JP2017196629A - Dirt detection device of protective glass, laser beam machine including the same, and dirt detection method of protective glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dirt detection method and a device of a protective glass for performing highly-accurate dirt detection.SOLUTION: There is provided a dirt detection device of a protective glass for detecting dirt of the protective glass mounted on a laser processing head of a laser beam machine. The dirt detection device of the protective glass includes an LED light incidence part for allowing incidence of LED light into the protective glass so that LED light is totally reflected inside the protective glass, and an LED light detection part arranged on the end face facing to the LED light incidence part of the protective glass.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a protective glass stain detection device, a laser processing machine including the same, and a protective glass stain detection method.

  A laser processing head that emits laser light in a laser processing machine includes an optical system such as an expensive condensing lens that condenses the laser light and irradiates the sample (workpiece). On the other hand, when the sample (work) is subjected to laser processing by irradiating the sample (work) with laser light, the generated spatter and fumes are diffused and scattered around, and the optical system such as the condenser lens is contaminated. If spatter or fume adheres to the condenser lens, etc., and is contaminated, the condenser lens etc. cannot perform its original optical function such as the condenser function, and laser light is scattered or excessive heat is applied to the condenser lens. May occur.

  Therefore, in order to avoid such problems and to protect the optical system such as the condensing lens from contaminants such as spatter and fume, the condensing lens and the like are usually protected from spatter in the laser processing head. , Equipped with protective glass.

  By providing the laser processing head with the protective glass, it is possible to protect the optical system such as the condenser lens from sputtering or the like, but instead, the protective glass is contaminated by sputtering or the like. When the protective glass is contaminated, the quality of the laser processing is deteriorated such that the laser beam does not reach a desired processing position with a desired output.

  For this reason, various methods for protecting the protective glass from contaminants such as spatter and fumes generated during laser processing and various methods for detecting the dirt in order to grasp the replacement timing of the protective glass have been proposed. In addition, there is a measure to give up detection of the contamination of the protective glass and replace the protective glass every predetermined laser processing time or periodically.

  For example, in the following Patent Document 1, since a small amount of light has been detected in the past, the detection level is low and it is easily affected by externally incident disturbances. An invention for detecting dirt on a protective glass aimed at solving these problems is disclosed.

  According to this, the method for detecting contamination of the protective glass provided in the laser processing head, wherein the detection light is incident on the protective glass from the outer peripheral surface of the protective glass and reflected by the peripheral surface of the protective glass. The contamination of the protective glass is detected by detecting the amount of detection light irregularly reflected by the contaminant attached to the protective glass and leaking from the outer peripheral surface by a light detection means provided on the peripheral surface of the protective glass. The invention is described.

  According to the invention of Patent Document 1, “detection light is incident from the outer peripheral surface of the protective glass into the protective glass. Therefore, the incident detection light is reflected by the upper and lower inner surfaces and the inner peripheral surface of the protective glass. Therefore, even if the incident position of the detection light is one, the detection light is transmitted through the entire inside of the protective glass. When the light is emitted from the outer peripheral surface of the glass to the outside, it is detected by the light detection means.

  Therefore, the amount of light detected by the light detection means is large, and adhesion such as sputtering can be reliably detected. Further, since the amount of detection light is large, the detection level can be increased and the influence of disturbance can be suppressed. It is described in Patent Document 1 that there is an effect of "".

  Patent Document 2 listed below includes a condensing lens that condenses laser light oscillated from a laser oscillator and irradiates the work, and is provided on the work side of the condensing lens to protect the condensing lens. A laser processing head comprising a protective glass and a dirt detecting means for detecting dirt on the protective glass, wherein the detection light is applied to the protective glass from a direction inclined with respect to the optical axis of the laser light. An invention characterized in that it is provided with detection light irradiating means for irradiating is described.

  According to Patent Document 2, since the detection light from the detection light irradiation means is inclined with respect to the optical axis of the laser beam and can be applied to the protective glass, dirt is generated near the periphery of the protective glass. It is described that it can be easily detected even when the protective glass is present, and therefore, the entire dirt state of the protective glass can be detected, and the protective glass can be replaced properly.

