초록 ▼

A focus detecting device for a camera is disclosed which employs a CCD for producing an image signal carrying focus information. A monitoring circuit has a charge storing circuit for storing the charge generated from a light receiving element, so that the monitoring circuit monitors the amount of li

A focus detecting device for a camera is disclosed which employs a CCD for producing an image signal carrying focus information. A monitoring circuit has a charge storing circuit for storing the charge generated from a light receiving element, so that the monitoring circuit monitors the amount of light received from the target object to be photographed and produces a charge signal representing the monitored amount. A reference signal generator is provided for producing a reference signal. Since the reference signal generator is defined by the same circuitry as the charge storing circuit, undesirable fluctuation in the charge signal will also be seen in the reference signal. Since undesirable fluctuation in both signals can be counterbalanced with each other, the comparison between the charge signal and the reference signal can be done with high accuracy.

대표청구항 ▼

A focus condition detecting device for a camera having an objective lens, said device comprising: an optical system arranged to receive light from an object through said objective lens and to form object images whose intensity distributions vary with the focus condition of said objective lens; a sel

A focus condition detecting device for a camera having an objective lens, said device comprising: an optical system arranged to receive light from an object through said objective lens and to form object images whose intensity distributions vary with the focus condition of said objective lens; a self scanning type image sensor having a shift register and a plurality of photosensitive elements arranged to receive said object images, each of said photosensitive elements being capable of storing electric charges at a speed dependent upon the intensity of light impinging thereon; means for generating a clear pulse which causes said image sensor to clear the electric charges stored in said photosensitive elements, said photosensitive elements starting the storage of the electric charges in response in disappearance of said clear pulse; means for generating a shift pulse which shifts the stored electrical charges to said shift register; means for generating transfer pulses which cause said shift register to transfer the shifted electrical charges therein and to generate them as outputs in a serial manner; means for converting the outputs of said shift register into picture element signals which constitute a video signal representative of said intensity distributions each time said shift register generates its output; means for processing said video signal in accordance with a predetermined program to generate a signal representative of the focus condition of said objective lens; means for detecting the brightness of said object; a monitor circuit having an input terminal connected to said directing means, said monitor circuit including first charge storing means connected to said input terminal and a first buffer circuit connected to said first charge storing means and having high input impedence and low output impedence, and said first charge storing means storing electrical charge at a speed dependent on the brightness of said object detected by said detecting means in response to the disappearance of said clear pulse so that said first buffer circuit generates a time varying output which varies with the advance of the storage of the charge by said first charge storing means while said first charge storing means is cleared in response to said clear pulse so that the output of said first buffer circuit is restored to a given initial voltage level; a reference output generating circuit having an open output terminal, said reference output generating circuit including second charge storing means connected to said open input terminal and having the same characteristics as said first charge storing means and a second buffer circuit connected to said second charge storing means and having the same characteristics as said first buffer circuit, and said second charge storing means being cleared in response to said clear pulse and maintaining the cleared state even after the disappearance of said clear pulse so that said second buffer circuit constantly generates a reference output which is at said given initial voltage level; a first comparator comparing said time varying output of said first buffer circuit with said reference output of said second buffer circuit to invert its output when the former output represents a given relationship with respect to the latter output; and shift pulse generation control means for causing said shift pulse generating means to generate said shift pulse in response to the inversion of the output of said first comparator.