Injection 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 that emits light or the like, and the like. [Background Art]

[0002] Conventionally, emission devices that are mounted on automobiles and emit electromagnetic waves are known. For example, the code-modulation radar distance measuring device described in Patent Document 1 emits code-modulated or spectrum-spread electromagnetic waves. The code-modulation radar distance measuring device receives, by means of a receiver, an electromagnetic wave reflected by a distance measurement object such as an automobile, and calculates the distance to the distance measurement object. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. 11-83991 [Summary of the Invention] [Problems to be Solved by the Invention]

[0004] As an electromagnetic wave used when detecting the distance to a distance measurement object, for example, light such as infrared light is used. At the left and right ends and the outer side of the driving lane of a vehicle (hereinafter simply referred to as "the outer side of the driving lane"), there are reflectors provided, for example, on the center line of a road, a road shoulder, a curb of a sidewalk, and the like. For this reason, the light emitted by the above-described emission device is reflected particularly by the reflector provided on the outer side of the driving lane. Therefore, when the emission device detects an automobile, there is a possibility that the light reflected by the reflector provided on the outer side of the driving lane is erroneously detected, and the accuracy of detecting the automobile decreases.

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

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

[0007] When viewed from the emission direction from an emission device positioned on a first vehicle traveling in a straight lane, the second vehicle is positioned higher and smaller the further it is from the emission device. Similarly, the lane is positioned higher and narrower in the lateral direction the further it is from the emission device. In this invention, the emission area has a lateral width of the first part, which corresponds to the far position, which is smaller than the lateral width of the second part, which is the lower part of the first part. The first part is for detecting the second vehicle when it is at a far position. The second part is for detecting the second vehicle when it is at a close position. The emission area is set to match the size of the second vehicle and the lateral width of the lane. Therefore, when the emission area is aligned with a straight lane, the amount of light from the emission area illuminating the reflector outside the lane becomes smaller. Consequently, when detecting the second vehicle by detecting the light emitted from the emission device, the possibility of false detection of the reflector outside the lane is reduced. Thus, the detection accuracy of the second vehicle is improved. Furthermore, it is preferable that the first and second parts be separated within the emission region. Also, the emission region should be continuous from the first to the second part.

[0008] For example, the emission unit comprises a light generation unit and an emission lens unit that refracts the light generated by the generation unit and emits it into the emission area. In this case, the emission device can concentrate the light into the emission area by refracting the light with the emission lens unit. Therefore, it is not necessary to make the shape of the generation unit a special shape for emitting light into the emission area. Thus, the cost of the generation unit can be reduced. The generation unit can be an LED (Light Emitting Diode). In particular, the generation unit can be an LD (Laser Diode). In this case, even if the emission device is mounted on the inside of the windshield, the light can be transmitted through the windshield and reach a second vehicle that is further away.

[0009] Furthermore, the emission area is preferably rectangular, with at least one of the pair of sides facing each other in the left-right direction inclined inward as it extends upward. In this case, the brightness of the light illuminating the reflector on at least one side of the driving lane in the left-right direction tends to be lower. Therefore, when detecting a second vehicle by detecting the light emitted from the emission device, the possibility of falsely detecting a reflector on the outside of the driving lane is reduced. Thus, the detection accuracy of the second vehicle is improved.

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

[0011] Furthermore, the emission area should be triangular or quadrilateral in shape, with both sides of a pair of opposing sides inclined inward as they move upward. In this case, the brightness of the light illuminating both reflectors on the left and right sides of the driving lane tends to decrease. Therefore, when detecting a second vehicle by detecting the light emitted from the emission device, the possibility of falsely detecting a reflector on the outside of the driving lane is reduced. Thus, the detection accuracy of the second vehicle is improved.

[0012] Incidentally, the emission area could be a triangle with a shape that eliminates the influence of reflectors on the outside of the driving lane. However, since the upper vertex of the triangle is a point, if the first vehicle deviates to the left or right from the center of the driving lane, there is a high possibility that the second vehicle will not be detected. Therefore, to ensure more reliable detection even when the first vehicle deviates to the left or right from the center of the driving lane, an upper side is provided, making the emission area a trapezoid. The length of the upper side of the trapezoidal emission area should, for example, be the length corresponding to the driving lane at the target distance of the second vehicle.

[0013] Furthermore, for example, the emission device should be equipped with a mounting part that allows it to be mounted on the first vehicle so that the emission direction is horizontal. Also, it is preferable that the slanted sides located on the left and right of the trapezoidal emission area and the lines on the left and right of the driving lane as seen from the emission device are nearly parallel. For example, if the angle between each of the slanted sides located on the left and right of the trapezoidal emission area and the base is 45 degrees, it is preferable to set the angle between the lines on the left and right of the driving lane as seen from the emission device and the left and right direction to be 45 degrees. In this case, the brightness of the light illuminating the reflector on the outside of the driving lane tends to be low, and the brightness of the light illuminating the reflector on the second vehicle tends to be high. Therefore, when detecting the second vehicle by detecting the light emitted from the emission device, the second vehicle can be detected more reliably. It is preferable that each of the slanted sides located on the left and right of the trapezoidal emission area is slightly outside the lines on the left and right of the driving lane as seen from the emission device. In this case, it is desirable that light is less likely to shine on reflectors located outside the lines on either side of the driving lane as seen from the light emitter. Furthermore, it is desirable that the slanted sides on either side of the trapezoidal emission area be in the same position as the lines on either side of the driving lane as seen from the light emitter. Even more desirable, it is desirable that the slanted sides on either side of the trapezoidal emission area be inside the lines on either side of the driving lane as seen from the light emitter. In addition, the emission area should be designed to match roads that are relatively wide in the lateral direction, such as main roads. On roads that are wide in the lateral direction, vehicle speeds tend to be higher, so the distance to the second vehicle becomes important in terms of driving safety. By using a light emitter on such roads where speeds tend to be high, driving safety is improved.

[0014] (3) In the emission area of ​​the emission device, the brightness of the light from the first part is preferably greater than the brightness of the light from the second part. In this case, the light can travel further than when the brightness of the light from the first part is less than or equal to the brightness of the light from the second part. The brightness of the first part for detecting the second vehicle at a distance is greater, and the light can travel further, so when detecting the second vehicle by detecting the light emitted from the emission device, the second vehicle at a greater distance can be detected.

[0015] (4) The emission device includes a light receiving unit that receives reflected light from the light emitted by the emission unit, and the upper part of the light receiving unit is preferably shaped to conform to the upper part of the region into which the reflected light from the emission unit is incident. In this case, compared to the case in which the light receiving unit is not shaped to conform to the upper part of the light emission region, the area of ​​the light receiving area of ​​the light receiving unit that can be used to receive light emitted from the emission unit can be increased. Therefore, a wider range of light can be received. Therefore, the emission device can further improve the detection accuracy of the second vehicle.

[0016] For example, a single photodiode is used as the light-receiving unit. When a single photodiode is used, if the area of ​​the light-receiving unit that can be used to receive light emitted from the emission region is small, the sensitivity will decrease. However, as in the present invention, by shaping the light-receiving unit to follow the upper part of the area into which reflected light from the light emission region is incident, the area that can be used to receive light emitted from the emission region is increased, thereby improving the sensitivity even with a single photodiode. Therefore, the emission device can further improve the detection accuracy of the second vehicle.

[0017] (5) In the emission device, the emission area is a trapezoidal shape projected onto a plane normal to the emission direction, with the first part at the top and the second part at the bottom, and the light receiving part is a rectangle, preferably with one corner located on the upper side. When one corner of the rectangular light receiving part is located on the upper side, both sides forming the upper corner are aligned with the upper part of the area into which the reflected light of the trapezoidal emission area is incident. Therefore, compared to the case where the light receiving part is arranged so that the upper side of the rectangle is parallel to the left-right direction, the area of ​​the light receiving area that can be used to receive the reflected light of the light emitted to the emission area can be increased. Thus, a wider range of light can be received. Therefore, the emission device can further improve the detection accuracy of the second vehicle when using a rectangular light receiving part.

[0018] (6) The emission device includes a light-receiving lens that guides the reflected light to the light-receiving section, and the light-receiving lens has a plurality of optical central axes, which are preferably located inside the light-receiving section. Here, in order to widen the light-receiving area of ​​the light-receiving section, means such as increasing the area of ​​the light-receiving section or shortening the focal length of the light-receiving lens can be considered. If the area of ​​the light-receiving section is increased, the capacitance of the light-receiving section increases, and the waveform when light is received becomes more easily distorted. This may reduce the detection accuracy of the second vehicle. Therefore, there is a limit to how much the light-receiving section can be enlarged. Also, if the focal length of the light-receiving lens is shortened, the area of ​​the light-receiving lens decreases, and the light-gathering ability of the light-receiving lens decreases. This may reduce the detection accuracy of the second vehicle. Therefore, there is a limit to how much the focal length of the light-receiving lens can be shortened.

[0019] In this invention, the light-receiving lens has multiple optical central axes. Therefore, compared to a lens with one optical central axis, the light-receiving area that the light-receiving part can receive is larger. In other words, the light-receiving area can be increased without increasing the area of ​​the light-receiving part. Because the light-receiving area is larger, a second vehicle located in a wider area can be detected, and the detection accuracy of the second vehicle is improved.

[0020] Furthermore, compared to a system with a single optical central axis, this system allows for a larger light-receiving area while suppressing the decrease in light-gathering ability due to the smaller size of the light-receiving lens. Because the light-receiving area is larger, it is possible to detect a second vehicle located in a wider area, improving the detection accuracy of the second vehicle.

[0021] (7) In the light emission device, the light receiving lens comprises a main lens and an auxiliary lens, wherein the auxiliary lens is positioned below the main lens, and the optical central axis of the auxiliary lens is positioned below the optical central axis of the main lens. In this case, more light from below can be guided to the light receiving unit than when only a main lens is provided. Therefore, the area in which the light receiving unit can receive light from below is larger than when only a main lens is provided.

[0022] Here, when viewed from the ejection device, the farther the distance from the ejection device to the second vehicle, the higher the reflector on the second vehicle is positioned, and the closer the distance from the ejection device to the second vehicle, the lower the reflector on the second vehicle is positioned. In this invention, by increasing the area that can receive light from below, the area that can receive light in the vertical direction is increased. Therefore, the range of distances at which the reflector on the second vehicle can be detected is increased compared to the case where only a main lens is provided. Also, the lens does not become excessively large compared to the case where the light receiving range is increased with a single lens. Therefore, the possibility of the ejection device becoming larger can be reduced. Furthermore, it is preferable that the auxiliary lens be smaller than the main lens.