JP 2014-237150 A JP2013-052440A

  In addition, since the protective glass is a relatively expensive part with a high level of required functional surface, such as a highly accurate flatness and a small transmission loss, in periodic replacement of the protective glass, Although it can still be used, it is not preferable because it causes an increase in cost such as replacement. On the other hand, when checking the degree of contamination of the protective glass by visual inspection, the laser processing machine must be stopped in order to reliably block the laser light, so that the productivity deteriorates, for example, the manufacturing throughput decreases. Also, in the unlikely event that laser light leaked or its scattered light is irradiated to an operator who is inspecting without reliably blocking the laser light, there may be serious health hazards and serious safety issues. Will cause serious concerns.

  Moreover, in the dirt detection method of patent document 1 known conventionally, since incident light incident on the protective glass is irregularly reflected by the upper and lower inner surfaces and the inner peripheral surface, a plurality of primary reflections, secondary reflections, etc. High-order reflected light is simultaneously detected and accurate measurement is difficult. Furthermore, there is a concern that the detection light becomes extremely fragile because the detection light is emitted and leaked to the outside from the dirt adhering portions on the upper and lower inner surfaces and the inner peripheral surface of the protective glass. Since the fragile detection light contains a large amount of relatively large noise other than the dirt adhering to the protective glass, it is difficult to detect the dirt of the protective glass with high accuracy. Moreover, it had the characteristic that it was very weak to the influence of the disturbance by the environmental light which injects from the outside of protective glass.

  The present invention has been made in view of the above-described problems. By detecting the light emitted from the opposite end surface by allowing the detection light from the LED to be totally reflected in the protective glass from the outer peripheral surface of the protective glass. An object of the present invention is to provide a protective glass contamination detection device that safely performs highly accurate contamination detection, a laser processing machine including the same, and a protective glass contamination detection method.

  The protective glass contamination detection device of the present invention is a protective glass contamination detection device that detects the contamination of the protective glass mounted on the laser processing head of the laser processing machine. LED light is applied to the protective glass within the protective glass. The LED light incident part which makes LED light enter so that it may totally reflect, and the LED light detection part arrange | positioned at the end surface facing the LED light incident part of a protective glass, It is characterized by the above-mentioned.

  The protective glass contamination detection device of the present invention preferably further includes a display unit for displaying a ratio of the amount of detection light detected by the LED light detection unit to the amount of light before the LED light is incident on the protective glass. It is characterized by providing.

  In the protective glass contamination detector of the present invention, the LED is preferably pulsed light, and the incident angle to the reflection plane inside the protective glass is more than a critical angle and less than 90 °. . The incident angle from the air to the medium (protective glass) is appropriately set so that the light incident angle to the reflection plane inside the protective glass exceeds the critical angle. That is, the incident angle to the reflection plane inside the protective glass (typically, the circular upper surface and the circular lower surface of the protective glass) exceeds the critical angle so that total reflection occurs in the glass. Further, in this case, the closer the incident angle is to the critical angle, the more the number of internal reflections, and this is advantageous for dirt detection (see FIG. 6A). As shown in FIG. 6, in the present invention, the LED light is transmitted in the diameter direction while being reflected by the upper and lower surfaces under the condition of total reflection inside the glass, and the transmitted light intensity is detected at the opposite end. The detection light intensity is reduced in accordance with the degree of adhesion dirt present. Accordingly, the degree of dirt adhesion can be grasped by detecting the degree of attenuation of the LED light. However, since the output of the LED light depends on the environmental temperature, the temperature compensation is calibrated with a monitoring photodiode.

  In the protective glass contamination detection apparatus of the present invention, the LED is preferably visible light, and the critical angle is 41 °. The critical angle varies depending on the refractive index of the medium, the wavelength of the LED light, and the like, but typically, light having a wavelength of 588 nm (yellow) in an optical glass (protective glass) having a refractive index of 1.52. Can be calculated as 41 ° (see FIG. 6B).

  The protective glass contamination detection apparatus of the present invention is more preferably characterized in that the main wavelength of the LED is between 580 nm and 600 nm, and the emission angle of the LED light from the LED is 30 ° or less. It is also possible to use any wavelength in the visible light range (380 nm to 780 nm). Since the emission angle of LED light from the LED is 30 ° or less, it is expected that the light taken into the protective glass is efficiently totally reflected on the reflection plane without the LED light being scattered in various directions. it can.

