JP2016058370A - Vehicle lighting fixture and abnormality detector of light source thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably detect abnormalities in a light source comprising a combination of a blue laser diode and a phosphor.SOLUTION: A light source 10 includes a laser diode 12 emitting excitation light 20 and a phosphor 14 excited by the excitation light 20 to emit fluorescence. A first photosensor 32 has a sensitivity to a wavelength of the excitation light 20, and receives a part of output light 24 to generate a first current in accordance with an amount of received light. A second photosensor 34 has a sensitivity to a wavelength of the fluorescence, and receives a part of the output light 24 to generate a second current in accordance with an amount of received light. A first current-voltage conversion circuit 36 outputs a first detection signal V1 in accordance with the voltage drop of a first resistor R1 provided on a path of the first current. A second current-voltage conversion circuit 38 outputs a second detection signal V2 in accordance with the voltage drop of a second resistor R2 provided on a path of the second current. A determination part 40 determines the presence or absence of abnormalities on the basis of the first detection signal V1 and the second detection signal V2.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a vehicular lamp used in an automobile or the like.

  Conventionally, halogen lamps and HID (High Intensity Discharge) lamps have been mainstream as light sources for vehicle lamps, particularly headlamps, but in recent years, semiconductor light sources such as LEDs (light emitting diodes) have been used instead. Vehicle lamps are being developed.

  In order to further improve the visibility, a vehicular lamp provided with a laser diode (also referred to as a semiconductor laser) and a phosphor instead of an LED is disclosed (for example, see Patent Document 1). In the technique described in Patent Document 1, ultraviolet light, which is excitation light emitted from a laser diode, is irradiated to a phosphor. The phosphor receives white light and generates white light. The white light generated by the phosphor is irradiated in front of the lamp, thereby forming a predetermined light distribution pattern. In the technique described in Patent Document 1, excitation light is not irradiated.

JP 2004-241142 A International Publication No. 10/070720 Pamphlet

  FIG. 1 is a cross-sectional view of a light source of a vehicular lamp studied by the present inventor. The light source 10 mainly includes a laser diode 12, a phosphor 14, an optical system 16, and a housing 18. The light source 10 is common to the technique of Patent Document 1 in that it includes a laser diode 12 and a phosphor 14.

  The laser diode 12 in FIG. 1 generates blue excitation light 20 instead of ultraviolet light. The excitation light 20 is collected on the phosphor 14 by the optical system 16. The optical system 16 is configured by a lens, a reflecting mirror, an optical fiber, or a combination thereof. The phosphor 14 that has received the blue excitation light 20 generates fluorescence 22 having a spectral distribution in a longer wavelength region (green to red) than the excitation light 20. The excitation light 20 applied to the phosphor 14 is scattered by the phosphor 14 and passes through the phosphor 14 in a state where coherence is lost. For example, the phosphor 14 is supported by being fitted into an opening provided in the housing 18.

  FIG. 2 is a diagram illustrating a spectrum of the output light 24 of the light source 10. The output light 24 of the light source 10 includes blue excitation light 20a that has passed through the phosphor 14 and green to red fluorescence 22 emitted from the phosphor 14, and has a spectral distribution of white light.

  That is, in the light source of Patent Document 1, excitation light that is ultraviolet light is not used as part of the emitted light that irradiates the front of the vehicle, whereas in the light source 10 of FIG. It is used as a part of the emitted light from the lighting.

  As a result of studying the light source 10 of FIG. 1, the present inventor has recognized the following problems. In the light source 10 of FIG. 1, when an abnormality such as the phosphor 14 is broken or the phosphor 14 is detached from the housing 18, the excitation light 20 generated by the laser diode 12 is strong without being scattered by the phosphor 14. It is dangerous because it is emitted directly in the state of coherence and is irradiated in front of the vehicle.

  The present invention has been made in such a situation, and one of exemplary purposes of an embodiment thereof is to provide a technique capable of reliably detecting an abnormality in a light source of a combination of a blue laser diode and a phosphor.

(First aspect)
One embodiment of the present invention relates to an abnormality detector for a light source. The light source includes a laser diode that emits excitation light and a phosphor that emits fluorescence when excited by the excitation light, and is configured to generate white output light including the excitation light and the fluorescence spectrum. The anomaly detector is sensitive to the first wavelength, substantially insensitive to the second wavelength, receives a part of the output light of the light source, and generates a first current corresponding to the amount of received light. A photosensor and a second photo that is sensitive to the second wavelength, substantially insensitive to the first wavelength, receives a part of the output light of the light source, and generates a second current according to the amount of received light A first current-voltage conversion circuit including a sensor, a first resistor provided on a path of the first current, and outputting a first detection signal corresponding to a voltage drop of the first resistance; and a path of the second current A second current-voltage conversion circuit that includes a second resistor provided and outputs a second detection signal corresponding to a voltage drop of the second resistor, and whether there is an abnormality based on the first detection signal and the second detection signal A determination unit for determining.

  The first detection signal changes linearly according to the amount of excitation light, and the inclination thereof is determined according to the resistance value of the first resistor. Similarly, the second detection signal changes linearly according to the amount of fluorescent light, and the inclination thereof is determined according to the resistance value of the second resistor. Here, when the phosphor is normal, the intensity of the excitation light, the intensity of the fluorescence, and the intensity of the white light that is the output of the light source are in a proportional relationship. Therefore, when the phosphor is normal, the ratio between the first detection signal and the second detection signal is substantially constant. However, when the phosphor is abnormal and the excitation light is directly emitted, the excitation included in the output light. The balance between light and fluorescence is lost, and the ratio between the first detection signal and the second detection signal changes. According to this aspect, by appropriately determining the resistance values of the first resistor and the second resistor and monitoring the first detection signal and the second detection signal, regardless of the intensity of white light, that is, the output of the light source, A phosphor abnormality can be detected easily and reliably.

When the first current when the phosphor is normal is I1, the second current is I2, the first current when the phosphor is abnormal is I1 ', and the second current is I2', the resistance of the first resistor The value R1 and the resistance value R2 of the second resistor are expressed by the relational expression R1 × I1 <R2 × I2 (1)
R1 × I1 ′> R2 × I2 ′ (2)
It may be determined to satisfy.
In this case, an abnormality can be detected by comparing the magnitudes of the first detection signal and the second detection signal.

  The determination unit may determine that the abnormality is detected when the magnitude relationship between the first detection signal and the second detection signal is reversed.

  The determination unit may include a voltage comparator.