[0023] (8) In the emission device, the auxiliary lenses are provided in pairs in the left-right direction, and the optical central axis of one of the auxiliary lenses is located to one side in the left-right direction relative to the optical central axis of the main lens, and the optical central axis of the other auxiliary lens is located to the other side in the left-right direction relative to the optical central axis of the main lens. In this case, the auxiliary lenses are provided in pairs in the left-right direction below the main lens. Therefore, compared to the case where only one auxiliary lens is provided, the light-receiving range of the lower part of the light-receiving area is larger in the left-right direction. In the present invention, since the second part is located below the first part, the left-right width of the lower part of the emission area tends to be larger than the left-right width of the upper part. However, by providing two auxiliary lenses, the light-receiving range can be set to match the width of the lower part of the emission area. Therefore, reflected light from the light emitted to the emission area can be received more reliably, and the detection accuracy of the second vehicle is further improved. Furthermore, it is preferable that one of the auxiliary lenses has a shape that is symmetrical to the other auxiliary lens. Furthermore, it is desirable that the optical central axis of one auxiliary lens and the optical central axis of the other auxiliary lens are symmetrically positioned with respect to the optical central axis of the primary lens.

[0024] Note that the main lens and the auxiliary lens are preferably formed integrally. In this case, compared to the case where the main lens and the auxiliary lens are formed separately, light is less likely to bend and reflect at the boundary between the main lens and the auxiliary lens. Therefore, light can be more reliably guided to the light receiving unit than in the case where the main lens and the auxiliary lens are formed separately. Accordingly, the detection accuracy for the second vehicle is improved.

[0025] (9) In the emission device described above, the main lens is preferably circular, and the auxiliary lens preferably has the same shape as the region of the main lens adjacent to the auxiliary lens. In this case, the reflected light is received by the light receiving unit in a state where the focal lengths of the main lens and the auxiliary lens are the same. Therefore, the detection accuracy for the second vehicle is improved compared to the case where the main lens and the auxiliary lens have different focal lengths from each other.

[0026] (10) The emission device preferably includes: a housing that supports the light receiving unit and the light receiving lens; and a reflection unit provided in the housing that reflects part of the light incident from the light receiving lens and guides the reflected part to the light receiving unit. In this case, the brightness of the reflected light reaching the light receiving unit is higher than that in the case where no reflection unit is provided. Accordingly, the emission device can detect the second vehicle more reliably.

[0027] (11) The emission device includes a low-reflection unit provided below the light receiving unit in the housing, the low-reflection unit being less likely to guide the light to the light receiving unit than the reflection unit, and the reflection unit preferably reflects at least the light that reaches a position above the light receiving unit and guides the reflected light to the light receiving unit. Part of the light from the periphery of the second region of the emission region reaches a position above the light receiving unit via the main lens or the auxiliary lens. The light that reaches a position above the light receiving unit is guided to the light receiving unit by the reflection unit. Therefore, the emission device can detect a nearby second vehicle more reliably. On the other hand, part of the light from the periphery of the first region of the emission region reaches a position below the light receiving unit. Since the low-reflection unit is provided below the light receiving unit, light is less likely to be reflected there. The travel lane at the position where the light from the first region of the emission device is emitted has a narrow width in the left-right direction, so that reflectors outside the travel lane are easily irradiated with light, but since the light is less likely to be guided to the light receiving unit by the low-reflection unit, the possibility of erroneously detecting a reflector can be further reduced.

[0028] (12) In the emission device described above, the light receiving section is quadrilateral, with one corner located on an upper side, and the reflection section preferably extends from each of a pair of sides forming the one corner. In this case, the light reflected by the reflection section can more reliably reach the light receiving section. Therefore, the detection accuracy for the second vehicle is improved.

[0029] (13) In the emission device described above, the emission section and the light receiving lens are preferably arranged adjacent to each other. In this case, compared to a case where the emission section and the light receiving lens are spaced apart from each other, an emission region and a region that receives light by the light receiving section are more likely to overlap. Therefore, the detection accuracy for the second vehicle is improved.

[0030] (14) The emission device includes: emission control means for causing the emission section to emit the light; and equivalent time sampling means for sampling a signal including the light received by the light receiving section at a sampling interval according to an equivalent time sampling method. The emission control means preferably changes the luminance of the emitted light according to the time from when the light is emitted until the sampling is performed by the equivalent time sampling means. For example, the shorter the distance from the emission device to the second vehicle is, the higher the luminance of the reflected light received by the light receiving section tends to be. Further, for example, depending on characteristics of a light-emitting side lens, characteristics of a light-receiving side lens, or the like, when the distance from the emission device to the second vehicle falls within a predetermined distance range, the luminance of the reflected light received by the light receiving section may become high. When the luminance of the reflected light received by the light receiving section increases, there is a possibility that an amplifier circuit becomes saturated when a voltage based on the reflected light received by the light receiving section is amplified by the amplifier circuit or the like. For this reason, it takes time for the amplifier circuit to return to a normal state after saturation, which may reduce the detection accuracy for the second vehicle.

[0031] In the equivalent time sampling method, the time from when light is emitted from the light-emitting unit until it is sampled changes depending on the distance to the second vehicle. In this invention, the brightness of the emitted light changes depending on the time from when light is emitted from the light-emitting unit until it is sampled. For this reason, for example, in the range where the amplifier circuit may saturate, the brightness of the light emitted from the light-emitting unit can be reduced. Thus, the possibility of the amplifier circuit saturating is reduced. Furthermore, even if saturation occurs, the recovery time from saturation can be shortened. Thus, the detection accuracy of the second vehicle is improved. In addition, power consumption is reduced compared to a case where the brightness of the light does not change and light is always emitted at a brightness sufficient to detect a distant second vehicle. Furthermore, because the equivalent time sampling method has a period of time when no light is emitted, it prevents strong light from being continuously output.

[0032] Incidentally, because the frequency of light pulses is high (for example, the unit of pulse frequency is nanosecs), a very high sampling frequency is required, which can lead to problems such as high component costs. Therefore, in this invention, sampling is performed by an equivalent sampling method.

[0033] The light emitter emits light of the necessary intensity to reach the furthest point within the range of detection for the second vehicle. Therefore, the light intensity may be high. Furthermore, if the light emitter is installed inside the vehicle, for example, it is necessary to transmit the light through the windshield, etc., which may further increase the light intensity. When continuously emitting high-intensity light, it is necessary to consider the impact on human eyes. Therefore, instead of continuously emitting light, pulsed light is emitted, and periods of no light emission are included to reduce the average value of the light intensity. This reduces the impact on human eyes. For example, the interval between pulses should be twice as large as the pulse width. More preferably, the interval between pulses should be 1000 times or more larger than the pulse width.

[0034] (15) In the emission device, the emission control means should emit light with a lower brightness to the emission unit as the time from emission of the light to sampling by the equivalent time sampling means is shorter. The closer the distance from the emission device to the second vehicle, the more likely it is that the brightness of the light received by the light receiving unit will be. In the present invention, the shorter the time from emission of the light to sampling by the equivalent time sampling means, the lower the brightness of the light emitted from the light emitting unit. Therefore, compared to the case where 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. Thus, the possibility of the amplifier circuit becoming saturated can be reduced, and the detection accuracy of the second vehicle can be improved.

[0035] (16) In the emission device, the emission control means includes a power supply circuit that supplies voltage to the emission unit, the power supply circuit includes 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 divider resistor used to set the output voltage of the DC / DC converter by inputting a divided voltage to the reference input terminal of the DC / DC converter, the integrating circuit to which a pulse signal is input, and the third resistor provided between the output side of the integrating circuit and the reference input terminal, the pulse signal is input to the integrating circuit, the voltage applied to the reference input terminal fluctuates, and the output voltage of the DC / DC converter fluctuates, so that the shorter the time from when the light is emitted until it is sampled by the equivalent time sampling means, the weaker the light emitted to the emission unit. In this case, by fluctuating the voltage input to the reference input terminal by the output from the integrating circuit, the function can be realized in which the shorter the time from when the light is emitted until it is sampled by the equivalent time sampling means, the weaker the light emitted to the light-emitting unit.

[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 according to the equivalent time sampling method after the light has been 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. Since the signal level of reflected light is very small, if the signal-to-noise ratio (S / N ratio) decreases due to the influence of noise, it can lead to a decrease in sensitivity, and the distance at which the second vehicle can be detected may be shortened. One way to improve the S / N ratio is to use a bandpass filter (BPF), but since the signal waveform of reflected light is a square wave, if the bandwidth of the BPF is narrowed, the waveform of the reflected light signal may be distorted. This can lead to a decrease in sensitivity, and the distance at which the second vehicle can be detected may be shortened.

[0038] In this invention, a signal is acquired and encoded based on the difference between a signal acquired before light is emitted and a signal acquired at a sampling interval using the equivalent sampling method. The signal acquired by the first acquisition means is a signal that does not include reflected light and is a noise signal. The signal acquired by the second acquisition means is a signal that includes reflected light and noise. Since a signal is acquired and encoded based on the difference between the signal including reflected light and noise and the noise signal, the signal-to-noise ratio can be improved. In addition, since a band-pass filter is not used, the waveform of the reflected light is less likely to be distorted. Therefore, the possibility of sensitivity degradation is reduced, and the distance at which a second vehicle can be detected is increased.

[0039] (18) The emission device is equipped with a low-pass filter that allows a band of the signal received by the light receiving unit to pass through a band with a frequency lower than that of the light, and the first acquisition means may acquire the signal after it has passed 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 the noise fluctuating in the same frequency band as the light will be superimposed on the light signal by the third acquisition means. In the present invention, the noise in the same frequency band as the light is reduced by the low-pass filter and acquired by the first acquisition means. Therefore, the possibility of noise fluctuating in the same frequency band as the light being superimposed on the light signal by the third acquisition means is reduced. As a result, the possibility of sensitivity degradation is reduced, and the distance at which the second vehicle can be detected is increased.

[0040] (19) The emission device may be provided with distance acquisition means for acquiring the distance to an object based on the signal received from the light receiving unit. In this case, the emission device can obtain the distance between the vehicle and the second vehicle. [Brief explanation of the drawing]

[0041] [Figure 1] This is a view from inside vehicle 2, looking forward. [Figure 2] This is a block diagram showing the electrical configuration of the laser inter-vehicle distance meter 1. [Figure 3] This is a perspective view of the optical unit 7. [Figure 4] This is a plan view of the optical unit 7. [Figure 5] This figure shows the shape of the emission area 40 when viewed from the front of the laser distance meter 1. [Figure 6] This diagram shows the case where another vehicle 3 is located closer to the position shown in Figure 5. [Figure 7] This figure shows the brightness, etc., of the emission area 40. [Figure 8] This is a front view of the optical unit 7 with the light-emitting lens 711 and light-receiving lens 76 removed. [Figure 9] This is a front view of the optical unit 7. [Figure 10] This is a longitudinal cross-sectional view of the light receiving unit 74 in the light unit 7. [Figure 11] This diagram illustrates the method for measuring the distance between another vehicle 3 and the laser distance meter 1. [Figure 12] This is another diagram illustrating the method for measuring the distance between another vehicle 3 and the laser distance meter 1. [Figure 13] This is a block diagram of the injection control circuit 60. [Figure 14] This is a block diagram of the light receiving control circuit 80. [Figure 15] Figure 14 shows an example of light reception control by the light reception control circuit 80. [Figure 16] This is a block diagram of the pulse generation circuit 85. [Figure 17] This figure shows the ejection region 41 related to the modified form. [Figure 18] This is an external view of the laser distance meter 1. [Figure 19] This is a diagram of Table 961. [Figure 20] This is a diagram of Table 962. [Figure 21] This is a diagram of Table 963. [Figure 22] This is a diagram of Table 964. [Modes for carrying out the invention]

[0042] The following description will explain a laser distance meter 1, which is an example of the present invention, with reference to the drawings. In the following description, the top, bottom, right, left, front, and back sides of Figure 1 will be described as the top, bottom, right, left, rear, and front sides of the laser distance meter 1 and the vehicle 2, respectively.