  Further, the protective glass contamination detection apparatus of the present invention is more preferably characterized in that the LED pulse is 2000 times / second or more.

  In addition, the protective glass dirt detection device of the present invention is more preferably based on a comparison between the amount of light before the LED light is incident on the protective glass and the amount of detection light detected by the LED light detection unit. It further comprises a determination unit for determining the degree of contamination of the glass.

  Further, the laser processing machine of the present invention is a laser processing machine provided with the above-described protective glass stain detection device, and when the determination unit determines that the degree of contamination of the protective glass is equal to or greater than a predetermined threshold, It is characterized by comprising notifying means for stopping the laser processing operation by the processing machine or notifying the operator.

  The method for detecting dirt on a protective glass according to the present invention is a method for detecting dirt on a protective glass using the dirt detector according to any one of the above items, and the LED light is incident on the protective glass at the LED light incident portion. And the step of detecting the light emitted from the opposite end faces of the protective glass in the LED light detection unit and the comparison of the light intensity between the incident LED light and the emitted LED light And a step of judging the degree of contamination.

  According to the present invention, the detection light from the LED is incident from the outer peripheral surface of the protective glass so as to be totally reflected in the protective glass, and the outgoing light from the opposite end surface is detected, so that highly accurate dirt detection can be safely performed. A glass contamination detection apparatus, a laser processing machine including the glass contamination detection device, and a protection glass contamination detection method can be provided.

(A) is a figure explaining the structure outline | summary of the laser processing system regarding embodiment of this invention, (b) is a block diagram explaining the structure outline | summary of the dirt detection apparatus of protective glass. It is a conceptual diagram explaining scattering of the contaminant in a laser processing machine, and mounting | wearing of protective glass. (A), (b) is a conceptual diagram explaining the critical angle which makes LED light inject with respect to protective glass, and the state of total reflection, (c) is detected when ambient temperature changes. It is a figure explaining the fluctuation | variation before calibration of the emitted LED light, (d) arrange | positions the photoelectric element for correction | amendment (namely, for calibration or / and reference) close to the light source for measurement, and sets the photoelectric element for measurement to the opposing end. It is a figure explaining the state to arrange | position. (A), (b) is a conceptual diagram for explaining that the dirt detection region is a band passing through the diameter between the light source for measurement and the photoelectric element, and FIG. 4 (c) is the sensitivity distribution of the protective glass of φ100 mm. FIG. 4D is a conceptual diagram illustrating a configuration including three pairs of light emitting / receiving units each including a measurement light source, a correction photoelectric element, and a detection photoelectric element. It is a figure explaining the relative output of the detected light intensity with respect to the degree to which dirt adhered to the protective glass of φ100 mm according to the embodiment of the present invention. (A) is a conceptual diagram explaining an incident angle, a reflection angle, a refraction angle, and a critical angle, (b) is a figure explaining the wavelength dependence of the refractive index of glass.

  In the laser processing machine, a protective glass is attached to the front surface of the optical component in order to prevent the optical component such as the objective lens from being damaged. This avoids contamination of the optical components, but if the protective glass is contaminated, the laser light may be attenuated or the protective glass may be damaged due to heat generation. It is an item.

  In the present invention, it is possible to link with production equipment and a laser processing automatic machine (hereinafter simply referred to as an automatic machine) by automating the dirt detection. The laser processing machine includes a laser beam emitting portion called a laser machining head or an emission unit, and has a relatively expensive optical system such as an objective lens in this portion.

  FIG. 1A is a diagram for explaining an outline of the configuration of a laser processing system 1000 according to the embodiment of the present invention. In FIG. 1A, a laser processing system 1000 includes a laser processing machine including a laser processing head 1200 and the like connected to a laser control unit 1600 and an optical fiber 1100.

  As shown in FIG. 1A, the laser processing system 1000 has a configuration in which a workpiece 1400, which is a sample to be laser processed, is automatically and continuously supplied by an automatic machine 1500. The laser processing head 1200 includes a protective glass 1210 between the workpiece 1400 and the laser processing head 1200.

