JPH07297997A - Source document reader - Google Patents

Abstract

PURPOSE:To speed up the scanning of a source document and to improve the color reproducibility of the source document. CONSTITUTION:This device is provided with a CCD image sensor 3 composed of many optoelectric transducers arranged on the image formation surface of an optical system imaging a source document plane, a red fluorescent lamp 7R, a green fluorescent lamp 7G and a blue fluorescent lamp 7B having each different wavelength area and irradiating the source document plane, and a lighting circuit 20 turning on each of these fluorescent lamps 7R, 7G and 7B in a prescribed order by prescribed time. Further, the device is provided with a control circuit 4 controlling the line sensor so that the scanning of the source document plane may be started later than the starting of the turning on of each light source by the prescribed time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document reading device such as a facsimile or a scanner, and more particularly to a document reading device for reading information on a document by separating it into color signals.

[0002]

2. Description of the Related Art Conventionally, document reading devices such as facsimiles and scanners include document reading devices such as so-called color facsimiles and color scanners, which read information on a document by separating it into color signals. For example, Japanese Patent Publication Sho 62-6210
In Japanese Patent Laid-Open Publication No. 1-58, as a plurality of light sources having different wavelength ranges, a red fluorescent lamp, a green fluorescent lamp, and a blue fluorescent lamp are lit in a predetermined order for a predetermined period of time to illuminate the original plane,
There is disclosed a document reading device which receives light from a line sensor such as an image sensor, divides information on the plane of a document into wavelengths of respective fluorescent lamps, and reads out as electrical signals arranged in time series.

[0003] In the document reading apparatus of the above configuration, as shown in FIG. 14, lights the light-up signal period FLONR holds the "H" level of the red fluorescent light, i.e., only the red fluorescent lamp time T _R, green The period during which the lighting signal FLONG of the fluorescent lamp holds the “H” level, that is, the period during which the green fluorescent lamp is turned on for the time T _{G and} the lighting signal FLONB of the blue fluorescent lamp holds the “H” level, that is, The blue fluorescent lamp is turned on for the time T _B. Then, while the red fluorescent lamp is lit, the image reading signal VO corresponding to the blue color due to the lighting of the blue fluorescent lamp that was lit immediately before is output. That is, the image reading signal VO of the reflected light from the fluorescent lamp that is lit immediately before the fluorescent lamp that is currently lit is output.

At this time, in order to prevent the color mixture due to the afterglow of each fluorescent lamp, the signal FLONG is changed to the signal FL by the control means.
When ONR changes from "H" level to "L" level, td
_{In order to reach} the "H" level with a delay of _r2 ,
For LONB, the signal FLONG changes from "H" level to "L".
As td _g2 hours later the "H" level when the level further signal FLONR is, td _b2 hours later the "H" level when the signal FLONB becomes "H" level to "L" level Is controlled. Incidentally, C
The scanning start pulse SH ′ of the CD image sensor is set to the “H” level at the same time that the lighting signal of each fluorescent lamp becomes the “H” level.

Therefore, the lighting cycle of the fluorescent lamp of the document reading apparatus is T _R + T _G + T _B + td _r2 + td _g2 + td
_b2 , and a STEP pulse is applied to the motor for driving the CCD image sensor in this cycle to drive the motor to determine the scanning speed of the document.

[0006]

By the way, generally, the scanning time is determined by the lighting period of the fluorescent lamp. In other words, if the lighting cycle of the fluorescent lamp is short, the scanning time will be short,
It is possible to reduce the reading time of the document. However, in the above document reading apparatus, the lighting cycle of the fluorescent lamp is T
_R + T _G + T _B + td _r2 + td _g2 + td _b2 , which is td _r2 + t from the lighting time T _R + T _G + T _{B of} the fluorescent lamp.
It is longer by d _g2 + td _b2 . Therefore, td _r2
By shortening by + td _g2 + td _b2, only the lighting time of the fluorescent lamp becomes the lighting cycle, and the scanning time of the document can be shortened. For example, T _R = T _G = T _B = 500 μse
c, td _r2 = td _g2 = td _b2 = 100 μsec, T _R + T _G + T _B + td _r2 + td _g2 + td _b2
The lighting cycle of the fluorescent lamp is 1.8 msec, and T _R + T _G
At + T _B , the lighting period of the fluorescent lamp is 1.5 msec, and the scanning speed of the document can be increased.

