JPH01186296A - Device for detecting stain on protection glass plate of laser outgoing port - Google Patents

Abstract

PURPOSE:To automatically detect the stain of a protection glass plate by receiving the light subjected to the inner face reflection by the glass plate with the stain sticked on the protection glass plate at the vicinity of the light path of a laser light. CONSTITUTION:When the stain of a splash or spatter, etc., is sticked on a protection glass plate 12, one part of a laser light LS is reflected to the inner side of the glass plate by its attachment and its reflection light proceeds to the side part with repeating partial reflection and partial transmission on the boundary face of the glass plate. The transmission light coming out of the glass boundary face approaching to an optical sensor 24 is made incident on the light receiving face of the sensor 24. As the optical strength of the laser light LS is extremely large the attenuated light by repeating the inner face reflection several times like this attains a moderate strength for being detected by the sensor 24. The incident light amt. onto the sensor light receiving face 24a is increased in case of a stain existing, the output signal of the sensor 24 is also made large accordingly and it is decided that the stain state of the glass plate 12 exceeds the allowable value, in a judgement circuit 36.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for automatically detecting dirt on a protective glass plate provided at a laser emission aperture.

[Prior Art] In a laser processing machine, a glass plate is attached to the laser beam exit to protect the condenser lens from splash and metal vapor flying from the workpiece.

Therefore, this type of protective glass plate is easily exposed to splashes and metal vapors and gets dirty easily.If this is left untreated, the amount of laser light irradiation will decrease and the processing quality will be affected, so please check the protective glass plate in a timely manner. The board needs to be replaced.

[Problems to be solved by the invention] Conventionally, the time to replace the protective glass plate due to dirt as described above was determined at the time when a processing defect actually occurred, or by visually checking the degree of dirt on the glass from time to time. The decision was either made or made.

However, if the protective glass plate is replaced after a processing defect occurs, it may be too late, and on the other hand, visual judgment is a troublesome task for workers.

The present invention has been made in view of such problems, and provides a protection glass plate dirt detection device that can automatically detect dirt on a protection glass plate provided at a laser emission port and notify the time to replace the protection glass plate. The purpose is to

[Means for Solving the Problems] In order to achieve the above object, the protection glass plate dirt detection device of the present invention includes a light receiving surface on the protection glass plate at a position beside the optical path of the laser beam at the laser exit aperture. The present invention is configured to include an optical sensor directed toward the protective glass plate, and a determination circuit that determines the degree of contamination of the protective glass plate based on the output signal of the optical sensor.

Advantageously, the optical sensor is provided outside the laser exit. In that case, the protective glass plate used is large enough to protrude from the laser exit aperture. Further, it is preferable to arrange a light shielding plate on the opposite side of the optical sensor with the glass plate in between.

[Operation] When dirt such as splash or spatter adheres to the protective glass plate, part of the laser beam is reflected inside the glass plate by the deposit, and the reflected light is partially reflected at the boundary surface of the glass plate, and then Proceed laterally while repeating partial penetration. Then, transmitted light emitted from the glass boundary surface close to the optical sensor enters the light receiving surface of the sensor. Since the light intensity of laser light is extremely high, the light that is attenuated by repeating internal reflection several times in this way has a light intensity that is suitable for being detected by a sensor.

Since there is no deposit (although there is a small amount of reflection at the glass boundary surface), there is light that enters the optical sensor due to the same effect as described above, but the light intensity is quite low.

Therefore, 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. 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 permissible value.

Note that if the optical sensor is placed outside the laser emission port, it is possible to effectively prevent unwanted light from entering the sensor light-receiving surface, and it is also convenient for installation. Further, by arranging the light shielding plate, the influence of ambient light can be prevented, and detection accuracy is further improved.

Example] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an output section 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 opening of the laser emission unit 10, and a condensing lens 14 is arranged inside (backward) thereof.

A laser beam LS sent from a laser generator (not shown) through an optical transmission means such as a mirror or an optical fiber is condensed by a condensing lens 14 to a workpiece 16 at a predetermined position.
is irradiated. By this laser processing, the workpiece 16
The more flying splash or spatter (metal vapor) hits the protective glass plate 12 and adheres thereto. Therefore, although the protective glass plate 12 becomes dirty, the condensing lens 14 is kept clean without becoming dirty.

The protective glass plate 12 is supported by a support member 18 provided around the exit aperture. It is supported by a guide plate 20 so as to be slidable in the direction of arrow F. As a result, a clean glass area can be set on the laser beam path by shifting the dirty portion of the protective glass plate 12, and the -th protective glass plate 12 can be used effectively. Of course, if there is a clean glass area, replace it with a new glass plate.

Now, a box 22 is provided between the outer surface of the housing of the emission section 10 and the guide plate 20, and an optical sensor 24 made of a phototransistor or a photodiode is arranged in the box 22. A light receiving surface 24a of this sensor 24 is directed toward the glass plate 12 through an opening 20a of the guide plate 20. As a result, a part of the laser beam LS reflected on the inner surface of the glass plate 12 on the optical path propagates laterally while repeating inner reflection, and the light exiting through the opening 20a of the guide plate 20 is transmitted to the sensor light receiving surface 24a. It is designed to be incident on . In addition,
A light shielding plate 26 is placed on the opposite side of the optical sensor 24 with the glass plate 12 in between to minimize the incidence of ambient light on the sensor light receiving surface 24a and to increase detection performance.

