Emission device

Abstract

To provide an emission device and the like that improve detection accuracy of, for example, vehicles.SOLUTION: A laser inter-vehicle range-finder is mounted to an own vehicle. The laser inter-vehicle range-finder is configured to emit light in an emission direction that is forward or backward; detect other vehicle located in the emission direction. The laser inter-vehicle range-finder comprises an emission unit. The emission unit is configured to have a directional characteristic in which the light is emitted with the light converged to an emission area 40 serving as an area where the light is emitted. The emission area 40 is shaped in which a width of a first portion 401 corresponding to the other vehicle present at a distant location serving as a distant location is smaller than a width in a left / right direction of a second portion 402 corresponding to the other vehicle present at a close location further than the distant location, and on a lower side further than the first portion 401.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an emission device or the like that emits light or the like. [Background technology]

[0002] Conventionally, there are known emission devices that are mounted on automobiles and emit electromagnetic waves. For example, a code modulation type radar ranging device described in Patent Document 1 emits code-modulated or spectrum-spread electromagnetic waves. The code modulation type radar ranging device receives electromagnetic waves reflected by an object to be measured, such as an automobile, with a receiver and calculates the distance to the object. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-83991 Summary of the Invention [Problem to be solved by the invention]

[0004] The electromagnetic waves used to detect the distance to an object to be measured include, for example, infrared light. At the left and right ends and outside of the lane in which the vehicle is traveling (hereinafter simply referred to as the "outside of the lane"), there are reflectors, such as those attached to the center line of the road, roadside strips, and curbs of the sidewalk. For this reason, the light emitted by the above-mentioned emitting device is reflected, in particular, by reflectors attached outside the lane. Therefore, when the emitting device detects a vehicle, it may erroneously detect light reflected by reflectors attached outside the lane, reducing the accuracy of vehicle detection.

[0005] An object of the present invention is to provide, for example, an emission device or the like that improves vehicle detection accuracy. [Means for solving the problem]

[0006] (1) The emission device is mounted on a first vehicle, emits light in an emission direction in front of or behind the first vehicle, and detects a second vehicle located in the emission direction. The emission device has an emission section having directional characteristics that concentrates the light in an emission area, which is an area from which the light is emitted, and the emission area has a shape in which the left-right width of a first part, which is a part corresponding to a distant position, is smaller than the left-right width of a second part, which is a part below the first part.

[0007] When viewed in the emission direction from a light emitting device disposed on a first vehicle traveling along a straight driving lane, the second vehicle is located higher and smaller the farther it is from the light emitting device. Furthermore, the driving lane is located higher and smaller in width in the lateral direction the farther it is from the light emitting device. In the present invention, the lateral width of a first portion of the emission area, which corresponds to the distant position, is smaller than the lateral width of a second portion, which is located below the first portion. The first portion is a portion for detecting the second vehicle when the second vehicle is located far away. The second portion is a portion for detecting the second vehicle when the second vehicle is located close. The emission area is set according to the size of the second vehicle and the lateral width of the driving lane. Therefore, when the emission area is aligned with a straight driving lane, the amount of light from the emission area irradiated onto reflectors outside the driving lane is reduced. Therefore, when detecting a second vehicle by detecting light emitted from the emission device, the possibility of erroneously detecting reflectors outside the driving lane is reduced. This improves the detection accuracy of the second vehicle. In the emission region, the first portion and the second portion may be separated, or the emission region may be continuous from the first portion to the second portion.

[0008] For example, the emission unit includes a generation unit that generates light and an emission lens unit that refracts the light generated by the generation unit and emits the light to the emission area. In this case, the emission device can concentrate the light at the emission area by refracting the light using the emission lens unit. Therefore, the shape of the generation unit does not need to be specially shaped to emit light to the emission area. This reduces the cost of the generation unit. The generation unit may be an LED (Light Emitting Diode). Furthermore, it is particularly preferable for the generation unit to be an LD (Laser Diode). In this case, even if the emission device is attached to the inside of the windshield, the light can pass through the windshield and reach a second vehicle that is farther away.

[0009] Furthermore, the emission area may be rectangular, with at least one of a pair of opposing sides tilting inward toward the center of the emission area as it approaches the top. In this case, the brightness of the light irradiated onto the reflector on at least one side of the lane is likely to be reduced. Therefore, when detecting a second vehicle by detecting light emitted from the emission device, the possibility of erroneously detecting a reflector on the outside of the lane is reduced. This improves the accuracy of detecting the second vehicle.

[0010] (2) In the emitting device, the shape of the emission area, when projected onto a plane normal to the emission direction, may be a trapezoid with the first portion at the top and the second portion at the bottom. When a driving lane is viewed from a emitting device disposed on a first vehicle, the driving lane is trapezoidal. Therefore, the reflector provided on the second vehicle is often located within the trapezoidal area where light is concentrated. Therefore, compared to when the emission area has a shape other than a trapezoid, the brightness of the light irradiated onto the reflector outside the driving lane is likely to be lower, and the brightness of the light irradiated onto the reflector of the second vehicle is likely to be higher. Therefore, when detecting a second vehicle by detecting light emitted from the emitting device, the second vehicle can be detected more reliably.

[0011] The emission area may be triangular or rectangular, with both of the opposing sides tilting inward as they move upward. In this case, the brightness of the light irradiated onto the reflectors on both the left and right sides of the lane tends to decrease. This reduces the possibility of falsely detecting reflectors on the outside of the lane when detecting a second vehicle by detecting light emitted from the emission device. This improves the accuracy of detecting the second vehicle.

[0012] The emission area may be a triangle, which eliminates the influence of reflectors outside the driving lane. However, since the upper vertex of the triangle is a point, there is a high possibility that the second vehicle will not be detected if the first vehicle deviates to the left or right from the center of the driving lane. Therefore, to more reliably detect the first vehicle even if it deviates to the left or right from the center of the driving lane, an upper side is provided and the emission area is made trapezoidal. The length of the upper side of the trapezoidal emission area may be, for example, a length corresponding to the driving lane of the second vehicle at the detection target distance.

[0013] Furthermore, for example, the emitting device may have a mounting portion that can be attached to the first vehicle so that the emission direction is horizontal. It is also preferable that the oblique sides located on the left and right of the trapezoidal emission area are nearly parallel to the left and right lines of the driving lane as seen from the emitting device. For example, if the angles between the left and right oblique sides located on the left and right of the trapezoidal emission area and the base are 45 degrees, the angle between the left and right lines of the driving lane as seen from the emitting device and the left-right direction may be set to 45 degrees. In this case, the brightness of the light irradiated onto the reflector on the outside of the driving lane tends to be reduced, and the brightness of the light irradiated onto the reflector of the second vehicle tends to be increased. Therefore, when detecting a second vehicle by detecting light emitted from the emitting device, the second vehicle can be detected more reliably. It is also preferable that the oblique sides located on the left and right of the trapezoidal emission area are slightly outside the left and right lines of the driving lane as seen from the emitting device. In this case, it is preferable that light is unlikely to be irradiated onto a reflector located outside the left and right lines of the driving lane as seen from the emission device. It is also preferable that the left and right oblique sides of the trapezoidal emission area are located at the same positions as the left and right lines of the driving lane as seen from the emission device. It is even more preferable that the left and right oblique sides of the trapezoidal emission area are located inside the left and right lines of the driving lane as seen from the emission device. It is also preferable that the emission area is adapted to roads that are relatively wide in the left-right direction, such as arterial roads. Since automobile speeds tend to be high on roads that are wide in the left-right direction, the distance to a second vehicle becomes important in terms of driving safety. Using an emission device on roads where speeds tend to be high improves driving safety.

[0014] (3) In the emission region of the emission device, the luminance of the light in the first portion may be greater than the luminance of the light in the second portion. In this case, the light can reach a farther distance than when the luminance of the light in the first portion is equal to or less than the luminance of the light in the second portion. Since the luminance of the first portion for detecting a second vehicle located farther away is greater and the light can reach a farther distance, when detecting a second vehicle by detecting the light emitted from the emission device, a second vehicle located farther away can be detected.

[0015] (4) The emitting device may include a light receiving unit that receives reflected light of the light emitted by the emitting unit, and the upper part of the light receiving unit may have a shape that conforms to the upper part of the area where the reflected light of the emitting area is incident. In this case, the area of ​​the light receiving area of ​​the light receiving unit that can be used to receive the light emitted to the emitting area can be made larger than when the light receiving unit does not have a shape that conforms to the upper part of the light emitting area. Therefore, a wider range of light can be received. Therefore, the emitting device can further improve the detection accuracy of the second vehicle.

[0016] Note that, for example, one photodiode is used as the light receiving unit. When one photodiode is used, if the area of ​​the light receiving area of ​​the light receiving unit that can be used to receive light emitted to the emission region is small, sensitivity decreases. However, as in the present invention, the light receiving unit is shaped to fit along the upper part of the region where reflected light from the light emission region is incident, thereby increasing the area that can be used to receive light emitted to the emission region, thereby improving sensitivity even with one photodiode. Therefore, the emission device can further improve the detection accuracy of the second vehicle.

[0017] (5) In the above-described emitting device, the shape of the emitting region, when projected onto a plane normal to the emitting direction, may be a trapezoid with the first portion at the top and the second portion at the bottom, and the light receiving portion may be a rectangle with one corner located at the top. When one corner of the rectangular light receiving portion is located at the top, both sides forming the upper corner are aligned with the top of the trapezoidal emitting region where reflected light enters. Therefore, compared to when the light receiving portion is positioned so that the upper side of the rectangle is parallel to the left-right direction, the area of ​​the light receiving portion that can be used to receive reflected light of light emitted to the emitting region can be increased. This allows light to be received over a wider range. Therefore, the emitting device can further improve the detection accuracy of a second vehicle when using a rectangular light receiving portion.

[0018] (6) The emitting device includes a light-receiving lens that guides the reflected light to the light-receiving unit, and the light-receiving lens has multiple optical central axes, and the optical central axes are preferably located inside the light-receiving unit. Here, in order to widen the light-receiving area of ​​the light-receiving unit, measures such as increasing the area of ​​the light-receiving unit or shortening the focal length of the light-receiving lens are conceivable. Increasing the area of ​​the light-receiving unit increases the electrical capacitance of the light-receiving unit, making it easier for the waveform of received light to become dull. This may result in a decrease in the detection accuracy of the second vehicle. Therefore, there is a limit to how large the light-receiving unit can be. Furthermore, shortening the focal length of the light-receiving lens reduces the area of ​​the light-receiving lens, reducing the light-gathering ability of the light-receiving lens. This may result in a decrease in the detection accuracy of the second vehicle. Therefore, there is a limit to how long it can be shortened.

[0019] In the present invention, the light receiving lens has multiple optical central axes. Therefore, the light receiving area in which the light receiving unit can receive light is larger than in the case of a lens with a single optical central axis. In other words, the light receiving area can be enlarged without increasing the area of ​​the light receiving unit. Because the light receiving area is enlarged, a second vehicle located over a wider range can be detected, improving the detection accuracy of the second vehicle.

[0020] Furthermore, compared to a case where there is a single optical center axis, the light receiving area can be enlarged while preventing a decrease in light gathering ability due to a smaller light receiving lens. Because the light receiving area is enlarged, a second vehicle located over a wider area can be detected, improving the detection accuracy of the second vehicle.

[0021] (7) In the above-mentioned light-emitting device, the light-receiving lens may include a main lens and an auxiliary lens, the auxiliary lens being disposed below the main lens, and the optical center axis of the auxiliary lens being located below the optical center axis of the main lens. In this case, more downward light can be guided to the light-receiving unit than when only the main lens is provided. Therefore, the area in which the light-receiving unit can receive the downward light is larger than when only the main lens is provided.

[0022] Here, when viewed from the emission device, the farther the distance from the emission device to the second vehicle, the higher the reflector of the second vehicle is located, and the closer the distance from the emission device to the second vehicle, the lower the reflector of the second vehicle is located. In the present invention, the area that can receive light from below is increased, thereby increasing the area that can receive light in the vertical direction. Therefore, the range of distances over which the reflector of the second vehicle can be detected is wider than when only a main lens is provided. Furthermore, compared to when a single lens is used to increase the light receiving range, the lens does not become too large. Therefore, the possibility of the emission device becoming larger can be reduced. Furthermore, it is preferable that the auxiliary lens is smaller than the main lens.

[0023] (8) In the emission device, two auxiliary lenses may be arranged side by side in the left-right direction, with the optical center axis of one auxiliary lens located on one side of the optical center axis of the main lens in the left-right direction, and the optical center axis of the other auxiliary lens located on the other side of the optical center axis of the main lens in the left-right direction. In this case, the two auxiliary lenses are arranged side by side in the left-right direction below the main lens. Therefore, the light receiving range of the lower portion of the light receiving region is larger in the left-right direction compared to when a single auxiliary lens is provided. In this invention, since the second portion is located below the first portion, the left-right width of the lower portion of the emission region tends to be larger than the left-right width of the upper portion. However, by providing two auxiliary lenses, the light receiving range can be set to match the width of the lower portion of the emission region. Therefore, reflected light of light emitted to the emission region can be more reliably received, further improving the detection accuracy of the second vehicle. Furthermore, one auxiliary lens may be shaped symmetrically to the other auxiliary lens. In addition, it is preferable that the optical center axis of one auxiliary lens and the optical center axis of the other auxiliary lens are located at positions symmetrical to each other with respect to the optical center axis of the main lens.

