Vehicle lamp device and abnormality detector of light source thereof

An abnormality detector for a light source includes a laser diode which emits an excitation light and a fluorescent substance which is excited by the excitation light to generate a fluorescent light. The abnormality detector includes a first photo sensor which is sensitive to a wavelength of the excitation light, a second photo sensor which is sensitive to a wavelength of the fluorescent light, a first current-voltage conversion circuit which outputs a first detection signal based on an output of the first photo sensor, a second current-voltage conversion circuit which outputs a second detection signal based on an output of the second photo sensor, and a determination unit which determines whether an abnormality occurs based on the first detection signal and the second detection signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of priority of Japanese Patent Application No. 2014-179881, filed on Sep. 4, 2014 and Japanese Patent Application No. 2015-005214, filed on Jan. 14, 2015, the content of which is incorporated herein by reference.

TECHNICAL FIELD

Aspects of the present invention relate to a vehicle lamp device to be used for an automobile and the like.

BACKGROUND

Conventionally, a vehicle lamp device, particularly, a head lamp, mainly uses a halogen lamp or a High Intensity Discharge (HID) lamp as a light source. In recent years, however, a vehicle lamp device using a semiconductor light source such as a Light Emitting Diode (LED) has been developed.

In order to further improve visibility, for example, JP-A-2004-241142 discloses a vehicle lamp device including a laser diode (also referred to as a semiconductor laser) and a fluorescent substance, instead of an LED. In this vehicle lamp device, an ultraviolet light which is an excitation light emitted from the laser diode is emitted to the fluorescent substance. The fluorescent substance receives the ultraviolet light and generates a white light. The white light generated by the fluorescent substance is emitted to the front of the lamp device such that a predetermined light distribution pattern is formed. In this vehicle lamp device, the excitation light is not emitted to the front.

SUMMARY

FIG. 1is a sectional view of a light source of a vehicle lamp device examined by the inventor of the present invention. The light source10includes a laser diode12, a fluorescent substance14, an optical system16and a housing18. The light source10is similar to the vehicle lamp device disclosed in JP-A-2004-241142 in that it has the laser diode12and the fluorescent substance14.

The laser diode12is configured to generate a blue excitation light20(not an ultraviolet light). The excitation light20is concentrated on the fluorescent substance14by the optical system16. The optical system16is configured by a lens, a reflector, an optical fiber or a combination thereof. The fluorescent substance14having received the blue excitation light20generates a fluorescent light22having a spectral distribution in a wavelength region (green to red) longer than the excitation light20. The excitation light20emitted to the fluorescent substance14is scattered by the fluorescent substance14and passes through the fluorescent substance14with coherence thereof being lost. The fluorescent substance14is fitted and supported to an opening formed in the housing18, for example.

FIG. 2shows a spectrum of an output light24of the light source10. The output light24of the light source10includes a blue excitation light20ahaving passed through the fluorescent substance14and green to red fluorescent light22generated by the fluorescent substance14and has a spectral distribution of the white light.

That is, while the ultraviolet excitation light is not used as a part of the emission light illuminating the front of the vehicle in the vehicle lamp device of JP-A-2004-241142, the blue excitation light is used as a part of the emission light of the head lamp in the light source10ofFIG. 1.

The inventor of the present invention studied on the light source10ofFIG. 1and recognized following problems. In the light source10ofFIG. 1, when an abnormality such as breaking of the fluorescent substance14or removal of the fluorescent substance14from the housing18occurs, the excitation light20generated by the laser diode12is directly emitted to the front of the vehicle with the strong coherence and without being scattered by the fluorescent substance14, which is dangerous.

The present invention has been made in view of the above circumstances, and an aspect of the present invention provides a technique capable of securely detecting an abnormality in a light source having a combination of a blue laser diode and a fluorescent substance.

According to a first aspect of the present invention, there is provided an abnormality detector for a light source. The light source includes a laser diode configured to emit an excitation light and a fluorescent substance configured to be excited by the excitation light to generate a fluorescent light, and is configured to generate a white output light having spectra of the excitation light and the fluorescent light. The abnormality detector includes a first photo sensor which is sensitive to a wavelength of the excitation light and substantially insensitive to a wavelength of the fluorescent light and which is configured to receive a part of the output light to generate a first current in accordance with an amount of the received light, a second photo sensor which is sensitive to the wavelength of the fluorescent light and substantially insensitive to the wavelength of the excitation light and which is configured to receive a part of the output light to generate a second current in accordance with an amount of the received light, a first current-voltage conversion circuit which includes a first resistance provided on a path of the first current and which is configured to output a first detection signal corresponding to a voltage drop of the first resistance, a second current-voltage conversion circuit which includes a second resistance provided on a path of the second current and which is configured to output a second detection signal corresponding to a voltage drop of the second resistance, and a determination unit which is configured to determine whether an abnormality occurs based on the first detection signal and the second detection signal.

The first detection signal linearly changes in accordance with an amount of light of the excitation light, and a gradient thereof is determined in accordance with a resistance value of the first resistance. Similarly, the second detection signal linearly changes in accordance with an amount of light of the fluorescent light, and a gradient thereof is determined in accordance with a resistance value of the second resistance. Here, when the fluorescent substance is normal, an intensity of the excitation light, an intensity of the fluorescent light and an intensity of the white light, which is an output of the light source, are proportional to each other. Therefore, when the fluorescent substance is normal, a ratio of the first detection signal and the second detection signal is substantially constant, and when an abnormality occurs in the fluorescent substance and the excitation light is thus directly emitted, a balance of the excitation light and fluorescent light included in the output light is lost, so that the ratio of the first detection signal and the second detection signal changes. According to the above configuration, it is possible to simply and securely detect the abnormality of the fluorescent substance by appropriately determining the resistance values of the first resistance and the second resistance and monitoring the first detection signal and the second detection signal, irrespective of an intensity of the white light, i.e., an output of the light source.

