JPH01233911A - Operating method for photoelectric switch - Google Patents

Abstract

PURPOSE:To strengthen an output light at the adjustment so as to facilitate the adjustment and to weaken the output light at the activation so as to offer a long service life for the semiconductor laser by adopting the constitution so that an optional output luminous intensity is obtained in a photoelectric switch employing the semiconductor laser for its projection section. CONSTITUTION:An output control circuit 2 of the semiconductor laser 1 has a pulse light drive circuit 21 and a DC light drive circuit 22. Then the circuits 21, 22 are connected to a power supply 3 by a changeover switch 4. In case of the optical axis adjustment or the like, the changeover switch 4 is connected to the DC light drive circuit 22 and the semiconductor laser 1 is stimulated continuously by the continuous drive. After the end of the optical axis adjustment when normal detection is to be implemented, the switch 4 is thrown to the position of the pulse light drive circuit 21. The drive circuit 21 consists, e.g., of an oscillation circuit and a switching transistor(TR) and the oscillated output of the oscillation circuit applies turn-on/turn-off control to the switching TR, thereby intermitting the drive current of the semiconductor laser 1. The duty ratio is given by b/a in figure.

Description

[Detailed Description of the Invention] Summary of the Invention In a photoelectric switch using a semiconductor laser in a light projecting section,
To enable output light to be switched between continuous oscillation and pulse oscillation. Alternatively, the duty ratio of pulse oscillation can be set arbitrarily. This makes it possible to obtain any output light intensity.

During adjustment, the output light is strengthened to facilitate adjustment, and during operation, the output light is weakened to prolong the life of the semiconductor laser.

BACKGROUND OF THE INVENTION The present invention relates to a method of operating a photoelectric switch using a semiconductor laser as a light source, and particularly to a method of operating a photoelectric switch for adjusting an optical axis.

Adjustment of the non-optical axis is one of the difficult tasks when installing or adjusting a photoelectric switch, especially a transmission type photoelectric switch in which a light emitter and a light receiver are arranged facing each other. If the projected light from the photoelectric switch is weak, the projected light cannot be seen or is difficult to see, so it takes a long time to adjust the optical axis. This is especially difficult when the projected light is infrared or near-infrared light.

On the other hand, if the intensity of the projected light of the photoelectric switch is increased, the projected light becomes visible or easier to see.

Optical axis adjustment becomes easier. However, since the semiconductor laser serving as the light source is driven with a large current, its lifespan is shortened. Also.

Since laser light has a relatively small beam diameter and high energy, high-intensity laser light is dangerous to the human body, especially the eyes.

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, an object of the present invention is to provide a method for operating a photoelectric switch that facilitates optical axis adjustment, extends life, and is safe.

The operating method of a photoelectric switch using a semiconductor laser as a light source according to the present invention is to drive the semiconductor laser with continuous light emission or pulsed light emission with a relatively large duty ratio to adjust the output light intensity when adjusting and installing the photoelectric switch. 5. During normal operation, the output light intensity is set relatively low by driving the semiconductor laser to emit pulses with a relatively small duty ratio.

According to this invention, for yJ adjustment and optical axis adjustment during installation, the output light intensity is increased by using a semiconductor laser as a light source to perform continuous oscillation or pulse oscillation with a large duty ratio. Therefore, the projected light beam is visible or easy to see, making it easy to adjust the optical axis. On the other hand, by using pulse oscillation or pulse oscillation with a small duty ratio during operation, the life of the semiconductor laser can be extended and the output light intensity is low.

It is also safe against direct light.

This invention is particularly useful for photoelectric switches that employ Fresnel lenses. When a normal convex lens is used, the semiconductor laser light is not very strong (for example, the diameter is 5rII
Although it is not possible to narrow down the aperture (approximately 1 mm), it is possible to make the connection extremely small (for example, approximately 1 mm) using a finnel lens.

The energy per unit area of the projected laser beam becomes strong.

Therefore, this laser light is dangerous to the human body.

In the present invention, pulse oscillation with a relatively large duty ratio is used during normal operation, so it is relatively safe. Further, when the semiconductor laser light is near-infrared light, the laser beam can be made into continuous oscillation or pulse oscillation with a large duty ratio, and it can be seen by narrowing down to a small size, making it easier to adjust the optical axis.

This invention is of course applicable not only to transmission type photoelectric switches but also to reflective type photoelectric switches.

Description of Examples Figure 1 shows the output light intensity when the semiconductor laser as the light source of the photoelectric switch is continuous oscillation during adjustment (including installation) and pulse oscillation during normal detection operation. It is.

Such control can be realized, for example, by the configuration shown in FIG. In this figure, the output control circuit 2 of the semiconductor laser 1 includes a pulse lighting drive circuit 21 and a DC lighting drive circuit 2.
2. And these circuits 2r, 22
is connected to the power source 3 by a changeover switch 4.

For optical axis adjustment and the like, the changeover switch 4 is connected to a DC lighting drive circuit 22, and the semiconductor laser 1 is continuously driven to oscillate continuously. Optical axis adjustment etc. are completed.

When performing a normal detection operation, the switch 4 is switched to the pulse lighting drive circuit 21 side. This drive circuit 21 includes, for example, an oscillation circuit and a switching transistor, and controls the switching transistor to be turned on and off by the oscillation outputs of the two oscillation circuits, thereby intermittent the drive current of the semiconductor laser 1.

The duty ratio is given by b/a in FIG.

FIGS. 3 and 4 show the output light intensity when the semiconductor laser is caused to emit pulses with a large duty ratio during adjustment and emit small pulses during operation.

In FIG. 3, the pulse period is kept constant and the duty ratio is varied. Duty ratio b/a during adjustment > 1 during operation
duty ratio b1/a1> duty ratio b of 2 during operation
The relationship is /a. During operation, 1 and 2 may be switched as necessary.

In FIG. 4, the pulse 111 (on time) is kept constant and the duty ratio is changed, and the relationship between the duty ratios during adjustment and during operation 1 and 2 is the same as that shown in FIG.

Such operation control can be realized using the circuit shown in FIG. In this figure, the same parts as shown in FIG. 2 are given the same reference numerals. By changing the variable resistor 5 included in the pulse lighting drive circuit 21, it is possible to change or switch the pulse duration or frequency of one oscillation.

[Brief explanation of the drawing]

1 and 2 show a first embodiment, FIG. 1 is an output signal waveform diagram, and FIG. 2 is a block diagram showing an operation control circuit. 3 to 5 show the second embodiment, FIGS. 3 and 4 are output signal waveform diagrams, and FIG. 5 is a block diagram of the operation control circuit. 1... Semiconductor laser, 2... Output control circuit. 3...Power supply, 4...Selector switch 5.
...Variable resistance. 21...Pulse lighting drive circuit. 22...DC lighting drive circuit. Above Figure 1 Figure 2

Claims (1)

[Claims] In a photoelectric switch that uses a semiconductor laser as a light source, when adjusting and installing the photoelectric switch, drive the semiconductor laser with continuous light emission or pulsed light emission with a relatively large duty ratio to set the output light intensity relatively high. A method for operating a photoelectric switch, characterized in that during normal operation, the output light intensity is set relatively low by driving a semiconductor laser to emit pulses with a relatively small duty ratio.