DEVICE FOR THE AUTOMATIC STOP SETTING OF PHOTOGRAPHIC CAMERAS

• US 3,816,841 A
• Filed: 10/06/1972
• Issued: 06/11/1974
• Est. Priority Date: 10/13/1971
• Status: Expired due to Term

• Current Assignee: Hans Dietrich Schmidt, Herbert Maronde
• Original Assignee: Hans Dietrich Schmidt, Herbert Maronde
• Inventors: Maronde, Herbert, Schmidt, Hans Dietrich
• Primary Examiner(s): Peters, Jr., Joseph F.
• Application Number:
  US05/295,729
• Time in Patent Office: 613 Days
• Field of Search: 95/1C,1CD,11.5,64R 352/141 250/215,229
• US Class Current: 396/259
• CPC Class Codes: G03B 7/085 for control of aperture

Abstract

An attachment for a camera has an adjusting ring rotatable about an axis. The stop setting ring of the camera is positioned within the adjusting ring and the two are engaged so that rotation of the adjusting ring will rotate the stop setting ring. A photoelectric cell projecting forwardly on the attachment measures the ambient light and operates a servomotor to rotate the adjusting ring accordingly. A shade affixed to the adjusting ring moves into the path of the light to the photocell to a greater or less extent depending on the position of the adjusting ring. This is correlated with the light through the lens setting so that when the latter is at an optimum, the amount of light reaching the cell (past the shade) causes the cell to deenergize the servomotor.

Claims

1. An attachment for automatically positioning the rotatable light stop setting ring on the lens of a camera, said attachment comprising:

a rotatable adjusting ring;

means for mechanically coupling the adjusting ring and the setting ring for movement in unison comprising a coupling ring segment received in a particular position on said setting ring, said segment having a curved periphery with an opening thereon, and a pawl mounted on the adjusting ring in a position to enter said opening on the segment and thereby engage the segment, said pawl being movable toward and away from the segment so that it can rest on said periphery when not aligned with the segment opening;

a servomotor coupled to the adjusting ring for rotating the same; and

control means coupled to the servomotor and including a photoelectric detector positioned on the object side of the attachment for controlling the servomotor in response to the ambient light conditions.

2. An attachment as set forth in claim 1, including a box-shaped body having a central aperture into which the camera lens extends, said adjusting ring being positioned around said aperture.

3. An attachment as set forth in claim 2, including shade means secured to the attachment ring and positioned to move in a path in front of the detector for blocking the light to the detector to a greater and less extent depending upon the position of the adjusting ring.

4. An attachment as set forth in claim 3, wherein said setting ring has two limits of movement, including signal means connected to said control means to identify when the limits of movement are reached.

5. An attachment as set forth in claim 3, wherein said servomotor has an armature energizable in one polarity to achieve rotation in one direction and energizable in the other polarity to achieve rotation in the other direction, said control means includes a pair of power transistors connected to said armature, and a pair of series-connected complementary transistors having interconnected collectors connected to the bases of the power transistors to control the polarity of energization of said armature.

6. An attachment as set forth in claim 5, wherein said control means includes a potentiometer having a slider, said potentiometer being connected between the bases of said complementary transistors, and means connecting said detector to said slider.

7. An attachment as set forth in claim 5, wherein said adjusting ring has two limits of rotation, said control means including first limit switch means positioned to be actuated when one of said limits of rotation is reached, second limit switch means positioned to be actuated when the other of said limits of rotation is reached, first circuit means including the first limit switch means, second circuit means including the second limit switch means, said circuit means being connected in parallel with each other and in series with said armature, one circuit means iNcluding a diode permitting current flow only in one direction and the other circuit means including a diode permitting current flow only in the other direction.

8. An attachment as set forth in claim 7, wherein said detector is a photoconductive cell, and said means connecting said detector to said slider includes voltage divider including resistance means variable in steps by means of a setting knob.

9. An attachment as set forth in claim 1 for use with a photoflash unit, characterized by said setting ring having a limit of movement corresponding to minimum ambient illumination, said control means including switch means connectable to said unit to switch on said unit when said limit of movement is reached.

10. An attachment as set forth in claim 1, wherein said opening is a slot aligned with the axis of the opening and said pawl is mounted for pivotal movement about a line in a plane transverse to said axis.

11. An attachment as set forth in claim 1, wherein said setting ring has two limits of movement, including signal means connected to said control means to identify when the limits of movement are reached.

12. In an attachment for automatically setting photographic cameras having an objective and a diaphragm setting ring, said attachment including an actuating element adapted to be mechanically coupled to said diaphragm setting ring, a servomotor, means rotatably coupling said motor with said actuating element, a photoelectric detector, a tube through which said detector receives light, electronic means connecting said detector and said motor for setting the rotatable position of the motor in response to the light received by said detector, the improvement in said attachment comprising:

a box shaped body having a substantially centrally positioned aperture therethrough into which aperture said camera objective extends, said tube being adjacent said aperture and generally parallel thereto, said actuating element comprising an actuating ring encircling said aperture and means for coupling said actuating ring wigh said setting ring at a predetermined relative position, a crescent-shaped light stop affixed to said actuating ring and extending into said tube to control the amount of light passing through the tube to the detector as a function of the position of the actuating ring, said rotatable coupling means including a gear segment attached to said actuating ring and a pinion on the shaft of the servomotor in mesh with said gear segment, and said electronic means including an amplifier.

13. An attachment as set forth in claim 12, wherein said servomotor has an armature energizable in one polarity to achieve rotation in one direction and energizable in the other polarity to achieve rotation in the other direction, said control means includes a pair of power transistors connected to said armature, and a pair of series-connected complementary transistors having interconnected collectors connected to the bases of the power transistors to control the polarity of energization of said armature.

14. An attachment as set forth in claim 13, wherein said control means includes a potentiometer having a slider, said potentiometer being connected between the bases of said complementary transistors, and means connecting said detector to said slider.

15. An attachment as set forth in claim 14, wherein said detector is a photoconductive cell, and said means connecting said detector to said slider includes voltage divider including resistance means variable in steps by means of a setting knob.

16. An attachment as set forth in claim 12, wherein said adjusting ring has two limits of rotation, said control means including first limit switch means positioned to be actuated when one of said limits of rotation is reached, second limit switch means positioned to be actuated when the other of said limits of rotation is reached, first circuit means including the first limit switch means, second circuit means including the sEcond limit switch means, said circuit means being connected in parallel with each other and in series with said armature, one circuit means including a diode permitting current flow only in one direction and the other circuit means including a diode permitting current flow only in the other direction.