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Hot Pixels

uEye Camera Manual Version 3.80

Hot Pixels

Definition

Hot pixels (or in a broader sense, defective pixels) are pixels that do not react linearly to incident light - or do not react at all. They occur for various reasons, such as contamination during sensor production or sensor age, and with both CCD and CMOS sensors. CCD sensors generally have fewer hot pixels than CMOS sensors under the same operating conditions. With darkened sensors and prolonged exposure times, hot pixels are visible as individual bright dots in the image. The following factors promote the occurrence of hot pixels:

Long exposure times
High gain settings
High sensor operating temperature
Figure 28: Hot pixels detected in a monochrome camera

Figure 28: Hot pixels detected in a monochrome camera

Figure 29: Hot pixels detected in a color camera

Figure 29: Hot pixels detected in a color camera

Hot pixel correction

During the manufacture of our cameras, all sensors that will be used in uEye cameras are checked for hot pixels. In the process, images are taken with a darkened sensor and long exposure times. Pixels with a brightness higher than a specific value are classified as hot pixels. A list of the coordinates of each hot pixel is stored in the camera EEPROM. The hotpixel correction is done in the uEye driver. However, some sensors also provide an internal hotpixel correction.

The maximum number of hot pixels stored in a uEye camera is:

uEye model

max. hot pixels stored

GigE uEye (CMOS)

384

GigE uEye (CCD)

20

USB uEye (CMOS)

768

USB uEye (CCD)

20

How many hot pixels are on the camera's internal list depends above all on the defined threshold values. It is not an indication of the quality of the sensors used.

When you enable the Hotpixel correction function in the uEye software, the software automatically corrects the hot pixels in the captured image by calculating the average from the brightness value of two neighboring pixels. When using color sensors, the hot pixel is corrected with the appropriate color in raw Bayer format, i.e. before color conversion. The GigE uEye models correct hot pixels in the camera.

Hinweis

IDS also tests sensors for cold pixel and dead pixels. Sensors with dead pixel clusters (more than two neighboring defective pixels of the same color) are rejected by our quality control. When the camera is operated in very warm ambient conditions, other defective pixels can occur, however.

All sensors used in uEye cameras have been artificially aged by about one year before being installed in the camera. This reduces the probability that additional hot pixels occur with use of the camera.

Defining additional hot pixels

If additional hot pixels occur during use of the camera, you can add them to the camera's internal hot pixel list. To do this, use the API function given below.

See also:

uEye Demo: Hot pixel correction
Programming: is_HotPixel()

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