The first current-voltage conversion circuit includes a first operational amplifier in which a first photosensor is connected to an inverting input terminal and a fixed voltage is applied to a non-inverting input terminal, and between the inverting input terminal and the output terminal of the first operational amplifier. And a first resistor provided in. The second current-voltage conversion circuit includes a second operational amplifier in which the second photosensor is connected to the inverting input terminal and a fixed voltage is applied to the non-inverting input terminal, and between the inverting input terminal and the output terminal of the second operational amplifier. And a second resistor provided in the.
In this configuration, the gain (current-voltage conversion) of the first current-voltage conversion circuit and the second current-voltage conversion circuit is determined only by the resistance values of the first resistor and the second resistor. As a result, an error factor can be eliminated, and a highly accurate abnormality can be detected.

Each of the first photosensor and the second photosensor may include a first photodiode and a second photodiode. The cathode of the first photodiode is connected to the inverting input terminal of the first operational amplifier, a fixed voltage is applied to the anode of the first photodiode, and the second photo amplifier is connected to the inverting input terminal of the second operational amplifier. A cathode of the diode is connected, and a fixed voltage may be applied to the anode of the second photodiode.
In this case, since no voltage is applied between the anode and cathode of the photodiode, light can be detected without being affected by dark current in a wide light quantity range.

  Each of the first photosensor and the second photosensor may include a first photodiode and a second photodiode. The anode of the first photodiode is connected to the inverting input terminal of the first operational amplifier, the cathode of the first photodiode is connected to the non-inverting input terminal of the first operational amplifier, and a predetermined fixed voltage is applied. The anode of the second photodiode is connected to the inverting input terminal of the second operational amplifier, the cathode of the second photodiode is connected to the non-inverting input terminal of the second operational amplifier, and a fixed voltage is applied. May be applied.

The determination unit may offset at least one of the first detection signal and the second detection signal in a direction in which they are separated from each other.
When the output of the light source is small, the first detection signal and the second detection signal are close to each other, and erroneous detection may occur due to the influence of noise. By introducing the offset, it is possible to suppress erroneous detection of abnormality when the light amount is small.

  The determination unit may include a voltage dividing circuit that divides the second detection signal. Thereby, an offset can be introduced with a simple configuration using only two resistors. At this time, when the output of the light source is larger than a predetermined value, the influence of setting the voltage dividing circuit, that is, the influence due to the introduction of the offset is suppressed, and the accuracy of abnormality detection can be maintained.

  Another aspect of the present invention relates to a vehicular lamp. A vehicular lamp includes a light source, one of the above-described abnormality detectors that detects abnormality of the light source, and a lighting circuit that drives the light source and executes predetermined protection processing when the abnormality detector detects abnormality. .

A plurality of abnormality detectors may be provided. The lighting circuit may execute a protection process when at least one abnormality detector detects an abnormality.
In this case, even if a failure occurs in any of the abnormality detectors, the abnormality of the light source can be detected by another current station detector, and appropriate protection processing can be executed.

(Second aspect)
Another aspect of the present invention also relates to an abnormality detector. The light source includes a laser diode that emits excitation light and a phosphor that emits fluorescence when excited by the excitation light, and is configured to generate white output light including the excitation light and the fluorescence spectrum. The abnormality detector includes a diffraction element that diffracts the output light of the light source, a photodetector that detects the diffracted light of the diffraction element, and a determination unit that determines whether there is an abnormality based on the detection result of the photodetector. .

  Since the excitation light is scattered by the phosphor when the phosphor is normal, the coherency of the excitation light input to the diffractive element is reduced, and therefore, the diffracted light obtained by the diffractive element is significantly No interference fringes are observed. On the other hand, when the phosphor is abnormal, the excitation light is not scattered and is input to the diffractive element in a coherent state, so that significant interference fringes are observed in the diffracted light obtained by the diffractive element. . Therefore, according to this aspect, the presence or absence of abnormality of the phosphor can be determined based on the diffracted light of the diffraction element.

  The photodetector detects the light intensity at two points: a first position where the diffracted light pattern has a peak when the phosphor is normal and a second position where the peak does not exist when the phosphor is normal. May be. The determination unit may determine whether there is an abnormality based on the light intensity at two points.

  The photodetector may include two photosensors provided at two points.

  The determination unit may determine that there is an abnormality when the difference between the outputs of the two photosensors exceeds a predetermined threshold value.

  The photodetector may have a plurality of pixels that receive diffracted light. The determination unit may determine the presence / absence of an abnormality based on a diffraction pattern measured by a plurality of pixels.

The determination unit may include a differentiator that spatially differentiates data measured by a plurality of pixels, and may determine whether there is an abnormality based on the output of the differentiator.
Thereby, the presence or absence of a significant diffraction pattern can be determined.

  Data from a plurality of pixels may be read sequentially. The differentiator may time-differentiate data from a plurality of pixels that are sequentially read out.

  The determination unit may determine that the output is abnormal when the output of the differentiator exceeds a predetermined threshold.

The abnormality detector may further include a pinhole provided between the diffraction element and the light source.
Thereby, a clear diffraction pattern can be obtained when the phosphor is abnormal.

  The light source and the abnormality detector may be used for a vehicular lamp. The vehicular lamp may include a reflector that reflects the output light of the light source, and a pinhole may be formed in the reflector.

  Another aspect of the present invention relates to a vehicular lamp. The vehicular lamp includes a light source and any one of the abnormality detectors described above that detects an abnormality of the light source.

  According to an aspect of the present invention, abnormality of the phosphor can be detected.

It is sectional drawing of the light source of the vehicle lamp which this inventor examined. It is a figure which shows the spectrum of the output light of a light source. It is a block diagram of a vehicular lamp provided with an abnormality detector according to the first embodiment. FIG. 4A is a diagram showing the relationship between the output light intensity and the first detection signal and the second detection signal when the phosphor is normal, and FIG. 4B is an abnormality of the phosphor. It is a figure which shows the relationship between output light intensity, a 1st detection signal, and a 2nd detection signal at the time. It is a circuit diagram which shows the abnormality detector which concerns on a 1st structural example. It is a circuit diagram which shows the abnormality detector which concerns on a 2nd structural example. FIG. 7A is a diagram showing the relationship between the output light intensity and the first detection signal and the second detection signal when the phosphor is normal, and FIG. 7B is an abnormality of the phosphor. It is a figure which shows the relationship between output light intensity, a 1st detection signal, and a 2nd detection signal at the time. FIG. 8A is a circuit diagram of an abnormality detector according to a third configuration example. FIG. 8B is a circuit diagram of the abnormality detector according to the fourth configuration example. FIG. 9A is a diagram showing the relationship between the output light intensity, the first detection signal, and the second detection signal when the phosphor is normal in the abnormality detector of FIG. 8A. FIG. 9B is a diagram showing the relationship between the output light intensity, the first detection signal, and the second detection signal when the phosphor is normal in the abnormality detector of FIG. 8B. It is a block diagram of the vehicle lamp which concerns on a 4th modification. FIG. 11A is an equivalent circuit diagram of a photodiode module including a photodiode pair, and FIG. 11B is a schematic cross-sectional view thereof. It is a block diagram of the vehicle lamp provided with the abnormality detector which concerns on 2nd Embodiment. FIG. 13A shows diffracted light when the phosphor is normal, and FIG. 13B shows diffracted light when the phosphor is abnormal. It is a figure which shows the vehicle lamp containing the abnormality detector which concerns on a 1st structural example. FIGS. 15A and 15B are circuit diagrams illustrating a specific configuration example of the determination unit. It is a circuit diagram which shows the abnormality detector which concerns on a 2nd structural example. FIG. 17A is a diagram showing the output of the photodetector and its differential data when the phosphor is abnormal, and FIG. 17B is the diagram of the photodetector when the phosphor is normal. It is a figure which shows an output and its differential data. It is a circuit diagram which shows the structural example of a determination part. It is a perspective view of a lamp unit provided with the vehicular lamp concerning an embodiment.

