JPH04104656A - Picture reader - Google Patents

Abstract

PURPOSE:To suppress moire by providing a processing circuit generating the data of picture element after reduction through averaging data of all picture elements before reduction corresponding to the picture element after reduction to the reader. CONSTITUTION:When a picture element shown in a caption A corresponds to a picture element to be read completely, the output of a CCD 1 is a 100% output, while outputs of codes B, C, D are respectively 75, 50 or 25% outputs. However, data of 4 picture elements are averaged to be one picture element as consecutive four picture elements, since all the picture elements shown in codes A-M are concerned picture elements, then the output is 25%. Since 75% of picture elements in codes N-Q correspond to CCDs 14-17, the output is 19%. Although this is a kind of moire, since the difference (amplitude) is as small as 6%, the moire is almost unremarkable. Thus, generation of moire is almost suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to an image reading device suitable for use in a handy scanner.

[Conventional technology]

By manually scanning a document with a handy scanner, you can obtain a reduced image of the document. Conventionally, this reduced image has been generated by thinning out pixel data at a rate corresponding to the reduction rate.

Alternatively, the read pixel data is averaged through a low-pass filter corresponding to the dot density of the document, and then reduced.

[Problem to be solved by the invention]

However, the above method of simply thinning out data is
Since pixels with a density of 00% and pixels with a density of 0% appear periodically, there is a problem in that moiré, a pattern that does not exist in originals, occurs.

Further, the method of processing using a low-pass filter has the problem that the processing becomes complicated and the processing circuit becomes expensive and large. Therefore, it has been difficult to apply it to a handy scanner. In addition, the image data output from the handy scanner can be received by, for example, a personal computer, etc.
If you try to process it on a personal computer, etc., even if you reduce the image, all the data before reduction must be transferred from the handy scanner to the personal computer (handheld scanners cannot process it).
This has the problem of slowing down the processing speed.

As a result, processing becomes difficult for a personal computer with a small memory capacity.

The present invention has been made in view of these circumstances, and it is an object of the present invention to provide a device that is small, inexpensive, and suppresses the occurrence of moiré.

[Means to solve the problem]

The image reading device according to claim 1 includes: a line sensor that receives light from the original and reads the original; an optical system that forms an image of the original on the line sensor; and a relative position between the reading position of the line sensor and the original. an encoder that detects the amount of movement;
The image reading device according to claim 2, further comprising a processing circuit that averages data of all pixels before reduction corresponding to the pixel after reduction to generate data of the pixel after reduction. a line sensor that receives light from the line sensor and reads the original, an optical system that forms an image of the original on the line sensor, and an encoder that detects the amount of relative movement between the reading position of the line sensor and the original;
The apparatus includes a processing circuit that extracts a predetermined line from a plurality of lines before reduction, averages data of a plurality of pixels of the extracted line, and generates pixel data after reduction.

[Effect]

In the image reading device according to the first aspect, pixel data after reduction is generated by averaging data of all pixels before reduction corresponding to, for example, one pixel after reduction. Occurrence can be prevented.

Further, in the image reading device according to claim 2, a predetermined line is extracted from a plurality of lines before reduction corresponding to, for example, one line after reduction, and a predetermined line is extracted from a plurality of lines before reduction corresponding to one line after reduction, and one pixel of the extracted line after reduction is extracted. Since the data for one pixel after reduction is generated by averaging the data of a plurality of pixels, the occurrence of moiré can be suppressed with IJ[, which has a simple and inexpensive configuration.

〔Example〕

Next, an embodiment of the image reading device of the present invention will be described.

FIG. 2 shows the configuration of an embodiment of a handy scanner to which the image reading device of the present invention is applied.

Each component is arranged inside a space surrounded by an upper case 1 and a lower case 2. Rollers 3 and 4 are rotatably supported by the lower case 2. These rollers 3 and 4 are connected to the original 14.
When the main body is moved upward or downward by pressing upward, the rollers 3 and 4 rotate. The rotation of roller 3 is controlled by gears 5 to 9.
The rotation is transmitted to the encoder 11, and the encoder 11 detects the relative movement amount between the document 14 and the main body (finally, a line sensor 17, which will be described later) from this rotation.

When the main body is manually scanned with respect to the original 14, the light emitted from the LED 12 is transmitted to the reading section 1 made of a transparent member.
3 onto the original 14. The light reflected on the original 14 is incident on the mirror 15 via the reading section 13,
The reflected light enters a line sensor 17 such as a CCD via a lens 16. In this way, the LED
12, a mirror 15, a lens 16, and the like, an image on the original 14 is formed on the line sensor 17.

The output of the line sensor 17 is processed by a processing circuit arranged on the board 19 (the details of which will be described later with reference to FIG. 1), and then sent to a printer (not shown) via a cable 1o.
It is output to a display device, etc.

