Polarizing filter control mechanism to reduce reflected light

• US 6,028,303 A
• Filed: 11/14/1997
• Issued: 02/22/2000
• Est. Priority Date: 11/14/1996
• Status: Expired due to Term

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Suzuki, Toshio
• Primary Examiner(s): Allen, Stephone
• Application Number:
  US08/971,105
• Time in Patent Office: 830 Days
• Field of Search: 250/225, 396/544, 359/493, 359/501, 359/502, 359/601, 359/603, 359/608, 359/891
• US Class Current: 250/225
• CPC Class Codes: G02B 27/281 used for attenuating light intensity, e.g. comprising rotatable polarising elements
• CPC Class Codes: G03B 11/00 Filters or other obturators specially adapted for photographic purposes
• CPC Class Codes: G03B 17/12 with means for supporting objectives, supplementary lenses, filters, masks, or turrets
• CPC Class Codes: H04N 23/55 Optical parts specially adapted for electronic image sensors; Mounting thereof

Abstract

A polarizing filter control mechanism used in a camera that automatically rotates a polarizing filter in order to minimize the effects of reflected light on a photographic image. An image signal is obtained by an imaging element that converts image light of a photographic subject into an electrical signal. A level detection unit outputs a level detection signal that corresponds to the electrical signal. A minimum value detection unit compares the level detection signal with a reference signal. Using this comparison, the minimum value detection unit outputs an error signal based on a difference between the level detection signal and the reference signal. A drive control unit rotates the polarizing filter until the difference between the level detection signal and the reference signal is minimized.

Claims

1. A polarizing filter control mechanism comprising:

a polarizing filter;

a level detection unit to output a level detection signal corresponding to an image signal of a subject;

a drive control unit to rotate said polarizing filter to minimize the level detection signal;

an imaging element to convert the image signal of the subject to a corresponding electrical signal, wherein the electrical signal is input to the level detection unit; and

a minimum value detection unit to compare the level detection signal with a reference signal and output a corresponding error signal.

2. The polarizing filter control mechanism according to claim 1, wherein the reference signal is a minimum value detected by said minimum value detection unit.

3. The polarizing filter control mechanism comprising:

a polarizing filter;

a level detection unit to output a level detection signal corresponding to an image signal of a subject; and

a drive control unit to rotate said polarizing filter to minimize the level detection signal wherein the level detection signal corresponds to a level of the image signal from which a synchronizing signal has been removed.

4. A polarizing filter control mechanism comprising:

a polarizing filter;

a level detection unit to output a level detection signal corresponding to an image signal of a subject;

a drive control unit to rotate said polarizing filter to minimize the level detection signal;

a minimum value detection unit to compare the level detection signal with a reference signal and output a corresponding error signal;

a rotation sampling unit to rotate the polarizing filter and sample the level detection signal at designated angles; and

a memory unit to store the sampled level detection signal, wherein the minimum value detection unit compares the level detection signal in the memory unit and detects a minimum value of the level detection signal.

5. The polarizing filter control mechanism according to claim 4, wherein rotation of the polarizing filter is greater than 90 degrees.

6. A polarizing filter control mechanism in a camera, comprising:

a polarizing filter;

a level detection unit to output a level detection signal corresponding to an image signal of a subject;

a drive control unit to rotate said polarizing filter;

an imaging element to convert the image signal of the subject to a corresponding electrical signal, wherein the electric signal is input to said level detection unit; and

a minimum value detection unit to compare the level detection signal with a reference signal and output a corresponding error signal, wherein said drive control unit minimizes the level detection signal through rotation of said polarizing filter in response to the error signal.

7. The polarizing filter control mechanism according to claim 6, further comprising:

a default position control unit to rotate the polarized filter to a rotation angle where the level detection signal is a minimum value.

8. The polarizing filter control mechanism according to claim 6, wherein the level detection unit integrates and converts the electrical signal to a DC voltage output.

9. The polarizing filter control mechanism according to claim 6, further comprising a range selection unit to select a range of the image signal wherein the level detection signal corresponds to the image signal within the selected range.

10. The polarizing filter control mechanism according to claim 6, wherein the level detection signal corresponds to a level of the image signal from which a synchronizing signal has been eliminated.