  Further, the protective glass 1210 protects the optical system in the laser processing head 1200 from contamination such as fumes accompanying processing such as cutting and welding of the workpiece 1400. The laser processing system 1000 also includes a protective glass contamination detection device 1300 that detects the degree of contamination of the protective glass 1210.

  FIG. 1B is a block diagram for explaining an outline of the configuration of the protective glass contamination detection apparatus 1300. In FIG. 1B, the dirt detection light source LED 1315 has its measurement frequency adjusted every minute or every 30 seconds by the measurement signal adjustment unit 1330, and a measurement period of 0.5 seconds or the like by the pulse modulation unit 1320. During this period, the LED driver 1310 instructed with 1000 pulses or the like emits light with a predetermined pulse modulation at a predetermined frequency.

  The emission intensity of the dirt detection light source LED 1315 is monitored by the reference measurement photoelectric element 1390 (1). Based on this, the controller 1360 calibrates the detection light intensity of the detection photoelectric element 1390 (2) disposed at the opposite end of the protective glass 1210. The output values of the reference measurement photoelectric element 1390 (1) and the detection photoelectric element 1390 (2) are demodulated from preamplifiers 1370 (1) and 1370 (2) and demodulation circuits 1380 (1) and 1380 ( 2) to be input to the controller 1360 for computation and processing.

  In addition, the display unit 1340 can display a degree of contamination of the protective glass 1210 calibrated and calculated by the controller 1360, a warning or a caution based on the degree of contamination, and the like. Further, when the degree of contamination of the protective glass 1210 becomes a predetermined condition, a signal for stopping the automatic machine 1500 or the like may be sent via the external IF 1350. As a result, it is possible to reliably avoid laser processing in a contaminated state, so that the yield is improved and the cost is reduced.

  Here, when performing laser processing, contaminants called spatter, fume and the like are scattered from the material to be processed (sample to be processed or workpiece) during processing, so that these optical components are damaged by the scattered material. There are concerns.

  As described above, in order to prevent damage to equipment and equipment (particularly optical components) related to laser processing machines, a protective glass is generally attached to the front surface of the optical component, and the protection glass is in accordance with the contamination status of the protective glass. Maintenance work is performed to replace the protective glass as appropriate. FIG. 2 is a conceptual diagram illustrating the scattering of contaminants and the wearing of protective glass in a laser processing machine.

  Although the protective glass can protect the optical system such as the objective lens for the time being, if the contamination of the protective glass progresses, the laser beam is prevented from being emitted and the processing energy is attenuated, or the contamination is significant. May cause damage to the protective glass due to the heat generated by the contaminated material absorbing the laser beam.

  Therefore, checking the degree of contamination of the protective glass is an important daily maintenance / inspection / maintenance item for the operation of the laser processing machine, but the operator still visually detects the contamination of the protective glass. In general, an automated system for detecting dirt is not widespread.

  It is an object of the present invention to further improve the efficiency of a laser processing production line by enabling the linkage with production equipment and automatic machines by automating dirt detection. Specifically, in the present invention, the protective glass is regarded as an optical waveguide, an LED is used as a dirt measurement light source incident on the optical waveguide, and the LED light incident at a desired angle from the end face of the protective glass is reflected inside the protective glass. It is configured to totally reflect.

  On the other hand, a photoelectric element such as a photodiode is arranged on the opposite end face located on the opposite side of the end face on which the LED light is incident, and the LED light that has progressed in the diameter direction while reflecting in the protective glass in the thickness direction. The output light is obtained.

  FIGS. 3A and 3B are conceptual diagrams for explaining a state in which LED light is incident on the protective glass from the end face at 70 ° and totally reflected inside, and FIG. 3C shows the surrounding environment. FIG. 3D is a diagram for explaining the pre-calibration fluctuation of the emitted LED light detected when the temperature changes, and FIG. 3D shows a correction photoelectric element (that is, calibration or / and reference) as a measurement light source. It is a figure explaining the state which arrange | positions closely and arrange | positions the photoelectric element for a measurement to an opposing end.