  The present invention will be described below based on preferred embodiments with reference to the drawings. The same or equivalent components, members, and processes shown in the drawings are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate. The embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

In this specification, “the state in which the member A is connected to the member B” means that the member A and the member B are electrically connected to each other in addition to the case where the member A and the member B are physically directly connected. It includes cases where the connection is indirectly made through other members that do not substantially affect the general connection state, or that do not impair the functions and effects achieved by their combination.
Similarly, “the state in which the member C is provided between the member A and the member B” refers to the case where the member A and the member C or the member B and the member C are directly connected, as well as their electric It includes cases where the connection is indirectly made through other members that do not substantially affect the general connection state, or that do not impair the functions and effects achieved by their combination.

  Further, in this specification, electrical signals such as voltage signals and current signals, or symbols attached to circuit elements such as resistors and capacitors indicate the respective voltage values, current values, resistance values, and capacitance values as necessary. It shall represent.

(First embodiment)
FIG. 3 is a block diagram of the vehicular lamp 1 including the abnormality detector 30 according to the first embodiment. The vehicular lamp 1 includes a light source 10, an abnormality detector 30 that detects an abnormality of the light source 10, and a lighting circuit 200.

  As described with reference to FIG. 1, the light source 10 includes the laser diode 12, the phosphor 14, and the optical system 16. The laser diode 12 emits excitation light 20. The laser diode 12 emits light with an intensity corresponding to a drive current from a drive circuit (not shown). The phosphor 14 is provided on the optical path of the excitation light 20 and is excited by the excitation light 20 to emit fluorescence 22. The light source 10 is configured to generate white output light 24 that includes a spectrum of excitation light 20 and fluorescence 22.

The lighting circuit 200 supplies a drive current _ILD to the laser diode 12 and causes the laser diode 12 to emit light. The configuration of the lighting circuit 200 is not particularly limited, and a known technique may be used.

  The abnormality detector 30 receives a part of the output light 24 and determines whether or not the light source 10 is abnormal, more specifically, whether or not the phosphor 14 is abnormal. Examples of the abnormality of the phosphor 14 include, but are not particularly limited to, cracking, detachment, and aging deterioration of the phosphor 14. When detecting the abnormality, the abnormality detector 30 asserts the abnormality detection signal S1 (for example, high level). When the abnormality detector 30 detects an abnormality, the lighting circuit 200 performs a predetermined protection process. Examples of the protection process include turning off the laser diode 12, reducing the luminance (light quantity), and notifying various higher-level ECUs (Electronic Control Units), but are not particularly limited.

The abnormality detector 30 includes a first photosensor 32, a second photosensor 34, a first current-voltage conversion circuit 36, a second current-voltage conversion circuit 38, and a determination unit 40. The first photosensor 32 is sensitive to the wavelength of the excitation light 20 and is substantially insensitive to the wavelength of the fluorescence 22. The first photosensor 32 receives a part of the output light 24 and generates a first current _ISC1 corresponding to the intensity of the excitation light 20 that has passed through the phosphor 14. On the other hand, the second photosensor 34 is sensitive to the wavelength of the fluorescence 22 and is substantially insensitive to the wavelength of the excitation light 20. The second photosensor 34 receives a part 24 of the output light 24 and generates a second current _ISC2 corresponding to the intensity of the fluorescence 22 emitted from the phosphor 14.

  The wavelength selectivity of sensitivity of each of the first photosensor 32 and the second photosensor 34 may be realized by a color filter, or may be realized by a semiconductor material or a device structure of the sensor. The first photosensor 32 and the second photosensor 34 are not particularly limited, and a semiconductor photosensor such as a photodiode or a phototransistor can be used. In the present embodiment, the first photosensor 32 and the second photosensor 34 include photodiodes.

The first current-voltage conversion circuit 36 includes a first resistor R1 provided on the path of the first current _ISC1 , and outputs a first detection signal V1 corresponding to the voltage drop _VSC1 of the first resistor R1. The first detection signal V1 changes linearly with a slope corresponding to the resistance value of the first resistor R1 with respect to the first current _ISC1 .

The second current-voltage conversion circuit 38 includes a second resistor R2 provided on the path of the second current _ISC2 , and outputs a second detection signal V2 corresponding to the voltage drop _VSC2 of the second resistor R2. The second detection signal V2 changes linearly with a slope corresponding to the resistance value of the second resistor R2 with respect to the second current _ISC2 .

  The determination unit 40 determines the presence / absence of an abnormality based on the first detection signal V1 and the second detection signal V2. When the determination unit 40 detects an abnormality, the determination unit 40 asserts the abnormality detection signal S1 (for example, high level). The basic configuration of the abnormality detector 30 has been described above. Next, the operation principle will be described.

  The first detection signal V1 changes linearly according to the light amount of the excitation light 20, and its inclination is determined according to the resistance value of the first resistor R1. Similarly, the second detection signal V2 changes linearly according to the light quantity of the fluorescence 22, and its inclination is determined according to the resistance value of the second resistor R2. Here, when the phosphor 14 is normal, the intensity of the excitation light 20, the intensity of the fluorescence 22, and the intensity of the output light 24 of the light source 10 are proportional to each other. Therefore, when the phosphor 14 is normal, the ratio of the first detection signal V1 and the second detection signal V2 takes a substantially constant value. On the other hand, if the phosphor 14 is abnormal and the excitation light 20 is directly emitted, the output The balance between the excitation light 20 and the fluorescence 22 contained in the light 24 is lost, and the ratio between the first detection signal V1 and the second detection signal V2 changes. According to the anomaly detector 30 of FIG. 3, by appropriately determining the resistance values of the first resistor R1 and the second resistor R2, and monitoring the first detection signal V1 and the second detection signal V2, the intensity of white light, That is, the abnormality of the phosphor 14 can be detected easily and reliably without depending on the output of the light source.