[0043] Referring to Figures 1 and 2, the overview of the laser distance meter 1 will be described. The laser distance meter 1 is mounted on the vehicle 2 and emits light in the emission direction, which is either in front of or behind the vehicle 2. In this embodiment, the emission direction from which the light is emitted is the forward direction of the laser distance meter 1. The laser distance meter 1 receives reflected light from the 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 distance meter 1 and the other vehicle 3. In this embodiment, the reflector 31 of the other vehicle 3 is provided at the 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] Figure 1 shows the view from inside the vehicle 2 looking forward. In Figure 1, the rearview mirror 29 is shown by a dotted line. The laser distance meter 1 is positioned in front of the rearview mirror 29.

[0045] As shown in Figure 1, the laser distance meter 1 comprises a main body 11 and a mounting part 19. The mounting part 19 includes a mounting part 191 and a support part 192. The main body 11 is roughly rectangular in shape. The support part 192 extends upward from the top of the main body 11. The mounting part 191 is provided at the upper end of the support part 192. The mounting part 191 is roughly rectangular in shape and is attached to the center and upper part of the windshield 91 in the left-right direction using, for example, double-sided adhesive tape or a suction cup. This mounts the laser distance meter 1 to the windshield 91. The mounting part 19 supports the main body 11 so that its angle can be changed. Therefore, the laser distance meter 1 can be mounted on the vehicle 2 such that the emission direction is horizontal. The laser distance meter 1 may be mounted in other locations, for example, on the back of the rearview mirror 29 with a mounting part for mounting on the back of the rearview mirror 29, but it is preferable to mount it on the windshield 91 as in this embodiment. In this way, it is possible to suppress changes in the relative distance between the laser distance meter 1 and the windshield 91 due to vehicle vibrations, and the measurement accuracy of the laser distance meter 1 can be improved compared to other mounting locations.

[0046] As shown in Figure 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, etc. The light emitted and received by the optical unit 7 passes through a transparent plate (not shown) and a windshield 91 provided on the front of the main body 11.

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

[0048] The light-emitting circuit 102 is electrically connected to the LD72. The CPU 101 controls the lighting and extinguishing of the LD72 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. Based on the transmitted signal, the CPU 101 measures the distance between the other vehicle 3 and the laser distance meter 1.

[0049] The audio circuit 104 is electrically connected to the speaker 105. The CPU 101 controls the audio circuit 104 to output sound from the speaker 105. For example, the CPU 101 outputs sound from the speaker 105 when the distance between the other vehicle 3 and the laser distance meter 1 falls below a predetermined distance. In this way, the CPU 101 notifies the driver of the vehicle 2 that the distance between the other vehicle 3 and the laser distance meter 1 has fallen below a predetermined distance. Also, for example, the CPU 101 outputs sound from the speaker 105 when the distance between the laser distance meter 1 and the other vehicle 3 decreases by a predetermined distance (e.g., 10 m) or more within a predetermined time (e.g., 0.3 seconds). In this way, the CPU 101 notifies the driver of the 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, the light-emitting unit 71 and the light-receiving unit 74 are integrally formed. The light-emitting unit 71 and the light-receiving unit 74 are adjacent to each other. Therefore, the light-receiving lens 76 provided on the front of the light-receiving unit 74 is adjacent to the light-emitting unit 71. The light-receiving unit 74 is provided to the right of the light-emitting unit 71.

[0051] The light-emitting unit 71 and the light-receiving unit 74 are box-shaped. The light-receiving unit 74 protrudes forward from the light-emitting unit 71. Also, the light-receiving unit 74 protrudes upward from the light-emitting unit 71.

[0052] Referring to Figures 5 to 7, the emission region 40, which is the area from which the emission unit 71 emits light, will be described. The emission unit 71 has a directional characteristic that concentrates and emits light into the emission region 40. The shape of the emission region 40 shown in Figures 5 to 7 is a trapezoidal shape, which is the shape projected onto a plane normal to the emission direction.

[0053] The emission unit 71 comprises an LD72 (see Figures 2 and 8) and a light-emitting lens 711 (see Figure 3). The emission unit 71 can concentrate light into the emission area 40 by refracting the light generated by the LD72 with the light-emitting lens 711. In other words, the emission unit 71 of this embodiment has trapezoidal directional characteristics due to the light-emitting lens 711.

[0054] In the following explanation, the lane in which the vehicle 2 is traveling is referred to as the driving lane 50. As shown in Figure 5, when viewed from the direction of emission from the laser distance meter 1 placed on the vehicle 2, the straight driving lane 50 becomes narrower in the left-right direction as it goes upwards. The right line 501 defining the driving lane 50 slopes to the left as it goes upwards, and the left line 502 slopes to the right as it goes upwards. The upper end 503 of the driving lane 50 is a plane parallel to the left-right direction. Thus, the driving lane 50 is roughly trapezoidal in shape. Therefore, when another vehicle 3 is at a distant position, the other vehicle 3 is located above (see Figure 5) and its left-right width is smaller. When the other vehicle 3 is closer than the distant position, the other vehicle 3 is located below and its left-right width is larger (see Figure 6).

[0055] The reflectors 95 are positioned on the left and right outer sides of the driving lane 50. The left and right outer sides of the driving lane 50 include the left and right ends and outer sides of the driving lane 50. The left and right ends of the driving lane 50 include lines 501 and 502. In this embodiment, as an example, the reflectors 95 are positioned on line 501 and line 502. The reflectors 95 may also be positioned to the right of line 501 and to the left of line 502 within the driving lane 50. For example, the reflectors 95 may be positioned on the curb of a sidewalk.

[0056] In the emission area 40, the part corresponding to the distant position is called the first part 401. In this embodiment, the first part 401 is the upper part of the emission area 40 and is the part for detecting the other vehicle 3 when it is at a distant position. Also, in the emission area 40, the part below the first part 401 is called the second part 402. The second part 402 is the part for detecting the other vehicle 3 when it is at a close position. The first part 401 has a smaller width in the left-right direction than the second part 402. In this embodiment, the second part 402 is the lower part of the emission area 40.

[0057] The emission area 40 is configured such that the width of the first part 401 for detecting other vehicles 3 at a distance is smaller in the left-right direction than the width of the second part 402 for detecting other vehicles 3 that are closer than the distance. Furthermore, the second part 402 is located below the first part 401. In this way, the emission area 40 is set to match the size of other vehicles 3 and the width of the driving lane 50 in the left-right direction. 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 reflector 95 on the outside of the driving lane 50 becomes smaller. Consequently, when detecting other vehicles 3 by detecting the light emitted from the laser distance meter 1, the possibility of false detection of the reflector 95 on the left-right outer side of the driving lane 50 is reduced. Thus, the detection accuracy of other vehicles 3 is improved.

[0058] Furthermore, in this embodiment, the shape of the ejection region 40 projected onto a plane normalized to the ejection direction is a trapezoidal shape with the first portion 401 at the top and the second portion 402 at the bottom. The right hypotenuse 403 in the ejection region 40 tilts to the left as it moves upward, and the left hypotenuse 404 tilts to the right as it moves upward. The hypotenuse 403 follows the right line 501 of the driving lane 50, and the hypotenuse 404 follows the left line 502 of the driving lane 50.

[0059] In Figure 7, the magnitude of brightness within the emission region 40 is shown by the intensity of the color. In the emission region 40, the brightness of the light from the first part 401 is greater than the brightness of the light from the second part 402. In this embodiment, the brightness gradually increases from the second part 402 towards the first part 401.

[0060] When the driving lane 50 is viewed from the laser distance meter 1 located on the vehicle 2, the driving lane 50 is trapezoidal in shape. Therefore, as shown in Figures 5 and 6, the reflectors 31 on other vehicles 3 often fall within the trapezoidal area where the light is concentrated. Consequently, compared to the case where the emission area 40 has a shape other than a trapezoid, the brightness of the light illuminating the reflectors 95 outside the driving lane 50 tends to be lower, and the brightness of the light illuminating the reflectors 31 on other vehicles 3 tends to be higher. Therefore, when detecting other vehicles 3 by detecting the light emitted from the laser distance meter 1, other vehicles 3 can be detected more reliably. In addition, since light is less likely to hit reflectors located in unnecessary areas such as the roadside, false detection of such reflectors can be prevented, and the detection distance of other vehicles 3 can be extended.

[0061] Furthermore, as shown in Figure 7, in the emission region 40, the brightness of the light from the first part 401 is greater than that of the light from the second part 402. Therefore, the light can travel further than when the brightness of the light from the first part 401 is less than or equal to that of the light from the second part 402. When another vehicle 3 is located in the first part 401, it is at a greater distance than when it is located in the second part 402 (see Figure 5). Since the brightness of the first part 401 is high for detecting other vehicles 3 at a distance, and the light can travel further, when detecting other vehicles 3 by detecting the light emitted from the laser distance meter 1, other vehicles 3 at a greater distance can be detected. In other words, in this embodiment, the light is concentrated and strongly irradiated in the distant direction where sensitivity is required, so the detection distance of other vehicles 3 can be efficiently increased. Therefore, the detection distance of other vehicles 3 can be extended.

[0062] The structure of the emission unit 71 will be described with reference to Figures 3, 4, 8, and 9. The emission unit 71 comprises a housing 712, an LD 72 (see Figures 2 and 8), and a projection lens 711. The housing 712 is substantially rectangular in shape. As shown in Figure 8, the housing 712 is provided with a recess 713 that curves inward from front to rear. The LD 72 is positioned at the rear end of the recess 713. The projection lens 711 is mounted on the front surface of the housing 712 (see Figure 9). When the LD 72 emits light, the light is refracted by the projection lens 711, and light is emitted into the emission area 40 (see Figures 5 to 7). In other words, the curved shape of the projection lens 711 enables trapezoidal directional characteristics, and furthermore, the brightness of the light at the top of the trapezoid can be increased.

[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 comprises a housing 742, a photodiode 75 (see Figures 2 and 8), and a light-receiving lens 76. The housing 742 is approximately rectangular and larger than the housing 712. As shown in Figure 8, the housing 742 is provided with a recess 743 that curves inward from the front to the rear. The photodiode 75 is positioned at the rear end of the recess 743. The photodiode 75 is supported by the housing 742.

