JPS63211867A - Image reader - Google Patents

Abstract

PURPOSE:To constitute an image reader of an excellent quality of synthesis by providing an address control means to control the read start address or the end address of a memory data based on a temperature detection signal. CONSTITUTION:The followings are provided: an illumination means to illuminate the surface of an original 1, plural photoelectric conversion elements 10 such as charge coupled device that scan the original 1 whose read area is divided in plural sections line after line along the main scanning direction and convert optical signals from the original 1 to electrical signals, a temperature detection means 21 such as a thermister to detect a temperature in the vicinity of the elements 10, a memory in whose prescribed address a read data from the elements 10 is stored, and an address control means to control the read start address or the end address of a memory data based on a temperature detection signal from the temperature detection means 21. As a result, the temperature compensation at the joint part between images can exactly be executed, and the reliability of the read of image can be improved.

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to an image reading device such as an image sensor, and particularly relates to an image reading device such as an image sensor, in which a reading area is divided into a plurality of parts along the main scanning direction, and a reading area corresponding to each divided reading area is divided. The present invention relates to an image reading device in which a plurality of photoelectric conversion elements are arranged in parallel for reading data.

(Prior art) Conventional image reading devices have a low pixel density (about 8 lines/■), and the document size to be read is, for example, A3 size: f, (29
7 mm), a charge-coupled device (hereinafter abbreviated as CCD) is used for reading the document.

), it was sufficient to use one with about 2600 pixels. Recently, there has also been an image reading device that uses a 5000 pixel CCD and has a pixel density of 16 lines/1ffn to read A3 size documents, but this too was able to read documents with one CCD.

However, if you try to read a larger A2 size or AO size document at a pixel density of 16 pages/field, 5
Even if a CCD with 000 pixels is used, the reading area must be divided into two or three CCDs for reading. By the way, in such an image reading device that can read large-sized originals, the area is shared between multiple CCDs to read the original image.

A new problem arises regarding image seams.

FIG. 1'il1 is a schematic configuration diagram of an image reading device that reads a document using a plurality of CCDs. As shown in the figure, a plurality of optical lenses 52 and a plurality of CCDs 53 are arranged in pairs along the main scanning direction of a document 51. The document surface is exposed in a slit shape by an illumination lamp (not shown), and the reflected light from the document surface is transmitted through each optical lens 52 and received by the corresponding CCD 53, so that the document image is optically divided line by line. is read. The data read by the CCD 53 is stored in a memory of a control section (not shown).

In an image reading device having such a configuration, for example, the optical lens 52. Variations in the mounting position of CCD53,
Alternatively, the image joint portion 54 may be displaced due to thermal expansion or contraction of the CC, D53 itself or the optical unit including it, which may prevent proper image reading.

Normally, when the CCD 53 or the optical unit 1 expands in a direction perpendicular to the optical axis, the joint portion 54 becomes double, and when it contracts, the joint portion 54 separates, resulting in data loss.

Furthermore, when creating one line of composite data based on the read data from each CCD, if all the read data is taken in and combined, the data quality deteriorates, especially at the joints. This is thought to be because the MTF of the optical lens that projects the image onto the CCD decreases toward the periphery, and because the aberration of the lens increases, making magnification errors and focus errors more likely to occur.

(Objective) It is an object of the present invention to solve the problems of the prior art and provide an image reading device with high reading reliability.

(Structure) For this reason, the present invention includes an illumination means for illuminating the document surface, a reading area divided into a plurality of parts along the main scanning direction, scanning the document line by line, and converting optical signals from the document surface into electrical signals. A plurality of photoelectric conversion elements such as CCDs, temperature detection means such as a thermistor, which detects the temperature near the photovoltaic conversion elements, and data read from the photoelectric conversion elements are sent to respective predetermined addresses. The present invention is characterized by comprising a memory for storing data, and an address control means for controlling a read start address or end address of memory data based on a temperature detection signal from the temperature detection means.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an image reading device according to an embodiment of the present invention, FIG. 2 is an explanatory diagram showing the arrangement of an optical lens and a CCD, and FIG. 3 is a front view showing a fixed state of the optical lens and CCD. , FIG. 4 is an overall control block diagram.

As shown in FIG. 1, when a document 1 to be read is inserted from the document table 2, the document entrance sensor 3 detects the leading edge, and the detection signal causes the document transport motor (
(not shown) is driven, the conveyance rollers 4.5 rotate, and the document 1 is conveyed to the document reading section /\, and the illumination lamp 6 is turned on.

