JP2021153050A - Failure determination device for light emitting element and failure determination method for light emitting device and light emitting element - Google Patents

Abstract

To determine a plurality of states as a failure state of a light emitting element.SOLUTION: A failure determination device for a light emitting element includes a current control unit for controlling a drive current to be supplied to the light emitting element, a voltage measuring unit for measuring a voltage to be applied to the light emitting element to be driven with the supplied drive current, and a determination unit for determining a failure state of the light emitting element based on a voltage difference between a plurality of determination voltages determined from the drive current and a voltage measured by the voltage measurement unit. A short-circuit state, an open state, and an output reduction state are determined as the failure states of the light emitting element.SELECTED DRAWING: Figure 1

Description

The present invention relates to a failure determination device for a light emitting element, a light emitting device, and a failure determination method for the light emitting element.

Patent Documents 1 and 2 disclose techniques for detecting defects in light emitting elements. The laser device disclosed in Patent Document 1 detects a drive current supplied to the laser diode, a drive voltage applied to the laser diode, a light emitting amount of the laser diode, and a temperature in the vicinity of the laser diode. In addition, this laser device has current command value and normal drive current characteristics, current command value and normal drive voltage characteristics, current command value and normal light intensity characteristics, current command value and laser. The characteristics of the normal temperature difference before and after irradiation are stored as a table. Then, the laser device deviates from the predetermined range for each of the detected drive current, drive voltage, light amount, and temperature difference from the values obtained based on the current command value output from the stored table. If so, it is determined that the laser diode is abnormal.

The headlamp device disclosed in Patent Document 2 has a diode module in which a plurality of LEDs are connected in series. This headlamp device detects the voltage applied to the LED, and considers it abnormal when the voltage drop drops below a predetermined threshold value.

Japanese Unexamined Patent Publication No. 2005-85871 Japanese Unexamined Patent Publication No. 2009-280157

The light emitting element fails due to, for example, a surge voltage. In this case, as the mode of failure of the light emitting element, for example, when the light emitting element is a laser diode, a short circuit state in which the anode and the cathode are short-circuited, an open state in which the anode and the cathode are open (open), and the output light There is an output reduction state in which the strength of the laser is reduced. In the output low state, the difference between the detected light intensity and the normal light intensity deviates from the predetermined range, but the difference between the detected drive voltage and the normal drive voltage does not deviate from the predetermined range. In some cases.

In such a state of output decrease, in the laser apparatus disclosed in Patent Document 1, all of the detected drive current, drive voltage, light intensity, and temperature difference deviate from the predetermined range with respect to the normal values. Since there is no such thing, it cannot be judged as abnormal. Further, in this laser device, the open state and the short-circuit state are not distinguished, only the occurrence of an abnormality is determined, and the failure state cannot be detected.

In the headlamp device disclosed in Patent Document 2, when the voltage drop drops below a predetermined threshold value, it is regarded as abnormal, and the open state cannot be detected. Further, in the case of the headlamp device disclosed in Patent Document 2, since there is a voltage drop in the short-circuit state and the output reduction state, an abnormality can be detected in either state, but in which state. I can't judge.

The present invention has been made in view of the above, and an object of the present invention is to provide a technique for determining a plurality of states as a state of failure of a light emitting element.

In order to solve the above-mentioned problems and achieve the object, the failure determination device for the light emitting element according to one aspect of the present invention includes a current control unit that controls the drive current supplied to the light emitting element and the driven drive that is supplied. The light emitting element is based on a voltage difference between a voltage measuring unit that measures a voltage applied to the light emitting element driven by an electric current, a plurality of determination voltages determined from the driving current, and a voltage measured by the voltage measuring unit. It is characterized by including a determination unit for determining the state of failure of the above.

The failure determination device for a light emitting element according to one aspect of the present invention is characterized in that the determination unit determines a plurality of states including a state in which the intensity of light output by the light emitting element is lower than that in the normal state.

In the failure determination device for the light emitting element according to one aspect of the present invention, the determination unit has a short circuit failure and an open failure based on the voltage difference, and an output in which the intensity of the light output by the light emitting element is lower than that in the normal state. It is characterized in that a failure is determined.

The failure determination device for the light emitting element according to one aspect of the present invention determines that a short circuit failure occurs when the voltage measured by the voltage measuring unit is smaller than the short circuit threshold determined by the drive current, and the voltage measured by the voltage measuring unit. Is larger than the open circuit threshold determined by the drive current, it is determined to be an open circuit failure, and when the voltage measured by the voltage measuring unit is within the output failure range determined by the drive current, it is determined to be an output failure. do.

The failure determination device for a light emitting element according to one aspect of the present invention has a light measuring unit for measuring the intensity of light output by the light emitting element, and the determination unit has the intensity measured by the light measuring unit. When the drive current is supplied and is equal to or less than a predetermined intensity threshold value lower than the normal light intensity output by the light emitting element, the state of failure of the light emitting element is determined.

In the failure determination device for the light emitting element according to one aspect of the present invention, the current control unit sets the drive current to a predetermined current value when the intensity measured by the light measurement unit is equal to or less than the predetermined intensity threshold value. The determination unit is characterized in that the current control unit determines the state of failure of the light emitting element after the drive current is reduced to the predetermined current value.

In the failure determination device for the light emitting element according to one aspect of the present invention, the determination unit exceeds a predetermined time in which the voltage measured by the voltage measurement unit is out of a predetermined range determined by the drive current. In this case, it is characterized in that the state of failure of the light emitting element is determined.

In the failure determination device for a light emitting element according to one aspect of the present invention, a plurality of the light emitting elements are connected in series, and the determination unit determines the failure state of each of the light emitting elements, and the current control unit. Is characterized in that, when at least one of the plurality of light emitting elements is determined to be a failure by the determination unit, the drive current supplied to the light emitting element is increased.

In the light emitting element failure determination device according to one aspect of the present invention, a plurality of the light emitting elements are connected in series, and a detour circuit for diverting the current supplied to each of the light emitting elements to the light emitting element in the subsequent stage. The light emitting element, which is determined to be faulty, is characterized in that the drive current is bypassed by the bypass circuit according to the state of the fault.

The failure determination device for a light emitting element according to one aspect of the present invention has a plurality of light emitting element trains in which a plurality of the light emitting elements are connected in series, and the current control unit determines that the light emitting element has failed. If there is, the drive current supplied to the light emitting element row including the light emitting element determined to be defective is decreased, and the drive current supplied to the light emitting element row not including the light emitting element determined to be defective is increased. It may be configured to cause.

The failure determination device for a light emitting element according to one aspect of the present invention has a drive element that supplies the drive current to each of the plurality of light emitting element rows, and measures the temperature of the drive element for each of the plurality of light emitting element rows. The current control unit has the driving current of the driving element measured by the temperature measuring unit to supply the driving current supplied to the light emitting element train that does not include the light emitting element determined to be a failure. The configuration may be controlled according to the temperature.

In the light emitting element failure determination device according to one aspect of the present invention, the current control unit acquires a target value of the light intensity output by the plurality of the light emitting element trains, and the light intensity is equal to the target value. Therefore, the drive current supplied to the light emitting element train including the light emitting element determined to be a failure by the determination unit is reduced, and the light emission not including the light emitting element determined to be a failure by the determination unit. The drive current supplied to the element train may be increased.

In the light emitting element failure determination device according to one aspect of the present invention, the current control unit supplies the drive current to the light emitting element train that does not include the light emitting element determined to be a failure by the determination unit. The driving elements may be sequentially controlled according to the height of the temperature measured by the temperature measuring unit.

In the failure determination device for the light emitting element according to one aspect of the present invention, the current control unit uses the following order of the driving elements when the temperature of the driving elements measured by the temperature measuring unit reaches a threshold value. It may be configured to start control.

In the light emitting element failure determination device according to one aspect of the present invention, the current control unit uniformly increases the drive current supplied to the light emitting element train that does not include the light emitting element determined to be defective. After that, among the driving elements that supply the driving current to the light emitting element train, the driving current supplied by the driving element having the highest temperature measured by the temperature measuring unit is reduced, and a plurality of the light emitting element trains are used. Controls the drive element having the lowest temperature measured by the temperature measuring unit so that the intensity of the light output by the device reaches the target value, and the drive current supplied by the drive element having the lowest temperature reaches the threshold value. If this is the case, the configuration may be such that the driving element having the highest temperature and other driving elements other than the driving element having the lowest temperature are controlled.

The light emitting device according to one aspect of the present invention is characterized by including a light emitting element and a failure determination device for any one of the above light emitting elements.

The method for determining a failure of a light emitting element according to one aspect of the present invention includes a voltage measurement step for measuring a voltage applied to a light emitting element driven by a supplied drive current, a plurality of determination voltages determined from the drive current, and the above. Based on the voltage difference from the voltage measured in the voltage measurement step, a determination step of determining a plurality of states including a state in which the intensity of the light output by the light emitting element is lower than the normal state as a state of failure of the light emitting element. It is characterized by having.

According to the present invention, there is an effect that a plurality of states can be determined as a state of failure of the light emitting element.

FIG. 1 is a diagram showing a schematic configuration of a laser device according to the first embodiment. FIG. 2 is a block diagram showing a configuration of a function according to the first embodiment. FIG. 3 is a diagram showing the relationship between the reference voltage and the threshold value of the voltage for determining the failure. FIG. 4 is a flowchart showing a flow of processing for determining the state of the light emitting element in the first embodiment. FIG. 5 is a diagram showing a schematic configuration of the laser apparatus according to the second embodiment. FIG. 6 is a block diagram showing a configuration of functions according to the second embodiment. FIG. 7 is a flowchart showing a flow of processing for determining the state of the light emitting element in the second embodiment. FIG. 8 is a flowchart showing a flow of processing for determining the state of the light emitting element in the third embodiment. FIG. 9 is a diagram showing a schematic configuration of the laser apparatus according to the fourth embodiment. FIG. 10 is a block diagram showing a configuration of a function according to a fourth embodiment. FIG. 11 is a flowchart showing a flow of processing for determining the state of the light emitting element in the fourth embodiment. FIG. 12 is a diagram showing a schematic configuration of the laser apparatus according to the fifth embodiment. FIG. 13 is a diagram showing a modified example of the laser apparatus according to the fifth embodiment. FIG. 14 is a flowchart showing a flow of processing for determining the state of the light emitting element in the fifth embodiment. FIG. 15 is a flowchart showing an example of a processing flow for controlling the driving current of the FET in the fifth embodiment. FIG. 16 is a flowchart showing an example of a processing flow for controlling the driving current of the FET in the fifth embodiment. FIG. 17 is a flowchart showing an example of a processing flow for controlling the driving current of the FET in the fifth embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiments described below. Further, in the description of the drawings, the same or corresponding elements are appropriately designated by the same reference numerals.

[First Embodiment]
FIG. 1 is a diagram showing a schematic configuration of a laser device 1A according to a first embodiment of the present invention. The laser device 1A is a device that outputs laser light. The laser device 1A includes light emitting elements LD1 to LD3, a control unit 10, a power supply unit 20, a current sensor 30, a voltage detection unit 40, an FET 50, a display unit 60, and an operated unit 70. The laser device 1A is an example of a light emitting device. The laser device 1A is also an example of a failure determination device for a light emitting element.

The power supply unit 20 is a DC power supply that supplies electric power to the light emitting elements LD1 to LD3. The power supply unit 20 supplies the drive current for driving the light emitting elements LD1 to LD3 to the light emitting elements LD1 to LD3.

The light emitting element LD1, the light emitting element LD2, and the light emitting element LD3 are light sources that output light. In the present embodiment, the light emitting element LD1, the light emitting element LD2, and the light emitting element LD3 are laser diodes that output laser light, but are not limited to laser diodes. The light emitting element LD1, the light emitting element LD2, and the light emitting element LD3 are connected in series, the anode of the light emitting element LD1 is connected to the power supply unit 20, and the cathode of the light emitting element LD3 is connected to the FET 50. .. In the present embodiment, the number of light emitting elements included in the laser device 1A is three, but the number of light emitting elements included in the laser device 1A is not limited to three, and is two or less or four. It may be more than one.

