Photography – With exposure objective focusing means – focusing aid – or... – Temperature compensating
Reexamination Certificate
2002-05-14
2004-03-16
Perkey, W. B. (Department: 2851)
Photography
With exposure objective focusing means, focusing aid, or...
Temperature compensating
C396S100000, C396S104000, C396S114000
Reexamination Certificate
active
06707994
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a focus detecting device which detects the focusing state of an imaging optical system, to a device for determining the amount of focus adjustment for an image-forming optical system, and to an improved imaging device.
2. Description of the Related Art
Focus detecting devices which detect the focusing state of an imaging optical system by comparing images formed by light beams passing through different areas in the imaging optical system are known in the art. In such focus detecting devices, a detection value representing the state of the imaging optical system includes errors caused by variations in ambient temperature and ambient humidity of an image-re-forming optical system used for forming images of each area.
Since temperature sensors are generally used not only for focus detection but also for other purposes, they are often disposed at positions apart from focus detection units. Accordingly, the detection temperature often differs from the actual temperature of an image-re-forming lens installed in a focus detecting device. Therefore, it is difficult to correct errors caused by temperature variation in an image-re-forming lens with high accuracy. Although a method in which an AF sensor containing a temperature sensor is used has been suggested, there is a risk in that the temperature of the image-re-forming lens cannot be accurately detected because of heat diffused from the AF sensor itself.
In addition, as disclosed in Japanese Patent Laid-Open No. 11-109219, a technique is known in which a temperature detection unit is attached to a focus detecting device and the focal position is corrected on the basis of a temperature, which is detected indirectly.
In addition, as disclosed in Japanese Patent Application No. 2000-261496, another technique is known in which a pattern is formed on an optical component and a correction unit corrects information regarding the focusing state of an imaging optical system by detecting the position of the pattern. More specifically, a pattern is placed on a deflecting mirror disposed in the light path of the imaging optical system, and is detected by a detection unit so that changes in the deflecting mirror can be detected.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, a device for determining an amount of focus adjustment for an image-forming optical system which forms an image on a predetermined image plane includes a sensor; an image-re-forming optical system which re-forms the image on the sensor; a reference member disposed at a position close to the predetermined image plane of the image-forming optical system; and a processing circuit which detects a projected image of the reference member by using the sensor and determines the change in the amount of focus adjustment caused by the change in operating environment in which the device for determining the amount of focus adjustment is used.
According to another aspect of the present invention, a device for determining an amount of focus adjustment for an image-forming optical system which forms an image on a predetermined image plane, includes a sensor; an image-re-forming optical system which re-forms the image on the sensor; a reference member included in one of the image-forming optical system and the image-re-forming optical system; and a processing circuit which detects a projected image of the reference member by using the sensor and determines the change in the amount of focus adjustment caused by the change in operating environment in which the device for determining the amount of focus adjustment is used.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments (with reference to the attached drawings).
REFERENCES:
patent: 5572013 (1996-11-01), Ohsawa
patent: 5995766 (1999-11-01), Yamashita
patent: 2002/0044772 (2002-04-01), Yamasaki et al.
patent: 11-109219 (1999-04-01), None
patent: 2002-72071 (2002-03-01), None
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