In the above abnormality detector, in a case where the first current is denoted as I1and the second current is denoted as I2when the fluorescent substance is normal, and the first current is denoted as I1′ and the second current is denoted as I2′ when the fluorescent substance is abnormal, a resistance value R1of the first resistance and a resistance value R2of the second resistance may satisfy the following relation equations:
R1×I1<R2×I2  (1); and
R1×I1′>R2×I2′  (2).

In this case, it is possible to detect whether an abnormality occurs by comparing magnitudes of the first detection signal and the second detection signal.

In the above abnormality detector, the determination unit may be configured to determine that an abnormality occurs when a magnitude relation of the first detection signal and the second detection signal is reversed.

In the above abnormality detector, the determination unit may include a voltage comparator.

In the above abnormality detector, the first current-voltage conversion circuit may include a first operational amplifier having an inverting input terminal to which the first photo sensor is connected and a non-inverting input terminal to which a fixed voltage is applied, and the first resistance provided between the inverting input terminal and an output terminal of the first operational amplifier. The second current-voltage conversion circuit may include a second operational amplifier having an inverting input terminal to which the second photo sensor is connected and a non-inverting input terminal to which a fixed voltage is applied, and the second resistance provided between the inverting input terminal and an output terminal of the second operational amplifier.

In this configuration, gains (current-voltage conversion) of the first current-voltage conversion circuit and the second current-voltage conversion circuit are determined only by the resistance values of the first resistance and the second resistance. Thereby, it is possible to exclude an error factor, so that it is possible to detect an abnormality with high precision.

In the above abnormality detector, the first photo sensor may include a first photo diode, and the second photo sensor may include a second photo diode. A cathode of the first photo diode may be connected to the inverting input terminal of the first operational amplifier and a fixed voltage may be applied to an anode of the first photo diode. A cathode of the second photo diode may be connected to the inverting input terminal of the second operational amplifier and a fixed voltage may be applied to an anode of the second photo diode.

In this case, since a voltage is not applied between the anode and cathode of the photo diode, it is possible to detect the light without an influence of a dark current in a wide range of the amount of light.

In the above abnormality detector, the first photo sensor may include a first photo diode, and the second photo sensor may include a second photo diode. The inverting input terminal of the first operational amplifier may be connected with an anode of the first photo diode, and the non-inverting input terminal of the first operational amplifier may be connected with a cathode of the first photo diode and is applied with a fixed voltage. The inverting input terminal of the second operational amplifier may be connected with an anode of the second photo diode, and the non-inverting input terminal of the second operational amplifier may be connected with a cathode of the second photo diode and may be applied with a fixed voltage.

In the above abnormality detector, the determination unit may be configured to offset at least one of the first detection signal and the second detection signal in a direction of separating from each other.

When the output of the light source is low, the first detection signal and the second detection signal are close to each other, so that a false detection may be caused due to an influence of the noise. If an offset is used, it is possible to suppress the abnormal false detection when the amount of light is small.

In the above abnormality detector, the determination unit may include a voltage-dividing circuit configured to voltage-divide the second detection signal. Thereby, it may be possible to provide the offset by the simple configuration of only the two resistances. In the meantime, at this time, when the output of the light source is greater than a predetermined value, the influence resulting from the setting of the voltage-dividing circuit, i.e., an influence resulting from the usage of the offset is suppressed and the precision of the abnormality detection can be kept.

According to another aspect of the present invention, there is provided a vehicle lamp device. The vehicle lamp device includes a light source, the above abnormality detector which is configured to detect an abnormality of the light source; and a lighting circuit which is configured to drive the light source and to execute predetermined protection processing when the abnormality detector detects an abnormality of the light source.

In the above vehicle lamp device, a plurality of the abnormality detectors may be provided, and the lighting circuit may execute the protection processing when at least one the abnormality detectors detects an abnormality.

In this case, even when a failure or abnormality occurs in any one abnormality detector, it is possible to detect the abnormality of the light source by the separate abnormality detector and to execute the appropriate protection processing.

According to a second aspect of the present invention, there is provided an abnormality detector for a light source. The light source includes a laser diode configured to emit an excitation light and a fluorescent substance configured to be excited by the excitation light to generate a fluorescent light, and which is configured to generate a white output light having spectra of the excitation light and the fluorescent light. The abnormality detector includes a diffraction element which is configured to diffract the output light of the light source, a light detector which is configured to detect a diffracted light by the diffraction element, and a determination unit which is configured to determine whether an abnormality occurs based on a detection result of the light detector.

When the fluorescent substance is normal, the excitation light is scattered by the fluorescent substance. Therefore, the excitation light incident to the diffraction element is lowered in coherency, so that a substantial interference fringe (interference fringe) is not observed in the diffracted light obtained by the diffraction element. On the other hand, when the fluorescent substance is abnormal, the excitation light is not scattered and is highly-coherently incident to the diffraction element. Therefore, the substantial interference fringe is observed in the diffracted light obtained by the diffraction element. Therefore, according to the second aspect, it is possible to determine whether the fluorescent substance is abnormal based on the diffracted light of the diffraction element.