Note that a window 18 made of a translucent material is provided above the reading section 13 so that the scanning position can be confirmed.

FIG. 1 shows the configuration of one embodiment of a processing circuit built into the main body.

In this embodiment, a processing circuit 41 is composed of latch circuits 31 to 34 of A/D converter 30.4 stages, adder circuits 35, 36, 37, select circuits 38, 39, and memory 40.

Next, the operation will be explained with reference to the timing chart of FIG.

The video signal output from the line sensor 17 is input to an A/D converter 30 and A/D converted.

The data output from the A/D converter 30 is temporarily written into the memory 40. The data read from the memory 40 (FIG. 3(a)) is sequentially supplied to the latch circuits 31 to 34 in synchronization with the clock (FIG. 3(b)) and is latched. Due to this.

Data delayed by one clock is obtained from each of the latch circuits 31 to 34.

That is, pixel data ① and 2゛ are obtained from the memory 40.

Assuming that ``■'', .
, third pixel data (2) is output from the latch circuit 32, and fourth pixel data (2) is output from the latch circuit 31, respectively.

The adder circuit 35 outputs the latch circuit 33 (pixel data ■)
and the output of the latch circuit 34 (pixel data ■) are added and output. The adder circuit 36 adds the output of the latch circuit 31 (pixel data ■) and the output of the latch circuit 32 (pixel data ■) and outputs the sum.

Since each pixel data has 6 bits, the latch circuits 31 to 34 have a 6-bit configuration.

The outputs of adder circuits 35 and 36 include carry-over pits, so they are 7 bits. The adder circuit 37 adds the 7-bit output (■+■) of the adder circuit 35 and the 7-bit output (■+■) of the adder circuit 36, and adds 1 to the added value by selecting the upper 6 bits. /4 is multiplied and supplied to terminal A of the select circuit 39. That is, the data supplied to this terminal A (Fig. 3 (C)) is the average value of the data of 4 pixels (■ to α) ((■+C! + 3++■)/
The data corresponds to 4).

On the other hand, terminal B of the select circuit 39 is connected to the upper 6 bits of the output of the adder circuit 36, that is, the output of the adder circuit 36 is connected to 1/1.
The data multiplied by 2 (FIG. 3(d)) is supplied. This data corresponds to the average value ((■x■)/2) of two pixels (■ and ■).

In addition, the select circuit 38 alternately selects either the output of the latch circuit 31 (pixel data ■) or the data obtained by multiplying the output of the adder circuit 36 by 1/2 ((■+■)/2). Select (Figure 3(e)).

Of these, the data output every 4 clocks ((■1q+
) /2. (@+■)/2, etc.) are removed by a subsequent circuit (not shown). Therefore, 3 pixels
Data to be compressed to /4 is supplied to terminal C of the select circuit 39.

The output (■) of the latch circuit 31 (FIG. 3(f)) is directly input to the terminal of the select circuit 39.

The select circuit 39 selects and outputs one of the inputs from the terminals A to Terminal A, as shown in the following table, according to the logic of the signals input to the terminals Sl and S2.

When the front terminal A is selected, the output of the select circuit 39 is 4.
Updated every clock. Therefore, data for compressing the image to 1/4 is obtained.

Furthermore, when terminal B is selected, data is updated every two clocks, so data for compression to 1/2 can be obtained.

When terminal C is selected, data for compression to 3/4 is obtained.

When the terminal is selected, the data is updated every clock, so the data is used to obtain a same size image.

Note that the above processing is performed on the extracted pixel data of a predetermined line, but when compressing an image, the lines are thinned out according to the compression rate. For example, when compressing an image to 1/16, a predetermined line is extracted at a rate of one out of four, and three out of the remaining four lines are thinned out. Then, the four pixels of the extracted line are averaged to form one pixel. Similarly, when compressing an image to 1/4, a predetermined line is extracted at a rate of one out of every two lines, and one pixel is generated by averaging two pixels of the extracted lines. 9
When compressing to /16, predetermined lines are extracted at a rate of 3 out of 4 lines, and data of 3 pixels is generated from 4 pixels. If compression is not performed (same size), all lines are extracted and each pixel is not averaged. Such line extraction processing is executed by controlling reading from the memory 40.

Next, referring to FIG. 4, the operation of the above embodiment will be explained.
This will be further explained while comparing with the conventional case.

Figure 4 shows an original with a density of 25% (that is, 25% of one pixel area is black) and a halftone screen with 133 lines per inch tilted at 45 degrees, at 400DP.
Read with I (dot per inch) scanner, 1/
4 (that is, 100 DP) is shown.

When a halftone screen with 133 lines is tilted at 45 degrees, 94.
0 (=133/2”) DPI halftone dot.

