Shutter for a photogrammetric camera

• US 4,942,415 A
• Filed: 08/30/1989
• Issued: 07/17/1990
• Est. Priority Date: 11/05/1988
• Status: Expired due to Term

• Current Assignee: Intergraph Hardware Technologies Company (Hexagon AB)
• Original Assignee: Carl-Zeiss-Stiftung
• Inventors: Krastel, Heinz, Felle, Karl
• Primary Examiner(s): Gellner, Michael L.
• Application Number:
  US07/400,686
• Time in Patent Office: 321 Days
• Field of Search: 354/65, 354/66, 354/234.1, 354/254
• US Class Current: 396/463
• CPC Class Codes: G03B 9/20 each moving in a single direction first to open and then to reclose

Abstract

The invention is directed to a shutter wherein the rotary discs thereof are accelerated out of a standstill start position for each exposure operation and are again brought to standstill at the end of the exposure operation. The start position is computed such that a constant access time results for all exposure times. An electronic control circuit for the shutter includes a position-control circuit and a speed-control circuit. During each exposure operation, the drive for the rotary discs of the shutter are switched between the two control loops.

Claims

1. A shutter for a photogrammetric camera comprising:

rotatably mounted disc means for defining a shutter opening;

drive means for rotatably driving said disc means for each exposure operation by accelerating said disc means out of a standstill start position thereof;

angle encoder means for measuring said start position of said disc means;

a control circuit for providing a signal indicative of a desired exposure time t_B ; and

,

a device operatively connected to said drive means for displacing said start position of said disc means in dependence upon said signal so as to cause the access time t_z between the start t_o of the acceleration and the exposure for different adjustable exposure times (t_B1, t_B2) to have a substantially constant value.

2. The shutter of claim 1, said disc means comprising a plurality of rotatably mounted discs;

and, transmission means for interconnecting said discs to each other and to said drive means at different speed ratios.

3. The shutter of claim 2, said transmission means being a gear transmission.

4. The shutter of claim 1, said disc means comprising a plurality of pairs of discs;

and, transmission means for interconnecting said disc pairs to each other and to said drive means at different speed ratios.

5. The shutter of claim 4, said transmission means being a gear transmission.

6. The shutter of claim 1, further comprising a control arrangement including a position-control loop and a speed-control loop;

and, said device including computer means for computing a preselected desired position value U_pos and a preselected desired speed value U_v in correspondence to the desired exposure time t_B and the constant access time t_z and for applying said position value U_pos to said position-control loop and said speed value U_v to said speed-control loop.

7. The shutter of claim 6, said control arrangement comprising changeover switching means for switching between said position-control loop and said speed-control loop during each exposure operation.