In the above abnormality detector, the light detector may be configured to detect light intensities of two positions including a first position at which a pattern of the diffracted light has a peak when the fluorescent substance is normal and a second position at which there is no peak when the fluorescent substance is normal, and the determination unit may be configured to determine whether an abnormality occurs based on the light intensities of the two positions.

In the above abnormality detector, the light detector may include two photo sensors provided at the two positions, and the determination unit may be configured to determine that an abnormality occurs when a difference of outputs of the two photo sensors exceeds a predetermined threshold.

In the above abnormality detector, the light detector may include a plurality of pixels configured to receive the diffracted light, and the determination unit may be configured to determine whether an abnormality occurs based on a diffraction pattern measured by the plurality of pixels.

In the above abnormality detector, the determination unit may include a differentiator configured to spatially differentiate data measured by the plurality of pixels, and the determination unit may be configured to determine whether occurs an abnormality based on an output of the differentiator. Thereby, it is possible to determine whether the substantial diffraction pattern occurs.

In the above abnormality detector, the data from the plurality of pixels may be sequentially read, the differentiator may be configured to temporally differentiate the data sequentially read from the plurality of pixels, and the determination unit may be configured to determine that an abnormality occurs when the output of the differentiator exceeds a predetermined threshold.

The above abnormality detector may further include a pinhole provided between the diffraction element and the light source. Thereby, when the fluorescent substance is abnormal, it is possible to obtain a clear diffraction pattern.

In the above abnormality detector, the light source and the abnormality detector may be used for a vehicle lamp device, the vehicle lamp device may include a reflector configured to reflect the output light of the light source, and the reflector may be formed with the pinhole.

According to another aspect of the present invention, there is provided a vehicle lamp device. The vehicle lamp device includes a light source and the above abnormality detector which is configured to detect an abnormality of the light source.

According to the above configuration, it is possible to detect an abnormality of the fluorescent substance.

DETAILED DESCRIPTION

Illustrative embodiments will be described below with reference to the accompanying drawings. Constituent elements, members and/or steps which are shown in the drawings and which are the same as or equivalent to each other may be given the same reference signs. Also, redundant description thereon may be omitted accordingly. It should be noted that the illustrative embodiments described below do not limit the scope of the invention and are just exemplary or illustrative. All of features described below or any combination thereof may not be always essential for the present invention.

In this specification, the description “a state where a member A is connected to a member B” includes not only a case where the member A and the member B are physically directly connected but also a case where the member A and the member B are indirectly connected via another member, which does not substantially influence electrical connection states thereof or does not damage functions and effects exhibited by the connection thereof.

Similarly, the description “a state where a member C is provided between a member A and a member B” includes not only a case where the member A and the member C or the member B and the member C are directly connected but also a case where the member A and the member C or the member B and the member C are indirectly connected via another member, which does not substantially influence electrical connection states thereof or does not damage functions and effects exhibited by the connection thereof.

Also, in this specification, the reference numerals denoted at an electric signal such as a voltage signal and a current signal, and a circuit element such as a resistance and a capacitor may indicate a voltage value, a current value, a resistance value and a capacitance.

First Illustrative Embodiment

FIG. 3is a block diagram of a vehicle lamp device1having an abnormality detector30according to a first illustrative embodiment. The vehicle lamp device1includes a light source10, the abnormality detector30configured to detect an abnormality of the light source10and a lighting circuit200.

As described with reference toFIG. 1, the light source10includes a laser diode12, a fluorescent substance14and an optical system16. The laser diode12is configured to emit an excitation light20. The laser diode12is configured to emit the light with an intensity corresponding to a driving current supplied from a driving circuit (not shown). The fluorescent substance14is provided on a light path of the excitation light20and is excited by the excitation light20to generate a fluorescent light22. The light source10is configured to generate a white output light24including spectra of the excitation light20and the fluorescent light22.

The lighting circuit200is configured to supply a driving current ILDto the laser diode12and to enable the laser diode12to emit the light. A configuration of the lighting circuit200is not particularly limited and a known configuration may be used.

The abnormality detector30is configured to receive a part of the output light24and to determine whether the light source10is abnormal, more specifically, whether the fluorescent substance14is abnormal. The abnormality of the fluorescent substance14may be, for example, breaking, removal, aging deterioration and the like of the fluorescent substance14, but not limited to those. When the abnormality detector30detects an abnormality, the abnormality detector30asserts an abnormality detection signal S1(for example, changes into a high level). When the abnormality detector30detects an abnormality, the lighting circuit200executes predetermined protection processing. The protection processing may include light-off of the laser diode12, reduction in brightness (an amount of light), notifications to various upper Electronic Control Units (ECUs) and the like, but not limited to those.

The abnormality detector30includes a first photo sensor32, a second photo sensor34, a first current-voltage conversion circuit36, a second current-voltage conversion circuit38and a determination unit40. The first photo sensor32is sensitive to a wavelength of the excitation light20and is substantially insensitive to a wavelength of the fluorescent light22. The first photo sensor32is configured to receive a part of the output light24to generate a first current ISC1in accordance with the intensity of the excitation light20having passed through the fluorescent substance14. The second photo sensor34is sensitive to the wavelength of the fluorescent light22and is substantially insensitive to the wavelength of the excitation light20. The second photo sensor34is configured to receive a part of the output light24to generate a second current ISC2in accordance with the intensity of the fluorescent light22generated by the fluorescent substance14.

The wavelength selectivity to which the first photo sensor32and the second photo sensor34are respectively sensitive may be implemented by a color filter, a semiconductor material of a sensor or a device structure. The first photo sensor32and the second photo sensor34are not particularly limited, and semiconductor light sensors such as photo diodes and photo transistors may be used. In this illustrative embodiment, the first photo sensor32and the second photo sensor34include the photo diodes, respectively.