  In FIG. 3, if the surface of the protective glass functioning as a waveguide is in a clean state, the incident angle to the upper and lower surfaces of the protective glass is greater than the critical angle and less than 90 degrees as described above. The light is confined in the protective glass (without light being emitted from the upper and lower surfaces of the glass) and can be detected with high light intensity from the exit end face facing the light incident part while proceeding in the diameter direction with total reflection. .

  As shown in FIG. 3B, if a contaminant is attached to the surface of the protective glass, the evanescent light that has oozed out from the contaminated portion onto the surface of the protective glass is disturbed and dissipated as propagating light to the outside. The light intensity detected at 1 will decrease. This degree of light intensity change (decrease degree) can be grasped as the degree of contamination of the protective glass.

  Here, the LED as the measurement light source generates light that is pulse-modulated (for example, 1000 times / 0.5 seconds per measurement), and further detects the signal from the photoelectric element after receiving light. By measuring, the influence of the disturbance by the environmental light (typically 50-60 Hz illumination lamp etc.) in which the laser processing machine is installed shall be avoided.

  In FIG. 3 (c), the luminous efficiency of the LED generally has a high temperature dependency, so whether the detected change in the measurement light is caused by contamination of the protective glass or the change in the ambient temperature. There is concern that it may become unclear whether it is a thing.

  For this reason, as shown in FIG. 3 (d), the light of the LED, which is the light source, is measured by the photoelectric element even before entering the protective glass, and using this as a reference, the ratio of the light source to the light to be measured is calculated, The degree of fouling of the protective glass shall be judged from the degree of decrease in the ratio. Further, based on the reference, the detected emitted light intensity may be temperature-corrected as appropriate, and the degree of fouling of the protective glass may be determined based on the temporal change of the temperature-corrected emitted light intensity.

  In the present invention, an LED light source (preferably an emission angle of 20 to 30 ° or less) that is relatively focused by a lens effect such as a mold resin is used, and reflected light by total internal reflection in glass is used instead of scattered light. Even when the size of the protective glass is increased, the measuring light easily reaches the opposing end surfaces with high light intensity.

  As a result of such characteristics, the present invention can be applied to dirt detection of a large-diameter protective glass that is attached to an objective lens (fθ lens) of a galvano scanner type welding head, which has been difficult in the past. In addition, because of the detection method based on total reflection of focused LED light, the detection area where dirt can be detected has a relatively thin band-like distribution passing through the diameter of the protective glass, but by using a plurality of combinations of LED light sources and photoelectric elements. , The detection area can be expanded.

  4 (a) and 4 (b) are conceptual diagrams for explaining that the dirt detection region has a band shape passing through the diameter between the light source for measurement and the photoelectric element, and FIG. 4 (c) is a diagram of protective glass having a diameter of 100 mm. FIG. 4D is a conceptual diagram illustrating a configuration including three pairs of light emitting and receiving units each including a measurement light source, a correction photoelectric element, and a detection photoelectric element. .

  In addition to the high detection light intensity level of the measurement light by the optical waveguide method using the protective glass as a waveguide, the measurement with pulse-modulated light makes it less susceptible to disturbances and extremely reliable contamination. Detection is possible.

  Similarly, since the dynamic range of stain measurement is wide, it is possible to display not only the presence / absence of contamination but also the degree of contamination in stages, which is useful for predicting the replacement time of protective glass. Become.

  FIG. 5 is a diagram for explaining the relative output of the detected light intensity with respect to the degree of contamination on the φ100 mm protective glass according to the embodiment of the present invention. FIG. 5 shows changes in the output of the photoelectric element when ink drops are dropped on the protective glass one by one, the horizontal axis indicates the number of ink drops dropped, and the vertical axis indicates the relative detection light intensity. Note that the ink was measured by dropping linearly at intervals of 10 mm on the optical path (on the strip-shaped stain detection area).

  As can be understood from FIG. 5, the detected light intensity decreases as the number of drops increases, that is, the contamination of the protective glass increases, and the degree of contamination of the protective glass can be accurately grasped from the correlation. Is possible. Therefore, for example, when the detected light intensity drops from 80% to 80%, the operator is warned or notified, the conveyance of the workpiece by the automatic machine is stopped, and the laser oscillation itself is stopped. It is also possible to do.

