JP3198455B2 - Distance measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring apparatus for measuring a distance to an object based on a time difference between a timing of emitting pulse light emitted from a light emitting element and a timing of receiving light pulse light received by a light receiving element. Things.

[0002]

2. Description of the Related Art Conventionally, a vehicle forward monitoring device using a semiconductor laser has been proposed as this type of distance measuring device. In this device, pulse light is emitted from the front of the vehicle, reflected by a rear or rear reflector of a preceding vehicle, the reflected and returned pulse light is received, and emission timing of emission pulse light (radiation beam light) is determined. The distance between the host vehicle and the preceding vehicle is measured from the time difference between the light receiving timing of the received light pulse and the received light beam, and an alarm is issued when the measured distance becomes smaller than a predetermined safe inter-vehicle distance.

[0003] In this vehicle front monitoring device, the radiation is a beam light is formed on one beam shape directed straight ahead of the vehicle, the expansion angle phi _t1 in the horizontal direction with respect to the road surface of the radiation beam (FIG. 4 Normally, the radiation beam light is set so as to have one lane width W at the maximum detection distance _Rmax (for example, 70 m). In this case, the shaded area shown in FIG. 5 becomes a blind spot and cannot be detected until the interrupted vehicle 100 enters the area of the radiation beam light.

In order to avoid such inconvenience, it is conceivable to widen the spread angle φ _t1 of the radiation beam light in the horizontal direction. For example, as shown in FIG. 6, the divergence angle of the radiation beam in the horizontal direction is increased from φ _t1 to φ _t2 , and R _cut
(For example, 40 m), it is conceivable that the lane width W is set. However, in this case, the beam spreads too much at the maximum detection distance _Rmax , and the lane and the unnecessary object are detected next to the detection result, which leads to a false alarm.

Therefore, the detection area in front of the vehicle is divided into three zones I, II, and III, and the reflected beam light from zone I (main zone) and the reflected beam light from zone II (first sub-zone) are divided into three zones. The light is received by each light receiving element separately from the reflected light beam from the zone III (second sub-zone), the distance data up to the maximum detection distance _Rmax is valid in the main zone I, and limited in the sub-zones II and III. By making the distance data up to the distance R _cut valid, it is considered to create the detection areas M, SB1, and SB2 as shown in FIG.
By setting such a detection area, that is, by performing forward monitoring in the right zone SB1 and the left zone SB2 in addition to the central zone M, it is possible to improve blind spots at the time of a preceding vehicle interruption without fear of a false alarm. it can.

FIG. 8 is a block circuit configuration diagram showing an example of a vehicle front monitoring device in which blind spots are improved when a front vehicle is interrupted. In the figure, 1 is a semiconductor laser, 2 is a light transmitting lens, 3 is a light receiving lens, and 4-1 to 4-3 are light receiving elements (photodiodes). The semiconductor laser 1 is driven via a driving device 6 based on a trigger pulse periodically sent from a trigger circuit 5, and emits a pulse light synchronized with the trigger pulse via a light transmitting lens 2. The beam shape of the emitted pulse light (radiation beam light) from the semiconductor laser 1 has directivity as shown in FIG. S1 is the directivity of the vehicle in the horizontal direction (front left and right directions), and S2 is the directivity of the vehicle in the vertical direction (front vertical directions).

The central part of the directivity S1 is a radiation beam B _M to the main zone I, and the right part is a radiation beam B to the sub-zone II.
_S1 and the left side are radiation beam light B _S2 to the sub-zone III. That is, the radiation beam from the semiconductor laser 1 is a one in practice, the radiation beam B _S1 and the secondary zone III to the radiation beam B _M and the sub-zone II as its beam shape to the main zone I And the radiation beam light B _S2 .

