JP2003046716A - Image processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a processing speed in matching with to the resolution. SOLUTION: The image processor has a sensor which is composed of an arrangement of several pixels and an image processing part which controls the change in period and duty of clock pulses for reading out signals from the sensor, in matching with the change in the resolution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus for picking up a subject image and processing the picked-up signal.

[0002]

2. Description of the Related Art In a line sensor in which a plurality of pixels are arranged in one line in the main scanning direction, the maximum cycle of image signal output is determined, and a normal image signal cannot be obtained even if a clock exceeding it is given. .

That is, the reading cycle of one line is (1
It could not be made faster than (pixel cycle) × (total number of pixels of line sensor).

When the resolution of the required image data is lower than the resolution of the line sensor, the image signal output of all the pixels of the line sensor is digitally processed and the resolution is used.

[0005]

For example, when the maximum resolution of the line sensor is 600 dpi, the clock pulse for driving the line sensor is generated regardless of whether the required resolution is 600 dpi or 300 dpi. The timing was the same, and therefore, the read cycle of one line, that is, the read speed was the same at 600 dpi and 300 dpi.

Therefore, even if the resolution is lowered, the reading speed cannot be increased.

An object of the present invention is to increase the reading speed when the required resolution of image data is low.

[0008]

In order to achieve the above object, a sensor unit in which a plurality of pixels are arranged, and a cycle and a duty of a clock pulse for reading a signal from the sensor unit according to a change in resolution are set. There is provided an image processing device, comprising: an image processing unit that controls to change.

[0009]

1 is an overall view of an image processing apparatus according to an embodiment of the present invention. The image processing apparatus according to the present embodiment has a resolution changing function.

An image reading unit 101 includes a line sensor in which a plurality of pixels are arranged in one line in the main scanning direction for picking up an image of a subject such as a document, and an LED as a light source. The LED is turned on by the LEDON signal to illuminate the document. The light applied to the document is reflected and reaches the sensor through an optical system (not shown). The line sensor outputs an electric signal according to the input light amount as an image signal VD.

Reference numeral 102 denotes an AD converter which converts the image signal VD which is an analog signal into a digital image signal DD at the timing of the sampling pulse SP. DD is 8b
It is a signal of it and is input to the image processing unit 103.

The image processing unit 103 performs appropriate image processing (for example, shading correction) on the input digital image signal and outputs it as image data. The image processing unit 103 also generates a timing signal necessary for the image reading unit. Also, control is performed according to the change in resolution.

CLK is a timing of outputting each pixel of the line sensor, and is a clock pulse for driving the line sensor to output the image signal VD from the line sensor, and SH is a read cycle of each line of the line sensor. Is a timing signal for determining.

SP is a sampling timing signal of the AD converter as described above.

LEDON is a signal synchronized with SH,
This turns on the LED of the line sensor.

Here, the above CLK, SH, and SP are changed according to the change of the resolution.

The operation according to the resolution will be specifically described below.

FIG. 2 is a diagram showing the timing of each line, FIG. 3 is a diagram showing the timing of each pixel in the case of the first resolution, and FIG. 4 is 1/1 of the first resolution. Two
FIG. 6 is a diagram showing timing for each pixel in the case of the second resolution of FIG.

As shown in FIG. 2, SH is a line synchronization signal, and this signal causes the output of the image signal VD for each line to be output from the leading pixel.

The SH cycle is at least (CLK cycle x 1
The number of pixels on the line) / 2 is required. If it is longer than that, it may be set longer.

LEDON is normally input in synchronization with SH. The LED lights up only during the LED ON period. Therefore, if the ON time of the LED is long, the amount of reflected light input to the sensor increases. Usually, the LED lighting time is the same for each line.

As shown in FIGS. 3 and 4, the image signal VD is output by one pixel every half cycle of CLK. Since the level of the image signal VD from the line sensor is reset and output for each pixel, the level is stable only after a sufficient time has elapsed from the falling or rising of the CLK signal.

For this purpose, the line sensor is set to have a minimum pulse width CLKV of CLK with which an effective image signal can be obtained. Further, the minimum pulse width CLKS of CLK required for the operation of the line sensor is also defined (CLKV> CL
KS).

The image processing unit, as shown in FIGS.
The sampling pulse SP is given to the AD converter for each pixel according to the resolution at a timing when D is stable. As a result, the AD converter outputs the digital image signal DD.

First, the processing of the image processing unit at the first resolution will be described.

In the present embodiment, the resolution of the line sensor is 600 dpi, the number of pixels in one line is 1000, and CLK
V is 400 ns.

Therefore, when the required resolution of the read image data is 600 dpi, the cycle of CLK = CL
If KV × 2 or more and a CLK having a positive pulse width and a negative pulse width are the same as shown in FIG. 3, a desired image signal can be obtained. At this time, the SH cycle is at least 40
0 ns × 1000 requires 400 μs or more.

In the case of the first resolution of this embodiment, C
LK cycle = 1000 ns (CLKV = 500 ns), S
H period = 500 μs, and SP is 1
The image processing unit controls so that it is output for each pixel.