[0024] The main lens and auxiliary lens are preferably formed integrally. In this case, light is less likely to be bent or reflected at the boundary between the main lens and auxiliary lens than when the main lens and auxiliary lens are formed separately. Therefore, light can be more reliably guided to the light receiving unit than when the main lens and auxiliary lens are formed separately. This improves the detection accuracy of the second vehicle.

[0025] (9) In the emission device, the main lens may be circular, and the auxiliary lens may have the same shape as a portion of the main lens adjacent to the auxiliary lens. In this case, the reflected light is received by the light receiving unit when the focal lengths of the main lens and the auxiliary lens are the same. Therefore, the detection accuracy of the second vehicle is improved compared to when the focal lengths of the main lens and the auxiliary lens are different.

[0026] (10) The emitting device may include a housing that supports the light receiving unit and the light receiving lens, and a reflecting unit within the housing that reflects a portion of the light incident from the light receiving lens and guides it to the light receiving unit. In this case, the brightness of the reflected light that reaches the light receiving unit is greater than when a reflecting unit is not provided. This allows the emitting device to more reliably detect a second vehicle.

[0027] (11) The emitting device may include a non-reflecting portion disposed below the light receiving portion within the housing and less likely to guide the light to the light receiving portion than the reflecting portion, and the reflecting portion may reflect the light that reaches at least above the light receiving portion and guide it to the light receiving portion. A portion of the light from the periphery of the second portion of the emitting region reaches above the light receiving portion via the main lens or auxiliary lens. The light that reaches above the light receiving portion is guided to the light receiving portion by the reflecting portion. This allows the emitting device to more reliably detect a nearby second vehicle. Meanwhile, a portion of the light from the periphery of the first portion of the emitting region reaches below the light receiving portion. Because a non-reflecting portion is provided below the light receiving portion, the light is less likely to be reflected. The lane where the light from the first portion of the emitting device is emitted is narrow in the left-right direction, and the light is likely to be irradiated onto reflectors outside the lane. However, the non-reflecting portion makes it difficult for the light to be guided to the light receiving portion, further reducing the possibility of erroneous detection of a reflector.

[0028] (12) In the above-mentioned emitting device, the light receiving portion may be rectangular with one corner located on the upper side, and the reflecting portion may extend from each of a pair of sides forming the one corner. In this case, the light reflected by the reflecting portion may more reliably reach the light receiving portion. This improves the detection accuracy of the second vehicle.

[0029] (13) In the light emitting device, the light emitting section and the light receiving lens may be disposed adjacent to each other. In this case, the light emitting area and the area received by the light receiving section are more likely to overlap than when the light emitting section and the light receiving lens are spaced apart. This improves the detection accuracy of the second vehicle.

[0030] (14) The emission device may include an emission control means for causing the emission device to emit the light and an equivalent time sampling means for sampling a signal including the light received by the light receiving device at a sampling interval based on an equivalent time sampling method, and the emission control means may change the brightness of the emitted light depending on the time between emitting the light and sampling by the equivalent time sampling means. For example, the closer the distance from the emission device to the second vehicle, the greater the brightness of the reflected light received by the light receiving device. Furthermore, depending on the characteristics of the lens on the light emitting side or the lens on the light receiving side, for example, the brightness of the reflected light received by the light receiving device may increase when the distance from the emission device to the second vehicle is within a predetermined range. If the brightness of the reflected light received by the light receiving device increases, an amplifier circuit or the like may become saturated when the voltage based on the reflected light received by the light receiving device is amplified by the amplifier circuit. As a result, it may take time for the amplifier circuit to return to a normal state after saturation, which may reduce the accuracy of detecting the second vehicle.

[0031] In the equivalent time sampling method, the time between when light is emitted from the light-emitting unit and when it is sampled varies depending on the distance to the second vehicle. In the present invention, the brightness of the emitted light varies depending on the time between when light is emitted from the light-emitting unit and when it is sampled. Therefore, for example, the brightness of the light emitted from the light-emitting unit can be reduced within a range where the amplifier circuit may become saturated. This reduces the possibility of the amplifier circuit becoming saturated. Even if the amplifier circuit becomes saturated, the recovery time from saturation can be shortened. This improves the detection accuracy of the second vehicle. Furthermore, power consumption is reduced compared to when the brightness of the light does not change and light is always emitted at a brightness sufficient to detect a distant second vehicle. Furthermore, the equivalent time sampling method provides periods when light is not emitted, preventing strong light from being continuously output.

[0032] However, since the frequency of light pulses is high (for example, the unit of pulse frequency is nanoseconds), a very high sampling frequency is required, which can lead to problems such as expensive components. Therefore, in the present invention, sampling is performed using an equivalent sampling method.

[0033] The emission device emits light with the intensity necessary to reach the farthest position within the range of distance for detecting the second vehicle. Therefore, the light intensity may be strong. Furthermore, for example, if the emission device is installed inside a vehicle, the light intensity may be even stronger because it must pass through the windshield or other similar structure. Continuously emitting high-intensity light requires consideration of its effects on human eyes, etc. Therefore, instead of continuously emitting light, pulsed light is emitted, and periods of time during which no light is emitted are provided, thereby reducing the average light intensity. This reduces the effects on human eyes, etc. For example, the interval between pulses may be set twice as long as the pulse width. More preferably, the interval between pulses may be set 1,000 times or more longer than the pulse width.

[0034] (15) In the emission device, the emission control means may cause the emission unit to emit light with lower brightness the shorter the time between emitting the light and sampling by the equivalent time sampling means. The closer the distance from the emission device to the second vehicle, the greater the brightness of the light received by the light receiving unit. In this invention, the shorter the time between emitting light and sampling by the equivalent time sampling means, the lower the brightness of the light emitted from the light emitting unit. Therefore, compared to when the brightness of the light is not adjusted, the brightness of the light received when the distance from the emission device to the second vehicle is short can be reduced. This reduces the possibility of saturating the amplifier circuit, improving the accuracy of detecting the second vehicle.

[0035] (16) In the emission device, the emission control means may include a power supply circuit that supplies a voltage to the emission unit, the power supply circuit including a DC / DC converter, a first resistor connected to the output side of the DC / DC converter, and a second resistor connected to ground, the power supply circuit including a divided voltage input to a reference input terminal of the DC / DC converter and a dividing resistor used to set the output voltage of the DC / DC converter, an integrating circuit to which a pulse signal is input, and a third resistor provided between the output side of the integrating circuit and the reference input terminal, wherein the pulse signal input to the integrating circuit fluctuates the voltage applied to the reference input terminal and fluctuates the output voltage of the DC / DC converter, thereby causing the emission unit to emit light with lower luminance as the time between emission of the light and sampling by the equivalent time sampling means becomes shorter. In this case, by fluctuating the voltage input to the reference input terminal using the output from the integrating circuit, it is possible to realize a function of causing the light emission unit to emit light with lower luminance as the time between emission of light and sampling by the equivalent time sampling means becomes shorter.

[0036] (17) In the emission device, the equivalent time sampling means may include a first acquisition means for acquiring a signal received by the light receiving unit before the light is emitted by the emission unit, a second acquisition means for acquiring a signal received by the light receiving unit at the sampling interval using the equivalent time sampling method after the light is emitted by the emission unit, a third acquisition means for acquiring a signal based on the difference between the signal acquired by the first acquisition means and the signal acquired by the second acquisition means, and an encoding means for encoding the signal acquired by the third acquisition means.

[0037] The signal acquired by the light receiving unit may contain various types of noise, such as circuit noise, external electrical noise, and external optical noise. Because the signal level of reflected light is very small, if the S / N ratio decreases due to the effects of noise, this can cause a decrease in sensitivity and shorten the distance at which a second vehicle can be detected. One way to improve the S / N ratio is to use a bandpass filter (BPF), but because the signal waveform of reflected light is a square wave, narrowing the bandwidth of the BPF can distort the waveform of the reflected light signal. This can cause a decrease in sensitivity and shorten the distance at which a second vehicle can be detected.

[0038] In the present invention, a signal based on the difference between a signal acquired before light is emitted and a signal acquired at sampling intervals using an equivalent sampling method is acquired and encoded. The signal acquired by the first acquisition means is a signal that does not contain reflected light and is a noise signal. The signal acquired by the second acquisition means is a signal that contains reflected light and noise. A signal based on the difference between the signal containing reflected light and noise and the noise signal is acquired and encoded, thereby improving the S / N ratio. Furthermore, because a BPF is not used, the waveform of the reflected light is less likely to be distorted. This reduces the possibility of sensitivity degradation and increases the distance at which a second vehicle can be detected.

[0039] (18) The emission device may include a low-pass filter that passes a frequency band lower than that of the light received by the light-receiving unit, and the first acquisition means may acquire the signal after passing through the low-pass filter. When the first acquisition means acquires a signal containing noise in the same frequency band as the light emitted by the light-emitting unit, there is a possibility that noise fluctuating in the same frequency band as the light may be superimposed on the optical signal by the third acquisition means. In this invention, the low-pass filter reduces noise in the same frequency band as the light, and the signal is acquired by the first acquisition means. Therefore, the third acquisition means reduces the possibility that noise fluctuating in the same frequency band as the light may be superimposed on the optical signal. This reduces the possibility of sensitivity degradation and increases the distance at which a second vehicle can be detected.

[0040] (19) The emission device may include a distance acquisition unit that acquires the distance to the object based on the signal received from the light receiving unit. In this case, the emission device may acquire the inter-vehicle distance to the second vehicle. [Brief explanation of the drawings]

[0041] [Figure 1] 1 is a view of the front of the vehicle 2 seen from inside the vehicle. [Figure 2] 2 is a block diagram showing the electrical configuration of the laser inter-vehicle distance meter 1. FIG. [Figure 3] FIG. [Figure 4] FIG. 2 is a plan view of the optical unit 7. [Figure 5] 10 is a diagram showing the shape of an emission area 40 when viewed from the laser inter-vehicle distance meter 1. FIG. [Figure 6] 6 is a diagram showing a case where another vehicle 3 is located closer than the position shown in FIG. 5. [Figure 7] 10 is a diagram showing the brightness etc. of the emission area 40. FIG. [Figure 8] FIG. 10 is a front view of the optical unit 7 with the light projecting lens 711 and the light receiving lens 76 removed. [Figure 9] FIG. 2 is a front view of the optical unit 7. [Figure 10] FIG. 2 is a vertical cross-sectional view of a light receiving unit 74 in the optical unit 7. [Figure 11] 1 is a diagram for explaining a method for measuring the distance between another vehicle 3 and a laser inter-vehicle distance meter 1. FIG. [Figure 12] FIG. 10 is another diagram for explaining the method of measuring the distance between another vehicle 3 and the laser inter-vehicle distance meter 1. [Figure 13] FIG. 2 is a block diagram showing an emission control circuit 60. [Figure 14] FIG. 2 is a block diagram showing a light-receiving control circuit 80. [Figure 15] 15 is a diagram illustrating an example of light reception control by a light reception control circuit 80 shown in FIG. 14. FIG. [Figure 16] FIG. 10 is a block diagram of a pulse generating circuit 85. [Figure 17] FIG. 10 is a diagram showing an emission region 41 according to a modified example. [Figure 18] 1 is an external view of a laser inter-vehicle distance meter 1. FIG. [Figure 19] FIG. 9 is a diagram showing a table 961. [Figure 20] FIG. 9 is a diagram showing a table 962. [Figure 21] FIG. 9 is a diagram showing a table 963. [Figure 22] FIG. 9 is a diagram showing a table 964. DETAILED DESCRIPTION OF THE INVENTION

[0042] A laser inter-vehicle distance meter 1, which is an example of the present invention, will be described below with reference to the drawings. In the following description, the upper, lower, right, left, front, and back sides of the paper in Fig. 1 will be referred to as the upper, lower, right, left, rear, and front sides of the laser inter-vehicle distance meter 1 and the vehicle 2, respectively.

[0043] An overview of the laser inter-vehicle distance meter 1 will be described with reference to Figures 1 and 2. The laser inter-vehicle distance meter 1 is mounted on the host vehicle 2 and emits light in an emission direction that is in front of or behind the host vehicle 2. In this embodiment, the emission direction of the light is the front of the laser inter-vehicle distance meter 1. The laser inter-vehicle distance meter 1 receives reflected light from a reflector 31 (see Figures 5 and 6) of another vehicle 3 (see Figures 5 and 6) located in the emission direction, and measures the distance to the other vehicle 3 and the distance between the laser inter-vehicle distance meter 1 and the other vehicle 3. In this embodiment, the reflector 31 of the other vehicle 3 is provided at a lower part of the rear surface 32 of the other vehicle 3, spaced apart in the left-right direction (see Figures 5 and 6).

[0044] 1 shows a view of the front from inside the vehicle 2. In FIG. 1, a rearview mirror 29 is indicated by a dotted line. The laser inter-vehicle distance meter 1 is disposed in front of the rearview mirror 29.

