The Lookup table (LUT) translates each pixel value from the camera through a programmable user-defined transfer function. The Lookup Table contains 1024 entries that range in value from 0 to 1023.
The Lookup table is also used to implement the IIDC Gamma feature. Gamma controls the contrast in the image by translating pixel values according to a logarithmic curve. A value of one is a linear translation. Higher or lower values of gamma will result in missing codes in the image histogram.
Since the Gamma and Lookup table functions share the same resource, when the Gamma feature is activated, the Lookup Table is disabled and vice versa. When the LUT or Gamma function is active (ON), every pixel is converted according to the transfer function stored in the LUT. With both functions off, the LUT is bypassed and a linear transfer function is used.
Since both Gamma and the LUT use the same camera memory, when the Gamma feature is activated, the Lookup Table is disabled and vice versa. When the LUT or Gamma function is active (ON), every pixel is converted according to the transfer function stored in the LUT. With both functions off, the LUT is bypassed and a linear transfer function is used.
Turning on the Gamma function will overwrite the LUT with the appropriate gamma values. Turning on the LUT will disable Gamma but will leave the camera memory unchanged. If the LUT is turned off, the LUT values will be retained in camera memory and will be applied again once the LUT is turned on.
The Lookup Table is not stored in the camera's non-volatile memory so if it is being used, it must be re-loaded after the camera is powered-up.
When to Use
Use this feature when:
You want to translate the brightness values from the camera through a user-defined transfer function. Common examples include Thresholding and Binarization.
You want to implement the IIDC Gamma feature.
How to Use
- The LUT is written to camera memory as a block of 1024 words at the address specified by the Look Up Table Offset register, starting with Word 0 (i.e. pixel value 0 or Black).
- The LUT address corresponds to the incoming pixel value. The contents of that address location are used to replace the pixel data.
- Write software using the SDK to program the Lookup Table into the camera.
- Use Pixelink Capture OEM to view the Lookup Table that has been programmed into the camera, and to save/restore the Lookup Table (with the Export/Import Config File functions).