Linea HS Series Camera User's Manual Camera Features • 29
Dual Exposure Mode (HDR)
Some inspection applications may have areas where specific features must be identified that have
very bright and very darks areas within the same field of view. Optimizing for the bright areas may
result in too much noise to detect features in dark areas and optimizing for the dark areas may
result in saturating the image in bright areas.
TeledyneDALSA CIS module has a dual exposure mode that can overcome these opposing
requirements by imaging with a long exposure time for one row while concurrently imaging with a
short exposure for a second row. The long exposure time row can be configured to detect the
desired features in the dark areas while the short exposure can be configured to detect features in
the bright areas.
To set up dual exposure mode see the ExposureMode, ExposureTime and exposureTimeSelector
features.
The maximum long exposure time is dictated by the period of the line rate. The minimum short
exposure times is 2µs. Therefore, the ‘dynamic range’ from dark to bright areas can be very large
as dictated by the line rate and available illumination intensity.
The long and short exposure time rows are output from the module separately, one after the other,
and captured by the frame grabber as two image panes that can be processed separately or
appropriately combined by the user to meet their specific needs.
Since two rows are being processed in dual exposure mode, the maximum line rate is half that with
normal monochrome imaging, i.e. 60KHz maximum.
The two rows are spatially separated in the scan direction. However, the module ensures the long
and short exposure time images are aligned. If the modules is at an angle or the encoder
resolution is not 42um for 600dpi or 28um for 900dpi, use the moduleAngle and/or the
scanDirectionObjectPixelSize features to enter the systems configuration to ensure image
alignment.
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