JPS5828945B2 - Graphic input device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a graphic input device, and particularly to an operation method of a light receiving element array in a scanning photoelectric conversion portion thereof.

FIG. 1 shows an example of a light-receiving element array used in a graphic input device or the like.

The array illustrated in Figure 1 uses a photodiode as a light receiving element and a CCD as a scanning circuit, and is an array in which several dozen to several dozen photodiodes and scanning circuits are integrated on one silicon wafer. So, generally C
This is called a CD photosensor array.

The part surrounded by a broken line 1 in FIG. 1 is a photosensor array integrated circuit (hereinafter referred to as a sensor), and photodiodes 2 are arranged in a straight line.

Each photodiode 2 is connected to a CCD shift register (hereinafter referred to as a CCD register) through a transfer gate 3.
It is connected to each cell of 4.

Further, each photodiode 2 is connected to a bias power supply 6 through a photogate 5.

A transfer gate (hereinafter referred to as TG) 3 is connected to the input line 7.
A signal is input to open and close the T.
G3 opens and closes at the same time.

A signal for opening and closing the photogate (hereinafter referred to as PG) 5 is inputted to the input line 8, and each PG 5 opens and closes simultaneously according to the signal.

Information in each cell of the CCD register 4 is transferred from the left to the right in the figure by a clock 9, and the output line 10 from the rightmost cell 4n is connected to the input terminal of the amplifier 11. Therefore, the output information of the cell 4n is amplified and taken out from the output terminal 12.

Figures 2 a to d are time charts showing the operation of the light receiving element array shown in Figure 1, where a is the input line 8 and b is the input line 7.
, c indicates the clock 9, and d indicates the signal at the output terminal 12.

Time T. PG5 becomes a contact at .

That is, when a signal is applied to the input line 8 so as to bias the fort diode 2, a charge proportional to the amount of light input to the photodiode 2 is generated and accumulated therein.

Since the large number of photodiodes 2 are each separated independently, the photodiodes 2 to which light is strongly incident will accumulate a large amount of charge, and the photodiodes 2 to which light is weakly incident will accumulate a small amount of charge. Ru.

Since charges are accumulated in this manner, the amount of charges is proportional to the product of the input light amount and the accumulation time, making it possible to perform highly sensitive photoelectric conversion operations.

Next, at time T1, a signal is applied to the input line 1 so that Ta2 is connected, and when PG5 is disconnected at time T2, the charge accumulated in the photodiode 2 is transferred to each corresponding cell of the CCD register 4. be done.

At time T3, TG3 is disconnected and clock 9 becomes CC.
When input to the D register 4, the charges in each cell of the CCD register 4 are sequentially transferred to the right in synchronization with the clock 9, and the output terminal 12 of the amplifier 11 is connected to the photodiode 2.
The output proportional to the charge accumulated in the photodiode 2
The items corresponding to those on the right are output in order.

When clocks 9 corresponding to the number of cells (n in this example) of the CCD register 4 are output, the amount of charge accumulated in each of all the photodiodes 2 (n) is expressed as a voltage in time series. This appears in the voltage at the output terminal 12, and one scan is completed.

Let this time be T5. Since the light quantity accumulation and photoelectric conversion operations can be performed independently of the CCD register 4, if PO2 is connected at time T4, accumulation will start from that time.

Time T4 can be any time after time T3, so the second
The positions shown in the figures are only examples.

Here, the time To-T2 is the accumulation time of the photodiode 2, and if the amount of incident light is constant, the length of the output terminal 12 is proportional to this length.

The time from T3 to T is the scanning time, and the shift clock 9
The product of the period t and the number n of CCD registers 4, that is, tn time is required.

Although one cell is shown as one quadrilateral in FIG. 1, the CCD register 4 is actually composed of several (for example, four) elements, and the voltage applied to each element changes. As a result, charges are transferred, but the details are omitted here.

When attempting to configure a graphic input device using the sensor 1 illustrated in FIG. 1, if the number n of photodiodes 2 is increased to improve its resolution, the elements of the CCD register 4 will be several times n (for example, 4 times), sensor 1
creates significant difficulties in manufacturing.

In order to avoid this, it is conceivable to configure the sensor 1 with n photodiodes 2 and a CCD register 4 having a fraction of the number of cells.

Figure 3 shows an example of a sensor with such a configuration.
The number of cells in D register 4 is % of the number of photodiodes 2
(Half) is an example.

In FIG. 3, the part surrounded by the broken line 13 is the sensor, and the photodiodes 2 are arranged in a straight line.

Every other photodiode 2 is connected to TG30, and every other photodiode 2 is connected to TG3E, and the other terminals of TG30 and TG3E are connected to each other as shown in the figure. Tied C
It is connected to one corresponding cell of the CD register 4.

Similarly, every other photodiode 2 has P
Connected to G50 and PG5E, PO50 and PG
The other terminal of 5E is connected to bias power supply 6.

A signal for controlling the opening and closing of the TG 30 is input to the input line 70, and each TG 30 is simultaneously opened and closed by the signal.

