JPH0650929Y2 - Photoelectric sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a photoelectric sensor, and more particularly to a photoelectric sensor that detects a mark attached to a conveyed sheet or the like.

(B) Conventional Technology Generally, a reflective photoelectric sensor or a transmissive photoelectric sensor is used to detect a mark carried by a roller in an automatic packaging machine or the like. A conventional reflection type photoelectric sensor irradiates a sheet to be detected with light emitted from a light projecting portion through an optical system including a half mirror and a lens, and the light reflected by the sheet or the mark is received by the light receiving portion through the optical system. Receive and detect the mark. In addition, in the transmissive photoelectric sensor, a light projecting unit and a light receiving unit are separately provided on the upper side and the lower side of the U-shaped case body, the conveyed sheet is sandwiched, and the light from the projecting section is transmitted through the sheet. The mark is detected depending on whether or not the light is received by the light receiving section.

(C) Problems to be solved by the invention In general, a single automatic packaging machine uses many kinds of packaging films. Therefore, for example, when a reflective photoelectric sensor is attached to an automatic packaging machine, when detecting a mark printed on an opaque film, the reflected light is obtained together with the film background, and the mark can be detected by the amount of light, The print marks on the transparent film cannot be detected stably. Rather, in this case, it is desirable to use a transmissive photoelectric sensor. Therefore, regardless of the type of film, in order to perform stable mark detection, the photoelectric switch is replaced and used according to the type of film, but this is not efficient because it takes a lot of time to replace it. There is a problem in that the price of the automatic packaging machine is increased because it is necessary to purchase two types of photoelectric sensors.

In view of the above, the present invention is a photoelectric sensor,
It is an object of the present invention to provide a photoelectric sensor capable of detecting marks printed on all kinds of films regardless of whether they are opaque or not requiring special manual switching depending on the type.

(D) Means for solving the problem The photoelectric sensor of the present invention is arranged across the detection area,
The first light projecting section and the second light projecting section that project light to the detection area, and the light projected by the first light projecting section are reflected by the detected object existing in the detection area. And a detection signal based on a light reception signal generated by the light reception unit, which receives the reflected light and receives the transmitted light that has passed through the object to be detected among the light projected by the second light projection unit. And a means for driving the first light projecting unit and the second light projecting unit in a time division manner.

(E) Action In this photoelectric sensor, the first light projecting portion and the second light projecting portion respectively emit light in a time division manner. The light from the first light projecting unit is applied to the sheet and the mark passing through the detection area, and when the sheet and the mark are not transparent, the light is reflected on the surface of the sheet and is received by the light receiving unit. on the other hand,
The light emitted from the second light projecting portion is also irradiated from the back surface of the sheet with a time difference from the light emitted from the first light projecting portion. In this case, when the sheet is transparent, the sheet is The light is transmitted and is also received by the light receiving unit. Therefore, when the sheet is opaque, the light-receiving unit changes the time and the first
When the sheet is transparent, the mark is detected by the light reflected by the mark from the light projecting portion of the second mark, and the mark is detected by the light receiving portion output of the light transmitted through the sheet from the second light projecting portion.

Therefore, according to the output signal derived from the light receiving section by the light of either the first light projecting section or the second light projecting section,
When the mark detection output is obtained, it becomes an output with a mark.

(F) Example Hereinafter, the invention will be described in more detail with reference to an example.

FIG. 1 is a side view of an optical system of a photoelectric sensor showing an embodiment of the present invention.

The case body 1 is formed in a U shape and sandwiches the space 2 between
The upper case part (first storage part) 3 and the lower case part (second storage part)
Storage part 4). The upper case portion 3 includes a light emitting diode (first light projecting portion) 5, a half mirror 7 and a lens 8 having an angle of 45 ° with respect to the optical axis from the light emitting diode 5.
And a composite photodiode (light receiving portion) 9 is provided,
The lower case portion 4 has a light emitting diode (second light emitting portion).
6 is provided. The composite photodiode 9
Is composed of two photodiodes 9a and 9b, and both photodiodes 9a and 9b have the same light receiving area.

