Basic Operation and Features3-4 Basler A500k SeriesPRELIMINARY3.2 Exposure Time Control ModesA500k cameras can operate under the control of an external trigger signal (ExSync signal) or canoperate in “free-run.” In free-run, the camera generates its own internal control signal and doesnot require an ExSync signal.3.2.1 ExSync Controlled OperationIn ExSync operation, the camera’s frame rate and exposure time are controlled by an externallygenerated (ExSync) signal. The ExSync signal is typically supplied to the camera by a framegrabber board. You should refer to the manual supplied with your frame grabber board todetermine how to set up the ExSync signal that is being supplied to the camera.When the camera is operating under the control of an ExSync signal, the length of the ExSyncsignal period determines the camera’s frame rate. ExSync can be periodic or non-periodic.When the camera is operating with an ExSync signal, it has three modes of exposure time controlavailable: edge-controlled mode, level-controlled mode and programmable mode.• In ExSync, edge-controlled mode, the pixels are exposed and charge is accumulated overthe full period of the ExSync signal (rising edge to rising edge). The falling edge of theExSync signal is irrelevant. The frame is read out and transferred on the rising edge ofExSync (see Figure 3-4).Figure 3-4: ExSync, Edge-Controlled Mode• In ExSync, level-controlled mode, the exposure time is determined by the time between thefalling edge of ExSync and the next rising edge. The pixels are exposed and charge is accu-mulated only when ExSync is low. The frame is read out and transferred on the rising edge ofthe ExSync signal (see Figure 3-5).Figure 3-5: ExSync, Level-controlled ModeExSyncExposureFrame Read OutExSync PeriodExSyncExSync PeriodFrame Read OutExposure
