JPWO2016181489A1 - Laser equipment - Google Patents

Abstract

The first transistor and the second transistor constitute a differential pair. The light receiving element receives a part of the light of the laser light emitting element. The converter converts the output of the light receiving element into a voltage proportional to the output of the laser light emitting element. The comparator compares the voltage converted by the converter with the abnormal voltage and applies the first voltage to the base of the first transistor as an output. The output control unit controls the current source in order to constantly control the light output of the laser light emitting element based on the voltage converted by the converter. A second voltage is applied to the base of the second transistor, and a current that distributes the current of the current source according to the difference between the first voltage and the second voltage flows through the first transistor and the second transistor. The first voltage is lowered when the voltage converted by the converter exceeds the abnormal voltage.

Description

  The present invention relates to a laser apparatus provided with a mechanism for safely blocking abnormal output.

  In order to prevent a user from being damaged by a laser product, a “laser product safety standard” JIS C6802 is defined based on the International Electrical Standard (IEC). This international electrical standard classifies laser products according to the degree of risk and requires that the class be guaranteed even in a single failure condition.

  The laser pointer described in Patent Document 1 detects that the monitor output has fallen below a predetermined value in order to suppress abnormal output when the monitor output used for feedback decreases in constant output control. Application of power supply voltage to is interrupted. However, when the optical output is varied and used, it is difficult to determine the lower limit value of the monitor output.

  Patent Document 2 is known as a method for solving this problem. The laser beam generator described in Patent Document 2 controls the output to be constant and includes two abnormal light amount detectors, and one of the two abnormal light amount detectors has a light amount of a predetermined level or more. Detecting the power supply voltage to the laser diode is interrupted. Thereby, only the abnormality when the laser output increases can be detected.

JP-A-7-235694 JP 2006-186168 A

  However, Patent Document 1 and Patent Document 2 have the following problems. In other words, in order to maintain a predetermined laser class at the time of a single failure, it is necessary to stop the laser output before reaching the exposure emission limit (AEL) of each class or reduce it to an allowable level or less.

  At this time, the allowable emission duration of the laser output depends on the laser diode class, wavelength, and transient output at the time of a single failure. In the case of class 1 that does not affect the human body, a cut-off speed of several μs or less may be required.

  However, in an application that is careful about the characteristics and noise characteristics of the laser diode, the power source and the laser drive unit are generally separated by a plurality of decoupling capacitors. As in Patent Documents 1 and 2, in the method of cutting off the application of voltage to the laser diode, there is a possibility that a transient current from a capacitor bank constituted by a plurality of decoupling capacitors may continue even after the power is turned off.

  If a 1 μF capacitor charged to 10 V discharges 1 V during 1 μs, a current of 1 A flows transiently. When the laser output is sustained by this current, it deviates from a predetermined laser class. In some cases, the human body may be affected.

  An object of the present invention is to provide a laser device that can shut off abnormal output at high speed even under a single failure condition and can guarantee a predetermined laser class.

  In order to solve the above problems, a laser device according to the present invention includes a first transistor and a second transistor that form a differential pair, a laser light emitting element connected to a collector electrode of the first transistor, and the first transistor. A current source connected to emitter electrodes of one transistor and the second transistor; a light receiving element that receives a part of the light of the laser light emitting element; and a voltage in which an output of the light receiving element is proportional to an output of the laser light emitting element A converter that converts the voltage converted by the converter to an abnormal voltage and applies a first voltage to the base electrode of the first transistor as an output, and the converter converts the voltage An output control unit for controlling the current source to control the light output of the laser light emitting element based on the voltage, and a second voltage is applied to the base electrode of the second transistor. Applied to the first transistor and the second transistor is a current that distributes the current of the current source according to a difference between the first voltage and the second voltage, and the comparator converts the current by the converter. When the applied voltage exceeds the abnormal voltage, the first voltage is lowered to cut off the current flowing through the laser light emitting element.

  According to the present invention, the interruption of abnormal output is controlled by switching the current of the differential pair of the first transistor and the second transistor. For this reason, abnormal discharge from the capacitor bank does not occur, and the current is switched with a slight differential voltage, so that the current can be interrupted at high speed. Therefore, even in a single failure condition, abnormal output can be shut off at high speed, and a predetermined laser class can be guaranteed.

FIG. 1 is a diagram showing a configuration of a laser apparatus according to the first embodiment of the present invention. FIG. 2 is a diagram showing the relationship between the differential input voltage and the emitter current of the differential pair formed of the first and second transistors provided in the laser apparatus according to the first embodiment of the present invention. FIG. 3 is a diagram showing a configuration of a laser apparatus according to the second embodiment of the present invention. FIG. 4 is a diagram showing a configuration of a laser apparatus according to the third embodiment of the present invention.