The current sensor 30 is a sensor that measures the drive current flowing through the light emitting element LD1, the light emitting element LD2, and the light emitting element LD3. The current sensor 30 is, for example, a well-known current sensor using a sense resistor. The current sensor 30 detects a voltage applied to a sense resistor inserted in series between the cathode of the light emitting element LD3 and the drain terminal of the FET 50, and uses a signal representing the detected voltage as a signal representing the drive current in the control unit 10. Output to. The current sensor 30 may be a current sensor using a Hall element.

The FET 50 is a field effect transistor, and the drain terminal is connected to the cathode of the light emitting element LD3 via the current sensor 30, the gate terminal is connected to the control unit 10, and the source terminal is grounded. The FET 50 controls the drive current according to the voltage applied to the gate terminal. The current sensor 30 may be arranged between the source terminal of the FET 50 and the power supply unit 20.

The voltage detection unit 40 includes an AD conversion unit 40a, an AD conversion unit 40b, an AD conversion unit 40c, and an AD conversion unit 40d. The AD conversion unit 40a is connected to the anode of the light emitting element LD1, detects the voltage (voltage v1) applied to the anode of the light emitting element LD1, and outputs a digital signal indicating the detected voltage to the control unit 10. The AD conversion unit 40b is connected between the cathode of the light emitting element LD1 and the anode of the light emitting element LD2, detects the voltage (voltage v2) applied between the light emitting element LD1 and the light emitting element LD2, and detects the detected voltage. Is output to the control unit 10. The AD conversion unit 40c is connected between the cathode of the light emitting element LD2 and the anode of the light emitting element LD3, detects the voltage (voltage v3) applied between the light emitting element LD2 and the light emitting element LD3, and detects the detected voltage. Is output to the control unit 10. The AD conversion unit 40d is connected to the cathode of the light emitting element LD3, detects the voltage (voltage v4) applied to the cathode of the light emitting element LD3, and outputs a digital signal indicating the detected voltage to the control unit 10. When the number of light emitting elements included in the laser device 1A is different from the number shown in the figure, the laser device 1A includes an AD conversion unit of the number of light emitting elements + 1, and the voltage applied to the anode of the light emitting element connected to the power supply unit 20 and light emission. The voltage applied between the elements and the voltage applied to the cathode of the light emitting element connected to the FET 50 are detected.

In the present embodiment, the level conversion circuit that converts the voltage level of the electric signal is installed between the anode of the light emitting element LD1 and the AD conversion unit 40a, and between the light emitting element LD1 and the light emitting element LD2, and the AD conversion unit 40b. An electric signal provided between the light emitting element LD2 and the light emitting element LD3 to the AD conversion unit 40c and between the light emitting element LD3 and the AD conversion unit 40d, and the voltage level is converted by the level conversion circuit. May be input to the AD conversion unit 40a, the AD conversion unit 40b, the AD conversion unit 40c, and the AD conversion unit 40d.

The display unit 60 is composed of a liquid crystal display or the like, and displays, for example, various information of the laser device 1A and the states of the light emitting elements LD1 to LD3 with characters, symbols, images, and the like. The operated unit 70 includes a button for operating the laser device 1A. The operated unit 70 includes a button for switching between the output of the laser beam and the stop of the output, a button for starting the process of determining the state of the light emitting elements LD1 to LD3, and the like. The operated unit 70 is not limited to the buttons, and may be, for example, a touch panel as long as it accepts the operation of the operator of the laser device 1A.

The control unit 10 includes a calculation unit and a storage unit. The calculation unit performs various calculation processes for controlling the drive current for driving the light emitting elements LD1 to LD3, controlling the display unit 60, and realizing the functions included in the laser device 1A. The control unit 10 is composed of, for example, a CPU (Central Processing Unit), an FPGA (field-programmable gate array), or both a CPU and an FPGA.

The storage unit includes, for example, a portion composed of a ROM (Read Only Memory) and a portion composed of a RAM (Random Access Memory). Various programs and data used by the arithmetic unit to perform arithmetic processing are stored in the portion composed of the ROM. In addition, the RAM is used to store a work space when the arithmetic unit performs arithmetic processing, a result of arithmetic processing of the arithmetic unit, and the like.

FIG. 2 is a block diagram showing a configuration of a function according to the present embodiment among the functions realized by the arithmetic unit executing a program stored in the storage unit. The voltage measuring unit 101 acquires the digital signals supplied from the AD conversion units 40a to 40d. From the voltage represented by the acquired digital signal, the voltage measuring unit 101 calculates the forward voltage of the light emitting elements LD1 to LD3, the voltage applied to the light emitting element LD1 (voltage Vak1), the voltage applied to the light emitting element LD2 (voltage Vak2), and light emission. The voltage (voltage Vak3) applied to the element LD3 is obtained.

The current measuring unit 104 acquires a signal supplied from the current sensor 30 and obtains a current value represented by the acquired signal. Since the current sensor 30 measures the current flowing through the light emitting elements LD1 to LD3, it can be said that the current measuring unit 104 obtains the drive current.

The current control unit 105 determines the voltage applied to the gate terminal of the FET 50 by the current measurement unit 104 so that the output of the laser light from the light emitting elements LD1 to LD3 becomes the output instructed by the operated unit 70. The drive current is controlled by a constant current.

The determination unit 102 determines the states of the light emitting elements LD1 to LD3 based on the threshold value determined from the current value obtained by the current measurement unit 104 and the voltage Vak1, voltage Vak2, and voltage Vak3 obtained by the voltage measurement unit 101.

Specifically, the determination unit 102 stores a voltage threshold value for each of the light emitting elements LD1 to LD3 in order to determine a failure. For example, the determination unit 102 has a short-circuit threshold value (TH_sha1), an open threshold value (TH_opa1), a first output failure threshold value (TH_loa1), and a second output failure threshold value (TH_hia1) when the drive current is set to a ampere for the light emitting element LD1. ) Is remembered. The short-circuit threshold value (TH_sha1) is a threshold value for determining that the light-emitting element LD1 is in the short-circuit state, and the open threshold value (TH_opa1) is the threshold value for determining that the light-emitting element LD1 is in the open state. The output failure threshold value (TH_loa1) and the second output failure threshold value (TH_hia1) are threshold values for determining that the light emitting element LD1 is in the output reduction state.

FIG. 3A shows a voltage (Vak1), a short-circuit threshold value (TH_sha1), an open threshold value (TH_opa1), and a first output failure threshold value (TH_loa1) measured by the voltage measuring unit 101 when the drive current is set to a ampere. ) And the second output failure threshold value (TH_hia1). The voltage (Vak1) shown in FIG. 3A indicates the voltage when the light emitting element LD1 is not out of order. The short-circuit threshold value (TH_sha1) is smaller than the voltage value of the reference voltage Vsta applied to the light-emitting element LD1 when a drive current of a ampere flows through the light-emitting element LD1 that has not failed, and the open threshold value (TH_opa1) is , The value is larger than the voltage value of the reference voltage Vsta. The first output failure threshold value (TH_loa1) is smaller than the voltage value of the reference voltage Vsta and larger than the short-circuit threshold value (TH_sha1), and the second output failure threshold value (TH_hia1) is larger than the voltage value of the reference voltage Vsta and is open. It is a value smaller than the threshold value (TH_opa1).

Further, the determination unit 102 has a short-circuit threshold value (TH_shb1), an open threshold value (TH_opb1), a first output failure threshold value (TH_lob1), and a second output failure threshold value (TH_hibi1) when the drive current is set to b amperes smaller than a amperes. I remember. The short-circuit threshold value (TH_shb1) is a threshold value for determining that the light-emitting element LD1 is in the short-circuit state, and the open threshold value (TH_opb1) is the threshold value for determining that the light-emitting element LD1 is in the open state. The output failure threshold value (TH_lob1) and the second output failure threshold value (TH_hib1) are threshold values for determining that the light emitting element LD1 is in the output reduction state.

FIG. 3B shows a voltage (Vak1), a short-circuit threshold value (TH_shb1), an open threshold value (TH_opb1), and a first output failure threshold value (Bak1) measured by the voltage measuring unit 101 when the drive current is set to b amperes. It is a figure which shows an example of the relationship between TH_lob1) and the second output failure threshold value (TH_hibi1). The voltage (Vak1) shown in FIG. 3B indicates the voltage when the light emitting element LD1 is not out of order. The short-circuit threshold value (TH_shb1) is smaller than the voltage value of the reference voltage Vstb applied to the light-emitting element LD1 when a drive current of b ampere flows through the light-emitting element LD1 that has not failed, and the open threshold value (TH_opb1) is , The value is larger than the voltage value of the reference voltage Vstb. The first output failure threshold value (TH_lob1) is smaller than the voltage value of the reference voltage Vstb and larger than the short-circuit threshold value (TH_shb1), and the second output failure threshold value (TH_hibi1) is larger than the voltage value of the reference voltage Vstb and is open. It is a value smaller than the threshold value (TH_opb1). Further, the short-circuit threshold value (TH_shb1) is smaller than the short-circuit threshold value (TH_sha1), and the open threshold value (TH_oppb1) is smaller than the open threshold value (TH_opa1). Further, the first output failure threshold value (TH_lob1) is smaller than the first output failure threshold value (TH_loa1), and the second output failure threshold value (TH_hib1) is smaller than the second output failure threshold value (TH_hia1).

The determination unit 102 also stores the short-circuit threshold value, the open threshold value, the first output failure threshold value, and the second output failure threshold value with respect to the drive current of a ampere for the light emitting element LD2 and the light emitting element LD3, and the drive current of b ampere. On the other hand, the short-circuit threshold value, the open threshold value, the first output failure threshold value, and the second output failure threshold value are stored. The determination unit 102 can obtain the reference voltage and the threshold value corresponding to the drive current other than a ampere and b ampere by linear interpolation from the a ampere threshold value and the b ampere threshold value. The reference voltage and threshold value corresponding to the drive current other than a ampere and b ampere may be stored as a table instead of being obtained by linear interpolation. The reference voltage is an example of the determination voltage. Further, the short circuit threshold value, the open threshold value, the first output failure threshold value, and the second output failure threshold value are also examples of the determination voltage.

Returning to FIG. 2, the determination unit 102 includes a short-circuit threshold value, an open threshold value, a first output failure threshold value and a second output failure threshold value determined from the current value obtained by the current measurement unit 104, and a voltage value obtained by the voltage measurement unit 101. Are compared, and the states of the light emitting elements LD1 to LD3 are determined based on the result of the comparison. The method of determination will be described later.

The notification unit 103 controls the display unit 60 so that the determination result of the determination unit 102 is displayed on the display unit 60. As a result, the state of the light emitting elements LD1 to LD3 is notified to the operator of the laser device 1A.

FIG. 4 is a flowchart showing a flow of processing for determining the state of the light emitting elements LD1 to LD3. When the operator performs an operation of instructing the output of the laser beam to the operated unit 70, the control unit 10 executes the process shown in FIG.

First, in step S101, the control unit 10 (current control unit 105) obtains a drive current for the operator to perform the output specified by the operated unit 70, and applies a voltage corresponding to the obtained drive current to the gate terminal of the FET 50. do. As a result, the drive current for driving the light emitting elements LD1 to LD3 is supplied from the power supply unit 20 to the light emitting elements LD1 to LD3.

The AD conversion unit 40a outputs a digital signal indicating the voltage v1 to the control unit 10, and the AD conversion unit 40b outputs a digital signal indicating the voltage v2 to the control unit 10. Further, the AD conversion unit 40c outputs a digital signal indicating the voltage v3 to the control unit 10, and the AD conversion unit 40d outputs a digital signal indicating the voltage v4 to the control unit 10.

