Optics: measuring and testing – Range or remote distance finding – Triangulation ranging to a point with one projected beam
Reexamination Certificate
2000-10-31
2002-01-22
Buczinski, Stephen C. (Department: 3662)
Optics: measuring and testing
Range or remote distance finding
Triangulation ranging to a point with one projected beam
C396S106000, C396S109000, C396S121000
Reexamination Certificate
active
06341012
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rangefinder apparatus for measuring the distance to a target object, and a rangefinding light-detecting device used in the rangefinder apparatus; and, in particular, to an active type rangefinder apparatus employed in a camera or the like, and a rangefinding light-detecting device used in the rangefinder apparatus.
2. Related Background Art
Conventionally known as an active type rangefinder apparatus used in a camera and the like is an automatic focus adjusting apparatus in which, as disclosed in Japanese Patent Application Laid-Open No. HEI 3-156412, light-emitting devices emit three projection light beams toward an object, a position sensitive detector (hereinafter referred to as “PSD”) receives reflected beams of thus emitted projection light beams, and the distance to the object is detected according to a current signal outputted from the PSD.
The above-mentioned automatic focus adjusting apparatus, however, may be problematic in that the rangefinding accuracy becomes lower. Namely, in this automatic focus adjusting apparatus, a single PSD detects the reflected beams of three projection light beams. For example, as shown in
FIG. 24
, the light-detecting area
101
of PSD
100
is divided into three regions according to the number of reflected beams
102
, so that the reflected beams
102
are detected one by one in thus divided regions
103
. In this case, the moving distance d
1
of each reflected beam
102
becomes shorter relative to the length L
1
within which positions are detectable by the PSD
100
. Thus, the current outputted from the PSD
100
changes by a smaller amount when the reflected beam
102
moves. As a consequence, the rangefinding accuracy becomes lower.
On the other hand, a rangefinder apparatus for projecting three projection light beams to an object has been proposed as disclosed in Japanese Patent Application Laid-Open No. HEI 6-317731, which comprises three light-detecting means for independently detecting the respective reflections of the individual projection light beams. This rangefinder apparatus can avoid the problem of the former apparatus that the rangefinding accuracy becomes lower. However, it requires a processing circuit for processing the current signal outputted from each light-detecting means. Consequently, it may be disadvantageous in that the manufacturing cost of the apparatus rises.
In order to overcome such technical problems, it is an object of the present invention to provide a rangefinder apparatus which can improve the rangefinding accuracy and can carry out appropriate rangefinding. It is another object of the present invention to provide a rangefinding light-detecting device to be used in such a rangefinder apparatus, which can be made smaller, at a lower cost, and is easy to adjust in position when used in rangefinder apparatus.
SUMMARY OF THE INVENTION
For achieving such an object, the present invention provides a rangefinder apparatus comprising a plurality of light-projecting means for projecting respective light beams toward a target object; and light-receiving means, disposed at a predetermined distance from the light-projecting means, having a light-receiving region for receiving respective reflected light beams of the light beams projected to the target object, the light-receiving region being shaped substantially as a parallelogram with no rectangular corner.
In the rangefinder apparatus, the light-receiving means may be disposed such that one pair of opposite sides in the light-receiving region of the light-receiving means are parallel to a direction along which the light-receiving means is distanced from light-projecting means, whereas the light-projecting means may be arranged in a row so as to be parallel to the other pair of opposite sides in the light-receiving region.
In the rangefinder apparatus, the light-receiving means may be a position sensitive detector.
According to these aspects of the present invention, since the light-receiving region of the light-receiving means is shaped substantially as a parallelogram having no rectangular corner, the individual reflected light beams can be irradiated in a row along one pair of opposite sides of the light-receiving region, whereby the irradiating positions of the reflected light beams can be moved along the other pair of opposite sides depending on whether the distance to the target object is longer or shorter. Therefore, without dividing the effective light-receiving length of the light-receiving region, rangefinding can be carried out while fully utilizing the effective light-receiving length. Hence, the rangefinding accuracy can be improved.
Also, since the light-receiving region of light-receiving means is shaped substantially as a parallelogram having no rectangular corner, the area of light-receiving region can be made smaller. Therefore, performances against external light can be enhanced, whereby the measurable length can be elongated.
Further, since a single light-receiving means can receive a plurality of reflected light beams, it is not necessary to provide individual output processing circuits for light-receiving means for the respective reflected light beams, whereby a single circuit or the like can carry out signal processing. Therefore, the number of components for signal processing can be made smaller, so that the apparatus can be made at a lower cost.
Also, the present invention provides a rangefinder apparatus comprising light-projecting means for projecting a light beam toward a target object; light-receiving means, disposed at a predetermined distance from the light-projecting means, having a light-receiving region for receiving a reflected light beam of the light beam projected to the target object, the light-receiving region being shaped substantially as a parallelogram having a pair of first opposite sides and a pair of second opposite sides, the first opposite sides extending in a distancing direction along which the light-receiving means is distanced from the light-projecting means, the second opposite sides extending in a direction intersecting the distancing direction at an acute angle; and adjusting means for moving the light-receiving means in a direction orthogonal to the direction in which the second opposite sides extend, so as to adjust a position of the light-receiving means.
The rangefinder apparatus may comprise a plurality of light-projecting means. The light-projecting means may be arranged in a row so as to be parallel to the second opposite sides of the light-receiving region.
According to these aspects of the present invention, if the light-receiving means is moved in a direction orthogonal to the second opposite sides of the light-receiving region so as to adjust the position of light-receiving means, then the adjustable range with respect to shifts in the attaching position of the light-receiving means is enlarged. Therefore, even when the attaching position of light-receiving means shifts greatly, the position of light-receiving means can be adjusted, which enables appropriate rangefinding to be carried out.
Also, since the range of positional adjustment of light-receiving means with respect to shifts in the attaching position of light-projecting means is greater, the position of light-receiving means can be adjusted without increasing the area of light-receiving region. Therefore, the measurable length can be prevented from shortening due to the increase in area of the light-receiving region.
Further, the present invention provides a rangefinder apparatus comprising light-projecting means for projecting a light beam toward a target object; light-receiving means, disposed at a predetermined distance from the light-projecting means, having a light-receiving region for receiving each reflected light beam of the light beam projected to the target object, the light-receiving region being shaped substantially as a parallelogram with no rectangular corner; and light-shielding means formed so as to have no light-receiving sensitivity
Buczinski Stephen C.
Fuji Photo Optical Co., Ltd.
Leydig , Voit & Mayer, Ltd.
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