Abstract: A chopper comparator is constructed by connecting current control transistors Q.sub.15 to Q.sub.17 comprising p-channel MOSFETs between CMOS inverters 3 to 5 and a power source 7 to supply a power voltage V.sub.DD . A control signal V.sub.C to control a current flowing in the CMOS inverters 3 to 5 is supplied to gates of the current control transistors Q.sub.15 to Q.sub.17. In case of constructing the A/D converter, the chopper comparator is used.

Abstract: In an automatic exposure control device of digital information type for a single lens reflex camera, a sampling circuit for dividing pulses generated from an oscillator and a shutter release signal generating circuit are connected with a gate means having a function of an AND circuit. The gate means connected with a leading shutter blind control device and a normally turned OFF gate interposed between the oscillator and a clock pulse counter. When the gate means is turned ON by the simultaneous output of the sampling circuit and the shutter release signal generating circuit, the normally turned OFF gate is turned ON to initiate the counting of the clock pulses and the leading shutter blind is started to initiate exposure.

Abstract: In a photographic camera provided with an exposure control circuit including a light measuring circuit which measures scene brightness and a memory circuit which memorizes the output of the light measuring circuit, a switching circuit is connected between the light measuring circuit and the memory circuit. The switching circuit is connected with a time constant circuit so that the switching circuit may be turned off to lock the memory memorized in the memory circuit when the time determined by the time constant circuit has lapsed since the power source is turned on. In a preferred embodiment, the time constant circuit is further connected with the output of the light measuring circuit so that the time determined by the time constant circuit is varied in accordance with the scene brightness.

Abstract: A switch means for electrically operating a device in a photographic camera is composed of a mechanical switch and a semiconductor switching element connected with the mechanical switch. The mechanical switch has a pair of contacts made of resilient conductive material and increases its conductivity as the pressure applied thereto increases. By the increase of the conductivity of the mechanical switch an input voltage supplied to the semiconductor switching element is raised and the switching element is turned on when the input voltage has reached a predetermined level. Thus, chattering and large consumption of electric power are prevented.

Abstract: An exposure time control circuit for a camera includes a level selecting circuit between a light measuring circuit and a memory circuit to have a selected output memorized in the memory circuit. The level selecting circuit is provided with two inputs, one of which is the output of the light measuring circuit indicative of the scene brightness and the other of which is the output of a maximum exposure time output source indicative of the maximum exposure time acceptable to the camera. The memory circuit memorizes the output selected by the level selecting circuit which output indicates a shorter exposure time between the two.

Abstract: A resistor having a high resistance and a resistor having a low resistance are arranged in parallel to each other in side by side relation. A pair of input terminals are fixed to both ends of the resistor of low resistance. A movable contact is provided in slidable contact with the resistor of high resistance moving along the edge of the resistor of low resistance which is in contact with an edge of the resistor of high resistance.

Abstract: In an electric shutter including a light measuring circuit for measuring the scene brightness and a comparator connected therewith for providing output voltage which rises from a low level to a high level when a time corresponding to the scene brightness has lapsed, a switching transistor circuit and an electromagnet for holding the trailing shutter blind are connected in parallel between the output of the comparator and the main power switch. When the power switch is turned on, both the switching transistor circuit and the electromagnet are turned on. When the output voltage of the comparator rises up to the high level, the switching transistor circuit and the electromagnet are turned off.

Abstract: In an integration circuit including an operational amplifier wherein an integrating capacitor and a switch are connected in series across the operational amplifier as a negative feedback circuit, a positive feedback resistor is connected between the connecting point between the integrating capacitor and the switch and the reference input terminal of the operational amplifier. The potential difference across the integrating capacitor is made zero in order to remove the influence of the leakage current of the switch when the switch is in its OFF-state.

Abstract: A space is formed between a wall of a camera body and a part of a printed circuit board fixed to the wall of the camera body. A part of a flexible printed circuit and a resilient member are inserted into the space to resiliently press the flexible circuit onto the printed circuit board to assure a tight electric contact between the flexible printed circuit and the printed circuit board.

Abstract: In a logarithmic amplifier employing a log-diode connected across an operational amplifier, a dividing resistor and a transistor circuit are connected in parallel between the output of the operational amplifier and the log-diode. The temperature characteristic of the log-diode and that of the transistor circuit cancel each other to effect temperature compensation in the output of the operational amplifier.

Abstract: The start of the leading curtain or the trailing curtain of a focal plane shutter is controlled to obtain an accurate exposure time. A delay means is provided in the mechanism for releasing the leading curtain or in the mechanism for releasing the trailing curtain. The difference between the delay time of the start of the leading curtain and the delay time of the start of the trailing curtain is controlled to be equal to the constant time during which the leading curtain runs overlapping with the trailing curtain. In one embodiment, an inertia member is provided in the vicinity of the curtain release member to delay the movement of the curtain release member. In another embodiment, an electric delay circuit is provided to delay the start of the trailing curtain. In both embodiments, the time of delay of the start of the curtain can be controlled.

Abstract: An automatic exposure control circuit which controls the shutter speed in accordance with the output of a light measuring circuit including a photodetector which detects the level of scene brightness. The output of the photodetector is memorized by a memorizing capacitor and the shutter speed control circuit is operated in accordance with the memorized output. The memorized level is shifted to a predetermined level when the memorized level is below a predetermined level which corresponds to a limit of scene brightness which can be photographed. A switching circuit and a shifting circuit connected therewith are connected with an end of the memorizing capacitor so that the level of the memorized output may be shifted by the shifting circuit when the level memorized by the capacitor is below a predetermined level. The shutter speed is therefore determined regardless of the scene brightness when the level of the scene brightness is below a predetermined level.