The control unit 10 (voltage measuring unit 101) measures the voltage applied to each of the light emitting elements LD1 to LD3 based on the digital signals supplied from the AD conversion units 40a to 40d (step S102). Specifically, the control unit 10 obtains the voltage values of the voltage v1, the voltage v2, the voltage v3 and the voltage v4 from the supplied digital signal, sets the difference between the voltage v1 and the voltage v2 as the voltage Vak1, and sets the voltage v2 and the voltage. The difference from v3 is defined as voltage Vak2, and the difference between voltage v3 and voltage v4 is defined as voltage Vak3.

Next, the control unit 10 (determination unit 102) acquires a threshold value for determining a failure of the light emitting elements LD1 to LD3 (step S103). Here, for example, when the drive current is a amperes, the control unit 10 has a short-circuit threshold value (TH_sha1), an open threshold value (TH_opa1), a first output failure threshold value (TH_loa1), and a second output failure threshold value corresponding to the light emitting element LD1. (TH_thia1) is acquired. Further, the control unit 10 also acquires the corresponding short-circuit threshold value, open threshold value, first output failure threshold value, and second output failure threshold value for the light emitting element LD2 and the light emitting element LD3.

The control unit 10 (determination unit 102) selects a light emitting element for determining the state (step S104), and determines the state of the selected light emitting element in step S105 and subsequent steps. For example, the control unit 10 first selects the light emitting element LD1 and determines whether the voltage Vak1 applied to the light emitting element LD1 is equal to or less than the short circuit threshold value (TH_sha1) (step S105). When the voltage Vak1 is equal to or less than the short-circuit threshold value (TH_sha1) (Yes in step S105), the control unit 10 proceeds to step S109. Here, the control unit 10 determines that the light emitting element LD1 is in a short-circuited state. In other words, it can be said that the control unit 10 here determines whether the voltage difference between the reference voltage Vsta and the voltage Vak1 determined from the drive current is equal to or greater than the voltage difference between the reference voltage Vsta and the short-circuit threshold (TH_sha1). It can be said that the determination is made based on the voltage difference between the short-circuit threshold value (TH_sha1) determined from the drive current and the voltage Vak1. The control unit 10 (notification unit 103) controls the display unit 60 in step S109, notifies that the light emitting element LD1 is in a short-circuited state with characters or symbols, and then proceeds to step S108.

When the voltage Vak1 is not equal to or lower than the short-circuit threshold value (TH_sha1) (No in step S105), the control unit 10 determines whether the voltage Vak1 is equal to or higher than the open threshold value (TH_opa1) (step S106). When the voltage Vak1 is equal to or higher than the open threshold value (TH_opa1) (Yes in step S106), the control unit 10 proceeds to step S110. Here, the control unit 10 determines that the light emitting element LD1 is in the open state. In other words, here, the control unit 10 determines whether the voltage difference between the reference voltage Vsta and the voltage Vak1 is equal to or greater than the voltage difference between the reference voltage Vsta determined from the drive current and the open threshold (TH_opa1). No, it can be said that the determination is made based on the voltage difference between the open threshold (TH_opa1) determined from the drive current and the voltage Vak1. The control unit 10 (notification unit 103) controls the display unit 60 in step S110, notifies that the light emitting element LD1 is in the open state with characters or symbols, and then proceeds to step S108.

When the voltage Vak1 is not equal to or higher than the open threshold value (TH_opa1) (No in step S106), the control unit 10 determines whether the voltage Vak1 is within the normal range (step S107). Specifically, the control unit 10 determines whether the first output failure threshold value (TH_loa1) <voltage Vak1 <second output failure threshold value (TH_hia1). When the control unit 10 does not have the first output failure threshold value (TH_loa1) <voltage Vak1 <second output failure threshold value (TH_hia1), in other words, the short circuit threshold value (TH_sha1) <voltage Vak1 ≦ first output failure threshold value (TH_loa1), Alternatively, if the second output failure threshold value (TH_hia1) ≤ voltage Vak1 <open threshold value (TH_opa1) (No in step S107), the process proceeds to step S111. The range of the short-circuit threshold value (TH_sha1) <voltage Vak1 ≤ first output failure threshold value (TH_loa1) and the second output failure threshold value (TH_hia1) ≤ voltage Vak1 <opening threshold value (TH_opa1) is an example of the output failure range. Here, the control unit 10 determines whether the voltage difference between the reference voltage Vsta and the voltage Vak1 is equal to or greater than the voltage difference between the reference voltage Vsta determined by the drive current and the first output failure threshold (TH_loa1). It can be said that it is determined whether or not it is equal to or larger than the voltage difference from the output failure threshold (TH_hia1), and the voltage difference between the first output failure threshold (TH_loa1) determined from the drive current and the voltage Vak1 and the second output determined from the drive current. It can be said that the determination is made based on the voltage difference between the failure threshold (TH_hia1) and the voltage Vak1.

FIG. 3C is a diagram showing an example of a change in the voltage Vka1 when the light emitting element LD1 fails. The output of the light emitting element LD1 decreases, and as shown in FIG. 3C, the voltage Vak1 changes to a voltage between the short-circuit threshold value (TH_sha1) and the first output failure threshold value (TH_loa1), and the changed voltage. When the above is measured, the control unit 10 proceeds to step S111. Here, the control unit 10 determines that the light emitting element LD1 is in the output reduction state. The control unit 10 (notification unit 103) controls the display unit 60 in step S111, notifies that the light emitting element LD1 is in the output reduction state with characters or symbols, and then proceeds to step S108.

The control unit 10 determines in step S108 whether or not the states of all the light emitting elements LD1 to LD3 have been determined. If the control unit 10 has not determined the states of all the light emitting elements LD1 to LD3 (No in step S108), the control unit 10 proceeds to step S104. When the control unit 10 proceeds to step S104, for example, the light emitting element LD2 is selected as the light emitting element whose state has not been determined, and the voltage Vak2, the short circuit threshold value, the opening threshold value, and the first output failure threshold value corresponding to the light emitting element LD2 are selected. And the second output failure threshold value is used to determine the state of the light emitting element LD2 in the same manner as when determining the state of the light emitting element LD1.

When the control unit 10 finishes determining the state of the light emitting element LD2, the process proceeds from step S108 to step S104, selects the light emitting element LD3 whose state has not been determined, and sets the voltage Vak3 and the short-circuit threshold value corresponding to the light emitting element LD3. Using the open threshold value, the first output failure threshold value, and the second output failure threshold value, the state of the light emitting element LD3 is determined in the same manner as when the state of the light emitting element LD1 is determined. When the control unit 10 determines the states of all the light emitting elements LD1 to LD3 (Yes in step S108), the control unit 10 ends the process of FIG.

As described above, according to the first embodiment, it is possible to determine the states of short circuit, open (open), and output decrease as failure states of each of the light emitting elements LD1 to LD3.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 5 is a diagram showing a schematic configuration of the laser device 1B according to the second embodiment. The second embodiment is different from the first embodiment in that the intensity of the light output by the light emitting elements LD1 to LD3 is measured and the state of the light emitting elements LD1 to LD3 is determined by using the measurement result of the light intensity. The same configuration as that of the first embodiment is designated by the same reference numerals and description thereof will be omitted. In the following description, differences from the first embodiment will be described.

The laser device 1B includes a light intensity detecting unit 80. The light intensity detection unit 80 includes a photodiode that measures the sum of the light intensities output by the light emitting elements LD1 to LD3. This photodiode outputs a signal representing the measured light intensity to the control unit 10.

FIG. 6 is a block diagram showing a configuration of a function according to a second embodiment among the functions realized by the arithmetic unit executing a program stored in the storage unit. The intensity measuring unit 106 acquires a signal supplied from the light intensity detecting unit 80. The intensity measuring unit 106 obtains the intensity of the light represented by the acquired signal.

The determination unit 102 according to the second embodiment has light for determining failure in each of the light emitting elements LD1 to LD3, in addition to the above-mentioned short-circuit threshold value, open threshold value, first output failure threshold value, and second output failure threshold value. The threshold value (light threshold value) of the intensity of is stored. For example, the determination unit 102 stores a first optical threshold value (TH_R1) for determining that the light emitting elements LD1 to LD3 have failed with respect to the drive current of a ampere. Further, the determination unit 102 stores a second optical threshold value (TH_R2) for determining that the light emitting elements LD1 to LD3 have failed with respect to the drive current of b amperes. The determination unit 102 obtains the optical threshold value corresponding to the drive current other than a ampere and b ampere by linear interpolation from the first optical threshold value (TH_R1) of a ampere and the second optical threshold value (TH_R2) of b ampere. These optical thresholds are examples of predetermined intensity thresholds.

The determination unit 102 compares the light intensity obtained by the intensity measurement unit 106 with the light threshold value to determine whether the light emitting elements LD1 to LD3 are out of order, and if it is determined that the light emitting elements LD1 to LD3 are out of order, the short-circuit threshold value is set. The open threshold value, the first output failure threshold value, and the second output failure threshold value are compared with the voltage value obtained by the voltage measuring unit 101, and the states of the light emitting elements LD1 to LD3 are determined based on the comparison result.

FIG. 7 is a flowchart showing a flow of processing for determining the state of the light emitting elements LD1 to LD3 in the second embodiment. When the operator performs an operation of instructing the output of the laser beam to the operated unit 70, the control unit 10 executes the process shown in FIG. 7.

First, in step S201, the control unit 10 (current control unit 105) obtains a drive current for the operator to perform the output specified by the operated unit 70, and applies a voltage corresponding to the obtained drive current to the gate terminal of the FET 50. do.

Next, the control unit 10 (voltage measuring unit 101, intensity measuring unit 106) measures the sum of the intensities of the light output by the light emitting elements LD1 to LD3 and the voltage applied to each of the light emitting elements LD1 to LD3 (step). S202). Specifically, the control unit 10 obtains the voltage values of the voltage v1, the voltage v2, the voltage v3 and the voltage v4 from the digital signals supplied from the AD conversion units 40a to 40d, and sets the difference between the voltage v1 and the voltage v2 as the voltage. Let Vak1, the difference between voltage v2 and voltage v3 be voltage Vak2, and the difference between voltage v3 and voltage v4 be voltage Vak3. Further, the control unit 10 acquires a signal supplied from the light intensity detection unit 80 and measures the sum of the light intensities output by the light emitting elements LD1 to LD3.

Next, the control unit 10 (determination unit 102) acquires a threshold value for determining a failure of the light emitting elements LD1 to LD3 (step S203). Here, for example, when the drive current is a amperes, the control unit 10 acquires the first optical threshold value (TH_R1) corresponding to the drive current of a amperes. Further, when the drive current is a ample, the control unit 10 has a short-circuit threshold value (TH_sha1), an open threshold value (TH_opa1), a first output failure threshold value (TH_loa1), and a second output failure threshold value (TH_hia1) corresponding to the light emitting element LD1. ) Is acquired, and the short-circuit threshold value, the open threshold value, the first output failure threshold value, and the second output failure threshold value are also acquired for the light emitting element LD2 and the light emitting element LD3.

The control unit 10 (determination unit 102) selects a light emitting element for determining the state (step S204), and determines the state of the selected light emitting element in step S205 and subsequent steps. For example, the control unit 10 first selects the light emitting element LD1 (step S204), and the sum of the light intensities output by the light emitting elements LD1 to LD3 measured in step S202 is equal to or less than the light threshold value acquired in step S203. (Step S205). The control unit 10 changes the order of step S204 and step S205 so that step S204 is performed after step S205 is performed. If No is determined in step S205, the process of FIG. 7 is terminated and the step is performed. If No is determined in S209, the process may return to step S204. By doing so, the number of executions of step S205 can be reduced.

