Abstract: A light signal entering a photo-electric converter means is interrupted at a certain interval of time. An electrical signal produced from the photo-electric converter means, after a predetermined amount of electrical signal is added to it, is A-D converted. The difference between the digital signal associated with the interruption of light to the photo-electric converter means and the digital signal associated with non-interruption of light to the photo-electric converter means is produced, which difference is proportional to the incident light signal. Even when the light entering the photo-electric converter means is very weak, the fact that a predetermined amount of electrical signal is added contributes to A-D conversion of good linearity. Even very weak light is thus A-D converted accurately. Noises and undesirable DC signal components contained in the two types of digital signals are offset by production of the difference.

Abstract: A photometric device for measuring and displaying by digital means primary color densities of a color negative to be printed to determine densities of color compensating filters. Exposure time, including reciprocity effect compensation for the photographic paper, is displayed digitally and determined by density measurements of the projected image.A reference area of a color negative illuminated by light through color compensating filters is projected on the aperture of a probe which directs light through a light guide to a photodetector. The resulting photocurrents generate voltages amplified by a first and second variable gain linear amplifier. The second amplifier provides primary color and exposure density reference by means of gains stored by measurement of a standard negative. Digital display means is provided to display memory gains for accurately modifying or resetting reference gains.

Abstract: The exposure metering circuit comprises a differential amplifier, whose inputs are connected to a measuring bridge consisting of a photo-conductive cell and setting controls for the insertion of exposure factors and whose outputs are connected to light-emitting elements for the indication of a set under-exposure, over-exposure or the correct exposure. The two measuring bridge feed points are connected across a resistor, on the one hand, and across a transistor which is driven by means of a voltage derived from the common emitter circuit of the differential amplifier, on the other hand, to an operating voltage source.

Abstract: An exposure meter provides a display indicating the brightness of selected portions of a scene to be photographed. In one embodiment, a photometering block including a plurality of light sensitive elements is employed, and there is an automatic fixed display indicating the brightness level of the brightest and the darkest portions of the objective scene together with a display of a median value. Another embodiment employs a spot photometering device with only one light sensitive element, and a display of the brightness level of different portions of the scene selected by the photographer.

Abstract: The present invention relates to an integrated circuit body suited to be applied for a TTL single reflex camera, by arranging at least two of the three circuit parts, namely the indication circuit part presenting an indication function, the light sensing circuit part presenting a light sensing function and the control-operation circuit part.

Abstract: A photometer for providing a measurement of shutter speed or aperture setting corresponding to a preselected value of the other comprises a photodiode supplying a voltage proportional to the logarithm of the measured light intensity. This voltage controls the frequency of an oscillator supplying pulses to a counting circuit during a time interval set by a timer.

Abstract: Photometer means usable in scientific instrument having a video display means such as a scanning electron microscope including means for matching the intensity of the video display to the exposure time selected for photographing said video display taking into consideration such film characteristics as film speed, reciprocity failure and exposure time.

Abstract: An analog-to-digital converter circuit for a photographic exposure meter includes a plurality of parallel connected transistors 51, 54, 57 and 60 whose bases are connected to the logarithmic output of a light measuring circuit A. The transistor collectors are driven by constant current sources comprising an equal plurality of transistors 50, 53, 56 and 59 having emitter area ratios of 1:2:4:8, whereby the collector voltages of the transistors represent a digital threshold conversion of the light measuring circuit output.

Abstract: A first voltage divider comprised of a fixed resistor and a light-dependent resistor, and a second voltage divider comprised of two fixed resistors are both connected across the camera battery. A variable attenuator is located in the path of scene light incident upon the light-dependent resistor and is coupled to the diaphragm-setting selector for coordinated movement. Two transistors of complementary conductivity type have their bases connected in common to the first voltage-divider tap and their emitters connected in common to the second voltage-divider tap. Each one of two light-emitting diodes is connected in the collector-emitter circuit of a respective one of the two transistors. An adjustable resistor is connected between the bases and emitters of the transistors for establishing the potential difference across the two voltage-divider taps at which the transistors become conductive and the diodes become illuminated.