[0008] The radiation beam light from the semiconductor laser 1 is reflected by an object such as a vehicle ahead or an interrupting vehicle, and the reflected beam light reflected back is condensed by the light receiving lens 3. Then, the reflected light beam B _M from the main zone I, the reflected light beam B _S1 from the sub zone II, and the reflected light beam B _S2 from the sub zone III are respectively received by the light receiving elements 4-1, 4-2,
The light is received at 4-3. Light receiving elements 4-1, 4-2, 4-
Reference numeral 3 converts the received light beam into an electric signal. The converted electric signals are amplified by the amplifiers 7-1, 7-2, and 7-3, respectively, and then sent to the signal processing device 8 as reception pulses.

Since the radiation beam emitted from the semiconductor laser 1 is generated in synchronization with the trigger pulse transmitted from the trigger circuit 5, the trigger pulse (the emission timing of the radiation beam) transmitted from the trigger circuit 5 is transmitted to the signal processor 8. By giving the signals, the time difference between the trigger pulse and each received pulse (the light receiving timing of the received light beam) can be used to determine the main zone I and the sub zone.
It is possible to measure the distance to the object located in II and sub-zone III.

Here, the signal processing device 8 validates the distance data up to the maximum detection distance _{Rmax in} the main zone I, and validates the distance data up to the limit distance _Rcut in the sub-zones II and III. That is, the signal processing device 8 performs
Invalidates distance data beyond the maximum detection distance R _max ,
In the sub zones II and III, distance data beyond the limit distance R _cut is invalidated. As a result, the signal processing device 8 operates the center zone M, the right zone SB1, and the left zone SB2 shown in FIG.
Is set as a detection area by the light receiving elements 4-1, 4-2, and 4-3 to perform forward monitoring.

The signal processor 8 calculates the relative speed with respect to the object from the rate of change of the distance to the object, or calculates the speed of the object from the relative speed and the own vehicle speed detected by the vehicle speed sensor 11. If it is determined or the distance to the object is smaller than the safe inter-vehicle distance, an alarm signal is generated from the alarm device 9 or each measurement data is displayed on the display device 10.

[0012]

In this vehicle forward monitoring device, a semiconductor laser 1, a light transmitting lens 2, a light receiving lens 3,
Light receiving elements 4-1 to 4-3, trigger circuit 5, driving device 6,
The transmitting and receiving units such as the amplifiers 7-1 to 7-3 are accommodated in a case,
It is mounted on the front of the vehicle as a laser sensor. Here, the laser sensor is easy to assemble and has high accuracy in the facing distance between the light transmitting lens 2 and the semiconductor laser 1 and the facing distance between the light receiving lens 3 and the light receiving elements 4-1 to 4-3. It is desired that the accuracy be maintained for a long period of time, the optical axis of the light transmitting lens 2 and the light receiving lens 3 be not shifted, and that it be compact and inexpensive. However, the conventional vehicle forward monitoring device has not been able to say that these requirements have been sufficiently satisfied.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and it is an object of the present invention to simplify the assembling, to set the distance between the light-sending lens and the light-emitting element and the distance between the light-receiving lens and the light-receiving element. It is an object of the present invention to provide a compact and low-cost distance measuring device that has high accuracy of the facing distance, can maintain this accuracy for a long period of time, does not cause a shift in the optical axis of the light transmitting lens and the light receiving lens, and does not cause the displacement.

[0014]

In order to achieve the above object, a first invention (an invention according to claim 1) is to provide a circuit board on which a light emitting element and a light receiving element are arranged by using a central reference plate made of a metal member. Are fixed at a predetermined distance to one surface of the light emitting device, and a light transmitting lens and a light receiving lens are fixed to the other surface at a predetermined distance. According to a second invention (an invention according to claim 2), in the first invention, the central reference plate is fixed in the case. Third
The invention (invention of claim 3) is the first invention in which a plurality of light receiving lenses are provided. According to a fourth invention (an invention according to claim 4), in the first invention, a second circuit board is provided between the circuit board on which the light emitting element and the light receiving element are arranged and the central reference plate, and the second circuit is provided. An opening is provided on a surface of the substrate and the central reference plate facing the light emitting element and the light receiving element.