  The protective glass contamination detection device of the present invention is a protective glass contamination detection device that detects the contamination of the protective glass mounted on the laser processing head of the laser processing machine. LED light is applied to the protective glass within the protective glass. The LED light incident part which makes LED light enter so that it may totally reflect, and the LED light detection part arrange | positioned at the end surface facing the LED light incident part of a protective glass, It is characterized by the above-mentioned.

  Further, without removing the workpiece, the laser processing idle time (for example, during the workpiece replacement time or before the start of processing for each sample to be processed) is used for a very short time (for example, 0.5 seconds). With this, you can safely detect dirt on the protective glass. Moreover, since it becomes possible to detect the emitted light containing the information on the degree of contamination on the upper surface or the lower surface of the protective glass with high light intensity, highly accurate contamination detection is possible. For example, when the protective glass has a disk shape having a predetermined thickness, the LED light incident part and the LED light detection part are arranged at opposing positions passing through the disk-shaped diameter. Thereby, it is possible to detect not the evanescent light, the scattered light, or the light propagating to the outside, but the strong light transmitted through the protective glass while reflecting on the upper and lower surfaces along the diameter under the total reflection condition.

  The protective glass contamination detection device of the present invention preferably further includes a display unit for displaying a ratio of the amount of detection light detected by the LED light detection unit to the amount of light before the LED light is incident on the protective glass. It is characterized by providing.

  For this reason, a photodiode for monitoring the amount of incident light for measuring the amount of LED light before incidence can be provided around the LED. In reality, since incident light is incident on the protective glass, it is impossible to directly measure the total amount of light in real time. However, it is possible to estimate and convert the incident light amount by providing an incident light amount monitoring photodiode.

  Records and stores the ratio between the measured value of the incident light intensity monitoring photodiode and the measured value of the detected light detected by the LED light detection unit when the protective glass is not dirty (immediately after replacement with a new one). If this is done, the ratio decreases with the progress of dirt on the protective glass, so the degree of dirt can be determined.

  In addition, LEDs are known to have significantly different luminous efficiencies and luminous intensities depending on the environmental temperature, but as described above, the degree of contamination is determined by the relative ratio of incident light and outgoing light, so the temperature characteristics of the LEDs It is possible to grasp the degree of contamination relatively accurately and objectively without being affected by fluctuations.

  The protective glass contamination detection apparatus of the present invention is more preferably characterized in that the incident angle of the LED light to the reflection plane in the protective glass is more than the critical angle and less than 90 °.

  This avoids LED light incident from, for example, the end surface of the protective glass circumferential portion being emitted from the opposite end without being linearly penetrating the protective glass and being reflected on the upper and lower surfaces. The reflected light reflected on the upper and lower surfaces can be detected at least once. Since the LED light passes through the protective glass while reflecting as if it were an optical waveguide, the emitted light at the opposite end includes at least information on the degree of contamination of the reflected portion. By adjusting the angle of the incident LED light so that it is totally reflected by the upper and lower surfaces inside the protective glass, the detection light at the opposite end is not too strong, and it is detected as light of appropriate intensity containing appropriate information for detection. It will be possible. By making the number of times the LED light is reflected within the protective glass as much as possible, more information on the degree of contamination can be included. In order to maximize the number of times the LED light is reflected inside the glass, it is preferable that the angle of light incident on the upper and lower reflective surfaces inside the glass be close to the critical angle. If the angle is smaller than the critical angle, LED light is emitted from the upper and lower surfaces of the glass and dissipated, and the light intensity measured by the light detection unit becomes extremely weak.

