Color imaging apparatus employing a horizontal stripe color filter to reduce rise-time artifacts

• US 4,896,207 A
• Filed: 06/17/1988
• Issued: 01/23/1990
• Est. Priority Date: 06/17/1988
• Status: Expired due to Term

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Parulski, Kenneth A.
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): Powell, Mark R.
• Application Number:
  US07/208,302
• Time in Patent Office: 585 Days
• Field of Search: 358/41, 358/43, 358/44
• US Class Current: 348/242
• CPC Class Codes: H04N 23/843 Demosaicing, e.g. interpolating colour pixel values
• CPC Class Codes: H04N 23/88 for colour balance, e.g. white-balance circuits or colour temperature control
• CPC Class Codes: H04N 25/134 based on three different wavelength filter elements
• CPC Class Codes: H04N 25/135 based on four or more different wavelength filter elements
• CPC Class Codes: H04N 25/136 using complementary colours
• CPC Class Codes: H04N 25/447 by preserving the colour pattern with or without loss of information

Abstract

Video imaging apparatus avoids rise-time artifacts due to analog bandwidth limitations by orienting a multi-green color filter array so that the luminance (green) elements are parallel to the high-speed, horizontal line scanning direction. Rise-time delays in the analog signal processing due to high frequency horizontal scanning are accommodated by having the critical green elements side-by-side in the horizontal direction rather than separated by red and blue elements. This additionally permits line-by-line switching during signal processing to correct for color balance.

Claims

1. Imaging apparatus for generating a color video representation of an object, said apparatus comprising:

an area image sensor having a high speed horizontal scan and a relatively lower speed vertical scan, said sensor having a plurality of light-sensitive areas arranged two-dimensionally in parallel lines each oriented lengthwise in the horizontal high speed scanning direction;

a color filter array having parallel horizontal lines of colored filter elements overlying respective lines of light-sensitive areas, said color filter array having a vertically repetitive pattern comprising at least three adjacent lines of same-color filter elements oriented in the horizontal scanning direction and a line of filter elements including at least one other color oriented in the horizontal scanning direction; and

means for horizontally and vertically scanning said image sensor and for generating an output signal, said output signal comprising a repetitive color video sequence of at least three lines of the same color and one line including said other color.

2. Imaging apparatus as claimed in claim 1 in which said adjacent lines of the same-color filter elements comprise lines of luminance-responsive filter elements.

3. Imaging apparatus as claimed in claim 2 in which said line of filter elements including at least one other color comprises a line of chrominance-responsive filter elements.

4. Imaging apparatus as claimed in claim 1 in which said two lines of same-color filter elements comprise at least three adjacent lines of green filter elements.

5. Imaging apparatus as claimed in claim 4 in which said line of filter elements including at least one other color comprises a repetitive sequence of red and blue filter elements.

6. Imaging apparatus for generating a color video representation of an object, said apparatus comprising:

an area image sensor having a high speed horizontal scan and a relatively lower speed vertical scan, said sensor having a plurality of light-sensitive areas arranged two-dimensionally in parallel lines each oriented lengthwise in the horizontal high speed scanning direction;

a color filter array segmented into parallel horizontal lines of colored filter elements overlying respective lines of light-sensitive areas, said color filter array having a vertically repetitive pattern comprising at least three adjacent lines of filter elements of the same color oriented in the horizontal scanning direction and a line of filter elements including a repetitive sequence of two or more colors oriented in the horizontal scanning direction;

means for horizontally and vertically scanning said image sensor and for generating an output signal, said output signal comprising a line repetitive color video sequence of at least three lines of one continuous color and one line of an alternating sequence of colors;

a gain-controlled processing stage for processing said output signal, said processing stage being switched between one gain value for the lines of continuous color and at least one other gain value for the line of alternating color; and

means for switching between said gain values on a line-by-line basis.

7. Imaging apparatus as claimed in claim 6 in which said vertically repetitive pattern comprises three adjacent lines of green filter elements bordered by a line of alternating red and blue filter elements.

8. In a color imaging system of the type having a color-responsive image sensor and a color filter interpolation sequence based on one color filter element being separated by two or more filter elements of a luminance-responsive color, said system operating in an electrical environment requiring high processing frequencies and having a propensity for crosstalk between colors caused by rise-time delays in an ancillary analog processing circuit;

the improvement wherein the imaging system comprises;

an area image sensor having a high speed horizontal scanning frequency and a relatively lower speed vertical scanning frequency, said sensor having a plurality of light-sensitive photosites arranged two-dimensionally in parallel lines each oriented lengthwise in the horizontal high speed scanning direction; and

a color filter array segmented into parallel horizontal lines of colored filter elements overlying respective lines of photosites, said color filter array having a vertically repetitive pattern comprising at least two adjacent lines of the luminance-responsive color filter elements oriented in the horizontal scanning direction bordered by a line of filter elements including a repetitive sequence of two or more colors oriented in the horizontal scanning direction, said area image sensor in combination with said color filter array providing a sequential input signal for said interpolation sequence comprising at least two adjacent lines of luminance-responsive color filter elements separated by single lines of filter elements including said two or more colors, said vertically repetitive pattern orienting the color filter interpolation sequence in the lower-speed vertical scanning direction so that color crosstalk is minimized.

9. An imaging system as claimed in claim 8 in which said vertically repetitive pattern comprises three adjacent lines of green filter elements bordered by a line of alternating red and blue filter elements, said vertically repetitive pattern orienting the color filter interpolation sequence in the vertical direction so that a vertical array of three green filter elements on either side of a red or blue filter element are used in the interpolation sequence.