Method for processing an image signal for double or multiple exposure cameras

• US 8,390,701 B2
• Filed: 04/29/2010
• Issued: 03/05/2013
• Est. Priority Date: 04/29/2010
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Klijn, Jan, Schirris, Johan, Cvetkovic, Sasa, Sturm, Peter
• Primary Examiner(s): Fan, Chieh
• Assistant Examiner(s): SPINKS, ANTOINETTE T
• Application Number:
  US12/770,447
• Publication Number:
  US 20110267506A1
• Time in Patent Office: 1,041 Days
• Field of Search: 348/222.1, 348/226.1, 348/229.1
• US Class Current: 348/226.1
• CPC Class Codes: H04N 23/745 Detection of flicker frequency or suppression of flicker wherein the flicker is caused by illumination, e.g. due to fluorescent tube illumination or pulsed LED illumination
• CPC Class Codes: H04N 23/76 by influencing the image signals
• CPC Class Codes: H04N 25/583 with different integration times

Abstract

Methods are described for processing an image signal for double or multiple exposure cameras in order to reduce fluorescent artifact effects.

Claims

1. A method for processing an image signal for double or multiple exposure cameras, the method comprising:

determining whether fluorescent light is present;

if so, ascertaining the period of the fluorescent light;

forming a plurality of image signals having different exposure conditions with at least one image pickup sensor, such that at least a long exposure time is made equal to a multiple of the fluorescent light period, and a short exposure time is made equal to a fraction of the long exposure time;

correcting at least part of the plurality of image signals with a correction function in order to obtain a corrected output signal;

combining at least one of said plurality of image signals and said corrected output signal to form a combined image signal; and

applying a gain factor G to the combined image signal, so that at least some image areas are shifted out of a display range.

2. The method of claim 1, further comprising:

reducing the color saturation of image areas shifted out of the display range.

3. The method of claim 1, wherein to determine, whether fluorescent light is present, color differences between long exposure times and short exposure times are monitored over time.