JP2586498B2 - MTF correction device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an MTF correction device, and more particularly to an MTF correction device capable of performing MTF correction at high speed.

(Prior Art) FIG. 2 is a schematic longitudinal sectional view of an image reading apparatus.

In FIG. 2, a document (not shown) placed on a platen glass 1 is illuminated by an illuminating light source 5, and its reflected light is reflected by a reflecting mirror 2 and then by a lens 3 by a CCD line sensor. 4 is formed.

The platen glass 1 or the reflecting mirror 2 and the light source 5 for illumination move in the direction perpendicular to the line direction of the CCD line sensor 4, whereby the image information recorded on the surface of the original is read line by line.

In such an image reading apparatus, in order to prevent deterioration in image quality due to deterioration of the optical system such as the lens 3, the illumination light source 5 or the like, or the CCD liner 4 or the like,
Each of the read image data is subjected to MTF correction.

MTF correction is performed by 3 × 3 with the image data of interest in the center.
Weight each of the image data matrices of
This is performed by adding.

That is, when performing MTF correction on the image data Dx, y of interest, a 3 × 3 matrix as shown in FIG. 3 is selected, and the image data of the matrix is used to calculate the first equation. Should be done.

Ex, y = P1 × Dx, y + P2 × (Dx-1, y + Dx + 1, y) + P3 × (Dx, y-1 + Dx, y + 1) + P4 × (Dx-1, y-1 + Dx + 1, y-1 + Dx-y, y + 1 + Dx + 1 , y + 1) (1) where Ex, y is data after MTF correction, and P1, P2, P3, and P4 are weighting coefficients. Further, in the following description, the product of the image data or the sum of the image data and the weighting coefficient, that is, each term P1 × Dx, y, P2 × (Dx
−1, y + Dx + 1, y),... Are referred to as weighted operation terms. That is, the image data after the MTF correction is represented by the sum of the four types of weighted operation terms.

In the conventional MTF correction device, when image data is read, an operation represented by the first expression is performed on each image data.

Such an MTF correction device is disclosed, for example, in JP-B-61-12590.
No., published in Japanese Unexamined Patent Publication No.

(Problems to be Solved by the Invention) The above-described conventional technology has the following problems.

That is, as described above, in the conventional MTF correction device, every time the image data is read, the calculation as shown in the first equation is performed for each image data. It was difficult to do.

The present invention has been made to solve the above problems.

(Means and Actions for Solving the Problems) In order to solve the above problems, the present invention records a plurality of weighted operation terms in a storage device in advance, and reads the weighted operation terms during MTF correction. It is characterized in that MTF correction is performed by reading out predetermined weighted calculation terms from the storage device based on the actual image data and adding them.

Thereby, at the time of MTF correction, there is no need to multiply the image data or the sum of the image data and the weighting coefficient to obtain the weighted operation term, and it is sufficient to simply add the read weighted operation terms. Therefore, it is possible to produce an operational effect that the MTF correction can be performed in a short time.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

 FIG. 1 is a block diagram of one embodiment of the present invention.

In FIG. 1, image data (MT
The image data before F correction is input to the gate 11 line by line.

Symbols 12 and 13 are gates, symbols 14 and 15 are latches, symbols 16 and 17
Is a line memory, wherein the gate 12 is connected to the gate 11 and the gate 13 is connected to the latch 14.

The gate 12, the gate 13, the line memory 16, and the line memory 17 are controlled by a write signal (WR) output from a timing generation circuit (not shown). Line image data (see FIG. 3) is stored, and n-
The image data of the n-th line read after the first line is stored.

The latches 14 and 15 are controlled by a read signal (RD), respectively, and are synchronized with the output of the image data of the (n + 1) th line from the gate 11 in synchronization with the nth line and (n−1) th line. The image data of the line is sequentially output.

Reference numerals 21 to 19 are data latches. The data latch 21 to the data latch 23 are connected in series to the gate 11, and the image data of the (n + 1) th line output from the gate 11 is sequentially input to each of them.

The data latches 24 to 26 are connected in series to the latch 14, and the image data of the n-th line output from the latch 14 is sequentially input to each of them.

Similarly, data latch 27 to data latch 29
, And the image data of the (n-1) th line output from the latch 15 is sequentially input to each of them.

That is, the data latches 21 to 29 respectively store the image data Dx−1, y− shown in FIG.
1, Dx, y-1, Dx + 1, y-1, Dx-1, y, Dx, y, Dx + 1,
y, Dx−1, y + 1, Dx, y + 1, Dx + 1, y + 1 are input.

 Reference numerals 31 to 33 are first adders.

The first adder 31 is connected to the data latch 21, the data latch 23, the data latch 27, and the data latch 29, and outputs image data (ie, four corners of a 3 × 3 image data matrix) output from each latch. Data, more specifically, Dx-1, y-1, Dx + 1, y-1, Dx-1, y +
1, and Dx + 1, y + 1).

The first adder 32 is connected to the data latch 24 and the data latch 26, and outputs the image data (that is, the data at the center of the left and right of the 3 × 3 image data matrix, more specifically, Dx−1, y, and D
x + 1, y).