[0064] As shown in Figures 3, 4, and 9, the light-receiving lens 76 is mounted on the front 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 the reflected light from the light emitted by the emission unit 71 to the photodiode 75.

[0065] The photodiode 75 receives reflected light from the light emitted by the emission unit 71. As shown in Figure 7, the incident region 750, into which the reflected light from the trapezoidal emission region 40 enters, tends to be trapezoidal, similar to the emission region 40. In Figure 7, the emission region 40 and the incident region 750 are shown superimposed. As shown in Figure 8, the upper part of the photodiode 75 has a shape that follows the upper part of the incident region 750 into which the reflected light from the emission region 40 (see Figures 5 and 7) enters. More specifically, the photodiode 75 is square, with one corner 751 located on the upper side. The sides 752 and 753 forming the corner 751 are inclined to follow the upper part of the incident region 750 into which the reflected light from the emission region 40 enters. In this embodiment, the photodiode 75, which is a square light-receiving element, is rotated 45 degrees and positioned.

[0066] As shown in Figure 9, the light-receiving lens 76 has multiple (three in this embodiment as an example) optical central axes 911-913. All of the multiple optical central axes 911-913 are located inside the photodiode 75. The structure of the light-receiving lens 76 will be described in detail below.

[0067] As shown in Figures 3 and 9, the light-receiving lens 76 comprises 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. The front surface 7611 of the main lens 761 protrudes forward, forming part of a sphere. The two auxiliary lenses 762 and 763 are arranged 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 of the auxiliary lenses 762 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 positioned on the lower right and lower left sides of the main lens 761. The auxiliary lenses 762 and 763 have the same shape as the parts of the main lens 761 adjacent to the auxiliary lenses 762 and 763. Note that "same shape" does not mean exactly the same shape, but also includes a shape that is close to the parts 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. The 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 is curved along the lower right end of the main lens 761. The lower end 762C of the auxiliary lens 762 is also curved in a front view. The front surface 762A of the auxiliary lens 762 is curved so that it is positioned further back from the upper surface 762B towards the lower end 762C.

[0070] The auxiliary lens 763 is connected to the lower left of the main lens 761 and has the same shape as the lower left of the main lens 761. The 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 curved along the lower left end of the main lens 761. The lower end 763C of the auxiliary lens 763 is also curved in a front view. The front surface 763A of the auxiliary lens 763 is curved so that it is positioned further back from the upper surface 763B towards the lower end 763C.

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

[0072] As described above, as a result of the formation of auxiliary lenses 762 and 763, the light-receiving region 89 that the photodiode 75 can receive light from becomes as shown in Figure 7. The light-receiving region 89 includes light-receiving regions 891 to 893. Light-receiving regions 891, 892, and 893 represent the regions where the main lens 761, auxiliary lens 762, and auxiliary lens 763 guide the reflected light from the light of the output region 40 to the photodiode 75, respectively. The shape of each light-receiving region 891 to 893 corresponds to the shape of the photodiode 75. The light-receiving region 891 by the main lens 761 corresponds to the upper part of the output region 40 and the incident region 750. The light-receiving region 892 by 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 by the auxiliary lens 763 is located to the lower left of the light-receiving region 891 of the main lens 761. In other words, compared to the case where only the main lens 761 is provided, the area in which the photodiode 75 can receive light is widened.

[0073] Furthermore, with only one ordinary circular spherical lens and a photodetector, the light-receiving area cannot cover the light-emitting area 40. For example, to widen the light-receiving area of ​​a single lens and photodetector, one could consider increasing the area of ​​the photodetector or shortening the focal length of the photodetector lens. Increasing the area of ​​the photodetector increases its capacitance, which can cause the signal waveform when light is received to become distorted and reduce the response speed. This may reduce the detection accuracy of other vehicles 3. Therefore, there are limits to how much the area of ​​the photodetector can be increased. Also, shortening the focal length of the photodetector lens reduces the area of ​​the lens, decreasing its light-gathering ability. This may reduce the detection accuracy of other vehicles 3. Therefore, there are limits to how much the focal length of the photodetector lens can be increased. In other words, the area of ​​the photodetector is limited by the size range of commercially available photodiodes, and there is a trade-off relationship between area size and response speed. Furthermore, shortening the focal length reduces the lens diameter (lens area) of the light-receiving lens, which also reduces its light-gathering ability.

[0074] In this embodiment, the light-receiving lens 76 has multiple optical central axes 911 to 913. Therefore, compared to the case of a lens with one optical central axis, the light-receiving area 89 that the photodiode 75 can receive is larger (see Figure 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 larger, other vehicles 3 located in a wider area can be detected, and the detection accuracy of other vehicles 3 is improved.

[0075] Furthermore, compared to the case with a single optical central axis, the light-receiving area 89 can be enlarged while suppressing the decrease in light-gathering ability due to the smaller size of the light-receiving lens 76. Because the light-receiving area 89 is enlarged, other vehicles 3 located in a wider area can be detected, improving the detection accuracy of other vehicles 3.

[0076] Furthermore, since the optical central axes 912 and 913 of the auxiliary lenses 762 and 763 are located below the optical central axis 911 of the main lens 761, more light from below 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 light from below can be made larger than when only the main lens 761 is provided.

[0077] Here, when viewed from the laser distance meter 1, the farther the distance from the laser distance meter 1 to the other vehicle 3, the higher the reflector 31 of the other vehicle 3 is located (see Figure 5), and the closer the distance from the laser distance meter 1 to the other vehicle 3, the lower the reflector 31 of the other vehicle 3 is located (see Figure 6). In this embodiment, by increasing the light-receiving area 89 that can receive light from below, the light-receiving area 89 that can receive light in the vertical direction becomes larger. Therefore, the range of distances at which the reflector 31 of the other vehicle 3 can be detected is increased compared to the case where only the main lens 761 is provided. Also, the light-receiving lens 76 does not become excessively large compared to the case where the light-receiving area 89 is increased with a single lens. Therefore, the possibility of the laser distance meter 1 becoming larger can be reduced.

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

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

[0080] The upper part of the photodiode 75 has a shape that follows the upper part of the incident region 750 into which reflected light from the emission region 40 (see Figures 5 and 7) is incident. Therefore, compared to a case where the photodiode 75 does not have a shape that follows the upper part of the emission region 40, the area of ​​the photodiode 75 that can be used to receive reflected light from the light emitted to the emission region 40 can be increased. Thus, it is possible to receive light from a wide range. Consequently, the laser inter-vehicle distance meter 1 can further improve the detection accuracy of other vehicles 3. For example, most of the light-receiving region 891 shown in Figure 7 overlaps with the incident region 750.

[0081] Furthermore, if a single photodiode 75 is used, the sensitivity will decrease if the area of ​​the photodiode 75's light-receiving surface that can be used to receive reflected light from the light emitted to the emission region 40 is small. However, as in this embodiment, the photodiode 75 is shaped to follow the upper part of the incident region 750, making it possible to increase the area that can be used to receive light from the light emitted to the emission region 40. Therefore, it is possible to receive light from a wider range. Thus, the sensitivity of the photodiode 75 is improved. Consequently, 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 one corner 751 of the rectangular photodiode 75 is located on the upper side, both sides 752 and 753 forming the upper corner 751 align with the upper part of the incident region 750 where reflected light from the trapezoidal emission region 40 is received. Compared to the case where the photodiode 75 is positioned so that the upper side of the rectangle is parallel to the left-right direction, the area of ​​the photodiode 75's light-receiving area that can be used to receive reflected light from the light emitted to the emission region 40 can be increased. Therefore, a wider range of light can be received. Consequently, the laser inter-vehicle distance meter 1 can further improve the detection accuracy of other vehicles 3 by using a rectangular photodiode 75. In addition, since there is no need to form the photodiode 75 in a shape other than a rectangle, costs can be reduced.

[0083] Note that the auxiliary lenses 762 and 763 are smaller in size than the main lens 761. In the incident region 750, in the portion that overlaps with the light-receiving region 891 of the main lens 761, the main lens 761 takes priority over the auxiliary lenses 762 and 763 in acquiring reflected light. When the other vehicle 3 is at a distance (see Figure 6), the gain tends to be small because it acquires reflected light from the reflector 31 of the other vehicle 3 at a distance, but because it is received by the larger main lens 761, the other vehicle 3 can be detected more reliably. Also, when the other vehicle 3 is at a close position (see Figure 6), the gain tends to be large because it acquires reflected light from the nearby other vehicle 3. For this reason, the reflected light is acquired by the smaller auxiliary lenses 762 and 763. In other words, in this embodiment, the portion detected by the auxiliary lenses 762 and 763 added to the main lens 761 does not require a large gain because the target other vehicle 3 is close, so the size of the auxiliary lenses 762 and 763 is reduced. Furthermore, by using the light-receiving lens 76 of this embodiment, wide-angle focusing can be achieved without reducing the lens diameter, which is proportional to the light-gathering area.

[0084] Referring to Figure 8, the internal structure of the housing 742 in the light-receiving unit 74 will be described. 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 that is recessed toward the rear is formed by the inner wall 77. The inner wall 77 is formed by two reflective surfaces 771, 772 and five anti-reflective surfaces 773 to 777.

[0085] The reflective surfaces 771 and 772 are formed, for example, by polishing the inner wall 77 of the housing 742. The reflective surfaces 771 and 772 reflect a portion of the light incident from the light-receiving lens 76 within the housing 742 and guide it to the photodiode 75. In this embodiment, the reflective surfaces 771 and 772 reflect at least the light that reaches above the photodiode 75 and guide it to the photodiode 75.

[0086] The low-reflectivity surfaces 773-777 are areas that are less likely to guide light to the photodiode 75 than the reflective surfaces 771 and 772. Of the low-reflectivity surfaces 773-777, the low-reflectivity surfaces 774-777 are located below the photodiode 75 within the housing 742.

[0087] A rectangular opening 78 is provided in the rear and central part of the inner wall 77 for arranging a photodiode 75. The photodiode 75 is rectangular, with one corner 751 located on the upper side. The opening 78 is formed so that one corner 781 is located on the upper side, in accordance with the arrangement of the photodiode 75.

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

[0089] The anti-reflective surface 774 extends downward from a pair of sides 755, 756 that form the lower corner 754 of the photodiode 75. The anti-reflective surface 775 extends diagonally to the front left from the left side of the anti-reflective surface 774. The upper end of the anti-reflective surface 775 is connected to the lower end of the reflective surface 771. The anti-reflective surface 776 extends diagonally to the front right from the right side of the anti-reflective surface 774. The upper end of the anti-reflective surface 776 is connected to the lower end of the reflective surface 772. The anti-reflective surface 777 extends diagonally downward from the bottom of the anti-reflective surface 774. The lower ends of the anti-reflective surfaces 774, 775, and 776 are connected to the anti-reflective surface 777.

