Photography – With exposure objective focusing means – focusing aid – or... – Optical detail with photoelement system
Reexamination Certificate
2000-04-28
2001-09-04
Adams, Russell (Department: 2851)
Photography
With exposure objective focusing means, focusing aid, or...
Optical detail with photoelement system
C396S106000, C396S123000
Reexamination Certificate
active
06285832
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor photo detector element such as a silicon photo diode (SPD) and a position sensitive device (PSD), distance measuring equipment for measuring a distance up to a target to be measured in distance using the semiconductor photo detector element, and a camera using the semiconductor photo detector element.
2. Description of the Related Art
There is widely spread a camera incorporating thereinto an automatic focusing (AF) device, which is generally referred to as an active type. Such an active type of automatic focusing device adopts a system for measuring a distance up to a camera subject in such a manner that an AF light projection unit and an AF photo detection unit are disposed at intervals of a predetermined base length, light is projected from the AF light projection unit to the camera subject, and light reflected on the camera subject is detected by the AF photo detection unit. As a photo detector element for focusing, for example, a semiconductor element, such as an SPD element and a PSD element, is used. By way of example, Japanese Patent Application Laid Open Gazette Sho. 57-22508 discloses a system in which a PSD element is used to perform focusing. In some cases, a camera is provided with an automatic flash emission device (an automatic electronic flash device), in which at the time of a photography, a flash is projected to a camera subject, a reflected light from the camera subject is detected, and a flash emission is stopped at a timing that the reflected light reaches a predetermined light quantity, and a remote control device for instructing an execution of an operation (for example, a self-time operation) according to a received light from a remote control equipment (for example, for a self-timer) for controlling the camera in accordance with an emission of light is directed to the camera, as well as an automatic focusing device. In such a case, in the camera, the automatic electronic flash device and the remote control device are provided with semiconductor photo detector elements represented by the SPD element, in addition to the semiconductor photo detector elements represented by the SPD element, in addition to the semiconductor photo detector element for the automatic focus (AF).
FIG. 9
is a diagram of semiconductor photo detector elements incorporated into the respective devices and their associated circuits, with respect to the conventional camera.
In
FIG. 9
, there is shown a PSD
61
, which is one example of the semiconductor photo detector element for the automatic focus (AF), and an AF-dedicated photo detector circuit
62
, which are provided in an automatic focusing device; and an SPD
63
provided in another device and a dedicated photo detector
64
for the another device. The AF-dedicated photo detector
62
and the dedicated photo detector circuit
64
are connected to an MPU (Micro Processor Unit)
65
serving as a control unit. Here, there will be explained a case wherein the camera is provided with an automatic electronic flash device as the “another device”.
The PSD
61
shown in
FIG. 9
generates a photo-current in such a manner that light for focusing is projected from an AF light projection unit (not illustrated) to a camera subject to the light for focusing reflected on the camera subject is detected on a detection surface of the PSD
61
. The photo-current thus generated is separated into photo-currents I
1
and I
2
in accordance with distances between an irradiation position on the detection surface and both ends of the detection surface, respectively, and the photo-currents I
1
and I
2
are fed to the AF-dedicated photo detector circuit
62
. The AF-dedicated photo detector circuit
62
determines a distance up to the camera subject in accordance with both photo-current I
1
and I
2.
The MPU controls a driving lens for focusing in accordance with the distance thus determined.
On the other hand, the SPD
63
detects the reflected light from the camera subject through the flash projected to the camera subject from an automatic electronic flash device at the time of photography. A photo-current I
3
generated through the detection by the SPD
63
conducts via the dedicated photo detector circuit
64
. The dedicated photo detector circuit
64
integrates the photo-current I
3
and outputs a signal to stop the flashing operation of the automatic electronic flash device in the timing that the integrated photo-current I
3
reaches a predetermined quantity of reflected light. This signal is transmitted to the MPU
65
as well as a flash emission stop control unit (not illustrated). The MPU
65
performs a control of shutter closing and the like in accordance with this signal.
As mentioned above, in some case, the conventional camera is provided with an automatic electronic flash device and a remote control device as well as an automatic focusing device. In such a camera, although the photo detection wavelengths of those devices are mutually closed, those devices are individually provided with their dedicated photo detector elements. Thus, the conventional camera is associated with a problem that the number of photo detector elements is increased, and as a result a circuit scale is enlarged. Accordingly, there is also a problem that the cost is increased.
Further, there is proposed a technology (cf. Japanese Patent Application Laid Open Gazette Hei. 7-260475) in which instead of the AF-dedicated photo detector circuit
62
, the signal of the photo-current is subjected to an A/D conversion and then is operated. However, also in accordance with this technology, the number of photo detector elements is large. This technology is also associated with a problem that the cost is increased.
In order to solve those problems, it is considered that one semiconductor photo detector element is used on a common basis for the automatic focusing device and another device. However, control and processing method for photo detection signals in the automatic focusing device are different from those in another device, for example, an automatic electronic flash device. Therefore, it is difficult for another device to use an AF-dedicated photo detector circuit for processing photo-current from the semiconductor photo detector element as a photo detector circuit as it is.
Further, the camera incorporated therein an automatic focusing device is also associated with an additional problem that as to focusing for distance, an accuracy of focusing is lowered.
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the present invention to provide a semiconductor photo detector element suitable for implementing a camera capable of enhancing an accuracy of focusing and/or reducing a cost with a small scale of circuit, a distance measuring equipment adopting such a semiconductor photo detector element, and a camera using the semiconductor photo detector element.
To achieve the above-mentioned object, the present invention provides a semiconductor photo detector element comprising:
a detection surface for generating a photo-current upon receipt of irradiation of light;
a pair of signal electrodes, disposed at both ends of said detection surface, adapted for outputting on a share basis the photo-current generated by irradiation of light onto said detection surface; and
a first switch, disposed at a position adjacent to one signal electrode which is one of said pair of signal electrodes, for selectively offering a first state which permits the photo-current generated on said detection surface to conduct into said one signal electrode, and a second state which inhibits the photo-current generated on said detection surface from conducting into said one signal electrode, in accordance with a control signal.
According to the semiconductor photo detector element of the present invention as mentioned above, there is provided the first switch disposed at a position adjacent to one signal electrode which is one of said pair of signal electrodes. This feature makes it p
Ishii Shuichi
Kotani Takaaki
Ushiro Seimei
Adams Russell
Blackman Rochelle
Fuji Photo Film Co. , Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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