Is_Exposure - THORLABS DCU223x Operation Manual And Sdk

DCx Cameras

4.3.26 is_Exposure

USB 2.0
USB 3.0
Syntax
INT is_Exposure (HIDS hCam, UINT nCommand, void* pParam, UINT cbSizeOfParam)
Description
Using is_Exposure() you can query the exposure time ranges available in your camera, and set new exposure
times.
The nCommand input parameter is used to select the function mode. The pParam input parameter depends on the
selected function mode. If you select functions for setting or returning a value, pParam contains a pointer to a
variable of the UINT type. The size of the memory area to which pParam refers is specified in the
cbSizeOfParam input parameter.
Notes
1. Dependencies on other settings
The use of the following functions will affect the exposure time:
is_PixelClock()
is_SetOptimalCameraTiming()
is_SetFrameRate()
(if the image size is changed)
is_AOI()
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is_SetSubSampling()
is_SetBinning()
Changes made to the image size, the frame rate or the pixel clock frequency also affect the exposure time. For this
reason, you need to call is_Exposure() again after such changes.
2. New driver versions
Newer driver versions sometimes allow an extended value range for the exposure time setting. We recommend
querying the value range every time and set the exposure time explicitly.
Applying new settings
In freerun mode (is_CaptureVideo()
when the next image but one is captured. In trigger mode
be applied to the next image. See also the
Accuracy of the exposure time setting
The increments for setting the exposure time (IS_EXPOSURE_CMD_GET_EXPOSURE_RANGE_INC) depend on the
sensor's current timing settings (pixel clock, frame rate). The smallest increment usually corresponds to the
duration of one pixel row, which is the time it takes the sensor to read out one pixel row.
You can query the actual exposure time setting with the IS_EXPOSURE_CMD_GET_EXPOSURE parameter.
Some sensors allow setting the exposure time in smaller increments. Using the IS_EXPOSURE_CMD_GET_CAPS
parameter, you can check whether your sensor supports this function.
For minimum and maximum exposure times as well as other sensor-based dependencies, please refer to the
Camera and sensor data
Rounding errors from increments
When calculating a new exposure time based on the returned increment, note that calculations with floating point
values in the PC will always be subject to rounding errors. Therefore, an addition or subtraction of the
n*INCREMENT value might not always produce the exact desired result. In this case, the uc480 API rounds down
the floating point value and sets the exposure time to the next lower value.
You can avoid this behavior by additionally adding the value INCREMENT/2.f (half increment) when calculating
with n*INCREMENT. This ensures that the desired value will be set even after rounding.
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USB 2.0
USB 3.0
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338
329
347
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), any modification of the exposure time will only become effective
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Applying new parameters
chapter.
460
(is_SetExternalTrigger()
chapter.
46
), the modification will
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