Dark current pattern estimation method

Topic

Organizational Unit

INSTITUT. PROJETS&TECHNOL. TRANSFER UNIT

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Summary

New method for estimating the background pattern of image sensors at any operating temperature, based on laboratory measurements performed beforehand. Allows accurate correction of images in situations where sensor temperature cannot be controlled and mechanical shutters for in-situ calibration are not available. Simplifies camera operation while enabling size, weight and power optimizations.

Example: Vegetation moisture maps taken by space camera based on uncooled InGaAs technology.

NDMI (before correction)

Before correction

NDMI (after correction)

After correction

NDMI · Sensor temperature: 29.02 ºC · Exposure time: 300 μs

Intellectual Property

Patent

Estado de desarrollo

TRL 9Validated in three space missions featuring uncooled SWIR cameras

Intended collaboration

Licensing or assignment

Contact

Anselmo Sosa Méndez
Office for the Transfer of Knowledge
otai [at] iac.es (otai[at]iac[dot]es)

Market need

Image sensors produce background patterns that need to be corrected in every acquired image. These patterns depend on sensor temperature, among other parameters. Failing to correct them properly could result in images not meeting the required quality levels.

In some sensor technologies like InGaAs, the dependency with temperature is so strong that camera manufacturers have been forced to add temperature control systems to stabilize the temperature to some specific value(s), with the associated background patterns measured beforehand in factory or in the field with the help of mechanical shutters.

There are applications where controlling the temperature is not a feasible solution due to the limited amount of available power, mass and volume to devote to the temperature control system, specially when the ambient temperature can change rapidly.

Proposed solution

We propose an new method that allows obtaining high quality images by correcting the background patterns of image sensors at any operational temperature, thus removing the need of including temperature stabilization systems in cameras where such systems were mandatory.

Cameras integrating this method can benefit from a significant reduction of power, mass and volume, as well as from simplified operational requirements. This enables new applications in the aerospace, automotive and environmental monitoring markets, among others.

Competitive advantages

Accuracy

Correction performance is comparable to in-situ camera characterization.

Simplicity

The algorithm can easily run in an embedded system, such as the camera itself.

Flexibility

Works with any type of sensor, as it does not assume any specific pixel model.

Further examples

The images below have been taken by the DRAGO-2 camera onboard the ALISIO-1 satellite, based on uncooled InGaAs technology. With the proposed method, images can be properly corrected regardless the acquisition configuration and operating temperature, revealing features that would otherwise be hidden by sensor noise.

Greenland coast (before correction) Greenland coast (after correction)