Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Reexamination Certificate
1998-11-04
2001-06-05
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
C250S559380, C250S208100, C396S111000
Reexamination Certificate
active
06242727
ABSTRACT:
This application is based on application Ser. No. H09-318020 filed in Japan, the content of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a distance detector used for automatic focusing in silver halide film cameras, video cameras and still video cameras (SVC).
2. Description of the Prior Art
Conventional examples of such a distance detector include one that performs distance measurement in one line of distance measurement area
61
horizontal to a taking image plane
60
of a camera as shown in FIG.
1
. The distance measurement sensor provided in the conventional distance detector is configured, for example, as shown in
FIG. 2. A
pair of line sensors
75
and
76
are disposed on the left and the right with a control circuit
10
in between. The line sensors
75
and
76
are situated substantially on the imaging planes of a pair of lenses disposed with a predetermined distance between the optical axes thereof. The line sensors
75
and
76
sense subject image light by means of light sensing arrays
12
comprising a plurality of light sensing elements.
Photocharges generated in the light sensing arrays
12
are successively transferred and output for each pixel by processors
11
in response to a clock supplied from the control circuit
10
. Based on the output from the distance measurement sensor, a microcomputer calculates the distance to the subject.
In a distance measurement sensor shown in
FIG. 3
, a pair of line sensors
77
and
78
are disposed on the left and the right so as to have the same function as that of the above-described distance measurement sensor (FIG.
2
). Processors
31
are disposed for each pixel on both sides with the light sensing arrays
12
in between.
However, in the above-described conventional distance detectors, since the distance measurement area
61
merely crosses the central portion of the taking image plane
60
as shown in
FIG. 1
, distance measurement cannot be performed when the subject
62
is situated in the lower part or in the upper part of the image plane
60
.
In order to ensure the measurement of the distance to the subject
62
, a configuration as shown in
FIG. 4
is considered in which a plurality of lines of distance measurement areas
63
to
65
are provided so that distance measurement can be performed in a wider range. In this configuration, the shorter the distance D
1
between the distance measurement areas
63
to
65
which the line sensors face is, the more distance measurement areas can be provided in the taking image plane
60
and the more the detection of the subject
62
is ensured. Since the subject
62
can be detected by use of a multiplicity of line sensors, the distance detection accuracy can be improved.
Distance detectors having such a plurality of lines of distance measurement areas include one having a distance measurement sensor configured as shown in FIG.
5
. The distance measurement sensor shown in
FIG. 5
has two pairs of lines sensors
81
to
84
and performs distance measurement along two lines.
The distance measurement sensor has the control circuit
10
at a position with respect to which the sensor is symmetrical. The two pairs of line sensors
81
to
84
are arranged so that the light sensing arrays
12
and the processors
11
accompanying them are oriented in the same direction. In the line sensors
81
to
84
, reduction in the distance d
7
between the light sensing arrays
12
of the line sensors is physically limited because of the existence of the processors
11
.
When the focal length of the taking system is long in order to obtain a large subject image, as schematically shown in
FIGS. 6A and 6B
, the angle of view G of the taking optical system is generally narrow. In this case, when the distance d
8
between lines sensors
91
to
93
is sufficiently short as shown in
FIG. 6A
, distance measurement can be performed with a distance measurement distance D
2
on the taking image plane. However, when the distance d
9
between line sensors
94
to
96
is long as shown in
FIG. 6B
, the distance measurement line density decreases because distance measurement with the distance measurement distance D
2
is impossible, so that the distance measurement areas are outside the taking image plane in some cases. As a result, the reliability and the accuracy of the distance to the subject
62
deteriorate.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a distance detector having a plurality of pairs of line sensors wherein the distance between the distance measurement lines is reduced in order to enable reliable measurement of the distance to the subject and to improve the distance measurement accuracy.
To achieve the above-mentioned object, according to the present invention, a distance detector is provided with: an optical system for forming a subject image; a distance measurement sensor having a plurality of line sensors disposed substantially on an imaging plane of the optical system, the plurality of line sensors each having an array of light sensing elements comprising a plurality of pixels for sensing the subject image and an array of processors for processing outputs of the light sensing elements, the plurality of line sensors being arranged so as to be axisymmetrical with respect to a virtual line and so that the arrays of light sensing elements are closer to the virtual line than the arrays of processors; and a distance calculating circuit for calculating a distance to a subject based on an output from the distance measurement sensor.
REFERENCES:
patent: 4368978 (1983-01-01), Tsunekawa et al.
patent: 4571047 (1986-02-01), Hirai
patent: 4910548 (1990-03-01), Taniguchi et al.
patent: 5539493 (1996-07-01), Kusaka
Burns Doane , Swecker, Mathis LLP
Le Que T.
Luu Thanh X.
Minolta Co. , Ltd.
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