[0045] As shown in FIG. 1 , the laser inter-vehicle distance meter 1 includes a main body 11 and a mounting unit 19. The mounting unit 19 includes an attachment unit 191 and a support unit 192. The main body 11 is substantially rectangular parallelepiped-shaped. The support unit 192 extends upward from the top of the main body 11. The mounting unit 191 is provided at the upper end of the support unit 192. The mounting unit 191 is a substantially rectangular plate, and is attached to the center and upper part of the windshield 91 in the left-right direction, for example, with double-sided adhesive tape or a suction cup. This allows the laser inter-vehicle distance meter 1 to be mounted on the windshield 91. The mounting unit 19 supports the main body 11 so that its angle can be changed. Therefore, the laser inter-vehicle distance meter 1 can be mounted on the host vehicle 2 so that the emission direction is horizontal. The laser distance meter 1 may be installed in another location, for example, on the back of the rearview mirror 29 by providing a mounting part for mounting on the back of the rearview mirror 29, but it is preferable to install it on the windshield 91 as in this embodiment. In this way, it is possible to prevent the relative distance between the laser distance meter 1 and the windshield 91 from changing due to vehicle vibration, and the measurement accuracy of the laser distance meter 1 can be improved compared to other installation locations.

[0046] As shown in FIG. 2, the main body 11 of the laser inter-vehicle distance meter 1 includes a CPU 101, a light emitting circuit 102, a light receiving circuit 103, an audio circuit 104, a speaker 105, a ROM 106, a RAM 107, and an optical unit 7. The optical unit 7 includes an emission unit 71 and a light receiving unit 74. The emission unit 71 includes an LD (Laser Diode) 72. The emission unit 71 is capable of emitting light. The light receiving unit 74 includes a photodiode 75. The light receiving unit 74 is capable of receiving light that is irradiated from the emission unit 71 and reflected by a reflector 31 or the like. The light emitted and received by the optical unit 7 passes through a transparent plate (not shown) provided on the front surface of the main body 11 and the windshield 91.

[0047] The CPU 101 is electrically connected to a light emitting circuit 102, a light receiving circuit 103, an audio circuit 104, a ROM 106, and a RAM 107. The ROM 106 stores a program for the CPU 101 to control the laser inter-vehicle distance meter 1. The RAM 107 temporarily stores various data.

[0048] The light-emitting circuit 102 is electrically connected to the LD 72. The CPU 101 controls the turning on and off of the LD 72 via the light-emitting circuit 102. The light-receiving circuit 103 is electrically connected to the photodiode 75. The light-receiving circuit 103 transmits a signal based on the light received by the photodiode 75 to the CPU 101. The CPU 101 measures the distance between the other vehicle 3 and the laser vehicle-to-vehicle distance meter 1 based on the transmitted signal.

[0049] The audio circuit 104 is electrically connected to a speaker 105. The CPU 101 controls the audio circuit 104 to output audio from the speaker 105. For example, the CPU 101 outputs audio from the speaker 105 when the distance between the other vehicle 3 and the laser distance meter 1 becomes equal to or shorter than a predetermined distance. This causes the CPU 101 to notify the driver of the host vehicle 2 that the distance between the other vehicle 3 and the laser distance meter 1 has become equal to or shorter than the predetermined distance. Furthermore, for example, the CPU 101 outputs audio from the speaker 105 when the distance between the laser distance meter 1 and the other vehicle 3 becomes shorter by a predetermined distance (e.g., 10 m) or more within a predetermined time (e.g., 0.3 seconds). This causes the CPU 101 to notify the driver of the host vehicle 2 that the other vehicle 3 is approaching.

[0050] The schematic configuration of the optical unit 7 will be described with reference to Figures 3 and 4. As shown in Figures 3 and 4, in the optical unit 7, an emission unit 71 and a light receiving unit 74 are integrally formed. The emission unit 71 and the light receiving unit 74 are adjacent to each other. Therefore, a light receiving lens 76 provided on the front surface of the light receiving unit 74 is adjacent to the emission unit 71. The light receiving unit 74 is provided to the right of the emission unit 71.

[0051] The light emitting unit 71 and the light receiving unit 74 are box-shaped. The light receiving unit 74 protrudes forward more than the light emitting unit 71. The light receiving unit 74 also protrudes upward more than the light emitting unit 71.

[0052] 5 to 7, the following describes the emission region 40, which is the region from which the emission unit 71 emits light. The emission unit 71 has directional characteristics that concentrate and emit light in the emission region 40. The shape of the emission region 40 shown in FIGS. 5 to 7 is a trapezoidal shape projected onto a plane having the emission direction as its normal line.

[0053] The emission unit 71 includes an LD 72 (see FIGS. 2 and 8) and a projection lens 711 (see FIG. 3). The emission unit 71 can refract light generated by the LD 72 using the projection lens 711, thereby concentrating the light on the emission region 40. That is, the emission unit 71 of this embodiment has a trapezoidal directivity due to the projection lens 711.

[0054] In the following description, the lane in which the host vehicle 2 is traveling is referred to as the driving lane 50. As shown in FIG. 5, when viewed in the emission direction from the laser inter-vehicle distance meter 1 disposed on the host vehicle 2, the straight driving lane 50 has a width that narrows in the left-right direction as it goes up. The right-side line 501 defining the driving lane 50 inclines more to the left as it goes up, and the left-side line 502 inclines more to the right as it goes up. The upper end 503 of the driving lane 50 is a plane that is parallel to the left-right direction. In this way, the driving lane 50 has a substantially trapezoidal shape. Therefore, when the other vehicle 3 is in a distant position, the other vehicle 3 is located at the top (see FIG. 5) and has a narrow width in the left-right direction. When the other vehicle 3 is located closer than the distant position, the other vehicle 3 is located at the bottom and has a wider width in the left-right direction (see FIG. 6).

[0055] The reflector 95 is disposed on the outer side in the left-right direction of the driving lane 50. The outer side in the left-right direction of the driving lane 50 includes the left-right ends and the outside of the driving lane 50. The left-right ends of the driving lane 50 include lines 501 and 502. In this embodiment, as an example, the reflector 95 is disposed on the line 501 and the line 502. The reflector 95 may also be disposed to the right of the line 501 and to the left of the line 502 in the driving lane 50. For example, the reflector 95 may also be disposed on a sidewalk curb.

[0056] In the emission region 40, a portion corresponding to a distant position is referred to as a first portion 401. In this embodiment, the first portion 401 is an upper portion of the emission region 40, and is a portion for detecting another vehicle 3 when the other vehicle 3 is in a distant position. In addition, in the emission region 40, a portion below the first portion 401 is referred to as a second portion 402. The second portion 402 is a portion for detecting another vehicle 3 when the other vehicle 3 is in a close position. The first portion 401 has a smaller width in the left-right direction than the second portion 402. In this embodiment, the second portion 402 is a lower portion of the emission region 40.

[0057] In the emission area 40, the width in the left-right direction of the first portion 401 for detecting another vehicle 3 at a distant location is smaller than the width in the left-right direction of the second portion 402 for detecting another vehicle 3 that is closer than the distant location. The second portion 402 is located below the first portion 401. In this manner, the emission area 40 is set to match the size of the other vehicle 3 and the width in the left-right direction of the driving lane 50. Therefore, when the emission area 40 is aligned with the straight driving lane 50, the amount of light from the emission area 40 that is irradiated onto the reflectors 95 outside the driving lane 50 is reduced. Therefore, when detecting another vehicle 3 by detecting the light emitted from the laser inter-vehicle distance meter 1, the possibility of erroneously detecting the reflectors 95 outside the left-right direction of the driving lane 50 is reduced. This improves the detection accuracy of the other vehicle 3.

[0058] Furthermore, in this embodiment, the shape of output region 40 when projected onto a plane normal to the output direction is a trapezoid with first portion 401 at the top and second portion 402 at the bottom. Right oblique side 403 of output region 40 inclines more to the left as it moves upward, and left oblique side 404 inclines more to the right as it moves upward. Oblique side 403 is aligned with right line 501 of driving lane 50, and oblique side 404 is aligned with left line 502 of driving lane 50.

[0059] 7, the magnitude of the luminance in the emission region 40 is indicated by the shade of color. In the emission region 40, the luminance of light in the first portion 401 is greater than the luminance of light in the second portion 402. In this embodiment, the luminance gradually increases from the second portion 402 toward the first portion 401.

[0060] When the driving lane 50 is viewed from the laser inter-vehicle distance meter 1 installed on the host vehicle 2, the driving lane 50 is trapezoidal. For this reason, as shown in FIGS. 5 and 6 , the reflector 31 installed on the other vehicle 3 is often located within the trapezoidal area where light is concentrated. Therefore, compared to when the emission area 40 has a shape other than a trapezoid, the brightness of the light irradiated onto the reflector 95 outside the driving lane 50 is likely to be lower, and the brightness of the light irradiated onto the reflector 31 of the other vehicle 3 is likely to be higher. Therefore, when detecting the other vehicle 3 by detecting the light emitted from the laser inter-vehicle distance meter 1, the other vehicle 3 can be detected more reliably. Furthermore, because the light is less likely to hit a reflector installed in an unnecessary area, such as a roadside strip, false detection of the reflector can be prevented, and the detection distance of the other vehicle 3 can be increased.

[0061] Furthermore, as shown in FIG. 7 , in the emission region 40, the luminance of light from the first portion 401 is greater than the luminance of light from the second portion 402, so that the light can reach a greater distance than when the luminance of light from the first portion 401 is equal to or less than the luminance of light from the second portion 402. When another vehicle 3 is located in the first portion 401, it is located farther away than when it is located in the second portion 402 (see FIG. 5 ). Since the luminance of the first portion 401 for detecting another vehicle 3 located farther away is greater and the light can reach a greater distance, when another vehicle 3 is detected by detecting the light emitted from the laser inter-vehicle distance meter 1, it is possible to detect another vehicle 3 that is farther away. That is, in this embodiment, the light is concentrated and strongly irradiated in a distant direction where sensitivity is required, so that the detection distance of the other vehicle 3 can be efficiently increased. Therefore, the detection distance of the other vehicle 3 can be increased.

[0062] The structure of the emission unit 71 will be described with reference to FIGS. 3, 4, 8, and 9. The emission unit 71 includes a housing 712, an LD 72 (see FIGS. 2 and 8), and a projection lens 711. The housing 712 is substantially rectangular. As shown in FIG. 8, the housing 712 is provided with a recess 713 that is recessed from the front to the rear. The LD 72 is disposed at the rear end of the recess 713. The projection lens 711 is attached to the front of the housing 712 (see FIG. 9). The LD 72 emits light, and the light is refracted by the projection lens 711, so that the light is emitted to the emission region 40 (see FIGS. 5 to 7). That is, the curved surface of the projection lens 711 realizes trapezoidal directional characteristics and can further increase the brightness of the light in the upper part of the trapezoid.

[0063] The structure of the light receiving unit 74 will be described with reference to Figures 3, 4, 8, and 9. The light receiving unit 74 includes a housing 742, a photodiode 75 (see Figures 2 and 8), and a light receiving lens 76. The housing 742 is substantially rectangular and larger than the housing 712. As shown in Figure 8, the housing 742 is provided with a recess 743 that is recessed from the front to the rear. The photodiode 75 is disposed at the rear end of the recess 743. The photodiode 75 is supported by the housing 742.

[0064] 3, 4, and 9, the light-receiving lens 76 is attached to the front surface of the housing 742. That is, the light-receiving lens 76 is supported by the housing 742 in front of the photodiode 75. The light-receiving lens 76 guides reflected light that is the light emitted by the emission unit 71 to the photodiode 75.

[0065] The photodiode 75 receives reflected light that is the light emitted by the emission unit 71. As shown in FIG. 7, an incident region 750 onto which the reflected light of the trapezoidal emission region 40 is incident tends to be trapezoidal in shape, similar to the emission region 40. In FIG. 7, the emission region 40 and the incident region 750 are shown overlapping each other. As shown in FIG. 8, the upper part of the photodiode 75 has a shape that conforms to the upper part of the incident region 750 onto which the reflected light of the emission region 40 (see FIGS. 5 and 7) is incident. More specifically, the photodiode 75 is quadrangular, with one corner 751 located on the upper side. Sides 752 and 753 that form the one corner 751 are inclined so as to conform to the upper part of the incident region 750 onto which the reflected light of the emission region 40 is incident. In this embodiment, the photodiode 75, which is a square light receiving element, is rotated 45 degrees.

[0066] 9, light receiving lens 76 has a plurality of (three in this embodiment, for example) optical center axes 911 to 913. All of the plurality of optical center axes 911 to 913 are located inside photodiode 75. The structure of light receiving lens 76 will be described in detail below.

[0067] As shown in FIGS. 3 and 9, the light receiving lens 76 includes a main lens 761 and two auxiliary lenses 762 and 763. The main lens 761 and the auxiliary lenses 762 and 763 are integrally formed. The main lens 761 is a circular lens when viewed from the front. A front surface 7611 of the main lens 761 protrudes forward so as to form a portion of a sphere. The two auxiliary lenses 762 and 763 are provided side by side in the left-right direction below the main lens 761. The auxiliary lenses 762 and 763 are smaller than the main lens 761. One auxiliary lens 762 has a shape that is symmetrical to the other auxiliary lens.

[0068] In this embodiment, in addition to the main lens 761, which is a normal circular spherical lens, auxiliary lenses 762 and 763, which are spherical lenses with the same curvature as the main lens 761, are arranged to the lower right and lower left of the main lens 761. The auxiliary lenses 762 and 763 have the same shape as the portions of the main lens 761 adjacent to the auxiliary lenses 762 and 763. Note that the term "same shape" does not necessarily mean an exact identical shape, but also includes a shape similar to the portions of the main lens 761 adjacent to the auxiliary lenses 762 and 763.

