JPH07159538A - Illuminating type range-finding device - Google Patents

Abstract

PURPOSE:To optimize the detection area of an illuminating type range-finding represented by an optical intervehicular distance meter. CONSTITUTION:The optical intervehicular distance meter is mounted in a running vehicle body and includes a pair of projection means 1 and reception means 2. The projection means 1 projects within a predetermined illuminating angle range a primary beam 5 including center luminous flux 3 and marginal luminous flux 4 toward a target vehicle body located in a predetermined range. The reception means 2 receives a secondary beam 10 reflected from the target object and measures the time required for the secondary beam to return, thereby measuring the intervehicular distance. The projection means 1 is provided with a liquid crystal filter 15 whereby the intensity of the marginal luminous flux 4 is variably lowered. Thereby, in a long range, the marginal luminous flux 4 is made ineffective while the center luminous flux 3 is kept effective so as to narrow an effective illuminating angle range. On the other hand, in a short range, the marginal luminous flux 4 is held effective to widen an effective illuminating angle range CA. Further, a control circuit 17 which adjusts the intensity of the marginal luminous flux 4 by controlling the liquid crystal filter 15, is provided so that the effective illuminating angle range can be set to the optimum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light irradiation type distance measuring device for irradiating a target object with light emitted from a light emitter and detecting a return time of the reflected light to measure a distance to the target object.

[0002]

2. Description of the Related Art Conventionally, a light irradiation type distance measuring device has been used for non-contact and remote distance measurement in various fields. For example, it is applied to an optical distance meter. The optical inter-vehicle meter is mounted on the traveling vehicle body and includes a pair of light projecting means and light receiving means. The light projecting means projects the primary light including the central light beam and the peripheral light beam to a target vehicle body in a predetermined distance region in a predetermined irradiation angle range. On the other hand, the light receiving means receives the secondary light reflected from the target vehicle body, detects the return time thereof, and measures the inter-vehicle distance.

[0003]

As shown in FIG. 5, a vehicle body 101 traveling along a predetermined lane 100 is equipped with an optical inter-vehicle distance meter. The light projecting means 102 incorporated in this inter-vehicle meter projects the primary light 104 forward in a predetermined irradiation angle range 103. As described above, the primary light 104 includes the central light flux that travels along the central line 105 of the lane 100 and the peripheral light flux that is oblique to the central line. The primary light is reflected by the target vehicle body in front, travels backward as secondary light, and is received and detected. The arrival distance of the primary light is finite, and if it exceeds this distance, the intensity of the secondary light reflected from the target becomes weak, so that it cannot be detected. Therefore, the detection area 106 in which normal distance measurement is possible is substantially fan-shaped as shown in the figure. Since the viewing angle is widened when the target vehicle body is in close proximity, the target (reflecting plate) of the target vehicle body may not be captured unless the irradiation angle range 103 is set wide. However, if the irradiation angle range is widened too much, the detection area 106 may expand laterally in the long-distance area and may include adjacent lanes. In this case, there is a fear of detecting an object outside the target vehicle body, which is a problem.

On the other hand, as shown in FIG. 6, the irradiation angle range 103
If is set to be narrow, the detection area 10
6 can be reduced and only the target lane 100 can be covered. However, on the contrary, there is a possibility that the detection area 106 becomes too narrow in the short-distance region and the target of the target vehicle body cannot be captured.

As can be understood from the above description, the conventional optical inter-vehicle meter has a problem that it is difficult to set the detection area 106 without excess or deficiency under necessary and sufficient conditions in both the near and far distance ranges. . Therefore, the present invention has a basic object to enable setting of a detection area corresponding to both the near and far distance areas.

A semiconductor laser or the like is used as the light source of the light projecting means, and the primary laser light is emitted forward with a predetermined output power. However, since the output power varies, the detection area is not constant. When the power increases, the detection area expands in the distance direction and the width direction of the lane. Conversely, when the output power decreases, the detection area shrinks similarly. For this reason, there is a problem that the detection area is not constant due to the fluctuation of the output power or other fluctuations, and there is a fear that incorrect distance measurement is performed.
Alternatively, it is conceivable that the output power is intentionally increased in order to improve the ranging accuracy of the target vehicle body located in the long-distance area. At this time, the detection area may be expanded not only in the distance direction but also in the width direction, so that there is a possibility that wrong distance may be measured. In view of the problems of the conventional technique, the present invention has a particular object to optimize the detection area according to the fluctuation of the primary light intensity.

