Configuring Exposure Time; Frame Rate Calculation - Hamamatsu Photonics C11440-36U Instruction Manual

9-6

CONFIGURING EXPOSURE TIME

The exposure time can be set with the absolute value by the command in Free running mode,
Edge trigger or Start trigger mode. The actual exposure time setting is defined by the following
formula, and the camera automatically calculates a larger and closest value from the specified
exposure time setting. And the exposure times in Level trigger mode and Synchronous readout
trigger mode are determined by a trigger signal from the outside.
Available setting range of the exposure time is 26.17 µs to 10 s in Free running mode, Edge
trigger mode, and Start trigger mode, and 1 ms to 1 s in Level trigger mode and Synchronous
readout trigger mode.
• In the case of Level trigger and Synchronous readout trigger mode, jitter which is up to 1H (≈
12.4 µs) might be included in exposure time
9-7

FRAME RATE CALCULATION

The frame rate is calculated as below.
In Free running mode, in External trigger mode (Synchronous readout trigger and Start trigger) and
Software trigger mode (Start trigger mode);
In External trigger mode (Edge trigger mode , Level trigger mode) and Software trigger mode (Edge
trigger mode);
• In the case of Edge trigger mode, Level trigger and Synchronous readout trigger mode, there are
some jitters and delays between a trigger input timing and an exposure start timing. Therefore, it
has possibility not to reach frame rate which is calculated by using above formula in some case.
Exposure time = N × 1H + 13.73 µs
N: Integer number (1 to 803 572)
1H = (1 / 37.125 MHz) × 462 clk ≈ 12.4 µs
N ＞ (Vn + 28)
N ≦ (Vn + 28)
1/(((Vn + 38) × 1H) + Exposure time)
N = ROUNDUP((Exposure time – 13.75 µs) / 1 H)
Vn: Width of vertical line (2 to 1200)
1H = (1 / 37.125 MHz × 462 clk ≈ 12.4 µs
C11440-36U Instruction Manual Ver.1.1
1 / Exposure time
1/((Vn + 38) × 1H)
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