When measuring the voltage related to the light emitting element, for example, the voltage when noise is placed on the line connecting the AD conversion units 40a to 40D and the light emitting elements LD1 to LD3 may be measured. In this case, in the configuration of the first embodiment, the state is determined using the voltage detection result when noise is on the line connecting the AD conversion units 40a to 40D and the light emitting elements LD1 to LD3. Even if the light emitting element is not broken, it may be determined as a failure.

On the other hand, regarding the sum of the light intensities output by the light emitting elements LD1 to LD3, the measured light intensity is lower than that in the normal state regardless of whether the failure state is short-circuit, open, or output decrease. If there is no failure, it does not change even if noise is added to the line connecting the AD conversion units 40a to 40D and the light emitting elements LD1 to LD3. Therefore, in the second embodiment, the sum of the light intensities output by the light emitting elements LD1 to LD3 is used, and in step S205, first, the measurement result of the sum of the light intensities not affected by noise is used to determine whether the failure occurs. It is judged whether or not.

When the sum of the light intensities output by the light emitting elements LD1 to LD3 exceeds the optical threshold value acquired in step S203 (No in step S205), the control unit 10 proceeds to step S209. Here, the control unit 10 determines that the light emitting elements LD1 to LD3 are in a non-failed state.

When the sum of the light intensities output by the light emitting elements LD1 to LD3 is equal to or less than the optical threshold value acquired in step S203 (Yes in step S205), the control unit 10 proceeds to step S206. Here, the control unit 10 determines that at least one of the light emitting elements LD1 to LD3 is in a failed state.

The processing of step S206 is the same as that of step S105, and the processing of step S210 that proceeds when it is determined to be Yes in step S206 is the same as that of step S109. The process of step S207 is the same as that of step S106, and the process of step S211 that proceeds when it is determined to be Yes in step S207 is the same as that of step S110. The process of step S208 is the same as that of step S107, and the process of step S212 that proceeds when No is determined in step S208 is the same as that of step S111. That is, in the second embodiment, the control unit 10 determines the short-circuit state, the open state, and the output reduction state in steps S206 to S208, and notifies the failure state in steps S210 to S212. ..

The control unit 10 determines whether or not the states of all the light emitting elements LD1 to LD3 have been determined in step S209. If the control unit 10 has not determined the states of all the light emitting elements LD1 to LD3 (No in step S209), the control unit 10 proceeds to step S204. When the control unit 10 proceeds to step S204, for example, the light emitting element LD2 is selected as the light emitting element whose state has not been determined, and the voltage Vak2, the light threshold value, the short circuit threshold value corresponding to the light emitting element LD2, the opening threshold value, and the first Using the output failure threshold value and the second output failure threshold value, the state of the light emitting element LD2 is determined in the same manner as when the state of the light emitting element LD1 is determined.

When the control unit 10 finishes determining the state of the light emitting element LD2, the process proceeds from step S209 to step S204, selects the light emitting element LD3 as the light emitting element for determining the state, and corresponds to the voltage Vak3, the light threshold value, and the light emitting element LD3. The state of the light emitting element LD3 is determined in the same manner as when the state of the light emitting element LD1 is determined by using the short-circuit threshold value, the open threshold value, the first output failure threshold value, and the second output failure threshold value. When the control unit 10 determines the states of all the light emitting elements LD1 to LD3 (Yes in step S209), the control unit 10 ends the process of FIG. 7.

As described above, according to the second embodiment, even if noise is added to the line connecting the AD conversion units 40a to 40D and the light emitting elements LD1 to LD3, it is possible to prevent the determination as a failure.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. In the third embodiment, when it is determined that the failure is based on the measurement result of the light intensity output by the light emitting elements LD1 to LD3, the drive current supplied to the light emitting element is changed for the failure of the output decrease. The second embodiment is different from the second embodiment in that the voltage Vak1, the voltage Vak2, and the voltage Vak3 are measured, and the failure is determined by using the voltage Vak1, the voltage Vak2, and the voltage Vak3 after changing the drive current. Hereinafter, the differences from the second embodiment will be described.

The determination unit 102 according to the third embodiment sets the drive current to a predetermined predetermined current value in addition to the various threshold values described in the first embodiment and the second embodiment for each of the light emitting elements LD1 to LD3. It also stores a short-circuit threshold value, an open threshold value, a first output failure threshold value, and a second output failure threshold value for sometimes determining a failure. This predetermined current value is a value close to the oscillation threshold current when, for example, the light emitting elements LD1 to LD3 are laser diodes. The predetermined current value is not limited to a value close to the oscillation threshold current.

The determination unit 102 determines that the output of the light emitting element LD1 has decreased when the drive current of a predetermined current value is supplied to the light emitting elements LD1 to LD3, so that the third output failure threshold value (TH_lo11) and the fourth output failure threshold value are determined. (TH_hi11) is memorized. The third output failure threshold (TH_lo11) is a value smaller than the voltage value of the reference voltage applied to the light emitting element LD1 when a drive current of a predetermined current value flows through the light emitting element LD1 that has not failed, and is the fourth output. The failure threshold value (TH_hi11) is a value larger than the voltage value of the reference voltage applied to the light emitting element LD1 when a driving current of a predetermined current value flows through the light emitting element LD1 that has not failed.

FIG. 8 is a flowchart showing a flow of processing for determining the state of the light emitting elements LD1 to LD3 in the third embodiment. When the operator performs an operation of instructing the output of the laser beam to the operated unit 70, the control unit 10 executes the process shown in FIG.

Since the processing of step S301 is the same as that of step S201 and the processing of step S302 is the same as that of step S202, the description thereof will be omitted.

Next, the control unit 10 (determination unit 102) acquires a threshold value for determining a failure of the light emitting elements LD1 to LD3 (step S303). Here, for example, when the drive current is a amperes, the control unit 10 acquires an optical threshold value corresponding to the drive current of a amperes. Further, the control unit 10 acquires the short-circuit threshold value (TH_sha1), the open threshold value (TH_opa1), the first output failure threshold value (TH_loa1), and the second output failure threshold value (TH_hia1) corresponding to the light emitting element LD1 and sets the light emitting element LD2. The light emitting element LD3 also acquires the short-circuit threshold value, the open threshold value, the first output failure threshold value, and the second output failure threshold value. Further, for the light emitting elements LD1 to LD3, the third output failure threshold value (TH_lo11) and the fourth output failure threshold value (TH_hi11) are also acquired.

The control unit 10 (determination unit 102) selects a light emitting element for determining the state (step S304), and determines the state of the selected light emitting element in step S305 or later. For example, the control unit 10 first selects the light emitting element LD1 (step S304), and the sum of the light intensities output by the light emitting elements LD1 to LD3 measured in step S302 is equal to or less than the light threshold value acquired in step S303. (Step S305). The control unit 10 swaps the order of step S304 and step S305 to perform step S304 after performing step S305. If No is determined in step S305, the process of FIG. 8 is terminated and the step S305 is performed. If No is determined in S311, the process may return to step S304. By doing so, the number of executions of step S305 can be reduced.

When the sum of the light intensities output by the light emitting elements LD1 to LD3 exceeds the light threshold value acquired in step S303 (No in step S305), the control unit 10 proceeds to step S311. Here, the control unit 10 determines that the light emitting elements LD1 to LD3 are in a non-failed state.

When the sum of the light intensities output by the light emitting elements LD1 to LD3 is equal to or less than the optical threshold value acquired in step S303 (Yes in step S305), the control unit 10 proceeds to step S306. Here, the control unit 10 determines that at least one of the light emitting elements LD1 to LD3 is in a failed state.

The process of step S306 is the same as that of step S105, and the process of step S312 that proceeds when it is determined to be Yes in step S306 is the same as that of step S109. The process of step S307 is the same as that of step S106, and the process of step S313 that proceeds when it is determined to be Yes in step S307 is the same as that of step S110. Therefore, the processing of step S306, step S307, step S312, and step S313 will be omitted.

When the control unit 10 (current control unit 105) determines No in step S307, the control unit 10 changes the voltage applied to the gate terminal of the FET 50 to set the drive current of the light emitting element to a predetermined current value (step S308). At this time, when the predetermined current value is set smaller than the drive current obtained in step S301, the voltage applied to the light emitting element when the predetermined current value is flowing in the output reduced state and the predetermined current value without failure flow. It is possible to increase the difference from the voltage applied to the light emitting element while the current is on, and it is possible to reduce erroneous determination due to noise. Next, the control unit 10 (voltage measurement unit 101) applies a voltage Vak1 to each of the light emitting elements LD1 to LD3 when the drive current is set to a predetermined current value based on the digital signals supplied from the AD conversion units 40a to 40d. , Voltage Vak2 and voltage Vak3 are measured (step S309).

Next, the control unit 10 determines whether the voltage applied to the selected light emitting element is within the normal range (step S310). Specifically, when the light emitting element LD1 is selected as the light emitting element for determining the failure, the control unit 10 has the third output failure threshold value (TH_lo11) <voltage Vak1 <fourth output failure threshold value (TH_hi11). judge. The control unit 10 proceeds to step S314 when the third output failure threshold value (TH_lo11) <voltage Vak1 <fourth output failure threshold value (TH_hi11) is not satisfied (No in step S310). Here, the control unit 10 determines that the light emitting element LD1 is in the output reduction state. The control unit 10 (notification unit 103) controls the display unit 60 in step S314, notifies that the light output of the light emitting element LD1 is in a reduced state with characters or symbols, and then proceeds to step S311.

The control unit 10 determines whether or not the states of all the light emitting elements LD1 to LD3 have been determined in step S311. If the control unit 10 has not determined the states of all the light emitting elements LD1 to LD3 (No in step S311), the control unit 10 proceeds to step S304. When the control unit 10 proceeds to step S304, the control unit 10 selects, for example, the light emitting element LD2 as the light emitting element whose state has not been determined, and determines the state in the same manner as the light emitting element LD1. When the light emitting element LD2 is newly selected as the light emitting element to be determined, the voltage used for determining the state in steps S306 and S307 is the voltage Vak2 measured in step S302. When the control unit 10 finishes determining the state of the light emitting element LD2, the process proceeds to step S304 again, selects the light emitting element LD3 as the light emitting element for determining the state, and determines the state in the same manner as the light emitting element LD1. When the light emitting element LD2 is newly selected as the light emitting element to be determined, the voltage used for determining the state in steps S306 and S307 is the voltage Vak3 measured in step S302. When the control unit 10 finishes determining the state of the light emitting element LD3 (Yes in step S311), the control unit 10 ends the process of FIG.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. FIG. 9 is a diagram showing a schematic configuration of the laser device 1D according to the fourth embodiment. The fourth embodiment is different from the first embodiment in that when there is a light emitting element determined to be open or reduced in output, a drive current is passed to another light emitting element by bypassing the light emitting element in which the open or output is reduced. ..

The laser device 1D includes a detour circuit 90. The bypass circuit 90 is a circuit that bypasses the drive current supplied to the failed light emitting element, and includes FET 51, FET 52, and FET 53. The FETs 51 to 53 are field effect transistors, and the gate terminal is connected to the control unit 10.

In the FET 51, the drain terminal is connected to the anode of the light emitting element LD1, and the source terminal is connected between the cathode of the light emitting element LD1 and the anode of the light emitting element LD2. When a voltage for turning on the FET 51 is applied from the control unit 10 to the gate terminal of the FET 51, the drive current bypasses the light emitting element LD1 and flows to the light emitting element LD2 via the FET 51. In the FET 52, the drain terminal is connected between the cathode of the light emitting element LD1 and the anode of the light emitting element LD2, and the source terminal is connected between the cathode of the light emitting element LD2 and the anode of the light emitting element LD3. When a voltage for turning on the FET 52 is applied from the control unit 10 to the gate terminal of the FET 52, the drive current bypasses the light emitting element LD2 and flows to the light emitting element LD3 via the FET 52. In the FET 53, the drain terminal is connected between the cathode of the light emitting element LD2 and the anode of the light emitting element LD3, and the source terminal is connected to the cathode of the light emitting element LD3. When a voltage for turning on the FET 53 is applied from the control unit 10 to the gate terminal of the FET 53, the drive current bypasses the light emitting element LD3 and flows through the FET 53.