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

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

[0092] Some of the reflected light from the area surrounding the first part 401 of the emission region 40 reaches below the photodiode 75 (see arrow 795). Below the photodiode 75, there are low-reflectivity surfaces 774-777, so light is less likely to be reflected there than from the reflective surfaces 771 and 772. Therefore, the reflected light is less likely to be guided to the photodiode 75. The driving lane 50 at the position where the light from the first part 401 of the laser distance meter 1 is emitted is narrow in the left-right direction, and the light is likely to illuminate the reflector 95 on the outside of the driving lane 50. However, because the low-reflectivity surfaces 774-774 make it difficult for the reflected light to be guided to the photodiode 75, the possibility of the laser distance meter 1 falsely detecting the reflector 95 can be further reduced.

[0093] Furthermore, the reflective surfaces 771 and 772 extend from the pair of sides 752 and 753 that form one corner 751 of the photodiode 75 (see Figure 8). As a result, compared to the case where the reflective surfaces 771 and 772 do not extend from the sides 752 and 753, the light reflected by the reflector 31 of the other vehicle 3 reaches the photodiode 75 more reliably. Thus, the detection accuracy of the other vehicle 3 is improved.

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

[0095] As described above, the light unit 7 in this embodiment is formed. The emission unit 71 can concentrate light into the emission area 40 by refracting light with the light projection lens 711. Therefore, it is not necessary to make the shape of the LD72 a special shape that emits light into the emission area 40. Thus, the cost of the LD72 can be reduced.

[0096] Furthermore, the emission unit 71 and the light-receiving lens 76 are positioned next to each other. Therefore, compared to the case where the emission unit 71 and the light-receiving lens 76 are far apart, the emission area 40 and the incident area 750 that receives light from the photodiode 75 are more likely to overlap. Thus, the detection accuracy of other vehicles 3 is improved.

[0097] Furthermore, as described above, the formation of the light unit 7 makes it possible to obtain light receiving directionality that matches the light projection directionality.

[0098] Furthermore, the light receiving unit 74 and the light emitting unit 71 are adjacent to each other in the left-right direction. Therefore, the vertical length of the light unit 7 can be shortened compared to when they are adjacent to each other in the vertical direction. As a result, when the laser distance meter 1 is mounted on the upper part of the windshield 91, as shown in Figure 1, it is less likely to be in the driver's field of vision.

[0099] The equivalent sampling method in this embodiment will be described with reference to Figures 11 and 12. In this embodiment, the equivalent time sampling method (sequential sampling) is used when the laser distance meter 1 calculates the distance from the laser distance meter 1 to another vehicle 3. The equivalent time sampling method is used to convert the ultrafast received pulse waveform (repeating waveform) to a time axis order that can be captured by a low-rate AD converter and processed. The equivalent time sampling method is a technique that repeatedly samples by slightly shifting the starting point of sampling, thereby downconverting many sample points onto the waveform.

[0100] The CPU 101 causes the LD 72 to light up, thereby emitting light to the emission unit 71. The CPU 101 also samples the signal based on the light received by the LD 72 at a sampling interval using the equivalent time sampling method. However, because the frequency of light is high, a very high sampling frequency is required, which can lead to problems such as high component costs. Therefore, in this embodiment, sampling is performed using the equivalent sampling method.

[0101] The closer the laser distance meter 1 is to the other vehicle 3, the shorter the time it takes for light to be emitted from the emission unit 71 and for the reflected light from the reflector 31 of the other vehicle 3 to reach the laser distance meter 1. In other words, the time it takes for light to be emitted from the emission unit 71 and for the reflected light from the reflector 31 of the other vehicle 3 to reach the laser distance meter 1 changes depending on the distance between the laser distance meter 1 and the other vehicle 3. Therefore, the CPU 101 controls the emission unit 71 to change the time from when it emits light until it performs sampling, thereby detecting other vehicles 3 from close by to when they are far away.

[0102] In this embodiment, the CPU 101 controls the emission unit 71 to emit light and changes the brightness of the emitted light according to the time from when it emits light until sampling is performed. More specifically, in this embodiment, as shown in Figure 12, the shorter the time from when the CPU 101 controls the emission unit 71 to emit light and sampling is performed, the weaker the brightness of the light emitted by the emission unit 71. 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. Therefore, the closer the distance, the larger the received light signal level at that sampling timing, so the pulse light level of the LD72 is controlled in proportion to the distance.

[0103] Figures 11 and 12 will be explained below. In the following explanation, the pulsed light emitted from the laser distance meter 1 may be referred to as pulsed light. Figures 11(A) and (B) show the luminance of the pulsed light emitted from the laser distance meter 1 and the magnitude of the luminance of the reflected light when the luminance is kept constant regardless of the time from when the emission unit 71 is controlled to emit light until sampling is performed. Figures 12(A) and (B) show the luminance of the pulsed light and the magnitude of the luminance of the reflected light when the luminance of the emitted light is changed according to the time from when the emission unit 71 is controlled to emit light until sampling is performed.

[0104] In Figures 11(A) and 12(A), the vertical axis 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 distance meter 1 attempts to detect. In Figures 11(B) and 12(B), the vertical axis 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 distance meter 1 attempts to detect. The further to the right on the horizontal axis, the longer the distance L between the laser distance meter 1 and the other vehicle 3. In the following explanation, the pulsed light emitted by the emission unit 71 may be referred to as pulsed light Pa (a=1~n). The pulsed light used to detect the other vehicle 3 with the smallest distance L is defined as pulsed light P1, and the pulsed light used to detect the other vehicle 3 with the largest distance L is defined as pulsed light Pn. The laser distance meter 1 repeatedly emits pulsed light from P1 to Pn.

[0105] The number of pulses from pulse light P1 to pulse light Pn is, for example, 4096 (i.e., n=4096), but in Figures 11 and 12, the number of pulses is shown as a smaller number. The duration of emission of one pulse is, for example, 20-29 nS. The time between the emission of one pulse and the emission of the next pulse is, for example, 57 μS. (The diagram is a conceptual diagram and shows the 57 μS interval as a short interval, but in reality, the time is 57 μS, which is more than 1000 times longer than 20-29 nS.) Also, the interval from the emission of pulse light from the emission unit 71 to the sampling of reflected light increases from pulse light P1 to pulse light Pn. That is, regarding the interval from the emission of pulse light Pa from the emission unit 71 to the sampling of reflected light, the further to the left you move on the horizontal axis, the shorter the interval until sampling becomes.

[0106] In the example shown in Figure 11(A), the brightness of the pulsed light Pa emitted from the emission unit 71 is constant regardless of the distance L (for example, constant at 16W from pulsed light P1 to pulsed light Pn). For example, when another vehicle 3 is at position PL1, the light is reflected by the reflector 31 of the other vehicle 3, so the brightness of the reflected light received by the light receiving unit 74 becomes large, as shown at point P11. Also, when the other vehicle 3 is at PL2, which is further away than position PL1, the light is reflected by the reflector 31 of the other vehicle 3, so the brightness of the reflected light received by the light receiving unit 74 becomes large, as shown at point P12.

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

[0108] Referring to Figure 12, the control of the brightness of pulsed light Pa in a case where the brightness of the emitted light is changed according to the time from when the emission unit 71 is controlled to emit pulsed light Pa until sampling is performed will be explained. As shown in Figure 12(A), the brightness of pulsed light Pa emitted from the emission unit 71 decreases as the distance L decreases (for example, if pulsed light Pn is 16W, pulsed light P1 is 1 / 4 of that, or 4W). In other words, the CPU 101 causes the emission unit 71 to emit pulsed light Pa with lower brightness the shorter the time from when the emission unit 71 is controlled to emit light until sampling is performed.

[0109] In this case, for example, if other vehicle 3 is at position PL1, the light is reflected by the reflector 31 of other vehicle 3, so the brightness of the reflected light received by the light receiving unit 74 becomes large, as shown at point P21. Also, if other vehicle 3 is at PL2, which is further away than position PL1, the light is reflected by the reflector 31 of other vehicle 3, so the brightness of the reflected light received by the light receiving unit 74 becomes large, as shown at point P22.

[0110] When another vehicle 3 is nearby, the brightness increases when the reflected light from the reflector 31 of the other vehicle 3 is received by the light receiving unit 74. However, the brightness of the pulsed light Pa emitted from the emission unit 71 decreases as the distance L decreases, so the difference D2 between the brightness of point P21 and the brightness of point P22 becomes smaller than the difference D1 between the brightness of point P11 and the brightness of point P12 shown in Figure 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 closer the distance L from the laser distance meter 1 to the other vehicle 3, the greater the brightness of the reflected light received by the light receiving unit 74 tends to be (see Figure 11(B)). Also, for example, depending on the characteristics of the light-emitting lens 711 or 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 distance meter 1 to the other vehicle 3 is within a predetermined range. When the brightness of the reflected light received by the photodiode 75 increases, the amplifier circuit may saturate when the signal based on the reflected light received by the photodiode 75 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, and the detection accuracy of the other vehicle 3 may decrease. For example, the amplifier circuit may saturate at point P11 shown in Figure 11(B).

[0112] In the equivalent time sampling method, the time from when pulsed light Pa is emitted from the emission unit 71 until it is sampled by the CPU 101 changes depending on the distance to the other vehicle 3. In this embodiment, the brightness of the emitted pulsed light Pa changes depending on the time from when pulsed light Pa is emitted from the emission unit 71 until it is sampled (see Figure 12). For this reason, for example, in the range where the amplifier circuit may saturate, the brightness of the light emitted from the emission unit 71 can be reduced. Thus, the possibility of the amplifier circuit saturating is reduced. As a result, the detection accuracy of the other vehicle 3 is improved compared to the case where the amplifier circuit saturates and a long recovery time occurs. Also, even if saturation occurs, the recovery time can be shortened. Furthermore, power consumption is reduced compared to the case where the brightness of the pulsed light Pa does not change and light is always emitted at a brightness sufficient to detect the other vehicle 3 at a distance (see Figure 11). In addition, since the brightness of individual pulsed light Pa and the average light output of pulsed light Pa are reduced, the level of light reflected by the windshield 91 can be reduced.

[0113] The laser distance meter 1 emits light of the necessary intensity to reach the furthest point within the range of distance for detecting other vehicles 3. Therefore, the intensity of the light may be high. Furthermore, if the laser distance meter 1 is installed inside a vehicle, for example, it is necessary to transmit the light through the windshield 91, etc., which may further increase the intensity of the light. When continuously emitting high-intensity light, it is necessary to consider the impact on the human eye. Therefore, in this embodiment, instead of continuously emitting light, pulsed light Pa is emitted, and periods of no light emission are provided to reduce the average value of the light intensity. This reduces the impact on the human eye. For example, the interval between pulsed light Pa should be twice as large as the pulse width. More preferably, the interval between pulsed light Pa should be 1000 times or more large than the pulse width.

[0114] Furthermore, in this embodiment, the shorter the time between the emission of pulsed light Pa and its sampling by the CPU 101, the weaker the pulsed light Pa emitted from the emission unit 71 (see Figure 12). Therefore, compared to the case where the brightness of the pulsed light Pa is not adjusted (see Figure 11), the brightness of the reflected light received when the distance from the laser distance meter 1 to the other vehicle 3 is short can be reduced (see Figure 12). Thus, the possibility of the amplifier circuit becoming saturated can be reduced, and the detection accuracy of the other vehicle 3 can be improved.

