Ultraviolet light detection device

A detector made of lanthanum-doped lead zirconate titanate detects intensity of ultraviolet light radiated inside of a vehicle. The detector sends ultrasonic wave to an incidence direction of ultraviolet light, and detects ultrasonic wave reflected by an object. An electrical unit determines the object to be an occupant of the vehicle or not based on the reflected ultrasonic wave. The electrical unit outputs a signal representing that a predetermined or more amount of ultraviolet light is radiated to the occupant, when the detector detects the predetermined or more amount of ultraviolet light and when the electrical unit determines the object to be the occupant.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2006-247053 filed on Sep. 12, 2006, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ultraviolet light detection device for detecting ultraviolet light radiated to an occupant of a vehicle.

2. Description of Related Art

A large amount of ultraviolet light radiated from the sun may affect human health, so that it is recommended that human should not be exposed to too much ultraviolet light. However, when human is in a vehicle traveling outside, the human has to be exposed to ultraviolet light, because ultraviolet light is radiated inside of the vehicle through a window glass.

In order to reduce the radiation of ultraviolet light into the vehicle, a colored glass capable of blocking or absorbing sunlight is used as the window glass. However, a deep-colored glass hinders vision of a driver of the vehicle at night or under bad weather, so that the deep-colored glass may affect safety driving by the driver.

Here, JP-A-8-207569 discloses a sunlight-adjusting device for a vehicle. An occupant, e.g., driver, of the vehicle operates the device, if necessary, to adjust a light-transmitting rate of a window glass of the vehicle by changing an applied voltage. Thereby, ultraviolet light radiated to the occupant can be reduced, and vision of the driver can be secured.

However, because ultraviolet light is not visible light, the occupant cannot accurately determine the radiated ultraviolet light to be strong or weak. That is, the occupant sensuously estimates intensity of the radiated ultraviolet light based on brightness of outside. Therefore, the occupant may inappropriately operate the device, although strong ultraviolet light is radiated to the occupant.

SUMMARY OF THE INVENTION

In view of the foregoing and other problems, it is an object of the present invention to provide an ultraviolet light detection device.

According to an example of the present invention, an ultraviolet light detection device detects ultraviolet light radiated to an occupant of a vehicle. A detecting element includes an ultraviolet detector made of lanthanum-doped lead zirconate titanate (PLZT), and detects intensity of ultraviolet light radiated inside of the vehicle. An electrical unit outputs an ultraviolet light detection signal representing that a predetermined or more amount of ultraviolet light is radiated to the occupant. The ultraviolet detector sends ultrasonic wave to an incidence direction of ultraviolet light, and detects ultrasonic wave reflected by an object to be detected. The electrical unit outputs the ultraviolet light detection signal when the detecting element detects the predetermined or more amount of ultraviolet light and when the object is determined to be the occupant of the vehicle based on the reflected ultrasonic wave.

Accordingly, intensity of the ultraviolet light radiated to the occupant of the vehicle can be detected. For example, when the predetermined or more amount of ultraviolet light is radiated, the ultraviolet light detection device may activate a device for blocking ultraviolet light.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

First Embodiment

As shown inFIGS. 1A and 1B, an ultraviolet light detection device1is mounted to a vehicle80, and includes a detecting element10and an electronic control unit21(ECU). The detecting element10detects ultraviolet light, and sends and receives ultrasonic wave. The ECU21determines that an occupant exists in the vehicle80or not based on a signal output from the detecting element10. Further, the ECU21outputs a radiation signal, when ultraviolet light having intensity equal to or larger than a threshold value is determined to be radiated and when the occupant is determined to exist in the vehicle80. The radiation signal represents that the ultraviolet light having intensity equal to or larger than the threshold value is radiated to the occupant in the vehicle80.

The detecting element10is arranged on an inner face40aof a front windshield40of the vehicle80. A rearview mirror81and a steering wheel82are shown to indicate the position of the detecting element10. The detecting element10is located at a position to be able to detect each of an occupant on a driver seat and an occupant on a passenger seat in the vehicle80. In this embodiment, the detecting element10is arranged at each top position in front of the driver seat and the passenger seat.

The ECU21is arranged in an engine compartment of the vehicle80, and is constructed with a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), an input-output interface (I/O), and an application specified integrate circuit (ASIC) type microcomputer having a communication interface (which are not shown). The CPU is connected to the detecting element10through the I/O or communication interface.