  FIG. 4A is a diagram showing the relationship between the output light intensity and the first detection signal V1 and the second detection signal V2 when the phosphor 14 is normal, and FIG. It is a figure which shows the relationship between output light intensity, the 1st detection signal V1, and the 2nd detection signal V2 when is abnormal.

When the phosphor 14 is normal, the first current I _SC1 at a certain output light intensity is I1, the second current I _SC2 is I2, and the first current I _SC1 when the phosphor 14 is abnormal is I1 ′, second The current _{ISC2 is set} to I2 ′. When an abnormality occurs in the phosphor 14, the intensity of the fluorescence 22 decreases, and the excitation light 20 passes through without being absorbed by the fluorescence 22, so that I1 ′> I1 and I2 ′ <I2. At this time, it is desirable that the resistance value of the first resistor R1 and the resistance value of the second resistor R2 are determined so as to satisfy the following relational expression.
R1 × I1 <R2 × I2 (1)
R1 × I1 ′> R2 × I2 ′ (2)

The abnormality detector 30 compares the magnitude relationship between the first detection signal V1 and the second detection signal V2, and determines that the condition is abnormal when the magnitude relationship is inverted. The process of the abnormality detector 30 is based on the ratio I _SC1 / I _SC2 between the detection current I _SC1 of the first photosensor 32 and the detection current I _SC2 of the second photosensor 34, and the ratio between the first resistance R1 and the second resistance R2. This is equivalent to comparing with the resistance ratio R2 / R1. The abnormality detector 30 can determine that an abnormality has occurred when the ratio I _SC1 / I _SC2 of the intensity of the blue excitation light 20 and the intensity of the yellow fluorescence exceeds a predetermined determination value (R2 / R1).

  The scope of the present invention extends to various circuits grasped as the block diagram of FIG. 3, but a specific configuration example will be described below.

(First configuration example)
FIG. 5 is a circuit diagram showing the abnormality detector 30a according to the first configuration example.
In this configuration example, the first photosensor 32 includes a first photodiode PD1 and a first color filter CF1. The first color filter CF <b> 1 has a high transmittance for blue light that is the wavelength of the excitation light 20, and a low transmittance for the wavelength of the fluorescence 22. The second photosensor 34 includes a second photodiode PD2 and a second color filter CF2. The second color filter CF2 has a high transmittance for green to red, which is the wavelength region of the fluorescence 22, and a low transmittance for blue light. A blue filter may be used as the first color filter CF1, and a yellow filter, a green filter, or a red filter may be used as the second color filter CF2.

  The first current-voltage conversion circuit 36 includes a first operational amplifier OA1 in addition to the first resistor R1. The first photosensor 32 is connected to the inverting input terminal (−) of the first operational amplifier OA1, and a fixed voltage is applied to the non-inverting input terminal (+). The fixed voltage is, for example, a ground voltage. The first resistor R1 is provided between the inverting input terminal (+) and the output terminal of the first operational amplifier OA1.

  More specifically, the cathode of the first photodiode PD1 of the first photosensor 32 is connected to the inverting input terminal (−) of the first operational amplifier OA1, and a fixed voltage is connected to the anode of the first photodiode PD1. (Ground voltage) is applied.

The voltage level of the first detection signal V1 generated by the first current-voltage conversion circuit 36 is expressed by Expression (3).
V1 = R1 × I _SC1 (3)

The second current-voltage conversion circuit 38 includes a second operational amplifier OA2 in addition to the second resistor R2, and is configured in the same manner as the first current-voltage conversion circuit 36. The voltage level of the output V2 is expressed by the following equation (4). Become.
V2 = R2 × I _SC2 (4)

  The determination unit 40 includes a voltage comparator CMP1 that compares the voltage levels of the first detection signal V1 and the second detection signal V2. The abnormality detection signal S1 output from the voltage comparator CMP1 is low level (negate) when V1 <V2, that is, when the phosphor 14 is normal, and when V1> V2, that is, when the phosphor 14 is abnormal. Becomes high level (asserted).

  The anomaly detector 30a in FIG. 5 can be configured with a small circuit including two operational amplifiers, two resistors, and one comparator in addition to two photodiodes. In addition, the current-voltage conversion gain (transimpedance) of each of the first current-voltage conversion circuit 36 and the second current-voltage conversion circuit 38 depends only on the first resistance R1 and the second resistance R2. Therefore, the influence of element variation can be reduced, and highly accurate abnormality detection can be performed.

  Further, according to the first current-voltage conversion circuit 36 of FIG. 5, the ground voltage is applied to each of the anode and cathode of the first photodiode PD1 by the virtual ground of the first operational amplifier OA1, and the anode cathode of the first photodiode PD1. The potential difference between them becomes substantially zero. Therefore, light can be detected without being affected by dark current in a wide light quantity range. The same applies to the second current-voltage conversion circuit 38.

(Second configuration example)
FIG. 6 is a circuit diagram showing an abnormality detector 30b according to the second configuration example.
With respect to the first current-voltage conversion circuit 36, the anode of the first photodiode PD1 is connected to the inverting input terminal (−) of the first operational amplifier OA21, and the non-inverting input terminal (+) of the first operational amplifier OA21. The cathode of the first photodiode PD1 is connected and a predetermined fixed voltage is applied. For example, the fixed voltage may be the power supply voltage _VCC or other voltage level.

The voltage level of the first detection signal V21 generated by the first current-voltage conversion circuit 36 of FIG. 6 is expressed by Equation (5).
V21 = V _CC -R21 × I _SC1 (5)

The second current-voltage conversion circuit 38 is configured in the same manner as the first current-voltage conversion circuit 36, and the voltage level of the output V22 is expressed by equation (6).
V22 = V _CC -R22 × I _SC2 (6)

  FIG. 7A is a diagram showing the relationship between the output light intensity and the first detection signal V21 and the second detection signal V22 when the phosphor 14 is normal, and FIG. It is a figure which shows the relationship between output light intensity, 1st detection signal V21, and 2nd detection signal V22 when is abnormal. As described above, the resistance values of the resistors R21 and R22 are determined so that the relational expressions (1) and (2) are established. Therefore, V21> V22 is established when normal, and V22 <V21 when abnormal. The voltage comparator CMP21 in FIG. 6 sets the abnormality detection signal S1 to a low level (negate) when V21> V22, that is, normal, and sets the abnormality detection signal S1 to a high level when V21 <V22, that is, abnormality. Assert).

