JPH055651A - Photoelectric switch - Google Patents

Abstract

(57) [Abstract] [Purpose] Photoelectric switch that can also be used for the detection of articles that use photosensitizers, such as photographic film manufacturing processes. A diode is used, and a photodiode that is sensitive to infrared rays with a wavelength of 1000 nm or more is used for the light receiving part.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a photoelectric switch.

[0002]

2. Description of the Related Art In each process of manufacturing a photographic film, it is necessary to surely detect whether or not a film coated with a photosensitizer exists (is passing) in a certain place. Since contact type detectors such as microswitches have flaws in the product, non-contact type detectors such as photoelectric switches are desired, but conventional photoelectric switches detect near-infrared rays in the visible light range ~ 900 nm as detection light. Since the light in the range is used, it cannot be used in the manufacturing process of a photographic film or the like which handles a photosensitizer which is sensitive to the same wavelength range as the light. Therefore, conventionally, a method of sticking a light-shielding tape to the film and irradiating it with detection light, or irradiating the film with detection light without providing a light-shielding means and then cutting off the exposed portion at the end of the manufacturing process has been adopted. Was there.

[0003]

The method of attaching the light-shielding tape to the film not only requires an extra step in the film production line, but also reduces the production efficiency. This is also the case with the method of cutting off the exposed areas, and is a waste of product. Furthermore, since none of these methods can be applied to a liquid photosensitizer, it is not possible to detect the liquid level of the photosensitizer contained in a container, for example.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a photoelectric switch which can be used when a photosensitizer is used in a photographic film manufacturing process or the like. To provide.

[0005]

A photoelectric switch according to the present invention made to solve the above-mentioned problems includes a light-projecting section having a light-emitting diode that emits infrared rays having a wavelength of 1000 nm or more, and infrared rays having a wavelength of 1000 nm or more. And a light-receiving portion provided with a photodiode sensitive to.

[0006]

The light receiving portion is arranged so as to face the light projecting portion or face the same side as the light projecting portion and face the same direction. In the case where the light receiving section is arranged so as to face the light projecting section, an object interposed between the two blocks the light from the light projecting section,
When the two are arranged on the same side, the presence of the object is detected by reflecting the light from the light projecting portion and returning the light from the light projecting portion to the light receiving portion by the object in the direction in which both are facing. In any case, the object to be detected is irradiated with light from the light projecting part, but since the photoelectric switch of the present invention uses infrared rays having a wavelength of 1000 nm or more, the object to be detected is a normal photographic film. , It is not exposed to this detection light.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A reflective photoelectric switch which is an embodiment of the present invention will be described with reference to FIGS. As shown in FIGS. 2 (a), 2 (b) and 2 (c), the photoelectric switch of this embodiment is an integral type in which a light projecting portion, a light receiving portion and peripheral circuits are all housed in a small case.

At the tip of the case 10, a light emitting diode (LED) 11 constituting a light projecting portion, and a photodiode (PD) 12 constituting a light receiving portion and a lens 13 are provided next to the light emitting diode (LED) 11. As the light emitting diode 11, a light emitting diode (long wavelength light emitting diode) which emits infrared rays having a wavelength of 1300 nm or 1550 nm, which has been recently developed for optical communication, is used. Further, the photodiode 12 correspondingly uses a photodiode having a sensitive wavelength in the infrared region of 1000 to 1650 nm. The light projecting unit (light emitting diode 11) and the light receiving unit (photodiode 12 and lens 13) have their optical axes 1
4 and 15 are arranged so as to be inclined so that they intersect each other at a predetermined distance 17 from the lower surface (light emitting / receiving surface) 16 of the case 10. When the surface of the object to be detected is such that the light from the light projecting portion is scattered, the optical axes 14 and 15 of the light projecting portion and the light receiving portion may be set parallel to each other. In this case, it is possible to reduce the processing cost for forming holes for the light projecting portion and the light receiving portion in the case 10.

