JPS63112899A - Driving circuit - Google Patents

Abstract

PURPOSE:To reduce a chip area in case a driving circuit for reading out many input signals is formed by an IC, by providing a bidirectional shift register of (m) bits, on the driving circuit for executing bidirectional read-out and reading out many input signals, by using the bidirectional shift register. CONSTITUTION:At the time of executing a scanning from the left to the right, a scanning switch 2-1 is turned on, and thereafter, a resetting switch 5-1 is turned on by being delayed by (m) bits. Switches 2-2, 2-3 are turned on successively, and thereafter, switches 5-2, 5-3 are turned on by being delayed by (m) bits, respectively. In such a way, continuous read-out can be executed. On the contrary, at the time of executing the scanning from the right to the left, continuous read-out of an image sensor can be executed by driving the shift registers 4-1-4-n and 4-01-4-0m in the reverse direction. In such a way, when the shift register for a dummy bit is made bidirectional, an image sensor driving circuit which can execute a bidirectional scanning is obtained by only providing (m) pieces of shift registers.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a drive circuit for reading signals from an image sensor or the like, and particularly to a bidirectional drive circuit using a shift register.

[Conventional technology]

A large number of optical sensors, such as image sensors in which photodiodes are arranged, are used as part of facsimile sensors.

In particular, the importance of this technology is increasing as a sensor made of amorphous silicon that is as long as a manuscript has been realized.

Since this photosensor has a large number of photodiodes lined up, in order to obtain a video signal from this photo sensor, a drive circuit is required to sequentially read out the image sensor consisting of a photodiode array.

FIG. 2 is an example of a drive circuit including a portion of the sensor. In the figure, 20 is a sensor consisting of a photodiode, etc., and many of these sensors are lined up to form an image sensor.
is made. 21 is a voltage follower, which operates as an impedance converter. 22 is N-MO3F
A scanning analog switch consisting of ET22' and P-MO3FET22, 23 is a level shifter, 24
．． 25 are shift registers. 26 is an inverter, and 27 is a stray capacitance parasitic to the wiring section.

In the drive circuit of such an image sensor,
When light is incident on the sensor 20, this
The charge corresponding to the amount of incident light is accumulated in the capacitor 27 including the capacitor 27 .

The potential level is received by a voltage follower 21, and a scanning analog switch 22 is opened and closed to obtain a video signal as an output signal.

Timing signals for opening and closing the scanning analog switch 22 are generated by shift registers 24, 25-. Inverter 26 includes N-MOS22', P-MO32
This is used to generate signals for opening and closing an analog switch consisting of two FETs.

Each shift register is provided with a clock input 27 and a scan input, and a delayed scan input is obtained for each clock from the shift register, and this signal opens and closes the analog switch 22 for scanning.

At this time, if there is any charge remaining on the input line after reading out the sensor, this will be read out at the same time when the next image signal is read and noise will be mixed into the image signal, so a glue set circuit is used to ground the input line. It is necessary to provide

FIG. 3 shows an example in which this reset circuit is provided with analog switches 31, 32- of CMO3 configuration.

In the figure, 21.21' corresponds to the voltage follower 21 in FIG.
．． The output of 21' is input to the scanning analog switch. Also, the terminal 36. which is the input of the voltage follower.
37 are each connected to a sensor.

In FIG. 3, after turning on the scanning analog switch and reading out the video signal, the analog switch 31
．． 32 is turned on in sequence and terminals 36, 37 are turned on in sequence to reset and ground any remaining charge on each input line.

However, since the stray capacitance 33 exists between the input lines of adjacent sensors, there is a problem in that the output signal of the next stage is affected depending on the reset timing.

To solve this problem, we changed the reset timing to
It is better to delay the reading as much as possible.

FIG. 4 shows an example of such a drive circuit in which the reset timing is delayed by m bits.

In the figure, 46-1.46-2---46-n is
This is a shift register, and generates a control signal to sequentially turn on and off the switches 47-1, 47-2-47-n in accordance with the clock from the terminal 43. These constitute an n-bit driver.

45-1.45-2 to 45-n are shift registers 46
This is a level shifter that receives an output such as -1 and converts the level, and the output of this level shifter causes the switch 4 to
7-1.47-2- is controlled.

44-1.44-2 to 44-n are voltage followers that receive outputs from the sensors connected to the terminals 40-1.40-2 and 4Q-n, and are connected to the aforementioned switch 47-
1 to 47-n, the video signal output is output to the terminal 42. The switches 47-1, 47-2 to 47-n are sequentially opened and closed in response to control signals from the shift registers 46-1, 46-2 to 46-n, so that the outputs of the sensors arranged in rows are serially transmitted. It will be output as a video signal.

As mentioned above, the switch 48-L is used to ground the charge remaining on the input line after reading out the video signal.
48-2 to 48-n are provided. Then, for example, after the switch 47-1 is closed and the output of the sensor is read, the switch 48-1 is closed after m bits.
Remove any residual charge on this line.

Therefore, in order to close the switch 48-n after n bits after reading the output 40-n from the n-th sensor by closing the switch 47-n, a dummy bit for m-bit delay reset is required. Shift register arrays 46-01 to 46-0m are required.

In the example shown in FIG. 4, the switch 47-1.47-2-4
7-n is turned on in the above order to read the sensor, that is, to scan only from the left to the right in the figure. It becomes necessary to scan to the left.

FIG. 5 is an example in which left-to-right and right-to-left scanning is made possible in this manner. In the figure, the same members as in FIG. 4 are given the same numbers.