In FIG. 2, the output current SI of the optical sensor 22 is -
The voltage conversion circuit 28 converts it into a voltage signal SV, and this voltage signal SV is applied to one input terminal of the comparison circuit 30. On the other hand, the digital switch 32 causes the glass plate 12 to
A permissible limit value (upper limit value) for the degree of contamination is set, and a voltage signal QV corresponding to the limit value is applied from the upper limit value setting circuit 34 to the other input terminal of the comparator circuit 30. Comparison circuit 30 compares the levels of both human power signals SV and QV, and when the former exceeds the latter, generates an output signal CO having a logic value of "H". The determination circuit 36 outputs its output signal CO (“H”)
When inputting , it is determined that the degree of contamination of the glass plate 12 exceeds the upper limit value, and an alarm message instructing to replace or reset (shift position) the protective glass plate 12 is displayed on the display 38.

Next, the operation of this embodiment will be explained with reference to FIGS. 3 and 4.

In FIG. 3, splash or sputter stains DAl and DA2 are attached to the surface of the protective glass plate 12 facing the workpiece (not shown).

A portion of the laser beam LS is absorbed by these deposits DA1. The reflected light LS1 is reflected to the inside of the glass plate 12 by DA2.
．． LS2 travels laterally while repeating partial reflection and partial transmission at the boundary surface of the glass plate 12. Then, transmitted light ΔLSI, ΔL emitted from the glass interface near the optical sensor 24
S2 enters the sensor light receiving surface 24a. Since the light intensity of the laser beam LB is extremely high, the attenuated light ΔLSI, ΔLS after repeating internal reflection several times in this way
2 has an appropriate light intensity to be detected by the sensor 24.

Such transmitted light ΔLSI and ΔLS2 are the deposits DA1
．． Although it exists even when DA2 is not present, its light intensity is quite low. Therefore, when the glass plate 12 is clean, the amount of light incident on the sensor light receiving surface 24a is small;
As the glass plate 12 becomes dirty, the sensor light receiving surface 24a
The amount of incident light is increasing.

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 somewhat dirty. As can be seen from this figure, when the glass plate 12 becomes dirty, the output signal of the optical sensor 24 increases.

However, if the protective glass plate 12 becomes considerably dirty and the sensor output signal exceeds a predetermined value, the dirt detection device (second
In the figure), an output signal CO is generated from the comparator circuit 30,
In response to this, the determination circuit 36 and display 38 issue an alarm message. The operator who receives this message can either shift the protective glass plate 12 and set a clean glass area on the optical path, or replace it with a new glass plate. There is no need for the worker to keep up and visually check the degree of dirt on the protective glass plate 12.

Note that it is also 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 a warning message is issued, processing may be temporarily interrupted. Furthermore, the present invention can be applied to any laser device in which the protective glass is likely to get dirty, other than laser processing machines.

[Effects of the Invention] Since the present invention is configured as described above, it has the following effects.

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

Since the degree of contamination of the glass plate is automatically determined by the determination circuit based on the output signal of the optical sensor corresponding to the degree of contamination of the glass plate, timely replacement of the glass plate is possible and visual inspection is not required.

By placing the optical sensor outside the laser exit,
Unwanted light can be effectively prevented from entering the sensor light receiving surface. Furthermore, it is easier to attach the optical sensor in the outer arrangement than in the inner arrangement.

By arranging a light shielding plate on the opposite side of the optical sensor across the glass plate, it is possible to prevent the influence of ambient light and further improve detection accuracy.

[Brief explanation of the drawing]

FIG. 1 is a partially cross-sectional side view showing the configuration of a laser emitting section to which an embodiment of the present invention is applied; FIG. 2 is a block circuit diagram showing the circuit configuration of the protective glass plate dirt detection device of the embodiment; FIG. 3 is a partial cross-sectional schematic enlarged view of the main part of the laser emitting part for explaining the operation of the embodiment, and FIG. 4 shows the light when the protective glass plate 12 is clean and dirty to some extent. 3 is a diagram showing the level of an output signal of a sensor 24. FIG. In the drawings, 10... Laser emission part, 12... Protective glass plate, 14... Condensing lens, 24... Optical sensor, 24a... Light receiving surface, 26... - Light shielding plate, 30... Comparison circuit, 34... Upper limit setting circuit, 36... Judgment circuit, 38... Display device. Patent applicant Miyaji Denshi Co., Ltd. Company agent
Patent attorney Takashi Sasaki Special question on Figure 2 and Figure 4

Claims (3)

[Claims] (1). A device for detecting the degree of contamination of a protective glass plate provided at a laser beam exit, comprising: an optical sensor with a light-receiving surface facing the protective glass plate at a position beside the optical path of the laser beam; A protection glass plate dirt detection device comprising: a determination circuit that judges the degree of dirt on the protection glass plate based on an output signal. (2). 2. The protective glass plate stain detection device according to claim 1, wherein the protective glass plate is larger than the laser exit port, and the optical sensor is disposed outside the laser exit port. (3). 3. The protective glass plate stain detection device according to claim 1, further comprising a light shielding plate disposed on the opposite side of the optical sensor across the glass plate.