A flexible printed wiring board (FPCB) 2 is provided in a portion of the case 10 excluding the light projecting portion and the light receiving portion.
The peripheral circuits arranged on the 0 are stored. The electrical configuration of the peripheral circuit will be described later, but the FPCB 20 is bent in a box shape so that the surface on which various elements of the circuit (including a hybrid IC described later) are placed is the case 1
It is stored in 0. Therefore, due to the electromagnetic shielding effect of the FPCB 20, the peripheral circuit is shielded from external noise, and the electromagnetic noise from the noise generation source (such as a pulse lighting circuit described later) included in the peripheral circuit is prevented from being emitted to the outside. There is. A sensitivity adjusting screw 21 to be described later is provided in the center of the case 10 on the opposite side (back side) of the light emitting / receiving surface 16.
Is provided.

Power lines 22 and 23 and an output line 24 extend from an end portion of the case 10 opposite to the light emitting portion / light receiving portion side end portion. When this photoelectric switch is used, the + and-power supply lines 22 and 23 are connected to a DC power supply (battery or the like) of 12 to 24V ± 10%.

The structure of the circuit housed inside the case 10 is shown in FIG. As shown in FIG. 1, in the photoelectric switch of this embodiment, most of the circuit is a hybrid IC (HIC).
It is configured on 30. Each unit of two constant current circuits 31, 32, a constant voltage circuit 33, a pulse lighting circuit 34, an amplifier 35 and a comparator 36 is provided on the hybrid IC 30, and between the amplifier 35 and the comparator 36. A circuit for temperature compensation described later is provided. The hybrid IC 30 includes a unit that generates noise, such as a pulse lighting circuit, but also includes a circuit that dislikes noise, such as a comparator. Therefore, in the hybrid IC 30, these circuits are separately mounted on both surfaces of the FPCB 31 (different from the above) (see FIG. 2A).

The operation of the photoelectric switch of this embodiment is as follows. If a DC power supply is connected between the power lines 22 and 23,
The pulse lighting circuit 34 gives a pulsed drive current (duty is 1/4) of about 4 to 5 kHz to the light emitting diode 11. As a result, the light emitting diode 11 has a wavelength of 1300 nm.
Infrared rays (or 1550 nm) are emitted toward the detection target point 17. When an object exists at that point 17,
This infrared ray is reflected on the surface of the object and is incident on the photodiode 12 by the condenser lens 13. The photodiode 12 converts the received infrared light into an electric signal (photoelectric conversion) and sends it to the amplifier 35.

The weak pulsed electric signal from the photodiode 12 is amplified by the amplifier 35 as an AC signal,
After the voltage is dropped by a temperature compensating diode D1 which will be described later, it is integrated by a capacitor C1 and the comparator 36
Entered in. Note that the reflectance of the surface of the detection target object greatly differs depending on the object and the surface condition, and accordingly the amount of infrared rays returned to the light receiving unit also greatly changes. Therefore, a circuit for adjusting the gain of amplification is provided inside the amplifier 35, and the sensitivity adjusting screw 21 (case 10
(Provided in the center of the back surface of) is turned by a flat-blade screwdriver or the like to change the amplification gain. Accordingly, for example, it is possible to perform sensitivity adjustment so that only the portion to which the mark label having the silver luster is attached is sensitive.

The light reception signal voltage Vpp from the amplifier 35 is subjected to a voltage drop by passing through the forward diode D1 and becomes a voltage V. This diode D1 (the voltage drop thereof) emits light from the light emitting diode 11 due to a change in environmental temperature. It serves to compensate for changes in quantity. This will be described with reference to FIGS. 3 and 4.

As shown in FIG. 3 (this graph is for a GaP LED), the light emitting diode has a characteristic that the amount of light emission (relative luminance) decreases as the ambient temperature rises even when the same drive current is applied ( Temperature coefficient is about -1% /
℃) have. Therefore, even if the detection criterion is set that an object is present when a certain amount or more of infrared rays are returned, even if the infrared emission amount itself decreases due to a change in ambient temperature, even if an object is present. There is a possibility of making an erroneous determination as a nonexistence. Therefore, conventionally, a temperature compensation circuit as shown in FIG. 4 has been provided. This circuit uses a thermistor RTH whose resistance value changes according to the ambient temperature (the resistance value decreases as the temperature rises).
Light-emitting diode LED to compensate for the decrease in LED light output
The driving current is increased to keep the amount of light emission constant.