As shown inFIG. 2, the detecting element10is constructed by a rectangular semiconductor board11having a silicon on insulator (SOI) structure. The semiconductor board11is made of a material capable of transmitting ultraviolet light. A first insulation film11b,a silicon active layer11cand a second insulation film11dare layered in this order on a support member11amade of silicon, to construct the semiconductor board11. An approximately center part of the support member11aand the first insulation film11bis removed in a rectangular shape using a micro electro mechanical system (MEMS) technology. Thereby, the support member11ais a flat plate having the center part eliminated in the rectangular shape, and the first insulation film11bis a thin film having the center part eliminated in the rectangular shape. Each of the silicon active layer11cand the second insulation film11dis a thin rectangular film, whose center part is not eliminated.

For example, in order to form the semiconductor board11, the first insulation film11bis formed on a silicon board, i.e., the support member11a,then, a poly-silicon film is formed on the first insulation film11bas the silicon active layer11c.Thereafter, ion injection is performed to the poly-silicon film to activate, and the second insulation film11dis formed on the silicon active layer11c.Alternatively, an indium tin oxide (ITO) board or quartz board may be used as the semiconductor board11. In this case, an amount of transmitting ultraviolet light can be increased compared with a case in which the semiconductor board11is used. Further, because the ITO board can also work as a bottom electrode, ultraviolet light can be detected from the both sides (top and bottom) of the ITO board.

A detector12is formed on the second insulation film11dto cover the thinly formed part, i.e., silicon active layer11cand second insulation film11d.The detector12has a piezoelectric property and a photostrictive characteristic generated by ultraviolet light, which represents that the detector12is distorted when ultraviolet light is radiated to the detector12. The detector12is constructed by a piezoelectric membrane made of lanthanum-doped lead zirconate titanate (PLZT). An electrode13is electrically connected to the detector12.

Thereby, the thinly formed part and the detector12construct a membrane15having a predetermined resonance frequency. Ends of the membrane15are supported by the support member11a.

The detector12sends ultrasonic wave to an object to be detected, and receives ultrasonic wave reflected by the object. The membrane15is displaced because the membrane15resonates with the received ultrasonic wave. The detector12transforms the displacement of the membrane15generated by the resonance into a voltage signal, so that the received ultrasonic wave can be detected. That is, the detector12can detect ultrasonic wave.

Further, because the detector12has the photostrictive characteristic, the detector12can detect intensity of ultraviolet light radiated to the detector12. That is, the detector12can further detect ultraviolet light, in addition to ultrasonic wave.

The detecting element10is fitted to the inner face40aof the front windshield40through the support member11asuch that the detector12faces, i.e., opposes to, the occupant of the vehicle80.

A cover90is disposed at the occupant side of the detecting element10. The cover90has a mesh part, i.e., hole, capable of transmitting ultrasonic wave. The cover90protects the detecting element10from a load of an outer force. However, the cover90may be eliminated when the detecting element10is located at a position such that the occupant has little chance to touch the detecting element10.

Further, the detecting element10may be disposed in a box case capable of transmitting ultraviolet light, and the box case may be fitted to the front windshield40.

As shown inFIG. 3A, ultrasonic wave starts to be sent from the detector12to the occupant at time t1, and ultrasonic wave reflected by the occupant reaches the membrane15of the detecting element10and vibrates the membrane15from time t2to time t3. Due to the vibration of the membrane15, a voltage signal output from the detector12into the ECU21varies with wave shape from time t2to time t3, so that the reflected ultrasonic wave can be detected. Here, a distance to an object, e.g., occupant, to be detected can be calculated based on a time period T1(i.e., t2−t1). The ECU21can determine the object to be the occupant or not based on the calculated distance and a variation V1of an output value of the voltage signal.

The above-described determination is performed by using single result of the calculated distance. However, the determination may be performed by using plural results of the calculated distance. When the occupant is not on a seat of the vehicle80, the seat is detected as the object to be measured. Because the seat is fixed to the vehicle80, the plural results of the calculated distance are approximately uniform. In contrast, when the occupant is detected as the object to be measured, the plural results of the calculated distance vary, because the occupant usually makes some movements. Thus, the ECU21can determine the object to be the occupant.

Ultraviolet light is radiated from outside into the vehicle80through the front windshield40, and reaches the detector12through the membrane15. Because the lanthanum-doped lead zirconate titanate (PLZT) constructing the detector12has the photostrictive characteristic, the detector12is distorted when ultraviolet light is radiated to the detector12. Then, an electrical signal corresponding to the distortion of the detector12is output. That is, as shown inFIG. 3B, an output value of the electrical signal increases by a variation V2corresponding to an intensity of ultraviolet light from time t4to time t5, in which ultraviolet light is radiated to the detector12.

