JPH0670567B2 - Detection optics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is directed to receiving reflected light from an object.
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a detection device for detecting the presence of an object and a distance to the object, and more particularly to improvement of a light receiving optical device for that purpose.

[Conventional technology]

Conventionally, there is known a device which detects the presence of an object by irradiating a light beam toward the area and detecting reflected light from the object existing in the area in order to detect the distance to the object in the area. Has been. For example, in a device that monitors an angle range of ± 45 ° with respect to the front direction, as shown in the plan view of FIG. 1 and the side view of FIG. 2, a detection unit for a fan-shaped area is provided. The detection unit 1 includes an irradiation device 2 that irradiates a light beam 6 from a monitoring point and a light receiving device 3 that condenses the reflected light 5 from the object O onto a light receiving element. Therefore, the presence or absence of the object O can be detected by the signal from the light receiving element, and the distance to the object O can be detected by the position of the condensing point on the light receiving element. By doing so, it is possible to recognize the movement of the object.

[Problems to be Solved by the Invention]

In such a detection device, in order to increase the efficiency as much as possible, the detection unit should be in the horizontal plane (in the sagittal plane).
It is necessary to widen the range of monitoring that is undertaken by. Moreover, since the reflected light flux from the object is generally extremely weak, it is of course necessary to increase the output of the irradiation light, but it is necessary to improve the light collection efficiency of the light receiving device and the accuracy of the distance detection to the object. In order to increase the size, it is important to make the focused spot size as small as possible.

However, it is difficult to collect the reflected light from an object in a wide range with a small spot size, and it is extremely difficult to detect the object distance efficiently and with high sensitivity and accuracy by a small device.

An object of the present invention is to detect the existence of an object over a wide range and the distance to the object, and further, the light collection performance of the light collection optical system is excellent, and efficient light collection is possible and highly sensitive object detection. Another object of the present invention is to provide a small-sized detection optical device capable of performing highly accurate object distance detection.

[Means for Solving the Problems]

The detection optical device according to the present invention has a condensing optical device for receiving light from an object to be inspected located in a predetermined plane, and the condensing optical device converges in a plane perpendicular to the plane. Two first and second columnar concave reflecting surfaces having an action, and the two
A light receiving element disposed on the focal plane by two columnar concave reflecting surfaces, and a light beam incident on the condensing optical device is reflected by the first columnar concave reflecting surface and then by the second columnar concave reflecting surface. The light-receiving element on the focal plane is focused.

The center of curvature of the first columnar concave reflection surface is located on the opposite side of the reflection region of the first columnar concave reflection surface with respect to the reflection region of the second columnar concave reflection surface. Is arranged at a position farther from the incident surface of the condensing optical device with respect to the reflection area of the first columnar concave reflection surface.

〔Example〕

Hereinafter, the present invention will be described based on examples. FIG. 3 is a perspective view showing a schematic configuration of an optical system of the detection optical device according to the present invention. By an irradiation optical device (10) having a laser light source (11) such as a semiconductor laser and a projection lens (12),
The laser beam (L) is projected in a fan shape in a horizontal plane (xy plane). Illumination optical devices include, for example, JP-A-50-156956.
It is effective to use a ring type lens system having a toric surface as disclosed in Japanese Patent Laid-Open Publication No. A condensing optical device (20) having a prism P and a light receiving element (27) is provided above the irradiation optical device, and the optical axis 1 of the irradiation optical device and the optical axis m of the condensing optical device are provided. It is configured to be parallel to each other and included in the same vertical plane (yz plane). If any object (0) exists in the optical path of the projected light flux, the laser light is scattered and reflected by this object, and a part of the scattered light reaches the condensing optical device (20) and is condensed. The prism P of the condensing optical device (20) has an entrance surface (21) and a first inner concave reflection surface as shown in the sectional optical path diagram in the vertical plane (yz plane) of FIG. 4, that is, in the meridional plane. A cylindrical convex surface (22), a second internal concave reflecting surface as a cylindrical convex surface (23), and a focal plane as an exit surface (24),
The light receiving element (27) is joined to the exit surface (24).
The first reflection surface (22), the second reflection surface (23), and the both side surfaces (25, 26) of the prism P are each formed as a reflection surface having a high reflectance by vapor deposition of silver or the like. It should be noted that, as shown by the dotted line in FIG. 4, the prism P is formed separately on the first reflection surface (22) side and the second reflection surface (23) side, and is then configured to be bonded, which is easy to manufacture. desirable. The exit surface (2
Since 4) functions as a focal plane, it is desirable that it be formed so as to be perpendicular to the optical axis m of the condensing optical device.