However, the lighting cycle of the fluorescent lamp is set to T _R +
When T _G + T _B , as shown in FIG. 10 which is an explanatory diagram of the present invention, color mixing of the afterglow of the fluorescent lamp and the fluorescent lamp to be turned on next is performed to reproduce the color image of the original vividly. There is a problem that you can not do it.

Further, in the conventional document reading apparatus, even if the fluorescent lamp has a sufficiently long lighting cycle and the data transfer amount per line is large, the fluorescent lamp is within the lighting cycle even in a personal computer having a low data reception speed. It is possible to receive data for one line.

However, due to the high sensitivity of the CCD image sensor and the advent of a bright lens, it is possible to realize an original reading device for scanning with a short lighting time of a fluorescent lamp.
As a result, the transfer speed on the data transfer side becomes faster,
Such an original reading device capable of high-speed scanning cannot cope with an ordinary personal computer or the like having a relatively slow receiving speed on the data receiving side.

For example, the lighting cycle of the fluorescent lamp T _R + T _G + T
_{When B} = 1.5 msec, the host computer of the data transfer destination has a maximum data amount / one line of 2550 × 3.
= 7650 bytes, for example, the receiving time is 4
If it is msec, the data read by the document reading device cannot be received. Therefore, the waiting time T
_WAIT = 2.5 msec is the lighting cycle of the fluorescent lamp T _R + T _G +
By adding T _B = 1.5 msec, the transfer time T
= 4 msec, the host computer can receive the data.

However, the transfer time of the document reading device T = 4
When msec is set, when the host computer side requests the transfer of the first 1275 pixels of the 2550 pixels of the original image, the data amount / line on the host computer side is half the maximum data amount / line, that is,
Since (1275 × 3) / (2550 × 3) = 1/2, the receiving time is 2 msec. However, since the transfer time T of the document reading device is set to 4 msec, the host computer transmits the data for 2 msec.
Although it can be received at, the data is transferred with a delay. This causes a problem that the efficiency of data transfer to the host computer is reduced.

The present invention has been made in view of the above problems, and an object of the present invention is to increase the speed and accuracy of scanning an original without causing color mixing, and thereby to improve the color of an original image. An object of the present invention is to provide a document reading apparatus capable of improving reproducibility and changing the data transfer time according to the receiving time on the data receiving side to transfer data efficiently.

[0013]

According to a first aspect of the present invention, there is provided a document reading apparatus which comprises a line consisting of an optical system for picking up an image of a plane of a document and a large number of photoelectric conversion elements arranged on an image plane of the optical system. The light source includes a sensor, a plurality of light sources each having a different wavelength range and irradiating the original plane, and a lighting means for turning on the light sources in a predetermined order for a predetermined time. It is characterized in that a control means for controlling the line sensor is provided so as to start after a predetermined time from the start of lighting.

A document reading apparatus according to a second aspect of the present invention is the document reading apparatus according to the first aspect, wherein the control means includes a line sensor so as to change the speed of the document scanning according to the amount of data per line of the document image. It is characterized by controlling.

According to a third aspect of the present invention, in the document reading apparatus according to the second aspect, the control means sets the speed of the original scanning regardless of the amount of data per line of the original image. .

[0016]

According to the structure of the first aspect, the control means controls the line sensor so that the scanning of the plane of the original is started after a predetermined time from the start of lighting of each light source. If the predetermined time is set as the time after which the afterglow of each light source disappears, color mixing due to the afterglow of each light source can be eliminated. This makes it possible to eliminate the delay time provided for avoiding color mixing, that is, the time set between the light emission times of the respective light sources, when the lighting of the light sources and the scanning of the original by the line sensor are simultaneously performed. Therefore, the lighting cycle of each light source is sufficient only for the lighting time of each light source. Therefore, it is possible to shorten the time for scanning the original by the line sensor and eliminate the color mixture of each light source.
It is possible to speed up the document scanning and improve the color reproducibility of the document.