FIG. 10 is a block diagram showing a configuration of a function according to a fourth embodiment among the functions realized by the arithmetic unit executing a program stored in the storage unit. The detour control unit 107 controls the voltage at the gate terminal of the FETs 51 to 53 so that the drive current bypasses the light emitting element determined by the determination unit 102 to be open or output reduction.

FIG. 11 is a flowchart showing a flow of processing for determining the state of the light emitting elements LD1 to LD3 in the fourth embodiment. When the operator performs an operation for instructing the output of the laser beam to the operated unit 70, the control unit 10 executes the process shown in FIG. The processing of steps S401 to S404 is the same as the processing of steps S101 to S104. Further, the processing of step S405 is the same as that of step S105, and the processing of step S409 that proceeds when it is determined to be Yes in step S405 is the same as that of step S109. Therefore, the description of steps S401 to S405 and step S409 will be omitted.

The control unit 10 proceeds to step S413 after step S409. When the control unit 10 (current control unit 105) determines, for example, that the light emitting element LD1 selected in step S404 is short-circuited, the control unit 10 controls the voltage applied to the gate terminal of the FET 50 and increases the drive current in step S413. .. Here, since the output of the light emitting element LD1 determined to be a failure is insufficient, the control unit 10 uses a light emitting element other than the light emitting element LD1 determined to be in a short-circuited state to obtain a drive current so that an output specified by the operator can be obtained. To set. The control unit 10 proceeds to step S408 after step S413. Since the process of step S408 is the same as the process of step S108, the description thereof will be omitted.

The control unit 10 selects the light emitting element LD1 in step S404, and if the voltage Vak1 is not equal to or lower than the short-circuit threshold value (TH_sha1) (No in step S405), determines whether the voltage Vak1 is equal to or higher than the open threshold value (TH_opa1) (step). S406). When the voltage Vak1 is equal to or higher than the open threshold value (TH_opa1) (Yes in step S406), the control unit 10 proceeds to step S410. Here, the control unit 10 determines that the light emitting element LD1 is in the open state. The control unit 10 (notification unit 103) controls the display unit 60 in step S410, notifies that the light emitting element LD1 is in the open state with characters or symbols, and then proceeds to step S412.

When the control unit 10 determines that the light emitting element LD1 is in the open state, the control unit 10 controls the bypass circuit 90 so that the drive current bypasses the light emitting element LD1 in which the drive current has stopped flowing (step S412). Specifically, when the light emitting element LD1 is selected in step S404, the control unit 10 applies a voltage for turning on the FET 51 to the gate terminal of the FET 51. Next, the control unit 10 controls the voltage applied to the gate terminal of the FET 50 to increase the drive current (step S413). Here, the control unit 10 sets the drive current for a light emitting element other than the light emitting element LD1 determined to be in the open state so that an output specified by the operator can be obtained.

The control unit 10 selects the light emitting element LD1 in step S404, and if the voltage Vak1 is not equal to or higher than the open threshold value (TH_opa1) (No in step S406), determines whether the voltage Vak1 is within the normal range (step S407). Specifically, the control unit 10 determines whether the first output failure threshold value (TH_loa1) <voltage Vak1 <second output failure threshold value (TH_hia1). If the first output failure threshold value (TH_loa1) <voltage Vak1 <second output failure threshold value (TH_hia1) is not satisfied (No in step S407), the control unit 10 proceeds to step S411. Here, the control unit 10 determines that the light emitting element LD1 is in the output reduction state.

The control unit 10 (notification unit 103) controls the display unit 60 in step S411, notifies that the light emitting element LD1 is in the output reduction state with characters or symbols, and then executes the processes of steps S412 and S413. When the control unit 10 determines that the output of the light emitting element LD1 is in a reduced state, the control unit 10 controls the detour circuit 90 (step S412). Specifically, when the light emitting element LD1 is selected in step S404, the control unit 10 applies a voltage for turning on the FET 51 to the gate terminal of the FET 51. Next, the control unit 10 controls the voltage applied to the gate terminal of the FET 50 to increase the drive current (step S413). Here, the control unit 10 sets the drive current so that the output instructed by the operator can be obtained from the light emitting elements other than the light emitting element LD1 determined to be in the output reduction state. The control unit 10 controls the display unit 60 in step S411 to notify that the light emitting element LD1 is in the output reduced state with characters or symbols, and then does not control the detour circuit 90 in step S412, but in step S413. The voltage applied to the gate terminal of the FET 50 may be controlled to increase the drive current so that the output specified by the operator can be obtained.

The control unit 10 proceeds to step S408 after step S413. The control unit 10 determines whether or not the states of all the light emitting elements LD1 to LD3 have been determined in step S408. If the control unit 10 has not determined the states of all the light emitting elements LD1 to LD3 (No in step S408), the control unit 10 proceeds to step S404. When the control unit 10 determines the states of all the light emitting elements LD1 to LD3 (Yes in step S408), the control unit 10 ends the process of FIG.

According to the fourth embodiment, a drive current can be passed to another light emitting element by bypassing the light emitting element determined to be a failure. When the control unit 10 determines that the light emitting element is in the output reduced state, the control unit 10 controls the light emitting element determined to be in the output reduced state so that the drive current does not bypass, and the drive current is obtained so that the output instructed by the operator can be obtained. May be controlled to increase.

[Fifth Embodiment]
Next, a fifth embodiment of the present invention will be described. FIG. 12 is a diagram showing a schematic configuration of the laser device 1E according to the fifth embodiment. In the fifth embodiment, the same components as those in the above-described embodiments are designated by the same reference numerals and the description thereof will be omitted. In the following description, the differences from the above-described embodiments will be described.

The light emitting elements LD1A to LD3A, the light emitting elements LD1B to LD3B, and the light emitting elements LD1C to LD3C are the same light emitting elements as the light emitting element LD1. In the laser device 1E, the light emitting elements LD1A to LD2A and LD3A are connected in series, the light emitting elements LD1B, LD2B and LD3B are connected in series, and the light emitting elements LD1C, LD2C and LD3C are connected in series. In the following description, for convenience of explanation, the rows of light emitting elements LD1A to LD3A are referred to as light emitting element rows C1, the rows of light emitting elements LD1B to LD3B are referred to as light emitting element rows C2, and the rows of light emitting elements LD1C to LD3C are referred to as light emitting elements. It is referred to as column C3. The number of light emitting elements connected in series in each light emitting element row is not limited to three, and may be four or more.

Like the voltage detection unit 40, the voltage detection units 40A to 40C include an AD conversion unit 40a, an AD conversion unit 40b, an AD conversion unit 40c, and an AD conversion unit 40d. In FIG. 12, the AD conversion unit 40a, the AD conversion unit 40b, the AD conversion unit 40c, and the AD conversion unit 40d are not shown. The voltage detection unit 40A has a voltage applied to the anode of the light emitting element LD1A, a voltage applied between the cathode of the light emitting element LD1A and the anode of the light emitting element LD2A, and a voltage applied between the cathode of the light emitting element LD2A and the anode of the light emitting element LD3A. And the voltage applied to the cathode of the light emitting element LD3A is detected. The voltage detection unit 40B has a voltage applied to the anode of the light emitting element LD1B, a voltage applied between the cathode of the light emitting element LD1B and the anode of the light emitting element LD2B, and a voltage applied between the cathode of the light emitting element LD2B and the anode of the light emitting element LD3B. And the voltage applied to the cathode of the light emitting element LD3B is detected. The voltage detection unit 40C has a voltage applied to the anode of the light emitting element LD1C, a voltage applied between the cathode of the light emitting element LD1C and the anode of the light emitting element LD2C, and a voltage applied between the cathode of the light emitting element LD2C and the anode of the light emitting element LD3C. And the voltage applied to the cathode of the light emitting element LD3C is detected.

The current sensors 30A to 30C are the same sensors as the current sensor 30. The current sensor 30A is connected to the cathode of the light emitting element LD3A and measures the current value of the current flowing through the light emitting element row C1. The current sensor 30B is connected to the cathode of the light emitting element LD3B and measures the current value of the current flowing through the light emitting element row C2. The current sensor 30C is connected to the cathode of the light emitting element LD3C and measures the current value of the current flowing through the light emitting element row C3.

FETs 50A to 50C are the same field effect transistors as FET50. In the FET 50A, the drain terminal is connected to the cathode of the light emitting element LD3A via the current sensor 30A, the gate terminal is connected to the output terminal of the operational amplifier 54A, and the source terminal is grounded. In the FET 50B, the drain terminal is connected to the cathode of the light emitting element LD3B via the current sensor 30B, the gate terminal is connected to the output terminal of the operational amplifier 54B, and the source terminal is grounded. In the FET 50C, the drain terminal is connected to the cathode of the light emitting element LD3C via the current sensor 30C, the gate terminal is connected to the output terminal of the operational amplifier 54C, and the source terminal is grounded.

The input terminals of the operational amplifiers 54A to 54C are connected to the control unit 10 and the ground. The output terminal of the operational amplifier 54A is connected to the gate terminal of the FET 50A, the output terminal of the operational amplifier 54B is connected to the gate terminal of the FET 50B, and the output terminal of the operational amplifier 54C is connected to the gate terminal of the FET 50C. The operational amplifier 54A applies a voltage corresponding to the voltage applied to the input terminal from the control unit 10 to the gate terminal of the FET 50A, and the operational amplifier 54B applies a voltage corresponding to the voltage applied to the input terminal from the control unit 10 to the FET 50B. When applied to the gate terminal, the operational amplifier 54C applies a voltage corresponding to the voltage applied to the input terminal from the control unit 10 to the gate terminal of the FET 50C.

Thermistors 55A to 55C are used as temperature sensors for measuring the temperature of FETs 50A to 50C. The thermistor 55A is arranged in the vicinity of the FET 50A, is connected to the control unit 10 and the AD conversion unit 41A, and a voltage is applied from the control unit 10. The thermistor 55B is arranged in the vicinity of the FET 50B, is connected to the control unit 10 and the AD conversion unit 41B, and a voltage is applied from the control unit 10. The thermistor 55C is arranged in the vicinity of the FET 50C, is connected to the control unit 10 and the AD conversion unit 41C, and a voltage is applied from the control unit 10.

The AD conversion unit 41A outputs a digital signal indicating the output voltage of the thermistor 55A to the control unit 10, and the AD conversion unit 41B outputs a digital signal indicating the output voltage of the thermistor 55B to the control unit 10, and the AD conversion unit 41C Outputs a digital signal indicating the output voltage of the thermistor 55C to the control unit 10. The thermistors 55A to 55C and AD conversion units 41A to 41C are examples of temperature measuring units.

The laser device 1E has a configuration in which the number of pairs of the light emitting element train, the voltage detection unit, the current sensor, the FET, the operational amplifier, the thermistor, and the AD conversion unit is 3, but the number of the pairs is 4 or more. That is, the number of light emitting element rows may be four or more.

Although the laser device 1E does not have the above-mentioned detour circuit, it may have a detour circuit. FIG. 13 is a diagram showing a schematic configuration of a laser device 1F in which bypass circuits 90A to 90C are added to the laser device 1E.

The detour circuit 90A includes FETs 51A to 53A. In the FET 51A, the drain terminal is connected to the anode of the light emitting element LD1A, and the source terminal is connected between the cathode of the light emitting element LD1A and the anode of the light emitting element LD2A. The drain terminal of the FET 52A is connected between the cathode of the light emitting element LD1A and the anode of the light emitting element LD2A, and the source terminal is connected between the cathode of the light emitting element LD2A and the anode of the light emitting element LD3A. In the FET 53A, the drain terminal is connected between the cathode of the light emitting element LD2A and the anode of the light emitting element LD3A, and the source terminal is connected to the cathode of the light emitting element LD3A. When a voltage for turning on the FET 51A is applied from the control unit 10, the drive current bypasses the light emitting element LD1A, and when a voltage for turning on the FET 52A is applied from the control unit 10, the drive current bypasses the light emitting element LD2A. Then, when a voltage for turning on the FET 53A is applied from the control unit 10, the drive current bypasses the light emitting element LD3A.