With such a configuration, the meridional component of the reflected light flux from the object that enters the prism P of the condensing optical device (20) passes through the incident surface (21), and then the first reflection surface (22) and The light is converged on the exit surface (24) by the converging action of each cylindrical concave reflection surface on the second reflection surface (23). The component of the sagittal direction in the light flux reflected from the object, after passing through the incident surface (21), is simply reflected by the first reflecting surface (22) and the second reflecting surface (23), respectively, and exited (24 ) Is reached. For this reason, a light beam incident on the prism P from a wide angle range in the horizontal plane (xy plane) is as shown in the development optical path diagram in the horizontal plane (xy plane) of the prism P shown in FIG. 5, that is, in the sagittal plane. , After being refracted at the entrance surface (21),
The light is reflected by the side surfaces (25) and (26) and reaches the light receiving element (27) on the exit surface (24).

Therefore, the light flux reflected from the object incident on the prism P of the condensing optical device (20) is collected as a linear light flux parallel to the generatrix (x direction) of the cylindrical surface on the exit surface (24) as a focal plane. Be illuminated. The width of this linear light beam corresponds to the size of the focused spot of the prism P in the meridional direction, and the position of this spot in the meridional plane corresponds to the distance to the object. That is, when an object is present in the vicinity, as shown in the meridional direction sectional optical path diagram of FIG. 4, the reflected light flux from the object is incident on the incident surface (21) at an incident angle θ, so that the focused spot is Exit surface (24)
It approaches the incident surface (21) side above. Then, the optical axis m as the condensing optical device and the exit surface (24) as the focal plane are shown.
The distance d from the intersection (30) with the position (31) of the focused spot corresponds to the object distance. Now, this condensing prism P
When the focal length of is defined as f, the relationship of d = f · tan θ is established. Further, if the distance between the optical axis 1 of the irradiation optical device and the optical axis m of the condensing optical device is H, then for the object distance D, the relationship of tan θ = H / D holds, so the object distance D is D = It is obtained from the relationship of f · H / d. Therefore, the distance to the object can be obtained by measuring the position of the linear light beam condensed on the light receiving element (27), that is, the spot position on the meridional plane.

Since the cylindrical concave reflection surface formed on such a prism P employs a cylindrical concave reflection system instead of a refraction imaging system such as a cylindrical positive lens, a luminous flux from a wide angle range in a horizontal plane can be efficiently formed. Moreover, it is suitable for compact focusing. In addition, there is no unavoidable tendency of a cylindrical lens in which an off-axis straight line parallel to the generatrix direction of a cylinder is deformed to form an image, and the straight line is accurately reproduced as a straight line. It is effective in improving accuracy.

However, since the cylindrical concave reflecting surface is composed of an eccentric system, coma aberration is remarkable in the meridional direction. When the coma aberration is large, the spot size of the condensed light beam cannot be reduced, so that the detection accuracy of the distance to the object is unavoidable. For this reason, in the present invention, the two cylindrical concave reflecting surfaces are combined as described above to collect the reflected light flux from the object, and thereby the coma aberration is reduced and the focused spot size is made extremely small. Therefore, it is possible to dramatically improve the accuracy of detecting the object distance.