[0115] Thus, when monitoring other vehicles 3 at a distance, the pulsed light Pa is output at the highest possible level to obtain sensitivity, while when monitoring other vehicles 3 at a close distance, the pulsed light Pa is output at a small level to prevent the amplifier circuit from saturating at an unnecessarily high level.

[0116] Referring to Figure 13, the electrical configuration for emitting the pulsed light Pa shown in Figure 12(A) will be described. At least a portion of the emission control circuit 60 shown in Figure 13 is included in the light-emitting circuit 102 (see Figure 2). As shown in Figure 13, the emission control circuit 60 comprises a power supply circuit 61, a fourth resistor 651, and a switch 68. The power supply circuit 61 supplies voltage to the LD72 of the emission unit 71. The power supply circuit 61 includes a DC / DC converter 63, a divider 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 LD72. The DC / DC converter 63 includes an input terminal 631, an output terminal 632, and a reference input terminal 633, etc.

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

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

[0119] The output terminal 632 of the DC / DC converter 63 is electrically connected to terminal 651A of the fourth resistor 651. Terminal 651B of the fourth resistor 651 is electrically connected to the anode terminal 721 of LD72. The cathode terminal 722 of LD72 is connected to a switch 68, which is composed of a transistor or the like. The switch 68 is electrically connected to ground. The switch 68 is turned on and off by the control of the CPU 101 or by the output signal of the oscillator.

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

[0121] When the voltage of waveform S2 is input to the reference input terminal 633, the voltage output from the output terminal 632 of the DC / DC converter 63 fluctuates as shown in waveform S3. Waveform S3 is a waveform in which the voltage rises in section 671, becomes constant in section 672, and decreases over time in section 673, and this change is repeated. In other words, the divided voltage from the divider resistor 62 is forcibly fluctuated by the integrating circuit 64 and the third resistor 614, causing the voltage applied to the reference input terminal 633 to fluctuate and creating waveform S3. In this way, waveform S3 is created by inputting waveform S2, which is a ramp signal generated by the integrating circuit 64, to the reference input terminal 633 of the DC / DC converter 63, which is the high-voltage DC / DC circuit for the power supply of the LD72.

[0122] Waveform S3 is applied to LD72. While the voltage of portion 673 of waveform S3 is applied to LD72, the switch 68 is repeatedly switched on and off, and the pulsed light Pa shown in Figure 12(A) is output. That is, the shorter the time from when the laser distance meter 1 emits the pulsed light Pa until it is sampled by the equivalent time sampling means, the weaker the light that is emitted.

[0123] Thus, in this embodiment, by varying the voltage input to the reference input terminal 633 with the output from the integrating circuit 64, it is possible to realize a function in which the pulsed light Pa emitted by the emission unit 71 has a weaker brightness, as the time from emission of the pulsed light Pa to sampling by the CPU 101 becomes shorter.

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

[0125] As shown in Figure 14, the light receiving control circuit 80 includes a low-pass filter (LPF) 81, sample-and-hold circuits (S&H) 821 and S&H 822, a differential amplifier 83, and an A / D converter 84. The light received signal from the photodiode is input to the LPF 81 and 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] S&H821 is a circuit that acquires the signal received by the photodiode 75 before the pulsed light Pa (see Figures 11 and 12) is emitted by the LD72. A pre-sampling pulse is input to S&H821. The pre-sampling pulse is set to an interval that allows S&H821 to acquire the signal received by the photodiode 75 before the pulsed light Pa is emitted by the LD72. The interval between each pulse in the pre-sampling pulse is constant. The LPF81 allows a frequency band lower than the pulsed light Pa emitted by the LD72 to pass through the signal received by the photodiode 75. Therefore, S&H821 acquires the signal after it has passed through the LPF81.

[0127] S&H822 is a circuit that acquires the signal obtained by the photodiode 75 at a sampling interval based on the equivalent sampling method, after the pulsed light Pa is emitted by LD72. An equivalent time sampling pulse is input to S&H822. The equivalent time sampling pulse is set to an interval at which S&H821 acquires the signal based on the reflected light obtained by the photodiode 75 at a sampling interval based on the equivalent sampling method, after the pulsed light Pa is emitted by LD72.

[0128] The differential amplifier 83 acquires a signal based on the difference between the signal acquired by S&H821 and the signal acquired by S&H822, 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] Referring to Figure 15, the signal processing by the light receiving control circuit 80 will be explained. Waveform 991 in Figure 15(A) represents the signal level based on luminance when the reflector 31 of the other vehicle 3 is at position PL3 and only the reflected light from the reflector 31 of the other vehicle 3 is received by the photodiode 75, with the value increasing around position PL3. Waveform 992 represents the signal level when various noises such as circuit noise, external electrical noise, and external optical noise are added in addition to waveform 991. Since various noises are added to waveform 992, the value is larger than waveform 991 by magnitude E1.

[0130] Figure 15(B) shows the timing at which the pre-sampling pulse PPb (b=1~n) and the equivalent-time sampling pulse SPc (c=1~n) are input. S&H821 acquires the signal obtained by photodiode 75 at the timing when the pre-sampling pulse PPb is input. S&H822 acquires the signal obtained by photodiode 75 at the timing when the equivalent-time sampling pulse SPc (c=1~n) is input.

[0131] Each pre-sampling pulse PPb is input to the S&H821 before the pulsed light Pa (a=1~n) shown in Figures 11 and 12 is emitted. For example, the first pre-sampling pulse PP1 is input to the S&H821 before the pulsed light P1 (see Figures 11 and 12) is emitted. The second pre-sampling pulse PP2 is input to the S&H821 after the pulsed light P1 is emitted but before the pulsed light P2 (see Figures 11 and 12) is emitted.

[0132] Each pre-sampling pulse PPb is input to the S&H821 before the pulse light Pa shown in Figures 11 and 12 is emitted, so the reflected light of the pulse light Pa is not received by the photodiode 75. Therefore, a signal of magnitude E1 is acquired by the S&H821. In other words, a signal based on various types of noise, such as circuit noise, external electrical noise, and external optical noise, is acquired. Furthermore, since the LPF81 is provided, even if the reflected light of the pulse 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~N) is input to the S&H822 at the timing when the reflected light is received after the pulse light Pa shown in Figures 11 and 12 has been emitted. That is, it is input to the S&H822 at the sampling interval determined by the equivalent time sampling method. As you move towards SP1, SP2...SPn, the timing of the equivalent time sampling pulse SPc being input to the S&H822 after the pulse light Pa has been emitted becomes later. Therefore, the further the distance L to other vehicles 3 is, the later the timing of the reflected light of the pulse light Pa being received. In other words, by delaying the timing of the input of the equivalent time sampling pulse SPc to the S&H822, it is possible to receive reflected light corresponding to the distance L. For example, the signal at point P31, where the value of waveform 992 is largest, is acquired by the S&H822 when the equivalent time sampling pulse SPm+2 is input to the S&H822.

[0134] The difference between the signal based on brightness, etc., when the pre-sampling pulse PPb is input to the S&H821 and the signal based on brightness, etc., when the equivalent-time sampling pulse SPc is input to the S&H821 is amplified by the differential amplifier 83. The amplified signal is encoded 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 brightness, etc., when the pre-sampling pulse PP1 is input to S&H821 and the signal based on brightness, etc., when the equivalent-time sampling pulse SP1 is input to S&H821 is amplified by the differential amplifier 83. The signal based on brightness, etc., when the pre-sampling pulse PP1 is input to S&H821 and the signal based on brightness, etc., when the equivalent-time sampling pulse SP1 is input to S&H821 are noise components (signals of magnitude E1) that do not contain reflected light from the reflector 31 of the other vehicle 3. Therefore, the noise components cancel each other out, and the output from the differential amplifier 83 approaches 0 compared to the case where they do not cancel each other out.

[0136] When the m+2th measurement is performed, the difference between the signal based on brightness, etc. when the pre-sampling pulse PPm+2 is input to S&H821 and the signal based on brightness, etc. when the equivalent time sampling pulse SPm+2 is input to S&H821 is amplified by the differential amplifier 83. The signal based on brightness, etc. when the pre-sampling pulse PPm+2 is input to S&H821 is a noise component (a signal with magnitude E1). The signal based on brightness, etc. when the equivalent time sampling pulse SPm+2 is input to S&H821 is a signal that includes the noise component and the reflected light from the reflector 31 of another vehicle 3 (a signal with magnitude E2). Therefore, the noise component, which is the signal based on brightness, etc. when the pre-sampling pulse PPm+2 is input to S&H821, is removed from the signal based on brightness, etc. when the equivalent time sampling pulse SPm+2 is input to S&H821. Thus, the signal with reduced noise is encoded and input to the CPU 101. In other words, a signal of magnitude E3 is amplified, encoded, and input to the CPU 101.

[0137] The CPU 101 obtains the distance to the other vehicle 3 based on the input signal. Specifically, the CPU 101 can obtain the distance to the other vehicle 3 based on the pulsed light Pa received by the photodiode 75.

[0138] As mentioned 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. Since the signal level of the reflected light is very small, if the signal-to-noise ratio (S / N ratio) decreases due to the influence of noise, it can lead to a decrease in sensitivity (reduction in the maximum detection distance), and the distance at which other vehicles 3 can be detected may become shorter. One way to improve the S / N ratio is to use a bandpass filter (BPF), but since the signal waveform of the reflected light is a square wave, if the bandwidth of the BPF is made too narrow, the waveform of the reflected light signal may become distorted. This can lead to a decrease in sensitivity, and the distance at which other vehicles 3 can be detected may become shorter. Therefore, in this embodiment, a signal synchronized with the noise is generated and subtracted from the equivalent time sampling output signal to reduce the influence of noise without distorting the waveform. Details are described below.

[0139] In this embodiment, a signal is acquired and encoded based on the difference between a signal acquired before the pulse light Pa is emitted (a signal acquired at the timing of the pre-sampling pulse PPb) and a signal acquired at the sampling interval using the equivalent sampling method (a signal acquired at the timing of the equivalent time sampling pulse SPc). The signal acquired by S&H821 is a signal that does not contain reflected light and is a noise signal. The signal acquired by S&H822 is a signal that contains both reflected light and noise. Since a signal is acquired and encoded based on the difference between the signal containing reflected light and noise and the noise signal, the signal-to-noise ratio can be improved. In addition, since a band-pass filter is not used, the waveform of the reflected light is less likely to be distorted. Therefore, the possibility of sensitivity degradation is reduced, and the distance at which other vehicles 3 can be detected is increased.

[0140] Furthermore, if a signal containing noise in the same frequency band as the light emitted by LD72 is acquired by S&H821, there is a possibility that the differential amplifier 83 may superimpose noise fluctuating in the same frequency band as the light onto the light signal.

