ASX340CS datasheet(20/74 Pages) ONSEMI

20 / 74 page

ASX340CS_DS Rev. F Pub. 6/15 EN

©Semiconductor Components Industries, LLC, 2015.

ASX340CS: 1/4-Inch Color CMOS NTSC/PAL Digital Image Sensor

Sensor Pixel Array

Black Level Subtraction and Digital Gain

Image stream processing starts with black level subtraction and multiplication of all

pixel values by a programmable digital gain. Both operations can be independently set

to separate values for each color channel (R, Gr., Gb, B). Independent color channel

digital gain can be adjusted with registers. Independent color channel black level adjust-

ments can also be made. If the black level subtraction produces a negative result for a

particular pixel, the value of this pixel is set to 0.

Positional Gain Adjustments (PGA)

Lenses tend to produce images whose brightness is significantly attenuated near the

edges. There are also other factors causing fixed pattern signal gradients in images

captured by image sensors. The cumulative result of all these factors is known as image

shading. The ASX340CS has an embedded shading correction module that can be

programmed to counter the shading effects on each individual R, Gb, Gr., and B color

signal.

The Correction Function

The correction functions can then be applied to each pixel value to equalize the

response across the image as follows:

(EQ 1)

where P is the pixel values and f is the color dependent correction functions for each

color channel.

20-263

Active video

264-265

Blanking

266-282

Blanking

283-525

Active Video

Table 7:

PAL

Line Numbers

Field

Description

1-22

Blanking

23-310

Active video

311-312

Blanking

313-335

Blanking

336-623

Active video

624-625

Blanking

Table 6:

NTSC (continued)

Line Numbers

Field

Description

Pcorrected(row,col)=Psensor(row,col)*f(row,col)

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