JPS61149876A - Transmitter for signal for range measurement - Google Patents

Abstract

PURPOSE:To obtain a small-sized, low-cost range measuring radar which takes a measurement over a wide range from long distance to short distance and is small in power consumption by providing plural signal projectors which differ in projection beam angle according to a distance measurement range. CONSTITUTION:A light emitting element 1 and a lens 2 form the 1st signal projector S1 which has a wide projection beam angle theta1 and a light emitting element 3 and a lens 4 form the 2nd signal projector S2 which has a narrow projection beam angle theta2. Those signal projectors S1 and S2 which have the different projection angles are combined together to form a transmitter TX. Consequently, the projector S1 is made to correspond to a short-range object R1 and the projector S2 is made to correspond to a long-range object R2, so that the power consumption and size are reduced on the whole. A laser light beam, a radio wave, an ultrasonic wave, etc., are applicable as a range measuring medium.

Description

Detailed Description of the Invention (Technical Field of the Invention) The present invention projects a ranging signal, such as light, toward a target, and receives a reflected signal, such as reflected light, of the signal at the target. The present invention relates to a signal transmitting device for a distance measuring radar that measures the distance to a target.

(Prior art and its problems) In conventional ranging radars, the transmitting device for ranging signals is generally comprised of a single signal projector for the signal projection beam angle.

Generally, the distance that a signal projected from a signal projector effectively reaches (the longest distance in which a reflected signal can be detected) increases as the output power of the signal projector increases, and also increases as the projection beam angle narrows.

Therefore, when long-distance measurement is desired, it is necessary to increase the output power of the signal projector or to reduce the projection beam angle.

Increasing the output power of the signal projector will increase the cost and size of the device, and will also increase the power consumption during operation, while reducing the projection beam angle will increase the cost, especially at short distances. The measurable range becomes narrower. Therefore, for example, when a distance measuring radar for measuring the distance between vehicles is required to be installed in a limited installation space, operated with limited power, and to perform measurements over a wide range, the above-mentioned method is used. Satisfactory results have not been obtained using conventional ranging radars.

(Purpose of the Invention) The present invention is proposed to solve the above-mentioned conventional problems, and is capable of measuring a wide range of distances from long distances to short distances, and is compact and low-cost with low power consumption. The purpose is to obtain a ranging radar.

(Summary of the Invention) For the above purpose, the present invention provides a plurality of signal projectors with different projection beam angles depending on the distance measurement range.

(Example) All drawings are for detailed explanation of the present invention.
Fig. 1 is a structural diagram of the first embodiment, Fig. 2 is a diagram explaining the projection beam characteristics of the first embodiment, Fig. 3 is a structural diagram of the second embodiment, and Fig. 4 is a diagram of the second embodiment. FIG. 3 is a diagram illustrating projection beam characteristics.

All of the embodiments are examples in which the present invention is applied to a distance measuring radar for measuring the distance between cars, and light (laser light) is used as a distance measuring signal.

First, a first embodiment will be explained with reference to FIGS. 1 and 2.

In Figures 1 and 2, TX is a transmitter, A is a road,
R1 and R3 are ranging target objects (for example, a preceding vehicle, hereinafter referred to as objects), and in the transmitter TX, S,
and S are first and second projectors (signal projectors), respectively, 1 and 3 are light emitting elements, and 2 and 4 are projecting lenses (hereinafter referred to as lenses).

The transmitter TX has a first projector S□ for short distances, which is made up of a light emitting element 1 and a lens 2, and a second projector S, for long distances, which is made up of a light emitting element 3 and a lens 4.

The distance between the light emitting elements 1, 3 and the lenses 2, 4 and the focal length of the lenses 2, 4 are such that the projected beam angle θ of the projected light from the first projector S1 is different from that of the second projector S, The projected beam angle θ of the projected light is set to be wider than the snow.

As shown in FIG. 2, the projection direction g of light from each of the projectors S1 to S1 is set in the direction of travel of a vehicle equipped with a distance measuring radar, that is, in the direction of people on the road. Incidentally, since the distance between the floodlights 5leS1 is so short that it can be ignored compared to the width of the road A, both the floodlights S1, S! The projection points of the light may be the same, and FIG. 2 is drawn accordingly.