Hereinafter, with respect to the light converging performance in such meridional direction, a converging prism having only one cylindrical concave reflecting surface and a condensing prism having two cylindrical concave reflecting surfaces are compared with a focal length f = 100 mm. This will be specifically described.

FIG. 6 shows a condensing prism P ₁ having only one cylindrical concave reflection surface.
FIG. 3 is a sectional optical path diagram in the meridional direction of FIG. Incident surface (3
The light flux incident from 1) is reflected by the cylindrical concave reflection surface (32) as the first reflection surface, is reflected by the flat surface (33) as the second reflection surface perpendicular to the incidence surface (31), and is used as the focal plane. Reaching the exit surface (34). Here, the radius of curvature R of the cylindrical concave reflecting surface as the first reflecting surface (32) is 333 mm. If the optical axis of this curved surface is defined as an axis A perpendicular to the incident surface (31), the optical axis A and the optical axis m of the condensing optical device are parallel and the distance S is 167 mm. Optical axis A of cylindrical concave reflecting surface (32)
Along the concave concave reflecting surface (32) from the apex Q of the incident surface (3
The distance T to 1) is arbitrary. In such a condensing prism P ₁ , when a light flux with a width of 62 mm enters perpendicularly to the incident surface (31), that is, parallel to the optical axis m as the condensing optical device, the condensing state is the first. It looks like Figure 7. That is, in the best image plane F, the marginal rays q and r are condensed at a position about 3 mm apart from the principal ray p along the optical axis m,
It is clear that the focused spot size will be quite large.

On the other hand, a concrete example of the condenser prism P ₂ according to the present invention having two cylindrical concave reflecting surfaces is shown in the sectional optical path diagram in the meridional direction of FIG. The light flux incident on the incident surface (41) is converged by the cylindrical concave reflection surface (42) as the first reflection surface and then by the cylindrical concave reflection surface (43) as the second reflection surface. It is focused on the exit surface (44) as a focal plane. Here, the radius of curvature of the cylindrical concave reflecting surface (42) as the first reflecting surface
R ₁ is 586 mm. If the optical axis of the curved surface as the first concave reflecting surface is defined as the axis A ₁ perpendicular to the incident surface (41),
The optical axis A ₁ is parallel to the optical axis m as the condensing optical device, and the distance is 276 mm. The radius of curvature R ₂ of the cylindrical concave reflecting surface (43) as the second reflecting surface is 534 mm. If the optical axis of the second reflecting surface (43) is defined as an axis A ₂ parallel to the incident surface (41), then the second reflecting surface (43) in the present embodiment.
Of which the vertices Q ₁ is positioned in the first reflecting surface on the optical axis A ₂ (42), the distance between the vertex Q ₂ vertices Q ₁ and the second reflecting surface of the first reflecting surface (42) (43) U is 202 mm. Along the optical axis A ₁ of the curved surface as the first reflecting surface, from the vertex Q ₁ of the first reflecting surface to the incident surface (4
The distance T to 1) is also arbitrary in this prism.

In the condensing prism P ₂ having two such cylindrical concave reflecting surfaces, the optical axis as a condensing optical device is similar to the condensing prism P ₁ having only one cylindrical concave reflecting surface shown in FIG. m
Assuming that a light beam having a width of 62 mm parallel to is made incident, the condensed state in the meridional direction is as shown in FIG. As shown in the figure, the marginal rays q and r are condensed at a position slightly separated by about 0.3 mm from the principal ray p along the optical axis m on the best image plane F. Therefore, it is clear that the focused spot size can be reduced to about 1/10 in the case where two concave reflecting surfaces are provided, as compared with the case where only one concave reflecting surface is provided.