[0015]

According to the present invention, therefore, in the first invention,
The light-emitting element and the light-receiving element face the light-sending lens and the light-receiving lens with a predetermined distance therebetween with a central reference plate made of a metal member interposed therebetween. In the second invention, a central reference plate made of a metal member is fixed to the case, and the light-emitting element and the light-receiving element face the light-sending lens and the light-receiving lens with a predetermined interval therebetween with the central reference plate interposed therebetween. . In the third invention, the light emitting element and the light receiving element face the light transmitting lens and the plurality of light receiving lenses at a predetermined interval with the central reference plate made of a metal member interposed therebetween. In the fourth invention, the light emitting element and the light receiving element, the light transmitting lens and the light receiving lens face each other at a predetermined interval, with the central reference plate made of a metal member and the second circuit board interposed therebetween. In addition, light is transmitted and received through an opening provided in the second circuit board.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments. FIG. 2 is a block diagram of a vehicle front monitoring apparatus according to an embodiment of the present invention. 8, the same reference numerals as those in FIG. 8 denote the same or equivalent components, and a description thereof will be omitted. In this embodiment, the reflected light beam B _M from the main zone I, the reflected light beam B _S1 from the sub zone II, the sub zone
A light receiving element (photodiode) 4-4 is provided in addition to the light receiving elements 4-1, 4-2, and 4-3 for receiving the reflected light beam B _S2 from III through the main light receiving lens 3-1. An auxiliary light receiving lens 3-2 having a smaller lens diameter than the main light receiving lens 3-1 is disposed on the front surface of the light receiving element 4-4,
And so as to receive the reflected beam B _M from the main zone I even receiving element 4-4.

The output of the light receiving element 4-1 and the output of the light receiving element 4-4 are electrically connected in common, and the amplifier 7-
1 to the signal processing device 8 '.
Further, the output of the light receiving element 4-2 and the output of the light receiving element 4-3 are electrically connected in common, and are supplied to the signal processing device 8 'via the amplifier 7-2.

In this distance measuring device, the radiation beam light from the semiconductor laser 1 is reflected by an object such as a preceding vehicle or an interrupting vehicle, and the reflected beam light reflected back is received by the light receiving lenses 3-1 and 3--3. The light is collected at 2. Then, the reflected beam B _M from the main zone I is the light receiving element 4
It is received at 1 and 4-4, the reflected beam B _S1 from the sub-zone II is received by the light receiving elements 4-2, the sub-zone II
The reflected beam light _BS2 from I is received by the light receiving element 4-3. The light receiving elements 4-1, 4-2, 4-3, and 4-4 convert the received light beam into an electric signal. The electric signals converted by the light receiving elements 4-1 and 4-4 are amplified by the amplifier 7-1 and then sent to the signal processing device 8 'as reception pulses. The electric signals converted by the light receiving elements 4-2 and 4-3 are amplified by the amplifier 7-2 and then sent to the signal processing device 8 'as reception pulses.

The signal processor 8 'measures the distance to the object located in the main zone I from the time difference between the trigger pulse sent from the trigger circuit 5 and the pulse received from the amplifier 7-1. Further, the distance to the objects located in the sub-zones II and III is measured from the time difference between the trigger pulse transmitted from the trigger circuit 5 and the received pulse from the amplifier 7-2.

[0020] That is, the signal processing device 8 ', based on the time difference between receiving timing of the reflected beam B _M from the main zone I in the firing timing and the light receiving element 4-1 and the light receiving element 44 of the radiation beam Then, the distance to the object located in the main zone I is measured. The sub zone III in the reflected beam B _S1 and the light receiving element 4-3 from the secondary zone II on the light receiving elements 4-2 and firing timing of the radiation beam
The distance to the objects located in the sub-zones II and III is measured based on the time difference between any one of the reflected light beams B _S2 and the earlier light-receiving timing.

Then, the signal processing device 8 '
_Is valid for distance data up to the maximum detection distance R _max ,
In the sub zones II and III, the distance data up to the limit distance R _cut is made valid, and only the objects located in the central zone M, the right zone SB1 and the left zone SB2 are monitored forward based on the distance data.