The first current-voltage conversion circuit36includes a first resistance R1provided on a path of the first current ISC1and is configured to output a first detection signal V1corresponding to a voltage drop VSC1of the first resistance R1. The first detection signal V1linearly changes with respect to the first current ISC1with a gradient corresponding to a resistance value of the first resistance R1.

The second current-voltage conversion circuit38includes a second resistance R2provided on a path of the second current ISC2and is configured to output a second detection signal V2corresponding to a voltage drop VSC2of the second resistance R2. The second detection signal V2linearly changes with respect to the second current ISC2with a gradient corresponding to a resistance value of the second resistance R2.

The determination unit40is configured to determine whether an abnormality occurs based on the first detection signal V1and the second detection signal V2. When an abnormality is detected, the determination unit40asserts the abnormality detection signal S1(for example, changes into a high-level). The above is the basic configuration of the abnormality detector30. Subsequently, an operation principle thereof is described.

The first detection signal V1linearly changes in accordance with an amount of light of the excitation light20, and the gradient thereof is determined in accordance with the resistance value of the first resistance R1. Similarly, the second detection signal V2linearly changes in accordance with an amount of light of the fluorescent light22, and the gradient thereof is determined in accordance with the resistance value of the second resistance R2. Here, when the fluorescent substance14is normal, an intensity of the excitation light20, an intensity of the fluorescent light22and an intensity of the output light24of the light source10are proportional to each other. Therefore, when the fluorescent substance14is normal, a ratio of the first detection signal V1and the second detection signal V2is substantially constant. In contrast, when the fluorescent substance14is abnormal and the excitation light20is thus directly emitted, a balance of the excitation light20and fluorescent light22included in the output light24is lost, so that the ratio of the first detection signal V1and the second detection signal V2changes. According to the abnormality detector30ofFIG. 3, it is possible to simply and securely detect the abnormality of the fluorescent substance14by appropriately determining the resistance values of the first resistance R1and the second resistance R2and monitoring the first detection signal V1and the second detection signal V2, irrespective of an intensity of the white light, i.e., an output of the light source.

FIG. 4Ashows a relation among an output light intensity, the first detection signal V1and the second detection signal V2when the fluorescent substance14is normal, andFIG. 4Bshows a relation among the output light intensity, the first detection signal V1and the second detection signal V2when the fluorescent substance14is abnormal.

When the fluorescent substance14is normal, the first current ISC1is denoted as I1and the second current ISC2is denoted as I2at an output light intensity, and when the fluorescent substance14is abnormal, the first current ISC1is denoted as I1′ and the second current ISC2is denoted as I2′. When an abnormality occurs in the fluorescent substance14, the intensity of the fluorescent light22decreases and the excitation light20passes without being absorbed by the fluorescent light22, so that I1′ becomes larger than I1and I2′ becomes smaller than I2. At this time, the resistance value of the first resistance R1and the resistance value of the second resistance R2are preferably determined to meet following relation equations.
R1×I1<R2×I2  (1)
R1×I1′>R2×I2′  (2)

The abnormality detector30compares a magnitude relation of the first detection signal V1and the second detection signal V2and determines that an abnormality occurs when the magnitude relation is reversed. The processing of the abnormality detector30is equivalent to processing of comparing a ratio ISC1/ISC2of the detection current ISC1of the first photo sensor32and the detection current ISC2of the second photo sensor34and a ratio R2/R1of the resistance values of the first resistance R1and the second resistance R2. The abnormality detector30may determine that an abnormality occurs when a ratio ISC1/ISC2of the intensity of the blue excitation light20and the intensity of the yellow fluorescent light exceeds a predetermined determination value (R2/R1).

The scope of the present invention includes various circuits which can be perceived from the block diagram ofFIG. 3. In the below, specific configuration examples are described.

First Configuration Example

FIG. 5is a circuit diagram showing an abnormality detector30A according to a first configuration example.

In this configuration example, the first photo sensor32includes a first photo diode PD1and a first color filter CF1. The first color filter CF1is configured such that a transmittance thereof is high with respect to a blue light having the wavelength of the excitation light20and is low with respect to the wavelength of the fluorescent light22. The second photo sensor34includes a second photo diode PD2and a second color filter CF2. The second color filter CF2is configured such that a transmittance thereof is high with respect to green to red light in the wavelength region of the fluorescent light22and is low with respect to the blue light. As the first color filter CF1, a blue filter may be used, and as the second color filter CF2, a yellow filter, a green filter or a red filter may be used.

The first current-voltage conversion circuit36includes a first operational amplifier OA1in addition to the first resistance R1. The first photo sensor32is connected to an inverting input terminal (−) of the first operational amplifier OA1and a fixed voltage is applied to a non-inverting input terminal (+). The fixed voltage is a ground voltage, for example. The first resistance R1is provided between the inverting input terminal (−) and an output terminal of the first operational amplifier OA1.

More specifically, a cathode of the first photo diode PD1of the first photo sensor32is connected to the inverting input terminal (−) of the first operational amplifier OA1, and the fixed voltage (ground voltage) is applied to an anode of the first photo diode PD1.

