JPH0716795B2 - Laser emission port protection glass plate dirt detection device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a device for automatically detecting dirt on a protective glass plate provided at a laser emission port.

[Prior Art] In a laser processing machine, a glass plate for protecting a condenser lens from splashes and metal vapor flying from a workpiece is attached to a laser beam emission port.

Therefore, this type of protective glass plate is apt to be contaminated by splashes and metal vapors, and leaving it unattended will reduce the laser beam irradiation amount and affect the processing quality. The board needs to be replaced.

[Problems to be Solved by the Invention] Conventionally, the replacement time of the protective glass plate due to the above-mentioned stains is judged at the time when a processing defect actually occurs, or sometimes the condition of stains on the glass is visually checked. It was either decided.

However, if the protective glass plate is replaced after the defective processing occurs, the protective glass plate may be lost lately, while visual judgment is a troublesome work for the operator.

The present invention has been made in view of the above problems, and provides a protective glass plate contamination detection device capable of automatically detecting contamination of a protective glass plate provided at a laser emission port and notifying the replacement time. The purpose is to

[Means for Solving the Problems] In order to achieve the above-mentioned object, the first laser emission port protection glass plate dirt detection device according to the present invention is designed to clean the protection glass plate provided at the laser light exit port. In a protective glass plate contamination detection device for detecting the condition, the protective glass plate formed in a size larger than the laser emission port, and the light receiving surface of the protective glass plate at a portion outside the optical path of the laser light. And an optical sensor that receives laser light emitted from the glass boundary surface by repeating internal reflection inside the protective glass plate, and determines the degree of contamination of the protective glass plate based on the output signal of the optical sensor. And a determination circuit for

A second laser emission port protection glass plate dirt detection device of the present invention is the first laser emission port protection glass plate dirt detection device, wherein the protection glass plate is sandwiched between the optical sensor and the opposite side. The light shielding plate is arranged.

[Operation] When dirt such as splash or spatter adheres to the protective glass plate, a part of the laser light is reflected inside the glass plate by the adhered substance, and the reflected light is partially reflected on the boundary surface of the glass plate. It goes to the side while repeating partial penetration. Then, the transmitted light emitted from the glass boundary surface adjacent to the optical sensor enters the light receiving surface of the sensor. Since the light intensity of the laser light is extremely high, the light attenuated by repeating the internal reflection several times in this way has a proper light intensity to be detected by the sensor.

Even if there is no deposit, there is a slight reflection at the glass interface, so there is light that enters the photosensor by the same action as described above, but its light intensity is quite low.

When the glass plate is clean, the amount of light incident on the sensor light receiving surface is small, but as the glass plate becomes dirty, the amount of light incident on the sensor light receiving surface increases, and the output signal of the sensor also increases accordingly. Then, when the output signal of the sensor exceeds the reference value, the determination circuit determines that the degree of contamination of the glass plate exceeds the allowable value.

Since the optical sensor is placed outside the laser emission port,
It is possible to effectively prevent undesired light from entering the light receiving surface of the sensor, which is convenient for mounting. Further, by disposing the light shielding plate, the influence of ambient light can be prevented, and the detection accuracy is further improved.

Embodiments Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an emission part of a laser processing machine to which an embodiment of the present invention is applied. FIG. 2 shows the circuit configuration of the protective glass plate stain detection device of this embodiment.

In FIG. 1, a protective glass plate 12 is attached to the emission port of the laser emission unit 10, and a condenser lens 14 is provided inside (rear) of the protective glass plate 12.
Are arranged.

The laser light LS sent from a laser generator (not shown) through an optical transmission means such as a mirror and an optical fiber is condensed by a condenser lens 14 and is applied to a workpiece 16 at a predetermined position. . By this laser processing, splashes or spatters (metal vapor) flying from the workpiece 16 hit the protective glass plate 12 and adhere thereto. Therefore, although the protective glass plate 12 is soiled, the condenser lens 14 is kept clean without being soiled.

The protective glass plate 12 is a support member 1 provided around the emission port.
8, supported by a guide plate 20 so as to be slidable in the direction of arrow F. As a result, a clean glass region can be set on the laser optical path by shifting the dirty portion of the protective glass plate 12, and one protective glass plate 12 can be effectively used.
Of course, when the clean glass area is gone, replace it with a new glass plate.

A box 22 is provided between the outer surface of the housing of the emitting unit 10 and the guide plate 20, and an optical sensor 24 including a phototransistor or a photodiode is disposed in the box 22. The light receiving surface 24a of the sensor 24 is directed to the glass plate 12 through the opening 20a of the guide plate 20. As a result, a part of the laser light LS reflected on the inner surface of the glass plate 12 on the optical path propagates sideways while repeating inner surface reflection, and the light emitted outside through the opening 20a of the guide plate 20 is the sensor light receiving surface 24a. It is designed to be incident on. In addition, in order to minimize the incidence of ambient light on the sensor light-receiving surface 24a and to improve the detection capability, a glass plate
A light-shielding plate 26 is arranged on the opposite side of the optical sensor 24 with the 12 in between.