The input line 7E similarly controls the opening and closing of the TG 3E, and the input line 80 receives a signal that controls the opening and closing of the PO 50, and each PO 50 is opened and closed at the same time by the signal.

Input line 8E similarly controls opening and closing of PG5E.

The operation of the sensor 13 in this example is based on the input lines 70, 80 . The clock 9 and the output terminal 12 operate according to the time chart shown in FIG. 2, but the number of output photodiodes 2 is half the number of photodiodes 2 shown in FIG. 7E.

The same applies to 8E, clock 9 and output terminal 12.

In other words, when the number of photodiodes 2 is n, by inputting the signals shown in FIG.
Output terminal 12 outputs discrete photoelectric conversion outputs for every other optical pattern input to the photodiode 2 part of 3.
Similarly, if input lines 7E and 8E are used, the remaining every other photoelectric conversion output is output to output terminal 12.

A scanning method in which scanning of every other photodiode 2 is performed once for each different photodiode 2, that is, twice in total to scan the entire photodiode 2, is generally called interlaced scanning. )
It is called.

FIG. 4 shows a schematic configuration of a graphic input device using a CCD photosensor array that performs such interlaced scanning.

That is, figures, characters, etc. (hereinafter simply referred to as figures) drawn on the original 14 are imaged onto the sensor 13 by the lens 15.

Since the sensor 13 is made up of a large number of photodiodes 2 arranged in a straight line, it is the straight line 16 on the original 14 that is photoelectrically converted.

The illumination means 1γ illuminates a straight line 16 on the original 14.

Since the graphic information on the original 14 is two-dimensional, it is raster scanned by main scanning by the sensor 13 and sub-scanning by sending the original 14 in the direction of arrow 18.

Motor 19, paper feed roller 20 and pinch roller 21
is for performing sub-scanning, and the motor 19 is
By rotating in the direction 2, the document 14 is sent in the direction of the arrow 18.

When the original 14 is scanned using such a device, a location on the original 14 as shown in FIG. 5 is photoelectrically converted during main scanning.

That is, by scanning every other photodiode in the first half of l main scanning, 23 at23 b...2
The part 3-X is photoelectrically converted, and in the latter half 24-a and 24-
The portion b...24-X is photoelectrically converted and one main scan is completed.

This staggered pattern in the sub-scanning direction in one main scan indicates that the photoelectrically converted figure is significantly distorted compared to the original figure.

In order to avoid this, methods such as (a) stopping the sub-scanning until the main scanning is completed, and (b) arranging the photodiodes 2 on the sensor 13 in a staggered manner can be considered, but (' Regarding method I'), the sum of the times required for main scanning and sub-scanning is the time required for one main scanning, and the operating speed of the device, that is, the time required to input one document 14 is increased. It has the disadvantage of becoming.

Regarding method (b), the spacing at which the photodiodes are arranged in a staggered manner differs depending on the sub-scanning resolution, and once a graphic input device is determined, the sensor 13 to be used for it is determined, which reduces the versatility of the sensor 13. , sensor 13
price increases.

In addition, in manufacturing the sensor 13, arranging the photodiodes 2 in a staggered manner increases variations in each photodiode 2, which also has the disadvantage of increasing the price of the sensor 13. there were.

This invention was made in order to eliminate the above-mentioned drawbacks, and without causing the above-mentioned disadvantages such as a decrease in the operating speed of the device, a decrease in the versatility of the sensor, and an increase in the price of the sensor,
It is an object of the present invention to provide a graphic input device that can obtain good image quality without graphic distortion.

The present invention will be described in detail below with reference to the drawings.

6a to 6f are time charts showing the operation of one embodiment of the graphic input device according to the present invention, in which a to d are signals on the input lines 80, 8E, 70, and 7E in order, e is the scanning time on the O side, f is a signal indicating the E-side scanning time.

Note that the explanation will be made using the sensor shown in FIG. 3 as an example.

That is, at time T6, a signal is input so that the input line 80 is connected to the PG 50, and a light amount accumulation operation is performed for every other photodiode 2 connected to the PG 50.

At time T7, the accumulation operation is ended, and just before that, a signal is input to the input line 70 so that TG30 is connected.

When PG30 is disconnected at time T7, photodiode 2
The charges generated and accumulated in every other one of the CCD registers are transferred to the CCD register 4, and then clock 9 is applied from time T8 to T9.
are input in a number corresponding to the number of bits of the CCD register 4, and photoelectric conversion outputs corresponding to every other photodiode 2 are sequentially output to the output terminal 12.

That is, from time T8 to T, photodiode 2
Counting from the left side, numbers 1, 3, 5... (odd numbers)
This means that the eye photodiode 2 has been scanned.

However, the accumulation time of these photodiodes 2 is at time T6.
~T7.

The remaining photodiodes 2, i.e. 2, 4, 6...
...For the (even numbered) item, the time 'f'io
It is accumulated and output from time T13.

Since time T14 is the time when the odd-numbered photodiode 2 starts accumulation again, the repetition time of this operation is from time T6 to 'I'14, that is, tB, and the interlaced scanning interval is from time T6 to T1. That is, ti.