In the photoelectric switch of this embodiment, instead of the complicated circuit using the thermistor and the transistor Tr, the change of the light emission amount of the light emitting diode 11 is compensated by only the diode D1 which changes the voltage drop amount depending on the ambient temperature. I decided to do it. That is, when the light emission amount of the light emitting diode 11 decreases due to the temperature rise, the light reception amount of the photodiode 12 also decreases accordingly, and the output Vpp of the amplifier 35 decreases.
However, since the voltage drop of the diode D1 decreases as the temperature rises, the input voltage V of the comparator is kept almost constant.

In this way, the output V of the temperature-compensated amplifier 35 is compared with the judgment reference value by the comparator 36. In the circuit of FIG. 1, the current from the constant current circuit is used as the determination reference, but a reference potential generator may be separately provided and the determination may be performed based on the voltage reference. When the comparator determines that the amount of received light is equal to or greater than the predetermined value, the transistor Q1 is turned on, and the load (for example, solenoid) connected to the output line 24 is driven.

Since the photoelectric switch of this embodiment uses infrared rays having a wavelength of 1000 nm or more as detection light, it does not need to be exposed to a photosensitizer such as ordinary photographic film (the photosensitive region is near infrared rays of visible light to 900 nm). It is possible to detect the passage of the film and the liquid level.

The photoelectric switch of the above embodiment has a feature that the light emitting portion, the light receiving portion, and the peripheral circuit are integrated, and thus the handling is simple. However, when there is no space for arranging such an integrated unit in the production line of film or the like, a method of guiding the incident light and the reflected light from the light projecting unit and the light receiving unit to the vicinity of the detection position by an optical fiber is adopted. You can also Therefore, also in the above embodiment, sockets for connecting the optical fibers may be provided in the holes of the light projecting portion and the light receiving portion of the case 10. Further, instead of integrally forming the light projecting portion and the light receiving portion, both may be separable so that transmission type detection can be performed.

[0020]

Since the photoelectric switch according to the present invention uses infrared rays having a wavelength of 1000 nm or more as the detection light, it can detect the passage of the product (or the photosensitizer itself) using the ordinary photosensitizer and the level detection. Etc. can be used. As the photosensitizer, not only a normal photosensitizer sensitive to visible light (and near infrared rays having a wavelength of 1000 nm or less) but also a photosensitizer sensitive to ultraviolet rays can be used. Therefore, the photoelectric switch according to the present invention can be used not only in the normal photographic film manufacturing process but also in the IC manufacturing process and the like.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a photoelectric switch that is an embodiment of the present invention.

FIG. 2 is a front sectional view (a), a side sectional view (b) and a plan sectional view (c) of an integrated photoelectric switch that is an embodiment of the present invention.

FIG. 3 is a graph showing the relationship between the ambient temperature of a light emitting diode and the amount of emitted light.

FIG. 4 is a circuit diagram of a conventional circuit for compensating for a change in the amount of light emitted from a light emitting diode due to temperature.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Photoelectric switch case 11 ... Light emitting diode 12 ... Photodiode 13 ... Lens 14 and 15 ... Optical axis 16 ... Light emitting / receiving surface 21 ... Sensitivity adjusting screw 22, 23 ... Power supply line 24 ... Output line 30 ... Hybrid IC 31, 32 ... Constant current circuit 33 ... Constant voltage circuit 34 ... Pulse lighting circuit 35 ... Amplifier 36 ... Comparator D1 ... Temperature compensation diode

Claims (1)

Claim: What is claimed is: 1. A light-emitting unit having a light-emitting diode that emits infrared rays having a wavelength of 1000 nm or more, and a light-receiving unit having a photodiode that is sensitive to infrared rays having a wavelength of 1000 nm or more. And photoelectric switch.