Projection beam angle θ3 of the projection light from each projector S1*Sl. θ, is the effective reach L1 of each projection light
*A! It is set to cover the width a of a road A, for example, during the required measurement at the longest point of the road A.

Now, considering the case where L H = n L 1 and an attempt is made to cover the range of distance t with only the projection light of the first projector Si, the light emitting output of light emitting element 1 covers the range of distance t1. It requires n times as much.

That is, in general, when a point separated by a distance t is irradiated with a projection angle of angle θ, the irradiated area at the point of distance t is an area corresponding to the bottom of a conical space of angle θ and height L, This area is proportional to the square of the distance if the angle θ is constant. Therefore, if the intensity of the light source is constant, the irradiation intensity of the area will be inversely proportional to the square of the distance. This can be expressed as a relational expression as follows.

L=k (1) where L is the irradiation intensity, X is the intensity of the light source, and k is a proportionality constant (a constant determined by the angle θ).

There is a reflective object at the point that is irradiated with the above irradiation intensity],
The intensity (
Since the above-mentioned reflecting object can be regarded as a strong light source (received light intensity at the receiver), the following relational expression holds true if considered in the same way as above.

(2) where L' is the received light intensity at the receiver, and k' is a proportionality constant (a constant determined by the angle θ').

From the relational expressions (1) and (2) above, L'=L・□ (3) However, K-to-to'. If we apply the relationship in equation (3) to the distance t1 and t is in the relationship rt1=ntIJ, and since the reception strength at the receiver / and L2t must be equal to each other, from equations (4) and (5) above, From this equation (6), we get: , the light emitting output of the light source when covering the range of distance t1 is n4 times.

Next, examples of the present invention will be considered.

The irradiated area at a distance 1X in front of the first projector S1 and the irradiated area in front at a distance t by the second projector S are:
The respective projection angles θ1 and θ.

They are set to be the same by making them different. Thus, each floodlight S1.

If the intensities of the light emitted by the objects R1 and R3 are equal, the intensities of the irradiated light reaching the objects R1 and R3 will be equal.

Using this relationship as in equation (1) above, each distance L'st!
Expressed for: where k and , are constants determined by the angles θ1 and θ-thickness, respectively.

Next, the intensity of the reflected light returned to the receiver by the objects R1 and R is considered in the same manner as in equation (2) above, and the intensity of the reflected light is calculated for each distance 1. ,1
．． Expressed as: ■.

However, k, ' and 2' are constants determined by the angle of reflection of the reflected light on objects R1 and R7, respectively.
As before, assuming that the angles of reflection of the reflected light from objects R1 and R2 are equal, kl- has a distance of 2'...αρ distance 1. ．．
1. Regarding the relationship between t, m nt, and J, from this relationship and the relationship between equations (8), (9), and (to) above, from equation (8) above, we get = n ・to 1... ...(g) is obtained, and from the relationship between the α1 equation and the above Guya and equation (6), the relationship Ll--L' .......α→ is obtained.This α1 equation is set so that the irradiated area at distance t1 and Ll ahead are equal, and if the projected light intensity of the light source is the same, the received intensity of the reflected light at distance t and ahead object R2 is equal to distance t and ahead object R2. It is shown that the received intensity of the reflected light at the object R1 is r 1/n2J, and when the received intensities of both are made equal (that is, L,
'! L2'), the light projection intensity of the long-distance projector S may be set to n times the light projection intensity of the short-range projector S1.

From the above, it can be seen that the distance 1 in the first embodiment of the present invention.
The light projection output required to cover the range of distance L1 (the sum of the light projection outputs of the projectors S1 and S) is (1+n) times the light projection output necessary to cover the range of distance L1.

Therefore, compared to the case where there is only one light projector, in the first embodiment of the present invention, the light projection output may be (1+n2)/n' times,
The power consumption of the projector is extremely low.In addition, the light output of each projector Si and S can be smaller than when using a single projector, making it easier to implement heat dissipation measures and making the equipment smaller. It becomes possible to

When a vehicle is equipped with the distance measuring radar according to the present invention, if the distance measurement range is set to be wider than the width of the road A, considering when the vehicle is traveling on a curve, it will be possible to set the distance measurement range to be wider than the width of the road A. This is convenient because it allows you to catch cars, etc. The second embodiment described below is an embodiment that takes into consideration the above-mentioned curve traveling, and 5 is a light emitting element, 6 is a light projecting lens, and other symbols are the same as in FIG. 1 above. be.