The detector12has two normal line directions, and a direction for sending and receiving ultrasonic wave to detect the occupant by the detector12is a direction heading the occupant. In contrast, a direction for detecting ultraviolet light by the detector12is a direction heading outside of the vehicle80. The direction for detecting the occupant is opposite to the direction for detecting ultraviolet light. Therefore, the detector12detects ultrasonic wave and ultraviolet light on approximately the same line (normal line of the detector12). Thus, the detector12can detect an amount of ultraviolet light radiated to the occupant detected by the ultrasonic wave.

Next, a flow of the ultraviolet light detection treatment performed by the microcomputer of the ECU21of the ultraviolet light detection device1will be described with reference toFIGS. 4 and 5. In the ultraviolet light detection treatment, the CPU of the microcomputer repeatedly performs an ultraviolet light detection program stored in the ROM of the microcomputer every predetermined period, e.g., one second or one minute, using a timer interrupt function, for example.

As shown inFIG. 4, at step S101, the ECU21obtains parameters, e.g., V1, V2, T1, based on the detection signals output from the detecting element10, after a predetermined initializing process. Specifically, the ECU21obtains a parameter of the output value V2corresponding to the intensity of ultraviolet light, a parameter of the output value T1used for calculating the distance to the object to be detected, and a parameter of the output value V1corresponding to the intensity of ultrasonic wave reflected by the object based on the detection signals shown inFIG. 5.

At step S103, the ECU21determines the output value V2corresponding to the intensity of ultraviolet light to be larger than a threshold Vs corresponding to an allowed intensity of ultraviolet light (V2>Vs) or not.

When the ECU21determines the output value V2to be larger than the threshold Vs (Yes at S103), ultraviolet light having intensity larger than the allowed intensity determines to be radiated into the vehicle80. Then, the ECU21proceeds to step S105. In contrast, when the ECU21determines the output value V2to be equal to or smaller than the threshold Vs (No at S103), the ECU21does not output the ultraviolet light detection signal because the intensity of ultraviolet light is low. Then, the ultraviolet light detection treatment is finished.

At step S105, the ECU21determines the occupant to exist at the radiation direction of ultraviolet light or not, based on the output value T1used for calculating the distance to the object and the output value V1corresponding to the intensity of ultrasonic wave reflected by the object, which are obtained at step S101.

When the ECU21determines the occupant to exist (Yes at S105), the ECU21proceeds to step S107. In contrast, when the ECU21determines the occupant not to exist (No at S105), the ECU21does not output the ultraviolet light detection signal, and the ultraviolet light detection treatment is finished.

At step S107, the ECU21outputs the ultraviolet light detection signal. When the ECU21determines the occupant to exist at the radiation direction of ultraviolet light at S105, the ECU21outputs the ultraviolet light detection signal. Thereby, a treatment for blocking the ultraviolet light radiated to the occupant may be performed. For example, the ultraviolet light detection signal is output into an alarm unit (not shown). The alarm unit indicates the detection of ultraviolet light to the occupant with sound information or alarm buzzer to promote the occupant to close window, wear a jacket or wear sunglasses.

When the ultraviolet light detection signal is output into a controller (not shown) for controlling window glass, the controller activates a UV cutting function of the window glass. For example, the window glass contains a material capable of reflecting ultraviolet light, e.g., TiO2. When the ultraviolet light detection signal is output, electrophoretic migration is performed to orient the TiO2, so that ultraviolet light can be blocked. Alternatively, an electric-colored glass may be used for the window glass. The electric-colored glass is colored by applying a voltage. Further, a UV filter may be inserted into the window glass in order to block ultraviolet light.

After the ultraviolet light detection signal is output at step S107, the ultraviolet light detection treatment is finished. In the above-described treatment, step S103is performed earlier than step S105. However, step S105may be performed earlier than step S103.

As shown inFIG. 6, the detecting element10may be arranged on each side windshield or rear windshield. In this case, because ultraviolet light radiated to an occupant on a rear seat can be detected, the occupant on the rear seat can be restricted from being exposed to ultraviolet light having strong intensity. Further, the occupant on the front seat can be protected from ultraviolet light radiated through the side windshield in addition to ultraviolet light radiated through the front windshield.