According to the structure of the second aspect, the line sensor is controlled by the control means so as to change the speed of the document scanning according to the amount of data per line of the document image. When the data amount is small, the document scanning speed can be increased, and when the document scanning data amount is large, the document scanning speed can be decreased. As a result, even if the data receiving speed at the data receiving side such as the host computer that receives the data to be transferred is slow, it is possible to efficiently handle the data transfer.

According to the third aspect of the present invention, the control means sets the speed of document scanning regardless of the amount of data per line of the document image, so that the host computer can receive data at high speed. It is possible to always transfer data to the receiving side such as at a high speed and at a constant speed. As a result, the data can be efficiently transferred to the high speed host computer.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention is shown in FIGS.
The explanation is based on the following.

As shown in FIG. 2, a color scanner 1 as an original reading device according to the present embodiment includes, for example, a host computer 2 as an image processing device and a SCSI.
(Small Computer System Interface) interface or GPIB (General Purpose Interface Bus)
Information is communicably connected via a communication means such as an interface. The color scanner 1 decomposes the image information of the original into color signals and sends them to the host computer 2, and the host computer 2 recognizes the color and reads the mark on the original based on the image information from the color scanner 1. Image processing such as pattern recognition or character recognition pattern is performed.

As shown in FIG. 1, the color scanner 1 includes a CCD (Charge C) for solid-state scanning in which a plurality of solid-state photosensitive elements (light-receiving elements) are arranged in a predetermined direction (main scanning direction).
image sensor (line sensor) 3,
Further, a control circuit (control means) 4 for controlling the operation of the entire color scanner 1 including the CCD image sensor 3 is provided, and is connected to a host computer 2 as an image processing means so as to be capable of information communication. In this embodiment, the CCD
It is assumed that the image sensor 3 has 2550 solid-state photosensitive elements.

The control circuit 4, as shown in FIG.
A PU (Central Processing Unit) 4c, a FIFO memory 4a for storing data from the CCD image sensor 3
4b, a data selector 4d for selectively outputting data from the FIFO memories 4a and 4b, and an interface circuit for information communication with the host computer 2.

As shown in FIG. 3, the color scanner 1 includes an original placing table 5 made of a transparent glass plate for placing the original P, and a sub-scanning direction (below the original placing table 5 in the sub-scanning direction). The optical unit 6 is provided so as to be movable in the main scanning direction).

A white plate WB is provided near the sub-scanning start position of the optical unit 6, and the white plate WB is first read before the scanning of the original P starts. The white plate WB has a very bright white color and is brighter than the background of the document P that is generally used.

As shown in FIG. 4, the optical unit 6 irradiates a document with a red fluorescent lamp (hereinafter referred to as a red fluorescent lamp) 7 as a light source having a different wavelength range.
_R and green fluorescent lamp (hereinafter referred to as green fluorescent lamp) 7
_G and blue fluorescent lamp (hereinafter referred to as blue fluorescent lamp) 7
_B, and a plurality of mirrors 8 for guiding the reflected light from the document to the CCD image sensor 3 (first to sixth mirrors 8a
8f), a lens 9 for focusing the reflected light from the document, and the CCD image sensor 3.

The optical unit 6 is driven in the sub-scanning direction substantially orthogonal to the main scanning direction by the optical unit driving mechanism 10 (sub-scanning device) as the sub-scanning device shown in FIGS. The optical unit drive mechanism 10 is basically provided on a slide shaft 11 for guiding the optical unit 6 in the sub-scanning direction, a drive motor 12 such as a pulse motor, and an output shaft of the drive motor 12. The motor gear 13, a reduction gear 14 meshing with the motor gear 13, and the reduction gear 1 fixed to the reduction gear 1
4, a first pulley 15 that rotates at the same rotation speed, a second pulley 16 provided at a predetermined distance from the first pulley 15, and a winding between the first pulley 15 and the second pulley 16. The timing belt 17 is provided with a belt tension adjusting spring 18 attached to the second pulley 16, and a belt retainer 19 for fixing the optical unit 6 and the timing belt 17 together.

One end of the optical unit 6 is slidably attached to the slide shaft 11, and the optical unit drive mechanism 10 includes a drive motor 12
Is converted into a reciprocating motion of the timing belt 17 via the motor gear 13 and the reduction gear 14, and the optical unit 6 fixed to the timing belt 17 is conveyed along the slide shaft 11.