The first adder 33 is connected to the data latch 22 and the data latch 28, and outputs image data (that is, data in the upper and lower center of a 3 × 3 image data matrix, specifically, Dx, y-1, and
Dx, y + 1).

The ROM 41 previously stores a plurality of types of products of the sum of the data at the four corners of the 3 × 3 image data matrix and the weighting coefficient P4, using the sum as an address. The ROM 41
Are connected to the output line of the first adder 31.

In the ROM 42, the product of the sum of the left and right center data of the 3 × 3 image data matrix and the weighting coefficient P2 is stored in advance.
A plurality of types are stored using the sum as an address. The RO
The address input line of M42 is connected to the output line of the first adder 32.

The product of the sum of the data in the upper and lower center of the 3 × 3 image data matrix and the weighting coefficient P3 is stored in the ROM 43 in advance.
A plurality of types are stored using the sum as an address. The RO
The address input line of M43 is connected to the output line of the first adder 33.

The ROM 44 previously stores a plurality of types of central data of the 3 × 3 image data matrix, that is, a product of Dx, y and the weighting coefficient P1 using the data as an address. The address input line of the ROM 44 is connected to the data latch 2
Connected to 5 output lines.

When an address signal is input to each address input line, each of the ROMs 41 to 44 sends a product of image data or a sum of image data and a weighting coefficient, that is, a weighting operation term to the second adder 34. Output.

The second adder 34 adds the weighted operation terms output from the ROMs 41 to 44.

In one embodiment of the present invention having the above configuration, image data output from an image reading device (not shown)
The data is input to the gate 11 line by line.

As described above, the image data of the (n-1) th line shown in FIG. 3 is stored in the line memory 17, and the image data of the nth line is stored in the line memory 17.
Stored in 16.

When the image data of the (n + 1) th line is output, the image data of the (n) th and (n−1) th lines are output from the latches 14 and 15, respectively.
Image data is input to the data latches 21 to 29 in an arrangement as shown in FIG.

The data latches 21 to 29 receive the same clock signal (CL
When the shift is performed by K), the first adders 31 to 33 add the image data output from the predetermined data latch and output the result (sum) to the ROM 41 to the ROM 43 as described above. .

The ROM 41 to the ROM 43 use the signals output from the first adders 31 to 33 as addresses, and the ROM 44 uses the image data output from the data latch 25 as addresses, and apply the corresponding data (weighting operation items). ) To the second
Is output to the adder 34.

Then, the second adder 34 adds the respective data, and the result, that is, the image data Ex, y after MTF correction is added.
Is output to an image forming apparatus (not shown) or the like.

In the above description, the weighting coefficients are assumed to be the same for the image data at the upper and lower centers, the left and right centers, and the four corners of the image data matrix. In other words, the weighting coefficients are 3 × 3 Although the matrix is symmetrical with respect to the vertical direction and / or the horizontal direction, the present invention is not particularly limited thereto. Naturally, it may be set to be symmetric.

(Effects of the Invention) As is apparent from the above description, according to the present invention, a plurality of weighted operation terms are stored in a storage device in advance, and when MTF correction is performed, the data is used for MTF correction based on the data. The MTF-corrected image data is obtained by reading out the data and simply adding them, so that the following effects are achieved.

(1) At the time of MTF correction, it is not necessary to multiply the image data or the sum of the image data and the weighting coefficient to calculate the weighted operation term, so that the MTF correction can be performed at high speed.

(2) Since the weighted calculation terms for performing the MTF correction are stored in the storage device (ROM), the weighted calculation terms calculated with different weighting coefficients are stored in advance in a plurality of storage devices. I can put it.

Therefore, the weighting coefficient can be easily changed by exchanging the storage device. That is,
Even if the image reader changes over time, good MTF correction can be always performed simply by replacing the storage device.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a schematic longitudinal sectional view of an image reading apparatus, and FIG. 3 is a view showing a 3 × 3 image data matrix used for MTF correction. 11 to 13 gates, 14, 15 latches, 16, 17 line memories, 21 to 29 data latches, 31 to 33 first adder, 34 second adder, 41-44… ROM

Claims (2)

(57) [Claims] 1. An MTF correction apparatus for weighting a 3 × 3 image data matrix and performing MTF correction on image data at the center thereof, wherein the MTF correction device is arranged to form a 3 × 3 matrix, and And a first adder connected to a predetermined one of the data latches so as to obtain a sum of a data latch to which image data is input and image data used to calculate a weighted operation term. And a weighted operation term is stored in advance as an address using the sum of image data and image data used to calculate the weighted operation term, and the address input line is
Storage means connected to the first adder and an output line of a data latch at the center of the matrix; and a second adder for adding a weighted operation term output from the storage means. Characteristic MTF correction device. 2. The image processing method according to claim 1, wherein the weighting operation term is a product of image data at the center, top, bottom, left, right, and four corners of the image data matrix and a predetermined weighting coefficient. 2. The MTF correction device according to claim 1.