JPH04113767A - Close contact type image sensor - Google Patents

Abstract

PURPOSE:To stably supply power to each sensor chip by selecting drive means brought into an operating state at a same point of time with a prescribed combination including those corresponding at least to different line sensor chips and operating them of a prescribed number being two or over at all times. CONSTITUTION:Drivers 11-15 drive relevant sensor chips till the operating timing reaches an operation start point of time for two-succeeding sensor chip and stop driving as soon as the operation of two-succeeding sensor chip is started. That is, even after an output of all signals of one sensor chip is finished, it is driven as a dummy chip till the operation of the two-succeeding sensor chip is started. Thus, two drivers are always in operation and two sensor chips are driven and current consumption is almost constant. Thus, the power is supplied stable and an event of a change in an output signal level of the sensor chips 1-5 due to a voltage change is prevented.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a close-contact type sensor chip formed by arranging a plurality of sensor chips in a staggered manner, each of which is constructed by one-dimensionally arranging a large number of photoelectric conversion elements. Regarding image sensors.

(Prior Art) FIG. 4 is a diagram showing an example of the appearance of a contact type image sensor. This close-contact image sensor scans documents one-on-one.
A plurality (five in this case) of sensor chips (for example, CCD sensors) 1.degree. 2.3, 4.5 are arranged in a staggered manner and are integrally formed so as to be read by hand. Note that each sensor chip 1~
5 is constructed by one-dimensionally arranging a large number of photoelectric conversion elements 6 as shown in FIG.

By the way, sensor chips such as CCD sensors have excellent features such as high performance, small size, light weight, low voltage, and low power consumption, but they have the disadvantage that the output changes depending on the ambient temperature. It is necessary to correct output errors due to the influence of ambient temperature, ie, so-called dark time correction.

For this reason, in a contact type image sensor, as shown in Fig. 5, the photoelectric conversion element 6 on the reading front side of each sensor chip is masked for several pixels with a metal film, etc., and the black reference pixel (other parts are effective pixels). It is said that

Then, the signal output from this black reference pixel (black reference signal) is latched at - time, and the level obtained by subtracting the level of the black reference signal from the level of the signal of the effective pixel (effective pixel signal) that will be output thereafter is calculated. Output as the level of the read image signal.

Here, each sensor chip 1 to 5 is, for example, sensor chip 1.
→sensor chip 2 →...→sensor chip 5 are sequentially driven in this order, and the output signals of each sensor chip 1 to 5 are serialized to form one line of image signal. For this reason, it is necessary that the effective pixels of each sensor chip 1 to 5 are arranged continuously in the reading direction, and the black reference pixels of each of the second and subsequent sensor chips 2 to 5 are as shown in FIG. As shown in the figure, the sensor chip is placed so as to overlap the effective pixel of the previous sensor chip. Then, by driving each sensor chip 1 to 5 at the timing when the operation of one sensor chip ends and the effective pixel signal of the next sensor chip is output, the output is output from each sensor chip 1 to 5 as shown in FIG. The effective pixel signals thus obtained are continuous in time, and one line of image signals can be obtained by simply selectively outputting the effective pixel signals (those with dark time correction) output from the sensor chips 1 to 5. Obtainable.

In the contact type image sensor as described above, each sensor chip 1 to 5 is sequentially driven by a driver (not shown) provided corresponding to each sensor chip 1 to 5, or each sensor chip 1 to 5 is driven by a driver (not shown) provided corresponding to each sensor chip 1 to 5. If the driving timing is set to the timing described above, the operation of the driver will be as shown in FIG. Note that the driver A in FIG. 7 is connected to the sensor chip 1,
Driver B connects to sensor chip 2, driver C connects to sensor chip 3, driver D connects to sensor chip 4, driver E
correspond to the sensor chip 5, respectively.

As can be seen from FIG. 7, two drivers are operating during the period in which the two sensor chips overlap. Therefore, the current consumption of the entire contact type image sensor changes as shown in FIG. Naturally, when the two drivers are operating, the current consumption is large, and there is a possibility that the power supply to the sensor chips 1 to 5 becomes unstable during this period. When the voltage of the power supply changes in the sensor chips 1 to 1, the level of the output signal also changes.

Figure 8 is a diagram showing the measurement results of changes in current consumption in a conventional contact type image sensor. It is.

Here, as mentioned above, the power supply becomes unstable in the area where the two sensor chips overlap, that is, in the area of the black reference pixel on one sensor chip, so the level of the black reference signal of the sensor chip is is different from the actual level. Therefore, the effective pixel signals of the sensor chip are corrected in the dark using this erroneous black reference signal, resulting in all signals having erroneous levels. This results in "density unevenness" for each sensor chip 1 to 5.

In addition, in the other sensor chip, the area where the two sensor chips overlap is part of the effective pixel area, and does not affect the entire area of one chip as described above. However, since the signal level only in this region is at an incorrect level, "white stripes" or "black stripes J" appear.