As shown in FIG. 1, the control circuit 4 sends a signal FLON to a lighting circuit (lighting means) 20 for driving the fluorescent lamp 7.
R, signal FLONG, and signal FLONB are output to control ON / OFF of each fluorescent lamp 7 _R , 7 _G , 7 _B. For example, when the signal FLONR is at the “H” level, the lighting circuit 20 lights the red fluorescent lamp 7 _R while the signal FLONR is turned on.
When the NR is at the “L” level, the lighting circuit 20 is the red fluorescent lamp 7
It is designed to turn off _R. Similarly, the signal FLO
The lighting circuit 20 controls turning on / off of the green fluorescent lamp 7 _G by NG, and the lighting circuit 20 controls turning on / off of the blue fluorescent lamp 7 _B by signal FLONB.

For example, as shown in FIG. 7, the red fluorescent lamp 7 _R is lit by a self-exciting high-voltage generating circuit provided in the lighting circuit 20. That is, this high-voltage generating circuit outputs to the secondary side output of TRANS when the signal FLONR is 5V.
A high voltage AC waveform (AC250V) of several tens of kHz is generated to turn on the red fluorescent lamp 7 _R. The green fluorescent lamp 7 _G and the blue fluorescent lamp 7 _B are each provided with a high voltage generating circuit.

Further, as shown in FIG. 1, the control circuit 4 outputs a signal FORWARD and a signal STEP to the motor drive circuit 21 which drives the drive motor 12 of the optical unit drive mechanism 10 to rotate the drive motor 12. To control. When the signal STEP switches from the "L" level to the "H" level while the signal FORWARD is at the "H" level, the motor drive circuit 21 causes the drive motor 1 to operate.
Rotate 2 by a fixed angle. As a result, the drive motor 12 advances the optical unit 6 by a fixed distance. On the other hand, when the signal STEP switches from the "L" level to the "H" level when the signal FORWARD is at the "L" level, the motor drive circuit 21 causes the drive motor 1 to operate.
Rotate 2 in reverse by a fixed angle. As a result, the drive motor 12 retracts the optical unit 6 by a certain distance. In this embodiment, the resolution of the scanning device is 300 dpi.
Therefore, the drive motor 12 drives the optical unit 6 at 1/300 inch per line, that is, about 1/12 mm.
Move one by one.

Further, the control circuit 4 outputs a start pulse SH for starting the main scanning and a scanning basic clock φ ₀ to the CCD image sensor 3.
The CCD image sensor 3 uses the start pulse SH
And solid-state scanning (main scanning) is performed based on the scanning basic clock φ ₀ .

The electric signal v _O corresponding to the original image output from the CCD image sensor 3 is inverted by the inverting section composed of the capacitor C ₁ , the resistors R ₁ and R ₂ and the operational amplifier 22, and then the capacitor C 1. _{After the} DC component is removed by ₂ , it is input to the buffer amplifier 23. On the input side of the buffer amplifier 23, there is provided a DC level clamp analog switch ASW composed of a MOS field effect transistor operated by the clamp pulse T _CLAMP output from the control circuit 4. The base level of the output signal VO (hereinafter referred to as the image reading signal VO) is clamped to the ground level.

The image read signal VO is an analog / digital converter (hereinafter referred to as an AD converter) 2
4 analog input terminal A _IN .

The AD converter 24 quantizes the image read signal VO input to the analog input terminal A _IN and converts it into a digital amount. AD of this AD converter 24
The conversion operation is performed based on the clock T _AD output from the control circuit 4.

Specifically, the AD converter 24 is
0V to D for analog input (image reading signal VO)
An 8-bit digital signal A is coded after quantizing between A _OUT , for example, to a quantization level of 255 steps.
D ₀ , AD ₁ , ... AD ₇ are output.

The digital signals AD ₀ , AD ₁ , ... A
D ₇ is input to the control circuit 4 as the binarized signals DI ₀ , DI ₁ , ... DI ₇ . This binary signal DI ₀ , D
I ₁ , ... DI ₇ are output to the host computer 2 via the interface circuit (FIG. 8) described above.

The exchange of signals between the host computer 2 and the control circuit 4 will be described below with reference to FIGS. 1, 11 and 12.

