Photographic camera of automatic focussing type

A photographic camera of automatic focussing type capable of focussing objects between a minimum and infinite distance comprising:

• a movable objective lens;
• a photoelectric focussing detector comprising an image sensor of self-scanning type, said photoelectric focussing detector having a photoconductive element responsive to light rays passing through the objective lens from an object to be photographed, said photoconductive element providing a maximum response when an image of the object formed on the photoconductive element is in the focussed condition, a responsive zone being defined within which the output of the detector varies in accordance with the position of the objective lens and the corresponding degree of focus of the object image and non-responsive zones being defined away from the responsive zone and within which the output of the detector is invariant independent of the position of the objective lens;
• a focussing motor coupled to the objective lens for moving the lens for focussing the image of an object to be photographed;
• a first electrical circuit for determining the direction of movement of the focussing motor for moving the objective lens to focus the object image;
• a second electrical circuit for generating a focussing motor drive signal for causing the motor to rotate at a first speed when the objective lens is in the non-responsive zone, said second electrical circuit for generating a focussing motor drive signal for causing the motor to rotate at a second speed that is less than said first speed when the objective lens is in the responsive zone;
• a scan initiating signal oscillator for providing a scan initiating signal;
• a third electrical circuit coupled to the scan initiating signal oscillator and adapted for controlling the frequency of the scan initiating signal in accordance with the liminance of an object to be photographed and for generating a squarewave output signal in synchronization with the scan initiating signal, such that the duty cycle of said squarewave output signal is varied in accordance with the presence of the objective lens in the responsive and non-responsive zones such that the duty cycle of the squarewave output signal during the presence of the objective lens in the non-responsive zone causes the focussing motor to rotate at the first speed and such that the duty cycle of the squarewave output signal during the presence of the objective lens in the responsive zone causes the focussing motor to rotate at the second speed;
• a first switch adapted to be actuated when the objective lens is at a position for focussing at the infinite distance;
• and
• a second switch adapted to be actuated when the objective lens is at a position for focussing at the minimum distance, said first and second switches coupled to the first electrical circuit such that when either switch is actuated the rotation of the focussing motor is reversed.

In a photographic camera having a translatable lens and a film plane, automatic focussing apparatus comprising:

• a motor connected to the lens to translate the lens for the purpose of focussing an object onto the film plane;
• a light detector for generating an output signal representative of the light passing through the lens onto the film plane;
• means responsive to the light detector for driving the motor to bring the lens in focus;
• and
• means for reducing the speed of the motor as the lens approaches the in focus position.

In a photographic camera having a translatable lens and a film plane, automatic focusing apparatus comprising:

• a motor connected to the lens to translate the lens for the purpose of focusing an object onto the film plane;
• a light detector for generating an output signal representative of the light passing through the lens onto the film plane, the response time of the light detector being a function of the luminance of the object being focused upon;
• means responsive to the light detector for driving the motor to bring the lens in focus;
• and
• means for varying the speed of the motor as a function of the luminance of the object so as to reduce motor speed as the response of the light detector slows.