Abstract: In a photometric circuit a reference current is supplied into the input of the logarithmic amplifier at the same time the signal compensating the error originating in the photocell is supplied to the circuit. The reference current corresponds to the current which would occur in the photocell for the lowest measurable intensity of illumination. A sum-and-difference amplifier has one of its inputs supplied by the output of the logarithmic amplifier and its second input is supplied by a reference voltage. The control loop contains a storage capacitor connected after the sum-and-difference amplifier and an impedance converter connected after the storage capacitor. The compensating and reference currents are controlled by switches synchronized with a light chopper mounted in front of the photocell.

Abstract: A light measuring and indicating circuit utilizing indicating elements such as light-emitting diodes, to indicate corresponding light intensity levels. Intermediate levels are indicated without increasing the number of flip-flops employed in an activating circuit for the light-emitting diodes by intentionally causing the circuit to activate light-emitting diodes alternately. The activating circuit includes a reversible digital counter controlling the light-emitting diodes, two comparators for operating the counter reversibly in response to the comparison of light-dependent and standard signals, and a digital-to-analog converter which varies one or more of said signals in accordance with a counter output.

Abstract: An indicating exposure meter for a camera has an array of indicating elements, each of which has an active and an inactive state ascertainable by inspection, and a circuit responsive both to light from the scene being photographed by the camera, and to the actual setting of the exposure factors of the camera for controlling the state of each indicating element. The magnitude as well as the direction of the displacement of the setting of the exposure factors from the correct setting is ascertainable from visual inspection of the location of the active indicator elements in the array.

Abstract: In a metering device for cameras comprising an operational amplifier, a photodiode connected between the positive and the negative input terminal of the operational amplifier, and a logarithmic conversion diode connected between the negative input terminal and the output terminal of the operational amplifier, the electric charge stored in the capacity present in the photodiode due to noise may be discharged to a capacitor which is adapted to reduce its potential in synchronism with the output potential drop of the operational amplifier.

Abstract: A photometer for measuring the light transparency of a substance. A light beam is provided for illuminating a substance, which light beam passes through the substance and strikes a photoelement and produces a measuring current. The voltage generated from the measuring current is logarithmated by a converter circuit and is supplied to an indicating instrument for indicating a measured value. A zero balance control circuit is provided for controlling the voltage applied to the indicating instrument so that the indicating instrument will return to a value determined by a previous measuring of a calibrated substance. If the transparency of the measured substance is identical to the transparency of the calibrated substance, the indicating device will return to a zero value. A value other than zero will indicate the difference in transparency of the measured substance from the calibrated substance.

Abstract: This invention relates to a digital exposure meter in which brightness information is digitized and exposure factors such as film sensitivity are converted to digital values to perform digital computation. Accordingly, an exposure value, average exposure value, aperture value or shutter time is derived while a computer having various operation functions being controlled in sequence by sequence control means.

Abstract: A display system for a camera of the type having shutter preselection and diaphragm preselection automatic exposure control modes which are selectively operative by a switch is provided with a single array of decimal digit display elements for displaying the numerical values of the preselected shutter speed or diaphragm aperture and of the computed result representing the effective aperture or exposure time respectively at a time in combination with control means cooperative with the mode select switch for controlling relative display arrangement of the numerical values and/or display color change, thereby it being made possible for the photographer looking the display to insure that the camera operates in the intentionally selected exposure control mode.

Abstract: An exposure control for automatically controlling the duration of the exposure time for a photographic material to be printed. The light intensity is sensed by a sensor which could be either of the photoresistive or the photovoltaic type. A range control controls both the light sensor circuit and a timer control. The range control permits to return the indicator to a permanent mark despite variations of the lens aperture, negative density, degree of enlargement and the like, while simultaneously increasing or decreasing the length of a standard timing signal. The timing signal in turn controls the printer lamp to determine the exposure time.

