AR0130CSSC00SPBA0-DP1 datasheet(20/40 Pages) ONSEMI

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AR0130CS

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Embedded Statistics

The embedded statistics contain frame identifiers and

histogram information of the image in the frame. This can be

used by downstream auto−exposure algorithm blocks to

make decisions about exposure adjustment.

This histogram is divided into 244 bins with a bin spacing

of 64 evenly spaced bins for digital code values 0 to 212, 120

evenly spaced bins for values 212 to 216, 60 evenly spaced

bins for values 216 to 220.

The first pixel of each line in the embedded statistics is a

tag value of 0x0B0. This signifies that all subsequent

statistics data is 10 bit data aligned to the MSB of the 12−bit

pixel.

The figure below summarizes how the embedded

statistics transmission looks like. It should be noted that

data, as shown in Figure 19, is aligned to the msb of each

word:

Figure 19. Format of Embedded Statistics Output within a Frame

lowEndMean

[19:10]

stats line 1

stats line 2

histogram

bin1 [9:0]

#words =

10’h1EC

{2’b00, frame

_count MSB}

{2’b00, frame

_ID MSB}

{2’b00, frame

_ID LSB}

histogram

bin0 [19:10]

histogram

bin0 [9:0]

histogram

bin1 [19:10]

data_format_

code =8’h0B

#words =

10’h1C

mean [ 19:10]

mean [9:0]

hist_begin

[19:10]

hist_begin

[9:10]

8’h07

data_format_

code =8’h0B

{2’b00, frame

_count LSB}

8’h07

histogram

bin243 [19:10]

histogram

bin243 [9:0]

8’h07

hist_end

[19:10]

hist_end

[9:10]

lowEndMean

[9:0]

perc_lowEnd

[19:10]

perc_lowEnd

[9:0]

norm_abs_dev

[19:10]

lnorm_abs_dev

[9:0]

The statistics embedded in these rows are as follows:

Line 1:

• 0x0B0 − identifier

• Register 0x303A − frame_count

• Register 0x31D2 − frame ID

• Histogram data − histogram bins 0−243

Line 2:

• 0x0B0 (identifier)

• Mean

• Histogram Begin

• Histogram End

• Low End Histogram Mean

• Percentage of Pixels Below Low End Mean

• Normal Absolute Deviation

Gain

Digital Gain

Digital gain can be controlled globally by R0x305E

(Context A) or R0x30C4 (Context B). There are also

registers that allow individual control over each Bayer color

(GreenR, GreenB, Red, Blue).

The format for digital gain setting is xxx.yyyyy where

0b00100000 represents a 1x gain setting and 0b00110000

represents a 1.5x gain setting. The step size for yyyyy is

0.03125 while the step size for xxx is 1. Therefore to set a

gain of 2.09375 one would set digital gain to 01000011.

Analog Gain

The AR0130 has a column parallel architecture and

therefore has an Analog gain stage per column.

There are two stages of analog gain, the first stage can be

set to 1x, 2x, 4x or 8x. This is can be set in

R0x30B0[5:4](Context A) or R0x30B0[9:8] (Context B).

The second stage is capable of setting an additional 1x or

1.25x gain which can be set in R0x3EE4[8].

This allows the maximum possible analog gain to be set

to 10x.

Black Level Correction

Black level correction is handled automatically by the

image sensor. No adjustments are provided except to enable

or disable this feature. Setting R0x30EA[15] disables the

automatic black level correction. Default setting is for

automatic black level calibration to be enabled.

The automatic black level correction measures the

average value of pixels from a set of optically black lines in

the image sensor. The pixels are averaged as if they were

light−sensitive and passed through the appropriate gain.

This line average is then digitally low−pass filtered over

many frames to remove temporal noise and random

instabilities associated with this measurement. The new

filtered average is then compared to a minimum acceptable

level, low threshold, and a maximum acceptable level, high

threshold. If the average is lower than the minimum

acceptable level, the offset correction value is increased by

a predetermined amount. If it is above the maximum level,

the offset correction value is decreased by a predetermined

amount. The high and low thresholds have been calculated

to avoid oscillation of the black level from below to above

the targeted black level. At high gain, long exposure, and

high temperature conditions, the performance of this

function can degrade.

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