(First embodiment)
FIG. 1 is a diagram showing a configuration of a laser apparatus according to the first embodiment of the present invention. The laser apparatus according to the first embodiment shuts off the abnormal output of the laser diode LD shown in FIG. 1 at high speed and ensures a predetermined laser class of the laser diode LD.

  The laser device includes a laser diode LD, a power supply VLD, transistors Q1 and Q2, resistors R1 to R4, a current source 11, a photodiode PD, an IV converter 6, a comparator 7, a level converter 8, an auto power controller (APC). ) 9.

  The power source VLD is connected to the anode of the laser diode LD, and the collector electrode of the bipolar transistor Q1 is connected to the cathode of the laser diode LD via the resistor R1.

  The collector electrode of the bipolar transistor Q2 is connected to the power supply VLD via a resistor R2. The transistor Q1 and the transistor Q2 constitute a differential pair, and the emitter electrode of the transistor Q1 and the emitter electrode of the transistor Q2 are connected to a current source 11 that supplies a constant current.

  One end of the resistor R3 and the output terminal of the level converter 8 are connected to the base electrode of the transistor Q1, and the voltage V1 is applied. One end of a resistor R4 is connected to the base electrode of the transistor Q2, and a voltage V2 is applied.

  The laser diode LD corresponds to the laser light emitting element of the present invention, and generally the laser output increases or decreases in proportion to the drive current.

  The photodiode PD corresponds to the light receiving element of the present invention, and detects a part of the laser light of the laser diode LD. The IV converter 6 converts the output current detected by the laser diode LD into a voltage proportional to the output current of the laser diode LD, and outputs the voltage to the comparator 7 and the APC 9.

  The comparator 7 compares the converted voltage from the I-V converter 6 with an abnormal voltage corresponding to the abnormal output of the laser diode LD. If the converted voltage is equal to or lower than the abnormal voltage, the comparator 7 is at the H level (for example, 5V). Is output to the level converter 8, and when the converted voltage exceeds the abnormal voltage, the L level (for example, 0 V) is output to the level converter 8. The level converter 8 converts the output voltage from the comparator 7 into a predetermined voltage V1 and outputs the voltage V1 to the base electrode of the transistor Q1.

  The APC 9 corresponds to the output control unit of the present invention and performs constant output control. The APC 9 controls the optical output of the laser diode LD based on the conversion voltage from the IV converter 6 and the reference voltage Vref. In addition, the current Iop of the current source 11 that is a control amount is generated and controlled.

  The current Iop of the current source 11 is the total current of the emitter current of the transistor Q1 and the emitter current of the transistor Q2.

  Next, the operation of the laser apparatus according to the first embodiment configured as described above will be described. First, a case where the transistor Q1 is turned on, the transistor Q2 is turned off, and the output of the photodiode PD is not an abnormal output will be described.

  In this case, the comparator 7 compares the conversion voltage from the IV converter 6 with the abnormal voltage corresponding to the abnormal output of the laser diode LD, and the conversion voltage is equal to or lower than the abnormal voltage. The signal is output to the base electrode of the transistor Q1 through the device 8. Therefore, the transistor Q1 continues to be turned on and the transistor Q2 continues to be turned off.

  Since the bipolar transistors Q1 and Q2 are configured as a differential pair, the emitter currents IE1 and IE2 of the transistors Q1 and Q2 are as shown in FIG. 2 with respect to the differential input voltage (V1-V2). Change. That is, a current obtained by distributing the current Iop of the current source 11 according to the differential input voltage (V1-V2) flows through the emitters of the transistors Q1 and Q2. The differential input voltage (V1-V2) is 120 mV, and about 99% of the current Iop of the current source 11 flows to the transistor Q1 side (emitter current E1 in FIG. 2). Therefore, from the viewpoint of reducing current consumption that does not contribute to light emission, it is desirable that the differential input voltage (V1-V2) is larger than 120 mV when the laser diode LD is turned on.

  Next, a case where the output of the photodiode PD becomes an abnormal output will be described. Here, when the voltage input from the IV converter 6 to the APC 9 decreases due to a single failure of the circuit, the voltage from the IV converter 6 becomes less than the reference voltage Vref. The current Iop of the current source 11 that is the control amount is increased.

  For this reason, the current flowing through the laser diode LD increases. The comparator 7 compares the converted voltage from the IV converter 6 with the abnormal voltage corresponding to the abnormal output of the laser diode LD. Since the converted voltage exceeds the abnormal voltage, the comparator 7 outputs the L level (for example, 0 V) to the base electrode of the transistor Q1 via the level converter 8.

  For this reason, the base electrode of the transistor Q1 changes to L level, and the transistor Q1 is turned off. At this time, if the differential input voltage (V1−V2) becomes smaller than −120 mV, about 99% of the current Iop of the current source 11 flows from FIG. 2 to the transistor Q2 side (emitter current E2 in FIG. 2). ), The laser diode LD is turned off.

