CAMERA SHUTTER CONTROLS FOR EXTREMELY SHORT EXPOSURE TIME

• US 3,848,986 A
• Filed: 04/23/1973
• Issued: 11/19/1974
• Est. Priority Date: 05/12/1971
• Status: Expired due to Term

• Current Assignee: Nobuhiro Noda, Seinan Miyakawa
• Original Assignee: Nobuhiro Noda, Seinan Miyakawa
• Inventors: Miyakawa, Seinan, Noda, Nobuhiro
• Primary Examiner(s): Matthews, Samuel S.
• Assistant Examiner(s): Gellner, Michael L.
• Application Number:
  US05/353,884
• Time in Patent Office: 575 Days
• Field of Search: 95/1CT,53EB
• US Class Current: 396/238
• CPC Class Codes: G03B 7/083 for control of exposure time

Abstract

A camera capable of automatically determining the extent to which the film is exposed. When making an exposure of extremely short duration, controls are provided to deenergize an electromagnet which releases a trailing curtain in an extremely short time which does not require the interval usually required for response of the circuitry to various exposure-determining factors.

Claims

1. In a camera having circuitry for automatically determining the extent to which film in the camera is exposed, said circuitry including an electromagnetic means for terminating an exposure when said electromagnetic means becomes unenergized, switching circuit means electrically connected to said electromagnetic means for controlling the deenergizing thereof, signaltransmission means electrically conNected to said switching circuit means for transmitting to the latter a signal corresponding to exposure-determining factors for operating said switching circuit means to deenergize said electromagnetic means in accordance with said factors, and control means electrically connected with said switching circuit means for providing an automatic electrical control and a mechanical control, for causing the switching circuit means to deenergize said electromagnetic means after a variable time duration when providing said automatic control, and for causing the switching circuit means to deenergize said electromagnetic means after a pre-determined extremely short fixed time duration when providing said mechanical control, said switching circuit means including a high input impedance transistor electrically connected to said signal transmission means for receiving a signal therefrom and having an output, a thyristor for deenergizing said electromagnetic means, and wherein said control means includes a variable resistor means connected between said output of said transistor and said thyristor, said variable resistor means having an adjusting component having a position for operating said thyristor with a bleeder voltage for deenergizing said electromagnetic means, said last-mentioned position providing said mechanical control.

2. The combination of claim 1 and wherein said high input impedance transistor is a field effect transistor.

3. The combination of claim 1 and further comprising a switching transistor connected in series with said electromagnetic means and having a control electrode connected in parallel with said thyristor, such that when said thyristor conducts, said switching transistor becomes non-conductive.

4. The combination of claim 3 and further comprising Zener diode means connected in series between said thyristor and said control electrode of said switching transistor.