  According to this configuration example, the same effect as the abnormality detector 30 of FIG. 5 can be obtained.

(Third configuration example)
Returning to FIGS. 4 (a) and 4 (b). In the first configuration example of FIG. 5, in the region where the output light intensity is small, the detection currents I _SC1 and I _SC2 are small, so the first detection signal V21 and the second detection signal V22 are close to each other. Therefore, when noise, element variations, offset voltages of operational amplifiers and voltage comparators (hereinafter referred to as error factors) are so large that they cannot be ignored, the magnitudes of the first detection signal V21 and the second detection signal V22 within a small range of output light intensity. The relationship is reversed, and there may be a problem that the abnormality is erroneously detected, or the abnormality cannot be detected although it is originally abnormal. As can be seen from FIGS. 7A and 7B, this problem can also occur in the second configuration example of FIG.

  Therefore, in the third configuration example, the determination unit 40 offsets at least one of the first detection signal V21 and the second detection signal V22 in a direction in which they are separated from each other, and based on the detection signals V21 and V22 after the offset. Determine if there is an abnormality.

  FIG. 8A is a circuit diagram of an abnormality detector 30c according to the third configuration example. The determination unit 40c includes voltage dividing circuits R11 and R12 in addition to the voltage comparator CMP21. The voltage dividing circuits R11 and R12 divide the second detection signal V22. The voltage comparator CMP21 compares the divided second detection signal V32 with the first detection signal V21, and generates an abnormality detection signal S1.

FIG. 9A is a diagram illustrating the relationship between the output light intensity and the first detection signal V21 and the second detection signal V22 when the phosphor 14 is normal in the abnormality detector 30c of FIG. 8A. In the abnormality detector 30c, the divided second detection signal V32 is given by Expression (7).
V32 = R12 / (R11 + R12) × V22
= R12 / (R11 + R12) × V _CC −R12 / (R11 + R12) × R22 × I _SC2 (7)

That is, the y-intercept of the second detection signal V32 in FIG. 9A is offset in a direction away from the first detection signal V21. The offset width ΔV is V _CC × R11 / (R11 + R12) and can be set by the resistors R11 and R12. For example, it is assumed that the offset voltage of the voltage comparator CMP21 is dominant as an error factor. In this case, the offset width ΔV is preferably slightly larger than the offset voltage of the voltage comparator CMP21 (for example, 20 mV).

  Thus, according to the third configuration example, the detection accuracy can be increased in a range where the output light intensity is small. In particular, in FIG. 8A, since it is only necessary to insert two R11 and R12 of the voltage dividing circuit, the detection accuracy can be increased with low cost and a small area.

  As described above, the absolute value of the slope of the second detection signal V32 divided by the voltage dividing circuits R11 and R12 is smaller than that without the voltage dividing circuit. Therefore, in the steady lighting region A where the output light intensity is large to some extent, the influence of the offset width ΔV by the voltage dividing circuit is sufficiently smaller than the region where the output light intensity is low, and the influence on the detection value can be ignored.

  It will be understood that the slope of the second detection signal V32 and the offset width ΔV can be set independently and arbitrarily by optimizing the resistance value of the second resistor R22 with the introduction of the voltage dividing circuits R11 and R12.

FIG. 8B is a circuit diagram of the abnormality detector 30d according to the fourth configuration example. The determination unit 40d includes voltage dividing circuits R13 and R14 in addition to the voltage comparator CMP1. Voltage divider circuit R13, R14 are, divides the second detection signal V2 and the power supply voltage _{V CC.} The voltage comparator CMP1 compares the divided second detection signal V2 ′ with the first detection signal V1, and generates an abnormality detection signal S1.

FIG. 9B is a diagram showing the relationship between the output light intensity, the first detection signal V1, and the second detection signal V2 ′ when the phosphor 14 is normal in the abnormality detector 30d of FIG. 8B. In the abnormality detector 30d, the second detection signal V2 ′ after the partial pressure is given by Expression (8).
V2 ′ = (R13 · V2 + R14 · V _CC ) / (R13 + R14)
= (R13 · R2 × I _SC2 + R14 · V _CC ) / (R13 + R14) (8)

That is, the y-intercept of the second detection signal V2 ′ in FIG. 9B is offset in a direction away from the first detection signal V1. The offset width ΔV is R14 · V _CC / (R13 + R14), and can be set by the resistors R13 and R14. In the fourth configuration example, the same effect as in the third configuration example is obtained.

  Subsequently, a modification of the first embodiment will be described.

(First modification)
In the embodiment, the determination unit 40 is configured by the voltage comparator CMP1, but the present invention is not limited thereto. For example, the determination unit 40 includes an A / D converter that converts the first detection signal V1 and the second detection signal V2 into digital values D1 and D2, respectively, and performs digital signal processing on the digital values D1 and D2. You may judge.

(Second modification)
The method of introducing the offset width ΔV is not limited to the voltage dividing circuits R11 and R12. For example, the comparator CMP1 may be configured so that the input offset voltage can be adjusted, and at least one of the first detection signal V1 and the second detection signal V2 may be offset. In this case, erroneous detection due to error factors such as noise can be prevented.

(Third Modification)
In the abnormality detector 30a of FIG. 5, it is also effective to offset at least one of the first detection signal V1 and the second detection signal V2. Specifically, the second detection signal V2 in FIG. 4A may be offset in the positive direction. This is achieved by applying a fixed voltage corresponding to the offset width ΔV to the non-inverting input terminal (+) of the first operational amplifier OA1.

(Fourth modification)
FIG. 10 is a block diagram of a vehicular lamp 1b according to a fourth modification. The vehicular lamp 1b includes a plurality (two in the present embodiment) of abnormality detectors 30. The abnormality detector 30 may use any of those described in the first embodiment and its modifications. The two abnormality detectors 30 may have the same configuration, or may combine abnormality detectors having different configurations.

The lighting circuit 200 is input with abnormality detection signals S1_1 and S1_2, which are outputs of the abnormality detectors 30, in different systems. The lighting circuit 200 fails-latches the plurality of abnormality detection signals S1_1 and S1_2, and executes a protection process when any of them indicates an abnormality. As described above, the protection process is to turn off the laser diode 12, that is, when any abnormality detection signal S1 is asserted, the lighting circuit 200 may stop supplying the drive current _ILD .

  Thus, in the fourth modification, a plurality of abnormality detectors 30 are provided, and a plurality of abnormality detection signals S1 obtained therefrom are applied to the fail latch for protection of the lighting circuit 200 in another system. Thereby, even when a failure occurs in an abnormality detector 30 of a certain system, an abnormality can be detected in another system, and thus robustness can be improved.