As shown in FIG. 12, the host computer 2 outputs the signal RDCLK to the control circuit 4 when the signal SRDY input from the control circuit 4 is at "H" level, and the control circuit 4 outputs the data SD. ₀ , SD ₁ , ... SD ₇
Is entered.

Further, the host computer 2 requests the control circuit 4 to output a signal HREQ and, for example, a command for designating a data amount per line or a command for designating a cycle T of one line. At this time, when the control circuit 4 receives the command data from the host computer 2, as shown in FIG.
Set CK to "H" level. When the host computer 2 confirms that the signal SACK is at the “H” level, it sets the signal HREQ to the “L” level and then outputs the signal SAC.
K is also set to "L" level.

The interface circuit provided in the control circuit 4 will be described with reference to FIG. 8. First, the binarized signals DI ₀ , DI ₁ , ... DI _{7 will be described.}
When the write pulse WA is at “H” level, data for one address is written in the storage area of the memory 4a, and when the read pulse RA is at “H” level, the data for one address from the storage area of the memory 4a is written. Is read. Also, 2
The digitized signals DI ₀ , DI ₁ , ... DI ₇ are set to 1 in the storage area of the memory 4b when the write pulse WB is at “H” level.
When the data for the address is written and the read pulse RB is at "H" level, the data for the one address is read from the storage area of the memory 4b. That is, the binarized signal DI ₀ ,
DI ₁ , ... DI ₇ are stored in the memory 4a as AI ₀ , AI ₁ ,
... stored as AI ₇ input data, AO ₀ , AO ₁ ,
... While being read as AO ₇ output data, memory 4
BI ₀ , BI ₁ , ... BI ₇ input data are stored in b and read as BO ₀ , BO ₁ , ... BO ₇ output data.

In the interface circuit, the data read from each of the memories 4a and 4b is SA ₀ , SA ₁ , ... SA ₇ input data, S ₇ in the data selector 4d.
B ₀ SB ₁ , ... SB ₇ Stored as input data, SD
₀ , SD ₁ , ... SD _{7 are} output to the host computer 2 and the CPU 4c as output data. At this time, the data selector 4d selects SA ₀ , SA ₁ , ... SA ₇ input data when the input selection signal SELA is at “H” level, and outputs it as SD ₀ , SD ₁ , ... SD ₇ output data. When the selection signal SELA is at "L" level,
SB ₀ , SB ₁ , ... SB ₇ Select the input data and press S
The data is output as D ₀ , SD ₁ , ... SD ₇ output data.

Further, a signal MA output from the CPU 4c
Is at the "H" level, the write pulse WA is set to the "H" level to enable writing of data to the memory 4a, and the read pulse RB is set to the "H" level.
Data can be read from the memory 4b.
On the other hand, when the signal MA output from the CPU 4c is at "L" level, the write pulse WB is set at "H" level to enable writing of data to the memory 4b, and
The read pulse RA is set to the “H” level to enable the reading of data from the memory 4a. Therefore,
The signal MA is "H", "L", "H", for each line.
Since it is output while being inverted to "L", the write pulse becomes the inverted signal of the clock T _AD and the read pulse becomes the signal RDCLK.

FIG. 9 shows waveforms of various signals in the document reading apparatus. The scanning operation of the document reading device
The following description will be given mainly with reference to FIGS. 9 and 1.

The control circuit 4 raises the start pulse SH from the "L" level to the "H" level in a cycle of 5 msec, for example, to start solid scanning as main scanning. As a result, the CCD image sensor 3 has the scanning basic clock φ.
Solid-state scanning is performed based on _0, and electric signals v _O corresponding to the original image are sequentially output. The signal v _O is inverted and the direct current component is removed, and then input to the buffer amplifier 23. The base level of the image reading signal VO output from the buffer amplifier 23 is the clamp pulse T _CLAMP.
Clamped to ground level based on.

During the main scanning, the image reading signal VO is A
It is input to the analog input terminal A _IN of the D converter 24. Further, the AD converter 24 outputs digital signals AD ₀ , AD ₁ , ... AD ₇ according to the image reading signal VO.

The control circuit 4 uses the digital signal A
Image information composed of D ₀ , AD ₁ , ... AD ₇ is sent to the host computer 2.

