JP7048434B2 - Lighting equipment - Google Patents

Description

The present invention relates to a technique for improving safety in a lighting device using a semiconductor light emitting device.

Japanese Patent No. 5122542 (Patent Document 1) describes a semiconductor laser element that oscillates coherent laser light, an optical conversion member that converts the laser light into incoherent light and emits the light, and the semiconductor laser element and the above. It is arranged on an extension of the line connecting the light conversion member on the light conversion member side, and the light detector that detects the intensity of the laser light and the detection output of the light detector are compared with the reference value. Described is a light emitting device including a determination unit for determining the emission of the laser light to the outside, the light detector, and a safety device for suppressing the emission of the laser light to the outside. According to this conventional technique, it is possible to suppress the emission of coherent light to the outside even when an abnormality such as a defect of the light conversion member occurs, so that the safety of the light emitting device can be enhanced.

By the way, in the above-mentioned prior art, the intensity of light from the light conversion member is detected by a photodetector, and the emission of laser light to the outside is suppressed according to the magnitude of the light, but the light incident from the outside is suppressed. When (background light) has a relatively high intensity, there is a disadvantage that it is affected by it. Regarding this point, Patent Document 1 also includes a technique in which a monitor sensor is provided at a position where external light is incident at a position where light from an optical conversion member is not incident, and the influence of external light is canceled by using this output. Have been described.

However, in the above-mentioned conventional technique, since a monitor sensor is provided in addition to the photodetector, there is a disadvantage that more installation space is required and the miniaturization of the device is hindered. In addition, the operating principle is to compare the difference between the light intensity received by the photodetector and the light intensity received by the monitor sensor with a predetermined threshold value, but in reality, it does not depend on the incident angle of the light or the like. In order to keep the difference constant, there is an inconvenience that restrictions increase in the design of the optical system.

Japanese Patent No. 5122542

One of the specific aspects of the present invention is to provide a technique capable of ensuring safety without hindering the miniaturization of the lighting device and without increasing the restrictions on the optical system.

One aspect of the lighting device according to the present invention is (a) a lighting device including a light emitting circuit and a light receiving circuit, and (b) the light emitting circuit has (b1) an output unit for outputting first data and (b2). ) A modulation unit that modulates the first data by a method in which the average power is constant to generate a first signal, (b3) a drive unit that generates a drive current based on the first signal, and (b4) the above. It has a semiconductor light emitting element that emits a laser beam driven by a drive unit, and (c) the light receiving circuit has (c1) a light receiving unit that receives reference light generated by the laser light and generates an electric signal. , (C2) a high-pass filter that removes a DC component from the electric signal to generate a second signal, (c3) a demodulator that demolishes the second signal to generate second data, and (c4) the first. The lighting device includes an error detection unit that outputs a fault signal for stopping the operation of the semiconductor light emitting element to a light emitting circuit when the data and the first data do not match.

According to the above configuration, it is possible to ensure safety without hindering the miniaturization of the lighting device and without increasing restrictions on the optical system.

FIG. 1 is a diagram showing a configuration of a lighting device according to an embodiment. FIG. 2A is a waveform diagram showing a drive current supplied to the light emitting element by the drive unit, and FIG. 2B is an electric signal (pulse signal) obtained from the light receiving element via the conversion unit and the high-pass filter. ) Is a waveform diagram. FIG. 3 is a flowchart showing the flow of operations in the first mode and the second mode in the lighting device. FIG. 4 is a diagram showing a configuration of a lighting device of a modified example.

FIG. 1 is a diagram showing a configuration of a lighting device according to an embodiment. The illustrated lighting device is used, for example, as a vehicle lamp, and includes a light emitting circuit 100, an optical fiber 102, a phosphor (light conversion unit) 103, a light receiving circuit 101, and a lens 104. In this lighting device, the blue laser light emitted from the light emitting circuit 100 is guided to the phosphor 103 by the optical fiber 102 to be converted into light having a different wavelength (preferably white light), and this light is condensed by the lens 104. It irradiates the outside as illumination light. The light receiving circuit 101 detects the presence or absence of an abnormality such as dropping of the phosphor 103 (that is, an abnormality of the irradiation light) by receiving a part of the light emitted from the phosphor 103 as reference light, and when necessary. Is for stopping the operation of the light emitting circuit 100. One end of the optical fiber 102 is arranged so as to correspond to the emission surface of the light emitting element 6, and the laser light emitted from the light emitting element 6 is transmitted to the phosphor 103. When the phosphor 103 is irradiated with the blue laser light emitted from the other end side of the optical fiber 102, the phosphor 103 converts the blue laser light into white light.