[0069] In this embodiment, the auxiliary lens 762 is connected to the lower right portion of the main lens 761 and has the same shape as the lower right portion of the main lens 761. An upper surface 762B of the auxiliary lens 762 protrudes forward from the lower right end of the main lens 761. In a front view, the upper surface 762B has an arc shape that follows the lower right end of the main lens 761. In a front view, the lower end 762C of the auxiliary lens 762 also has an arc shape. A front surface 762A of the auxiliary lens 762 is curved so that it is positioned further rearward from the upper surface 762B toward the lower end 762C.

[0070] The auxiliary lens 763 is connected to the lower left part of the main lens 761 and has the same shape as the lower left part of the main lens 761. An upper surface 763B of the auxiliary lens 763 protrudes forward from the lower left end of the main lens 761. In a front view, the upper surface 763B is arc-shaped along the lower left end of the main lens 761. A lower end 763C of the auxiliary lens 763 is also arc-shaped in a front view. A front surface 763A of the auxiliary lens 763 is curved so that it is positioned further rearward from the upper surface 763B toward the lower end 763C.

[0071] 9, optical center axes 912 and 913 of the auxiliary lenses 762 and 763 are located below the optical center axis 911 of the main lens 761. Furthermore, the optical center axis 912 of one of the auxiliary lenses 762 and 763 is located on the right side, that is, on one side in the left-right direction, of the optical center axis 911 of the main lens 761. The optical center axis 913 of the other auxiliary lens 763 is located on the left side, that is, on the other side in the left-right direction, of the optical center axis 911 of the main lens 761. The optical center axes 912 and 913 are located in symmetrical positions with respect to the left-right position of the optical center axis 911 of the main lens 761.

[0072] As a result of forming the auxiliary lenses 762 and 763 as described above, the light receiving region 89 capable of receiving light by the photodiode 75 is as shown in FIG. 7 . The light receiving region 89 includes light receiving regions 891 to 893. The light receiving regions 891, 892, and 893 indicate regions where the main lens 761, the auxiliary lens 762, and the auxiliary lens 763 guide reflected light from the light exit region 40 to the photodiode 75, respectively. The shape of each of the light receiving regions 891 to 893 corresponds to the shape of the photodiode 75. The light receiving region 891 of the main lens 761 corresponds to the upper part of the light exit region 40 and the incident region 750. The light receiving region 892 of the auxiliary lens 762 is located to the lower right of the light receiving region 891 of the main lens 761. The light receiving region 893 of the auxiliary lens 763 is located to the lower left of the light receiving region 891 of the main lens 761. That is, the area in which the photodiode 75 can receive light has a wider angle than when only the main lens 761 is provided.

[0073] Note that a single normal circular spherical lens and a light receiving element alone cannot cover the light receiving area 40, which is the light projection area. For example, to widen the light receiving area of ​​a single lens and light receiving element, possible measures include increasing the area of ​​the light receiving element or shortening the focal length of the light receiving lens. Increasing the area of ​​the light receiving element increases the electrical capacitance of the light receiving element, which may cause the signal waveform when light is received to become dull and reduce the response speed. This may result in a decrease in the detection accuracy of other vehicles 3. Therefore, there is a limit to how much the area of ​​the light receiving element can be increased. Furthermore, shortening the focal length of the light receiving lens reduces the area of ​​the light receiving lens, which reduces the light-gathering ability of the light receiving lens. This may result in a decrease in the detection accuracy of other vehicles 3. Therefore, there is a limit to how much the focal length of the light receiving lens can be shortened. In other words, the area of ​​the light receiving element is limited by the size range of commercially available photodiodes, and there is a trade-off between the area size and the response speed. Furthermore, shortening the focal length reduces the lens diameter (lens area) of the light-receiving lens, which reduces the light-gathering ability.

[0074] In this embodiment, the light receiving lens 76 has a plurality of optical central axes 911 to 913. Therefore, compared to a lens having one optical central axis, the light receiving area 89 in which the photodiode 75 can receive light is larger (see FIG. 7). In other words, the light receiving area 89 can be enlarged without increasing the area of ​​the photodiode 75. Because the light receiving area 89 is enlarged, other vehicles 3 located over a wider range can be detected, improving the detection accuracy of other vehicles 3.

[0075] Furthermore, compared to a case where there is one optical central axis, it is possible to enlarge the light receiving area 89 while preventing a decrease in light gathering ability due to a smaller light receiving lens 76. Since the light receiving area 89 is enlarged, other vehicles 3 located over a wider range can be detected, and the detection accuracy of other vehicles 3 is improved.

[0076] Furthermore, because the optical center axes 912, 913 of the auxiliary lenses 762, 763 are located below the optical center axis 911 of the main lens 761, more downward light can be guided to the photodiode 75 than when only the main lens 761 is provided. Therefore, the area in which the photodiode 75 can receive downward light can be made larger than when only the main lens 761 is provided.

[0077] Here, when viewed from the laser inter-vehicle distance meter 1, the farther the distance from the laser inter-vehicle distance meter 1 to the other vehicle 3, the higher the reflector 31 of the other vehicle 3 is located (see FIG. 5), and the closer the distance from the laser inter-vehicle distance meter 1 to the other vehicle 3, the lower the reflector 31 of the other vehicle 3 is located (see FIG. 6). In this embodiment, the light receiving area 89 that can receive light from below is larger, and therefore the light receiving area 89 that can receive light in the vertical direction is larger. Therefore, the range of distances over which the reflector 31 of the other vehicle 3 can be detected is wider than when only the main lens 761 is provided. Also, the light receiving lens 76 does not become too large compared to when the light receiving area 89 is enlarged with a single lens. This reduces the possibility that the laser inter-vehicle distance meter 1 will become larger.

[0078] Furthermore, two auxiliary lenses 762, 763 are provided side by side in the left-right direction below the main lens 761. Therefore, compared to when one auxiliary lens is provided, the lower light receiving area 89 in the light receiving area 89 is larger in the left-right direction (see light receiving areas 892, 893). In this embodiment, the second portion 402 in the emission area 40 is located below the first portion 401, so the width of the lower portion of the emission area 40 in the left-right direction tends to be larger than the width of the upper portion in the left-right direction. However, by providing two auxiliary lenses 762, 763 lined up side by side, the light receiving area 89 can be set to match the width of the lower portion of the emission area 40. Therefore, reflected light of light emitted to the emission area 40 can be received more reliably, further improving the detection accuracy of other vehicles 3.

[0079] Furthermore, since the auxiliary lenses 762, 763 have substantially the same shape as the portions of the main lens 761 adjacent to the auxiliary lenses 762, 763, the reflected light is received by the photodiode 75 with the main lens 761 and the auxiliary lenses 762, 763 having substantially the same focal length. Therefore, the detection accuracy of the other vehicle 3 is improved compared to when the main lens 761 and the auxiliary lenses 762, 763 have different focal lengths.

[0080] The upper part of the photodiode 75 has a shape that follows the upper part of the entrance area 750 into which reflected light from the exit area 40 (see FIGS. 5 and 7) enters. Therefore, compared to a case in which the photodiode 75 does not have a shape that follows the upper part of the exit area 40, the area of ​​the photodiode 75 that can be used to receive reflected light of light emitted to the exit area 40 can be made larger. This makes it possible to receive light from a wider range. Therefore, the laser inter-vehicle distance meter 1 can further improve the detection accuracy of other vehicles 3. For example, most of the light receiving area 891 shown in FIG. 7 overlaps with the entrance area 750.

[0081] When one photodiode 75 is used, if the area of ​​the light receiving area of ​​the photodiode 75 that can be used to receive reflected light of light emitted to the emission area 40 is small, the sensitivity decreases. However, as in this embodiment, the photodiode 75 is shaped to fit along the upper part of the incidence area 750, which increases the area that can be used to receive light emitted to the emission area 40. This makes it possible to receive light over a wider range. This improves the sensitivity of the photodiode 75. Therefore, the laser inter-vehicle distance meter 1 can further improve the detection accuracy of other vehicles 3.

[0082] Furthermore, in this embodiment, the photodiode 75 is rectangular, with one corner 751 located on the upper side. When the first corner 751 of the rectangular photodiode 75 is located on the upper side, both of the two sides 752, 753 forming the upper corner 751 are aligned with the upper portion of the incident region 750, which receives light reflected from the trapezoidal emission region 40. Compared to when the photodiode 75 is positioned so that the upper side of the rectangle is parallel to the left-right direction, the area of ​​the light receiving area of ​​the photodiode 75 that can be used to receive reflected light of light emitted to the emission region 40 can be increased. This allows light to be received over a wider range. Therefore, the laser inter-vehicle distance meter 1 can further improve the detection accuracy of other vehicles 3 even when using a rectangular photodiode 75. Furthermore, since it is not necessary to form the photodiode 75 in a shape other than a rectangle, costs can be reduced.

[0083] The auxiliary lenses 762 and 763 are smaller in size than the main lens 761. In the portion of the incident area 750 that overlaps with the light receiving area 891 of the main lens 761, the main lens 761 is given priority over the auxiliary lenses 762 and 763 to acquire reflected light. When the other vehicle 3 is located far away (see FIG. 6), the gain is likely to be small because reflected light from the reflector 31 of the other vehicle 3 located far away is acquired. However, since the main lens 761, which is large in size, receives light, the other vehicle 3 can be detected more reliably. When the other vehicle 3 is located close (see FIG. 6), the gain is likely to be large because reflected light from the nearby other vehicle 3 is acquired. For this reason, the reflected light is acquired by the auxiliary lenses 762 and 763, which are small in size. That is, in the portion detected by the auxiliary lenses 762 and 763 added to the main lens 761 in this embodiment, the target other vehicle 3 is closer, so a large gain is not required, and therefore the auxiliary lenses 762 and 763 are made smaller in size. Furthermore, by using the light receiving lens 76 of this embodiment, it is possible to collect light at a wide angle without reducing the lens diameter, which is proportional to the light collecting area.

[0084] The internal structure of the housing 742 of the light receiving unit 74 will be described with reference to Fig. 8. In this embodiment, a reflective structure is provided on the rear side of the light receiving lens 76 to reflect light to the photodiode 75. This will be described in detail below. In the housing 742 of the light receiving unit 74, a recess 743 recessed toward the rear is formed by an inner wall 77. The inner wall 77 is formed by two reflective surfaces 771, 772 and five non-reflective surfaces 773 to 777.

[0085] As an example, the reflecting surfaces 771 and 772 are formed by polishing the inner wall 77 of the housing 742. The reflecting surfaces 771 and 772 reflect a portion of the light incident from the light receiving lens 76 inside the housing 742 and guide the light to the photodiode 75. In this embodiment, the reflecting surfaces 771 and 772 reflect at least the light that has reached a position above the photodiode 75 and guide the light to the photodiode 75.

[0086] The non-reflecting surfaces 773 to 777 are portions that are more difficult to guide light to the photodiode 75 than the reflecting surfaces 771 and 772. Of the non-reflecting surfaces 773 to 777, the non-reflecting surfaces 774 to 777 are provided below the photodiode 75 within the housing 742.

[0087] A hole 78 having a square shape when viewed from the front is provided in the rear and central part of the inner wall 77 for arranging the photodiode 75. The photodiode 75 is square, with one corner 751 located on the upper side. In accordance with the arrangement of the photodiode 75, the hole 78 is formed so that one corner 781 is located on the upper side.

[0088] The reflective surfaces 771 and 772 extend from a pair of sides 752 and 753 that form the upper corner 751 of the photodiode 75. The reflective surface 771 extends forward and diagonally upward to the left from the side 752. The reflective surface 772 extends forward and diagonally upward to the right from the side 753. A non-reflecting surface 773 is provided between the reflective surfaces 771 and 772.

[0089] The non-reflecting surface 774 extends downward from a pair of sides 755, 756 that form the lower corner 754 of the photodiode 75. The non-reflecting surface 775 extends diagonally leftward from the left part of the non-reflecting surface 774. The upper end of the non-reflecting surface 775 is connected to the lower end of the reflecting surface 771. The non-reflecting surface 776 extends diagonally rightward from the right part of the non-reflecting surface 774. The upper end of the non-reflecting surface 776 is connected to the lower end of the reflecting surface 772. The non-reflecting surface 777 extends diagonally downward toward the front from the lower part of the non-reflecting surface 774. The lower ends of the non-reflecting surfaces 774, 775, 776 are connected to the non-reflecting surface 777.

[0090] As described above, the light receiving unit 74 of this embodiment is formed. With reference to Fig. 10, a manner in which reflected light is guided to the photodiode 75 in the light receiving unit 74 will be described. A portion of the reflected light corresponding to the light emitted from the emission region 40 is guided to the photodiode 75 via the main lens 761 and auxiliary lenses 762 and 763 (see arrows 791 and 792).