[0007]

In order to achieve the above-mentioned object of the present invention, the following means were taken. That is, in a light irradiation type distance measuring device which irradiates a target object with light emitted from a light emitting body through a light projecting lens and detects a return time of the reflected light to measure the distance to the target object. It is possible to set a divergence angle of the outgoing light by providing a member whose electric transmittance can be electrically controlled with respect to the outgoing light passing through the peripheral portion of the optical disk, and externally adjusting the optical transmittance. It is characterized by what was done. Further, it is characterized in that the light transmittance can be optimally adjusted according to the power of the light emitting body.

The light irradiation type distance measuring device described above is suitable for, for example, an optical headway distance meter. That is, the optical distance meter according to the present invention has, as a basic configuration, a pair of light projecting means and light receiving means mounted on the traveling vehicle body. The light projecting means projects the primary light including the central light flux and the peripheral light flux to a target vehicle body in a predetermined distance region within a predetermined irradiation angle range. on the other hand,
The light receiving means receives the secondary light reflected from the target vehicle body, detects the return time thereof, and measures the inter-vehicle distance. In such a configuration, a variable limiting unit that variably suppresses the intensity of the peripheral light flux is provided, and the peripheral light flux is invalidated in the long-distance region and the central light flux is effectively maintained to narrow the effective irradiation angle range. Turn into. On the other hand, in the short-distance region, the peripheral luminous flux is effectively kept and the effective irradiation angle range is kept wide. Further, a control means for controlling the variable limiting means to adjust the intensity of the peripheral light flux is provided. This makes it possible to optimally set the effective irradiation angle range. Preferably, the control means comprises means for detecting the intensity of the primary light. When it is detected that the primary light intensity has increased to extend the measurable long-distance region, the intensity of the peripheral luminous flux is automatically reduced in response to this, preventing an excessive expansion of the effective irradiation angle range.

[0009]

According to the present invention, the limiting means for selectively suppressing the intensity of the peripheral luminous flux is provided. The peripheral light flux whose intensity is attenuated as compared with the central light flux does not have sufficient intensity in the long-distance region, and the secondary light reflected backward from the target is extremely weak and cannot be detected by the light receiving means. In other words, since the peripheral light flux is invalidated in the long-distance area, the effective irradiation angle range becomes narrow, and it is possible to prevent the detection area from expanding excessively. On the other hand, in the short-distance region, the peripheral light flux that has been attenuated also has a certain level of intensity, and the component reflected and retreated by the target object can be sufficiently detected by the light receiving means. Therefore, in the short-distance region, the effective irradiation angle range is kept wide and a sufficient detection area can be secured. As described above, the detection area can be accurately set over both the near and far distance ranges.

Furthermore, the above-mentioned limiting means can variably suppress the intensity of the peripheral light flux. By controlling this variable limiting means to adjust the intensity of the peripheral light flux, the effective irradiation angle range can be optimized and an appropriate detection area can always be maintained. For example, when the output power of the light source included in the light projecting means increases, the detection area also expands accordingly. In this case, expansion of the detection area can be prevented by increasing the amount of attenuation of the peripheral light flux and adjusting the intensity to be low. Therefore, it is possible to deal with a variation factor such as the output power of the light source, and it is possible to always maintain a stable detection area.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a first embodiment of a light irradiation type distance measuring device according to the present invention, which is applied to an optical distance meter. As shown in the figure, the optical distance meter includes a pair of light projecting means 1 and light receiving means 2. The light projecting means 1 projects the primary light 5 including the central light beam 3 and the peripheral light beam 4 to a target vehicle body (not shown) in a predetermined distance region within a predetermined irradiation angle range. In this example, the light projecting means 1 is composed of a semiconductor laser 6 serving as a light source and a light projecting lens 7.
The semiconductor laser 6 is driven by the drive circuit 8 and emits the primary light 5 pulse-modulated according to the reference signal supplied from the oscillation circuit 9.