A voltage of the first detection signal V1generated by the first current-voltage conversion circuit36is expressed by an equation (3).
V1=R1×ISC1(3)

The second current-voltage conversion circuit38includes a second operational amplifier OA2in addition to the second resistance R2and is configured similarly to the first current-voltage conversion circuit36, and a voltage of the output V2thereof is expressed by an equation (4).
V2=R2×ISC2(4)

The determination unit40includes a voltage comparator CMP1configured to compare the voltages of the first detection signal V1and the second detection signal V2. The abnormality detection signal S1which is output from the voltage comparator CMP1is a low level (negate) when V1<V2, i.e., the fluorescent substance14is normal, and is a high level (assert) when V1>V2, i.e., the fluorescent substance14is abnormal.

The abnormality detector30aofFIG. 5may be configured as a small-scale circuit including two operational amplifiers, two resistances and one comparator, in addition to the two photo diodes. A current-voltage conversion gain (transimpedance) of each of the first current-voltage conversion circuit36and the second current-voltage conversion circuit38depends only on the first resistance R1and the second resistance R2. Therefore, it is possible to reduce an influence of variation of elements, so that it is possible to detect the abnormality with high precision.

Further, according to the first current-voltage conversion circuit36ofFIG. 5, due to the virtual ground of the first operational amplifier OA1, the ground voltage is applied to each of the anode and cathode of the first photo diode PD1such that a potential difference between the anode and cathode of the first photo diode PD1becomes substantially zero. Therefore, it is possible to detect the light without an influence of a dark current in a wide range of the amount of light. The second current-voltage conversion circuit38is also the same.

Second Configuration Example

FIG. 6is a circuit diagram showing an abnormality detector30baccording to a second configuration example.

Regarding the first current-voltage conversion circuit36, an inverting input terminal (−) of a first operational amplifier OA21is connected with the anode of the first photo diode PD1, and a non-inverting input terminal (+) of the first operational amplifier OA21is connected with the cathode of the first photo diode PD1and is applied with a predetermined fixed voltage. For example, the fixed voltage may be a power supply voltage VCC, or the other voltage.

A voltage of a first detection signal V21generated by the first current-voltage conversion circuit36ofFIG. 6is expressed by an equation (5).
V21=VCC−R21×ISC1(5)

The second current-voltage conversion circuit38is configured similarly to the first current-voltage conversion circuit36, and a voltage of an output V22thereof is expressed by an equation (6).
V21=VCC−R22×ISC2(6)

FIG. 7Ashows a relation among the output light intensity, the first detection signal V21and the second detection signal V22when the fluorescent substance14is normal, andFIG. 7Bshows the relation among the output light intensity, the first detection signal V21and the second detection signal V22when the fluorescent substance14is abnormal. As described above, the resistance values of the resistances R21, R22are determined to satisfy the relation equations (1) and (2). Therefore, when the fluorescent substance is normal, V21becomes larger than V22, and when the fluorescent substance is abnormal, V22becomes larger than V21. A voltage comparator CMP21ofFIG. 6sets the abnormality detection signal S1to the low level (negate) when V21>V22, i.e., when the fluorescent substance is normal, and sets the abnormality detection signal S1to the high level (assert) when V21<V22.

According to the configuration example, it is possible to achieve the same effects as the abnormality detector30ofFIG. 5.

Third Configuration Example

Returning toFIGS. 4A and 4B, according to the first configuration example ofFIG. 5, since the detection currents ISC1, ISC2are small in a region where the output light intensity is low, the first detection signal V21and the second detection signal V22approximate. Therefore, when the noise, the variation of elements, offset voltages of the operational amplifier and the voltage comparator, and the like (hereinafter, referred to as error factors) are non-negligibly large, the magnitude relation of the first detection signal V21and the second detection signal V22are reversed in the range where the output light intensity is low, so that an abnormality may be falsely detected or an abnormality cannot be detected even though an abnormality occurs. As can be seen fromFIGS. 7A and 7B, similar problem may be also caused in the second configuration example ofFIG. 6.

Therefore, according to a third configuration example, the determination unit40is configured to offset at least one of the first detection signal V21and the second detection signal V22in a direction of separating away from each other and to determine whether an abnormality occurs based on the detection signals V21, V22after the offset.

FIG. 8Ais a circuit diagram of an abnormality detector30caccording to the third configuration example. A determination unit40cincludes voltage-dividing circuits R11, R12in addition to the voltage comparator CMP21. The voltage-dividing circuits R11, R12are configured to voltage-divide the second detection signal V22. The voltage comparator CMP21is configured to compare a second detection signal V32after the voltage division and the first detection signal V21and to generate the abnormality detection signal S1.

FIG. 9Ashows a relation among the output light intensity, the first detection signal V21and the second detection signal V22in the abnormality detector30cofFIG. 8Awhen the fluorescent substance14is normal. In the abnormality detector30c, the second detection signal V32after the voltage division is expressed by an equation (7).

That is, a y-intercept of the second detection signal V32inFIG. 9Ais offset in the direction of separating from the first detection signal V21. An offset width ΔV is VCC×R11/(R11+R12) and can be set by the resistances R11, R12. For example, it is assumed that the offset voltage of the voltage comparator CMP21is dominant as the error factor. In this case, the offset width ΔV is preferably slightly greater than the offset voltage of the voltage comparator CMP21(for example, 20 mV).

In this way, according to the third configuration example, it is possible to increase the detection precision in the range where the output light intensity is low. Particularly, inFIG. 8A, since the two resistances R11, R12of the voltage-dividing circuit have only to be inserted, it is possible to increase the detection precision at low costs and with a small area.