[0141] In this embodiment, the LPF81 reduces noise in the same frequency band as light, and this noise is acquired by the S&H821. Therefore, the differential amplifier 83 reduces the possibility that noise fluctuating in the same frequency band as light will be superimposed on the light signal. Consequently, the possibility of sensitivity degradation is reduced, and the distance over which other vehicles 3 can be detected is increased.

[0142] Thus, as a means of attenuating noise below the desired signal bandwidth, in addition to the frequency discrimination BPF, two sets of sampling circuits (S&H821 and S&H822) are provided in the equivalent time sampling section. One provides a sampling pulse (pre-sampling pulse PPb) at a fixed timing immediately before the LD72 emits light, while the other provides it at the timing of normal equivalent time sampling. By subtracting the output of the former sampling circuit from the output of the latter sampling circuit using a differential circuit (differential amplifier 83), the lower (lower frequency) noise components are strongly attenuated. Furthermore, the received signal input to the pre-sampling is passed through an LPF 81 to reduce noise.

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

[0144] In this embodiment, two output voltages with different periods from integrating circuits 851 and 852 are input to comparator 853 to sweep the rising and falling timings and generate an equivalent time sampling pulse SPc.

[0145] The integrating circuit 851 receives the voltage of waveform 55. Waveform 55 is a repeating square wave. The integrating circuit 852 receives the voltage of waveform 56. 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 the integrating circuit 851, waveform 57 is output. Waveform 57 is a waveform in which the voltage rises in section 571 and gradually decreases in section 572. When waveform 56 is input to the integrating circuit 852, waveform 58 is output. Waveform 58 is a waveform in which the voltage rises in section 581, becomes constant in section 582, and gradually decreases in section 583.

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

[0148] As described above, in this embodiment, an equivalent time sampling pulse SPc is generated. The equivalent time sampling method allows for downconversion of a received light pulse waveform on the order of a few nS to tens of nS at any magnification. Therefore, high speed is less required for the signal processing circuit after receiving the light.

[0149] In the above embodiment, the laser inter-vehicle distance meter 1 is an example of the "emitting device" of the present invention. The photodiode 75 is an example of the "receiving unit" of the present invention. The reflective surfaces 771 and 772 are examples of the "reflecting unit" of the present invention. The low-reflectivity surfaces 774 to 777 are examples of the "low-reflectivity unit" of the present invention. The emission control circuit 60 is an example of the "emission control means" of the present invention. The light receiving control circuit 80 is an example of the "equivalent time sampling means" of the present invention. S&H821 is an example of the "first acquisition means" of the present invention. S&H822 is an example of the "second acquisition means" of the present invention. The differential amplifier 83 is an example of the "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 the "distance acquisition means" of the present invention.

[0150] It should be noted that the present invention is not limited to the above embodiments and can be modified in various ways. For example, although the emission area 40 was trapezoidal, it is not limited to this. Preferably, the emission area 40 has a shape in which at least one of a pair of opposing sides in the left-right direction is inclined inward as it goes upward. In this case, the brightness of the light irradiated onto the reflector 95 on at least one side in the left-right direction of the driving lane 50 tends to be reduced. Therefore, when detecting other vehicles 3 by detecting the light emitted from the laser distance meter 1, the possibility of falsely detecting the reflector 95 on the outside of the driving lane 50 is reduced. Thus, the detection accuracy of other vehicles 3 is improved. For example, as shown in Figure 17, if only the right side 413 is inclined to the left as it goes upward, the possibility of falsely detecting the reflector 95 on the right side is reduced.

[0151] Incidentally, the emission area 40 is preferably a triangle in shape that can eliminate the influence of the reflectors 95 on the left and right outer sides of the driving lane 50. However, since the upper vertex of the triangle is a point, if the vehicle 2 is shifted to the left or right from the center of the driving lane 50, there is a high possibility that the other vehicle 3 will not be detected. Therefore, in order to ensure more reliable detection even when the vehicle 2 is shifted to the left or right from the center of the driving lane, an upper side 405 is provided, as shown in Figures 5 to 7, making the emission area 40 a trapezoid. The length of the upper side 405 of the trapezoidal emission area 40 is preferably, for example, the length corresponding to the driving lane 50 at the detection target distance of the other vehicle 3.

[0152] Furthermore, as in this embodiment, the emission region 40 is preferably continuous from the upper first portion 401 to the lower second portion 402. Also, the emission region 40 is preferably divided between the first portion 401 and the second portion 402. In addition, the light generation unit is an LED (Light It is preferable that the generating unit be an Emitting Diode. The generating unit is particularly preferable to be an LD72 as in this embodiment. The LD72 can transmit light through the windshield 91 and reach other vehicles 3 at a greater distance, even when the laser distance meter 1 is mounted on the inside of the windshield 91.

[0153] Furthermore, the emission area 40 is preferably triangular or quadrilateral, with both sides of a pair facing each other in the left-right direction inclined inward 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 tends to decrease. Therefore, when detecting other vehicles 3 by detecting the light emitted from the laser distance meter 1, the possibility of false detection of the reflectors 95 on the outside of the driving lane 50 is reduced. Thus, the detection accuracy of other vehicles 3 is improved. In this embodiment, the emission area 40 is quadrilateral, with a pair of hypotenuses 403 and 404 facing each other in the left-right direction inclined inward as they extend upward.

[0154] Furthermore, it is desirable that the hypotenuses 403 and 404 located on the left and right sides of the trapezoidal emission area 40 be nearly parallel to the left and right lines 501 and 502 of the driving lane 50 as seen from the laser distance meter 1. For example, if the angle R1 (see Figure 5) between the hypotenuses 403 and 404 located on the left and right sides of the trapezoidal emission area 40 and the base 406 is 45 degrees, it is desirable to set the angle R2 (see Figure 5) between the left and right lines of the driving lane 50 as seen from the laser distance meter 1 and the left and right direction to be 45 degrees. In this case, the brightness of the light illuminating the reflector 95 on the outside of the driving lane 50 tends to be low, and the brightness of the light illuminating 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 distance meter 1, the other vehicle 3 can be detected more reliably.

[0155] Furthermore, it is preferable that the slanted edges 403 and 404 located on the left and right sides of the trapezoidal emission area 40 are slightly outside the left and right lines 501 and 502 of the driving lane 50 as seen from the laser distance meter 1. In this case, it is preferable that light is less likely to irradiate the reflectors located outside the left and right lines 501 and 502. Preferably, the slanted edges 403 and 404 located on the left and right sides of the trapezoidal emission area 40 are in the same position as the left and right lines 501 and 502 of the driving lane 50 as seen from the laser distance meter 1. Even more preferably, the slanted edges 403 and 404 located on the left and right sides of the trapezoidal emission area 40 are inside the left and right lines 501 and 502 of the driving lane 50 as seen from the laser distance meter 1. Also, it is preferable that the emission area 40 be sized to match a road with a relatively wide width in the lateral direction, such as a main road. On roads that are wide from side to side, vehicles tend to travel at higher speeds, making the distance between vehicles 3 crucial for driving safety. The use of a laser distance meter 1 on such roads, where speeds tend to be higher, improves driving safety.

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

[0157] Furthermore, it is preferable that the optical central axes 912 and 913 of the auxiliary lenses 762 and 763 are located below the optical central axis 911 of the main lens 761. Because the auxiliary lenses 762 and 763 are provided, more light from below 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 light from below is larger than when only the main lens 761 is provided.

[0158] Furthermore, although the explanation used the laser distance meter 1 as an example, it is preferable that the device cannot measure the distance between vehicles. For example, the emission device of the present invention may be a device that can only detect the presence or absence of other vehicles 3, rather than the laser distance meter 1. Also, it is preferable that the emission device of the present invention is a device that can emit light and cannot receive reflected light. In this case, it is preferable that the reflected light is received by another device and other vehicles 3 are detected.

[0159] Furthermore, it is preferable that the LPF81 (see Figure 6) is not provided. If the LPF81 is not provided, costs can be reduced. Also, the light receiving control circuit 80 may have a configuration other than the example shown in Figure 14. Furthermore, the circuit configuration for emitting light may have a configuration other than the example shown in Figure 13. In addition, the first resistor 621, the second resistor 622, and the third resistor 614 are not limited to a single resistor each, but may be a combination of multiple resistors.

[0160] Furthermore, although the reflective surfaces 771 and 772 shown in Figure 8 were formed by polishing the inner wall 77 of the housing 742, they may be formed by means other than polishing. For example, the reflective surfaces 771 and 772 may be formed by metal plate, plating, or polishing. Also, it may be desirable for the non-reflective surface 773 to be a reflective surface. Also, it may be desirable not to provide the non-reflective surfaces 773 to 777. Also, it may be desirable not to provide the reflective surfaces 771 and 772. If the reflective surfaces 771 and 772 are not provided, the cost of forming the reflective surfaces 771 and 772 can be reduced.

[0161] Furthermore, the photodiode 75 should be arranged in a configuration other than one where one corner 751 is located on the upper side. Also, the photodiode 75 should not be rectangular. In addition, a light-receiving element other than the photodiode 75 should be used. For example, a CCD should be used.

[0162] Furthermore, the shapes of the auxiliary lenses 762 and 763 may differ from those of this embodiment. Also, the number of auxiliary lenses is not limited. It is preferable to have one auxiliary lens. It is preferable to have three or more auxiliary lenses. Also, the position of the auxiliary lenses is not limited. For example, the position of the auxiliary lenses may be changed according to the shape of the emission area 40. Also, the shapes of the auxiliary lenses 762 and 763 may differ from those of this embodiment. Also, it is preferable that auxiliary lenses 762 and 763 are not provided. Also, the shape of the main lens 761 does not have to be circular. It is preferable that at least a portion of the optical central axes 911 to 913 of the light-receiving lens 76 be located outside the photodiode 75.

[0163] Furthermore, it is preferable that the emission unit 71 and the light receiving unit 74 be adjacent to each other in the vertical direction. In this case, the width of the laser inter-vehicle distance meter 1 in the horizontal direction can be reduced. Also, it is preferable that the emission unit 71 and the light receiving unit 74 be spaced apart from each other.

[0164] Furthermore, the location where the laser distance meter 1 is mounted is not limited. For example, the laser distance meter 1 may be mounted on the rear window of the vehicle 2. Also, the direction of light emission may be towards the rear. In addition, the laser distance meter 1 may be placed outside the vehicle 2. For example, the laser distance meter 1 may be placed at the front or rear end outside the vehicle 2. Also, the mounting part 19 may not be provided. In this case, costs can be reduced.

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

[0166] The CPU 101 (see Figure 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 (e.g., PCs and mobile terminals) via a miniUSB connector. Aiming sights 124 are provided at the lower ends of the front 111 and rear 112, arranged in the front-to-back direction. A slit is provided at the lower end of each aiming sight 124. The aiming sights 124 are used when adjusting the orientation of the laser distance meter 1. The user visually observes the slit of the aiming sight 124 from the rear and adjusts the orientation of the laser distance meter 1 by aligning the slits of the aiming sights 124 positioned front to back.