  Further, in the protective glass contamination detection apparatus of the present invention, the LED light is preferably pulsed light of visible light, and the incident angle to the reflection plane in the protective glass is an angle exceeding the critical angle. To do. As illustrated in FIG. 6, the incident angle of the LED light from the outside of the protective glass is such that the incident angle to the reflection plane inside the medium (protective glass) is as small as possible exceeding a critical angle (for example, 41 °). Can be adjusted and set. Here, the incident angle of the LED light to the protective glass (that is, the direction of the LED with respect to the glass) will be described. For example, when the light is incident from the end surface, the shape of the end surface, the layer presence / absence of coating, etc. It is generally known that the refractive characteristics at the time of glass incidence differ greatly depending on the refractive index of the glass. In the present invention, the LED light for measurement traveling in the glass is totally reflected at the upper and lower surfaces inside the glass, preferably many times, but in view of the above refraction characteristics, the incident angle of the LED light to the protective glass It is assumed that the LED light is incident on the glass so as to have total reflection characteristics inside the glass without being specified by (that is, the direction of the LED with respect to the glass). For example, in the case of total reflection, the detected light intensity is maximized (or maximized) within a certain range, so that the detected light intensity does not become weak while finely adjusting the direction of the LED. In addition, the direction of the LED can be adjusted so that the inside of the glass is reflected many times.

  That is, by making the LED light incident from the protective glass end face or the like so as to satisfy the predetermined condition described above, the LED light reflected at least once on the upper surface or the lower surface at the opposite end can be obtained under a good S / N ratio. It can be detected. For example, when LED light is incident on the glass at an incident angle of 0 ° to the protective glass, the LED light that is linearly transmitted through the protective glass without being reflected once by the upper or lower surface of the protective glass has a strong intensity. Since the light is emitted from the opposite end, it is not appropriate for the dirt detection.

  The protective glass contamination detection apparatus of the present invention is more preferably characterized in that the main wavelength of the LED is between 580 nm and 600 nm, and the light emission angle of the LED is 30 ° or less.

  The LED itself has a resin mold having a lens function, and a light emission angle is defined as one of the characteristics of the LED. In the present invention, in order to allow the LED to efficiently enter the protective glass at a predetermined incident angle that satisfies the internal total reflection condition, the light emission angle of the LED is preferably 20 ° to 30 °. It shall be. In an LED that emits light at a wide angle too broadly, the reflection efficiency inside the glass is deteriorated and the detected light to be detected is weak.

  The wavelength of the LED is preferably about yellow to orange, and is preferably an LED mainly having an emission wavelength in a wavelength range of about 580 nm to 600 nm. In the confirmation experiment of the present inventor, the measurement by the wavelength region has a result that a good light measurement intensity can be obtained as compared with other wavelength regions.

  Further, the protective glass contamination detection apparatus of the present invention is more preferably characterized in that the LED pulse is 2000 times / second or more.

  The light emission pulse of the LED is preferably separated as much as possible from a period of about 50 to 60 Hz, which exists in a large amount in the surrounding environment. Preferably, when the measurement time of one time is 0.5 seconds, for example, it is preferable to use pulsed light that blinks about 1000 times or more during this 0.5 second. Thereby, it is possible to reduce the influence of noise signals (for example, various illuminations) in the surrounding environment and to measure and judge the degree of contamination with high accuracy.

  In addition, the protective glass dirt detection device of the present invention is more preferably based on a comparison between the amount of light before the LED light is incident on the protective glass and the amount of detection light detected by the LED light detection unit. It further comprises a determination unit for determining the degree of contamination of the glass.

  As a result, the determination unit can automatically determine the degree of contamination without the operator making a direct determination based on the measurement data. Judgment is possible. For this reason, the photoelectric element for the emitted light intensity monitor which estimates the LED light quantity before incidence, and the photoelectric element which measures the light quantity of detection light can be provided.

  Further, the laser processing machine of the present invention is a laser processing machine provided with the above-described protective glass stain detection device, and when the determination unit determines that the degree of contamination of the protective glass is equal to or greater than a predetermined threshold, It is characterized by comprising notifying means for stopping the laser processing operation by the processing machine or notifying the operator. The notification may be an alarm sound, an alert display on the display unit, or a combination thereof, and any notification method can be used.

  As a result, it is possible to eliminate quality degradation factors such as laser processing performed while the protective glass remains dirty due to an operator's judgment error, etc., so that stable and high-quality laser processing is always performed. It becomes possible. For example, the operator who has received the notification can make the protective glass free from dirt depending on whether the protective glass is replaced or cleaned.