On the other hand, the light receiving means 2 receives and detects the secondary light 10 reflected from the target vehicle body. The light receiving means 2 is composed of a photodiode 11 and a condenser lens 12.
The photodiode 11 outputs an electric signal in response to a change in the amount of received pulse-modulated secondary light 10. This electric signal is input to the phase comparison circuit 13, the phase is compared with the reference signal supplied from the oscillation circuit 9, and the delay time is detected. This delay time corresponds to the return time of the secondary light 10, and the further the target vehicle body is, the longer the return time becomes.
The arithmetic circuit 14 arithmetically processes the return time information output from the phase comparison circuit 13 and outputs inter-vehicle distance information. This inter-vehicle distance information is displayed on, for example, an in-vehicle monitor.

As a feature of the present invention, a variable limiting means for variably suppressing the intensity of the peripheral light flux 4 is provided. In this example, this variable limiting means is composed of a liquid crystal filter 15. As shown in the figure, the liquid crystal filter 15 is a projection lens 7
Is arranged on the front surface of, and selectively attenuates only the peripheral light flux 4 to suppress its intensity. The amount of attenuation depends on the transmittance of the liquid crystal filter 15. The liquid crystal filter 15 is driven by the drive circuit 16 and the transmittance changes according to the drive voltage. When the transmittance is low, the amount of attenuation of the peripheral light beam 4 is increased and the intensity is decreased. On the contrary, when the transmittance is high, the amount of attenuation is small and the intensity of the peripheral light flux can be set high. As described above, the liquid crystal filter 15 can variably control the transmittance, and the intensity of the peripheral light flux 4 can be freely changed. Although the liquid crystal filter 15 is used as the variable limiter in this example, the present invention is not limited to this. Instead of the liquid crystal filter 15, other types of electro-optical modulators can be used. In this way, by suppressing the intensity of the peripheral light flux by using the liquid crystal filter 15, the peripheral light flux can be invalidated in the long-distance region, and the central light flux 3 can be effectively maintained to narrow the effective irradiation angle range. On the other hand, in the short-distance region, the peripheral luminous flux 4 can be effectively held and the effective irradiation angle range can be maintained at a wide angle.

Further, a control circuit 17 for controlling the liquid crystal filter 15 to adjust the intensity (attenuation amount) of the peripheral luminous flux 4 is
It is connected to the drive circuit 16. The control circuit 17 controls the transmittance of the liquid crystal filter 15 via the drive circuit 16 to optimally set the effective irradiation angle range. The control circuit 17 includes, for example, a volume, and the drive circuit 16
Sets the level of drive voltage output from.

The operation of the optical headway distance meter shown in FIG. 1 will be described in detail with reference to FIG. As shown in the figure, an optical inter-vehicle meter is mounted on a vehicle body 22 that travels along a predetermined lane 21. The light projecting means 1 incorporated in this optical distance meter emits the primary light 5 toward the front. As described above, in the comparatively short distance region CR, the marginal luminous flux 4
Is effectively maintained, and the effective irradiation angle range CA is relatively wide. On the other hand, in the long-distance region FR, since the peripheral light flux is attenuated, the reaching distance is not extended and is invalidated. In other words, since only the central light flux effectively contributes to the distance measurement, the effective irradiation angle range FA has a narrow angle. In this way, the effective irradiation angle range CA is widened in the short distance region CR and the effective irradiation angle range FA is narrowed in the long distance region FR, whereby the detection area 23 can be set accurately along the lane 21.

By the way, the output power of the light source included in the light projecting means 1 includes various fluctuation factors. If the output power fluctuates in the increasing direction, the intensity level of the primary light 5 rises overall, so that the detection area 23 shown by the solid line expands to the detection area 24 shown by the dotted line. As a result, the detection area 24 extends beyond the width of the lane 21 and extends to the adjacent lane, and there is a fear that incorrect distance measurement will be performed. Therefore, in the present invention, the control circuit 17 is operated to reset the transmittance of the liquid crystal filter 15 to a lower level via the drive circuit 16. As a result, the increase in the output power of the light source is offset and the detection area can be returned to the optimum state. In this example, the control circuit 17 is manually operated. Liquid crystal filter 1
5, the transmittance is variably controllable. In addition to this, the light shielding width (mask width) can be variably adjusted, so that the cross-sectional areas of the peripheral light flux 4 and the central light flux 3 can be varied, thereby achieving a higher accuracy. A high optimization of the detection area 23 can be achieved. Instead of the variable optical modulator such as the liquid crystal filter 15,
It is also conceivable to suppress the intensity of peripheral light flux by using a pure optical attenuation member such as an ND filter. However, in this case, the fluctuation of the output power cannot be corrected and the optimum setting of the detection area cannot be realized.