The light emitting circuit 100 includes a control unit 1, a data generation unit 2, a coding unit 3, a modulation unit 4, a drive unit 5, and a light emitting element 6. In this embodiment, the data generation unit 2 and the coding unit 3 correspond to the "output unit".

The control unit 1 controls the overall operation of the light emitting circuit 100, and is configured by using, for example, a microcomputer.

The data generation unit 2 generates binary sequence data. The sequence data generated here is preferably an arbitrary sequence that is different each time, and may be, for example, sequence data generated using a random number sequence.

The coding unit 3 encodes the sequence data generated by the data generation unit 2 by an error-detectable method. As the error detection method, for example, a cyclic redundancy check (CRC) method can be used. In this case, the coding unit 3 divides the sequence data generated by the data generation unit 2 by a predetermined generation polynomial, and adds the remainder as inspection data. The sequence data encoded by the coding unit 3 is hereinafter referred to as "encoded data (first data)".

The modulation unit 4 modulates the coded data generated by the coding unit 3 to generate an electric signal. In this embodiment, a modulation method is used in which the average power of the electric signal obtained after modulation is constant regardless of the pattern of the coded data. As such a modulation method, for example, a pulse position modulation method (PPM: Pulse Position Modulation), a frequency shift keying method (FSK: Frequency Shift Keying), or the like can be used. For example, in this embodiment, the pulse position modulation method is used.

The drive unit 5 generates drive power having a pulse corresponding to the electric signal obtained by being modulated by the modulation unit 4 and supplies it to the light emitting element 6.

The light emitting element 6 is a semiconductor light emitting element (laser element), and emits laser light by receiving drive power from the drive unit 5. For example, in the present embodiment, a laser diode that emits a blue laser beam is used as the light emitting element 6.

The light receiving circuit 101 includes a control unit 9, a light receiving element 10, a conversion unit 11, a high-pass filter 12, a demodulation unit 13, and an error detection unit 14. In this embodiment, the light receiving element 10 and the conversion unit 11 correspond to the "light receiving unit".

The control unit 9 controls the overall operation of the light receiving circuit 101, and is configured by using, for example, a microcomputer.

The light receiving element 10 receives a part of the white light converted by the phosphor 103 and emitted as reference light, and generates a voltage or a current having a magnitude corresponding to the intensity thereof. As the light receiving element 10 of the present embodiment, one having sensitivity to light on the longer wavelength side than blue light is used. The light receiving element 10 is appropriately arranged in the vicinity of the phosphor 103. When an abnormality occurs in the phosphor 103, the intensity of the light incident on the light receiving element 10 decreases.

The conversion unit 11 converts the voltage or current generated by the light receiving element 10 into an electric signal indicating the intensity of the light received from the phosphor 103 by amplifying or the like.

The high-pass filter 12 generates an electric signal obtained by removing a low frequency component (particularly a DC component) from the electric signal generated by the conversion unit 11.

The demodulation unit 13 demodulates the electric signal (pulse signal) obtained through the high-pass filter 12 by the same method as that used in the modulation unit 4 to generate (restore) encoded data (second data).

The error detection unit 14 acquires the coded data generated (restored) by the demodulation unit 13, and detects the presence or absence of a data error using the error check data included in the coded data. Since the CRC method is used in the coding unit 3 in the present embodiment, the error detecting unit 14 divides the sequence data using the same generated polynomial used in the coding unit 3, and compares and collates the remainder. By doing so, the presence or absence of error or damage in the received coded data is detected. That is, if the coded data (first data) generated by the coding unit 3 and the coded data (second data) generated by the demodulation unit do not match, that fact is detected.

Then, when an error of a data error is detected by the error detection unit 14, the control unit 9 outputs a fault signal 15 for instructing "stop" to the light emitting circuit 100. When this fault signal 15 is input, the control unit 1 of the light emitting circuit 100 sends a command to the drive unit 5 to stop the supply of the drive power to the light emitting element 6. As a result, the light emitting element 6 is turned off.

According to such a configuration, a light receiving circuit installed at a position away from the light emitting circuit 100 by using one light receiving element without requiring high-speed data transmission between the light emitting circuit 100 and the light receiving circuit 101. The presence or absence of an abnormality in the phosphor 103 can be detected in the 101, and if there is an abnormality, the emission of the laser beam can be stopped promptly. Moreover, the influence of the background light can be eliminated.

