Improved Auto Exposure for Digital and Smartphone Cameras


This invention is an improved auto exposure (AE) method which, unlike existing AE methods, does not make a middle brightness assumption. As a result, this invention allows for better exposed images, in particular in poor lighting conditions such as front/back lit and low light scenes. The developed method has been implemented on a camera platform and results obtained have shown generation of better exposed images as compared to existing auto exposure methods.


Technical Summary:

Getting proper image exposure is a critical component of digital or smartphone camera image pipelines. In professional photography, the right exposure is normally decided manually either by visual inspection or by using an external exposure meter. By contrast, point-and-shoot digital and cell phone cameras utilize an AE feature that automatically sets the exposure level without any user intervention. Many AE methods have been reported in literature which utilize the image brightness in one way or another to set the right exposure level. These methods set the exposure value so that the mean brightness value of the entire image or an elected part of the image becomes close to the middle brightness value. While the use of middle brightness value generates a proper exposure for scenes where the average intensity level is similar, this approach leads to overexposure or underexposure in which the average intensity level in the scene is varied.


Value Proposition:

Provides significant improvements to obtained image exposure for point-and-shoot cameras in all kinds of lighting environments by eliminating the middle brightness assumption.



  • Cellphone Cameras
  • Point-and-Shoot Digital Cameras
  • Photography Software


Key Benefits:

  • Ease of Use - allows for non-professional camera user to capture correctly exposed images
  • Clearer Images – provides improved image quality when intensity levels of light in scene varies
  • Real-Time Solution – entire process runs in real-time on a typical ISP (Image Signal Processor)



Nasser Kehtarnavaz

Mohammed Rahman


Rahman, Mohammad T., et al. “Using Image Entropy Maximum for Auto Exposure.” Journal of Electronic Imaging, vol. 20, no. 1, 1 Jan. 2011, doi:10.1117/1.3534855.

IP Status: United States patent 8,743,235 B2 issued on June 3rd, 2014.

Licensing Opportunity: This technology is available for exclusive or non-exclusive licensing.

ID Number: 09-051



Patent Information:
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OTC Licensing
Multi Media
Optics & Photonics
Sensors & Controls
Signal Processing
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