In this case, as the shift register 56-1.56-2--56-n constituting the n-bit driver, a shift L-register that can be shifted in both left and right directions is used.
A shift register group 4.6-01~ is a dummy pin for m-bit delay reset on the right part of the n-bit driver.
In addition to 46-0m, shift register groups 46-01' to 46-0m', which are dummy bits for m-bit delay reset, are also provided on the left side of the n-bit driver. In addition, the input line reset switches 58-1 to 58-n provided in the sensor line are connected to the shift registers 46-01 to 46-0m and the shift register 46-01.
It is also controlled by signals from both '~46-0m'.

Therefore, when scanning from left to right, the switches 58-1. At the same time as grounding, when scanning from right to left, shift register group 4
By using 6-01' to 46-0m', m
Bit-delayed reset may be enabled.

[Problem that the invention seeks to solve]

As mentioned above, if you try to reset the input line to completely remove the charge remaining on the input line at a timing delayed by m bits from the time of reading, even in the case of unidirectional scanning, n+m Bit shift registers are required.

Furthermore, in order to provide more freedom in the directionality of image sensor reading, bidirectional scanning (bidirectional scanning) is possible.
In order to make this possible, a 2m-bit shift register is required for an n-bit driver, as shown in FIG. If this is directly laid out as an integrated circuit, there is a problem in that the required chip size becomes large.

The present invention has been made in view of the above points, and provides an image sensor drive circuit that enables bidirectional scanning and is capable of reducing the chip area when integrated into an IC. The purpose is to provide circuits.

[Means and operations for solving the problems] In order to solve the above-mentioned problems, the present invention provides a drive circuit for reading out a large number of input signals that performs bidirectional reading using a bidirectional shift register. It is characterized by providing an m-bit bidirectional shift register.

This makes it possible to reduce the chip area when implementing the drive circuit for reading a large number of input signals into an IC.

〔Example〕

FIG. 1 shows an embodiment of the invention. In the figure, 1 to
1.1-2, ~1-n are voltage followers,
The image sensor outputs from the terminals INI and TN2 to INn are sequentially sent to the output line 6 as video outputs via scanning switches 2-1.2-2 to 2-n. 3-1.3-2, ~3-n are level shifters, and switches 2-1.2-2~ for scanning the levels of signals from shift registers 4-1.4-2~4-n. 2-n
The scanning switch 2 is suitable for driving.
-1.2-2 to 2-n.

Further, the switches 5-1, 5-2 and 5-n are reset switches for removing charges remaining in the sensor input lines INI to INn. The reset switch 5-1 closes with a delay of m bits after the switch 2-1 closes.

Each switch 2-1.2-2, ~2-n and switch 5
It goes without saying that the analog switches explained in FIGS. 2 and 3 can be used for -1.5-2 and 5-n.

The n-th switch 5-n turns m after the switches 2-n are turned on.
Since it turns on after a bit delay, m for dummy bit
Shift register 4-01 for m-bit delay reset
~4-0m is provided.

The above is basically the same as the conventional example shown in FIG. 5, but in this invention, the shift register 4-01 for m-bit delay reset for dummy bits is
~4. - using a bidirectional shift register as Om,
ff! to the shift I register 4-0m for the seso I, which delays the shift output from the shift register 4-1 of the n-pi-) lime by m bits. and shift registers 4-1 to 4-
n and 4-01 to 4-0m form a closed ring.

In such an image sensor drive circuit, when scanning from left to right, the reset switch 5-1 is turned on with a delay of m-pitch 1 after the scan switch 2-1 is turned on. Sequential scan switch 2-2.
After turning on the reset switches 5-2 and 5-3, the reset switches 5-2 and 5-3 are turned on after a delay of m pins. In this way, when the switch 2-n is finally turned on, after m bits, the switch 5-m is driven by a signal from the dummy shift register 4-0m and reset is performed. Shift 1 to register 4-0m and shift register 4-1
are connected to each other and these shift registers form a closed ring, this operation again
-1, and continuous reading becomes possible.

Conversely, when scanning from right to left, continuous readout of the image sensor is possible by driving the shift registers 4-1 to 4-n and 4-01 to 4-0m in the opposite direction. It is also clear that

Although the invention has been described above using a driver circuit for an image sensor as an embodiment of the invention, it goes without saying that the invention is not limited to this and can be used for general driver circuits.

Note that in the figure, for the purpose of simplifying the explanation, a control signal circuit for controlling the shift register to the right or left is omitted.

〔Effect of the invention〕

As described above, in this invention, by making the shift register for dummy bits bidirectional, it is possible to realize an image sensor drive circuit capable of bidirectional scanning by simply providing m shift registers. .

This can be done, for example, by performing a reset with a 64-bit driver.
If 0 bits are delayed, a shift register for 84 bits would originally be required, but only a shift register for 74 bits would be required, resulting in an area reduction of about 12%.

Furthermore, since the later the reset is, the less influence it has on the output signal line, by delaying the reset further, the performance of the drive circuit can be further improved, and in this case, the effects of the present invention are further enhanced.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the invention, FIGS. 2 and 3 are diagrams explaining the operation of the image sensor drive circuit which is the principle of the invention, and FIGS. 4 and 5 are FIG. 3 is a diagram showing a conventional example. ■-1, 1-2~l-n Voltage follower, 2-
1.2-2 to 2-n scan switch, 3-1.
3-2~3-rr-level shifter, 4-1.4-2~
4- Shift register for n--n hit driver, 4-01.4-02~4- Shift register for Om-m bin 1-delay reset 1~, 5-1.5-2~5-n-reset switch .

Claims (1)

[Claims] A shift register is used to sequentially read out a large number of input signals, and a reset switch for input line grounding is provided on the input line of the input signal, so that the input signal is read out after a predetermined delay of m bits after the input signal is read. In the drive circuit which resets the input signal line by turning on the reset switch, m bidirectional shift registers for m-bit delay reset are provided to enable bidirectional scanning. and the drive circuit.