By the way, the operation according to the above configuration is particularly effective when the output of the light emitting element 6 is stable, but the detection by the light receiving element 10 may become unstable when the output is unstable. Therefore, it is more preferable to provide two modes as the lighting modes as described below. A binary drive current is used in each lighting mode, and a state in which the drive current is high is referred to as a "mark state" and a state in which the drive current is low is referred to as a "non-mark state".

FIG. 2A is a waveform diagram showing a drive current supplied to the light emitting element by the drive unit, and FIG. 2B is an electric signal (pulse signal) obtained from the light receiving element via the conversion unit and the high-pass filter. ) Is a waveform diagram. The waveform diagram when the lighting mode is the first mode is shown on the left side of each figure, and the waveform diagram when the lighting mode is the second mode is shown on the right side of each figure.

In the first mode, the drive current ILD1 in the unmarked state is set to a value lower than the threshold current ILDTH of the light emitting element 6, and the drive current ILD2 in the marked state is set to a value higher than the threshold current ILDTH. In this first mode, the light emitting element 6 is turned off in the non-marked state, and the light emitting element is turned on in the marked state. At this time, the duty ratio during the non-marked state is set to a very low value (for example, 1/100 to 1/1000). Further, the drive current ILD2 in the marked state is also set to a relatively low value. As a result, the light emitting element 6 can emit light while sufficiently ensuring safety.

In the second mode, both the drive current ILD3 in the unmarked state and the drive current ILD4 in the marked state are set to higher values than the threshold current ILDTH. Further, both the drive current ILD3 and the drive current ILD4 are set to higher values than the drive current ILD2. In this second mode, the magnitudes of the drive currents ILD3 and the drive currents ILD4 are set so as to secure the intensity of the illumination light required for the illumination device. At this time, since the modulation is performed so that the average power of the drive current does not depend on the data pattern, the intensity of the illumination light can be constant regardless of the data pattern. Further, since the coded data is transmitted by the pulse position modulation method, it is based on the pulse position in each frame in the electric signal (pulse signal) obtained from the light receiving element 10 via the conversion unit 11 and the high pass filter 12. The coded data can be restored.

FIG. 3 is a flowchart showing the flow of operations in the first mode and the second mode in the lighting device. The operation of the lighting device after the start of lighting will be described with reference to this flowchart.

The light emitting circuit 100 lights (lights) the light emitting element 6 in the first mode (step S11). Specifically, the operation of the first mode is started by supplying the drive current corresponding to the first mode to the light emitting element 6 based on the command of the control unit 1.

The light receiving circuit 101 performs a process of establishing synchronization with the light emitting circuit 100 (step S12). Specifically, the demodulation unit 13 detects the timing required for demodulation based on the electric signal (pulse signal) obtained via the light receiving element 10, the conversion unit 11, and the high-pass filter 12, and demodulates based on the timing. A reproduction clock to be used is generated, and the pulse signal is demodulated using this reproduction clock. The reproduction clock required for demodulation is generated by, for example, a PLL (Phase Locked Loop) circuit provided in the demodulation unit 13.

Next, the light receiving circuit 101 determines whether or not synchronization is completed within a preset time (step S13). Specifically, the control unit 9 of the light receiving circuit 101 determines that the synchronization is completed when the desired reproduction clock is generated in time by the demodulation unit 13. At this time, if light is not incident on the light receiving element 10 due to a failure of the phosphor 103 or the like, a direct current no-signal voltage (see FIG. 2) is output from the light receiving element 10, so synchronization is completed. do not. Also. Even when sunlight or the like is incident on the light receiving element 10 from the outside, the light component is removed by the high-pass filter 12, so that the DC voltage when there is no signal is output in the same manner, so that the synchronization is not completed.

When the synchronization is completed within the time (step S13; YES), the control unit 9 of the light receiving circuit 101 sets the status of the fault signal 15 to “cancel stop” and outputs the signal to the light emitting circuit 100 (step S14). .. It is assumed that the fault signal 15 is set to the status instructing "stop" in the initial state.

When the fault signal 15 whose status is "stop release" is given, the light emitting circuit 100 turns on (lights) the light emitting element 6 in the second mode (step S15). Specifically, the data generation unit 2, the coding unit 3, the modulation unit 4, and the drive unit 5 each operate based on the command of the control unit 1 to supply the drive current corresponding to the second mode to the light emitting element 6. As a result, the operation of the second mode is performed.