Also, as described above, an absolute value of a gradient of the second detection signal V32after the voltage division is reduced by the voltage-dividing circuits R11, R12, as compared to a configuration where the voltage-dividing circuit is not provided. Therefore, in a region A of steady lighting where the output light intensity is somewhat high, the influence of the offset width ΔV by the voltage-dividing circuit is sufficiently reduced, as compared to the region where the output light intensity is low, and the influence on the detection value can be negligible.

When the voltage-dividing circuits R11, R12are introduced and the resistance value of the second resistance R22is optimized, the gradient of the second detection signal V32and the offset width ΔV can be independently and arbitrarily set.

FIG. 8Bis a circuit diagram of an abnormality detector30daccording to a fourth configuration example. A determination unit40dincludes voltage-dividing circuits R13, R14in addition to the voltage comparator CMP1. The voltage-dividing circuits R13, R14are configured to voltage-divide the second detection signal V2and the power supply voltage VCC. The voltage comparator CMP1is configured to compare a second detection signal V2′ after the voltage division and the first detection signal V1and to generate the abnormality detection signal S1.

FIG. 9Bshows a relation among the output light intensity, the first detection signal V1and the second detection signal V2′ in the abnormality detector30dofFIG. 8Bwhen the fluorescent substance14is normal. In the abnormality detector30d, the second detection signal V2′ after the voltage division is expressed by an equation (8).

That is, a y-intercept of the second detection signal V2′ inFIG. 9Bis offset in the direction of separating from the first detection signal V1. The offset width ΔV is R14·VCC/(R13+R14) and can be set by the resistances R13, R14. Also in the fourth configuration example, it is possible to achieve the same effects as the third configuration example.

Subsequently, modified illustrative embodiments of the first illustrative embodiment are described.

First Modified Illustrative Embodiment

In the illustrative embodiment, the determination unit40is configured by the voltage comparator CMP1. However, the present invention is not limited thereto. For example, the determination unit40may include an A/D converter configured to convert the first detection signal V1and the second detection signal V2into digital values D1, D2, and may be configured to determine whether an abnormality occurs by performing digital signal processing for the digital values D1, D2.

Second Modified Illustrative Embodiment

The method of introducing the offset width ΔV is not limited to the voltage-dividing circuits R11, R12. For example, the comparator CMP1may be configured to adjust an input offset voltage, and at least one of the first detection signal V1and the second detection signal V2may be offset. In this case, it is possible to prevent the false detection due to the error factors such as the noise.

Third Modified Illustrative Embodiment

In the abnormality detector30aofFIG. 5, it is also effective to offset at least one of the first detection signal V1and the second detection signal V2. Specifically, the second detection signal V2ofFIG. 4Amay be offset in a positive direction. In order to realize this, the fixed voltage corresponding to the offset width ΔV may be applied to the non-inverting input terminal (+) of the first operational amplifier OA1.

Fourth Modified Illustrative Embodiment

FIG. 10is a block diagram of a vehicle lamp device1baccording to a fourth modified illustrative embodiment. The vehicle lamp device1bincludes a plurality of (two, in this illustrative embodiment) abnormality detectors30. As the abnormality detector30, any one described in the first illustrative embodiment and the modified illustrative embodiments thereof may be used. The two abnormality detectors30may have the same configuration or the abnormality detectors having different configurations may be combined.

The lighting circuit200is input with abnormality detection signals S1_1, S1_2, which are the outputs of the respective abnormality detectors, through separate routes. The lighting circuit200is configured to function as a failure latch for the plurality of abnormality detection signals S1_1, S1_2, and to execute protection processing when any one indicates an abnormality. As described above, in the protection processing, the lighting circuit200may stop the supply of the driving current ILDsuch that the laser diode12is turned off when any one abnormality detection signal S1is asserted.

Similarly, according to the fourth modified illustrative embodiment, the plurality of abnormality detectors30are provided, and the plurality of abnormality detection signals S1obtained therefrom is applied to the failure latch for protection of the lighting circuit200through the separate routes. Thereby, even when a failure occurs in the abnormality detector30of any system, since it is possible to detect the abnormality in the separate system, it is possible to increase the robustness.

Meanwhile, in the fourth modified illustrative embodiment, one terminal for failure latch of the lighting circuit200may be configured and collectors of transistors Tr1, Tr2provided at output terminals of the plurality of abnormality detectors30_1,30_2may be commonly connected to the terminal for failure latch. In this case, the transistors Tr1, Tr2configure an OR circuit, and the protection processing is performed when at least one of the abnormality detectors30detects the abnormality.

Subsequently, a package of the first photo diode PD1and the second photo diode PD2for abnormality detection is described.

When the photo diode is used for vehicle, a CAN package is adopted so as to secure the long-term reliability under severe environments where the photo diode is exposed to the high temperature and humidity and the thermal shock. Here, when the two photo diodes are accommodated in one package, the cathodes are commonly connected and are electrically connected to a metallic case.

Here, when it is desired to use a pair of photo diodes of which cathodes are common and which is accommodated in the CAN package, it is not possible to adopt the non-inverting current-voltage conversion circuits36,38ofFIG. 5, and it is necessary to adopt the inverting current-voltage conversion circuit36,38shown inFIGS. 6 and 8A. In this case, when a pair of photo diodes of the CAN package is used for the abnormality detectors30b,30cofFIGS. 6 and 8A, since the potential of the cathode becomes the power supply voltage VCC, a potential of the metallic case also becomes the power supply voltage VCC. Here, a metallic structure in the lamp device is grounded in many cases as the measures against the electromagnetic noise. Therefore, when the metallic case is contacted to the surrounding metallic structure, a short occurs between the power supply and the ground, so that the photo diodes cannot operate and the other circuit blocks sharing the power supply voltage VCCcannot also operate.

