JPH05203745A - Optical head for optical radar system - Google Patents

Abstract

PURPOSE:To enable low consumption beam scanning with a smaller size by changing a relative position of a photodetector and a receiving lens alternately almost in the same direction and at the same amplitude within a plane almost vertical to optical axes of respective lenses. CONSTITUTION:A tip part of a bar-shaped body 35 is inserted into a through hole 23 on a lens holding plate 20. The base part of the bar-shaped body is fixed at a peripheral part of a rotary disc 37 of a stepping motor 38. A small permanent magnet is buried at a specified point on an outer circumferential surface of the disc 37. A rotation sensor 39 is provided to detect an angle of rotation of the disc 37 by checking the passage of the permanent magnet using a Hall element or the like. Then, with the rotation of the motor 38, the tip of the bar-shaped body 35 mounted eccentric on the disc 37 moves depicting a circle. As a result, the holding plate 20 vibrates horizontally and a lens 21 for sending light and a receiving lens 22 move in the same direction and by the same distance only within a plane vertical to optical axes thereof thereby enabling the scanning of a light beam and a receiving visual field.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head of an optical radar system used in a vehicle collision warning system or the like.

[0002]

2. Description of the Related Art As a detection range of an optical radar system mounted on a moving body such as a vehicle, a maximum detectable distance of about 200 m and a maximum detectable width of about 4 m are desired. Due to the limit of the maximum light-receiving sensitivity of the light-receiving element, it is difficult to realize the above-described detection range with one light beam having a fixed radiation direction.

Therefore, it is possible to secure a necessary detection range by radiating a plurality of light beams whose directions are slightly deviated, but in this method, as the number of beams increases, the light emitting element and its peripheral circuits are The number increases, and it becomes large and expensive. As a remaining method, it is possible to scan with one light beam. As a method of scanning this light beam, an optical head including a light transmitting / receiving system is rotated,
A method of rotating a reflecting mirror such as a polygon mirror installed in a fixed light transmitting system is known.

[0004]

In the scanning method of the light beam for rotating the optical head, the rotating mechanism is large and expensive because the head including the light transmitting / receiving system is large, and the power consumption is also increased. There is a problem of doing. Also, in the method of rotating the reflecting mirror installed in the light transmission system,
In that the reflector such as a polygon mirror becomes large,
It has the same drawbacks as the method of rotating the entire optical head described above. Therefore, the problem to be solved by the present invention is to realize an optical head of an optical radar system which is small in size, inexpensive, and has a low power consumption beam scanning function.

[0005]

An optical head of an optical radar system according to the present invention includes a light-transmitting lens and a light-receiving lens installed in front of a light-emitting element and a light-receiving element, and the light-emitting element and the light-transmitting lens. And scanning means for alternately changing the relative position of the light receiving element and the light receiving lens in the plane substantially perpendicular to the optical axis of each lens in substantially the same direction and with substantially the same amplitude.

[0006]

As shown in FIG. 4A, the light emitting element and the light receiving element are represented by points P and Q, respectively, for convenience of description, and a light transmitting lens L1 and a light receiving lens L2 are arranged in front of each of them. It shall be. The light emitting element P and the light receiving element Q are near the focal positions of the light transmitting lens L1 and the light receiving lens L2, respectively, and the optical axes of the lenses L1 and L2 are substantially parallel.

As shown in FIG. 4B, with the light emitting element P and the light receiving element Q fixed, the lenses L1 and L2 are moved by the same distance δ in the same direction (directly above in this example) in the figure. Then, the line connecting the light emitting element P and the center of the lens L1 and the line connecting the light receiving element Q and the center of the lens L2 are inclined by the same angle φ with respect to the optical axes of the lenses L1 and L2, respectively. Accordingly, the light beam emitted from the light emitting element P is swung upward by φ as compared with the case of (A), and
The field of view of the light receiving element changes by the same angle φ as compared with the case of (A).