When the operation of the second mode is started, the control unit 9 of the light receiving circuit 101 determines whether or not an error has been detected by the error detection unit 14 (step S16). If no error is detected (step S16; NO), the status of the fault signal 15 is not changed, so the process returns to step S15 described above, and the operation of the light emitting circuit in the second mode is continued. ..

When an error is detected (step S16; YES), the control unit 9 of the light receiving circuit 101 outputs a fault signal 15 having a status instructing "stop" to the light emitting circuit 100 (step S17). In this case, the process returns to step S11 described above, and the operation and synchronization processing in the first mode are executed again.

On the other hand, if the synchronization is not completed within the preset time in step S13 described above (step S13; NO), the control unit 9 of the light receiving circuit 101 sets the status of the fault signal 15 to "stop". In response to this, the light emitting circuit 100 turns off the light emitting element 6 (step S18). In this case, it is considered that some abnormality or failure has occurred in the phosphor 103, so that both the light emitting circuit 100 and the light receiving circuit 101 stop operating.

According to the above embodiment, since a plurality of light receiving elements are not required, the miniaturization of the device is not hindered, the restrictions on the design of the optical system are not increased, and the safety can be ensured. ..

The present invention is not limited to the contents of the above-described embodiment, and can be variously modified and carried out within the scope of the gist of the present invention. For example, in the above-described embodiment, a vehicle lamp is mentioned as an example of a lighting device, but the scope of application of the present invention is not limited to this.

Further, in the above-described embodiment, the data generation unit 2 of the light emitting circuit 100 is configured to generate different sequence data each time, but the same sequence may be generated each time. The configuration of this modification is shown in FIG. The same reference numerals are used for the configurations common to the above-described embodiments, and detailed description thereof will be omitted. In the case of this modification, since it is sufficient to input the fixed value sequence data from the data output unit 2a to the modulation unit 4, the data generation unit 2 and the coding unit 3 in the light emitting circuit 100 of the above-described embodiment are omitted. can do. Further, in the error detection unit 14 of the light receiving circuit 101, since the sequence data is a preset fixed value, the error detection unit 14 can detect the presence or absence of an error by a simple data comparison. Therefore, the circuit configuration can be further simplified.

1: Control unit 2: Data generation unit 3: Coding unit 4: Modulation unit 5: Drive unit, 6: Light emitting element, 9: Control unit, 10: Light receiving element, 11: Conversion unit, 12: High pass Filter, 13: demodulation unit, 14: error detection unit, 15: fault signal, 100: light emitting circuit, 101: light receiving circuit, 102: optical fiber, 103: phosphor, 104: lens

Claims (5)

A lighting device equipped with a light emitting circuit and a light receiving circuit.
The light emitting circuit
The output unit that outputs the first data and
A modulation unit that modulates the first data by a method in which the average power is constant to generate a first signal, and a modulation unit.
A drive unit that generates a drive current based on the first signal,
A semiconductor light emitting device that emits laser light driven by the driving unit,
Have,
The light receiving circuit is
A light receiving unit that receives the reference light generated by the laser beam and generates an electric signal,
A high-pass filter that removes a DC component from the electrical signal to generate a second signal,
A demodulation unit that demodulates the second signal to generate second data,
An error detection unit that outputs a fault signal for stopping the operation of the semiconductor light emitting element to the light emitting circuit when the second data and the first data do not match.
Has a lighting device. The output unit outputs the coded data obtained by encoding the sequence data by an error-detectable method as the first data.
The error detection unit outputs the fault signal assuming that the second data and the first data do not match when an error is detected by performing an error detection process based on the second data.
The lighting device according to claim 1. The output unit generates the sequence data based on a random number sequence.
The lighting device according to claim 2. The output unit outputs fixed-value sequence data as the first data.
The error detection unit outputs the fault signal assuming that the second data and the first data do not match when the first data and the second data demodulated by the demodulation unit are not the same. ,
The lighting device according to claim 1. Further including an optical conversion unit that converts the laser light emitted from the semiconductor light emitting element into light having a wavelength different from that of the laser light to generate the illumination light.
The light receiving unit of the light receiving circuit receives a part of the illumination light generated by the light conversion unit as the reference light.
The lighting device according to any one of claims 1 to 4.

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