Image analysis – Image compression or coding – Quantization
Reexamination Certificate
1998-09-24
2001-08-07
Tran, Phuoc (Department: 2621)
Image analysis
Image compression or coding
Quantization
C382S248000, C382S275000
Reexamination Certificate
active
06272259
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an image correcting apparatus fit for use in an imaging apparatus such as a digital still camera for processing image data compression, to an image data compressing apparatus using the image correcting apparatus and to an imaging apparatus fitted with the image correcting apparatus and the image data compressing apparatus. More particularly, the present invention relates to an image correcting apparatus for correcting conspicuous fixed image flaws and making them inconspicuous, when image data is compressed, wherein the fixed image flaws are produced in a regenerated image due to scratches on a lens, defective pixels of an imaging device and furthermore dust sticking to the surfaces of the lens and the imaging device, to an image data compressing apparatus using the image correcting apparatus and to an imaging apparatus fitted with the image correcting apparatus and the imaging data compressing apparatus.
FIG. 5
is a block diagram showing the configuration of a conventional imaging apparatus by way of example. The exemplary imaging apparatus
60
in
FIG. 5
essentially comprises a lens
62
, an imaging device
64
, an image processing circuit
66
, a compression circuit
68
and a frame memory
70
. An image formed through the lens
62
and inputted into the imaging device
64
such as CCD is converted into an image signal when subjected by the imaging device
64
to photoelectric conversion, converted by the image processing circuit
66
into a format of such as RGB, which is divided into image data on a block basis, encoded and compressed by the compression circuit
68
and stored in the frame memory
70
after the data quantity is reduced.
As the information volume of image data is generally large, data compressing techniques for reducing the information volume by compressing the image data are employed for such imaging apparatus as digital still cameras when the image data is transferred to personal computers or preserved in external storage units. There is a JPEG (Joint Photographic Experts Group) algorithm, for example, which is an international standard encoding system for still color images as one of the aforementioned techniques.
In the JPEG algorithm, encoding image data is sequentially carried out by, for example, dividing the image data into blocks of horizontal 8 pixels×vertical 8 pixels with a block as one unit. As shown in
FIG. 6
, in the compression circuit
68
, each image data in each block is converted into coefficients of frequency components by an orthogonal transformation circuit
72
, quantized by a quantization circuit
74
using a quantization table
73
and subjected by a variable-length encoding circuit
76
to variable-length encoding in order to make the image data a compressed data.
In the case of the aforesaid imaging apparatus
60
, fixed image flaws such as white points or black points are produced in a regenerated image due to, for example, scratches on the lens
62
, defective pixels of the imaging device
64
and furthermore dust sticking to the surfaces of the lens
62
and the imaging device
64
. In order to deal with the fixed image flaws, there have heretofore been followed the steps of making an inspection when products are forwarded, replacing the lens
62
and the imaging device
64
whenever the product has not met predetermined standards and carrying out reassembly of the parts when dust is involved. In consequence, there have developed problems in that a yield rate is lowered and that the products tend to become costly.
An image flaw correcting method for correcting defective pixels of an imaging device as one of the means for solving the problems above described has heretofore been proposed in, for example, Japanese Patent Laid-Open Publication No. 6-105241/1994. This image flaw correcting method is intended to calculate a matrix of constants and a matrix of coefficients of equations corresponding to discrete cosine transformation based on the defective pixels of the imaging device, calculate a solution of the equations from an inverse matrix of these matrix of constants and matrix of coefficients, and correct the defective pixels based on this solution.
Furthermore, this image flaw correcting method is said to be able to put CCDs which are more defective than before into practice, and to realize an inexpensive camera system in this result. However, this image flaw correcting method is aimed to correct image data relevant to defective pixels of the imaging device and the problem is that it is incapable of dealing with image flaws of the regenerated image due to scratches on the lens and dust sticking to the surfaces of the lens and the imaging device.
SUMMARY OF THE INVENTION
An object of the present invention made in view of the foregoing problems with reference to the prior art is to provide an image correcting apparatus capable of correcting image flaws of a regenerated image due to scratches on a lens, defective pixels of an imaging device and furthermore dust sticking to the surfaces of the lens and the imaging device, an image data compressing apparatus using the image correcting apparatus, and an imaging apparatus fitted with the image correcting apparatus and the imaging data compressing apparatus.
In order to accomplish the above-described object, the present invention provides with an image correcting apparatus applied to a compression circuit for processing the compression of image data by subjecting the image data inputted on a block basis to orthogonal transformation, quantizing the image data according to a quantization table and subjecting the image data to variable-length encoding according to an encoding table, the image correcting apparatus comprising:
a switching circuit for switching a first quantization table for quantizing image data in a block where the image flaw exists and a second quantization table for quantizing image data in a block where the image flaw does not exist on a block basis according to flaw position information for indicating a position where the image flaw is located.
Preferably, an image correcting apparatus further comprises a flaw detecting circuit for comparing each coefficient after orthogonal transformation of image data of a single image with each reference coefficient after orthogonal transformation in order to detect whether or not the image flaw exists in the block and a data generating circuit for generating the first quantization table corresponding to the image flaw existing in the block detected by the flaw detecting circuit.
Preferably, the flaw detecting circuit also detects the flaw or block position information about the image flaw existing in the block detected.
Preferably, the data generating circuit also generates the flaw or block position information about the image flaw existing in the block detected by the flaw detecting circuit.
And also the present invention provides with an image data compressing apparatus comprising:
a compression circuit for processing the compression of image data, wherein the compression circuit comprises orthogonal transformation means for subjecting each image data inputted on a block basis to orthogonal transformation, quantizing means for quantizing the image data subjected to orthogonal transformation by the orthogonal transformation means according to quantization tables and an encoding circuit for subjecting the image data quantized by the quantizing means to variable-length encoding according to an encoding table and
an image correcting apparatus comprising a switching circuit for switching a first quantization table for quantizing image data in a block where the image flaw exists and a second quantization table for quantizing image data in a block where the image flaw does not exist on a block basis according to flaw or block position information for indicating a position where the image flaw is located, the quantization tables being used in the quantizing means.
Preferably, the flaw or block position information is held in flaw-position-information holding mean
Kawasaki Steel Corporation
Oliff & Berridg,e PLC
Tran Phuoc
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