In FIG. 2, the output current SI of the optical sensor 22 is converted into a voltage signal SV by the current-voltage conversion circuit 28, and this voltage signal SV is given to one input terminal of the comparison circuit 30. On the other hand, the allowable limit value (upper limit value) of the degree of dirt on the glass plate 12 is set by the digital switch 32, and the voltage signal QV corresponding to the limit value is supplied from the upper limit value setting circuit 34 to the other input terminal of the comparison circuit 30. Given. The comparator circuit 30 has both input signals SV and QV.
When the former exceeds the latter, the output signal CO of the theoretical value "H" is generated. When the judgment circuit 36 receives the output signal CO (“H”), it judges that the degree of dirt on the glass plate 12 has exceeded the upper limit value, and the protection glass plate 12 is replaced or reset (shifted). The warning message to be instructed is displayed on the display unit 38.

Next, the operation of this embodiment will be described with reference to FIGS.

In FIG. 3, the surface of the protective glass plate 12 facing the workpiece (not shown) is contaminated by splashes or spatters.
DA1 and DA2 are attached. A part of the laser light LS is reflected inside the glass plate 12 by these adhering substances DA1 and DA2, and the reflected light LS1 and LS2 are laterally reflected while partially reflecting and partially transmitting at the boundary surface of the glass plate 12. Proceed to. And optical sensor
Transmitted light from the glass interface close to 24 ΔLS1, ΔLS2
Is incident on the sensor light receiving surface 24a. Since the light intensity of the laser beam LB is extremely high, the light beams ΔLS1 and ΔLS2 attenuated by repeating the internal reflection several times in this way have a proper light intensity for being detected by the sensor 24.

Such transmitted lights ΔLS1 and ΔLS2 exist even when there is no attached matter DA1 and DA2, but the light intensity thereof is considerably low. Therefore, when the glass plate 12 is clean, the sensor light receiving surface 24a
Although the amount of light incident on is small, the amount of light incident on the sensor light receiving surface 24a increases as the glass plate 12 becomes dirty.

FIG. 4 shows the level of the output signal of the optical sensor 24 when the protective glass plate 12 is clean and when it is soiled to some extent. As can be seen from this figure, when the glass plate 12 gets dirty, the output signal of the optical sensor 24 increases.

Then, when the protective glass plate 12 is considerably soiled and the sensor output signal exceeds a predetermined value, the soiling detecting device of the present embodiment (second
In the figure), the output signal CO is generated from the comparison circuit 30, and in response to this, the judgment circuit 36 and the display 38 issue an alarm message. The worker who receives this message may shift the protective glass plate 12 to set a clean glass region on the optical path, or replace it with a new glass plate. There is no need for the operator to visually check the degree of dirt on the protective glass plate 12 by making it visible.

Note that it is possible to automate the replacement of the protective glass plate, and in that case, the glass plate replacement device may be operated in response to the output signal of the comparison circuit 30 or the determination circuit 36. Further, when the warning message is issued, the processing may be temporarily stopped. Further, the present invention can be applied to any laser device other than the laser processing machine, in which the protective glass easily gets dirty.

[Advantages of the Invention] The present invention, which is configured as described above, has the following advantages.

Since the light internally reflected by the glass plate due to the dirt attached to the protective glass plate is received near the optical path of the laser beam, the dirt on the glass plate can be detected without affecting the original laser emission.

Since the determination circuit automatically determines the degree of contamination based on the output signal of the optical sensor corresponding to the degree of contamination of the glass plate, it is possible to replace the glass plate in a timely manner and eliminate the need for visual inspection.

By arranging the optical sensor outside the laser emission port,
It is possible to effectively prevent undesired light from entering the light receiving surface of the sensor. Also, the optical sensor is easier to mount in the outer arrangement than in the inner arrangement.

Then, by disposing the light shielding plate on the opposite side of the optical sensor with the glass plate interposed therebetween, it is possible to prevent the influence of ambient light and further improve the detection accuracy.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional side view showing the configuration of a laser emission part to which an embodiment of the present invention is applied, and FIG. 2 is a block circuit diagram showing the circuit configuration of a protective glass plate stain detection device according to the embodiment. FIG. 3 is a partially enlarged schematic cross-sectional view of the main part of the laser emitting portion for explaining the operation of the embodiment, and FIG. 4 shows light when the protective glass plate 12 is clean and when it is soiled to some extent. 5 is a diagram showing the level of an output signal of the sensor 24. FIG. In the drawing, 10 ... laser emitting part, 12 ... protective glass plate, 14 ... condensing lens, 24 ... photosensor, 24a ... light receiving surface, 26 ... shading plate, 30 ... comparison circuit, 34 ... … Upper limit setting circuit, 36 …… Judgment circuit, 38 …… Indicator.

Claims (2)

[Claims] 1. A contamination detection device for a laser emission port protection glass plate for detecting the degree of contamination of a protection glass plate provided at a laser beam emission port, wherein the protection glass is formed in a size larger than the laser emission port. The plate and the protective glass plate are arranged with their light-receiving surface facing the portion outside the optical path of the laser light, and the laser light emitted from the glass boundary surface by repeating internal reflection inside the protective glass plate is received. And a determination circuit that determines the degree of contamination of the protective glass plate based on the output signal of the optical sensor. 2. The dirt detection device for a laser emission port protective glass plate according to claim 1, wherein a light shielding plate is arranged on the opposite side of the optical sensor with the protective glass plate interposed therebetween.