Basic Operation and FeaturesBasler A400k 3-9DRAFT3.4.1 Guidelines for Successful Use of the Rolling ShutterTo successfully use the rolling shutter functionality of the camera, make sure that you observe theguidelines listed below.• Exposure time can only be set incrementally in multiples of 4.56 μs. Formula:where N must be an integer and > 0. Exposure time can range from 4.56 μs to 19.12 s.• The runtime of the sensor reset and readout depends on the height of the area of interest(AOI, see page 3-24). The formula below can be used to calculate the runtime:Reset runtime = Readout runtime = 4.56 μs x (AOI Height - 1)• The formula below can be used to calculate the total time it takes to reset, expose and readout a single frame:Examples:(A) The height of the area of interest (AOI) is 1726 lines (full resolution):Total runtime = 4.56 μs x (1726 - 1) + Exposure time = 7866 μs + Exposure time(B) The height of the area of interest (AOI) is only 200 lines:Total runtime = 4.56 μs x (200 - 1) + Exposure time = 907.4 μs + Exposure time• Imaging of fast moving objects requires a flash exposure within the camera’s flash window(see Section 3.4.2).3.4.2 Flash Exposure for Fast Moving ObjectsImaging of fast moving objects requires a flash exposure. If flash exposure is not used, imagedistortions will occur due to the exposure’s 4.56 μs offset from one line to the next.Due to the exposure’s 4.56 μs offset from one line to the next, there is a limited time interval whereall pixel lines are open, that is, all pixels are exposed to light simultaneously. This time interval iscalled the “flash window“ of the camera (see Figure 3-9).The flash window opens when exposure is started in the last pixel line within the area of interest(AOI) and it closes when readout is started in the first pixel line within the AOI. The width of theflash window is calculated using the below formula:Flash window width [μs] = Exposure time [μs] - (AOI Height x 4.56 μs)A400k cameras output a flash trigger signal that can be used to trigger flash exposure. The flashtrigger signal can be programmed to be high as long as the flash window is open, that is, all pixellines are exposed to light and the flash should occur (see Section 2.5.8 on page 2-32).Exposure time N 4.56 μs×=Total frame exposure runtime 4.56 μs AOI Height 1–( ) Exposure time+×=