Abstract: A method and device for use in detecting a precise focussing point, which comprises the steps of: placing a photoelectric element on an optical path or optical axis of a lens of a camera; converting the information of the precise focussing point for a photographic object into a frequency variation of an A. C. signal; feeding said signal having varying frequency to a highly sensitive frequency detector such as a resonance circuit, a tuned amplifier, or frequency-amplitude convertor having acute frequency characteristics; and detecting the precise focussing point with high sensitivity by means of the output thus obtained; whereby the aforesaid functions may be satisfactorily performed, irrespective of the variation in the luminance of the object and whereby the focus of the lens may be brought into precise conformity to the predetermined plane (i.e., the position corresponding to a film).

Abstract: An exposure meter circuit is disclosed in which the photoreceptor may be either a photovoltaic element such as a photodiode or a photoconductive element such as a CdS element. The meter is able to provide an indication of various exposure determining factors such as object brightness, shutter speed, aperture, or a fixed point for alignment by appropriate choice of circuit values.

Abstract: A circuit arrangement for the pre-indication of the exposure time to be expected in automatic mirror-reflex cameras in which the brightness of a controllable luminous element, which is constant for the duration of the exposure, is used for the illumination of the photo-receiver of the electronic time-formation system. The voltage dropping over the luminous element, which is proportional to the exposure time, is ascertained by means of a measuring mechanism. The luminous element is formed as luminous diode and in parallel therewith there is connected a current path containing the measuring mechanism fed from a constant current source for the compensation of the response voltage of the luminous diode and for the adaptation of the measuring mechanism to the characteristics of the luminous diode.

Abstract: A system for detecting the brightness of an area which is to be photographed. A plurality of series circuits respectively include a plurality of photosensitive devices for respectively receiving light from different parts of the area while remaining substantially static with respect thereto so that when the area is illuminated unevenly a pair of the photosensitive devices will respectively receive light of maximum and minimum brightness. The plurality of series circuits respectively include also a plurality of series-connected elements respectively connected in series with the plurality of photosensitive devices for respectively providing therewith a plurality of photo-responsive divided voltages. The plurality of series circuits are connected in parallel with each other and with a power source.

Abstract: In an exposure meter having a row of lighting elements, such as lamps or light-emitting diodes, which correspond to respective exposure values, an improvement is made in that by utilizing a capacitor-charging integrating circuit, a constant current circuit and a ring-counter, an exposure value between two neighboring steps of the above-mentioned exposure values can be indicated by lighting said two lighting elements, and in that ranges of exposure indication can be switched by shifting a dial plate, which is facing the lighting elements, in interlocking relation with a range-shifting switch for switching its circuit for range selection, thus enabling a doubling of the steps of exposure values to be indicated with a limited number of lighting elements.

Abstract: This invention relates to a light-measuring apparatus wherein a photoelectric element is arranged in a leg of a measuring bridge, the output voltage of said element controlling the brightness of two signal lamps.

Abstract: In an automatic photometer for metering light from a sample to be measured which includes a light source for illuminating the sample and an objective for focusing the light passed from the light source through the sample, a slit is positioned closely adjacent the focal plane of the objective and has an opening providing a central area and an outer area surrounding the central area. Two light receiving elements are disposed to receive the light passed through the central and outer areas of the slit, respectively, and means are provided for effecting photometry under selected conditions of light reception by the light receiving elements.

Abstract: An indication system of a camera which allows the use of an indication system such that photographing information of a camera is indicated with illumination by a plural number of indication elements being positioned in parallel. Further such letters and symbols which distinguish different kinds of photographing information are indicated by at least a part of the plural number of indication elements.

Abstract: An off-photometric-range indicating device for photometric circuits for cameras visually indicates to a photographer when the brightness of an object to be photographed is off the set photometric range of the photometric circuit. The indicating device includes a detection circuit to detect the brightness of the object and to produce an output signal when the detected value of the brightness is out of the photometric range of the photometric circuit, a switching circuit connected to the detection circuit and operated by said output signal, and a circuit connected to the switching circuit and actuated by the operation of the switching circuit to scale out the indicator, which may be visually observed by the photographer.

Abstract: An autoranging digital luxmeter is disclosed in which the current from a photocell is converted into a voltage by cascaded, variable gain amplifiers. The output of the amplifiers is coupled by a sample-and-hold circuit to an analogue-to-digital converter, the output of which is a digital representation of lux. The output of the amplifiers is also connected to limit comparison circuitry which, by way of an up-down counter, varies the gain of one or both of the amplifiers.

