3.4.5

Autoexposure

The autoexposure (AE) feature computes and automatically applies the ideal exposure time and gain factors to

get the optimum average luminance in the image. The autoexposure algorithm is performed directly in the sensor,

to benefit from automatic exposure without the need to develop any dedicated algorithm or to allocate processor

resources to the computation.

The sensor can also operate in manual mode where exposure parameters are provided by the host.

The host can configure autoexposure module parameters that control brightness target, convergence speed, and

stability. The region of interest (ROI) used for autoexposure can be set independently from the image capture

region.

A specific antiflickering mode can be selected to mitigate artifacts introduced by ambient light frequency and

frame rate differences.

A dedicated I2C status register provides the image average brightness information when the sensor is set to

autoexposure or manual exposure mode. This information is also available in the status lines (ISL) embedded at

the beginning of each frame. Refer to Section 3.4.8: Embedded status lines for ISL description.

3.4.6

Analog subsampling

The devices support x2 and x4 subsampling which reduces overall image size and keeps the same field of view

(FoV). Subsampling is applied vertically and horizontally during the ADC readout, where every two or every four

pixels are read. When subsampling is used, the frame rate can be increased by decreasing the frame length.

3.4.7

Digital binning

The digital binning process reduces the image resolution by a factor of 2 or 4 in each direction. Central and

neighboring pixels are weighted to produce the digital binned image, avoiding special phase shift and artifacts

which may occur on the output image. Digital binning and subsampling are mutually exclusive.

3.4.8

Embedded status lines

The output interface (OIF) embeds the intelligent status line generator, which allows metadata to be sent through

the MIPI image data interface. The ISL follows the SMIA CSI-2, simplified, 2-byte, tagged data format for RAW8

data packing. There are two ISL lines transmitted at the beginning of each frame. Each data packet is 256 bytes

long. The length of the ISL can be stretched to equal the active line packet size.

The MCU has access to a bank of status registers, refreshed at each frame, and providing detailed information on

the current state of the sensor. Most of the content of this bank is also available in ISLs. The ISL contains all

information related to the current transmitted frame such as:

•

Clock settings

•

Cropping and orientation parameters

•

Analog and digital gains

•

Integration time

•

Frame counter index

•

Thermal sensor values

•

Dark calibration parameters

Transmission of ISL data packets can be disabled by configuring a static register during SW_STANDBY state

before streaming. ISL data packets have their own programmable "data types" and "virtual channels".

VD66GY

Functional description

DS13838 - Rev 7

page 9/37