When the leading edge of the original l is detected by the original registration sensor 7, a shading start signal is sent from a control unit (not shown), and a signal obtained by A/D (analog/digital) conversion of the light reflected from the original pressure plate 8 at this time is used for shading. R.A.
The signal is stored in M and is used when reading a document as a correction signal for uneven light intensity in the main scanning direction, sensitivity of each CCD, etc.

The document surface of the document 1 conveyed to the document reading section is exposed to light in a circular shape by the illumination lamp 6, and the optical impression made of the reflected light is reduced to about 1/9 by the optical lens 9.
For example, it is read by a CCD10 made of a solid-state image sensor.

This CGDIO is one in which 5,000 reading elements with a pitch of 7 μm are integrated [for example, Toshiba Corporation mTc106c
)5, and the reading density of original 1 is set to 16 lines/mTl1 on the original surface.

The document 1 from which information has been optically read line by line in this manner passes over the contact glass 11 and is discharged onto the tray 13 by the discharge rollers 12.

- This image reading device uses a CCD so that it can also read a relatively large document 1, for example, AO size.
A plurality of l0's (three in this embodiment) are used. Then, as shown in FIG. 2, 918 mm in the main scanning direction is divided into three parts, and three CCDs 10a, 10b, and 10c each have a length of 312 mm.
The CCDs 10 are mounted on one base member 14 (see FIG. 3) so that the overlap width between the CCDs 10 is 4 to 7 mm.

FIG. 3 is a diagram showing how the optical lens 9 and CCD 10 are attached. A printed circuit board 14 on which CGDIO and other electronic components are mounted is fixed to a mounting plate 19 via two supports 16 and a mounting bracket 17. On the other hand, the optical lens 9 is directly fixed to the mounting plate 19 by a lens holder at a position facing the CCD10. This mounting plate 19 further includes a mounting bracket 2.
0 to the base member 14. C
The magnification and focus are adjusted by adjusting the vertical movement of the optical lens 9 and the mounting plate 19 relative to 0DIO.

The base member 14 that ultimately fixes CGDIO is
It is made of cast aluminum from the viewpoint of processing and weight. Since the coefficient of linear expansion of aluminum is 23X10-'/"c, the amount of deviation due to thermal expansion when the ambient temperature changes from 5℃ to 35℃ (temperature difference 30℃) is calculated by setting the installation span of CC:Dlo to 3051 When calculated, Δ(1=Q・α・Δt (Q: length, α: coefficient of linear expansion, Δt: temperature difference) ΔQ = 3
05X23X10-'/℃X30℃= 210p
m.

CC with 5000 reading elements integrated at 7μm pitch
When the projection is reduced to 1/9 using Dl0, if the above-mentioned deviation amount of 210 μm is converted into pixels, the deviation will be 3.4 pixels (pickles).

This is due to the expansion of the base member 14 only, and considering the position of CGDlo, the expansion of the mounting bracket 17, 20, the printed circuit board 15, and the CCD 10 itself are also added, so the actual measured value is the temperature change of 30°C. Approximately 0.
It shifts by 8mm, or about 13 pickles (P 1xel) in terms of pixels.

If there is a deviation of about 0.8 mm at the seam, the output image will be missing or, conversely, doubled, resulting in a reduction in image quality.

In this embodiment, the ambient temperature of the CCD is detected by a temperature sensor such as a thermistor, the detection signal is amplified, and the A/D
The digital value is converted and stored as CCD data. The address point at which RAM readout starts is changed to compensate for deviations due to thermal effects when the ambient temperature changes.

FIG. 4 is an overall control block diagram. CCD1~3
is driven by the clock signal of 8 M I (z, and the drive clock and 5YNC signal etc. are CLOCK&TIMING
Made by the GENERATOR department. , C0D1-3
scans each assigned area on the document at the same timing and outputs it as a 5000 P 1xel image data string.

The output of the CCD is approximately 0.1 V at the white level, which is very small, so if it is directly A/D converted, the conversion error will become large due to the influence of noise, etc., so it is amplified approximately 10 times by VIDEOAMP. Since the drive clock is superimposed as noise on the CCD, only the signal components are extracted by sampling.

GAIN C0NTR0L is a variable amplifier that keeps the white level of the signal input to the A/D converter constant. Prior to scanning the document, it converts the white color of the document pressure plate into a pixel signal, and the maximum level is the maximum of the A/D conversion. The amplification degree is controlled so as to have the value (3FH for 6 bits).

The A/D converter converts an analog signal into a digital signal, and here a 6-bit one is used to convert the signal level from white to black into data with 64 gradations.

RAM is for memory of shading correction data, and C of 1 to 5000 Pjxel when reading the original pressure plate.
The CD output is stored as 6-bit data and used as reference data for correcting a decrease in peripheral light intensity of the optical lens, uneven sensitivity of each CCD, uneven light intensity of the illumination lamp, etc. ROM
Data is written in the CCD so that it operates as a type of arithmetic unit, and the output of each CCD when an original is scanned is extracted as data after shading correction.