  In the fourth modified example, the lighting circuit 200 has one fail latch terminal, and the collectors of the transistors Tr1 and Tr2 in the output stages of the plurality of abnormality detectors 30_1 and 30_2 are shared by the fail latch terminals. You may connect to. In this case, the transistors Tr1 and Tr2 constitute an OR circuit, and protection processing can be performed when at least one abnormality detector 30 detects an abnormality.

  Next, the package of the first photodiode PD1 and the second photodiode PD2 for detecting an abnormality will be described.

  When a photodiode is used in an in-vehicle application, a CAN package is employed in order to ensure long-term reliability in a harsh environment exposed to high temperature and high humidity and thermal shock. Here, when two photodiodes are accommodated in one package, the cathodes are commonly connected, and the cathodes are electrically connected to the metal case.

Here, when it is desired to use a cathode common photodiode pair housed in a CAN package, the non-inverting type current-voltage conversion circuits 36 and 38 in FIG. 5 cannot be adopted, and the inverting type shown in FIGS. It is necessary to employ the current-voltage conversion circuits 36 and 38. However, FIG. 6, the abnormality detector 30b in FIG. 8A, the use of photodiodes pairs CAN package 30c, since the cathode potential is at the power supply voltage _{V CC,} the potential of the metal case becomes the power supply voltage _{V CC} . Here, the metal structure in the lamp is often grounded as a countermeasure against electromagnetic noise. Therefore, when the metal case comes into contact with the surrounding metal structure, the power supply ground is short-circuited, the photodiode becomes inoperable, and other circuit blocks sharing the power supply voltage _VCC are also inoperable. End up.

  Therefore, in the abnormality detectors 30b and 30c of FIGS. 6 and 8A, the photodiodes PD1 and PD2 are accommodated in the photodiode module 100 having the following structure. FIG. 11A is an equivalent circuit diagram of the photodiode module 100 including the photodiode pairs PD1 and PD2, and FIG. 11B is a schematic cross-sectional view thereof. The photodiode module 100 includes anode terminals A1 and A2, a cathode terminal K, two photodiodes PD1 and PD2, and a metal case 102. The metal case 102 is electrically insulated from the cathode terminal K. An opening 104 is provided on the upper surface of the metal case so that light can enter the photodiodes PD1 and PD2. The light receiving portions of the photodiodes PD1 and PD2 may be covered with a color filter.

  Here, in the application of the abnormality detector 30, the current flowing through the photodiodes PD1 and PD2 is as weak as the μA order, and the input impedance of the current-voltage conversion circuit is extremely large, so that it can be said that the noise resistance is low. Therefore, it is desirable to provide the photodiode module 100 with a case terminal C that is electrically connected to the metal case 102. In this case, since the metal case 102 functions as a shield by grounding the case terminal C, resistance to electromagnetic noise can be increased.

(Second Embodiment)
FIG. 12 is a block diagram of the vehicular lamp 1 including the abnormality detector 50 according to the second embodiment. The vehicular lamp 1 includes a light source 10 and an abnormality detector 50 that detects an abnormality of the light source 10. The light source 10 is the same as that of the first embodiment, and is configured to generate white output light 24 including the excitation light 20 and the fluorescence 22 spectrum.

  The abnormality detector 50 receives a part of the output light 24 and determines whether or not the light source 10 is abnormal, more specifically, whether or not the phosphor 14 is abnormal. Examples of the abnormality of the phosphor 14 include, but are not particularly limited to, the phosphor 14 being cracked, detached, and aged.

The abnormality detector 50 includes a diffraction element 52, a photodetector 54, and a determination unit 56.
The diffraction element 52 diffracts the output light 24 of the light source 10. For example, a transmissive or reflective diffraction grating is used as the diffraction element 52. The photodetector 54 detects the diffracted light 26 of the diffractive element 52. The determination unit 56 determines the presence / absence of an abnormality based on the detection result of the photodetector 54.

The above is the basic configuration of the abnormality detector 50. Next, the principle will be described.
FIG. 13A shows the diffracted light when the phosphor 14 is normal, and FIG. 13B shows the diffracted light when the phosphor 14 is abnormal.
When the phosphor 14 is normal, the excitation light 20 is scattered by the phosphor 14, so that the excitation light 20 input to the diffractive element 52 has reduced coherency, and thus is obtained by the diffractive element 52. No significant interference fringes are observed in the diffracted light 26 (FIG. 13 (a)). On the other hand, when the phosphor 14 is abnormal, the excitation light 20 is not scattered and is input to the diffraction element 52 in a coherent state, and thus significant interference fringes are observed in the diffracted light 26 by the diffraction element 52. (FIG. 13B).

  Therefore, according to the anomaly detector 50, the presence or absence of abnormality of the phosphor 14 can be determined based on the diffracted light 26 obtained by the diffraction element 52, more specifically, based on the presence or absence of a significant diffraction pattern (interference fringe). .

  The scope of the present invention extends to various circuits grasped as the block diagram of FIG. 12, but a specific configuration example will be described below.

(First configuration example)
FIG. 14 is a diagram illustrating the vehicular lamp 1a including the abnormality detector 50a according to the first configuration example. The vehicular lamp 1a includes a light source 10, a reflector 2 that reflects the emitted light 24 of the light source 10, and a lens 4 that receives the emitted light 24 reflected by the reflector 2 and emits the light forward. The reflector 2 is provided with a pinhole. A diffractive element 52 is provided on the back side of the reflector 2, and a part of the outgoing light 24 that passes through the pinhole 58 reaches the diffractive element 52. The size (opening area) of the pinhole 58 is not particularly limited.

  The photodetector 54 has two points, a first position A where the pattern of the diffracted light 26 has a peak when the phosphor 14 is normal and a second position B where the peak does not exist when the phosphor 14 is normal. It is comprised so that the light intensity of can be detected. For example, the photodetector 54 includes two photosensors PS1 and PS2 provided at the positions of these two points A and B. The photodetector 54 is configured to be sensitive to blue that is the excitation light 20, and is desirably low insensitive (insensitive) particularly to yellow that is fluorescence.

  The determination unit 56 determines whether there is an abnormality based on the light intensity at two points. More specifically, the determination unit 56 may determine that the phosphor 14 is abnormal when the difference between the outputs of the two photosensors PS1 and PS2 exceeds a predetermined threshold.

  Or the determination part 56 may determine the presence or absence of abnormality based on the ratio of light intensity instead of the difference of the light intensity of A point and B point. In this case, the presence or absence of abnormality can be determined regardless of the output light intensity of the light source 10. Or the determination part 56 may determine the presence or absence of abnormality, combining a difference and ratio.

