MT9M114_16 Datasheet, PDF (27/62 Pages) ON Semiconductor – High-Definition (HD) System-On- A-Chip (SOC) Digital Image Sensor

MT9M114: 1/6-Inch 720p High-Definition (HD) System-On-A-Chip (SOC) Dig-
ital Image Sensor
Gamma Correction
Color correction should ideally produce output colors that are independent of the spec-
tral sensitivity and color crosstalk characteristics of the image sensor. The optimal values
of the color correction matrix elements depend on those sensor characteristics and on
the spectrum of light incident on the sensor. The color correction settings can be
adjusted using variables.
To increase image sharpness, a programmable 2D aperture correction (sharpening filter)
is applied. The gain and threshold for 2D correction can be defined through variable
settings.
The gamma correction curve (as shown in Figure 23) is implemented as a piecewise
linear function with 19 knee points, taking 12-bit arguments and mapping them to 8-bit
output. The abscissas of the knee points are fixed at 0, 64, 128, 256, 512, 768, 1024, 1280,
1536, 1792, 2048, 2304, 2560, 2816, 3072, 3328, 3584, 3840, and 4096. The 8-bit ordinates
are programmable through variables.
The MT9M114 IFP includes a block for gamma correction that has the capability to
adjust its shape, based on brightness, to enhance the performance under certain
lighting conditions.
Two custom gamma correction tables may be uploaded, one corresponding to a contrast
curve for brighter lighting conditions, the other one corresponding to a noise reduction
curve for lower lighting conditions. Also included in this block is a Fade-to Black curve
which sets all knee points to zero and causes the image to go black in extreme low light
conditions.
The MT9M114 has the ability to calculate the 19 point knee points based on a small
number of variable inputs from the host, another option is for the host to program one
or both of the 19 knee points. The diagram below shows how the gamma feature inter-
acts in MT9M114.
MT9M114/D Rev. 11, 2/16 EN
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