FIG. 3 is a schematic block diagram showing a second embodiment of the optical headway distance meter according to the present invention. The basic structure is similar to that of the first embodiment shown in FIG. 1, and corresponding parts are designated by corresponding reference numerals to facilitate understanding. The difference from the first embodiment is that the arithmetic circuit 1 for performing arithmetic processing of the delay time information output from the phase comparison circuit 13
4 is included in the CPU 31 and the liquid crystal filter 1
That is, the CPU 31 includes the control circuit 17 for adjusting the transmittance of item 5. Further, an additional photodiode 32 is provided as a means for detecting the intensity of the primary light 5 emitted from the semiconductor laser 6. This photodiode 3
2 is connected to the CPU 31 via an amplifier (AMP) 33, a sample and hold circuit (S / H) 34, and an analog / digital converter (A / D) 35.

The drive circuit 8 causes the semiconductor laser 6 to emit impulse light, and the projection lens 7 irradiates the primary light 5 to a target vehicle body (not shown). The secondary light 10 reflected from the target vehicle body is passed through the light receiving lens 12 to the photodiode 11
Focused on top. The phase comparison circuit 13 detects the return time of the secondary light 10 and transfers the result to the CPU 31. C
The PU 31 arithmetically processes the return time and measures the inter-vehicle distance. On the other hand, the additional photodiode 32 monitors the light emission power of the primary light 5 and outputs a corresponding electric signal. The electric signal is amplified to a level that can be processed by the amplifier 33, and is sampled and held by the sample and hold circuit 34. The analog electric signal sampled and held is the analog / digital converter 3
It is converted into a digital signal by 5 and transferred to the CPU 31. When the CPU 31 determines that the emission power of the semiconductor laser 6 is increased based on the input digital signal, it outputs a predetermined digital control signal. This digital control signal is converted into an analog control signal by a digital / analog converter (D / A) 36, and the light transmittance of the liquid crystal filter 15 is reduced via the drive circuit 16.

FIG. 4 is a schematic diagram for explaining the operation of the optical headway distance meter shown in FIG. To make it easier to understand
Corresponding reference numerals are given to portions corresponding to the schematic view of FIG. When the emission power of the light projecting means 1 is increased in order to accurately detect the target vehicle body located at a distant place, the measurable long-distance region FR is extended and the detection area 41 is also expanded as a whole to reach the adjacent lane. There is a fear that incorrect distance measurement will be performed. Therefore, when it is detected by the additional photodiode 32 that the intensity of the primary light 5 is increased, the intensity of the peripheral luminous flux is selectively reduced in accordance with this. This makes it possible to prevent the effective irradiation angle ranges CA and FA from expanding excessively. That is, the intensity of the peripheral light flux is suppressed and the predetermined detection area 42 is held, and only the intensity of the central light flux is increased, so that it becomes possible to measure the distance of the target vehicle body farther away without error.

Although the first and second embodiments described above are particularly related to the optical headway distance meter, the present invention is not limited to this. INDUSTRIAL APPLICABILITY The present invention is broadly applicable to light irradiation type distance measuring devices. That is, it is applicable to a light irradiation type distance measuring device that measures the distance to the target by irradiating the target with the light emitted from the light emitter through the light projecting lens and detecting the return time of the reflected light. A member for electrically controlling the light transmittance of the emitted light passing through the peripheral portion of the light projecting lens is provided, and the light transmittance is externally adjusted to arbitrarily change the spread angle of the emitted light. The feature is that it can be set to. Further, it is characterized in that the light transmittance can be optimally adjusted according to the power of the light emitting body.

