts it into an electrical signal, and an electrical signal of the light-receiving element is guided in correspondence with the oscillation frequency of each of the plurality of oscillators. A color discrimination photoelectric detection device comprising a plurality of electrical bandpass filters and a logic circuit that performs a logical operation on the output of each of the bandpass filters.