[0091] On the other hand, a portion of the reflected light corresponding to the second portion 402 of the emission region 40 (see FIGS. 5 to 7) is not directly guided to the photodiode 75, but reaches a position above the photodiode 75 via the main lens 761 or the auxiliary lenses 762 and 763 (see, for example, arrow 793). The reflected light that reaches a position above the photodiode 75 is reflected by the reflecting surfaces 771 and 772 and guided to the photodiode 75 (see arrow 794). Therefore, the brightness of the reflected light that reaches the photodiode 75 is higher than when the reflecting surfaces 771 and 772 are not provided. The light from the second portion 402 is reflected by the reflector 31 of the nearby vehicle 3 (see FIG. 6). The provision of the reflecting surfaces 771 and 772 increases the brightness of the light reflected by the reflector 31 of the nearby vehicle 3 when it reaches the photodiode 75. Therefore, the laser inter-vehicle distance meter 1 can more reliably detect nearby vehicles 3.

[0092] A portion of the light reflected from the periphery of first portion 401 of emission region 40 reaches a position below photodiode 75 (see arrow 795). Because non-reflecting surfaces 774 to 777 are provided below photodiode 75, light is less likely to be reflected than by reflective surfaces 771 and 772. Therefore, the reflected light is less likely to be guided to photodiode 75. The lane 50 at the position where light from first portion 401 of laser inter-vehicle distance meter 1 is emitted is narrow in the left-right direction, and the light is likely to be irradiated onto reflector 95 on the outside of lane 50. However, because non-reflecting surfaces 774 to 774 make it difficult for reflected light to be guided to photodiode 75, the possibility that laser inter-vehicle distance meter 1 will erroneously detect reflector 95 can be further reduced.

[0093] Furthermore, the reflecting surfaces 771, 772 extend from a pair of sides 752, 753 that form one corner 751 of the photodiode 75 (see FIG. 8). Therefore, compared to a case in which the reflecting surfaces 771, 772 do not extend from the sides 752, 753, light reflected by the reflector 31 of the other vehicle 3 more reliably reaches the photodiode 75. This improves the detection accuracy of the other vehicle 3.

[0094] Furthermore, compared to when the reflecting surfaces 771 and 772 are not provided, the brightness of the reflected light reaching the photodiode 75 is greater. Therefore, the laser inter-vehicle distance meter 1 can detect the other vehicle 3 more reliably.

[0095] As described above, the optical unit 7 in this embodiment is formed. The emission unit 71 can concentrate light on the emission region 40 by refracting the light using the projection lens 711. Therefore, the LD 72 does not need to have a special shape for emitting light to the emission region 40. This allows the cost of the LD 72 to be reduced.

[0096] Furthermore, the emission unit 71 and the light receiving lens 76 are disposed adjacent to each other. Therefore, the emission area 40 and the entrance area 750 where light is received by the photodiode 75 are more likely to overlap than when the emission unit 71 and the light receiving lens 76 are spaced apart. This improves the detection accuracy of the other vehicle 3.

[0097] Furthermore, by forming the optical unit 7 as described above, it is possible to obtain a light receiving directivity that matches the light projecting directivity.

[0098] Furthermore, the light receiving unit 74 and the light emitting unit 71 are adjacent to each other in the left-right direction. This allows the vertical length of the optical unit 7 to be shorter than when they are adjacent to each other in the vertical direction. Therefore, when the laser inter-vehicle distance meter 1 is attached to the top of the windshield 91 as shown in FIG. 1, it is less likely to be in the driver's field of view.

[0099] The equivalent sampling method in this embodiment will be described with reference to Figures 11 and 12. In this embodiment, the laser inter-vehicle distance meter 1 uses the equivalent time sampling method (sequential sampling) when calculating the distance from the laser inter-vehicle distance meter 1 to another vehicle 3. The equivalent time sampling method is used to time-scale and process the ultra-high-speed received light pulse waveform (repeated waveform) to an order that can be captured by a low-rate AD converter. The equivalent time sampling method is a technique in which the sampling start point is shifted little by little and repeated sampling is performed, resulting in many sample points being placed on the waveform and down-converted.

[0100] The CPU 101 turns on the LD 72, causing the emission unit 71 to emit light. The CPU 101 also samples a signal based on the light received by the LD 72 at sampling intervals using the equivalent time sampling method. Note that because the frequency of light is high, a very high sampling frequency is required, which may result in problems such as expensive components. Therefore, in this embodiment, sampling is performed using the equivalent sampling method.

[0101] The closer the distance from the laser inter-vehicle distance meter 1 to the other vehicle 3, the shorter the time it takes for light to be emitted from the emission unit 71 and for the light reflected by the reflector 31 of the other vehicle 3 to reach the laser inter-vehicle distance meter 1. In other words, the time it takes for light to be emitted from the emission unit 71 and for the light reflected by the reflector 31 of the other vehicle 3 to reach the laser inter-vehicle distance meter 1 changes depending on the distance between the laser inter-vehicle distance meter 1 and the other vehicle 3. Therefore, the CPU 101 controls the emission unit 71 to change the time from emitting light to sampling, thereby detecting other vehicles 3 that are close to each other as well as those that are far away.

[0102] In this embodiment, the CPU 101 changes the brightness of the emitted light depending on the time from when the CPU 101 controls the emitting unit 71 to emit light to when sampling is performed. More specifically, in this embodiment, as shown in Fig. 12, the CPU 101 causes the emitting unit 71 to emit light with lower brightness the shorter the time from when the CPU 101 controls the emitting unit 71 to emit light to when sampling is performed. In one measurement (one set), the received light signal is sampled by sweeping the monitoring distance range of the other vehicle 3 using equivalent time sampling, and therefore the closer the distance, the higher the received light signal level at that sampling timing. Therefore, the pulsed light level of the LD 72 is controlled in proportion to the distance.

[0103] 11 and 12 will be described. In the following description, the pulsed light emitted from the laser inter-vehicle distance meter 1 may be referred to as pulsed light. FIGS. 11(A) and 11(B) show the luminance of the pulsed light emitted from the laser inter-vehicle distance meter 1 and the luminance of the reflected light when the luminance is constant regardless of the time from when the emitting unit 71 is controlled to emit light to when sampling is performed. FIGS. 12(A) and 12(B) show the luminance of the pulsed light and the luminance of the reflected light when the luminance of the emitted light is changed depending on the time from when the emitting unit 71 is controlled to emit light to when sampling is performed.

[0104] The vertical axis in FIGS. 11A and 12A represents the brightness of the light emitted by the emission unit 71, and the horizontal axis represents the distance L to the other vehicle 3 that the laser inter-vehicle distance meter 1 is attempting to detect. The vertical axis in FIGS. 11B and 12B represents the brightness of the light received by the light-receiving unit 74, and the horizontal axis represents the distance L to the other vehicle 3 that the laser inter-vehicle distance meter 1 is attempting to detect. The distance L between the laser inter-vehicle distance meter 1 and the other vehicle 3 increases as the axis moves to the right on the horizontal axis. In the following description, the pulsed light emitted by the emission unit 71 may be referred to as pulsed light Pa (a = 1 to n). The pulsed light for detecting the other vehicle 3 with the shortest distance L is referred to as pulsed light P1, and the pulsed light for detecting the other vehicle 3 with the longest distance L is referred to as pulsed light Pn. The laser inter-vehicle distance meter 1 repeatedly emits pulsed light P1 to pulsed light Pn.

[0105] The number of pulsed lights from pulsed light P1 to pulsed light Pn is, for example, 4096 (i.e., n = 4096), but in FIGS. 11 and 12 , the number of pulsed lights is shown as being smaller. The length of time for which one pulsed light is emitted is, for example, 20 to 29 nS. The time from when one pulsed light is emitted to when the next pulsed light is emitted is, for example, 57 μS. (The drawing is a conceptual diagram and shows the 57 μS interval as short, but in reality, the time is 57 μS, which is more than 1000 times longer than 20 to 29 nS.) Furthermore, the interval from when pulsed light Pa is emitted from the emitting unit 71 to when the reflected light is sampled becomes longer from pulsed light P1 to pulsed light Pn. That is, with respect to the interval from when pulsed light Pa is emitted from the emitting unit 71 to when the reflected light is sampled, the interval until sampling becomes shorter as you move to the left on the horizontal axis.

[0106] 11(A), the luminance of the pulsed light Pa emitted from the emitting unit 71 is constant regardless of the distance L (for example, it is constant at 16 W from pulsed light P1 to pulsed light Pn). For example, when the other vehicle 3 is at position PL1, the light is reflected by the reflector 31 of the other vehicle 3, and the luminance of the reflected light received by the light receiving unit 74 increases as shown at point P11. When the other vehicle 3 is at position PL2, which is farther away than position PL1, the light is reflected by the reflector 31 of the other vehicle 3, and the luminance of the reflected light received by the light receiving unit 74 increases as shown at point P12.

[0107] When another vehicle 3 is nearby, the luminance of the light reflected by the reflector 31 of the other vehicle 3 increases when it is received by the light receiving unit 74. Therefore, as shown in FIG. 11, when the luminance of the pulsed light Pa is constant, the luminance of the light at point P11 is greater than the luminance of the light at point P12.

[0108] 12, control of the luminance of pulsed light Pa when changing the luminance of the emitted light depending on the time from when the emitting unit 71 is controlled to emit pulsed light Pa until sampling is performed will be described. As shown in FIG. 12(A), the luminance of pulsed light Pa emitted from the emitting unit 71 decreases as the distance L decreases (for example, pulsed light Pn is 16 W and pulsed light P1 is 1 / 4 of that, or 4 W). That is, the CPU 101 causes the emitting unit 71 to emit pulsed light Pa with a lower luminance as the time from when the emitting unit 71 is controlled to emit light until sampling is performed decreases.

[0109] In this case, for example, when the other vehicle 3 is at position PL1, light is reflected by the reflector 31 of the other vehicle 3, and the brightness of the reflected light received by the light-receiving unit 74 increases as shown at point P21. Also, when the other vehicle 3 is at position PL2, which is farther away than position PL1, light is reflected by the reflector 31 of the other vehicle 3, and the brightness of the reflected light received by the light-receiving unit 74 increases as shown at point P22.

[0110] When another vehicle 3 is nearby, the luminance of the light reflected by the reflector 31 of the other vehicle 3 increases when received by the light receiving unit 74. However, the luminance of the pulsed light Pa emitted from the emitting unit 71 decreases as the distance L decreases, so the difference D2 between the luminance of point P21 and the luminance of point P22 becomes smaller than the difference D1 between the luminance of point P11 and the luminance of point P12 shown in FIG. 11(B).

[0111] As described above, in this embodiment, the brightness of the pulsed light Pa emitted from the emission unit 71 is controlled. The shorter the distance L from the laser inter-vehicle distance meter 1 to the other vehicle 3, the greater the brightness of the reflected light received by the light-receiving unit 74 (see FIG. 11B). Furthermore, for example, depending on the characteristics of the light-emitting projection lens 711 or the characteristics of the light-receiving lens 76, the brightness of the reflected light received by the photodiode 75 may increase when the distance L from the laser inter-vehicle distance meter 1 to the other vehicle 3 is within a predetermined range. If the brightness of the reflected light received by the photodiode 75 increases, the amplifier circuit may become saturated if the signal based on the reflected light received by the photodiode 75 is amplified by an amplifier circuit or the like. Therefore, after the amplifier circuit becomes saturated, it may take time to return to a normal state, potentially reducing the detection accuracy of the other vehicle 3. For example, the amplifier circuit may become saturated at point P11 shown in FIG. 11B.

[0112] In the equivalent time sampling method, the time from when the pulsed light Pa is emitted from the emission unit 71 until sampling by the CPU 101 varies depending on the distance to the other vehicle 3. In this embodiment, the luminance of the emitted pulsed light Pa varies depending on the time from when the pulsed light Pa is emitted from the emission unit 71 until sampling (see FIG. 12). Therefore, for example, within a range where the amplifier circuit may be saturated, the luminance of the light emitted from the emission unit 71 can be reduced. This reduces the possibility of the amplifier circuit being saturated. This improves the detection accuracy of the other vehicle 3 compared to when the amplifier circuit is saturated and a long recovery time occurs. Furthermore, even when the amplifier circuit is saturated, the recovery time can be shortened. Furthermore, power consumption is reduced compared to when the luminance of the pulsed light Pa does not change and light is always emitted at a luminance sufficient to detect a distant other vehicle 3 (see FIG. 11). Furthermore, because the luminance of each pulsed light Pa and the average optical output of the pulsed light Pa are reduced, the level of light reflected on the windshield 91 can be reduced.

[0113] The laser inter-vehicle distance meter 1 emits light with an intensity necessary to reach the farthest position within the range of distances for detecting other vehicles 3. This may result in a high light intensity. Furthermore, for example, if the laser inter-vehicle distance meter 1 is installed inside a vehicle, the light may need to pass through the windshield 91 or the like, which may further increase the light intensity. When continuously emitting high-intensity light, it is necessary to consider the effects on human eyes, etc. Therefore, in this embodiment, instead of continuously emitting light, pulsed light Pa is emitted and a period of time during which no light is emitted is provided, thereby reducing the average light intensity. This reduces the effects on human eyes, etc. For example, the interval between pulsed light Pa may be set twice as long as the pulse width. More preferably, the interval between pulsed light Pa may be set 1000 times or more long as the pulse width.