Note that for the odd-numbered photodiode 2, the time T
6 to T7 is the accumulation time, and similarly, for even-numbered photodiodes 2, the time T 10 """' T 1
□ is the accumulation time.

The interlaced scanning interval ti is set to be shorter than this accumulation time.

Figure 7 shows the original 1 when using the apparatus illustrated in Figure 4.
25-a, 25-b...
...The portion 25-x is photoelectrically converted, and the even-numbered photodiodes 2 convert it into 26-a, 26-b...
26-X part is photoelectrically converted o25' a, 25
' -su,,,,25/ x and 26'aj2
6'-b...26'-X are portions to be photoelectrically converted during the next scan.

PR is the scanning pitch, Pi is an odd number due to interlaced scanning,
It shows the deviation of even-numbered photoelectrically converted parts.

In FIG. 4, if the speed at which the document 14 is fed in the direction of the arrow 18 is constant, the ratio of PR and Pi will be equal to the ratio of tB and tl, so if ti is made sufficiently smaller than tR, Pl will be This is sufficiently small compared to PR, and image distortion can be made sufficiently small.

Specifically, when used in a facsimile reading section, for example, the ratio between ti and tH (equal to the ratio between Pi and PR) is permissible up to about 1:5.

When used as OCR, i:i. If the ratio is below this level (as the ratio approaches 1:1), the reading rate (the rate at which characters are correctly recognized) will suddenly drop.

In addition, if a pulse motor or the like is used as a means for feeding the document 14, and the speed is not constant, the repetition time tB will change, but since it is necessary to operate so that the accumulation time is constant, the above-mentioned repetition time tH, The same explanation can be given in other words in terms of accumulation time.

In the above method, the scanning pitch PR shown in FIG. 7 is a very narrow pitch of 1 to 3 times the array pitch of photodiodes on the document surface (for example, 125 μm), and only this PR is used as a sub-pitch. The storage time of the photodiode must be set to be less than or equal to the time during which scanning is performed.

Therefore, image quality does not deteriorate due to the relationship between sub-scanning and accumulation time.

Further, in the above method, the sub-scanning is a sub-scanning that can be regarded as continuous at least during a lifetime scanning (a set of interlaced scanning).

As explained above, according to the present invention, even if an inexpensive sensor with a large number of bits that requires interlaced scanning is used, it is possible to maintain a large ratio between the repetition time (accumulation time) of the operation and the time interval between interlaced scanning. This has the effect that the distortion of the image signal caused by interlaced scanning can be sufficiently reduced, and a graphic input device with good image quality can be obtained.

Incidentally, the interlaced scanning sensor was designed to reduce the number of bits in the shift register rather than the number of photodiodes, but its purpose is, for example, to divide a photodiode row into a left half and a right half, and This can also be achieved by connecting the same number of photodiodes to one bit of the shift register via their gates.

However, in such a construction method, an intersection occurs in the wiring between the photodiode array and the shift register, making it impossible to manufacture the sensor using integrated circuit technology that provides wiring on one plane.

Furthermore, the lengths of the wires vary and the signal level is affected by the length of the wires, making it impossible to obtain a good image signal.

Interlaced scanning sensors can overcome these drawbacks.

[Brief explanation of the drawing]

Fig. 1 is a configuration explanatory diagram showing an example of a light receiving element array (sensor), Figs. 2 a to d are time charts showing the operation of the above array, and Fig. 3 is a configuration showing an example of a light receiving element array in an interlaced scanning method. An explanatory diagram, FIG. 4 is a schematic configuration diagram showing an example of a graphic input device using the same array as above that performs interlaced scanning, and FIG. 5 is a diagram showing the location of photoelectric conversion on a document when using the above device, Figures 6a to 6f are time charts showing the operation of one embodiment of the graphic input device according to the present invention, and Figure 7 is a diagram showing locations of photoelectric conversion on a document when the same device according to the invention is used. . 2...Photodiode, 30,3E...
...Transfer gate (TG), 4...CC
D shift register, 50,5E...Photogate (PG), 6...Bias power supply, 70,7E
, 80, 8E...Input line, 9...Clock, 10...Output line, 11...Amplifier, 12...Output terminal , 13... Photosensor array integrated circuit (sensor), 14...
Original, 15...Lens, 1γ...Illumination means, 19...Motor, 20...Paper feed roller, 21...Pinch roller , tR...
...Repetition time, tl...Interlaced scanning interval,
PR...Scanning pitch, Pi...Difference due to interlaced scanning.

Claims (1)

[Claims] 1. A plurality of light-receiving elements that accumulate charges corresponding to the amount of light from figures arranged in a straight line and moving in a direction perpendicular to the arrangement for a predetermined time according to a signal to the photogate, and one line scanning for each cell. an interlaced scanning circuit which has a shift register in which adjacent light receiving elements of the same number as the number of times are sequentially connected via a transfer gate, and sequentially extracts the output of each light receiving element as a time series signal by performing interlaced scanning a plurality of times by switching the transfer gate; A graphic input device, characterized in that the interval between the beginning and end of the interlaced scanning is set to be shorter than the charge accumulation time of the light receiving element.