Here, the limit detection distance R in the main zone I
_Since the output of the light receiving element 4-1 and the output of the light receiving element 4-4 are connected by wired OR, the _LIM
Limit detection distance R _LIM1 when only −1 is used (100
m). That is, as shown in FIG. 3, when the conventional limit detection distance R _{LIM (old)} is R _LIM1 , the limit detection distance R _{LIM (new)} in this embodiment is R _{LIM (old)} which is farther than R _{LIM (old). LIM2} .

That is, generally, the radar performance is given by the following radar equation. Pr = Pt · (K · _AT · Ar · Tt · Tr) / {π ² (θ / 2) ² · (φ / 2) ² · R ⁴ } (1) where Pr: reception Power, Pt: transmission power, K: reflectance of target, A _T : effective reflection area of target, Ar: area of light receiving unit (lens), Tt: transmittance of light transmitting system, Tr: transmission of light receiving system Rate, θ: divergence angle of light beam, φ: divergence angle of reflected light, R: distance to target.

As can be seen from this equation, the received power Pr
Is inversely proportional to the fourth power of the distance R to the target. Therefore, by doubling the area Ar of the light receiving section (lens) (provided that other parameters do not change), the reception power P
r is increased, the distance R to the target will be ⁴ √2 times.
Thus, in the present embodiment, the limit detection distance R _LIM is R
_It extends from _LIM1 to R _LIM2 .

[0025] Thus, according to this embodiment, with respect to degradation of the detection performance due to rain and fog, etc., it is possible to prevent a decrease in the following maximum detection distance R _max limit detection distance R _LIM. That is, the limit detection distance R _{LIM (new)} is 120
If assumed obtained as m, the maximum detected as well as the limit detection distance R _{LIM (new)} becomes 84m decreased 30% compared with clear weather by rain or fog like, limits the detection distance R _{LIM (new)} A value equal to or greater than the distance R _max (70 m) can be secured. Thus, regardless of the decrease in the detection performance due to rain and fog, etc., it can be always detected vehicle located maximum detection distance in R _max.

As a method of extending the limit detection distance R _LIM , a method of increasing the transmission power Pt, or increasing the sensitivity of the light receiving element, or improving the performance of the amplifier can be considered. There is no good idea. In the present embodiment, the problem such as electric noise does not occur, and the limit detection distance R _LIM can be extended at low cost. In this embodiment, the output of the light receiving element 4-2 and the output of the light receiving element 4-3 are electrically connected in common, and the
-2, the signal is supplied to the signal processing device 8 ', so that the amplifier 7-3 required in the conventional vehicle forward monitoring device shown in FIG. 8 can be omitted, and the signal processing device 8' Signal processing is also simplified.

FIG. 1 shows a semiconductor laser 1, a light transmitting lens 2, a light receiving lens 3-1 and 3-2, a light receiving element 4-1 to 4-4, a trigger circuit 5, a driving device 6, and amplifiers 7-1 and 7-. FIGS. 1A and 1B are diagrams showing an internal configuration of a laser sensor in which a light transmitting and receiving unit such as 2 is accommodated in a case, and FIG. 1A is a plan sectional view and FIG. In the figure, 12 is a case, 13 is a case 1
Reference numeral 2 denotes a window (glass) attached to the front opening, 14 denotes a signal cable connecting to a display unit (not shown), 15 denotes a central reference plate made of a metal member (aluminum), and 16-1 to 16-3 denote trigger circuits. 5 is a first to third circuit boards in which circuits such as a driving device 6, amplifiers 7-1 and 7-2 are dispersedly constructed. In FIG. 2, the main light receiving lens 3-1 and the sub light receiving lens 3-2 are shown separately for easy understanding, but actually, as shown in FIG. -2 is integrally formed as the light receiving lens 3 '.