The detour circuit 90B includes FETs 51B to 53B. In the FET 51B, the drain terminal is connected to the anode of the light emitting element LD1B, and the source terminal is connected between the cathode of the light emitting element LD1B and the anode of the light emitting element LD2B. The drain terminal of the FET 52B is connected between the cathode of the light emitting element LD1B and the anode of the light emitting element LD2B, and the source terminal is connected between the cathode of the light emitting element LD2B and the anode of the light emitting element LD3B. In the FET 53B, the drain terminal is connected between the cathode of the light emitting element LD2B and the anode of the light emitting element LD3B, and the source terminal is connected to the cathode of the light emitting element LD3B. When a voltage for turning on the FET 51B is applied from the control unit 10, the drive current bypasses the light emitting element LD1B, and when a voltage for turning on the FET 52B is applied from the control unit 10, the drive current bypasses the light emitting element LD2B. Then, when a voltage for turning on the FET 53B is applied from the control unit 10, the drive current bypasses the light emitting element LD3B.

The detour circuit 90C includes FETs 51C to 53C. In the FET 51C, the drain terminal is connected to the anode of the light emitting element LD1C, and the source terminal is connected between the cathode of the light emitting element LD1C and the anode of the light emitting element LD2C. The drain terminal of the FET 52C is connected between the cathode of the light emitting element LD1C and the anode of the light emitting element LD2C, and the source terminal is connected between the cathode of the light emitting element LD2C and the anode of the light emitting element LD3C. In the FET 53C, the drain terminal is connected between the cathode of the light emitting element LD2C and the anode of the light emitting element LD3C, and the source terminal is connected to the cathode of the light emitting element LD3C. When a voltage for turning on the FET 51C is applied from the control unit 10, the drive current bypasses the light emitting element LD1C, and when a voltage for turning on the FET 52C is applied from the control unit 10, the drive current bypasses the light emitting element LD2C. Then, when a voltage for turning on the FET 53C is applied from the control unit 10, the drive current bypasses the light emitting element LD3C.

The laser device 1F has a configuration in which the number of sets of the light emitting element train, the bypass circuit, the voltage detection unit, the current sensor, the FET, the operational amplifier, the thermistor, and the AD conversion unit is 3, but the number of these sets is 4 or more. That is, the configuration may have four or more rows of light emitting elements.

FIG. 14 is a flowchart showing a flow of processing for determining the state of the light emitting element included in the light emitting element row in the laser device 1E. The processing of FIG. 14 is performed for each light emitting element row. The flowchart shown in FIG. 14 is different from the flowchart of FIG. 11 in that step S412 is not provided and step S414 is provided instead of step S413. When the control unit 10 determines that the selected light emitting element state is a short-circuit state, an open state, or an output reduction state, that is, a failure state, the control unit 10 controls the drive current of each light emitting element row in step S414. Hereinafter, the process performed in step S414 will be described.

Specifically, when the selected light emitting element is in the open state, the control unit 10 transfers the current flowing through the light emitting element row including the selected light emitting element to the light emitting element row not including the selected light emitting element. Sort to. For example, when the control unit 10 determines that any of the light emitting elements in the light emitting element row C1 is in the open state, the control unit 10 sets 1/2 of the target value of the drive current flowing through the light emitting element row C1 to the driving current flowing through the light emitting element row C2. Is added to the target value of, and 1/2 of the target value of the drive current flowing through the light emitting element train C1 is added to the target value of the drive current flowing through the light emitting element train C3. Next, the control unit 10 controls the voltage applied to the gate terminal of the FET 50B and the voltage applied to the gate terminal of the FET 50C based on the changed target value, and the drive current flowing through the light emitting element row C2 and the light emitting element row. Increase the drive current flowing through C3. Further, the control unit 10 turns off the FET 50A and stops driving the light emitting element train C1.

Further, when, for example, the control unit 10 determines that any of the light emitting elements in the light emitting element row C1 is in the short-circuited state or the output reduced state, the control unit 10 determines the voltage applied to the light-emitting element determined to be in the short-circuited state or the output reduced state. Acquired based on the signal from the voltage detection unit 40A. For example, the control unit 10 acquires the reference voltage applied in the normal state for the light emitting element determined to be in the short-circuited state or the output reduced state, and obtains the voltage change amount which is the difference between the acquired reference voltage and the voltage applied in these states. calculate. The control unit 10 divides the calculated voltage change by the target current value to be passed through the light emitting element train C1, and the resistance value of the light emitting element in the short-circuited state or the output low state due to the change from the normal state to these states. Calculate the change in.

Next, the control unit 10 determines the current flowing through the light emitting element row C1 and the target flowing through the light emitting element row C1 when the constant current control is not performed in the short-circuited state or the output reduced state based on the calculated change in the resistance value. ΔIa, which is the difference from the current value of, is calculated. The control unit 10 sets the current value obtained by subtracting ΔIa from the target value of the current flowing through the light emitting element array C1 as a new target value of the current flowing through the light emitting element array C1. Further, the control unit 10 divides ΔIa by the number of light emitting element trains having no light emitting element in the failed state, and calculates ΔIb which is an increase in the current flowing through the light emitting element train having no light emitting element in the failed state. For example, when there is no light emitting element in the faulty state in the light emitting element row C2 and the light emitting element row C3, ΔIb becomes ΔIa / 2. The control unit 10 adds ΔIa / 2 to the target value of the current flowing through the light emitting element train C2, and adds ΔIa / 2 to the target value of the current flowing through the light emitting element train C3. Next, the control unit 10 controls the operational amplifiers 54A, 54B and 54C so that the voltage corresponding to the updated drive current of the target value is applied to the gate terminals of the FETs 50A, 50B and 50C.

In the laser device 1E, when it is determined that the selected light emitting element is in the output reduced state, the first output failure threshold value and the second output failure threshold value may be lowered for the light emitting element determined to be in the output reduced state.

Next, in the case of the laser device 1F, the process of determining the state of the light emitting element is the process of replacing step S413 with step S414 in the flowchart of FIG. 11, but the process of determining the open failure is the process of determining the state of the laser device 1E. Different from the case. In the case of the laser device 1F, the resistance values of the light emitting elements LD1A to LD3A, LD1B to LD3B, and LD1C to LD3C are stored in advance. For example, when the control unit 10 of the laser device 1F determines that the light emitting element selected in step S404 for the light emitting element row C1 is in the open state, the control unit 10 determines that the light emitting element row C1 including the selected light emitting element is in the open state. The resistance value of the light emitting element is subtracted, and the difference is taken as the change in the resistance value due to the change from the normal state to the failed state. Next, the control unit 10 bypasses the light emitting element in the open state in the bypass circuit 90A based on the calculated change in the resistance value, and when the constant current control is not performed, the current flowing in the light emitting element row C1 and the light emission. ΔIa, which is the difference from the target current value to be passed through the element train C1, is calculated. The control unit 10 sets the current value obtained by subtracting ΔIa from the target value of the current flowing through the light emitting element array C1 as a new target value of the current flowing through the light emitting element array C1. Further, the control unit 10 sets ΔIa = ΔIb, adds ΔIb to the target value of the current flowing through the light emitting element array C2, and adds ΔIb to the target value of the current flowing through the light emitting element array C3. Next, the control unit 10 controls the operational amplifiers 54A, 54B and 54C so that the voltage corresponding to the updated drive current of the target value is applied to the gate terminals of the FETs 50A, 50B and 50C.

If the current value of the drive current is increased, the temperature of the FET rises, and there is a risk that the FET will fail due to heating. In order to prevent FET failure due to heating, when controlling the drive current in step S414 in the laser device 1E and the laser device 1F, the drive current may be controlled in consideration of the temperatures of the FETs 50A to 50B. .. FIG. 15 is an example of a flowchart showing a processing flow when the drive current is controlled in consideration of the temperatures of the FETs 50A to 50C in step S414.

First, the control unit 10 determines whether the FETs 50A to 50C are of a type in which the temperature monotonically increases as the flowing current increases. This is because the FETs 50A to 50C have a type in which the temperature increases monotonically as the flowing current increases, and a type in which the relationship between the current value and the temperature is convex upward when the horizontal axis is the current value and the vertical axis is the temperature. This is because there is a type that looks like the following function. The control unit 10 stores data indicating this type of FET in advance, and determines the type of FETs 50A to 50C based on the stored data (step S501).

When the FETs 50A to 50C are of a type in which the temperature monotonically increases with an increase in the flowing current (YES in step S501), the control unit 10 calculates the above-mentioned ΔIa and ΔIb (step S502). The control unit 10 determines a target value of the drive current to be passed through each light emitting element train based on the calculated ΔIa and ΔIb, and controls the drive current so as to be the determined target value (step S503). Here, the control unit 10 sets, for example, ΔIb / 2 to the amount of increase in the current flowing through the light emitting element row in which there is no light emitting element in the failed state. Further, here, the control unit 10 calculates the temperature of the FETs 50A to 50C before changing the drive current based on the signals from the AD conversion units 41A to 41C, and stores the calculated temperature as the temperature of the FETs 50A to 50C.

Next, the control unit 10 determines from the measurement results of the current sensors 30A to 30C whether or not the drive current has changed after step S503 (step S504). When the drive current has not changed (YES in step S504), the control unit 10 stops driving the light emitting element (step S518). When the drive current has changed after step S503 (NO in step S504), the control unit 10 determines whether any of the measured current values of the drive current has reached a predetermined upper limit value (NO). Step S505). When any of the measured current values reaches the upper limit value of the drive current (YES in step S505), the control unit 10 stops driving the light emitting element (step S518).

When none of the measured current values has reached the upper limit of the drive current (NO in step S505), the control unit 10 acquires the temperatures of the FETs 50A to 50C based on the signals from the AD conversion units 41A to 41C (NO). Step S506). The control unit 10 compares the temperature acquired here with the temperatures of the FETs 50A to 50C stored before changing the drive current in step S503, and determines whether the temperature change exceeds 0, that is, whether the temperature has risen. (Step S507). When the temperature change exceeds 0 (YES in step S507), the control unit 10 sets the target value of the drive current based on the inverse ratio of the temperature rise amount (step S508). For example, when there is a failed light emitting element in the light emitting element row C1 and there is no failed light emitting element in the light emitting element rows C2 and C3, the ratio of the temperature rise of the light emitting element row C2 to the temperature rise of the light emitting element row C3 is 1: 1. If it is 2, the increase in the light emitting element row C2 and the increase in the light emitting element row C3 are set to 2: 1 with respect to the remaining increase in the current to be increased in the light emitting element rows C2 and C3.

The control unit 10 controls the drive current so that the drive current of each light emitting element row becomes the target value set in step S508 (step S509). Next, the control unit 10 determines from the measurement results of the current sensors 30A to 30C whether or not the drive current has changed after step S509 (step S510). When the drive current has not changed (YES in step S510), the control unit 10 stops driving the light emitting element (step S518). When the drive current has changed (NO in step S510), the control unit 10 determines whether the measured current value of the drive current has reached a predetermined upper limit value (step S511). When any of the measured current values reaches the upper limit value of the drive current (YES in step S511), the control unit 10 stops driving the light emitting element (step S518). When none of the measured current values has reached the upper limit of the drive current (NO in step S511), the control unit 10 returns to step S408.

When the control unit 10 determines NO in step S501 or NO in step S507, the control unit 10 acquires the temperatures of the FETs 50A to 50C based on the signals from the AD conversion units 41A to 41C, and acquires the order of the temperatures of the FETs 50A to 50C. (Step S512).