According to the first embodiment, the ultraviolet light detection device1includes the detecting element10having the detector12made of the lanthanum-doped lead zirconate titanate (PLZT) with the photostrictive (light-distorting) characteristic and the piezoelectric property. Therefore, the detecting element10can detect intensity of ultraviolet light radiated into the vehicle80. The detecting element10further sends ultrasonic wave toward the radiation direction of ultraviolet light, and detects ultrasonic wave reflected by the object to be detected. The ECU21outputs the ultraviolet light detection signal, when the detecting element10detects ultraviolet light having intensity larger than the predetermined amount and when the ECU21determines the object to be the occupant of the vehicle80based on the detection result of ultrasonic wave reflected by the object. The ultraviolet light detection signal represents that the predetermined or more amount of ultraviolet light is radiated to the occupant.

Because the detector12of the detecting element10detects both of the ultrasonic wave and the ultraviolet light on approximately the same line, the detector12can detect the intensity of ultraviolet light radiated to the occupant detected by the ultrasonic wave from outside of the vehicle80. When the predetermined or more amount of ultraviolet light is radiated to the occupant, the ECU21outputs the ultraviolet light detection signal, so that the treatment for blocking the ultraviolet light can be activated.

Thus, the ultraviolet light detection device1can activate the treatment for blocking the ultraviolet light, in a case where the predetermined or more amount of ultraviolet light is radiated to the occupant when the device1detects the intensity of ultraviolet light radiated to the occupant of the vehicle80.

Further, because the single detector12can detect both of the ultrasonic wave and the ultraviolet light, the number of detecting elements10can be reduced, so that a size of the device1can be made smaller.

The semiconductor board11has the membrane15, and a part of the membrane15is thin, on which the detector12is disposed. Therefore, the displacement of the detector12due to the vibration by ultrasonic wave can be increased, so that sensitivity for detecting ultrasonic wave can be improved.

Because the detecting element10is located on the front windshield40, the rear windshield42or the side windshield41, ultraviolet light radiated to the occupant through each of the windshields40,41,42can secure to be detected.

Second Embodiment

As shown inFIGS. 7A and 7B, multiple, e.g., two, detecting elements10a,10bare arranged in an array arrangement in an ultraviolet light detection device2in a second embodiment. Other parts in the second embodiment may be made similar to the first embodiment.

The two detecting elements10a,10bare fitted to the front windshield40such that the detectors12of the two detecting elements10a,10bare arranged on the same semiconductor board11parallel to each other. In this case, not only the distance to the object to be detected but also a position of the object can be measured based on a time difference and a phase difference between ultrasonic waves received by the detecting elements10a,10b.Therefore, the movement of the object can be accurately detected, so that the object can be determined to be the occupant or not more accurately.

Here, when an interval between center points of the membranes15of the adjacent detecting elements10a,10bis approximately equal to an integral multiple of half wavelength of the ultrasonic wave, the time difference can be also detected based on the phase difference. Thus, the time difference can be more accurately detected.

The number of the detecting elements10is not limited to two. For example, four, e.g., two-by-two, detecting elements10may be used as one unit. In this case, the position of the object in an up-and-down direction can be also measured, so that the occupant can be determined to exist or not more accurately.

In the second embodiment, the integrated detecting elements10a,10bare arranged in the ultraviolet light detection device2. Alternatively, individually-produced multiple detecting elements10may be arranged in the device2.

A part of the multiple detecting elements10may be replaced by another detecting element capable of detecting infrared ray. For example, when the detector12of the detecting element10ais made of lead zirconate titanate (PZT), the detector12can detect intensity of heat ray radiated from the object to be detected. Therefore, the detector12can detect both of the ultrasonic wave and the infrared ray. Alternatively, the single detecting element10further includes an infrared detector capable of detecting infrared ray, in addition to the detector12for detecting ultraviolet light. The infrared detector may be disposed opposite to the detector12. For example, the infrared detector is disposed on the semiconductor board11at the occupant side, and the detector12is disposed on the semiconductor11adjacent to the front windshield40. In this case, a size of the device2can be reduced.

Thereby, the temperature of the object can be measured. At step S105ofFIG. 4, the ECU21detects the existence of the object, i.e., occupant. At this time, the temperature of the object can be determined to be in a predetermined range, e.g., between 32° C. and 43° C., or not. When the temperature of the object is in the predetermined range, the object can be determined to be the occupant.

When a surface temperature of a body of the occupant is detected, the occupant can be determined to be in a comfortable state or not. For example, when the surface temperature of the body of the occupant is equal to or larger than a predetermined value, an air-conditioner may be activated to cool.

According to the second embodiment, the multiple detecting elements10a,10bare arranged in the array arrangement such that the detectors12of the multiple detecting elements10a,10bface to approximately the same direction. Therefore, not only the distance to the object to be detected but also the position of the object can be measured based on the time difference and the phase difference between ultrasonic waves received by the detecting elements10a,10b.Thereby, the movement of the object can be accurately detected, so that the object can be determined to be the occupant or not more accurately.

