One-chip color camera that can suppress generation of pseudo...

Details One-chip color camera that can suppress generation of pseudo... One-chip color camera that can suppress generation of pseudo...

1999-03-05

2004-11-23

Christensen, Andrew (Department: 2615)

Television

Camera, system and detail

With single image scanning device supplying plural color...

C348S279000, C358S518000, C358S520000, C358S525000

Reexamination Certificate

active

06822680

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to color cameras, and particularly to a one-chip color camera including a color separation circuit for processing a signal from a solid state image sensing device with photoelectric conversion elements arranged in an array corresponding to color filters arranged in an array.
2. Description of the Background Art
In a color camera, the CCD (Charge Coupled Device) that is currently widely used as an image sensing device simply alters the amplitude of the output signal according to the brightness of the received light. Color information is not included in the output signal. It is therefore necessary to provide some optical means to obtain color information such as filtering the light incident on the CCD.
For color cameras of personal usage, the so-called one-chip system of extracting signals of the three, primary colors from a single CCD is employed. The so-called simultaneous color image sensing system using a color filter array at the light receiving side of the CCD is adopted.
[Structure of Inter-line Transfer CCD]
FIG. 24
is a schematic block diagram showing a structure of an inter-line transfer CCD
10
that is generally used as the CCD of a color camera for domestic usage.
Inter-line transfer CCD
10
includes a photosensitive unit
12
formed of pn junction type photodiodes arranged in an array, a transfer unit
14
including an analog register formed of CCDs, and a horizontal transfer register
16
receiving the charge from CCD analog shift register (transfer unit)
14
to transfer in the horizontal direction a signal corresponding to the sequentially transferred signal charge converted into voltage for output.
In
FIG. 24
, the pn junction type photodiodes are shown to correspond to three pixels arranged in both the vertical and horizontal directions for the sake of simplification. In practice, photodiodes corresponding to 500 pixels in the vertical direction and 500-800 pixels in the horizontal direction, for example, are arranged in an array for the CCD employed in a color camera.
The operation will be described briefly here.
When light enters a photodiode, charge is generated to be accumulated in the diode. Then, application of a predetermined voltage on a shift gate (well known but, for simplicity, not shown) causes all the accumulated charge to be transferred to analog shift register
14
. CCD analog shift register
14
responds to application of clock pulse voltages &phgr;V
1
, &phgr;V
2
and &phgr;V
3
to transfer the charge sequentially towards horizontal transfer register
16
. In horizontal transfer register
16
, the received signal charge is converted into voltage to be sequentially output as an image sensed signal driven by externally applied horizontal drive signals &phgr;H
1
, &phgr;H
2
and &phgr;H
3
.
[Driving Method of Inter-line Transfer CCD]
As the method of driving the inter-line transfer CCD, there are generally two modes, i.e., the frame accumulation system and the field accumulation system. Some color cameras employ the frame accumulation system that is based on an entire-pixel readout operation even for the color filter array of the color difference sequential system.
In the following, an inter-line transfer CCD operating in a frame accumulation mode that can read out for every pixel is contemplated.
[Structure of Conventional One-Chip Color Camera]
FIG. 25
is a schematic block diagram showing a structure of main components of a conventional one-chip color camera
2000
.
One-chip color camera
2000
mainly includes an optical system
2
receiving light from an object of interest, a CCD
10
converting an optical image formed by optical system
2
into an electric signal, a drive circuit
2102
that drives to read out independently all the pixels for CCD
10
, and a color separation circuit
2101
receiving the output signal from CCD
10
to output three primary color signals R, G and B corresponding to each pixel.
Color separation circuit
2101
includes a C
L
C
R
C
B
generation circuit
2104
that receives the signal output from CCD
10
to generate a luminance signal C
L
and color difference signals C
R
and C
B
, a random access memory
2106
(referred to as RAM hereinafter) to transfer a read out signal D (x, y), luminance signal C
L
, and color difference signals C
R
and C
B
, with C
L
C
R
C
B
generation circuit
2104
, and that can retain these signals corresponding to at least one scanning line, and a matrix circuit
2108
that receives a signal from C
L
C
R
C
B
generation circuit
2104
to separate the three primary color signal RGB by a predetermined operation for output.
In one-chip color camera
2000
of
FIG. 25
, CCD
10
carries out a readout operation of all the pixels independently as mentioned above. More specifically, drive circuit
2102
generates a drive pulse that does not mix two pixels in the vertical direction in CCD
10
.
[Method of Separating Color Difference Signal]
FIG. 26
is a schematic diagram of an arrangement of the color filter array for describing signal read out from CCD
10
including such a color filter array in a conventional one-chip color camera.
In the color difference sequential system shown in
FIG. 26
, color filters of magenta (represented as Mg hereinafter), green (represented as G hereinafter), cyan (represented as Cy hereinafter) and yellow (represented as Ye hereinafter) are arranged in a mosaic manner.
Since the so-called additive color process is applicable in the mixture of the color of light, the following relationship between the three primary colors of red (R), green (G) and blue (B) and the complementary colors of Mg, Ye and Cy is established.
Mg=R+G
  (1)
Ye=R+G
  (2)
Cy=B+G
  (3)
By using the above Mg, G, Ye and Cy as the colors of the color filters, the intensity of the G signal having a great weight for the luminance signal out of the three primary colors of R, G and B can be set greater than that of the R and B signals.
[Generation of Pseudo Color signal]
As shown in
FIG. 26
, color filters Mg and G are arranged alternately in the horizontal direction (x direction) as to the 0-th line in the 0-th order in the vertical direction (y direction). Correspondingly, the signals of Mg and G are output alternately from CCD
10
as to the scanning line corresponding to this line. As to the next first line (corresponding to y=1), signals of Ye and Cy are output alternately.
Thus, the following relationship is established between each pixel (x, y) and the filter color in the CCD output signal when n is a natural number.
i) When y=4n−3 or 4n−1 (i.e., y=1, 3, 5 . . . ):
When x is an even number, the color filter is Ye.
When x is an odd number, the color filter is Cy.
ii) When y=4n−4 (i.e., y=0, 4, 8, . . . ):
When x is an even number, the color filter is Mg.
When x is an odd number, the color filter is G.
iii) When y=4n−2 (i.e., y=2, 6, 10, . . . ):
When x is an even number, the color filter is G.
When x is an odd number, the color filter is Mg.
For the purpose of convenience, the row corresponding to the color filters of Mg and G is an even numbered line, and the row corresponding to the color filters of Ye and Cy is an odd numbered line. However, the same applies for a color filter arrangement shifted by one line, for example, as will be apparent from the following description.
[Generation of Color Difference Signal from Four Pixels Fixed with Respect to Pixel (x, y)]
As mentioned above, signals are read out independently for all the pixels from CCD
10
. These signals are retained in RAM
2106
.
Therefore, a luminance signal C
L
(x, y), a first color difference signal C
R
(x, y) and a second color difference signal C
B
(x, y) for each pixel (x, y) can be generated by the following operation respectively.
In the following, the signal output from the photoelectric conversion element corresponding to a pixel (x

Affiliated with

Also associated with

Rating

One-chip color camera that can suppress generation of pseudo... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with One-chip color camera that can suppress generation of pseudo..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and One-chip color camera that can suppress generation of pseudo... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3325295