When the mark of the sheet is detected by using this photoelectric sensor, the sheet 10 is arranged so as to pass through the space 2 from the back side of the drawing in the front (or vice versa) direction. In this case, the passage position of the sheet 10 is set so that the mark 11 passes on the optical axis of the light emitting diode 5, the lens 8 and the light emitting diode 6. Then, the sheet 10 in which the light from the light emitting diode 5 passes through the space 2 through the half mirror 7 and the lens 8.
Alternatively, the mark 11 is irradiated and the reflected light is reflected by the lens 8,
The light is received by the composite photodiode 9 via the half mirror 7. When the sheet 10 is transparent, the light emitted from the light emitting diode 6 is transmitted through the sheet 10, passes through the lens 7 and the half mirror 8, and is also incident on the composite photodiode 9.

FIG. 2 is a block diagram showing the circuit configuration of the photoelectric sensor of the embodiment.

The pulse signal oscillated by the oscillating circuit 29 is frequency-divided by the frequency dividing circuit 30, and the light-emitting diode 5 and the light-emitting diode 6 are alternately driven in a time-division manner by the divided alternate output. The frequency-divided outputs of these frequency-dividing circuits 30 are input to the gate circuit 25 by closing the OR circuit 31.

The light emitted from the light emitting diode 5 or the light emitting diode 6 is received by the light receiving regions 9a and 9b of the composite photodiode 9, and the signal is amplified to some extent by the amplifiers 21 and 22 and then amplified by the differential amplifier 23. , Is input to the window comparator 24. Window comparator 24
Has two threshold values of Vth ₁ and Vth ₂ centered on 0V, and outputs a signal when the output of the differential amplifier 23 exceeds the threshold value Vth ₁ or falls below the threshold value Vth _2. . The output signal of the window comparator 24 is integrated by the integration circuit 26 via the gate circuit 25, and is output as two pulse signals from the output circuit 28 via the waveform shaping circuit 27. The mark is output by two pulse signals.

Next, the operation of the photoelectric sensor of the above embodiment will be described by taking the case of using three typical types of films as an example. There are three types of films used: an opaque film with a mark having a low reflectance, a transparent film with a mark with a low reflectance, and a transparent film with a mark with a high reflectance.

First, when a sheet having a mark with low reflectance on an opaque film is passed through the space 2, as shown in FIG. 3 (a), the timing at which the light emitting diode 5 is turned on (shown by a solid line) and the light emitting diode are indicated. Both of them emit light at the timing of lighting 6 (shown by a broken line). The light from the light emitting diode 5 is a half mirror 7 and a lens 8.
The sheet 10 and the marks 11 are radiated through the sheet, and the light from the light emitting diode 6 is radiated from the back surface of the sheet 10. The light emitted from the light emitting diode 5 is reflected by the sheet 10 because the sheet 10 is opaque, and is also reflected by the mark 11, but the reflectance of the mark 11 is low.
A difference occurs in the amount of light received by the composite photodiode 9 via the lens 8 and the half mirror 7, and a pulse signal corresponding to the level difference is output as the output of the differential amplifier 23 at the timing at which the light emitting diode 5 emits light. Further, only a signal exceeding the threshold value is derived by the window comparator 24, and is input to the integrating circuit 26 via the gate circuit 25. The pulse signal is integrated by the integrating circuit 26, waveform-shaped by the waveform shaping circuit 27, and two signals having a predetermined pulse width are output from the output circuit 28. As a result, mark detection is performed.

Next, as shown in FIG. 3B, when the transparent film is provided with a mark having a low reflectance, the light from the light emitting diode 5 is the same as in the case of FIG. 3A. Since it is a transparent film, the light from the light emitting diode 5 is transmitted in this case. On the other hand, the light from the light emitting diode 6 is transmitted through the sheet 10, and the lens 8 and the half mirror 7
Then, the light is received by the composite photodiode 9 via. That is, at the timing when the light emitting diode 6 emits light, a pulse signal corresponding to the amount of received light is output to the differential amplifier 23, a signal of a predetermined level or more is output to the window comparator 24, and the pulse width is the same as the previous time. Two signals are output and mark detection is performed.