  Instead of forming the pinhole 58 in the reflector 2, the reflectance of a part of the reflector 2 may be lowered and the output light 24 of the light source 10 may be transmitted.

FIGS. 15A and 15B are circuit diagrams illustrating a specific configuration example of the determination unit 56.
The determination unit 56 in FIG. 15A includes a difference calculator 60 and a voltage comparator CMP2. The difference calculator 60 receives the detection signal Vs1 from the photosensor PS1 and the detection signal Vs2 from the photosensor PS2, and amplifies the difference between them. The configuration of the difference calculator 60 is not particularly limited, and a known circuit may be used. The voltage comparator CMP2 compares the output voltage V3 of the difference calculator 60 with a predetermined threshold voltage _VTH . The output of the voltage comparator CMP2 (abnormality detection signal S1) is negated when the difference between the outputs of the two photosensors is smaller than the threshold value, and asserted when the difference becomes larger than the threshold value. In this configuration example, a negative logic system is adopted, and assert is assigned to a low level and negate is assigned to a high level.

  The determination unit 56 may be configured with a digital circuit. The determination unit 56 in FIG. 15B includes A / D converters 62 and 64, a subtractor 66, and a comparator 68. The A / D converters 62 and 64 convert the detection signals Vs1 and Vs2 of the photosensors PS1 and PS2 into digital signals Ds1 and Ds2, respectively. The A / D converter 64 calculates a difference signal S3 between the digital signals Ds1 and Ds2. The comparator 68 compares the difference signal S3 with the threshold value TH to determine whether there is an abnormality.

(Second configuration example)
FIG. 16 is a circuit diagram showing an anomaly detector 50b according to the second configuration example. The photodetector 54 b includes a plurality of pixels 55 that receive the diffracted light 26. The photodetector 54b can use a CCD or a CMOS sensor, and may be combined with a color filter. The photodetector 54b may be a line sensor including a plurality of pixels arranged in a one-dimensional manner, or may be a matrix array sensor including a plurality of pixels arranged in a matrix.

  The determination unit 56b determines whether there is an abnormality based on the pattern of the diffracted light 26 measured by the plurality of pixels 55. Hereinafter, some determination methods by the abnormality detector 50b will be described.

  For example, among the plurality of pixels 55, pixels corresponding to points A and B in FIG. 14 may be used as the photosensors PS1 and PS2 in FIG. The process of the determination unit 56b in this case is as described above.

  Alternatively, the pattern of the diffracted light 26 is obtained by using all or a part of the plurality of pixels 55, and compared with a predetermined diffraction pattern to check the matching thereof, so that interference fringes can be obtained. The presence or absence may be detected and the presence or absence of an abnormality may be determined.

  Or the determination part 56 may determine the presence or absence of abnormality by calculating the data of the diffracted light 26 measured by the photodetector 54b. FIG. 17A is a diagram showing an output S4 of the photodetector 54b and its differential data S5 when the phosphor 14 is abnormal, and FIG. 17B is a diagram when the phosphor 14 is normal. It is a figure which shows the output S4 and its differential data S5 of the photodetector 54b.

  Differentiating the output S4 of the photodetector 54b is equivalent to spatially differentiating the data measured by the plurality of pixels 55, and the edges of the interference fringes can be detected by differentiation processing. Then, by comparing the differential data S5 with a predetermined threshold value TH, it is possible to determine whether a significant interference fringe has occurred and to determine whether the phosphor 14 is abnormal. Note that the threshold value TH may be provided in the negative direction, in which case the opposite edge of the interference fringes can be detected. Alternatively, the threshold value TH may be set to both positive and negative.

  FIG. 18 is a circuit diagram illustrating a configuration example of the determination unit 56b. The determination unit 56b includes a differentiator 70 that spatially differentiates the data S4 indicating the diffracted light 26. Data S4 from the plurality of pixels 55 of the photodetector 54b may be sequentially read from the end. At this time, the spatial differentiation is equivalent to time differentiation of the data S4 from the plurality of pixels 55 that are sequentially read. Therefore, the differentiator 70 can be configured by a differential amplifier that differentiates the analog data signal S4. The differential amplifier (high-pass filter) mainly includes a resistor R21, a capacitor C21, and an operational amplifier OA3.

Voltage comparator 72, the output signal S5 of the differentiator 70 is compared with the threshold value _{V TH,} a low level when _{S5> V TH,} and outputs a high level when S5 _{<V TH.} A final determination circuit 74 including a filter or a timer may be provided after the voltage comparator 72. When the output of the voltage comparator 72 remains at the low level for a predetermined determination time, the final determination circuit 74 determines that the phosphor 14 is abnormal and asserts the abnormality detection signal S1 (high level).

  When the signal S4 from the photodetector 54b contains a lot of noise, the noise is amplified by the differentiator 70, and the S / N ratio may be lowered. Therefore, a resistor R22 (R11> R22) and a capacitor C22 (C21> C22) that form a weak integrator (low-pass filter) together with the operational amplifier OA3 may be added to the differentiator 70. Thereby, noise can be removed and the S / N ratio can be increased. To

  FIG. 18 shows the determination unit 56b of an analog circuit, but it will be understood by those skilled in the art that equivalent processing can be realized by a digital circuit. Specifically, the analog detection signal S4 from the photodetector 54b is converted into a digital value by an A / D converter, the digital value is differentiated, and compared with a threshold value to determine whether there is an abnormality. it can.

  Finally, the use of the vehicular lamp 1 will be described. FIG. 19 is a perspective view of a lamp unit (lamp assembly) 500 including the vehicular lamp 1 according to the embodiment. The lamp unit 500 includes a transparent cover 502, a high beam unit 504, a low beam unit 506, and a housing 508. The vehicle lamp 1 described above can be used for the high beam unit 504, for example. The vehicular lamp 1 includes one or a plurality of light sources 10. Instead of or in addition to the high beam unit 504, the vehicular lamp 1 may be used for the low beam unit 506.

