Introduction

The CMOS sensor module (MT9M034) incorporates the following features:

resolution to 1280 x 960 gray scale or RGB Bayer mosaic
supports window AOI mode with faster readout
programmable analog gain (0..12 dB)
progressive scan sensor (no interlaced problems!)
high dynamic range 115 dB (with gray scale version)
rolling shutter
programmable readout timing with free capture windows and partial scan
many trigger modes (free-running, hardware-triggered)

Details of operation

The sensor uses following acquisition mode:

rolling shutter (ShutterMode = "ElectronicRollingShutter")

With the rolling shutter the lines are exposed for the same duration, but at a slightly different point in time.

Note: Moving objects together with a rolling shutter can cause a shear in moving objects.

Furthermore, the sensor offers following operating modes:

free running mode (Overlapping exposure and readout)
snapshot mode (Sequential exposure and readout)

Free running mode

In free running mode, the sensor reaches its maximum frame rate. This is done by overlapping erase, exposure and readout phase. The sensor timing in free running mode is fixed, so there is no control when to start an acquisition. This mode is used with trigger mode Continuous.

To calculate the maximum frames per second (FPS_max) in free running mode you will need following formula:

FrameTime = (ImageHeight * (1650 / PixelClock)) + (25 * (1650 / PixelClock))

If exposure time is lower than frame time:

FPS_max =            1
           ----------------------
                 FrameTime

If exposure time is greater than frame time:

FPS_max =            1
           ------------------------
                ExposureTime

Snapshot mode

In snapshot mode, the image acquisition process consists off several sequential phases:

Trigger

Snapshot mode starts with a trigger. This can be either a hardware or a software signal.

The following trigger modes are available:

Mode	Description
Continuous	Free running, no external trigger signal needed.
OnLowLevel	As long as trigger signal is Low camera acquires images with own timing.
OnHighLevel	As long as trigger signal is High camera acquires images with own timing.

See also: Using external trigger with CMOS sensors

Erase, exposure and readout

All pixels are light sensitive at the same period of time. The whole pixel core is reset simultaneously and after the exposure time all pixel values are sampled together on the storage node inside each pixel. The pixel core is read out line-by-line after exposure.

Note: Exposure and read out cycle is carry-out in serial; that causes that no exposure is possible during read out.

The step width for the exposure time is 1 us.

Image data is then shifted out line-by-line and transferred to memory.

To calculate the maximum frames per second (FPS_max) in snapshot mode you will need following formula:

FrameTime = (ImageHeight * (1650 / PixelClock)) + (25 * (1650 / PixelClock))

FPS_max =                  1
           -----------------------------------
                 FrameTime + ExposureTime

Measured frame rates

AOI	PixelClock (MHz)	Exposure Time (us)	Maximal Frame Rate (fps)	PixelFormat
Maximum	40	100	24.6	Mono8
W:1036 x H:776	40	100	30.3	Mono8
W:838 x H:627	40	100	37.1	Mono8
W:678 x H:598	40	100	38.9	Mono8
W:550 x H:484	40	100	47.6	Mono8

Sensor Data

Device Structure

CMOS image sensor (Type 1/3")
Number of effective pixels: 1280 (H) x 960 (V)
Unit cell size: 3.75um (H) x 3.75um (V)

Characteristics

Color version

Gray scale version

Device Feature And Property List