As described above, the light-transmitting element P and the light-receiving element Q are fixed, and the light-transmitting and light-receiving lenses L1 and L2 are moved in the same direction by the same distance in the plane perpendicular to the respective optical axes. By doing so, the same scanning as that of rotating the entire optical head including the light emitting / light receiving element and the light transmitting / light receiving lens is performed. On the contrary, with the light-sending lens L1 and the light-receiving lens L2 fixed, the light-emitting element P and the light-receiving element Q are at the same distance in the same direction in the plane perpendicular to the optical axes of the lenses L1 and L2. Even if the optical head is moved only by the same amount, the same scanning as when the entire optical head is rotated is performed.

With such translation of the lens or the optical element in the direction perpendicular to the optical axis, a positional shift occurs between the optical element and the focal point of the lens, which causes blurring. Therefore, the principle of the present invention that the scanning of the beam by the rotation of the entire head is substituted by the translation of the lens or the optical element is practical only when the scanning angle is relatively small. By the way, in a vehicle-mounted laser radar, etc., the lane width is ± 2 m ahead of about 10 m.
Since it suffices to scan over a range of about 10 degrees, a beam scanning angle of about ± 12 ° is sufficient. As described above, the principle of the present invention is particularly suitable for a vehicle-mounted laser radar or the like having a relatively small beam scanning angle.

As described above, under the condition that the scanning angle is small, the relative position of the light emitting element and the light transmitting lens and the relative position of the light receiving element and the light receiving lens are surfaces substantially perpendicular to the optical axis of each lens. By alternately changing in the same direction and with the same amplitude, it is possible to perform the same scanning as when the entire head is rotated. Generally, a mechanism for moving only a lens or an element is much smaller and simpler than a mechanism for rotating the entire head or a mechanism for rotating a reflecting mirror, and consumes much less power. In this regard,
A description will be given together with the following examples.

[0011]

1 is a perspective view showing the structure of a main part of an optical head of an optical radar system according to an embodiment of the present invention. The printed wiring board 10 is provided in an appropriate housing (not shown).
Is fixed, and a light emitting element 11 such as a semiconductor laser and a light receiving element 12 such as an APD are fixed on the surface thereof while keeping a predetermined distance. This printed wiring board 10
A lens holding plate 20 is disposed substantially in front of the lens holding plate 20, and a light transmitting lens 21 and a light receiving lens 22 are fixed in respective lens barrels in a central portion of the lens holding plate 20 while maintaining a predetermined distance therebetween. ing. The printed wiring board 10 and the lens holding plate 20 are provided in a housing (not shown) so that the light emitting element 11 is arranged near the focal point of the light transmitting lens 21 and the light receiving element 12 is arranged near the focal point of the light receiving lens. Positioned relative to each other.

A longitudinally elongated elliptical through hole 23 is formed in the right end portion of the lens holding plate 20, and the lens holding plate 20 is movably held left and right by pulleys 34, 35, 36 and 37 fixed to the housing. To be done. A rod-shaped body 35 is provided in the through hole 23.
Is inserted, and the root portion of the rod-like body 35 is fixed to the peripheral portion of a rotating disk 37 axially attached to the rotating shaft of the step motor 38. This rotating disk 37
A small permanent magnet is embedded at a predetermined position on the outer peripheral surface of the rotation sensor 39, and a rotation sensor 39 is installed to detect the rotation angle of the rotating disk 37 by detecting the passage of the permanent magnet using a Hall element or the like. ing.

With the rotation of the pulse motor 38, the tip of the rod-shaped body 35 eccentrically attached to the rotary disc 37 moves in a circle. Along with this, the lens holding plate 20 vibrates to the left and right, and the light transmitting lens 21 and the light receiving lens move in the same direction and the same distance in the plane perpendicular to their respective optical axes. Scanning of the beam and the field of view is performed. When the focal lengths of the lenses 21 and 22 are about 20 mm and the scanning angle is about ± 12 °, the maximum amplitude of lateral vibration is about ± 4 mm.

FIG. 2 is a perspective view showing a structure of a main part of an optical head of an optical radar system according to another embodiment of the present invention. In this figure, the constituent elements denoted by the same reference numerals as those in FIG. 1 are the same as the constituent elements already described with reference to FIG. 1, and duplicate description thereof will be omitted.