The semiconductor laser 1 and the light receiving elements 4-1 to 4-4 are disposed on the first circuit board 16-1. 1 and 17-2. An opening 17-1a is provided at a position of the shield case 17-1 facing the semiconductor laser 1. Also, the light receiving elements 4-1 to 4-3 and 4-4 of the shield case 17-2.
Openings 17-2a and 17-2b are provided at positions opposite to. Also, the circuit boards 16-1 to 16-3
Is the center reference plate 1 using the collars 18-1 to 18-3.
5 is laminated and fixed to one surface.

That is, the bolts of the screws 19 (four) are passed through the other surface of the central reference plate 15, and the bolts of the screws 19 are passed through the collar 18-1 to the second circuit board 16.
-2, the first circuit board 16-1 is dropped through the collar 18-2, and the collar 18-3 is further dropped.
Through the third circuit board 16-3, and tighten the nut 20 to the thread portion of the screw 19 protruding from the upper surface of the third circuit board 16-3, so that the circuit boards 16-1 to 16-
3 is laminated and fixed to one surface of the central reference plate 15.
As a result, the circuit boards 16-1, 16-2, and 16-3 are disposed on one surface of the central reference plate 15 at predetermined intervals L1, L.
2 and L3.

An opening 16-2a is provided at a position of the second circuit board 16-2 facing the semiconductor laser 1,
Openings 16-2b and 16-2c are provided at positions facing the light receiving elements 4-1 to 4-3 and 4-4.
An opening 15a is provided at a position of the center reference plate 15 facing the semiconductor laser 1, and openings 15b and 15c are provided at positions facing the light receiving elements 4-1 to 4-3 and 4-4.
Is provided. Further, a sponge-like light shielding member 21 is provided between the second circuit board 16-2 and the central reference plate 15. Also, when forming the opening 17-1a of the shield case 17-1, an upright piece 17-1b is raised in an L shape, and this upright piece 17-1b is connected to the second circuit board 16-2. It is positioned as a light-shielding plate between the central reference plate 15.

On the other hand, on the other surface of the central reference plate 15,
The light transmitting lens 2 is fixed using the collar 22, and the light receiving lens 3 ′ is fixed using the collar 23. That is, the bolts of the screws 24 (three) are passed from one surface of the center reference plate 15, the light transmitting lens 2 is dropped through the collars 22 into the bolts of the screws 24, and the light transmitting lens 2 projects to the upper surface of the light transmitting lens 2 The light transmitting lens 2 is fixed to the central reference plate 15 by fastening the nut 20 to the thread portion of the screw 24 to be formed.
In addition, the screw 25 (3
The light receiving lens 3 'is dropped through the bolt 23 of the screw 25 through the collar 23, and the nut 20 is fastened to the thread of the screw 25 projecting from the upper surface of the light receiving lens 3'. Light receiving lens 3 'on plate 15
Is fixed. As a result, the light transmitting lens 2 and the light receiving lens 3 ′ are fixed to the other surface of the central reference plate 15 at predetermined intervals L4 and L5.

Here, the circuit boards 16-1 to 16-
3. The center reference plate 15 to which the light transmitting lens 2 and the light receiving lens 3 'are fixed is assembled in advance as a sub-assembly before being assembled into the case 12. The sub-assembly is assembled into the case 12 by screwing the peripheral edge of the central reference plate 15 to the flange step 12a in the case 12. That is, in this embodiment,
Instead of directly mounting the circuit boards 16-1 to 16-3, the light transmitting lens 2, and the light receiving lens 3 'in the case 12,
Since the sub-assembly with the center reference plate 15 at the center and the components attached is assembled later, the assembly is simple.
Workability is improved, cost can be reduced, and compactness is achieved. Also, the center reference plate 15
Is a metal member, so that the subassembly assembly is securely and firmly incorporated into the case 12.

In this embodiment, the central reference plate 15 made of a metal member is used.
There is no deformation such as warpage as in the case where a resin member is used instead, and there is no fear that the optical axes of the light transmitting lens 2 and the light receiving lens 3 ′ are shifted (in particular, the light receiving lens 3 ′ is the main light receiving lens 3).
-1 and the sub-light-receiving lens 3-2, the area of which is large, and the optical axis is easily deviated).

