Rangefinder device and camera

Details Rangefinder device and camera Rangefinder device and camera

2001-08-22

2003-02-18

Buczinski, Stephen C. (Department: 3662)

Optics: measuring and testing

Range or remote distance finding

Triangulation ranging to a point with one projected beam

C356S003070, C396S104000, C396S106000, C396S123000

Reexamination Certificate

active

06522394

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improvements in or to a rangefinder device and a camera which can measure distances based on both an active method and on a passive method.
2. Description of the Related Art
As a rangefinder device provided in a conventional camera, there has been proposed a rangefinder device by Japanese Patent Publication (KOKOKU) No. 5-22843, which uses a so-called active method, and is constructed such that the camera flashes or projects a subject, and when integrating the reflected light, a pair of CCDs arranged like a ring cycle accumulated charges, while a charge rejecting means (hereinafter referred to as “the skim means”) rejects a fixed amount of charges of extraneous-light components other than reflected light by the projection, and the distance to the subject is determined based on the relative value of the receiving position of the reflected light from the subject, using signals from the pair of CCDS.
Another rangefinder device of this kind has been proposed by Japanese Laid-Open Patent Publication (KOKAI) No. 9-196665, which can measure the distance based not only on the active method but also on a passive method using only extraneous light, by turning off the projection and stopping the operation of the skim means.
The above described autofocus optical system is generally provided on an optical axis different from the photographic optical system or the finder optical system. With such a camera, if the focal distance of the taking lens is changed, the ranging frame in the finder deviates from the actual ranging area. In such a case, if the distance is measured according to the passive method with a main subject present within the ranging frame and with an object present outside the ranging frame, the object being at a different distance from the main subject, the result of the distance measurement is affected by the object located outside the main subject. That is, a so-called conflict between far and near objects may occur.
Thus, Japanese Laid-Open Patent Publication (KOKAI) No. 2-293833 has proposed a camera which executes ranging calculations using only a part of pixel data that corresponds to the ranging frame out of the actual ranging area, depending on the focal distance.
However, with the rangefinder device that can use both the active and passive methods (hereinafter referred to as “the hybrid rangefinder device”) as disclosed in Japanese Laid-Open Patent Publication (KOKAI) No. 9-196665, if such control as proposed by Japanese Laid-Open Patent Publication (KOKAI) No. 2-293833 is executed, a sensor for use in a ranging operation has a reduced light receiving area on a long focal distance side. Thus, the active method can only deal with a reduced range of distances to which the camera can be adapted, thus making it impossible to carry out measurement of the distance to a subject located at a short distance. This phenomenon will be described with reference to FIG.
10
.
In
FIG. 10
, reference numerals
201
and
202
denote a first light receiving element CCD (L) and a second light receiving element CCD (R), respectively. Reference numerals
203
and
204
denote light receiving lenses with their principal points arranged at a fixed interval (baseline length) B. Reference numeral
205
denotes an infrared light emitting diode (hereinafter referred to as “the IRED”) as a projecting element, and reference numeral
206
denotes a projecting lens. The IRED
205
and the projecting lens
206
form projecting means. Reference numeral
207
denotes a subject.
In the figure, the distance from the principal points of the light receiving lenses
203
,
204
to the CCD
201
,
202
is defined as f, and the distance from the principal points of the light receiving lenses
203
,
204
to the subject
207
is defined as H. The interval (baseline length) between the principal points of the light receiving lenses
203
and
204
is defined as B, and the interval between the principal points of the projecting lenses
206
and the light receiving lens
203
is defined as K.
Further, assuming that the distance by which a received light image moves from a central position of reflected light observed when the subject
207
is located at a point at infinity and if reflected light therefrom is collected by the light receiving lens
203
and then formed into an image on the CCD
201
, to a central position of reflected light observed when the subject
207
is located at the above distance H and if reflected light therefrom is collected by the light receiving lens
203
and then formed into an image on the CCD
201
is defined as X
1
, and the distance by which the received light image moves from a central position of reflected light observed when the subject
207
is located at the point at infinity and if reflected light therefrom is collected by the light receiving lens
204
and then formed into an image on the CCD
202
, to a central position of reflected light observed when the subject
207
is located at the above distance H and if reflected light therefrom is collected by the light receiving lens
204
and then formed into an image on the CCD
202
is defined as X
2
, the following relationship is established:
H=(
B×f
)/(
X
2
−X
1
)  (1)
By determining the denominator (X
2
−X
1
) on the right side of the above Equation (1) using the known phase difference detecting method, the distance to the subject
207
can be calculated.
Here, the distances by which the received light images move on the CCD
201
and the CCD
202
will be explained.
The distance X
1
by which the image moves on the CCD
201
is given by:
X
1
=(
K×f
)/
H
The distance X
2
by which the image moves on the CCD
202
is given by:
X
2
={(
K+B
)×
f}/H
Accordingly, as the light receiving areas of the CCD
201
and the CCD
202
are shorter, the moving distances X
1
and X
2
increase when the distance H to the subject is short, resulting in that the received light images fall out of the light receiving areas of the CCD
201
and CCD
202
. Therefore, to enable measurement of the distance H to the subject over a large range, that is, from a far distance to a close distance, the light receiving areas of the CCD
201
and the CCD
202
have to be sufficiently large.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a rangefinder device and a camera which, in measuring a distance by the active method, are capable of properly measuring the distance even if the object to be measured is located at a short distance, while in measuring a distance by the passive method, are capable of measuring the distance without causing the conflict between far and near objects.
It is another object of the present invention to provide a rangefinder device and a camera which are capable of obtaining highly accurate distance measurement information from both results of the distance measurements executed according to the active method and the passive method.
To attain the above objects, the present invention provides a rangefinder device comprising a projecting section that projects spot-shaped light on a range-finding object, a light receiving section comprising a plurality of photoelectric converting elements, a first calculating section that calculates distance measurement information based on an output from the light receiving section receiving reflected light from the range-finding object, by driving the projecting section to project the light, and a second calculating section that calculates distance measurement information based on an output from the light receiving section receiving extraneous light reflected from the range-finding object, without driving the projecting section, and a control section that sets a light receiving range of the light receiving section used for calculation of the distance measurement information by the second calculating section to be narrower than a light receiving range of the light receiving section used for calculation of the

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