25/02/13How does the rolling shutter camera achieve the global shooting effect?
The rolling shutter camera uses the external trigger mode, which can achieve the shooting effect of the global shutter camera through the accurate control of the time sequence.
Here, Dhyana 400BSI V3 is an example to illustrate the implementation of the scheme:
1) Standard Trigger Mode to realize Global Patterns
As shown in the timing of the figure above, the standard trigger mode is selected. When the camera receives the external trigger signal, after a readout time T2, all pixels will be in the simultaneous exposure state. Therefore, the global output signal of the camera to the laser pulse device after T2 to control the open laser signal. That is, by allowing the signal of the static or transient shooting sample to fall in the time of T=T1-T2, all the signals can be captured to achieve the global effect.
The scheme needs to ensure that the exposure time is greater than the readout time, i.e., there is a range of global signal to be effective. Read out time = line cycle * number of lines, the line cycle is the shortest exposure time of the camera, each gain mode of each camera has a corresponding line cycle, please refer to the user manual of each camera for details.
2) Global reset mode goes for global patterning.
This scheme is only for cameras with a global reset function, such as Dhyana400BSIV3, Aries16, etc.
Entering the global reset mode, the camera will pixel reset all lines, and when the external trigger signal is received, all lines start exposure at the same time. The global effect can also be achieved by exposing the sample signal to the Exp shown in Fig. It should be noted that the exposure time of each line in this mode is not consistent, and the actual exposure time increases line by line, so it is recommended to use the Readout to read out this period for shading treatment.
Compared to the standard trigger mode simulating the global effect, the scheme does not require an exposure time greater than the readout time.
