Metering device for cameras

#1. Field of the Invention

#This invention relates to a metering device for cameras, and more particularly, to a metering device in which the aggravation of photo-responsive characteristic attributable to the capacity present in the light-sensing element has been corrected.

#2. Description of the Prior Art

#Specific embodiments of the invention have been chosen for purposes of illustration and description, and are shown in the accompanying drawing, forming a part of the specification, wherein:

#The FIGURE of the drawing is a circuit diagram showing an embodiment of the present invention.

#Referring to the drawing, which shows an embodiment of the present invention, the anode of a photodiode Dp is connected to the positive input terminal (+) of an operational amplifier 1 biased by a positive voltage +Vc, and the cathode of the photodiode Dp is connected to the negative input terminal (-) of the operational amplifier. A capacity Cd is present in the photodiode Dp and the anode of the photodiode Dp is grounded. The cathode and anode of a logarithmic conversion diode D1 are respectively connected to the negative input terminal (-) and the output terminal O of the operational amplifier 1, thus forming a negative feedback circuit. A capacitor 4 has one pole thereof connected to the terminal 3 of the operational amplifier 1 and the pole connected to a resistor 5 which has one end grounded. A discharging diode D2 has the cathode thereof connected to the junction between the capacitor 4 and the resistor 5, and has the anode thereof connected to the negative input terminal (-) of the operational amplifier 1.

#The terminal 3 of the operational amplifier 1 is led out at a point in the operational amplifier circuit whereat the potential of the operational amplifier varies in synchronism with variations in output potential of the operational amplifier.

#Operation of the shown embodiment will now be described.