According to this embodiment, the lens holding plate 20 is
The printed wiring board 10 is held by a back plate 43 which is fixed to the back plate 43 through thin side plates 41 and 42. The rigidity of the side plates 41 and 42 is set to a value that is sufficiently smaller than the rigidity of the lens holding plate 20 or the back plate 43 by setting the thickness thereof to a value smaller than that of the lens holding plate 20 or the back plate 43. It is set.

The function of the side plates of FIG. 2 will be described with reference to the conceptual diagram of FIG. 4. As the lens holding plate 20 vibrates to the left and right, the side plates 41 and 42 bend as shown by the dotted lines. As a result, the lens holding plate 20 also moves back and forth with the left and right vibrations. For convenience of illustration, the backward and forward movement amounts are emphasized compared to the left and right movement amounts, but in reality, the length of the side plate is set so that the distance between the center of each lens and the corresponding optical element is almost constant. The sheath and rigidity are set. As a result, fluctuations in the distance between the light emitting element 11 and the light transmitting lens 21 and the distance between the light receiving element 12 and the light receiving lens 22 are smaller than those in the case of FIG. 1 in which the lens holding plate 20 vibrates only left and right. It is kept at a value and defocus is reduced.

[0017]

Modified Embodiment Although the optical head of the present invention has been described above with reference to two embodiments, many similar embodiments are conceivable within the scope of the present invention. Only the major ones of these examples are listed below.

The printed wiring board 10 is vibrated with the lens holding plate 20 fixed.

The lens holding plate 20 and the printed wiring board 10
The vibration is generated by using a combination of a piezoelectric element and a cantilever or a linear motor.

A configuration in which the relative positions of the optical element and the lens are changed independently for each of the light transmitting system and the light receiving system.

In the embodiment utilizing the bending of the side plates of FIG. 2, by adjusting the rigidity of the side plates 41 and 42 and the weight balance of the lens holding plate 20, the movement of the lenses 21 and 22 can be performed in both the optical axis and the translational direction. A configuration that causes a minute rotation about an axis orthogonal to the. That is, in the state shown by the dotted line in FIG. 4, a slight counterclockwise rotation is generated in the lenses 21 and 22 about an axis perpendicular to the paper surface, thereby reducing the positional deviation between the optical element and the focal point of the lens. Constitution.

[0022]

As described above in detail, in the optical head of the optical radar system according to the present invention, the relative position of the light emitting element and the light transmitting lens and the relative position of the light receiving element and the light receiving lens are set to the light of each lens. Since the scanning means is arranged to alternate in substantially the same direction and with substantially the same amplitude in a plane substantially perpendicular to the axis, it is smaller and cheaper than the conventional device that rotates the entire optical head and the reflecting mirror. Beam scanning with low power consumption can be realized.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of a main part of an optical head of an optical radar system according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a configuration of a main part of an optical head of an optical radar system according to another embodiment of the present invention.

FIG. 3 is a conceptual diagram for explaining a function of a side plate of the embodiment of FIG.

FIG. 4 is a conceptual diagram for explaining the principle of the present invention.

[Explanation of symbols]

 10 Printed wiring board 11 Light emitting element 12 Light receiving element 20 Lens holding plate 21 Light transmitting lens 22 Light receiving lens 23 Elliptical groove 37 Rotating disk 38 Step motor 39 Rotation angle sensor 41, 42 Side plate 43 Back plate

Claims (2)

[Claims] 1. A light emitting element, a light receiving element, a light transmitting lens disposed in front of the light emitting element, a light receiving lens disposed in front of the light receiving element, the light emitting element and the light transmitting lens. And scanning means for altering the relative position of the light receiving element and the light receiving lens and the relative position of the light receiving element and the light receiving lens alternately in substantially the same direction and with substantially the same amplitude in a plane substantially perpendicular to the optical axis of each lens. The optical head of the characteristic optical radar system. 2. The optical head according to claim 1, wherein the scanning means holds the light-transmitting lens and the light-receiving lens at predetermined intervals while keeping their optical axes substantially parallel to each other. An optical head for an optical radar system, comprising: a mechanism; and a drive mechanism for vibrating the lens holding mechanism in a direction substantially perpendicular to the optical axis of each lens.