  Although the present invention has been described using specific terms based on the embodiments, the embodiments only illustrate the principles and applications of the present invention, and the embodiments are defined in the claims. Many variations and modifications of the arrangement are permitted without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Vehicle lamp, 2 ... Reflector, 4 ... Lens, 10 ... Light source, 12 ... Laser diode, 14 ... Phosphor, 16 ... Optical system, 18 ... Housing, 20 ... Excitation light, 22 ... Fluorescence, 24 ... Output light , 26 ... diffracted light, 30 ... abnormality detector, 32 ... first photosensor, 34 ... second photosensor, 36 ... first current-voltage conversion circuit, 38 ... second current-voltage conversion circuit, PD1 ... first photodiode , CF1 ... first color filter, PD2 ... second photodiode, CF2 ... second color filter, 40 ... determining unit, R1 ... first resistor, R2 ... second resistor, OA1 ... first operational amplifier, OA2 ... second Operational amplifier, CMP1 ... voltage comparator, V1 ... first detection signal, V2 ... second detection signal, S1 ... abnormality detection signal, 50 ... abnormality detector, 52 ... diffraction element, 54 ... photodetector, 56 ... determination unit, 5 DESCRIPTION OF SYMBOLS ... Pinhole, 60 ... Difference calculator, CMP2 ... Voltage comparator, 62 ... A / D converter, 64 ... A / D converter, 66 ... Subtractor, 68 ... Comparator, 70 ... Differentiator, 500 ... Lamp unit, 502 ... Cover, 504 ... High beam unit, 506 ... Low beam unit, 508 ... Housing.

Claims (18)

A light source anomaly detector,
The light source is
A laser diode that emits excitation light; and
A phosphor that emits fluorescence when excited by the excitation light;
And configured to generate white output light including a spectrum of the excitation light and the fluorescence,
The abnormality detector is
A first photosensor that is sensitive to the wavelength of the excitation light, substantially insensitive to the wavelength of the fluorescence, receives a portion of the output light, and generates a first current according to the amount of received light; ,
A second photosensor that is sensitive to the wavelength of the fluorescence, substantially insensitive to the wavelength of the excitation light, receives a portion of the output light, and generates a second current according to the amount of received light; ,
A first current-voltage conversion circuit including a first resistor provided on the path of the first current, and outputting a first detection signal according to a voltage drop of the first resistor;
A second current-voltage conversion circuit including a second resistor provided on the path of the second current, and outputting a second detection signal corresponding to a voltage drop of the second resistor;
A determination unit for determining the presence or absence of abnormality based on the first detection signal and the second detection signal;
An anomaly detector comprising: When the first current when the phosphor is normal is I1, the second current is I2, the first current when the phosphor is abnormal is I1 ′, and the second current is I2 ′ The resistance value R1 of the first resistor and the resistance value R2 of the second resistor are expressed by a relational expression R1 × I1 <R2 × I2 (1)
R1 × I1 ′> R2 × I2 ′ (2)
The abnormality detector according to claim 1, wherein the abnormality detector is defined so as to satisfy   3. The abnormality detector according to claim 1, wherein the determination unit determines that an abnormality occurs when a magnitude relationship between the first detection signal and the second detection signal is reversed.   The abnormality detector according to claim 3, wherein the determination unit includes a voltage comparator. The first current-voltage conversion circuit includes:
A first operational amplifier in which the first photosensor is connected to an inverting input terminal and a fixed voltage is applied to a non-inverting input terminal;
The first resistor provided between an inverting input terminal and an output terminal of the first operational amplifier;
Including
The second current-voltage conversion circuit includes:
A second operational amplifier in which the second photosensor is connected to the inverting input terminal and a fixed voltage is applied to the non-inverting input terminal;
The second resistor provided between an inverting input terminal and an output terminal of the second operational amplifier;
The abnormality detector according to any one of claims 1 to 4, wherein the abnormality detector is included. Each of the first photosensor and the second photosensor includes a first photodiode and a second photodiode,
The cathode of the first photodiode is connected to the inverting input terminal of the first operational amplifier, the fixed voltage is applied to the anode of the first photodiode,
6. The cathode of the second photodiode is connected to the inverting input terminal of the second operational amplifier, and the fixed voltage is applied to an anode of the second photodiode. The anomaly detector described. Each of the first photosensor and the second photosensor includes a first photodiode and a second photodiode,
The anode of the first photodiode is connected to the inverting input terminal of the first operational amplifier, and the cathode of the first photodiode is connected to the non-inverting input terminal of the first operational amplifier. A predetermined fixed voltage is applied,
The anode of the second photodiode is connected to the inverting input terminal of the second operational amplifier, and the cathode of the second photodiode is connected to the non-inverting input terminal of the second operational amplifier. The abnormality detector according to claim 5, wherein the fixed voltage is applied.   The abnormality detector according to claim 1, wherein the determination unit offsets at least one of the first detection signal and the second detection signal in a direction in which they are separated from each other.   The abnormality detector according to claim 7, wherein the determination unit includes a voltage dividing circuit that divides the second detection signal. The light source;
An abnormality detector according to any one of claims 1 to 9, which detects an abnormality of the light source;
A lighting circuit that drives the light source and executes a predetermined protection process when the abnormality detector detects an abnormality,
A vehicular lamp characterized by comprising: A plurality of the abnormality detectors are provided,
11. The vehicular lamp according to claim 10, wherein the lighting circuit executes the protection process when at least one of the abnormality detectors detects an abnormality. A light source anomaly detector,
The light source is
A laser diode that emits excitation light; and
A phosphor that emits fluorescence when excited by the excitation light;
And configured to generate white output light including a spectrum of the excitation light and the fluorescence,
The abnormality detector is
A diffraction element for diffracting the output light of the light source;
A photodetector for detecting the diffracted light of the diffraction element;
A determination unit for determining the presence or absence of abnormality based on a detection result of the photodetector;
An anomaly detector comprising: The photodetector has two light points: a first position where the pattern of the diffracted light has a peak when the phosphor is normal and a second position where the peak does not exist when the phosphor is normal. Detect the intensity,
The abnormality detector according to claim 12, wherein the determination unit determines the presence or absence of abnormality based on the light intensity at the two points. The photodetector includes two photosensors provided at the two points,
The abnormality detector according to claim 13, wherein the determination unit determines an abnormality when a difference between outputs of the two photosensors exceeds a predetermined threshold value. The photodetector has a plurality of pixels that receive the diffracted light,
The determination unit determines the presence or absence of abnormality based on the diffraction pattern measured by the plurality of pixels,
The abnormality detection according to claim 14, wherein the determination unit includes a differentiator that spatially differentiates data measured by the plurality of pixels, and determines whether there is an abnormality based on an output of the differentiator. vessel. The data from the plurality of pixels is sequentially read,
The differentiator time-differentiates data from the plurality of pixels that are sequentially read out,
The abnormality detector according to claim 15, wherein the determination unit determines that the output is abnormal when the output of the differentiator exceeds a predetermined threshold value.   The anomaly detector according to claim 12, further comprising a pinhole provided between the diffraction element and the light source. The light source and the abnormality detector are used for a vehicle lamp,
The abnormality detector according to claim 17, wherein the vehicular lamp includes a reflector that reflects output light of the light source, and the pinhole is formed in the reflector.