Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
1999-06-08
2001-06-12
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S216000
Reexamination Certificate
active
06246051
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of the Invention
The present invention relates to a light beam scanning device which two-dimensionally scans an object region with a light beam such as a laser beam.
2. Related Art
As a device such as a vehicle gap measuring apparatus, known is an apparatus configured by: a light beam scanning device which two-dimensionally scans a certain measuring object region in front of the apparatus with a laser beam; a light receiving device which receives reflected light of the laser beam emitted from the light beam scanning device; and a calculation device which calculates a vehicle gap on the basis of a light receiving state in the light receiving device. For example, Unexamined Japanese Patent Publication Hei.9-274076 discloses such a vehicle gap measuring apparatus.
A light beam scanning device of the conventional art which is used in a vehicle gap measuring apparatus is structured in the following manner. Pulse light from a light source such as a laser diode is passed through a collimating lens to be emitted as a light beam. The light beam impinges on light deflecting means which is swung in a constant angle range, specifically a reflector plate or a rotating polygon mirror. A measuring object region in front of the apparatus is two-dimensionally scanned by using a reflected beam from the means. In the vehicle gap measuring apparatus disclosed in the patent publication, for example, two-dimensional scanning of a light beam is conducted by using a polygon mirror.
As described above, in a light beam scanning device of the prior art, a light beam is deflected by swinging a reflector plate or rotating a polygon mirror, so as to conduct a scanning operation in a constant angle range. Deflecting means such as a reflector plate requires a larger installation space than other components. This largely impedes miniaturization of a light beam scanning device.
In a light beam scanning device of the prior art, irradiation of a light beam is pulsatingly conducted in synchronization with the scanning angle. When the irradiation (emission) timing of a light beam is shifted from the rotational angle position (scanning angle) of a reflector plate or a polygon mirror, there arises a disadvantage that it is impossible to scan the whole of a measuring object region without omission. In order to prevent such a disadvantage from occurring, conventionally, the reflector plate or the polygon mirror is driven while maintaining accurate linearity with respect to the irradiation timing of the light beam. Therefore, a mechanism for driving the reflector plate or the polygon mirror must be provided with positional accuracy of a high resolution.
SUMMARY OF INVENTION
In view of these problems, it is a first object of the invention to provide a small and compact light beam scanning device which can conduct scanning of a beam such as a laser beam in a constant angle range without requiring a reflector plate, a polygon mirror, or other light deflecting means.
It is a second object of the invention to provide a light beam scanning device which can adequately conduct scanning of a beam without using a driving mechanism provided with positional accuracy of a high resolution.
An aspect of the present invention, there is provided a light beam scanning device for scaning an object region in a predetermined direction with a light beam, comprising:
a light source emitting the light beam;
a collimating lens through which the light beam from said light source is allowed to pass; and
a swinging mechanism swinging said collimating lens in a predetermined angle range,
wherein a main optical axis of the light beam from said light source is positioned in a same plane as an optical axis of said collimating lens obtains when said collimating lens is swung, a swing center axis of said collimating lens due to said swinging mechanism is positioned on an extension of an optical axis of the light beam which is on a side of said light source with respect to said collimating lens, and said collimating lens is swung along the plane by said swinging mechanism.
As described above, in the light beam scanning device of the invention, the collimating lens is placed in front of the light source placed at a fixed position in the emission direction, and the collimating lens is directly swung in a constant angle range.
According to the invention, therefore, a reflector plate or a polygon mirror which is required in the prior art is not necessary, and hence the device can be compactly configured in a very small size.
The light source is placed at or in the vicinity of the swing center of the swinging mechanism and the lens which is driven by the mechanism. As compared with the configuration of the prior art in which a light source is placed outside a swing locus of a swinging mechanism having a reflector plate or a polygon mirror, therefore, the space required for placing such components can be reduced, and hence the whole of the device can be compactly configured in a further small size.
REFERENCES:
patent: 5498869 (1996-03-01), Appel et al.
patent: 35 31 666 A1 (1987-03-01), None
patent: 196 26 298 A1 (1998-01-01), None
patent: 0 249 642 A1 (1987-12-01), None
patent: 0 935 142 A2 (1999-08-01), None
patent: 9-274076 (1997-10-01), None
Japanese Abstract No. 61-175614, dated Aug. 7, 1986.
Kabushiki Kaisha Sankyo Seiki Seisakusho
Le Que T.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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