Allied Vision Alvium Series - Factors for exposure time and frame rates; Sensor ADC readout modes for maximum frame rates

68Alvium USB Cameras User Guide V4.6.1
Specifications
Factors for exposure time and frame rates
• The default bandwidth for Alvium USB cameras is 200 MByte/s. For some
models, you can achieve higher frame rates by increasing values for
MaxTransferSize and DeviceLinkThroughputLimit. See Host setup and
bandwidth on page 306.
• Available values and increments for exposure time depend on other controls,
such as
DeviceLinkThroughputLimit. See Value changes by feature
interdependencies on page 301.
• For delays, see Exposure start delay = exposure area – exposure time. on page
289.
• Calculation of maximum frame rates for different ROIs for Alvium USB
cameras does not allow to give a formula. Operation for maximum frame rates
on page 69 defines the conditions for measuring ROI frame rates.
Sensor ADC readout modes for maximum frame rates
If you are using pixel formats that do not require 12-bit sensor ADC readout and
you want to achieve higher frame rates, you can select between readout modes for
12-bit, 10-bit, and 8-bit with some Alvium USB camera models. See your model’s
specifications.
By default, Alvium 1800 U models use the maximum bit depth for
SensorBitDepth. For selected models, Adaptive mode switches automatically
between 12-bit and 10-bit sensor ADC readout, depending on the bit depth of the
selected pixel format. This allows to reduce bandwidth and increase frame rates
when only 10-bit is required.
To enable the 8-bit sensor readout mode, you must switch manually, using
SensorBitDepth. Please observe that the image brightness changes when you
switch between 8-bit sensor ADC readout mode and the other readout modes.
Keep in mind that changing the output bit depth of the sensor also affects the
minimum available exposure time of the camera.
Graphics controller NVIDIA Quadro FX 580
USB controller Delock U3 PCIe 1XG205-1S Rev. 1.1
(2-port USB 3.0 to PCI Express x1 Gen 2 with Renesas
chipset)
Operating system Windows 7 Ultimate 64-bit SP1
Measured by Oscilloscope
Measured signal
ExposureActive
Maximum frame rates at different values for SensorBitDepth
When the maximum bandwidth supported by USB interface is reached, reducing
the value for
SensorBitDepth does not increase the available maximum frame
rate.
Component Property
Table 16: Test setup components