In the configuration according to the present invention shown in FIG. 8 above, the first
Center of curvature of the concave reflecting surface (42) of Fig. 8 (the intersection of the extension line of the arrow indicating the radius of curvature R ₁ of the first reflecting surface in Fig. 8 and the optical axis A ₁ )
Is located on the opposite side of the reflection area of the first concave reflection surface (42) with respect to the reflection area of the second concave reflection surface (43), in other words, in FIG. It is necessary that the apex Q ₁ of) is below the second concave reflecting surface (43) in the figure. Further, the center of curvature of the second concave reflection surface (43) (the intersection of the arrow indicating the radius of curvature R ₂ of the second reflection surface in FIG. 8 and each extension line of the optical axis A ₂ ) is the first concave reflection surface. The position is farther from the incident surface (41) with respect to the reflection area of the surface (42), in other words, in FIG. 8, the vertex Q ₂ of the second concave reflection surface (43) is the first.
It is necessary to be at a position (right side) farther from the incident surface (41) with respect to the reflection area of the concave reflection surface (42).

Practically, as in the embodiment of FIG. 8, the radius of curvature R ₂ of the _second concave reflecting surface has a value equal to or smaller than the radius of curvature R ₁ of the first concave reflecting surface, that is, R ₁ ≧ R ₂ Is more desirable for the correction of coma.

The incident surface (41) of the prism P can be a curved surface to increase the degree of freedom of aberration correction, and the exit surface can be a curved surface according to the curvature of the image plane.

In the present invention, the irradiation device is not essential and can be realized by receiving light from an object.

〔The invention's effect〕

As described above, according to the detection optical device of the present invention, it is possible to detect the existence of an object in a wide range and the distance to the object, and further, the condensing optical device is excellent in the condensing performance, and efficient condensing is possible. Therefore, highly sensitive object detection and highly accurate object distance detection can be performed. Moreover, since the condensing optical device can be formed by an integral prism, the number of members is small and the entire device can be made compact.

[Brief description of drawings]

FIG. 1 is a plan view of a monitoring device as a general example of a detection device, FIG. 2 is a side view thereof, FIG. 3 is a perspective view showing a schematic configuration of an embodiment of the detection device according to the present invention, and FIG. Is a sectional optical path diagram in the meridional direction of the prism of the condensing optical device in the present invention, FIG. 5 is a developed optical path diagram of the prism in the sagittal direction, and FIG. 6 is a comparative example of a prism having one concave reflecting surface. FIG. 7 is a cross-sectional optical path diagram, FIG. 7 is a view showing a condensed state in the meridional direction, FIG. 8 is a cross-sectional optical path diagram of a comparative example of a prism having two concave reflecting surfaces, and FIG. 9 is a collection in the meridional direction. It is a figure which shows a light state. 1 ... Detection unit, 2 ... Irradiation device, 3 ... Light receiving device, 4 ... Monitoring range (90 °), 5 ... Reflected light from an object, 6 ... Irradiation beam, O ... Object, 10 ... … Irradiation optics, 20 …… Condensing optics, P, P ₁ , P ₂ …… Prism, 27…
… Light receiving element, 22, 23, 32, 42, 43 …… Cylindrical concave reflecting surface.

Continuation of the front page (56) Reference JP-A-57-199909 (JP, A) JP-A-60-73405 (JP, A) JP-A-61-170611 (JP, A) JP-A-62-87808 (JP , A)

Claims (1)

[Claims] 1. A condensing optical device for receiving light from an object to be inspected located in a predetermined plane, the condensing optical device having a converging function in a plane perpendicular to the plane. It has two columnar concave reflecting surfaces and a light receiving element arranged on the focal plane formed by the two columnar concave reflecting surfaces, and the light flux incident on the condensing optical device is reflected by the first columnar concave reflecting surface. Second after
It is configured so that it is reflected by the columnar concave reflecting surface and condensed on the light receiving element on the focal plane, and the center of curvature of the first columnar concave reflecting surface is Located on the opposite side of the reflection area of the first columnar concave reflection surface, the center of curvature of the second columnar concave reflection surface is closer to the reflection area of the first columnar concave reflection surface from the incident surface of the condensing optical device. A detection optical device characterized in that it is arranged at a distant position.