This point is shown in FIG. 4(b). On the other hand, thinning out 3 pixels from 4 pixels as in the case of the conventional example means
Out of the 0DPI CCD, one out of every four pixels is extracted and 10
It means to use it as 0DPI. This is illustrated in FIG. 4(c).

Now, the CCD for one pixel shown by the number in Fig. 4(c)
Assuming that the pixels indicated by the symbol A in Fig. 4(b) completely correspond to each other (completely (100%) overlap in the vertical direction), the output of the CCD numbered 1 is 100%. output(
The fA degree is 25%) (Fig. 4(a)). On the other hand, since about 75% of the pixels of code B correspond to number 20CCD, the output thereof is also 75% (FIG. 4(a)). Similarly, since only about 50% or 25% of pixels with codes C and D correspond to CCDs with numbers 3 and 4, their outputs are also 5% or 25%.
The output is (Fig. 4(a)). Since the CCD numbered 5 and the pixel numbered E do not correspond, their output is 0% (FIG. 4(a)).

In this way, the positional relationship (correspondence) between the CCD and pixels is
Since it gradually shifts, when thinning processing is performed as in the conventional example, outputs of 100% and 0% appear alternately and periodically. Since the density of these pixels should originally be a constant value of 25%, this results in moiré.

On the other hand, in the present invention, for example, there are four strokes.

Since the average of the elementary data is one pixel, this can be expressed schematically as shown in Fig. 4(d), CC
D can be expressed as four consecutive pixels. In this way, all of the pixels indicated by numbers A to M in FIG. 4(b) correspond to the CCDs indicated by numbers 1 to 13 in FIG. 4(d), so the output is 25% (because the CCD has four times the area of the pixel) (FIG. 4(e)). In contrast, C shown with numbers 14 to 17
Since only 75% of the pixels indicated by symbols N to Q correspond to CD, the output is 19% (FIG. 4(e)). In this case as well, the output changes periodically between 25% and ]9%, which is also a type of moiré, but the difference (amplitude) is as small as 6%, so it is hardly noticeable.

In the above description, a predetermined number of lines are extracted from a plurality of lines according to the reduction ratio, and the pixels of the extracted lines are averaged, but data can also be averaged in the vertical direction.

For example, when compressing an image to 1/16, 4 lines of data are stored in the memory 40, 4 pixel data are extracted from each line, and a total of 16 pixel data are averaged and 1 ( By doing this, it is possible to almost completely suppress the occurrence of moiré.

However, as described above, moire can be sufficiently suppressed by averaging data in each line direction but thinning lines in the vertical direction. This is mainly due to the following reasons.

(1) Since averaging processing is performed in the horizontal direction,
Moiré is reduced.

(2) When detecting the relative movement amount between the document and the handy scanner, since rotation is transmitted from the roller 3 to the encoder 11 via the gears 5 to 9, there may be slippage between these and pulses of the rotary encoder 11. Due to the timing of occurrence, etc., the reading cycle becomes irregular compared to the line (horizontal) direction.

As a result, moire also becomes irregular and less noticeable.

〔Effect of the invention〕

As described above, according to the image reading device according to the first aspect, pixel data after reduction is generated by averaging a plurality of pixel data before reduction in both the line direction and the vertical direction. Therefore, it is possible to prevent the occurrence of moiré with a simple and inexpensive device.

According to the image reading device according to the second aspect, a predetermined line is extracted from a plurality of lines, and the pixel data after reduction is generated by averaging the plurality of pixel data of the extracted lines. , it is possible to suppress the occurrence of moiré with a simple and inexpensive device.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of a processing circuit of an image reading device according to the present invention, and FIG. (b) is a side sectional view and a plan sectional view showing the configuration of an embodiment of the image reading device of the present invention, FIG. 3 is a timing chart explaining the operation of the embodiment of FIG. 1, and FIG. It is a diagram explaining the occurrence. 3.4...Roller, 5 to 9・Gear, 11・Rotary encoder, 12・LED, 13・Reading section, 14・
・Original, 15 Mirror, 16 Lens, 17 Line sensor, 19 Board, 30 A/D converter, 4o
・Memory, 31 to 34...Latch circuit, 35 to 37
...Addition circuit, 38.39...Select circuit, 41.
processing circuit.

Claims (2)

[Claims] (1) A line sensor that receives light from a document and reads the document; an optical system that forms an image of the document on the line sensor; and a relative movement between the reading position of the line sensor and the document. An image reading device comprising: an encoder that detects the amount; and a processing circuit that averages data of all pixels before reduction corresponding to the pixel after reduction to generate data of the pixel after reduction. (2) A line sensor that receives light from a document and reads the document; an optical system that forms an image of the document on the line sensor; and a relative movement between the reading position of the line sensor and the document. An image reading device comprising: an encoder that detects the amount; and a processing circuit that extracts a predetermined line from a plurality of lines before reduction and averages the data of a plurality of pixels of the extracted line to generate pixel data after reduction.