Abstract: A camera shutter control device includesA light intensity to electric signal conversion means, which means further includes a first photosensitive means and a second and a third photosensitive means. The first means and the second and third means are designed in such a manner that they receive the light beams coming from a substantially different part of the object to be photographed and give electrical signals corresponding to the light quantity received.A memory means is included, which is electrically connected with the first and second conversion means and serves to memorize the difference between the signal outputs of both conversion means.

Abstract: Light responsive circuit of low current consumption and low cost and used for camera exposure control and/or exposure indication. The circuit includes a field effect transistor, a photodiode connected between gate and source of the field effect transistor, a transistor having a collector connected to the gate of the field effect transistor and further having a base connected to the source of the field effect transistor, and a control circuit for controlling base voltage of the transistor to regulate source potential of the field effect transistor.

Abstract: In a single lens reflex camera equipped with a shutter time preselection-automatic exposure range and a diaphragm aperture preselection-automatic exposure range, the drive circuits of a light-sensor and a digit readout assembly arranged in the view finder are controlled in time-spaced relation to each other by timing signals. These signals in turn are controlled by a train of clock pulses to alternately bring the sensor and the digit readout assembly into sequential operation. In this manner, the light value as sensed by the sensor is not affected by any part of the light from the energized digit readout assembly.

Abstract: In a digital display system of the type wherein a plurality of luminous display elements are selectively operated in accordance with the value of an analogue input signal, the driving circuit of the display elements is constructed such that one display element is operated in accordance with one predetermined level of the input signal, that another display element is operated in accordance with another predetermined level of the input signal and that said one and another display elements are operated simultaneously for the input signal having a level intermediate of said one predetermined level and said another predetermined level.

Abstract: Light emitting elements such as light emitting diodes provided in the viewfinder of a camera are connected with a light measuring circuit including a photodetector through an A-D converter, a decoder and a gate circuit so that the light emitting elements may indicate exposure information in a digital form in accordance with the output of the light measuring circuit. An oscillator is connected with the A-D converter and the gate circuit for giving sampling pulses to the A-D converter and clock pulses to the gate circuit. Between the oscillator and the gate circuit is provided a duty modulator to change the duty cycle of the square wave transmitted from the oscillator to the gate circuit. The duty modulator is connected with the light measuring circuit or the A-D converter so as to control the duty cycle of the square wave in accordance with the output from the light measuring circuit.

Abstract: A camera is provided, in which the light sensitive element for the electronic exposure meter can be commonly used as the light sensitive element for the exposure control circuit.

Abstract: A light-responsive system which includes a plurality of photosensitive elements respectively directed to different parts of a scene for respectively providing electrical inputs according to the brightness of the light at the different parts of the scene. The several inputs are supplied to a plurality of electrical circuits which in turn are connected with an output unit, these circuits operating in such a way that the output unit will be actuated only by that one of the inputs which corresponds to that part of the scene which has the maximum brightness or the minimum brightness. In this way it is possible to provide an output corresponding either to the maximum brightness of the scene or the minimum brightness of the scene without requiring scanning of the scene.

Abstract: A voltage proportional to the APEX indication quantity for exposure time is coupled to one terminal of a meter through a buffer stage transistor. Circuit means produce a reference potential which is applied to the other terminal of the meter. The buffer stage transistor is biased by circuitry including a feedback stage transistor with the biasing being such that substantially constant collector current operation is ensured.

Abstract: An off-photometric-range indicating device for photometric circuits for cameras visually indicates to a photographer when the brightness of an object to be photographed is off the set photometric range of the photometric circuit. The indicating device includes a detection circuit to detect the brightness of the object and to produce an output signal when the detected value of the brightness is out of the photometric range of the photometric circuit, a switching circuit connected to the detection circuit and operated by said output signal, and a circuit connected to the switching circuit and actuated by the operation of the switching circuit to scale out the indicator, which may be visually observed by the photographer.