JPS60174569A - Photosensor driving device - Google Patents

Abstract

PURPOSE:To simplify circuit constitution and to perform a read without any influence of a noise by turning on analog switch elements for input selections of respective operational amplifiers successively with a specific lag, and turning on analog switch elements for output selection a specific time later. CONSTITUTION:Photosensor elements R1k, R2k...R4k (k=1...8) in a small block are connected to corresponding operational amplifiers OPA1, OPA2...OPA4 through analog switch elements S1k, S2k...S4k for input selection. Analog switches Sjk (j=1, 2...4) which turn turn on and ground elements Sjk when the elements Sjk are on are provided to prevent photocurrents from detouring. Here, the switches Sjk for input selection are turned on for a period with a log of time T, and analog switch elements S1...S4 for output seldcion are turned on a time tau later. Consequently, a spike noise due to the turn-on operation of an element Sjk which is generated in respective outputs of amplifiers OPA1...OPA4 is prevented from appearing in an output signal V0.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for an optical sensor that reads original image information at the same magnification in which optical sensor elements are arranged in units of pixels in an array for one line.

In general, this type of optical sensor driving device uses, for example, a-5i light that is reflected when the image plane is illuminated.

CdS 7. When light is received by a photosensor in which photosensor elements made of a photoconductor such as CdSe are arranged in an array, the output signal of each photosensor element is taken out through an operational amplifier, so that one line of each signal can be obtained. The image information is read.

In this case, providing an operational amplifier for each optical sensor element would complicate the circuit configuration, so conventionally, the first
As shown in the figure, the photosensor element groups R1 to Rm arranged in an array are equally divided into a plurality of blocks B1 to Bn, and the number of photosensor elements in each block is 12 (
= m/n) operational amplifiers 0PAI to 0PAQ are provided,
The optical sensor driving device is simplified by applying the bias voltage E to each block while being switched by the switch element CI''Cn and reading the image information in each block sequentially.

However, even in such a device, it is necessary to provide the same number of operational amplifiers as the number of optical sensor elements divided into blocks, and normally one line of optical sensors with 2048 elements is divided into 64 blocks. However, in this case, the number of elements per block is 322, which still requires a large number of operational amplifiers.

For this reason, in the past, as shown in FIG.
Analog switch elements 81 to S connected to the input side of A
Q is provided to effectively simplify the optical sensor driving device. However, in such a device, as shown in FIG. 3, for example, when the analog switch elements 81 to SQ are sequentially turned on in a time-sharing manner during the on period of the switch element C1, an image signal output is obtained from the operational amplifier OPA. Since the ratio between the output current of each photosensor element and the noise current generated when the analog switch element is switched on is small, the image signal is lost in the noise, so the image signal is read out until the noise current attenuates. Therefore, the image information reading speed becomes slow. In particular, when a-8i, which has a small photocurrent, is used, the effect is significant.

Note that the time constant for attenuation of noise appearing on the output side of the operational amplifier OPA is normally about 3 to 4 μs.

The present invention has been made in consideration of the above points, and provides an optical sensor driving device that effectively simplifies the circuit configuration and enables quick reading of image information. It is something.

−@澹 An embodiment of the present invention will be described in detail below.

The optical sensor driving device according to the present invention basically uses a method in which each optical sensor element divided into blocks is sequentially connected to the input side of an operational amplifier using an analog switch element as shown in FIG. In this case, in particular, in the present invention, the image signal is not sampled after the noise current generated when the analog switch element is turned on has attenuated, as is the case in the past, and the image signal is not affected by the noise current. It is characterized in that the image information can be read immediately without having to read the image information.

Therefore, in the present invention, when each optical sensor element divided into blocks is sequentially connected to the input terminal of an operational amplifier using an analog switch element, the noise generated when the analog switch element is turned on is prevented from appearing on the output side of the operational amplifier. The time required from when the image information becomes unreadable until the noise attenuates and the image information becomes readable, that is, the time constant of noise attenuation is τ, and the selection time of the photosensor element per dot is When T, two operational amplifiers whose integer part value is greater than or equal to (τ/T+1) are used. At this time, every second optical sensor element in the l block is connected to the input terminal of the same operational amplifier via an analog switch element for input selection, and an analog switch element for output selection is connected to the output side of each operational amplifier. A switch element is provided respectively.

However, with such a configuration, particularly in the present invention, under the control of the controller, one hour after selectively turning on the analog switch element for input selection, the corresponding analog switch element for output selection is turned on. Turn on,
Such operations are performed sequentially with a period T starting from one side of the optical sensor elements within the block.

FIG. 4 shows an example of the configuration of an optical sensor driving device according to the present invention. In this case, the time constant τ of noise attenuation is set to 3.0μ.
S, the selection time T of the photosensor element per dot is 1.0 μs, and from 3.0/1.0+1=4.0 p
= The case where four operational amplifiers are used is shown. Here, each block has 32 optical sensor elements, and each of the optical sensor elements is divided into 8 small blocks of 4 each, and the optical sensor elements R1k in each small block are
(k=]~8) is an analog switch element S for input selection
1 connected to the operational amplifier OP'AI via lk.
Similarly, the optical sensor element R2 ~4k is connected to the corresponding operational amplifiers 0PA2 to ○PA4 via analog switch elements 32k to 54k for input selection. In addition, an analog switch element S'j that is turned on when the analog switch element Sjk (j = 1 to 4) for each input selection is off and grounds the optical sensor element Rjk.
k is provided to prevent the photocurrent from going around. In the figure, 81 to S4 indicate analog switch elements for output selection, respectively. Although this diagram only shows the configuration of one block for simplicity, each optical sensor element in other blocks is similarly connected to each operational amplifier 0PAL to ○PA4 via an analog switch element Sjk for input selection. Needless to say, they are connected in parallel.