[0114] Furthermore, in this embodiment, the shorter the time between the emission of the pulsed light Pa and sampling by the CPU 101, the lower the luminance of the pulsed light Pa emitted from the emission unit 71 (see FIG. 12). Therefore, compared to when the luminance of the pulsed light Pa is not adjusted (see FIG. 11), the luminance of the reflected light received when the distance from the laser inter-vehicle distance meter 1 to the other vehicle 3 is short can be reduced (see FIG. 12). This reduces the possibility of saturating the amplifier circuit, improving the detection accuracy of the other vehicle 3.

[0115] In this way, during long-distance monitoring, when other vehicles 3 at a long distance are monitored, the pulsed light Pa is output at as high a level as possible to obtain sensitivity, and during short-distance monitoring, when other vehicles 3 at a short distance are monitored, the pulsed light Pa is output at a low level so as not to saturate the amplifier circuit at a level higher than necessary.

[0116] With reference to Fig. 13, an electrical configuration for emitting pulsed light Pa shown in Fig. 12(A) will be described. At least a part of the emission control circuit 60 shown in Fig. 13 is included in the light-emitting circuit 102 (see Fig. 2). As shown in Fig. 13, the emission control circuit 60 includes a power supply circuit 61, a fourth resistor 651, and a switch 68. The power supply circuit 61 supplies a voltage to the LD 72 of the emission unit 71. The power supply circuit 61 includes a DC / DC converter 63, a dividing resistor 62, an integrating circuit 64, and a third resistor 614. The DC / DC converter 63 is a high-voltage DC / DC voltage circuit for powering the LD 72. The DC / DC converter 63 includes an input terminal 631, an output terminal 632, a reference input terminal 633, etc.

[0117] The dividing resistor 62 includes a first resistor 621 and a second resistor 622. A terminal 621A of the first resistor 621 is electrically connected to an output terminal 632 of the DC / DC converter 63, and a terminal 621B of the first resistor 621 is electrically connected to a terminal 622A of the second resistor 622 and a reference input terminal 633 of the DC / DC converter 63. A terminal 622A of the second resistor 622 is electrically connected to the terminal 621B of the first resistor 621 and the reference input terminal 633 of the DC / DC converter 63, and a terminal 622B is electrically connected to ground. The dividing resistor 62 inputs a divided voltage to the reference input terminal 633 of the DC / DC converter 63. The dividing resistor 62 is used to set the output voltage of the DC / DC converter 63.

[0118] The integrating circuit 64 has an input terminal 641 and an output terminal 642. A terminal 614A of the third resistor 614 is electrically connected to the output terminal 642 of the integrating circuit 64. A terminal 614B of the third resistor 614 is electrically connected to the reference input terminal 633, a terminal 621B of the first resistor 621, and a terminal 622A of the second resistor 622.

[0119] An output terminal 632 of the DC / DC converter 63 is electrically connected to a terminal 651A of a fourth resistor 651. A terminal 651B of the fourth resistor 651 is electrically connected to an anode terminal 721 of the LD 72. A cathode terminal 722 of the LD 72 is connected to a switch 68 formed of a transistor or the like. The switch 68 is electrically connected to ground. The switch 68 is turned on and off under the control of the CPU 101 or by an output signal from the oscillator.

[0120] A voltage Vin is input to an input terminal 631 of a DC / DC converter 63. A pulse signal S1 is input to an input terminal 641 of an integrating circuit 64. When the pulse signal S1 is input to the integrating circuit 64, the voltage input to a reference input terminal 633 of the DC / DC converter 63 fluctuates as shown by a waveform S2. The waveform S2 is a waveform in which the voltage increases over time in a portion 611, becomes a constant voltage in a portion 662, and then decreases in a portion 663, and this change is repeated.

[0121] When the voltage of waveform S2 is input to reference input terminal 633, the voltage output from output terminal 632 of DC / DC converter 63 fluctuates as shown by waveform S3. Waveform S3 is a waveform in which the voltage rises in portion 671, becomes constant in portion 672, and then decreases over time in portion 673, repeating this cycle. That is, the voltage divided by dividing resistors 62 is forcibly varied by integrating circuit 64 and third resistor 614, thereby fluctuating the voltage applied to reference input terminal 633 and producing waveform S3. In this way, waveform S2, which is a ramp signal generated by integrating circuit 64, is input to reference input terminal 633 of DC / DC converter 63, which is a high-voltage DC / DC circuit for powering LD 72, to produce waveform S3.

[0122] The waveform S3 is applied to the LD 72. While the voltage of the portion 673 of the waveform S3 is applied to the LD 72, the switch 68 is repeatedly turned on and off, and the pulsed light Pa shown in Fig. 12(A) is output. That is, the shorter the time from when the laser inter-vehicle distance meter 1 emits the pulsed light Pa to when the equivalent time sampling means performs sampling, the weaker the brightness of the emitted light.

[0123] In this way, in this embodiment, by varying the voltage input to the reference input terminal 633 using the output from the integration circuit 64, it is possible to realize the function of causing the emission unit 71 to emit pulsed light Pa with lower brightness the shorter the time between emitting the pulsed light Pa and sampling by the CPU 101.

[0124] 14 and 15, an embodiment for improving the S / N ratio (Signal-Noise ratio) during equivalent time sampling will be described. In this embodiment, during equivalent time sampling, unnecessary components below the band of the received light signal (low frequency side) are strongly attenuated to improve the S / N. As a method for achieving this, during equivalent time sampling, the received light signal immediately before light emission is also sampled separately from the light reception timing, and subtracted by a differential amplifier 83 (described later), which is a differential circuit. This will be described in detail below.

[0125] As shown in FIG. 14, the light reception control circuit 80 includes a low-pass filter (hereinafter referred to as LPF) 81, a sample and hold circuit (hereinafter referred to as S&H) 821, an S&H 822, a differential amplifier 83, and an A / D converter 84. A light reception signal from a photodiode is input to the LPF 81 and the S&H 822. The LPF 81 is electrically connected to the S&H 82. The S&H 821 is electrically connected to the negative input terminal of the differential amplifier 83. The S&H 822 is electrically connected to the positive input terminal of the differential amplifier 83. The output terminal of the differential amplifier 83 is electrically connected to the A / D converter 84. The A / D converter 84 is electrically connected to the CPU 101.

[0126] The S&H 821 is a circuit that acquires a signal received by the photodiode 75 before the pulsed light Pa (see FIGS. 11 and 12) is emitted by the LD 72. A pre-sampling pulse is input to the S&H 821. The pre-sampling pulse is set at an interval that causes the S&H 821 to acquire a signal received by the photodiode 75 before the pulsed light Pa is emitted by the LD 72. The interval between each pulse in the pre-sampling pulse is constant. The LPF 81 passes a band of signals received by the photodiode 75 that has a lower frequency than the pulsed light Pa emitted by the LD 72. Therefore, the S&H 821 acquires the signal after passing through the LPF 81.

[0127] The S&H 822 is a circuit that acquires a signal acquired by the photodiode 75 at sampling intervals based on the equivalent sampling method after the pulsed light Pa is emitted by the LD 72. An equivalent time sampling pulse is input to the S&H 822. The equivalent time sampling pulse is set at an interval that causes the S&H 821 to acquire a signal based on the reflected light acquired by the photodiode 75 at sampling intervals based on the equivalent sampling method after the pulsed light Pa is emitted by the LD 72.

[0128] The differential amplifier 83 acquires a signal based on the difference between the signal acquired by the S&H 821 and the signal acquired by the S&H 822, and amplifies the signal level. The A / D converter 84 encodes the signal acquired by the differential amplifier 83. The encoded signal is input to the CPU 101 and used to calculate the distance L to the other vehicle 3.

[0129] Signal processing by the light-receiving control circuit 80 will be described with reference to Figure 15. Waveform 991 in Figure 15(A) represents the level of a signal based on the brightness when only reflected light from the reflector 31 of another vehicle 3 is received by the photodiode 75 when the reflector 31 of another vehicle 3 is at position PL3, with the value increasing around position PL3. Waveform 992 represents the level of a signal when various types of noise, such as circuit noise, external electrical noise, and external optical noise, are added to waveform 991. Since various types of noise are added to waveform 992, its value is larger than waveform 991 by magnitude E1.

[0130] 15(B) shows the timing at which a pre-sampling pulse PPb (b=1 to n) and an equivalent-time sampling pulse SPc (c=1 to n) are input. The S&H 821 acquires the signal acquired by the photodiode 75 at the timing at which the pre-sampling pulse PPb is input. The S&H 822 acquires the signal acquired by the photodiode 75 at the timing at which the equivalent-time sampling pulse SPc (c=1 to n) is input.

[0131] Each pre-sampling pulse PPb is input to the S&H 821 before the pulsed light Pa (a=1 to n) shown in Fig. 11 and Fig. 12 is emitted. For example, the first pre-sampling pulse PP1 is input to the S&H 821 before the pulsed light P1 (see Fig. 11 and Fig. 12) is emitted. The second pre-sampling pulse PP2 is input to the S&H 821 after the pulsed light P1 is emitted and before the pulsed light P2 (see Fig. 11 and Fig. 12) is emitted.

[0132] 11 and 12 is emitted, the reflected light of the pulsed light Pa is not received by the photodiode 75. Therefore, a signal of magnitude E1 is acquired by the S&H 821. That is, signals based on various noises such as circuit noise, external electrical noise, and external optical noise are acquired. Note that, since the LPF 81 is provided, even if the reflected light of the pulsed light Pa is received by the photodiode 75, the signal component based on the reflected light is removed.

[0133] Each equivalent time sampling pulse SPc (c=1 to N) shown in FIGS. 11 and 12 is input to the S&H 822 at the timing when the reflected light is received after the pulsed light Pa is emitted. That is, the equivalent time sampling pulses SPc are input to the S&H 822 at sampling intervals based on the equivalent time sampling method. The closer the equivalent time sampling pulse SPc is to SP1, SP2, . . . SPn, the later the timing at which the equivalent time sampling pulse SPc is input to the S&H 822 after the pulsed light Pa is emitted. Therefore, the longer the distance L to the other vehicle 3, the later the timing at which the reflected light of the pulsed light Pa is received. That is, by delaying the timing at which the equivalent time sampling pulse SPc is input to the S&H 822, it is possible to receive reflected light according to the distance L. For example, the signal at point P31, where the value of the waveform 992 is greatest, is acquired by the S&H 822 when the equivalent time sampling pulse SPm+2 is input to the S&H 822.

[0134] The difference between a signal based on the luminance etc. when the pre-sampling pulse PPb is input to the S&H 821 and a signal based on the luminance etc. when the equivalent time sampling pulse SPc is input to the S&H 821 is amplified by the differential amplifier 83. The amplified signal is coded by the A / D converter 84 and input to the CPU 101.

[0135] For example, when the first measurement is performed, the difference between the signal based on the luminance, etc. when the pre-sampling pulse PP1 is input to the S&H 821 and the signal based on the luminance, etc. when the equivalent time sampling pulse SP1 is input to the S&H 821 is amplified by the differential amplifier 83. The signal based on the luminance, etc. when the pre-sampling pulse PP1 is input to the S&H 821 and the signal based on the luminance, etc. when the equivalent time sampling pulse SP1 is input to the S&H 821 are noise components (signals with magnitude E1) that do not include light reflected by the reflector 31 of the other vehicle 3, so the noise components cancel each other out, and the output from the differential amplifier 83 is closer to 0 than if they did not cancel each other out.

[0136] When the (m+2)th measurement is performed, the difference between the signal based on the luminance, etc. when the pre-sampling pulse PPm+2 is input to the S&H 821 and the signal based on the luminance, etc. when the equivalent time sampling pulse SPm+2 is input to the S&H 821 is amplified by the differential amplifier 83. The signal based on the luminance, etc. when the pre-sampling pulse PPm+2 is input to the S&H 821 is a noise component (a signal with a magnitude E1). The signal based on the luminance, etc. when the equivalent time sampling pulse SPm+2 is input to the S&H 821 is a signal containing a noise component and reflected light from the reflector 31 of the other vehicle 3 (a signal with a magnitude E2). Therefore, the signal based on the luminance, etc. when the pre-sampling pulse PPm+2 is input to the S&H 821, which is a noise component, is removed from the signal based on the luminance, etc. when the equivalent time sampling pulse SPm+2 is input to the S&H 821. Therefore, the signal with the reduced noise component is coded and input to the CPU 101. That is, a signal of magnitude E3 is amplified, coded, and input to the CPU 101.

[0137] Based on the input signal, the CPU 101 acquires the distance to the other vehicle 3. That is, the CPU 101 can obtain the inter-vehicle distance to the other vehicle 3 based on the pulsed light Pa received by the photodiode 75.

[0138] As described above, the signal acquired by the photodiode 75 may contain various types of noise, such as circuit noise, external electrical noise, and external optical noise. Because the signal level of the reflected light is very small, if the S / N ratio decreases due to the influence of noise, this may cause sensitivity degradation (a reduction in the maximum detection distance) and shorten the distance at which another vehicle 3 can be detected. Using a bandpass filter (BPF) is considered as a means for improving the S / N ratio, but because the signal waveform of the reflected light is a square wave, setting the bandwidth of the BPF too narrow may distort the waveform of the reflected light signal. This may cause sensitivity degradation and shorten the distance at which another vehicle 3 can be detected. Therefore, in this embodiment, a signal synchronized with the noise is generated and subtracted from the equivalent time sampling output signal, thereby reducing the influence of noise without distorting the waveform. Details are described below.