Because the detectors12of the detecting elements10a,10bare disposed on the same semiconductor board11, the detecting elements10a,10bcan be produced in a single process at the same time. Further, cost for manufacturing the device2can be reduced, because the multiple detecting elements10a,10bcan be fitted at the same time.

A part of the multiple detecting elements10may be replaced by an infrared-ray detecting element capable of detecting infrared ray. For example, the detector12of the detecting element10ais made of the lead zirconate titanate (PZT) having a pyroelectric property. In this case, the single detector12of the detecting element10acan detect a heat quantity of the occupant in addition to the reflected ultrasonic wave. Thus, the object can be determined to be the occupant or not with the single detector12of the detecting element10a,so that the object can be determined to be the occupant or not more accurately.

Other Embodiments

As shown inFIG. 8, the detector12may be arranged on the silicon active layer11cadjacent to the support member11a.In this case, ultraviolet light reaches the detector12without passing through the semiconductor board11, so that an opaque board relative to ultraviolet light can be used as the semiconductor board11. Further, sensitivity for detecting ultraviolet light can be improved, because attenuation of ultraviolet light can be reduced.

A semiconductor board having a flat plate shape, that is, a semiconductor board not having the membrane15may be used as the semiconductor board11in the detecting element10. In this case, the manufacturing cost of the detecting element10can be reduced, because the membrane15is not formed on the detecting element10.

Further, the membrane15may be cantilevered (i.e., one-side supported) by the support member11ain the detecting element10. In this case, the membrane15can be easily displaced (deformed) compared with a case in which the membrane15is supported through the both ends. Therefore, the displacement (deformation) of the membrane15can be increased when ultrasonic wave vibration is transmitted thereto, so that sensitivity for detecting ultrasonic wave can be improved.

The detector12formed on the membrane15detects ultrasonic wave and ultraviolet light in the above embodiments. However, any detecting unit may be used as the detector12without departing from the scope of the present disclosure. For example, a capacitive vibration detector60shown inFIG. 9Amay be used in place of the detector12, in which a piezoelectric film for detecting ultraviolet light is formed on a vibration face thereof. The capacitive vibration detector60further detects ultrasonic wave based on a capacitance variation between first and second electrodes16,17. Because the capacitive vibration detector60has a relatively broad resonance frequency band, an allowed production variation is relatively large. Thus, production yield can be increased.

As shown inFIG. 9A, the capacitive vibration detector60includes the first electrode16formed on the first insulation film11b,and the second electrode17opposing to the first electrode16through a predetermined gap. The second electrode17is made of a material capable of transmitting ultraviolet light. A piezoelectric film18is formed on the second electrode17, and detects ultraviolet light and outputs an electrical signal. Here, the piezoelectric film18is made of lanthanum-doped lead zirconate titanate (PLZT).

A through hole16ais provided in the first electrode16in order to reduce affect of air damping by the vibration. A route for transmitting the ultrasonic wave by the capacitive vibration detector60is approximately similar to that by the detector12. When the capacitive vibration detector60receives ultrasonic wave and vibrates, the gap between the first and second electrodes16,17is varied. Thereby, a capacitance of a capacitor constructed with the first and second electrodes16,17is varied, so that the ultrasonic wave can be detected. Ultraviolet light passes through the through hole16aof the first electrode16and the second electrode17, then, reaches the piezoelectric film18.

As shown inFIG. 9B, the first and second electrodes16,17may be interchanged with each other, and the piezoelectric film18may be formed on the second electrode17adjacent to the support member11a.In this case, ultraviolet light is radiated to the piezoelectric film18without passing through the second electrode17, so that attenuation of the ultraviolet light can be reduced.

As shown inFIG. 10, the detecting element10may be fitted to the cover90through the support member11asuch that the detector12opposes to the inner face40aof the front windshield40. In this case, the detecting element10can be protected from a load of an outer force. Further, attenuation of ultraviolet light can be reduced because the ultraviolet light can reach the detector12without passing through the semiconductor board11. Thus, sensitivity for detecting ultraviolet light can be improved.

The detector12may be directly formed on the inner face40aof the front windshield40. In this case, manufacturing cost can be reduced because the semiconductor board11can be eliminated. Further, attenuation of ultraviolet light can be reduced, because ultraviolet light reaches the detector12without passing through the semiconductor board11. Thus, sensitivity for detecting ultraviolet light can be improved.