In this embodiment, since the light transmitting lens 2 and the light receiving lens 3 'are fixed to the central reference plate 15 made of a metal member, the light transmitting lens 2 and the light receiving lens 3' are fixed to the central reference plate 15. The accuracy of the intervals L4 and L5 is high,
And this precision can be maintained for a long time. Further, the circuit boards 16-1 to 16-1 are mounted on the central reference plate 15 made of a metal member.
Since 6-3 is fixed, the circuit boards 16-1 to 16-
The accuracy of the distances L1 to L3 between the center reference plate 15 and the center reference plate 15 is high,
And this precision can be maintained for a long time. This means that the accuracy of the facing distance between the light transmitting lens 2 and the semiconductor laser 1 and the facing distance between the light receiving lens 3 'and the light receiving elements 4-1 to 4-4 are high, and this accuracy can be maintained for a long time. It means you can do it.

In this embodiment, the second circuit board 16-2 is located between the center reference plate 15 and the first circuit board 16-1.
Is provided, so that the space between the central reference plate 15 and the first circuit board 16-1 is effectively utilized, and the size thereof is further reduced. That is, the facing distance between the light transmitting lens 2 and the semiconductor laser 1 and the facing distance between the light receiving lens 3 ′ and the light receiving elements 4-1 to 4-4 need to have a predetermined distance in order to secure the focal length. I do. As a result, a space is created between the central reference plate 15 and the first circuit board 16-1. In the present embodiment, the second circuit board 16-2 is provided by utilizing this space. An opening 16 is provided at a position on the circuit board 16-2 facing the semiconductor laser 1 so that the circuit board 16-2 does not interfere.
-2a, and openings 16-2b and 16-2c are provided at positions facing the light receiving elements 4-1 to 4-3 and 4-4.

In this embodiment, a window (glass) 13 is arranged on the front side of the light transmitting lens 2 and the light receiving lens 3 ′, and the aperture of the light transmitting lens 2 and the light receiving lens 3 ′ is formed on the outer peripheral surface of the window 13. The light shielding mask 13-1 is formed by silk printing or the like, avoiding the portions. The light-shielding mask 13-1 prevents extraneous light from entering the inside of the case 12 from the outside, and improves the light receiving accuracy. Further, the light transmitting lens 2 and the light receiving lens 3 ′ are formed as visible light cut lenses (lens of a color like sunglasses), and also serve as a filter that allows only infrared rays to pass.
Further, between the optical system on the light transmitting side and the optical system on the light receiving side, a partition plate 12b provided on the case 12 side, a light shielding member 21,
The light is shielded by the light shielding plate 17-1b.

In this embodiment, the inside of the case 12 is filled with an inert gas (for example, nitrogen gas). As a result, the window 13 and the light transmitting lens 2 and the light receiving lens 3 'are prevented from fogging, and the monitoring performance is prevented from lowering. The filling of the inert gas is performed from the injection part 12c. The injection part 12c is sealed after injection of the inert gas. Specifically, a hexagonal screw whose screw portion is covered with a resin member is screwed into the injection portion 12c, thereby sealing between the screw portion and the wall surface of the injection portion 12c with a resin member. In the present embodiment, the light receiving lens 3 'is formed as an integral body of the main light receiving lens 3-1 and the sub light receiving lens 3-2, but it goes without saying that the light receiving lens 3' may be formed separately. The same structure can be adopted in a laser sensor of a conventional type vehicle front monitoring apparatus having no such device.