[0139] In this embodiment, a signal based on the difference between a signal acquired before the pulsed light Pa is emitted (a signal acquired at the timing of the pre-sampling pulse PPb) and a signal acquired at a sampling interval using the equivalent sampling method (a signal acquired at the timing of the equivalent-time sampling pulse SPc) is acquired and encoded. The signal acquired by the S&H 821 is a signal that does not contain reflected light and is a noise signal. The signal acquired by the S&H 822 is a signal that contains reflected light and noise. A signal based on the difference between the signal containing reflected light and noise and the noise signal is acquired and encoded, thereby improving the S / N ratio. Furthermore, because a BPF is not used, the waveform of the reflected light is less likely to be distorted. This reduces the possibility of sensitivity degradation and increases the distance at which another vehicle 3 can be detected.

[0140] Furthermore, when a signal containing noise in the same frequency band as the light emitted by LD 72 is acquired by S&H 821, there is a possibility that noise fluctuating in the same frequency band as the light will be superimposed on the optical signal by differential amplifier 83.

[0141] In this embodiment, noise in the same frequency band as the light is reduced by the LPF 81 and acquired by the S&H 821. Therefore, the differential amplifier 83 reduces the possibility that noise that fluctuates in the same frequency band as the light is superimposed on the optical signal. This reduces the possibility of sensitivity degradation and increases the distance at which another vehicle 3 can be detected.

[0142] In this way, as a means of attenuating noise below the desired signal band, two sampling circuits (S&H 821 and S&H 822) are provided in the equivalent time sampling section, separate from the frequency discrimination BPF. One provides a sampling pulse (pre-sampling pulse PPb) at a fixed timing just before the LD 72 emits light, and the other provides it at the normal equivalent time sampling timing. By subtracting the output of the former sampling circuit from the output of the latter sampling circuit using a differential circuit (differential amplifier 83), noise components on the lower side (low frequency side) are strongly attenuated. In addition, noise is reduced by passing the received light signal input to the pre-light emission sampling through LPF 81.

[0143] An example of a method for generating an equivalent time sampling pulse SPc will be described with reference to Fig. 16. The pulse generating circuit 85 shown in Fig. 16 includes integrating circuits 851 and 852 and a comparator 853. The integrating circuits 851 and 852 are electrically connected to the comparator 853.

[0144] In this embodiment, two output voltages with different periods from the integrating circuits 851 and 852 are input to a comparator 853, whereby the timing of the rising and falling edges is swept and an equivalent-time sampling pulse SPc is generated.

[0145] A voltage of waveform 55 is input to integration circuit 851. Waveform 55 is a waveform in which a square wave is repeated. A voltage of waveform 56 is input to integration circuit 852. Waveform 56 is a continuous pulse signal. The period of waveform 55 is greater than the period of waveform 56.

[0146] When waveform 55 is input to integrating circuit 851, waveform 57 is output. Waveform 57 is a waveform that rises at portion 571 and gradually decreases in voltage at portion 572. When waveform 56 is input to integrating circuit 852, waveform 58 is output. Waveform 58 is a waveform that rises at portion 581, becomes a constant voltage at portion 582, and gradually decreases in voltage at portion 583.

[0147] When waveforms 57 and 58 are input to the comparator 853, waveform 59 is output. Waveform 59 is a waveform obtained by outputting an equivalent time sampling pulse SPc, and the timing of its rise and fall is swept. In this manner, in this embodiment, the output voltages (i.e., waveforms 57 and 58) of the two integrating circuits 851 and 852 with different periods are input to the comparator 853, thereby sweeping the timing of its rise and fall and outputting the equivalent time sampling pulse SPc. In this manner, in this embodiment, by applying the voltages of the two integrating circuits 851 and 852 with different periods to the comparator 853, a sampling trigger signal whose rise (or fall) timing is swept can be obtained.

[0148] As described above, in this embodiment, an equivalent time sampling pulse SPc is generated. The equivalent time sampling method allows the received light pulse waveform, which is on the order of several nS to several tens of nS, to be down-converted at an arbitrary magnification. This reduces the need for high speed in the signal processing circuit after receiving light.

[0149] In the above embodiment, the laser inter-vehicle distance meter 1 is an example of an "emitting device" of the present invention. The photodiode 75 is an example of a "light receiving unit" of the present invention. The reflecting surfaces 771 and 772 are an example of a "reflecting unit" of the present invention. The non-reflecting surfaces 774 to 777 are an example of a "non-reflecting unit" of the present invention. The emission control circuit 60 is an example of an "emission control means" of the present invention. The light receiving control circuit 80 is an example of an "equivalent time sampling means" of the present invention. The S&H 821 is an example of a "first acquisition means" of the present invention. The S&H 822 is an example of a "second acquisition means" of the present invention. The differential amplifier 83 is an example of a "third acquisition means" of the present invention. The CPU 101, which measures the distance to another vehicle 3 based on the signal received from the photodiode 75, is an example of a "distance acquisition means" of the present invention.

[0150] The present invention is not limited to the above-described embodiment and various modifications are possible. For example, while the emission area 40 is trapezoidal, this is not limiting. The emission area 40 may have a shape in which at least one of a pair of opposing left-right sides slopes inward as it approaches the upper side. In this case, the brightness of the light irradiated onto the reflector 95 on at least one side of the driving lane 50 in the left-right direction is likely to decrease. Therefore, when detecting another vehicle 3 by detecting light emitted from the laser inter-vehicle distance meter 1, the possibility of erroneously detecting a reflector 95 on the outside of the driving lane 50 is reduced. This improves the detection accuracy of the other vehicle 3. For example, as in the emission area 41 shown in FIG. 17 , if only the right side 413 slopes leftward as it approaches the upper side, the possibility of erroneously detecting the right reflector 95 is reduced.

[0151] Incidentally, it is preferable that the emission area 40 be a triangle shaped to eliminate the influence of the reflectors 95 on the outer lateral sides of the driving lane 50. However, since the upper vertex of the triangle is a point, there is a high possibility that the other vehicle 3 will not be detected if the host vehicle 2 deviates to the left or right from the center of the driving lane 50. Therefore, to more reliably detect the other vehicle 3 even if the host vehicle 2 deviates to the left or right from the center of the driving lane 50, an upper side 405 is provided and the emission area 40 is made trapezoidal, as shown in FIGS. 5 to 7. The length of the upper side 405 of the trapezoidal emission area 40 may be, for example, a length corresponding to the driving lane 50 at the position of the detection target distance for the other vehicle 3.

[0152] As in this embodiment, the light-emitting region 40 may be continuous from the first portion 401 at the top to the second portion 402 at the bottom. In addition, the first portion 401 and the second portion 402 may be separated from each other in the light-emitting region 40. The light-generating portion may be an LED (Light Emitting Diode). It is preferable that the generating unit is a laser diode (LD) 72 as in this embodiment. Even if the laser inter-vehicle distance meter 1 is attached to the inside of the windshield 91, the LD 72 can transmit light through the windshield 91 to reach other vehicles 3 that are farther away.

[0153] Furthermore, it is preferable that the emission area 40 is triangular or rectangular, and that both of a pair of sides facing each other in the left-right direction be shaped so that they incline inward of the emission area 40 as they extend upward. In this case, the brightness of the light irradiated onto both reflectors 95 on the left and right sides of the driving lane 50 is likely to be reduced. Therefore, when detecting another vehicle 3 by detecting light emitted from the laser inter-vehicle distance meter 1, the possibility of erroneously detecting a reflector 95 on the outside of the driving lane 50 is reduced. This improves the detection accuracy of the other vehicle 3. In this embodiment, the emission area 40 is rectangular, and each of a pair of oblique sides 403, 404 facing each other in the left-right direction be shaped so that they incline inward of the emission area 40 as they extend upward.

[0154] It is also preferable that the oblique sides 403, 404 located on the left and right of the trapezoidal emission area 40 are nearly parallel to the left and right lines 501, 502 of the driving lane 50 as viewed from the laser inter-vehicle distance meter 1. For example, if the angle R1 (see FIG. 5) formed between the oblique sides 403, 404 located on the left and right of the trapezoidal emission area 40 and the base 406 is 45 degrees, the angle R2 (see FIG. 5) formed between the left and right lines of the driving lane 50 as viewed from the laser inter-vehicle distance meter 1 and the left-right direction should also be set to 45 degrees. In this case, the brightness of the light irradiated onto the reflector 95 on the outside of the driving lane 50 tends to be low, and the brightness of the light irradiated onto the reflector 31 of the other vehicle 3 tends to be high. Therefore, when detecting the other vehicle 3 by detecting the light emitted from the laser inter-vehicle distance meter 1, the other vehicle 3 can be detected more reliably.

[0155] In addition, it is preferable that each of the oblique sides 403, 404 located on the left and right of the trapezoidal emission area 40 is located slightly outside the left and right lines 501, 502 of the driving lane 50 as seen from the laser inter-vehicle distance meter 1. In this case, it is preferable that light is less likely to be irradiated onto the reflectors located outside the left and right lines 501, 502. It is also preferable that each of the oblique sides 403, 404 located on the left and right of the trapezoidal emission area 40 is located in the same position as the left and right lines 501, 502 of the driving lane 50 as seen from the laser inter-vehicle distance meter 1. It is even more preferable that each of the oblique sides 403, 404 located on the left and right of the trapezoidal emission area 40 is located inside the left and right lines 501, 502 of the driving lane 50 as seen from the laser inter-vehicle distance meter 1. It is also preferable that the emission area 40 is adapted to a road that is relatively wide in the left-right direction, such as a main road. On roads that are wide in the lateral direction, cars tend to travel at high speeds, so the distance to other vehicles 3 is important in terms of driving safety. By using the laser distance meter 1 on roads where speeds tend to be high, driving safety is improved.

[0156] In this embodiment, the brightness gradually increases from the second portion 402 toward the first portion 401 (see FIG. 7). However, it is preferable that the brightness is the same throughout the entire emission region 40. It is also preferable that the brightness is high in the center of the emission region 40 and decreases toward the top, bottom, left, and right. It is also preferable that the brightness of the first portion 401 is lower than the brightness of the second portion 402.

[0157] Furthermore, it is preferable that the optical center axes 912, 913 of the auxiliary lenses 762, 763 are located below the optical center axis 911 of the main lens 761. Because the auxiliary lenses 762, 763 are provided, more downward light can be guided to the photodiode 75 than when only the main lens 761 is provided. Therefore, the area in which the photodiode 75 can receive downward light is larger than when only the main lens 761 is provided.

[0158] Furthermore, although the laser inter-vehicle distance meter 1 has been used as an example in the description, it is preferable that the emitting device of the present invention is not capable of measuring the inter-vehicle distance. For example, the emitting device of the present invention may be a device that can only detect the presence or absence of another vehicle 3, rather than the laser inter-vehicle distance meter 1. Furthermore, it is preferable that the emitting device of the present invention is a device that can emit light but cannot receive reflected light. In this case, it is preferable that the light is received by another device and the other vehicle 3 is detected.

[0159] Furthermore, it is preferable that the LPF 81 (see FIG. 6) is not provided. If the LPF 81 is not provided, costs can be reduced. Furthermore, it is preferable that the light-receiving control circuit 80 has a configuration other than the example shown in FIG. 14. Furthermore, it is preferable that the circuit configuration for emitting light has a configuration other than the example shown in FIG. 13. Furthermore, each of the first resistor 621, the second resistor 622, and the third resistor 614 is not limited to a single resistor, and it is preferable that a plurality of resistors be combined.

[0160] Furthermore, although reflective surfaces 771 and 772 shown in FIG. 8 are formed by polishing inner wall 77 of housing 742, they may be formed by a method other than polishing. For example, reflective surfaces 771 and 772 may be formed from a metal plate, by plating, or by a glossy finish. Furthermore, non-reflecting surface 773 may be a reflective surface. Furthermore, non-reflecting surfaces 773 to 777 may not be provided. Furthermore, reflective surfaces 771 and 772 may not be provided. If reflective surfaces 771 and 772 are not provided, the cost of forming reflective surfaces 771 and 772 can be reduced.

[0161] The photodiode 75 may be arranged in a manner other than that in which one corner 751 is located on the upper side. The photodiode 75 may not be rectangular. A light receiving element other than the photodiode 75 may be used. For example, a CCD may be used.

[0162] The shapes of the auxiliary lenses 762 and 763 may be different from those of this embodiment. The number of auxiliary lenses is not limited. One auxiliary lens may be provided. Three or more auxiliary lenses may be provided. The positions of the auxiliary lenses are not limited. For example, the positions of the auxiliary lenses may be changed depending on the shape of the emission region 40. The shapes of the auxiliary lenses 762 and 763 may be different from those of this embodiment. The auxiliary lenses 762 and 763 may not be provided. The shape of the main lens 761 may not be circular. At least a part of the optical center axes 911 to 913 of the light receiving lens 76 may be located outside the photodiode 75.

[0163] It is also preferable that the light emitting unit 71 and the light receiving unit 74 are adjacent to each other in the vertical direction, which reduces the width in the horizontal direction of the laser inter-vehicle distance meter 1. It is also preferable that the light emitting unit 71 and the light receiving unit 74 are spaced apart from each other.