The 6-bit shading-corrected pixel data from the ROMI is input to a toggle buffer consisting of RAM4 and RAM5. S E L 1 is RAM4 and R
AM5 is selected alternately, TIME GE
It operates based on the switching signal from NERATOR.

The first scanned data is stored in RAM 4 from 1 to 50.
Store as 6-bit data of 00. The RAM address is 8M at ADDRESS C0UNTERI.
]-1z is controlled by 5EL2. At the same time, the output of CCI) 2 is stored in RAM 6 as 6-bit data from ROM 2, and the output of CCD 3 is similarly stored in RAM 8.

In the next scan, the output of CCD1 goes to RA, M5,
The output of CCD2 is sent to RAM6, and the output of CCD3 is sent to RAM.
9 is also stored. At this time, the data stored in the RAM 4 is read out by the ADDRESCOUNTER 2 which is address-driven using a 24 MHz clock. ADDRESCOUNTER2 is composed of three blocks of counters, counters 1 to 3, as shown in the left block of FIG. Counter 1 controls the address of RAM 4.5 that stores the data of CCD 1, and counter 2 controls the address of RA M 4.5 that stores the data of CCD 2.
Counter 3 controls RAM8.9. Counter 1 sets the reading start point as PDSW (PR
ESET DATA 5WITCIH), reading starts from address 52 and data up to address 4948 is read.

The reason why the data of each CCD is set at the 52nd position instead of the 1st and the end is set at 4948 instead of 5000 is as follows. In other words, 1. The MTF of the optical lens that projects the image onto the CCD gradually decreases toward the periphery, and the aberration of the optical lens increases, making it easier to cause magnification errors and focus shifts, so data at both ends is truncated. , in order to equalize the quality of the left and right ends. In this case the second
As shown in the figure, it is only necessary to provide six areas including overlap, so if we consider it based on Figure 2, (
312,5X3-918)/3=3.25nn, converted to one pixel, becomes 3.25X]6=52 Pixel.

When the value of counter 1 reaches 4948, a match signal is output, gate 1 is opened, and a 24 MHz clock signal can be input to counter 2. At the same time, 5EL13 is switched and data from CCD2 from 5EL1'l is output. so that

The counter 2 is inputted as preset data with a converted voltage value from a thermistor 21 attached to detect the temperature at the mounting bracket 20 of the CCD 2 placed in the center, which is IA/D converted into 8 bits. . This value is set to be 52 at 20°C. This setting is set as DC offset by VRI.
It has been added to the second amplifier. By turning the VRI, the reading start point of the CCD 2 can be continuously changed.

In this example, settings were changed using analog means, but they can also be changed digitally using dip switches and an adder.

The data in RAM6 is 5 at around 20℃ using counter 2.
Read from address 2 to address 4948. When the value of counter 2 reaches 4948, it outputs a match signal in the same way as counter 1, opens gate 2 and allows a 24 MHz clock signal to enter counter 3, and at the same time switches 5EL14 and outputs the data of CCD 3 from 5EL12. so that

As with the counter 2, the precera l-data of the counter 3 is inputted with a value obtained by A/D converting the output voltage from the thermistor 21 attached to the mounting bracket 20 of the CCD 3, and is set to 52 when the temperature is around 20°C. is set to . This setting method is the same as counter 2, but
Since CCD3 is twice as far from CCD1, the temperature correction value will be larger, so the amplification degree of A4's amplifier should be changed to
It is larger than 2. Note that the value of expansion at the COD portion cannot simply be doubled because of the expansion of the mounting member as described above, so it must be determined based on actual measurements.

Data in RAM 8 is also read from address 52 to address 4948 at around 20°C using counter 3. counter 3 to 4
When 948-52=4896 clock signals are input, the total number of data is 918X16=4896X3="1.4
688, one line of main scanning is completed. On the second line, data from RAMs 5, 7, and 9 are sequentially read out.

When the temperature rises above 20"C, assuming that CCDI is fixed as shown in Figure 8, CCT, ) 2 will expand and move away, so at the same point on the manuscript, CCDZ
At the top, it moves to the downstream side of the document reading section.

In the configuration shown in FIG. 5, when the temperature rises, the electrical resistance value of the thermistor 21 decreases, and the voltage at the ten inputs of A2 increases, so that
The /D conversion value increases, and the readout and start address values of the RAM 6 increase to compensate for the seam deviation.