Next, the processing of the image processing unit at the second resolution will be described.

In the present embodiment, the resolution is 300 dpi.
Is.

In the prior art, a 600 dpi digital image signal obtained by operating at the timing shown in FIG. 3 is subjected to appropriate processing in an image processing section and converted into 300 dpi to obtain 300 dpi image data. .

In this case, the SH cycle is 600 dp as described above.
Like i, it remains 500 μs.

In this embodiment, the image reading section is operated at the timing shown in FIG.

As shown in FIG. 4, the duty of CLK is changed so that the negative pulse width is shorter than the positive pulse width (the positive pulse width is CLKV and the negative pulse width is CLKS.
And).

In this case, CLKV is 400n as described above.
s, CLKS is 100 μs, and VD is as shown in FIG. CLK is a negative pulse period (, ...
.), The image signal VD is output, but the signal does not reach a stable level because it is not sufficient time.

At this time, the sampling pulse SP is shown in FIG.
As shown in FIG. In other words, the output of the AD converter outputs only the image signal of the odd pixel,
As a result, an image signal obtained by thinning out the image signal of the sensor output pixel by pixel, that is, an image signal equivalent to 300 dpi is obtained.

In this case, since the image signal output of even-numbered pixels is not used, there is no problem even if the output is not stable. If the pulse width at this time is CLKS or more, there is no problem in the operation of the line sensor.

The required SH period is 500 ns ×
Since (1000/2) = 250 μs, SH is set to 250
If the time is shortened to μs, the reading time will be shortened.

In the case of the second resolution of this embodiment, C
LK cycle = 500 ns (CLKV = 400 ns, CLK
(S = 100 ns), SH cycle = 250 μs, and the image processing unit controls so that SP is thinned out for each pixel and output.

Referring to FIG. 5, at 600 dpi and 300 d
The timing for each line at pi is shown.

As can be seen from FIG. 5, in the case of 300 dpi, 1 / should be obtained when the SH timing is 600 dpi.
2, that is, the time taken to read an image signal of one line from the line sensor is 1/2.

In the case of 300 dpi, the absolute value of the pulse width of LEDON is set to be the same even when SH is shortened. As a result, the same level of image signal can be obtained even if the reading speed changes due to the different resolution.

To achieve the above points, 300 dpi
It is necessary to design in advance so that the width of the LEDON signal falls within the SH period of time.

In the present embodiment, 600 dpi
The CLK cycle of is set to 500 ns because the image signal of one pixel at 300 dpi and the image signal of one pixel at 600 dpi are output at the same timing (that is, 1 every 500 ns.
This is because the system configuration becomes easier when the pixel image signal is output to the image processing unit.

However, the CLK cycle at 600 dpi is 8
If it can be set to 00 ns, the reading speed at 600 dpi can be slightly increased.

As described above, the cycle and duty of the clock pulse applied to the line sensor are changed according to the required resolution of the image signal, the timing of the sampling pulse applied to the AD converter is changed, and the cycle of the line synchronization signal is changed. By shortening, the reading time according to the resolution can be achieved, and the output time from the line sensor at the time of low resolution can be shortened.

[0047]

According to the present invention, a processing speed corresponding to the resolution can be achieved.

[Brief description of drawings]

FIG. 1 is a diagram showing an image processing apparatus according to an embodiment.

FIG. 2 is a diagram showing a timing of reading an image signal according to the present embodiment.

FIG. 3 is a diagram showing a timing of reading an image signal according to the present embodiment.

FIG. 4 is a diagram showing a timing of reading an image signal according to the present embodiment.

FIG. 5 is a diagram showing a timing of reading an image signal according to the present embodiment.

[Explanation of symbols]

101 image reading unit 102 AD converter 103 image processing unit

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 5/335 H04N 1/04 103Z F term (reference) 5B047 BB02 BC11 CA06 CA19 CB10 CB17 DB01 5C024 AX03 CX68 CX69 EX01 HX02 HX23 JX30 5C051 DA03 DB01 DB08 DB29 DC03 DC05 DE03 DE15 DE29 EA03 5C072 AA01 BA03 CA05 CA12 EA04 FB08 UA06 UA09

Claims (4)

[Claims] 1. A sensor unit in which a plurality of pixels are arranged, and an image processing unit which controls so as to change the cycle and duty of a clock pulse for reading a signal from the sensor unit in response to a change in resolution. An image processing apparatus having. 2. The sensor unit according to claim 1, wherein the plurality of pixels are arranged in one line in the main scanning direction, and the image processing unit reads out a pixel signal for each line according to the change in the resolution. An image processing apparatus characterized by changing a cycle. 3. The AD converter according to claim 1, further comprising an AD converter that converts a signal from the sensor unit into a digital signal, and the image processing unit has the AD unit according to a resolution.
An image processing apparatus characterized by changing a sampling timing of a converter. 4. The image processing unit according to claim 1, further comprising a light source that illuminates a subject.
An image processing apparatus, characterized in that the light source is controlled so that the irradiation time is substantially the same regardless of the change in resolution.