After the main scanning of one line by the CCD image sensor 3 is completed, the above operation is repeated thereafter.

The lighting operation of each fluorescent lamp will be described below with reference to the waveform chart shown in FIG.

In the document reading apparatus having the above-described structure, as shown in FIG. 10, the time when the red fluorescent lamp 7 _R starts to emit light is the signal F.
Td _r1 is longer than the time for switching to the “H” level of LONR
While the time is delayed, the time when the red fluorescent lamp 7 _R is turned off is signal F
It is designed to be delayed by td _r2 time from the time when the LONR “H” level is switched to the “L” level. This is because even if a signal from red fluorescent lamp 7 _R control circuit 4 to the lighting circuit 20 of FLONR is input, a slight time lag until turning on the red fluorescent lamp 7 _R by lighting circuit 20 is generated, also, the time off This is because there is afterglow of the red fluorescent lamp 7 _R.
In addition, in the green fluorescent lamp 7 _G and the blue fluorescent lamp 7 _B , td _g1 , td with respect to the signal FLONG as in the red fluorescent lamp 7 _R.
g2 time delay occurs, td _b1 with respect to signal FLONB,
There is a delay of td _b2 hours.

Therefore, the control circuit 4 controls the signal FLONR.
The signal FLONG, the signal FLONB, and the signal FLONB are sequentially set to "H" level, and in order to avoid color mixture due to afterglow of each fluorescent lamp, the start pulse SH to the CCD image sensor 3 is delayed by the above time shift. H "level. As a result, conventionally, as shown in FIG.
It is possible to avoid color mixing such as when the signal FLONR, the signal FLONG, and the signal FLONB are at the “H” level and the start pulse SH ′ to the CCD image sensor 3 is at the “H” level at the same time. So
The scanned original image can be reproduced in vivid colors.

Further, the delay time td which has been conventionally used is
_r1 , td _r2 , td _g1 , td _g2 , td _b1 , td _b2 are signals F
Since the "H" level of LONR, signal FLONG, and signal FLONB is absorbed during the time it is held,
The lighting cycle of the fluorescent lamp is T _R + T _G + T _B , and the lighting cycle can be shortened. As a result, there is no influence of afterglow and the scanning time for one line of the original can be shortened, so that it is possible to improve the color reproducibility of the original and to speed up the original scanning.

Data transfer between the document reading device and the host computer 2 will be described below with reference to the waveform chart of FIG.

The control circuit 4 controls the host computer 2 during the time T during which the signal SRDY is held at "H" level.
The image data read in is transferred.
The transfer time T is obtained by adding the lighting cycle T _RGB of each fluorescent lamp and the waiting time T _WAIT.
WAIT is changed according to the data transfer amount. That is, the control circuit 4, as shown in Table 1 below,
The waiting time T _WAIT is changed according to the amount of data / line and the transfer time T is changed.

[0054]

[Table 1]

That is, the maximum data amount / one line is 255
When 0 × 3 is set and the lighting cycle at this time is 5 msec, the transfer time T = x is calculated by the following formula.

(2047 × 3) / (2550 × 3) = x / 5 ∴ x is about 4 msec (1274 × 3) / (2550 × 3) = x / 5 ∴ x is about 4.5 msec (1023 × 3) / (2550 × 3) = x / 5 ∴x is about 2 msec (512 × 3) / (2550 × 3) = x / 5 ∴x is about 1 msec, but the maximum transfer time in the document reading apparatus of the present embodiment. 1.5m
Since it is sec, the transfer time x in this case is about 1.5 m
Let be sec.

If the data receiving speed of the host computer 2 on the data receiving side is slower than the setting in Table 1 above, the control circuit 4 specifies the transfer time T = 10 msec, for example, by the host computer 2, The reading device controls the CCD image sensor 3 so as to scan the document at this time.

Therefore, as described above, the transfer time can be changed according to the receiving time of the data receiving side, so that the data can be transferred efficiently.