The second embodiment is provided with one floodlight S for short distance use and two floodlights S for long distance use, and the first floodlight S1 includes a light emitting element 1 and a lens 2. , second
The third floodlight S has a light emitting element 3 and a lens 4, and the third floodlight S has a light emitting element 5 and a lens 6, respectively.

As shown in FIG. 4, the projection direction g of the light from the first floodlight S1 is aligned with the direction of the road A, and the projection direction g of the light from the second and third floodlights S and S is aligned with the direction of the road A. and j are deviated from the direction of road A by angles α1 and α, respectively, and the projected beam angles θ1, θ, and θ are θ,〉θ, respectively.

The focal length of the lens 2, 4.6 and the distance between the lens 2, 4.6 and the light emitting element 1, 3°5 are set so that θ□>θ.

The distance measurement range (light projection space) by the first floodlight S1 is a short distance t, and the maximum range is the width a of the road A, and the second and third floodlights S and S , K cover long distances t and t, and have angles β1 and β on both sides from road A, respectively.
, it is outside the range. The existence of this protruding ranging area allows objects diagonally in front of the vehicle (preceding vehicle) to be detected, which is convenient when driving around a curve.

Regarding the light emitting outputs of the light emitting elements 1, 3 and 5 in the second embodiment, t,=HL1 as in the first embodiment.
and the projected beam angle θ8. 0 for θ. =08,
Projection distance 1. ．． 1. For %%t2==t3, the distance of the long-range projector S and S, tt C=ts
) in the conical space (projection space d.

If the diameter of the bottom of ・) is equal to the length a of road A, then
When the range of distance t is covered only by floodlight S1, (
1+2 n2)/n' is sufficient.

That is, in the second embodiment, compared to the first embodiment described above,
The other conditions are the same as in the first embodiment except that a third floodlight S having the same characteristics as the second floodlight S is added.When considering the power consumption of the entire floodlight, 1
It is only necessary to add the power consumption of the third light projector S3 to the power consumption in the embodiment.

From the above, power consumption is reduced in the second embodiment as well as in the first embodiment.

Although all of the embodiments described above use light (laser light) as the distance measuring medium, for example, radio waves, ultrasonic waves, etc. can also be used as the distance measuring medium, and the difference in distance measuring medium is the main difference. This does not change the gist of the invention.

In addition, in the second embodiment, the long-distance projectors S and S, the respective projection beam angles θ and θ3, the declination angles α and α1 of the projection direction, and the projection distances t and t3 are , may be equal to each other, or may be different depending on the ranging range, etc.

That is, various distance measurement patterns can be created depending on how these settings are made.

(Effects of the Invention) As explained in detail above, according to the present invention, the power consumption of the distance measuring radar can be reduced, and the equipment can be made smaller.
Therefore, it is extremely advantageous to apply the present invention to a distance measuring radar installed in an object such as an automobile, which has limited usable electric power and limited installation space.

Also, depending on how the multiple projectors are set, various distance measurement/
Since the 4' turn can be set, it is possible to provide a distance measuring radar with an extremely wide range of applications, and the present invention has extremely significant effects.

[Brief explanation of drawings]

The drawings are not meant to provide a detailed explanation of the invention.
1 and 3 are structural diagrams of the first and second embodiments, respectively, and FIGS. 2 and 4 are diagrams for explaining the projection beam characteristics of the first and second embodiments, respectively. (Main symbols) TX...Transmitter J, s, t SI
”・Floodlight 1.3.5...Light emitting element 2,4.6・
...Light projection lens 4 Figure 7, 7 Figure 2

Claims (1)

[Claims] The distance to the target is determined by projecting a signal toward a target, receiving the signal reflected by the target, and measuring the time from the time the signal is projected to the time the reflected signal is received. A distance measurement signal transmitting device for a distance measurement radar equipped with a plurality of signal projectors with different projection beam angles depending on the distance measurement range.