[0021]

As described above, according to the present invention, only the peripheral luminous flux included in the primary light is selectively suppressed to widen the effective irradiation angle range in the short distance area and to increase the effective irradiation angle range in the long distance area. The irradiation angle range is narrowed. Thereby, the detection area can be set with high accuracy. Further, there is an effect that the effective irradiation angle range can be adjusted and the detection area can be optimally set by variably suppressing the intensity of the peripheral light flux. In particular, when the primary light intensity is increased in order to improve the measurement accuracy of the target located in the long-distance area, the intensity of the peripheral luminous flux is automatically reduced according to this to prevent an excessive expansion of the effective irradiation angle range and perform optimum detection. This has the effect of maintaining the area.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of an optical headway distance meter according to the present invention.

FIG. 2 is a schematic diagram for explaining the operation of the optical headway distance meter shown in FIG.

FIG. 3 is a block diagram showing a second embodiment of the optical headway distance meter according to the present invention.

FIG. 4 is a schematic diagram for explaining the operation of the optical headway distance meter shown in FIG.

FIG. 5 is a schematic diagram for explaining a problem of a conventional optical distance meter.

FIG. 6 is a schematic diagram for explaining the problem.

[Explanation of symbols]

 1 Light emitting means 2 Light receiving means 3 Central light flux 4 Peripheral light flux 5 Primary light 6 Semiconductor laser 7 Light emitting lens 8 Driving circuit 9 Oscillation circuit 10 Secondary light 11 Photodiode 12 Condensing lens 13 Phase comparison circuit 14 Arithmetic circuit 15 Liquid crystal filter 16 Drive circuit 17 Control circuit

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Ikuo Sakauchi 2-16-20 Shimura, Itabashi-ku, Tokyo In-house Copal (72) Inventor Keiji Fujimura 1-2-2 Gosho-dori, Hyogo-ku, Hyogo Prefecture No. 28 in Fujitsu Ten Co., Ltd. (72) Inventor Hideki Kajioka 1-2-2 Goshodori, Hyogo-ku, Kobe, Hyogo Prefecture

Claims (4)

[Claims] 1. A light irradiation type distance measuring device for irradiating a target object with light emitted from a light emitting body through a light projecting lens and detecting a return time of the reflected light to measure a distance to the target object. A member capable of electrically controlling the light transmittance with respect to the outgoing light passing through the peripheral portion of the light projecting lens is provided, and the light transmittance is externally adjusted to arbitrarily set the divergence angle of the outgoing light. A light irradiation type distance measuring device characterized by being settable. 2. A light irradiation type measurement for irradiating a target object with light emitted from a light emitting body through a light projecting lens with a predetermined power and detecting a return time of the reflected light to measure a distance to the target object. In the distance device, a member whose light transmittance is electrically controllable with respect to outgoing light passing through the peripheral portion of the light projecting lens is arranged, and the light transmittance is optimally adjusted according to the power of the light emitter. A light irradiation type distance measuring device characterized in that it is possible. 3. A pair of light projecting means and light receiving means mounted on the traveling vehicle body are provided, and primary light including a central light flux and peripheral light flux is projected onto a target vehicle body in a predetermined distance area within a predetermined irradiation angle range. An optical distance meter that emits light and receives the secondary light reflected from the target vehicle body, detects the return time thereof, and measures the inter-vehicle distance, and includes variable limiting means for variably suppressing the intensity of the peripheral light flux. That is, the peripheral luminous flux is invalidated in the long-distance region, the central luminous flux is effectively maintained to narrow the effective irradiation angle range, and the peripheral luminous flux is effectively maintained in the short-distance region to widen the effective irradiation angle range. The optical distance meter is characterized in that it further comprises control means for controlling the variable limiting means to adjust the intensity of the peripheral light flux so that the effective irradiation angle range can be optimally set. 4. The control means comprises means for detecting the intensity of the primary light, and when the intensity of the primary light increases to extend the measurable long-distance region, the peripheral means selectively responds to the increase in primary light intensity. 4. The optical inter-vehicle meter according to claim 3, wherein the intensity of the luminous flux is automatically reduced to prevent the effective irradiation angle range from being excessively expanded.