[0164] Furthermore, the location where the laser inter-vehicle distance meter 1 is mounted is not limited. For example, the laser inter-vehicle distance meter 1 may be mounted on the rear window of the host vehicle 2. The light may be emitted rearward. The laser inter-vehicle distance meter 1 may be disposed outside the host vehicle 2. For example, the laser inter-vehicle distance meter 1 may be disposed at the front or rear end outside the host vehicle 2. The mounting unit 19 may not be provided. In this case, costs can be reduced.

[0165] The external appearance of the laser inter-vehicle distance meter 1 may be, for example, as shown in FIG. 18. The main body 11 of the laser inter-vehicle distance meter 1 includes a housing 110. A light projecting lens 711, a light receiving lens 76, and a speaker 105 are arranged on the front surface 111 of the laser inter-vehicle distance meter 1. A MODE key 121, an UP key 122, a DOWN key 123, and three LEDs 125 are arranged on the back surface 112 of the laser inter-vehicle distance meter 1. The MODE key 121, the UP key 122, and the DOWN key 123 are made of synthetic resin such as plastic. A miniUSB connector 126 is arranged on the top surface 113 of the laser inter-vehicle distance meter 1.

[0166] The CPU 101 (see FIG. 2) detects when the MODE key 121, UP key 122, and DOWN key 123 are pressed. The CPU 101 also controls the illumination of the LED 125. The CPU 101 can communicate with external devices (for example, a PC or a mobile terminal) via a miniUSB connector. Sights 124 are provided at the lower ends of the front face 111 and rear face 112 and are aligned in the front-to-rear direction. A slit is provided at the bottom end of the sight 124. The sight 124 is used when adjusting the orientation of the laser distance meter 1. The user visually observes the slit of the sight 124 from behind and adjusts the orientation of the laser distance meter 1 while aligning the slits of the sights 124 arranged at the front and rear.

[0167] The CPU 101 performs control shown in tables 961 to 964 (see FIGS. 19 to 22) based on data stored in the ROM 106. The CPU 101 outputs the sound shown in table 961 (see FIG. 19) from the speaker 105 based on the inter-vehicle distance to the other vehicle 3 measured using the optical unit 7, etc. As shown in table 961, the sound output by the CPU 101 through control of the speaker 105 can be selected from, for example, sound 1 (announcer-like), sound 2 (anime voice), and a buzzer sound. If a collision will occur within X seconds if the current situation continues, the CPU 101 outputs a collision warning from the speaker 105 to notify the user. Furthermore, for example, if the vehicle approaches the other vehicle 3 further from the position where the collision warning was issued, the CPU 101 outputs a collision warning from the speaker 105 to notify the user. The collision warning differs depending on whether the vehicle is traveling at a low speed or a high speed (see "Collision Warning (Low Speed)" and "Collision Warning (High Speed)" in table 961). Also, if the vehicle 3 ahead starts moving while the host vehicle 2 is stopped, the CPU 101 outputs start information from the speaker 105 to notify the user.

[0168] When set to voice 1 (announcer style), the CPU 101 outputs the collision warning "Ah," the collision warning (low speed) "It's dangerous," the collision warning (high speed) "Danger," and the start information "Vehicle ahead departs." When set to voice 2 (anime voice), the CPU 101 outputs the collision warning "Eek," the collision warning (low speed) "Be careful," the collision warning (high speed) "Danger!", and the start information "Go!" When set to buzzer sound, the CPU 101 outputs the collision warning "Beep beep," the collision warning (low speed) "Beep beep beep," the collision warning (high speed) "Beep beep beep beep," and the start information "Pu pu pu pu."

[0169] When the UP key 122 or the DOWN key 123 is pressed and held, the CPU 101 sets the sensitivity shown in the table 962 (Fig. 20). The sensitivity setting can be set between 0 and 3. When the UP key 122 is pressed and held, the CPU 101 increases the sensitivity setting from 0 toward 3. When the DOWN key 123 is pressed and held, the CPU 101 decreases the sensitivity setting from 3 toward 0. The sensitivity setting of "0" is a "non-detection" setting. When the sensitivity setting is set to "0", the CPU 101 does not detect other vehicles 3. Furthermore, the sensitivity increases as the sensitivity setting moves from 1 to 3. In other words, the CPU 101 makes it easier to detect other vehicles 3.

[0170] The CPU 101 can set the state of the laser inter-vehicle distance meter 1 to one of "S1. Operation mode," "S2. Glass correction mode," and "S3. Detection confirmation mode" shown in table 963 (see FIG. 21). The operation mode is a mode for normal operation. The glass correction mode is a mode for reducing the influence of the windshield 91.

[0171] The glass correction mode will be described in more detail. A portion of the light emitted from the LD 72 and reaching the windshield 91 is reflected by the windshield 91 and reflected toward the photodiode 75. For example, if the light emitted from the LD 72 and reaching the windshield 91 is taken as 100%, 95% is transmitted through the windshield 91 and emitted forward. Then, 2 to 3% of the light is reflected by the windshield 91 and reaches the photodiode 75.

[0172] On the other hand, a portion of the light that passes through the windshield 91 and is emitted forward is reflected by the reflector 31 of the other vehicle 3 in front and reaches the photodiode 75. Because the reflector 31 is present in a portion of the light irradiation range, the amount of light that is reflected by the reflector 31 and reaches the photodiode 75 is less than 1%. In other words, the amount of light that is reflected by the reflector 31 and reaches the photodiode 75 (less than 1%) is small compared to the amount of light that is reflected by the windshield 91 and reaches the photodiode 75 (2 to 3%). For this reason, the influence of light that is reflected by the windshield 91 and reaches the photodiode 75 is large. The glass correction mode is performed to reduce the influence of light that is reflected by the windshield 91 and reaches the photodiode 75.

[0173] Specifically, in the glass correction mode, light is emitted from the LD 72 when there is no other vehicle 3 ahead. Because there is no other vehicle 3 ahead, the light is not reflected by the reflector 31. Therefore, the CPU 101 can acquire the luminance of light reflected by the windshield 91 and reaching the photodiode 75. In the glass correction mode, the CPU 101 stores the luminance of light reflected by the windshield 91 and reaching the photodiode 75 in the RAM 107 or another storage medium. When detecting another vehicle 3 in the operation mode, the CPU 101 subtracts the luminance of light reflected by the windshield 91 and reaching the photodiode 75, which was stored in the glass correction mode, from the luminance of the detected light. This reduces the influence of light reflected by the windshield 91 and reaching the photodiode 75.

[0174] As shown in table 963, in "S1. Operation mode," if the UP key 122 is pressed for a short time, the CPU 101 increases the volume of sound output from the speaker 105. If the DOWN key 123 is pressed for a short time, the CPU 101 decreases the volume of sound output from the speaker 105. If the UP key 122 is pressed for a long time, the CPU 101 increases the sensitivity (see FIGS. 20 and 21). If the DOWN key 123 is pressed for a long time, the CPU 101 decreases the sensitivity (see FIGS. 20 and 21). If the MODE key 121 is pressed for a short time, the CPU 101 switches between voice and buzzer. More specifically, the switching occurs between voice 1 (announcer-like), voice 2 (anime voice), and buzzer sound, as shown in table 961 (see FIG. 19). If the MODE key 121 is pressed for a long time, the CPU 101 transitions the state of the laser inter-vehicle distance meter 1 to "S2. Glass correction mode."

[0175] The glass correction mode changes among "S2-1. Neutral," "S2-2. In progress," and "S2-3. Completed." "S2-1. Neutral" is a mode that does nothing when set and waits for glass correction to be performed or for the cancel key to be pressed. If the MODE key 121 is pressed and held, the CPU 101 determines that the cancel key has been pressed. In this case, the CPU 101 does not perform glass correction and shifts the state of the laser distance meter 1 to "S3. Detection confirmation mode." If the DOWN key 123 is pressed for a short time, the CPU 101 shifts the state of the laser distance meter 1 to "S2-2. In progress" in order to perform glass correction.

[0176] In "S2-2. Executing", the CPU 101 executes the glass correction. After about three seconds have elapsed since the start of the glass correction, the CPU 101 shifts the state of the laser inter-vehicle distance meter 1 to "S2-3. Completed". In "S2-3. Completed", the CPU 101 notifies the result of the determination as to whether the glass correction was executed normally (OK or NG). The notification is made, for example, by outputting a sound from the speaker 105 or by controlling the lighting of the LED 125. If the glass correction was executed normally (OK), the CPU 101 shifts the state of the laser inter-vehicle distance meter 1 to "S1. Operation Mode". If the glass correction was not executed normally, the CPU 101 shifts the state of the laser inter-vehicle distance meter 1 to "S2-1. Neutral".

[0177] As described above, when the MODE key 121 is pressed and held in "S2-1. Neutral", the CPU 101 transitions the state of the laser inter-vehicle distance meter 1 to "S3. Detection confirmation mode". The detection confirmation mode is a mode for checking whether the orientation of the laser inter-vehicle distance meter 1 is correct, etc. In the detection confirmation mode, for example, the detected distance is expressed by the pitch of a beep. When the UP key 122 is pressed for a short time, the CPU 101 increases the volume output from the speaker 105. When the DOWN key 123 is pressed for a short time, the CPU 101 decreases the volume output from the speaker 105. When the MODE key 121 is pressed and held, the CPU 101 transitions the state of the laser inter-vehicle distance meter 1 to "S1. Operation mode".

[0178] The CPU 101 controls the state of the LED 125 as shown in a table 964 (see FIG. 22). LED1, LED2, and LED3 in the table 963 are included in the LED 125 (see FIG. 18). LED1 is an LED for indicating the state (state of the device) of the laser inter-vehicle distance meter 1. LED2 is an LED for indicating warnings and notifications to the user. LED3 is an LED for indicating errors to the user.

[0179] Assume that the laser inter-vehicle distance meter 1 is in the operation mode (see FIGS. 21 and 22). In this case, the CPU 101 lights up the LED 1 green. Furthermore, when the state is "collision warning (high speed)," "collision notice (low speed)," "collision notice," "start information," "volume change," "sensitivity change," "alert sound change (voice)," or "alert sound change (buzzer)," the CPU 101 controls the LED 2 to be "red flashing," "yellow flashing," "yellow flashing," "blue flashing," "yellow lit (1 sec)," "blue lit (1 sec)," "blue lit (1 sec)," or "yellow lit (1 sec)," respectively.

[0180] Furthermore, when the status of "Err (error) 1", "Err2", "Err3", "Err4", or "Err5" occurs, the CPU 101 controls the LED 3 to "blink red", "blink blue", "blink yellow", "blink green", or "blink white", respectively. Err1 is an error indicating that glass correction has not been completed. Err2 is an error indicating that the aging time is in progress after power-on. Err3 is an error indicating that operation has stopped due to high temperature.

[0181] Assume that the laser inter-vehicle distance meter 1 is in the glass correction mode (see FIGS. 21 and 22). In this case, the CPU 101 lights up LED1 yellow. Furthermore, when the status is "in progress," "completed (success)," or "not executed or completed (failed)," the CPU 101 controls LED2 to light up green, "blue," or "red," respectively. "Not executed or completed (failed)" means that the glass correction has not been completed.

[0182] Assume that the laser inter-vehicle distance meter 1 is in the detection confirmation mode (see FIGS. 21 and 22). In this case, the CPU 101 causes LED 1 to blink yellow. Furthermore, the CPU 101 causes LED 2 to light red when no preceding vehicle (i.e., another vehicle 3) is detected, and causes LED 2 to light green when a preceding vehicle is detected. As described above, the CPU 101 performs the control shown in tables 961 to 964. [Explanation of symbols]

[0183] 1 Laser distance meter 2 Vehicle 3 Other vehicles 7 Optical Unit 31,95 Reflector 40,41 Output area 50 driving lanes 60 Emission control circuit 62 split resistor 63 DC / DC converter 64 Integral circuit 71 Emission unit 74 Light receiving unit 75 photodiodes 76 Receiving lens 80 Light receiving control circuit 83 Differential Amplifier 84 A / D converters 89,891,892,893 Light receiving area 401 First part 402 Second part 403,404 Hypotenuse 614 Third resistor 621 First resistor 622 Second resistor 633 Reference input terminal 651 Fourth resistor 750 incidence area 751 Corner 752,753,755,756 sides 761 Main Lens 762,763 Auxiliary Lens 771,772 reflective surface 773~777 Hardly reflective surface 911,912,913 Optical central axis

Claims

1. A device for detecting an object through a vehicle window, a light emitting unit, a light receiving unit, and a control unit; The control unit executes a process in a glass correction mode and a process in an operation mode, In the processing of the glass correction mode, brightness information of light that is emitted from the light emitting unit in a state where the object to be detected is not present in the emission direction of the light emitting unit and is reflected and reaches the light receiving unit is acquired and stored; The device is characterized by having a function of correcting the signal from the light receiving unit based on the stored luminance information and detecting the object in the processing of the operation mode.

2. The device according to claim 1, characterized in that, in addition to the glass correction mode processing and the operation mode processing, the control unit has a function of executing a detection confirmation mode processing that detects an object through the glass of a vehicle based on a user's operation and notifies whether or not an object has been detected.

3. The device according to claim 1 or 2, characterized in that the control unit has a function of issuing a notification according to each state of the glass correction mode: "in progress," "completed (success)," or "not yet executed or completed (failed)."

4. 4. The device according to claim 1, further comprising a function for assigning different functions to operation buttons in the glass correction mode process and the operation mode process.

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