Therefore, in the abnormality detectors30b,30cofFIGS. 6 and 8A, the photo diodes PD1, PD2are accommodated in a photo diode module100having the following structure.FIG. 11Ais an equivalent circuit diagram of the photo diode module100including the pair of photo diodes PD1, PD2, andFIG. 11Bis a pictorial sectional view thereof. The photo diode module100includes anode terminals A1, A2, a cathode terminal K, two photo diodes PD1, PD2and a metallic case102. The metallic case102is electrically insulated from the cathode terminal K. The metallic case is formed with an opening104on its upper surface, and the light can be incident to the photo diodes PD1, PD2. A light receiving part of each of the photo diodes PD1, PD2may be covered with a color filter.

Here, in a utility of the abnormality detector30, since the current flowing through the photo diodes PD1, PD2is very small such as μA order and the input impedance of the current-voltage conversion circuit is very high, it can be said that the noise resistance is low. Therefore, the photo diode module100is preferably provided with a case terminal C electrically connected to the metallic case102. In this case, when the terminal C is grounded, the metallic case102functions as a shield, so that it is possible to increase the resistance against the electromagnetic noise.

Second Illustrative Embodiment

FIG. 12is a block diagram of a vehicle lamp device1having an abnormality detector50according to a second illustrative embodiment. The vehicle lamp device1includes the light source10and the abnormality detector50configured to detect an abnormality of the light source10. The light source10is similar to that in the first illustrative embodiment and is configured to generate the white output light24including the spectra of the excitation light20and the fluorescent light22.

The abnormality detector50is configured to receive a part of the output light24and to determine whether an abnormality occurs in the light source10, more specifically, whether an abnormality occurs in the fluorescent substance14. The abnormality of the fluorescent substance14may be, for example, breaking, removal, aging deterioration and the like of the fluorescent substance14, but not limited to those.

The abnormality detector50includes a diffraction element52, a light detector54and a determination unit56.

The diffraction element52is configured to diffract the output light24of the light source10. For example, the diffraction element52may be a transmission type or a reflection type diffraction grating. The light detector54is configured to detect a diffracted light26of the diffraction element52. The determination unit56is configured to determine whether an abnormality occurs based on a detection result of the light detector54.

The above is the basic configuration of the abnormality detector50. Subsequently, an operation principle thereof is described.

FIG. 13Ashows the diffracted light when the fluorescent substance is normal, andFIG. 13Bshows the diffracted light when the fluorescent substance is abnormal.

When the fluorescent substance14is normal, the excitation light20is scattered by the fluorescent substance14. Therefore, the excitation light20incident to the diffraction element52is lowered in coherency, so that a substantial interference fringe is not observed in the diffracted light26obtained by the diffraction element52(FIG. 13A). On the other hand, when the fluorescent substance14is abnormal, the excitation light20is not scattered and is coherently incident to the diffraction element52. Therefore, a substantial interference fringe is observed in the diffracted light26obtained by the diffraction element52(FIG. 13B).

Therefore, according to the abnormality detector50, it is possible to determine whether the fluorescent substance14is abnormal based on the diffracted light26obtained by the diffraction element52, more specifically, depending on whether the substantial diffraction pattern (interference fringe) is observed.

The scope of the present invention includes various circuits which can be perceived from the block diagram ofFIG. 12. In the below, specific configuration examples are described.

First Configuration Example

FIG. 14illustrates a vehicle lamp device1aincluding an abnormality detector50aaccording to a first configuration example. The vehicle lamp device1aincludes the light source10, a reflector2configured to reflect the emission light24of the light source10and a lens4configured to receive the emission light24reflected on the reflector2and to emit the same to the front of the lamp device. The reflector2is formed with a pinhole. The reflector2is provided on its backside with the diffraction element52, and a part of the light passing through the pinhole58of the emission light24reaches the diffraction element52. A size (opening area) of the pinhole58is not particularly limited.

The light detector54is configured to detect the light intensities of two points, i.e., a first position A at which a pattern of the diffracted light26has a peak when the fluorescent substance14is normal and a second position B at which there is no peak when the fluorescent substance14is normal. For example, the light detector54includes two photo sensors PS1, PS2provided at the two positions A, B. The light detector54is configured to be sensitive to the blue light, which is the excitation light20, and is preferably insensitive to the yellow light, which is the fluorescent light.

The determination unit56is configured to determine whether an abnormality occurs based on the light intensities at the two points. More specifically, the determination unit56may determine that the fluorescent substance14is abnormal when a difference of outputs of the two photo sensors PS1, PS2exceeds a predetermined threshold.

Alternatively, the determination unit56may be configured to determine whether an abnormality occurs based on a ratio of the light intensities, instead of the difference of the light intensities at the points A, B. In this case, it is possible to determine whether an abnormality occurs irrespective of the output light intensity of the light source10. Alternatively, the determination unit56may be configured to determine whether an abnormality occurs by a combination of the difference and the ratio.

Instead of the configuration where the reflector2is formed with the pinhole58, a part of the reflector2may be made to have a lower reflectivity so that the output light24of the light source10can penetrate therethrough.

FIGS. 15A and 15Bare circuit diagrams showing specific configuration examples of the determination unit56.

