Hand Held Products IMAGETEAM IT4000HD, Руководство по интеграции

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2 - 4 IMAGETEAM™ 4X00 Series Integration Manual
Vertical
The vertical timing is configured with the active row start value (reg 0x15, 0x14) where the last 485 active rows, or lines of video,
of a 525 row frame are output immediately after the leading edge of the vertical signal, and the first five rows appear at the end
of the frame. The vertical pulse end is set to occur at row 480. The acquisition circuit acquires while the vertical signal is low.
Therefore, the circuit acquires data only during the low vertical window created by these settings.
Vertical data valid window data alignment:
The window is derived so the first and last 5 light shielded rows are ignored. Other row count value combinations are possible.
Horizontal
The horizontal pixel alignment and timing is similar to the vertical. The imager inverts the horizontal signal, Hsync end is set to
640, frame width (row length) is 858 pixel clocks per row, and the data is positioned at column start 853. This configuration
creates a window that presents the last 853 pixels first (640 + 5 light sh 28 blanks), and the first 5 light shielded pixels at
the end of the row.
Horizontal data valid window data alignment:
Interdependencies
Column Position of CDS Subtraction Pulse (Reg. 0x9C, 0x9B)
The register value for the CDS subtractive pulse must be considered when adjusting the frame width (FW) and the start of active
data column settings. As noted in the
Control Register Table (see page 2-2), this value must be less than the value entered for
FW. If CDS is greater than FW, the imager produces very strange video data results.
The IT4X00 Series engine does not perform the Correlated Double Sampling (CDS) method as the pixel’s value is read and
converted. The correlation samples are taken on a row basis. This means that the correlation samples for an entire row (line)
are taken when the row is reset prior the start of integration. The position of this correlation sample, selected by these registers,
determines when the correlation sample value is subtracted from the integration value of the video samples for each horizontal
line. The ideal column setting for the CDS subtractive pulse is at the end of the row after the active pixel data. Placing the
subtractive pulse during active pixel data leads to unpredictable results.
Exposure vs. Frame Height (Number of Lines per Frame)
The exposure is controlled by setting the number of rows (lines) to allow the pixels to acquire charge (row as a measure of
integration time based on RowCount * T
row
). The frame height must be set to a minimum value equal to the total number of active
lines (490), or to a number of rows that is greater than or equal to the exposure setting, but not greater than the maximum value
of 1023 ( [490 or Exp] < FH < 1023).
Vertical
Row Data
Horizontal
Row Data