SU885958A1 - Device for automatic focusing of camera lens - Google Patents

Description

(54) DEVICE FOR AUTOMATIC FOCUSING OF THE LENS OF A CAMERA

I

The device relates to a photo kinotekhnike and can be used to create photo and movie cameras with automatic focusing.

A device for autofocusing the lens of a camera is known, which contains an electric motor that engages with a lens through a gear and is controlled by a laser range finder 1.

A camera with such a device is characterized by a high complexity of the technical implementation associated with the presence of a laser range finder. In addition, it does not provide accurate autofocus.

The closest to the present invention is a device for automatically focusing a camera lens, which contains a $ 1 electroacoustic converter with an amplifier, a time-pulse converter consisting of a series-connected trigger, a logic element And and a counter, an electric motor connected through a gearbox to the lens M the camera and lens angle converter R are the number of pulses as well as the trigger mechanism, and the input

electroacoustic transducer is connected to the trigger output, and the output is through an amplifier with one of the trigger inputs and c. engine, while the second trigger input is associated with the trigger 2).

However, this device with an ultrasonic rangefinder does not provide accurate focusing.

The purpose of the invention is to improve the accuracy of focusing.

This goal is achieved by introducing an additional electroacoustic converter with a reflector installed at a fixed distance from it, a second amplifier and a logic element OR, connected to the input of an additional electroacoustic converter,

the output of which is connected via an amplifier with the input of the logical element AND and the input of the logical element OR, the second input of which is connected to the output of the trigger.

The drawing shows a device diagram with: tva.

Claims (2)

The device contains a camera lens 1, which, through a gearbox 2, is connected to an electric motor 3 and a counting wheel 4. Trigger 5, measuring electrical transducer 6 with amplifier 7, trigger 8, logic element AND 9, counter 10, logic element OR 11, reference electro-acoustic transducer 12 with amplifier 13, transducer 14 of the angle of rotation of the lens. a, in the number of pulses and the reflector 15. The device works, as follows, the image directs the lens to the object, combines the area delineated in the viewfinder Barely (this zone in the viewfinder on the object corresponds to the zone of irradiation with the KOBbijM locator), with the object that needs to be focused on the film and presses the trigger 5. At this, trigger 8 tilts, opens logic element 9 and starts electroacoustic transducers b and 12 An encoded ultrasonic sending is emitted to the object side by the electro-acoustic transducer 6 and, at the same time, a short sound pulse of the electro-acoustic transducer 12 is emitted towards the reflector 15. ecause the distance to the reflector is small (e.g., 8 cm), the reflected signal of 0.5 ms returns to electrical transducer, the latter is sensed, amplified by an amplifier and restarts the electroacoustic transducer via the OR gate II. As a result, the electroacoustic transducer 12 enters an oscillator mode, the oscillation frequency of which depends on the speed of sound in air. The output pulses of this generator through an open logic element I enter the counter 10. As soon as the signal reflected from the photographed object reaches the electroacoustic converter 6, its output signal, having passed the amplifier 7, sets the trigger 8 to its initial state, the element 9 closes and the number is fixed in the counter, corresponding to the measured distance. At this moment, the amplifier 7 turns on the focusing motor 3, which is connected via a gearbox 2 with a lens that is initially set to "infinity." The lens moves toward shorter distances. The counting wheel 4 with the transducer 14 generates pulses that fill the free positions of the counter. When the counter overflows, the focusing motor 3 stops, holding the lens in the best focus position. At this point, the photographer can see in the viewfinder (in the case of using a mirror system) a clearly focused image and perform an exposure. The acoustical transducer 12 and the reflector 15 are placed in a special compartment of the chamber connected to the external environment through slit openings. As a result, in the space between the electroacoustic transducer 12 and the reflector 15, temperature, humidity, pressure and gas composition are maintained, which coincide with the similar parameters of the external environment. The implementation of the invention in the industry for the production of photographic equipment will allow to obtain a qualitative effect, which consists in increasing the reliability of the autofocusing system when working in various environmental conditions, which leads to an increase in consumer properties of photographic equipment. Apparatus of the Invention A device for automatically focusing a camera lens, comprising an electroacoustic converter with an amplifier, a time-pulse converter consisting of a series-connected trigger, a logic element AND and a counter, an electric motor connected through a reduction gear with a camera lens and a converter for turning the lens into pulses , as well as the trigger mechanism, and the electro-acoustic converter is connected to the trigger output, and the output - through an amplifier with These inputs of the flip-flop and to the engine, wherein the second input is coupled to the trigger the trigger mechanism, characterized in that, in order to increase the focusing precision, it introduced a further electroacoustic transducer with a reflector installed on his. a fixed distance, a second amplifier and a logic element OR is connected by its output to an input of an additional electroacoustic converter, the output of which through an amplifier is connected to the input of an AND logic gate and the input of an OR logic element, the second input of which is connected to the trigger output. Sources of information taken into account in the examination 1. "Photo Revue, 1977, No. 5. p. 253-256. 2. “Electronics, 1978, No. 10, p. 4142 (prototype).