The determination unit56ofFIG. 15Aincludes a differential calculating unit60and a voltage comparator CMP2. The differential calculating unit60is configured to receive a detection signal Vs1from the photo sensor PS1and a detection signal Vs2from the photo sensor PS2and to amplify a difference thereof. The configuration of the differential arithmetic unit60is not particularly limited and a known configuration may be used. The voltage comparator CMP2is configured to compare an output voltage V3of the differential calculating unit60and a predetermined threshold voltage VTH. The output (abnormality detection signal S1) of the voltage comparator CMP2is negated when the difference of the outputs of the two photo sensors is smaller than the threshold, and is asserted when the difference is larger than the threshold. In this configuration example, a negative logic system is adopted, and a low level is allotted to the assert and a high level is allotted to the negate.

The determination unit56may be configured by a digital circuit. The determination unit56ofFIG. 15Bincludes A/D converters62,64, a subtractor66and a comparator68. The A/D converters62,64are configured to convert the detection signals Vs1, Vs2of the photo sensors PS1, PS2into digital signals Ds1, Ds2. The A/D converter64is configured to calculate a differential signal S3of the digital signals Ds1, Ds2. The comparator68is configured to determine whether an abnormality occurs by comparing the differential signal S3and the threshold TH.

Second Configuration Example

FIG. 16is a circuit diagram showing an abnormality detector50baccording to a second configuration example. A light detector54bincludes a plurality of pixels55configured to receive the diffracted light26. The light detector54bcan use a CCD or CMOS sensor and may be combined with a color filter. The light detector54bmay be a line sensor including a plurality of pixels arranged in one dimensional shape or may be a matrix array sensor including a plurality of pixels arranged in a matrix shape.

The determination unit56bis configured to determine whether an abnormality occurs based on a pattern of the diffracted light26measured by the plurality of pixels55. In the below, some determination methods by the abnormality detector50bare described.

For example, pixels, which correspond to the points A, B ofFIG. 14, of the plurality of pixels55may be used as the photo sensors PS1, PS2ofFIG. 14. In this case, the processing of the determination unit56bis as described above.

Alternatively, there may be employed a method which includes acquiring a pattern of the diffracted light26by using all or some of the plurality of pixels55, comparing the acquired pattern and a predetermined diffraction pattern, detecting whether an interference fringe exists by determining how the patterns are matched, and determining whether an abnormality occurs.

Alternatively, the determination unit56may be configured to determine whether an abnormality occurs by executing arithmetic processing for data of the diffracted light26measured by the light detector54b.FIG. 17Ashows an output S4of the light detector54band differential data S5thereof when the fluorescent substance14is abnormal, andFIG. 17Bshows the output S4of the light detector54band differential data S5thereof when the fluorescent substance14is normal.

A configuration of differentiating the output S4of the light detector54bis equivalent to a configuration of spatially differentiating data measured by the plurality of pixels55, and an edge of the interference fringe can be detected by the differential processing. Also, it is possible to determine whether the fluorescent substance14is abnormal by comparing the differential data S5and the predetermined threshold TH to determine whether the substantial interference fringe occurs. In the meantime, the threshold TH may be provided in a negative direction. In this case, it is possible to detect an edge opposite to the interference fringe. Alternatively, the threshold TH may be set at both positive and negative sides.

FIG. 18is a circuit diagram showing a configuration example of the determination unit56b. The determination unit56bincludes a differentiator70configured to spatially differentiate the data S4, which indicates the diffracted light26. The data S4obtained from the plurality of pixels55of the light detector54bmay be sequentially read from an end. At this time, the spatial differentiation is equivalent to a configuration of temporally differentiating the data S4sequentially read from the plurality of pixels55. Therefore, the differentiator70may be configured by a differential amplifier (high-pass filter) configured to differentiate the analog data signal S4. The differential amplifier (high-pass filter) mainly includes a resistance R21, a capacitor C21and an operational amplifier OA3.

The voltage comparator72is configured to compare an output signal S5of the differentiator70and the threshold VTH, and outputs a low level when S5>VTH, and a high level when S5<VTH. A subsequent stage of the voltage comparator72may be provided with a final determination circuit74including a filter, a timer and the like. The final determination circuit74determines that the fluorescent substance14is abnormal and asserts (high level) the abnormality detection signal S1when the output of the voltage comparator72keeps the low level for a predetermined determination time period.

When the signal S4from the light detector54bincludes many noises, the noise is amplified by the differentiator70so that the S/N ratio may be lowered. Therefore, the differentiator70may be added with a resistance R22(R11>R22) and a capacitor C22(C21>C22) configured to form a weak integrator (low-pass filter) together with the operational amplifier OA3. Thereby, it is possible to remove the noise and to thus increase the S/N ratio.

InFIG. 18, the determination unit56bof the analog circuit is shown. However, it is understood that one skilled in the art can implement processing equivalent thereto by a digital circuit. Specifically, there may be used a method which includes converting the analog detection signal S4from the light detector54binto a digital value by the A/D converter, differentiating the digital value and comparing the same and a threshold to determine whether an abnormality occurs.

Finally, a utility of the vehicle lamp device1is described.FIG. 19is a perspective view of a lamp unit (lamp assembly)500having the vehicle lamp device1according to the illustrative embodiments. The lamp unit500includes a transparent cover502, a high beam unit504, a low beam unit506and a housing508. The vehicle lamp device1may be used for the high beam unit504, for example. The vehicle lamp device1includes the one or more light sources10. Instead of the high beam unit504or in addition to the high beam unit504, the vehicle lamp device1may be used for the low beam unit506.

Although the present invention has been described using the specific expressions based on the illustrative embodiments, the illustrative embodiments are provided only to describe the principle and application of the present invention, and various modified embodiments and changes in the arrangement can be made without departing from the spirit of the present invention defined in the claims.