With this structure, when driving one block, the analog switch elements Sjk for input selection are sequentially switched under the control of a controller (not shown) as shown in FIG. The corresponding analog switch elements 81 to S for output selection are turned on for an L period with a T time lag, and when the τ time has elapsed, the corresponding output selection analog switch elements 81 to S
Turn on 4 sequentially. However, since each of the corresponding analog switch elements 81 to S4 for output selection is turned on one hour after the analog switch element Sjk for input selection is turned on, each output of each operational amplifier 81 to S4 is turned on. The spike noise caused by the turning on of the input selection analog switch element Sjk, which occurs in each of (1) to (4), is prevented from appearing in the output signal Vo. At that time, in particular, four operational amplifiers 0PAI to OP'A4 are provided to
Since the analog switch elements Sjk for each input selection are turned on sequentially with a difference in period, the analog switch elements 5l-84 for each output selection are sequentially turned on at a period of pXT = 4 μs to completely eliminate spike noise. This makes it possible to read image information from each photosensor element Rjk successively with a period T without waiting until the noise is attenuated.

If only one operational amplifier is used as shown in FIG. 2, a waiting time for noise decay time is required each time image information is read out from each photosensor element Rjk. Note that B in FIG. 5 indicates both signal components due to the photocurrent output from the optical sensor element.

As described above, in the optical sensor driving device according to the present invention, when each optical sensor element divided into blocks is connected to the input side of an operational amplifier using an analog switch element for input selection, in particular, the analog switch element The number of operational amplifiers to be used is determined by taking into consideration the time constant τ of noise attenuation that occurs when the sensor is turned on, and the selection time T of the photosensor element per dot, and an analog switch for input selection of each operational amplifier is determined. The elements are turned on one after another with a T shift, and the analog switch element for output selection is turned on one hour later. This effectively simplifies the circuit configuration and allows the image to be unaffected by noise. It has the excellent advantage that information can be read quickly.

[Brief explanation of the drawing]

1 and 2 are electrical wiring diagrams showing conventional optical sensor drive devices, FIG. 3 is a time chart of the operation of each part and signals of each part in the configuration of FIG. 2, and FIG. 4 is a diagram according to the present invention. FIG. 5 is an electrical wiring diagram showing a part of an embodiment of the optical sensor driving device, and is a time chart 1 of operations of each part and signals of each part in the same embodiment. Rjk... Optical sensor element Sjk... Analog switch element for input selection 0PAL-OPA4... Operational amplifier 5l-84... Analog switch element for output selection Applicant Kiyoshi Torii Figure 1 Figure 2 Figure 3 Figure - Ri Seki □ No. 511 vq F, "I □ Procedural amendment March 23, 1980 Commissioner of the Patent Office Wakasugi Kazudai Haku ■, Indication of the case 1982 Patent Application No. 030939 2, Name of the invention Sensor drive device 3, relationship with the person making the amendment Patent applicant Hiroshi Hamade 1-3-6 Nakamagome, Oide-ku, Tokyo Representative Ministry Hiroshi Hamade 4, agent 1920, month, month (shipment 1) 1920, month, day ) 6. Number of inventions made by amendment 7. Claims of the specification to be amended 29. Each column of the detailed description of the invention and gln; 8. Contents of the amendment (1) The scope of claims of the specification is as follows: Street correction code
It's true. ``Claim: In a device in which each elemental sensor element divided into blocks is connected to the input side of an operational amplifier using an analog switch element for input selection, noise generated when the analog switch element is turned on. When the decay time constant is τ and the selection time of the element sensor element per 1 dot is T, each element in In addition to connecting every p sensor elements to the input terminals of the same operational amplifier through one analog switch element for input selection, an analog switch element for output selection is provided on the output side of each operational amplifier, and the controller Under control, the analog switch elements for input selection are selectively turned on, and after 7 hours from ηλ, the corresponding analog switch elements for output selection are turned on, and such operations are repeated within a block with a period T. An optical sensor driving device characterized in that the optical sensor element is caused to perform lyA next operation from 10,000 to T) Insert J. (3) Box 5 in the drawings of this application is corrected as shown in the attached sheet. Figure 5 Sunny? □

Claims (1)

[Claims] In a device in which each of the divided photosensor elements is connected to the input side of an operational amplifier using an analog switch element for input selection, noise generated when the analog switch element is turned on is Two operational amplifiers with an integer value of (τ/Tv+1) or more are used, where the attenuation time constant is τ and the selection time of the photosensor element per dot is T. Every second optical sensor element in one block is connected to the input terminal of the same operational amplifier via an analog switch element for input selection, and an analog switch element for output selection is connected to the output side of each operational amplifier. Under the control of the controller, the corresponding analog switch element for output selection is turned on one hour after the analog switch element for input selection is selectively turned on, and such operations are blocked with a period T. 1. An optical sensor driving device characterized in that the optical sensor driving device is configured to perform the driving sequentially from one side of the optical sensor elements in the optical sensor element.