The amplification degree of A2 in Fig. 5 is determined by the resistance value R of thermistor 2■.
The A/D conversion value per 1° C. is determined based on the resistance value of 1, etc. so that it becomes the desired correction value.

If the seam is misaligned, the total number of data will be incorrect if the final read address of the CCD 3 is fixed, so another counter 4 is provided, and data is read out by the counter 3 until the total number of data is reached. When the counter 4 reaches the total number of data, the gate 2 is closed and the operation of the counter 3 is stopped.

In FIG. 5, the temperature is detected by the thermistor 21, but other means, such as a thermocouple, can also be used by increasing the amplification of A2 or A4.

In the example shown in FIG. 5, compensation is made assuming that the position of another COD changes with CGDI as a reference, but compensation can be made in the same way even if the position of another COD changes to the left or right with C0D2 as a reference. An example of the configuration in this case is shown in FIG.

Counter 5 (This is a counter that counts the number of scan data in order to change the scan end point of CCD 1 depending on the temperature. Preset the value of A/D 1, change the count number, and change the upper limit value of counter 1. Counter 5 counts. When finished, gate 3 is closed, clock signal input to counter 1 is stopped, gate 1 is opened, and counter 2 is input.
starts the currant. The reading start and end of this counter 2 are fixed. Counters 3 and 4 are the same as in FIG.

In this way, if CCD2 is used as a reference, the temperatures of CCD2 and CCD3 will be the same, and therefore A2 and A2 will be the same.
Setting the amplification level of the 4th amplifier becomes easier.

When the temperature range to be compensated for increases, in the case of a thermistor, the change in resistance value is not linear, so a deviation occurs between the noise level deviation compensation and the actual value. In this case, after A/D conversion, RO
Connect M, put the compensation value in RQN, 1 data,
You can compensate accordingly. In this case, the relationship between temperature and compensation value may be non-linear. In addition, the temperature to be detected is not limited to a few components, but multiple temperature sensors such as CC, D itself, and other mounting components are provided, and the detection output of each temperature sensor is A/D converted and stored in the ROM. Compensation as a function of multipoint temperature is also possible.

An example of this is shown in FIG.

It is desirable to constantly perform temperature compensation while scanning a document, but if it is constantly performed, the A/D converter may malfunction due to external noise, or the output may fluctuate due to quantization errors. However, since there is a risk that the seam portion may shift, it is recommended to prohibit the conversion operation of the A/D converter while scanning the fjK document.

FIG. 8 schematically shows the case where one line of composite data is created from the read data of ccot~3.

Also, if we show the timing of the aforementioned S Y N C signal, the output signal of ccot~3, the output signal of RAM4.6.8, the scan start signal, and the A/D conversion hold signal,
As shown in Figure 9.

Furthermore, FIG. 10 is an explanatory diagram showing a case where the CCD 2 is shifted to the left in the drawing due to thermal expansion.

In the above embodiment, a case has been described in which the original image is reduced through an optical lens and read by a CCD, but the present invention is not limited to this. The present invention can also be applied to a close-contact type image reading device with a 1:1 magnification.

(Effects) Since the present invention has the above-described configuration, temperature compensation at the image seam portion is reliably performed, and the reliability of image reading can be improved.

[Brief explanation of the drawing]

The figures are all for explaining an image reading device according to an embodiment of the present invention, and FIG. 1 is a schematic configuration diagram of the image reading device;
Figure 2 shows the optical lens and CCD of the image reading device.
An explanatory diagram showing the arrangement state of. Figure 3 is a front view showing the optical lens and CCD in the open state, Figure 4 is an overall control block diagram, Figures 5 and 6.
Figure 7 and Figure 7 are block diagrams of the main parts, Figure 8 is each CC
An explanatory diagram when the read data of D is combined into one line. Figure 9 is a timing chart 1-1. Figure 10 is an explanatory diagram showing the case where the CCD is displaced due to thermal expansion. Figure 11 is an illustration of the case where the CCD is shifted due to thermal expansion. FIG. 3 is a diagram for explaining a minute Jfi reading area. 1...Manuscript, 9...Optical lens, 10
...CCD, 21...Thermistor. Figure 1 Figure 2

Claims (1)

[Claims] (1) An illumination means for illuminating the document surface, and a plurality of illumination means for scanning the document line by line and converting optical signals from the document surface into electrical signals whose reading area is divided into a plurality of sections along the main scanning direction. a photoelectric conversion element, a temperature detection means for detecting the temperature near the photoelectric conversion element, a memory for storing read data from the photoelectric conversion element at predetermined addresses, and a temperature detection signal from the temperature detection means. 1. An image reading device comprising: address control means for controlling a read start address or end address of memory data based on the read start address or end address of memory data.