  At this time, for example, when the output voltage of the level converter 8 is adjusted so that the differential input voltage (V1−V2) when the laser diode LD is turned on becomes 120 mV, the laser diode only changes by −240 mV. The current IE1 flowing to the transistor Q1 side can be lowered to a level at which the LD does not light up. Further, the current flowing through the laser diode LD can be cut off. For this reason, abnormal output can be shut off at high speed.

  As described above, according to the laser device of the first embodiment, the abnormal output is controlled by switching the current of the differential pair of the transistor Q1 and the transistor Q2. For this reason, abnormal discharge from the capacitor bank does not occur, and the current is switched with a slight differential voltage, so that the current can be interrupted at high speed. Therefore, even in a single failure condition, abnormal output can be shut off at high speed, and a predetermined laser class can be guaranteed.

(Second Embodiment)
FIG. 3 is a diagram showing a configuration of a laser apparatus according to the second embodiment of the present invention. FIG. 3 shows a laser device according to the second embodiment of the present invention, in which a level converter AND8a is provided instead of the level converter 8 of the laser device according to the first embodiment shown in FIG. To do.

  The level converter AND8a takes the AND of the output from the comparator 7 and the voltage signal Vin from the outside, and applies the AND output to the base electrode of the transistor Q1. That is, on / off of the laser diode LD can be controlled by the voltage level of the external voltage signal Vin. When the laser diode LD is turned on, the abnormal output can be shut off at high speed by the laser device according to the first embodiment shown in FIG.

(Third embodiment)
FIG. 4 is a diagram showing a configuration of a laser apparatus according to the third embodiment of the present invention. The laser apparatus according to the third embodiment shown in FIG. 4 is characterized in that an auto current control (ACC) 9 is provided instead of the APC 8 of the laser apparatus according to the second embodiment shown in FIG.

  The ACC 9 corresponds to the current control unit of the present invention and performs constant current control, and performs control so that the current flowing through the current source 11 is constant. The level converter AND8a takes the AND of the output from the comparator 7 and the voltage signal Vin from the outside, and applies the AND output to the base electrode of the transistor Q1. That is, on / off of the current flowing through the laser diode LD can be controlled at high speed according to the voltage level of the external voltage signal Vin. For this reason, it is used at the time of digital modulation of the laser diode LD.

  Further, when the response speed of the IV converter 6 is approximately the same as the modulation speed of the laser diode LD, for each on-time optical output, the same configuration as the embodiment of FIGS. Abnormal output can be shut off at high speed.

  Even when the modulation speed of the laser diode LD is equal to or higher than the response speed of the IV converter 6, the abnormal output level is determined in consideration of the voltage value filtered within the response speed of the IV converter 6. Can do. Thereby, abnormal output can be shut off at high speed.

  The present invention can be applied to a laser apparatus that satisfies a single failure requirement that complies with the safety standards of laser products, and is particularly applicable to a laser processing apparatus, a laser illumination apparatus, and the like.

Claims (3)

A first transistor and a second transistor constituting a differential pair;
A laser emitting element connected to the collector electrode of the first transistor;
A current source connected to emitter electrodes of the first transistor and the second transistor;
A light receiving element that receives a part of the light of the laser light emitting element;
A converter that converts the output of the light receiving element into a voltage proportional to the output of the laser light emitting element;
A comparator that compares the voltage converted by the converter with an abnormal voltage and applies the first voltage to the base electrode of the first transistor as an output;
An output control unit for controlling the current source in order to constantly control the light output of the laser light emitting element based on the voltage converted by the converter;
A second voltage is applied to a base electrode of the second transistor, and a current obtained by distributing a current of the current source to the first transistor and the second transistor according to a difference between the first voltage and the second voltage. When the voltage converted by the converter exceeds the abnormal voltage, the comparator reduces the first voltage and cuts off the current flowing through the laser light emitting element. A first transistor and a second transistor constituting a differential pair;
A laser emitting element connected to the collector electrode of the first transistor;
A current source connected to emitter electrodes of the first transistor and the second transistor;
A light receiving element that receives a part of the light of the laser light emitting element;
A converter that converts the output of the light receiving element into a voltage proportional to the output of the laser light emitting element;
A comparator that compares the voltage converted by the converter with an abnormal voltage and applies the first voltage to the base electrode of the first transistor as an output;
A current control unit for controlling a current flowing through the current source to be constant,
A second voltage is applied to a base electrode of the second transistor, and a current obtained by distributing a current of the current source to the first transistor and the second transistor according to a difference between the first voltage and the second voltage. When the voltage converted by the converter exceeds the abnormal voltage, the comparator reduces the first voltage and cuts off the current flowing through the laser light emitting element. The voltage from the comparator is converted to the first voltage, which is a predetermined voltage, and the AND of the converted first voltage and an external voltage signal is taken, and the AND output is the base electrode of the first transistor The laser device according to claim 1, further comprising a level converter for applying to the laser.

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