Automatic range finder system

An automatic range finder for a camera comprising:

• means for projecting a pulse of light beam toward an object;
• means kept apart from said projecting means by a predetermined base length for focusing the light beam reflected back from the object, the optical axis of said focusing means being substantially parallel with the path of the projected light beam;
• means arranged on the focal plane of said focusing means for receiving the reflected light beam focused by said focusing means, said receiving means including a plurality of photosensitive elements aligned along the direction of the base length;
• means connected to said photosensitive elements for detecting the individual currents generated by said photosensitive elements respectively to produce corresponding current outputs;
• means connected to said detecting means for converting said current outputs into corresponding voltage output respectively;
• means for generating reference voltage levels;
• means for comparing each of said voltage outputs from said converting means with each of said reference voltage levels respectively;
• and
• means for producing a distance signal in response to said comparing means, wherein said converting means comprising logarithmic conversion circuits, each of which is for converting each of said current output into a corresponding voltage in logarithmic relation with each of said current outputs respectively.

An automatic range finder for a camera comprising:

• means for projecting a pulse of light beam toward an object;
• means kept apart from said projecting means by a predetermined base length for focusing the light beam reflected from the object, the optical axis of said focusing means being substantially parallel with the path of the projected light beam;
• means arranged on the focal plane of said focusing means for receiving the reflected light beam focused by said focusing means, said receiving means including a plurality of photosensitive elements aligned along the direction of the base length;
• means connected to said photosensitive elements for detecting the relatively rapid changes in the individual currents generated by said photosensitive elements respectively to produce corresponding current outputs;
• means connected to said detecting means for converting said current outputs into corresponding changes in voltages if any of said relatively rapid changes in the currents is detected respectively;
• means for generating reference voltage levels;
• means for comparing each of said voltage changes from said converting means with each of said reference voltage levels respectively;
• and
• means for producing a distance signal in response to said comparing means, wherein said detecting means includes a plurality of circuit means each connected to each of said photosensitive elements respectively, said circuit means each comprising a current regulator having a first, second and third terminals for controlling a current flow between said first and second terminals in response to the voltage at said third terminal, said first terminal being connected to said photosensitive element, a constant current source, a transistor having a base connected to a junction of said first terminal and said photosensitive element and an emitter connected to said constant current source, a feed back circuit formed between said first and third terminals for causing a change in the voltage at said first terminal in a negative direction to the change in the voltage at said third terminal, said feed back circuit including means for delaying the signal transmission through said feed back circuit, bypath circuit connected in series with said constant current source of introducing an alternating current component of the emitter current of said transistor, whereby said transistor outputs a constant collector current according to said constant current source when alternating current component is not included in the current output from said photosensitive element, and outputs the constant collector current added to a change of current when a corresponding change is included in the current output from said photosensitive element.

An automatic range finder for a camera comprising:

• means for projecting a pulse of light beam toward an object;
• means kept apart from said projecting means by a predetermined base length for focusing the light beam reflected back from the object, the optical axis of said focusing means being substantially parallel with the path of the projected light beam;
• means arranged on the focal plane of said focusing means for receiving the reflected light beam focused by said focusing means, said receiving means including a plurality of photosensitive elements aligned along the direction of the base length;
• means connected to said photosensitive elements for detecting the relatively rapid changes in the individual currents generated by said photosensitive elements respectively to produce corresponding current outputs;
• means connected to said detecting means for converting said current outputs into corresponding changes in voltages if any of said relatively rapid changes in the currents is detected respectively;
• means for generating reference voltage levels;
• means for comparing each of said changes in voltages from said converting means with each of said reference voltage levels respectively;
• and
• means for producing a distance signal in response to said comparing means, wherein said detecting means includes circuit means connected to each of said photosensitive elements respectively, each of said circuit means comprising an output transistor, the collector current of which is proportional to the current output of said detecting means, means for maintaining the base-emitter voltage of said output transistor at a predetermined value irrespective of the relatively slow change in current generated by said photosensitive element and means for introducing the relatively sudden change in the current generated by said photosensitive element into the base of said output transistor and for absorbing the relatively slow change in current generated by said photosensitive element.

A range finder system which comprises light beam projection means for projecting light beam toward a subject to be measured for distance, an image forming optical system disposed at a position spaced a predetermined base length from said light beam projection means in such a manner that the optical axis of said optical system is substantially parallel to an optical axis of said light beam projecting means, a plurality of photosensitive elements so arranged, on an image forming surface of said image forming optical system, as to receive the light beam selectively reflected from the subject according to distances up to said subject, current output circuit means for developing current corresponding to the reflected light of the light beam selectively incident upon one or the plurality of said photoelectric elements, conversion circuit means for converting photoelectric current outputs of said current output circuit means into voltage signals corresponding thereto, and voltage comparison circuit means for comparing output voltages of said conversion circuit means with reference voltages, said range finder system further including reference voltage varying circuit means arranged to alter levels of said reference voltages applied to said voltage comparison circuit meansaccording to the outputs of said conversion circuit means which receives reflected light of the maximum intensity from said subject resulting from said light beam.

A range finder system which is arranged to receive reflected light of light beam in the form of a pulse projected from light beam projection means to a subject to be measured for distance, selectitvely by at least one of a plurality of photoelectric elements according to the distances thereof so as to detect the distance up to said subject through anaylsis of photoelectric current output of said photoelectric elements, said range finder system comprising conversion circuit means connected to each of said photoelectric elements and adapted to develop, in a steady state where light of a predetermined intensity is incident upon said photoelectric elements, a constant current irrespective of the intensity, and to develop during incidence of light in the form of pulse thereupon, a current corresponding to the intensity of said incident light in the form of pulse in addition to said constant current, a first load including one transistor at least whose collector is connected to the output of said conversion circuit means as the load, negative feedback amplification circuit means connected, at its input, to a junction between said photoelectric conversion circuit means and said first load, and also connected, at its output, to the base of said transistor, and further imparted with feedback amount holding characteristics, and a logarithmic compression element connected substantially in parallel with said first load and forming a second load, said range finder system further including current-voltage conversion circuit so arranged, by bypassing current corresponding to the intensity of the incident light in the form of pulses developed from said photoelectric conversion circuit through said second load, as to cause voltage signal in the logarithmic relation with the current value to be developed from said second load.

A range finder system which is arranged to receive reflected light of light beam in the form of a pulse projected from light beam projection means to a subject to be measured for distance, selectively by at least one of a plurality of photoelectric elements according to the distances thereof so as to detect the distance up to said subject through analysis of photoelectric current output of said photoelectric elements, said range finder system comprising a current control element connected in series with each of said photoelectric elements, an input transistor which is connected at its base, to a junction between said photoelectric element and said current control element, and which is functionally connected at its emitter, to a control electrode of said current control element, and circuit means coupled to the emitter circuit of said input transistor and including a constant current source for causing a constant current to flow through the collector of said input transistor during a steady state period and a capacitor for suppressing a rapid fluctuation of the emitter potential of said input transistor, whereby according to intensities of the pulse-like light from said light beam projection means incident upon said photoelectric elements in addition to standing light, the photoelectric current developed by the photoelectric elements is caused to flow into the base of said input transistor so as to derive current corresponding to the photoelectric current from the collector of said input transistor.