Patent GB-1234299-A (GB)
IPC: G03B7/20
Filed: 1968-08-16
Abstract: 1,234,299. Reflex camera with inter-changeable lenses. NIPPON KOGAKU K.K. Aug.16, 1968, [Aug.18, 1967], No.39417/68. Heading G2A. A reflex camera with an exposure meter viewing through the lens has provision for compensating the meter for the different aperture ratios of inter-changeable lenses by an inter-connection between the stop adjusting ring and a variable resistance in the meter circuit. A ring 1 rotatably mounted on the camera body and inter-locking with the stop ring D by means of a pin 2 is also connected to a control ring 4, Fig. 2, by a spring 3 so that the ring 1 has a tendency to rotate anti-clockwise and the ring 4 to rotate clockwise. The control ring 4 has a resistance strip R Fig.4 (not shown) around its periphery engaged by a brush (P) on a shutter speed setting ring and connected in parallel with the meter. The inter-locking ring 1 is provided with a projection 5 accommodating a pivoted ratchet lever 7 formed at end 76 with a pawl to engage ratchet teeth 4a spaced around the control ring 4. To fix a lens to the camera body, the ring 1 is first rotated clockwise. By means of spring 3 the control ring 4 also rotates until it is stopped by a detent 10a of an L-shaped lever 10, but rotation of ring 1 continues until the pawl 7b engages ratchet teeth 4a in the controlling position 4d. In this position and when the aperture ratio is adjusted to 5À6 as shown in Fig. 1, the bayonet joint parts (not shown) of the lens and lens mount coincide so that the lens may be inserted. The lens is then rotated anti-clockwise to the position in Fig.6 (not shown) when it is secured to the mount. In doing so the rings 1 and 4 rotate simultaneously, connected by the ratchet mechanism. The stop ring D is then rotated counter-clockwise to a desired stop position thereby rotating ring 1 in the same direction with the part 7a of the ratchet lever is moved into contact with a cam part 9a of a pivoted lever 9. This disengages the pawl 7b from the ratchet teeth 4d to allow the control ring to rotate clockwise under the urgence of spring 3 until a projection 4c of the ring engages the detent 10a. When the ring 1 is further rotated counterclockwise the projection 5 pushes up a pin 19 causing levers 18 and 9 to rotate clockwise allowing the part 9a to move out of the path of the ratchet lever end 7a. The stop ring D is then rotated clockwise to the full aperture setting. Ring 1 also rotates and the projection 5 moves along a cam part 6a of a lever 6. The rotation of lever 6 is transferred to the lever 10 which rotates clockwise so that detect part 10a moves the control ring 4 anti-clockwise by an amount which corresponds to the particular aperture of the lens inserted. In removing the lens from the camera, the lens is rotated clockwise thereby rotating ring 1 in the same direction. The control ring 4 remains held by the detert 10a so that the ratchet lever 7 moves over the ratchet teeth to position 4d and at the same time projection 5 acts on a pin 9b on lever 9 to rotate the lever anti-clockwise so that part 9a is repositioned in the path of projection 5 on the ring 1. A simpler embodiment Fig. 11 (not shown) omits cam lever 6 and the L-shaped lever 10. The detert part 10a is replaced by a fixed pin (23). This embodiment operates satisfactory when the light intensity change on the exposure meter is proportional to the full aperature change of the lens.