Next, the control unit 10 selects an FET that increases the drive current (step S513). Here, since the control unit 10 selects the FETs in descending order of temperature, first, the FET having the highest temperature is selected from the order of the temperatures acquired in step S512. When returning to step S513 at the judgment of step S517 described later, the FET which is the second in the descending order of temperature is selected, and when returning to step S513 again, the FET which is the third in descending order of temperature is selected and the FET is selected. Select in descending order of temperature.

Next, the control unit 10 increases the drive current of the selected FET by a predetermined increase amount (step S514). After step S514, the control unit 10 determines whether the light intensity output by the light emitting element trains C1 to C3 is the target value of the output specified by the operator based on the signal from the light intensity detection unit 80 (). Step S515).

When the intensity of the light output by the light emitting element trains C1 to C3 reaches the target value of the output specified by the operator, the control unit 10 shifts the processing flow to step S408 (YES in step S515). When the intensity of the light output by the light emitting element trains C1 to C3 does not reach the target value of the output specified by the operator (NO in step S515), the control unit 10 has an upper limit of the current value of the drive current of the selected FET. It is determined whether the value has been reached (step S516). When the current value of the drive current of the selected FET has not reached the upper limit value (NO in step S516), the control unit 10 shifts the processing flow to step S514.

When the current value of the drive current of the selected FET has reached the upper limit value (YES in step S516), the control unit 10 determines whether the drive current of all the light emitting element trains has been increased (step S517). When the drive currents of all the light emitting element trains are not increased (NO in step S517), the control unit 10 returns to step S513 and then selects an FET for increasing the drive currents. When the drive currents of all the light emitting element trains are increased (YES in step S517), the control unit 10 stops the drive of the light emitting elements (step S518).

After step S509, the control unit 10 determines whether the light intensity output by the light emitting element trains C1 to C3 is the target value of the output specified by the operator based on the signal from the light intensity detection unit 80. However, when the measured light intensity exceeds the target value, the drive current of the light emitting element train having the largest drive current or the drive current of the light emitting element train driven by the FET having the highest temperature is lowered. PI control may be performed with the intensity as the target value.

Further, the control of the drive current performed in step S414 may be a process of the flowchart shown in FIG. In this case, the control unit 10 first calculates the above-mentioned ΔIa and ΔIb (step S601). The control unit 10 determines a target value of the drive current to be passed through each light emitting element train based on the calculated ΔIa and ΔIb, and controls the drive current so as to be the determined target value (step S602). Here, the control unit 10 sets, for example, ΔIb / 2 as the amount of increase in the current flowing through the light emitting element train that does not have the light emitting element in the failed state. Further, here, the control unit 10 calculates the temperature of the FETs 50A to 50C before changing the drive current based on the signals from the AD conversion units 41A to 41C, and stores the calculated temperature as the temperature of the FETs 50A to 50C.

Next, the control unit 10 determines from the measurement results of the current sensors 30A to 30C whether or not the drive current has changed after step S602 (step S603). When the drive current has not changed (YES in step S603), the control unit 10 stops driving the light emitting element (step S619). When the drive current has changed after step S602 (NO in step S603), the control unit 10 determines whether any of the measured current values of the drive current has reached a predetermined upper limit value (NO). Step S604). When any of the measured current values reaches the upper limit value of the drive current (YES in step S604), the control unit 10 stops driving the light emitting element (step S619).

When none of the measured current values has reached the upper limit of the drive current (NO in step S604), the control unit 10 acquires the temperatures of the FETs 50A to 50C based on the signals from the AD conversion units 41A to 41C (NO). Step S605). The control unit 10 compares the temperature acquired here with the temperatures of the FETs 50A to 50C stored before changing the drive current in step S602, and determines whether or not there is an FET whose temperature change is negative (step S606).

When there is no FET whose temperature change is negative (NO in step S606), the control unit 10 calculates and acquires the temperature of the FETs 50A to 50C based on the signals from the AD conversion units 41A to 41C, and obtains the temperature of the FETs 50A to 50C. The order of temperatures is acquired (step S607).

Next, the control unit 10 selects an FET that increases the drive current (step S608). Here, since the control unit 10 selects the FETs in ascending order of temperature, first, the FET having the lowest temperature is selected from the order of the temperatures acquired in step S607. When returning to step S608 based on the determination of step S612 described later, the second FET is selected in ascending order of temperature, and when returning to step S513 again, the third FET is selected in ascending order and the temperature of the FET is ascending. Select with.

The control unit 10 increases the drive current of the selected FET by a predetermined increase amount (step S609). After step S609, the control unit 10 determines whether the light intensity output by the light emitting element trains C1 to C3 has reached the output target value specified by the operator based on the signal from the light intensity detection unit 80. (Step S610).

When the intensity of the light output by the light emitting element trains C1 to C3 reaches the target value of the output specified by the operator, the control unit 10 shifts the processing flow to step S408 (YES in step S610). When the intensity of the light output by the light emitting element trains C1 to C3 does not reach the target value of the output specified by the operator (NO in step S610), the control unit 10 has an upper limit of the current value of the drive current of the selected FET. It is determined whether the value is exceeded (step S611). When the current value of the drive current of the selected FET has not reached the upper limit value (NO in step S611), the control unit 10 shifts the processing flow to step S609.

When the current value of the drive current of the selected FET has reached the upper limit value (YES in step S611), the control unit 10 determines whether the drive currents of all the light emitting element trains have been increased (step S612). When the drive currents of all the light emitting element trains are not increased (NO in step S612), the control unit 10 returns to step S608 and then selects the FET for increasing the drive currents. When the drive currents of all the light emitting element trains are increased (YES in step S612), the control unit 10 stops driving the light emitting elements (step S619).

When there is an FET whose temperature change is negative (YES in step S606), the control unit 10 calculates and acquires the temperature of the FETs 50A to 50C based on the signals from the AD conversion units 41A to 41C, and obtains the FETs 50A to 50C. The order of temperatures is acquired (step S613).

Next, the control unit 10 selects an FET that increases the drive current (step S614). Here, for example, the control unit 10 can select the FETs in descending order of temperature among the FETs whose temperature change with respect to the current is negative. When the temperature change of any of the FETs is negative, first, the FET having the highest temperature is selected from the order of the temperatures acquired in step S613. When returning to step S614 at the judgment of step S618 described later, the second FET is selected in descending order of temperature, and when returning to step S614 again, the third FET is selected in descending order, and the descending order of the FET temperature. Select with. If the temperature change of any one or more FETs is negative and the temperature change of the other one or more FETs is positive, the temperature of the FETs that initially had a negative temperature change with respect to the current is the highest. Select a high FET. When the process returns to step S614 based on the determination in step S618 described later, the second FET is selected in descending order of temperature among the FETs whose temperature change with respect to the current is negative. When all the FETs having a negative temperature change with respect to the current reach the upper limit of the drive current, the FET having the lowest temperature among the FETs having a positive temperature change with respect to the current is selected. After that, when the process returns to step S614 based on the determination in step S618 described later, the second FET is selected in ascending order of temperature among the FETs whose temperature change with respect to the current is positive. The upper limit of the driving current of the FET whose temperature change with respect to the current is negative can be determined, for example, according to the performance of the circuit component (for example, the upper limit of the voltage of the operational amplifiers 54A, 54B and 54C), and the temperature with respect to the current. The upper limit of the driving current of the FET whose change is positive can be determined from the upper limit of the temperature of the FET and the like. Therefore, the upper limits of these drive currents may be different.

The control unit 10 increases the drive current of the selected FET by a predetermined increase amount (step S615). After step S615, the control unit 10 determines whether the light intensity output by the light emitting element trains C1 to C3 has reached the output target value specified by the operator based on the signal from the light intensity detection unit 80. (Step S616).

When the intensity of the light output by the light emitting element trains C1 to C3 reaches the target value of the output specified by the operator, the control unit 10 shifts the processing flow to step S408 (YES in step S616). When the intensity of the light output by the light emitting element trains C1 to C3 does not reach the target value of the output specified by the operator (NO in step S616), the control unit 10 has an upper limit of the current value of the drive current of the selected FET. It is determined whether the value has been reached (step S617). When the current value of the drive current of the selected FET has not reached the upper limit value (NO in step S617), the control unit 10 shifts the processing flow to step S615.

When the current value of the drive current of the selected FET has reached the upper limit value (YES in step S617), the control unit 10 determines whether the drive current of all the light emitting element trains has been increased (step S618). When the drive currents of all the light emitting element trains are not increased (NO in step S618), the control unit 10 returns to step S614 and then selects an FET for increasing the drive currents. When the drive currents of all the light emitting element trains are increased (YES in step S618), the control unit 10 stops the drive of the light emitting elements (step S619).

In the flowchart shown in FIG. 16, it is determined after step S604 whether the FETs 50A to 50C are of a type in which the temperature monotonically increases as the flowing current increases, and the temperature monotonously increases as the flowing current increases. In the case of the type, the processing flow may be shifted to step S607.

Further, the control of the drive current performed in step S414 may be a process of the flowchart shown in FIG. In this case, the control unit 10 first determines whether the FETs 50A to 50C are of a type in which the temperature monotonically increases as the flowing current increases. The control unit 10 stores data indicating this type of FET in advance, and determines the type of FETs 50A to 50C based on the stored data (step S701).

When the FETs 50A to 50C are of a type in which the temperature monotonically increases with an increase in the flowing current (YES in step S701), the control unit 10 calculates the above-mentioned ΔIa and ΔIb (step 702). The control unit 10 determines a target value of the drive current to be passed through each light emitting element train based on the calculated ΔIa and ΔIb, and controls the drive current so as to be the determined target value (step 703). Here, the control unit 10 sets, for example, ΔIb / 2 as the amount of increase in the current flowing through the light emitting element train that does not have the light emitting element in the failed state.

Next, the control unit 10 determines from the measurement results of the current sensors 30A to 30C whether or not the drive current has changed after step S703 (step S704). When the drive current has not changed (YES in step S704), the control unit 10 stops driving the light emitting element (step S717). When the drive current has changed after step S703 (NO in step S704), the control unit 10 determines whether the measured current value of the drive current has reached a predetermined upper limit value (step S705). .. When the measured current value of the drive current reaches the upper limit value (YES in step S705), the control unit 10 stops driving the light emitting element (step S717).

When none of the measured current values has reached the upper limit value (NO in step S705), the control unit 10 acquires the temperatures of the FETs 50A to 50C based on the signals from the AD conversion units 41A to 41C (step S706). .. The control unit 10 calculates the average temperature of the FETs 50A to 50C, and controls the drive current so that the average temperature of the FETs, which is the maximum temperature, is + α (step S707). Here, α is, for example, 1 ° C., but is not limited to 1 ° C. Next, the control unit 10 controls the FET having the lowest temperature so that the intensity of the light output by the light emitting element trains C1 to C3 becomes the target value of the output specified by the operator, and drives the FET. PI control is performed on the drive current of the light emitting element train (step S708).

Next, the control unit 10 determines whether or not the drive current has changed after step S708 (step S709). If the drive current has not changed after step S708 (YES in step S709), the control unit 10 stops driving the light emitting element (step S717). When the drive current has changed after step S708 (NO in step S709), the control unit 10 determines whether the measured current value of the drive current has reached a predetermined upper limit value (step S710). .. When the measured current value of the drive current reaches the upper limit value (YES in step S710), the control unit 10 stops driving the light emitting element (step S717). When the measured current value of the drive current does not reach the upper limit value (NO in step S710), the control unit 10 returns to step S408.

When the control unit 10 determines NO in step S701, the control unit 10 acquires the temperatures of the FETs 50A to 50C based on the signals from the AD conversion units 41A to 41C, and acquires the order of the temperatures of the FETs 50A to 50C (step S711).