  The method for detecting dirt on a protective glass according to the present invention is a method for detecting dirt on a protective glass using the dirt detector according to any one of the above items, and the LED light is incident on the protective glass at the LED light incident portion. And the step of detecting the light emitted from the opposite end faces of the protective glass in the LED light detection unit and the comparison of the light intensity between the incident LED light and the emitted LED light And a step of judging the degree of contamination.

  This makes it possible to use a laser processing idle time (for example, during the workpiece replacement time or before the start of processing for each sample to be processed) for a very short time (for example, 0.5 seconds or the like) without removing the workpiece. ), It is possible to provide a method for detecting the contamination of the protective glass, which can safely detect the contamination of the protective glass. In addition, since it is possible to detect the emitted light including information on the degree of contamination of the upper surface or the lower surface of the protective glass with a high light intensity, it is possible to provide a method for detecting the contamination of the protective glass that enables highly accurate contamination detection.

  Since the present invention can automate the inspection of dirt on the protective glass and can be linked to an automatic machine, the downtime of the laser processing machine due to maintenance and inspection work is minimized, the operating rate is improved, and troubles due to contamination are prevented. It is also useful for prevention.

  Further, the present invention does not require a system such as a CCD camera or image processing, and can be realized with a relatively simple and inexpensive configuration, so that it can be miniaturized. It is also suitable for introduction.

  In addition, the present invention does not newly provide an element that interferes with the optical path of the processing laser beam for detecting the contamination of the protective glass. Therefore, during actual laser processing, the protective glass is contaminated in parallel with this. It is also possible to detect.

  The method for detecting contamination on the protective glass of the laser processing machine of the present invention is not limited to the configuration and method in the description of the present embodiment described above, and can be freely selected within the scope of the present invention and within the scope obvious to those skilled in the art. Can be changed, modified, and arranged. In addition, it can be used in combination with conventionally known apparatus configurations and methods as appropriate, and in appropriate order.

  The present invention can be widely applied to laser processing machines and systems.

  1000 ... Laser processing system, 1100 ... Optical fiber, 1200 ... Laser processing head, 1210 ... Protective glass, 1300 ... Protective glass contamination detector, 1400 ... Work, 1500 ... Automatic machine, 1600 ... Laser control unit.

Claims (9)

In the protective glass contamination detection device that detects the contamination of the protective glass mounted on the laser processing head of the laser processing machine,
An LED light incident part that makes the LED light incident on the protective glass so that the LED light is totally reflected in the protective glass; and
An LED light detection unit disposed on an end surface of the protective glass facing the LED light incident unit. In the protective glass dirt detection device according to claim 1,
A protective glass contamination detecting device, further comprising a display unit that displays a ratio of a light amount of the detection light detected by the LED light detection unit to a light amount of the LED light before entering the protective glass. . In the dirt detection device according to claim 1 or 2,
An incident angle of the LED light to the reflection plane in the protective glass is less than 90 ° exceeding a critical angle. In the dirt detection device according to claim 3,
The LED light is visible light pulse light. In the dirt detection device according to claim 4,
The main wavelength of the LED light is between 580 nm and 600 nm, and the light emission angle of the LED light from the LED is 30 ° or less. In the dirt detection device according to claim 4 or 5,
The LED light pulse is 2000 times / second or more. In the dirt detection device according to any one of claims 1 to 6,
The apparatus further includes a determination unit that determines the degree of contamination of the protective glass based on a comparison between the light amount of the LED light before entering the protective glass and the light amount of the detection light detected by the LED light detection unit. Protective glass contamination detector characterized by the above. In a laser processing machine comprising the protective glass contamination detection device according to claim 7,
When the determination unit determines that the degree of contamination of the protective glass is equal to or greater than a predetermined threshold value, the determination unit includes a notification unit that stops the laser processing operation by the laser processing machine or notifies the operator. Laser processing machine. In the dirt detection method of the protection glass using the dirt detector according to any one of claims 1 to 7,
In the LED light incident part, the step of causing the LED light to enter the protective glass;
In the LED light detection unit, detecting light emitted from the opposite end surfaces of the protective glass;
And a step of determining the degree of contamination of the protective glass based on a comparison of light intensity between the incident LED light and the emitted LED light.