[0167] The CPU 101 performs the control shown in Tables 961-964 (see Figures 19-22) based on the data stored in ROM 106. Based on the distance to the other vehicle 3 measured by the optical unit 7, the CPU 101 outputs the audio shown in Table 961 (see Figure 19) from the speaker 105. As shown in Table 961, the audio output by the CPU 101 controlling the speaker 105 can be selected from, for example, Voice 1 (announcer-like), Voice 2 (anime voice), and a buzzer sound. If a collision is imminent in X seconds, the CPU 101 outputs a collision warning from the speaker 105 to notify the user. Also, for example, if the vehicle approaches the other vehicle 3 further from the position where the collision warning is issued, the CPU 101 outputs a collision warning from the speaker 105 to notify the user. Collision warnings differ depending on whether the vehicle is moving at low speed or high speed (see "Collision Warning (Low Speed)" and "Collision Warning (High Speed)" in Table 961). Also, if vehicle 2 is stopped and another vehicle 3 ahead starts moving, the CPU 101 outputs start information from speaker 105 to inform the user.

[0168] When set to Voice 1 (announcer style), CPU 101 outputs the collision warning "Ah," the collision warning (low speed) "It's dangerous," the collision warning (high speed) "Watch out," and the start information "The vehicle in front is starting." When set to Voice 2 (anime voice), CPU 101 outputs the collision warning "Ah," the collision warning (low speed) "Be careful," the collision warning (high speed) "Watch out!", and the start information "Go!" When set to buzzer sound, CPU 101 outputs the collision warning "Beep beep," the collision warning (low speed) "Beep beep beep," the collision warning (high speed) "Beep beep beep," and the start information "Pu-pu-pu-pu."

[0169] When the UP key 122 or DOWN key 123 is pressed and held, the CPU 101 sets the sensitivity as shown in Table 962 (Figure 20). The sensitivity 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 to 3. When the DOWN key 123 is pressed and held, the CPU 101 decreases the sensitivity setting from 3 to 0. A sensitivity setting of "0" is the "no detection" setting. When the CPU 101 is set to sensitivity "0", it does not detect other vehicle 3. Also, the sensitivity increases as the sensitivity setting increases from 1 to 3. In other words, the CPU 101 makes it easier to detect other vehicle 3.

[0170] The CPU 101 can set the state of the laser distance meter 1 to one of the following modes shown in Table 963 (see Figure 21): "S1. Operation Mode," "S2. Glass Correction Mode," and "S3. Detection Confirmation Mode." Operation Mode is the mode for normal operation. Glass Correction Mode is a mode that reduces the influence of the windshield 91.

[0171] Let's explain the glass correction mode in more detail. A portion of the light emitted from LD72 and reaching the windshield 91 is reflected by the windshield 91 and then reflected back towards the photodiode 75. For example, if we consider the light emitted from LD72 and reaching the windshield 91 as 100%, then 95% passes through the windshield 91 and is emitted forward. Then, 2-3% of the light is reflected by the windshield 91 and reaches the photodiode 75.

[0172] On the other hand, some 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. Since the reflector 31 is located in only a part of the light's illumination range, less than 1% of the light is reflected by the reflector 31 and reaches the photodiode 75. In other words, the amount of light that reaches the photodiode 75 after being reflected by the reflector 31 (less than 1%) is small compared to the amount of light that reaches the photodiode 75 after being reflected by the windshield 91 (2-3%). Therefore, the influence of the light that reaches the photodiode 75 after being reflected by the windshield 91 is significant. The glass correction mode is implemented to reduce the influence of the light that reaches the photodiode 75 after being reflected by the windshield 91.

[0173] Specifically, in glass correction mode, light is emitted from LD72 when there is no other vehicle 3 in front. Since there is no other vehicle 3 in front, the light is not reflected by the reflector 31. Therefore, the CPU 101 can obtain the brightness of the light that is reflected by the windshield 91 and reaches the photodiode 75. In glass correction mode, the CPU 101 stores the brightness of the light that is reflected by the windshield 91 and reaches the photodiode 75 in RAM 107 or another storage medium. When the CPU 101 detects another vehicle 3 in operation mode, it subtracts the brightness of the light that was stored in glass correction mode, which is reflected by the windshield 91 and reaches the photodiode 75, from the brightness of the detected light. This reduces the influence of the light that is reflected by the windshield 91 and reaches the photodiode 75.

[0174] As shown in Table 963, in "S1. Operation Mode", when the UP key 122 is briefly pressed, the CPU 101 increases the volume output from the speaker 105. When the DOWN key 123 is briefly pressed, the CPU 101 decreases the volume output from the speaker 105. When the UP key 122 is long-pressed, the CPU 101 increases the sensitivity (see Figures 20 and 21). When the DOWN key 123 is long-pressed, the CPU 101 decreases the sensitivity (see Figures 20 and 21). When the MODE key 121 is briefly pressed, the CPU 101 switches between voice and buzzer. More specifically, it switches between voice 1 (announcer-like), voice 2 (anime voice), and buzzer sound, as shown in Table 961 (see Figure 19). When the MODE key 121 is long-pressed, the CPU 101 transitions the state of the laser distance meter 1 to "S2. Glass Correction Mode".

[0175] The glass correction mode changes between "S2-1. Neutral", "S2-2. Executing", and "S2-3. Completed". "S2-1. Neutral" is a mode in which nothing is done at the time it is set, and it waits for the glass correction to be executed or the cancel key to be pressed. If the MODE key 121 is pressed and held down, the CPU 101 determines that the cancel key has been pressed. In this case, the CPU 101 does not execute glass correction and changes the state of the laser distance meter 1 to "S3. Detection confirmation mode". If the DOWN key 123 is pressed briefly, the CPU 101 changes the state of the laser distance meter 1 to "S2-2. Executing" in order to execute glass correction.

[0176] In "S2-2. Execution," the CPU 101 performs glass correction. Approximately 3 seconds after the start of glass correction, the CPU 101 changes the state of the laser distance meter 1 to "S2-3. Completed." In "S2-3. Completed," the CPU 101 notifies the result of the judgment (OK or NG) of whether the glass correction was performed successfully. This notification is performed, for example, by outputting sound from the speaker 105 or by controlling the lighting of the LED 125. If the glass correction is performed successfully (OK), the CPU 101 changes the state of the laser distance meter 1 to "S1. Operation Mode." If the glass correction is not performed successfully, the CPU 101 changes the state of the laser distance meter 1 to "S2-1. Neutral."

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

[0178] The CPU 101 controls the state of LED 125 as shown in Table 964 (see Figure 22). LEDs 1, 2, and 3 in Table 963 are included in LED 125 (see Figure 18). LED 1 is an LED that indicates the state of the laser distance meter 1 (device status). LED 2 is an LED that indicates warnings and notifications to the user. LED 3 is an LED that indicates errors to the user.

[0179] Assume that the laser distance meter 1 is in operating mode (see Figures 21 and 22). In this case, the CPU 101 lights up LED 1 green. Furthermore, when the system is in the following states: "Collision Warning (High Speed)", "Collision Prediction (Low Speed)", "Collision Prediction", "Start Information", "Volume Change", "Sensitivity Change", "Notification Sound Change (Voice)", or "Notification Sound Change (Buzzer)", the CPU 101 controls LED 2 to flash red, flash yellow, flash yellow, flash blue, stay lit yellow (1 second), stay lit blue (1 second), stay lit blue (1 second), or stay lit yellow (1 second), respectively.

[0180] Furthermore, when the system is in the "Err1", "Err2", "Err3", "Err4", or "Err5" state, the CPU 101 controls LED 3 to blink red, blue, yellow, green, or white, respectively. Err1 is an error indicating that glass correction is not yet complete. Err2 is an error indicating that the system is in the aging period after power-up. Err3 is an error indicating that the system has stopped operating due to high temperature.

[0181] Assume that the laser distance meter 1 is in glass correction mode (see Figures 21 and 22). In this case, the CPU 101 lights up LED 1 yellow. Also, when the state is "running," "completed (successful)," or "not running or completed (failed)," the CPU 101 controls LED 2 to light up green, blue, and red, respectively. "Not running or completed (failed)" means that glass correction has not been completed.

[0182] Assume that the laser distance meter 1 is in detection confirmation mode (see Figures 21 and 22). In this case, the CPU 101 makes LED 1 blink yellow. Also, when the CPU 101 does not detect the vehicle ahead (i.e., other vehicle 3), it lights up LED 2 red, and when it detects the vehicle ahead, it lights up LED 2 green. As described above, the CPU 101 performs the control shown in Tables 961 to 964. [Explanation of Symbols]

[0183] 1. Laser distance meter 2. Own vehicle 3 Other vehicles 7 Optical Unit 31,95 Reflector 40,41 Output area 50 Lane 60. Ejection control circuit 62 split resistor 63 DC / DC Converters 64 Integral circuit 71 Launch Unit 74 Light receiving unit 75 Photodiode 76 Light-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 lenses 771,772 reflective surface 773~777 Hardly reflective surface 911,912,913 Optical central axis

Claims

1. A device for detecting objects through the glass of a vehicle, It comprises a light emission unit, a light receiving unit, and a control unit, The control unit performs processing for the glass correction mode and processing for the operation mode. In the processing of the glass correction mode, when there is no object to be detected in the emission direction of the emission unit, the brightness information of the light that is emitted from the emission unit and reflected to reach the light receiving unit is acquired and stored. In the processing of the aforementioned operating mode, the system includes a function to detect the object by correcting the signal from the light receiving unit based on the stored brightness information, The control unit is characterized by having a function that, in addition to processing in the glass correction mode and the operation mode, performs processing to detect an object through the vehicle's glass based on user operation and performs processing in the detection confirmation mode to notify whether or not an object has been detected.

2. A device for detecting objects through the glass of a vehicle, It comprises a light emission unit, a light receiving unit, and a control unit, The control unit performs processing for the glass correction mode and processing for the operation mode. In the processing of the glass correction mode, when there is no object to be detected in the emission direction of the emission unit, the brightness information of the light that is emitted from the emission unit and reflected to reach the light receiving unit is acquired and stored. In the processing of the aforementioned operating mode, the system includes a function to detect the object by correcting the signal from the light receiving unit based on the stored brightness information, The control unit is characterized by having a function to provide notification according to the status of the glass correction mode, such as "in progress," "completed (successful)," or "not executed or completed (failed)."

3. A device for detecting objects through the glass of a vehicle, It comprises a light emission unit, a light receiving unit, and a control unit, The control unit performs processing for the glass correction mode and processing for the operation mode. In the processing of the glass correction mode, when there is no object to be detected in the emission direction of the emission unit, the brightness information of the light that is emitted from the emission unit and reflected to reach the light receiving unit is acquired and stored. In the processing of the aforementioned operating mode, the system includes a function to detect the object by correcting the signal from the light receiving unit based on the stored brightness information, The apparatus is characterized by having a function that assigns different functions to the operation buttons in the processing of the glass correction mode and the processing of the operation mode.

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