[0038]

As is apparent from the above description, according to the present invention, in the first aspect, the circuit board on which the light emitting element and the light receiving element are arranged is provided on one surface of the central reference plate made of a metal member. And the light transmitting lens and the light receiving lens are fixed on the other surface at a predetermined distance, so that the opposing distance between the light transmitting lens and the light emitting element and the light receiving lens and the light receiving element are fixed. , The accuracy of the facing distance can be increased, and this accuracy can be maintained for a long period of time. Further, there is no problem that the optical axis is shifted, and the device is compact. In the second invention, the central reference plate is fixed in the case.
The central reference plate to which the circuit board, the light-sending lens, and the light-receiving lens are fixed is securely and firmly incorporated into the case as a subassembly, which simplifies assembly, improves workability, and promotes cost reduction. Will be able to Further, in the third invention, it is possible to extend the limit detection distance by forming the light receiving lens with the main light receiving lens and the sub light receiving lens. Further, in the fourth aspect, the space between the circuit board on which the light emitting element and the light receiving element are arranged and the central reference plate can be effectively utilized, and further downsizing can be achieved.

[Brief description of the drawings]

FIG. 1 is a diagram showing an internal configuration of a laser sensor in the vehicle front monitoring device shown in FIG.

FIG. 2 is a block circuit configuration diagram of a vehicle front monitoring device according to an embodiment of the present invention.

FIG. 3 is a diagram showing a comparison between a limit detection distance in a main zone in the vehicle front monitoring device and a limit detection distance in a main zone in the conventional vehicle front monitoring device.

FIG. 4 is a diagram showing a spread angle of a radiation beam light in a horizontal direction with respect to a road surface.

FIG. 5 is a diagram showing a blind spot in a case where there is an interrupting vehicle ahead in the conventional vehicle front monitoring device.

FIG. 6 is a diagram illustrating a case where a divergence angle of a radiation beam light in a horizontal direction with respect to a road surface is further increased.

FIG. 7 is a diagram showing a detection area where blind spots can be improved.

FIG. 8 is a block circuit diagram showing a conventional vehicle front monitoring device in which blind spots are improved.

FIG. 9 is a diagram showing the directivity of a semiconductor laser used in the vehicle forward monitoring device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser, 2 ... Light transmission lens, 3 '... Light receiving lens, 3-1 ... Main light receiving lens, 3-2 ... Sub light receiving lens, 4
-1 to 4-4: light receiving element (photodiode), 5: trigger circuit, 6: driving device, 7-1, 7-2: amplifier,
8 ': Signal processing device, 12: Case, 15: Central reference plate, 15a to 15c: Opening, 16-1 to 16-3: Circuit board, 16-2a to 16-2c: Opening.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takashi Yamamoto 500 Kitawaki, Shimizu City, Shizuoka Prefecture Inside the Koito Manufacturing Shizuoka Factory (72) Inventor Satoshi Yashiki 500 Kitawaki, Shimizu City, Shizuoka Prefecture Koito Manufacturing Shizuoka Factory (72) Inventor Taketoshi Fujigaya 500 Kitawaki, Shimizu City, Shizuoka Prefecture Inside Koito Manufacturing Shizuoka Plant (72) Inventor Makoto Yamanoi 500 Kitawaki Shimizu City, Shizuoka Prefecture Koito Manufacturing Shizuoka Plant (56) References JP-A-6-109464 (JP, A) JP-A-6-69867 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01S ⁷ /48-7/51 G01S 17/00 -17/95

Claims (4)

(57) [Claims] 1. A pulse light is emitted from a light emitting element via a light transmitting lens, and pulse light reflected and returned is received by a light receiving element via a light receiving lens, and emission timing of the emitted pulse light from the light emitting element And a circuit board on which the light emitting element and the light receiving element are arranged, and a surface on one side , wherein the distance measuring apparatus measures a distance to an object based on a time difference between the light receiving timing of the light receiving pulse light and the light receiving element. And a central reference plate made of a metal member having the light transmitting lens and the light receiving lens fixed at a predetermined interval on the other surface. A distance measuring device characterized by the above-mentioned. 2. The distance measuring device according to claim 1, wherein the central reference plate is fixed in the case. 3. The distance measuring device according to claim 1, further comprising a plurality of light receiving lenses. 4. The light emitting device according to claim 1, further comprising a second circuit board provided between the circuit board on which the light emitting element and the light receiving element are arranged and the central reference board, and the light emission of the second circuit board and the central reference board. A distance measuring device, wherein an opening is provided on a surface facing the element and the light receiving element.