| 摘要 |
1353449 Photographic camera indicating devices SEIKO KOKI KK 23 May 1972 [31 May 1971] 24146/72 Heading G2A A photographic camera has an indicating device, e. g. a lamp L, a light emitting diode or a liquid crystal, which operates in a steady manner, e.g. continuous light emission, when the light incident upon a photoconductor Rc is above a predetermined maximum strength, and which operates a varying manner, e. g. periodic light output, when the light incident upon the photoconductor is less than a predetermined minimum strength. In the former event over exposure is likely and in the latter camera vibration is likely. Contact slides a 1 , b 1 of changeover switches S 2 A, S 2 B are both ganged for movement with the shutter release. In the first position the contact slides contact a 3 , b 3 respectively. If light incident on Rc is such that V > V o , strong lighting condition, then transistors T 1 , T 2 and T 3 all conduct to cause steady illumination of the lamp L. If the light incident is below the predetermined maximum strength determined by resistor R 1 so that V x <V o then the transistors are non conducting and the lamp L is not lit. Further movement of the shutter release causes the contact slides to contact a 4 , b 4 . In this condition transistors T 3 , T 4 together with resistors R 7 , R 8 and capacitors C 1 , C 2 constitute an astable multi-vibrator. If the light incident is below the predetermined minimum strength determined by resistor R 2 so that V x <V o , transistors T 1 and T 2 are cut off, but transistor T 3 conducts, base current flowing through the lamp L, slide switch S 2 B and capacitor C 1 . Thereafter the circuit of transistors T 3 , T 4 causes periodic illumination of the lamp L. If the incident illumination is above the predetermined minimum strength so that V x >V o , transistors T 1 , T 2 and T 3 continuously conduct and transistor T 4 is permanently cut off the lamp L remaining unlit. In a further embodiment, Fig. 2 (not shown) changeover switch S 2 A has a further contact so that further depression of the shutter release connects photoconductor Rc in series with a shutter timing capacitor the common point being connected to a Schmidt trigger which controls the closing action of the camera shutter. |