Next, the control unit 10 selects an FET that increases the drive current (step S712). Here, since the control unit 10 selects the FETs in ascending order of temperature, first, the FET having the lowest temperature is selected from the order of the temperatures acquired in step S712. When the process returns to step S712 at the judgment of step S716 described later, the FET which is the second in the ascending order of temperature is selected, and when returning to step S712 again, the FET which is the third in the ascending order of temperature is selected and the FET is selected. Select in ascending order of temperature.

The control unit 10 increases the drive current of the selected FET by a predetermined increase amount (step S713). After step S713, the control unit 10 determines whether the light intensity output by the light emitting element trains C1 to C3 is the target value of the output specified by the operator based on the signal from the light intensity detection unit 80 (). Step S714).

When the intensity of the light output by the light emitting element trains C1 to C3 reaches the target value of the output specified by the operator, the control unit 10 shifts the processing flow to step S408 (YES in step S714). When the intensity of the light output by the light emitting element trains C1 to C3 does not reach the target value of the output specified by the operator (NO in step S714), the control unit 10 sets the temperature of the selected FET from the AD conversion unit. It is acquired based on the signal, and it is determined whether the acquired temperature has reached a predetermined upper limit value (step S715). When the temperature of the selected FET has not reached a predetermined upper limit value (NO in step S715), the control unit 10 shifts the processing flow to step S713. When the temperature of the selected FET reaches a predetermined upper limit value (YES in step S715), the control unit 10 determines whether the drive currents of all the light emitting element trains have been increased (step S716). When the drive currents of all the light emitting element trains are not increased (NO in step S716), the control unit 10 returns to step S713 and then selects the FET for increasing the drive currents. When the drive currents of all the light emitting element trains are increased (YES in step S716), the control unit 10 stops the drive of the light emitting elements (step S717).

The control unit 10 controls the FET having the lowest temperature in step S708, and when the drive current supplied by this FET exceeds the upper limit, that is, when it is determined as YES in step S710, the light emitting element If the drive is stopped but YES is determined in step S710, another FET excluding the hottest FET and the coldest FET is selected, and the light emitting element train driven by the selected FET is driven. The current may be controlled by PI. For example, in this case, the control unit 10 may select the FET in the order following the FET having the lowest temperature in the ascending order of the temperature and control the drive current by PI.

According to the fifth embodiment shown above, the drive current of each light emitting element row can be controlled according to the state of failure. Therefore, for example, each failure occurs while waiting for repair such as replacement of the light emitting element. The light output of the laser device can be maintained according to the state of. Further, by controlling the drive current according to the temperature of each FET, it is possible to maintain the optical output of the laser device even when a failure occurs while reducing the possibility of inducing a new failure.

[Modification example]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be implemented in various other embodiments. For example, the present invention may be carried out by modifying the above-described embodiment as follows. The above-described embodiment and the following modifications may be combined with each other. The present invention also includes a configuration in which the components of each of the above-described embodiments and modifications are appropriately combined. Further, further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspect of the present invention is not limited to the above-described embodiments and modifications, and various modifications can be made.

In the above-described embodiment, the following configuration is adopted in order to prevent the voltage when noise is added to the line connecting the AD conversion units 40a to 40D and the light emitting elements LD1 to LD3 for determining the failure. You may. For example, taking the light emitting element LD1 as an example, when determining the short-circuit state, the control unit 10 determines that the short-circuit state is obtained when the voltage Vak1 continues to be equal to or lower than the short-circuit threshold value for a predetermined time. May be good. Further, when determining the open state, the control unit 10 may determine that the open state is in the open state if the voltage Vak1 continues to be equal to or higher than the open threshold value for a predetermined time. Further, when the control unit 10 determines the output reduction state, the short-circuit threshold value <voltage Vak1 ≤ first output failure threshold value or the second output failure threshold value ≤ voltage Vak1 <open threshold value exceeds a predetermined time. , It may be determined that the output is in a reduced state. In other words, it can be said that the control unit 10 determines the failure state when the state in which the voltage Vak1 is out of the normal range determined by the drive current exceeds a predetermined time. According to this configuration, the voltage of noise generated in a short period of time is not used for determining the state, and erroneous determination can be prevented.

In the present invention, the control unit 10 stores the reference voltage applied to the light emitting element when there is no failure in the table for each drive current, and measures the difference between the measured voltages Vak1, voltage Vak2 and voltage Vak3 and the reference voltage. The state of the light emitting elements LD1 to LD3 may be determined using the absolute value. In this case, the control unit 10 stores a first threshold value for determining the short-circuited state or the open state and a second threshold value having a value smaller than the first threshold value for determining the output reduction state. For example, when the absolute value of the difference between the voltage Vak1 and the reference voltage is equal to or greater than the first threshold value, the control unit 10 determines that the light emitting element LD1 is in the short-circuited state or the open state, and determines that the voltage Vak1 and the reference voltage are used. When the absolute value of the difference is equal to or greater than the second threshold value and less than the first threshold value, it may be determined that the light emitting element LD1 is in the output reduction state.

In the above-described embodiment, the drive current is controlled by controlling the voltage applied to the gate terminal of the FET 50, but the drive current may be controlled by a PWM (Pulse Width Modulation) method. In the configuration in which the drive currents of the laser devices 1A, 1B, and 1D are controlled by the PWM method, the drain terminal is connected to the power supply unit 20, the gate terminal is connected to the control unit 10, and the source terminal is smoothed instead of the FET 50. It has a FET connected to the circuit. The smoothing circuit is composed of an LC circuit, the input end of the LC circuit is connected to the source terminal of the FET, and the output end of the LC circuit is connected to the anode of the light emitting element LD1. The cathode of the freewheeling diode is connected between the FET and the smoothing circuit, and the anode of the freewheeling diode is grounded. The control unit 10 outputs a PWM signal having a duty ratio corresponding to the target drive current to control the drive current.

1A, 1B, 1D, 1E, 1F Laser device 10 Control unit 20 Power supply unit 30, 30A to 30C Current sensor 40, 40A, 40B, 40C Voltage detection unit 40a to 40d AD conversion unit 41A to 41C AD conversion unit 50, 50A to 50C, 51-53 FET
54A to 54C Operational amplifier 55A to 55C Thermistor 60 Display unit 70 Operated unit 80 Light intensity detection unit 90, 90A to 90C Bypass circuit 101 Voltage measurement unit 102 Judgment unit 103 Notification unit 104 Current measurement unit 105 Current control unit 106 Strength measurement unit 107 Detour control unit LD1 to LD3, LD1A to LD3A, LD1B to LD3B, LD1C to LD3C light emitting element

Claims (17)

A current control unit that controls the drive current supplied to the light emitting element,
A voltage measuring unit that measures the voltage applied to the light emitting element driven by the supplied drive current, and
A determination unit that determines a failure state of the light emitting element based on a voltage difference between a plurality of determination voltages determined from the drive current and a voltage measured by the voltage measurement unit.
A failure determination device for a light emitting element. The failure determination device for a light emitting element according to claim 1, wherein the determination unit determines a plurality of states including a state in which the intensity of light output by the light emitting element is lower than that in a normal state. The light emitting element according to claim 2, wherein the determination unit determines a short circuit failure, an open failure, and an output failure in which the intensity of the light output by the light emitting element is lower than that in the normal state, based on the voltage difference. Failure judgment device. If the voltage measured by the voltage measuring unit is smaller than the short-circuit threshold value determined by the drive current, it is determined as a short-circuit failure.
When the voltage measured by the voltage measuring unit is larger than the open threshold value determined from the drive current, it is determined as an open failure.
The failure determination device for a light emitting element according to claim 3, wherein if the voltage measured by the voltage measuring unit is within the output failure range determined by the drive current, it is determined to be an output failure. It has an optical measuring unit that measures the intensity of light output by the light emitting element.
When the intensity measured by the light measuring unit is equal to or less than a predetermined intensity threshold value lower than the normal light intensity output by the light emitting element when the driving current is supplied, the determination unit fails the light emitting element. The failure determination device for a light emitting element according to any one of claims 1 to 4, wherein the state of the light emitting element is determined. When the intensity measured by the optical measuring unit is equal to or less than the predetermined intensity threshold value, the current control unit reduces the driving current to a predetermined current value.
The failure determination device for a light emitting element according to claim 5, wherein the determination unit determines a state of failure of the light emitting element after the current control unit reduces the drive current to the predetermined current value. The determination unit determines a failure state of the light emitting element when the voltage measured by the voltage measurement unit is out of a predetermined range determined from the drive current exceeds a predetermined time. The failure determination device for the light emitting element according to any one of claims 6. A plurality of the light emitting elements are connected in series, and the plurality of light emitting elements are connected in series.
The determination unit determines the state of failure of each of the light emitting elements, and determines the state of failure of each of the light emitting elements.
The current control unit increases the drive current supplied to the light emitting element when at least one of the plurality of light emitting elements is determined to be a failure by the determination unit. The failure determination device for the light emitting element according to item 1. A plurality of the light emitting elements are connected in series, and the plurality of light emitting elements are connected in series.
Each of the light emitting elements is provided with a detour circuit for diverting the supplied current to the light emitting element in the subsequent stage.
The failure determination device for a light emitting element according to any one of claims 2 to 8, wherein the light emitting element determined to be a failure is such that the drive current is bypassed by the bypass circuit according to the state of the failure. Having a plurality of light emitting element trains in which a plurality of the light emitting elements are connected in series,
When there is a light emitting element determined to be a failure by the determination unit, the current control unit reduces the drive current supplied to the light emitting element train including the light emitting element determined to be a failure, and reduces the driving current to be determined to be a failure. The failure determination device for a light emitting element according to claim 1, which increases the drive current supplied to the light emitting element train that does not include the light emitting element. A drive element that supplies the drive current to each of the plurality of light emitting element rows is provided.
It has a temperature measuring unit for measuring the temperature of the driving element for each of the plurality of light emitting element rows.
The current control unit controls the drive current supplied to the light emitting element train that does not include the light emitting element determined to be a failure according to the temperature of the drive element measured by the temperature measuring unit. 10. The failure determination device for a light emitting element. The current control unit acquires a target value of the light intensity output from the plurality of light emitting element trains, and determines the light emitting element as a failure by the determination unit so that the light intensity becomes the target value. The eleventh aspect of claim 11 is to reduce the drive current supplied to the light emitting element train including the light emitting element and increase the drive current supplied to the light emitting element train not including the light emitting element determined to be a failure by the determination unit. The failure determination device for the light emitting element described. The current control unit supplies the drive current to the light emitting element train that does not include the light emitting element determined to be a failure by the determination unit, and the height of the temperature measured by the temperature measuring unit. The failure determination device for a light emitting element according to claim 12, which is controlled in order according to the above. The failure determination device for a light emitting element according to claim 13, wherein the current control unit starts control of the drive element in the next order when the temperature of the drive element measured by the temperature measurement unit reaches a threshold value. .. The current control unit evenly increases the drive current supplied to the light emitting element train that does not include the light emitting element determined to be faulty, and then supplies the drive current to the light emitting element train. Among them, the driving current supplied by the driving element having the highest temperature measured by the temperature measuring unit is reduced so that the intensity of light output by the plurality of light emitting element trains becomes the target value. When the drive current measured by the temperature measuring unit is controlled and the drive current supplied by the drive element having the lowest temperature reaches a threshold value, the drive element having the highest temperature and the drive element having the lowest temperature are said to have the lowest temperature. The failure determination device for a light emitting element according to claim 12, which controls other driving elements other than the driving element. Light emitting element and
The failure determination device for a light emitting element according to any one of claims 1 to 15.
A light emitting device equipped with. A voltage measurement step that measures the voltage applied to the light emitting element driven by the supplied drive current, and
A determination step for determining a failure state of the light emitting element based on a voltage difference between a plurality of determination voltages determined from the drive current and the voltage measured in the voltage measurement step.
A method for determining a failure of a light emitting element.

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