JAI TMC-4200GE User Manual download pdf (Page 64)

Page 52

TM-4200GE Hardware

Operation

9 Operation

9.1 Progressive Scanning

Standard TV-system scanning is 525 lines interlace scanning as specified in the RS-170 protocol. Every

other horizontal line (odd lines and even lines) is scanned at a 60Hz rate per field, and the scanning is

completed with two fields (one frame) at 30Hz rate. Because of the interlace scanning, the vertical

resolution of CCD cameras is limited at 350 TV lines, regardless of the horizontal resolution. When

electronic shutter is applied, the CCD can hold only one field of charge at each exposure. This means

that the vertical resolution of the electronic-shutter camera is only 244 TV lines. The situation is the

same for an HDTV-format camera, since it has interlaced scanning and the vertical resolution of the

shuttered image is 500 lines.

The TM-4200CL uses a state-of-the-art progressive scanning interline transfer CCD which scans all

lines sequentially from top to bottom at one frame rate. Like a non-interlace computer screen, it

generates a stable, crisp image without alternating lines and provides full vertical TV resolution of 1000

lines (a normal TV monitor display may not be able to show 1000 lines due to monitor resolution of

30Hz scanning).

The interline transfer architecture is also important to generate simultaneous shuttering. This is different

from full frame transfer architecture which requires a mechanical shutter or strobe light in order to

freeze the object motion.

9.1.1 Preset Scan Area

TM/TMC-4200 has four fixed Scan Area Modes: full scan, centered 1000 lines, centered 500 lines, and

centered 250 lines. In full scan mode, all active lines of the CCD sensor, 2048 lines, are transferred out

line by line. In centered mode 1000 lines are transferred out, in 500 line and 250 line mode, only the

centered lines are transferred out line by line. The rest of the lines are dumped out using the fast dump

function of the CCD. This transfer method causes the frame rate of each mode to vary.

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JAI TMC-4200GE User Manual Page 64