Further, the control circuit 4 is adapted to set the document scanning speed regardless of the amount of data per line of the document image. For example, when the receiving host computer 2 has high speed and high performance, that is, when the data receiving time of the host computer 2 is very short, the control circuit 4 causes the receiving time of the data of the host computer 2 to be 1.5 msec. If (the time corresponding to the maximum transfer time of this document reading device), the transfer time of the document reading device is set to 1.5.
It is set to msec, and the CCD image sensor 3 is controlled so that the original is scanned and the data is transferred at the transfer time T = 1.5 msc. As a result, the document reading apparatus can scan the document at the maximum speed and can transfer and receive the data to the host computer 2 at a high speed regardless of the amount of data to be transferred at that time. Therefore, the document reading apparatus can sufficiently cope with the data transfer to the host computer 2 having a high data receiving speed.

[0060]

As described above, the document reading apparatus according to the present invention comprises the optical system for picking up an image of the plane of the document and a large number of photoelectric conversion elements arranged on the image plane of the optical system. Each of the line sensors, a plurality of light sources having different wavelength ranges and irradiating the original plane, and a lighting means for turning on the light sources in a predetermined order for a predetermined time, are provided for scanning the original plane. A control means for controlling the line sensor is provided so that the light source is started after a predetermined time from the start of lighting of each light source.

As a result, the time for scanning the original by the line sensor can be shortened and the color mixture of the respective light sources can be eliminated, so that the speed of the original scanning and the color reproducibility of the original can be improved. Play.

As described above, in the document reading apparatus of the second aspect of the present invention, the control means controls the line sensor so as to change the document scanning speed according to the amount of data per line of the document image. Is.

As a result, even if the data receiving speed at the data receiving side such as the host computer that receives the data to be transferred is slow, it is possible to efficiently transfer the data. .

As described above, the document reading apparatus according to the third aspect of the present invention is configured such that the control means sets the document scanning speed regardless of the amount of data per line of the document image.

As a result, it is possible to efficiently transfer the data to the host computer or the like on the receiving side having a high receiving speed.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention and is a block diagram showing a schematic configuration of a main part of a document reading apparatus.

FIG. 2 is a block diagram showing a schematic configuration of an image processing system using the document reading device.

FIG. 3 is a schematic vertical sectional view of the document reading device.

FIG. 4 is a schematic vertical sectional view showing a configuration of an optical unit of the document reading apparatus.

FIG. 5 is a schematic front view showing a configuration of an optical unit drive mechanism of the document reading apparatus.

FIG. 6 is a schematic plan view showing a configuration of a peripheral portion of a drive motor of the optical unit drive mechanism.

FIG. 7 is a schematic configuration diagram of a lighting circuit shown in FIG.

8 is a schematic configuration diagram of an interface circuit included in the control circuit shown in FIG.

FIG. 9 is a timing chart showing waveforms of various signals in the document reading apparatus.

FIG. 10 is a timing chart showing a waveform of a lighting signal of a fluorescent lamp and a start pulse of a CCD image sensor in the document reading apparatus.

FIG. 11 is a timing chart showing waveforms of signals transmitted and received between the control circuit and the host computer in the document reading apparatus.

FIG. 12 is a timing chart showing waveforms of signals transmitted and received between the control circuit and the host computer in the document reading apparatus.

FIG. 13 is a timing chart illustrating a data transfer time from the control circuit to the host computer in the document reading apparatus.

FIG. 14 is a timing chart showing waveforms of various signals in the conventional document reading apparatus.

[Explanation of symbols]

3 CCD image sensor (line sensor) 4 control circuit (control means) 7 _R red fluorescent light (light source) 7 _G green fluorescent light (light source) 7 _B blue fluorescent light (light source) 8 mirror (optical system) 9 lens (optical system) ) 20 Lighting circuit (lighting means)

Claims (3)

[Claims] 1. An optical system for picking up an image of a plane of an original, and a line sensor composed of a large number of photoelectric conversion elements arranged on an image plane of the optical system, each having a different wavelength range, A plurality of light sources for illuminating the plane of the original and a lighting means for lighting these light sources in a predetermined order for a predetermined time each are provided, and the scanning of the plane of the original is started by a predetermined time after the start of lighting of each light source. The document reading apparatus is provided with the control means for controlling the line sensor as described above. 2. The control means controls the line sensor so as to change the scanning speed of the document according to the amount of data per line of the document image.
The document reading device described. 3. The document reading apparatus according to claim 2, wherein the control means sets the document scanning speed regardless of the amount of data per line of the document image.