Further, when a mark having a high reflectance is attached to the transparent film, the light from the light emitting diode 5 is applied to the mark 11 through the half mirror 7 and the lens 8 and is reflected by the mark 11, so that the lens 8, The light is received by the composite type photodiode 9 through the half mirror 7, while the light emitting diode 6 is turned on at the timing of lighting.
The light from is transmitted through the sheet 10 and is also received by the composite photodiode 9. Therefore, as the output of the differential amplifier 23, as shown in FIG. 3C, pulse signals of + polarity and − polarity are output respectively, and the window comparator 24
A signal that exceeds both thresholds Vth ₁ and Vth ₂ at
It is output via 25, and this is the integrating circuit 26, the waveform shaping circuit.
The signal is output via 27, and the output circuit 28 also outputs two continuous pulse width signals to perform mark detection.

As described above, in the photoelectric sensor of this embodiment, the light emitting diode 5 and the composite photodiode 9 form a reflective photoelectric sensor, and the light emitting diode 6 and the composite photodiode 9 form a transmissive photoelectric sensor. Since both the photoelectric sensor and the transmissive photoelectric sensor are driven in a time division manner, even if the sheet 10 is transparent / opaque and the reflectance of the mark 11 is high / low, the detection output of either one is Since it is obtained, it is not necessary to prepare two photoelectric sensors specially, and one photoelectric sensor can detect.

In the case of using the composite photodiode in the light receiving portion as in the above embodiment, no switching operation or sensitivity adjustment is required due to the difference in the type of sheet or mark.

However, the present invention can be applied not only to the use of the composite photodiode of the light receiving section but also to the use of a single light receiving photodiode.

(G) Effect of the Invention According to the present invention, the first light projecting portion is provided in the first housing portion of the one case body in which the first housing portion and the second housing portion face each other through the space. Since the second portion and the light receiving portion are provided and the second light emitting portion is provided in the second storage portion, any of the reflection type photoelectric sensor or the transmission type photoelectric sensor can be used regardless of the sheet and mark to be detected. Either one of the outputs can be obtained, and the mark can be surely detected.

Therefore, even if the types of sheets and marks to be packaged are changed, it is not necessary to replace the photoelectric sensor each time, which saves the labor and one photoelectric sensor is sufficient, so that the cost of the entire apparatus can be reduced.

Further, in this photoelectric sensor, the light projecting portions are provided in the first housing portion and the second housing portion, respectively, and the light receiving portion is also used. Since it fulfills the function of the sensor, only one light receiving circuit unit is required, and the complicated light receiving circuit unit can be simplified. From this point as well, a photoelectric sensor of lower cost can be obtained.

[Brief description of drawings]

FIG. 1 is a side view of an optical system of a photoelectric sensor of an embodiment of the present invention, FIG. 2 is a circuit connection diagram of the photoelectric sensor of the embodiment, and FIG. 3 is for explaining the operation of the photoelectric sensor of the embodiment. It is a waveform diagram of. 1: Case body, 3: Upper case part, 4: Lower case part, 5: Light emitting diode (for reflective type), 6: Light emitting diode (for transmissive type), 7: Half mirror, 8: Lens, 9: Composite type Photodiode, 29: oscillator circuit, 30: frequency divider circuit.

Claims (1)

[Scope of utility model registration request] 1. A first light projecting section and a second light projecting section, which are arranged so as to sandwich a detection area and project light onto the detection area, and light emitted by the first light projecting section. A light receiving unit that receives the reflected light reflected by the detected object existing in the detection area, and receives the transmitted light that has passed through the detected object among the light projected by the second light projecting unit. And a signal processing unit that outputs a detection signal based on a light reception signal generated by the light receiving unit, and a unit that drives the first light projecting unit and the second light projecting unit in a time division manner. A photoelectric sensor characterized in that