(Problem to be solved by the invention) As described above, in the conventional contact type image sensor, there are periods when only one sensor chip is driven and periods when two sensor chips are driven, and both consume current. There will be a difference. As a result, the voltage of the power supply supplied to the sensor chip changes, causing problems such as "uneven density", "white stripes", "black stripes", etc., resulting in deterioration of image quality.

The present invention has been made in consideration of these circumstances, and its purpose is to stably supply power to each sensor chip and thereby generate high-quality image signals. The purpose of this invention is to provide a contact type image sensor that can be used.

[Structure of the Invention (Means for Solving the Problems)] The present invention provides a drive means for bringing a plurality of drive means respectively corresponding to a plurality of sensor chips arranged in a staggered manner into an operating state at the same time, for example, A predetermined combination including at least those corresponding to sensor chips in different rows is selected so that a predetermined number of two or more operating states are always maintained.

(Function) By taking such measures, the same number of drivers are always in operation, and power consumption becomes constant.

Therefore, it is possible to prevent the power supply from becoming unstable.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a contact type image sensor according to this embodiment. Note that the same parts as in FIG. 4 are given the same reference numerals, and detailed explanation thereof will be omitted.

In the figure, 11, 12, 13, and 14.15 are drivers that drive the sensor chips 1, 2, 3, and 4.5, respectively. These drivers 11 to 15 and sensor chip 1
-5 operate by receiving power supply from the same power source.

16 is a control circuit. The control circuit 16 controls each of the drivers 11 to 15 at timings to be described later, based on clock signals and control signals given from, for example, the main body of an image reading apparatus to which the present contact image sensor is applied.

An image processing circuit 17 performs various processes (dark correction, serialization, etc.) on the signals output from each of the sensor chips 1 to 5 to generate an image signal.

Next, the operation of the contact type image sensor configured as above will be explained with reference to the operation time chart shown in FIG. First, when the control circuit 16 is instructed to start reading by a control signal, it allows the driver 14 and the driver 15 to operate. In response to this, the drivers 14.15 respectively drive the sensor chips 45, but here the sensor chips 4.5 do not hold any charge and their outputs are in a no-signal state.

In this state, the line start signal LST among the control signals
When input, sensor chips 1 to 5 perform photoelectric conversion using this line start signal LST as a trigger. Thereafter, the control circuit 16 allows the driver 11 to operate after a short period of time (time T1 in FIG. 2). In response to this, the driver 11 drives the sensor chip 1 to sequentially output the signals obtained by each photoelectric conversion element of the sensor chip 1.

At this time, the operation of the driver 11 is permitted at time T1, and at the same time, the operation of the driver 15 is stopped. Note that the operation of the driver 14 is continued.

Subsequently, the control circuit 16 controls the driver 12 when a predetermined time t (the time required to output a signal obtained by the effective pixel area) has elapsed from the time T1 at which the driver 1 is allowed to operate.
(point 12 in Figure 2). In response to this, the driver 12 drives the sensor chip 2 to sequentially output the signals obtained by each photoelectric conversion element of the sensor chip 2. At this time, at the time point 12, the operation of the driver 12 is permitted, and at the same time, the operation of the driver 14 is stopped.

Note that the operation of the driver 11 is continued.

Thereafter, similarly, every time t passes (T3 in FIG. 2).
T4. At each time point T5), the operations of the drivers 13, 14, and 15 are sequentially permitted. Accordingly, drivers 13 and 14
．． Reference numeral 15 sequentially drives the sensor chips 3 and 4.5, respectively, and sequentially outputs signals obtained by each photoelectric conversion element in the sensor chips 3 and 4.5. At this time, the control circuit 16
At time 3, the operation of the driver 13 is allowed, and at the same time, the operation of the driver 11 is stopped, and the operation of the driver 12 is allowed to continue. Further, at the time point 14, the operation of the driver 14 is permitted, and at the same time, the operation of the driver 12 is stopped, and the operation of the driver 13 is allowed to continue. Further, at the time point 15, the operation of the driver 15 is permitted, and at the same time,
The operation of the driver 13 is stopped, and the operation of the driver 14 is continued.

In this way, each driver 11 to 15 drives the corresponding sensor chip until the operation timing of the next sensor chip starts, and the sensor chip whose operation timing is two times later starts operating. stop at the same time. That is, even after one sensor chip finishes outputting all signals, it is driven as a dummy until the next sensor chip starts operating. Therefore, as can be seen from FIG. 2, two drivers are always operating and two sensor chips are being driven, and the current consumption is almost constant. As a result, power supply is stably performed, and the output signal level of each sensor chip 1 to 5 does not change due to a voltage change.

Note that when the sensor chips 1 to 5 are driven as dummies, no charge is accumulated, so the output is no signal, and there is no similar problem.

By the way, since sensor chips 1 to 5 are arranged in a staggered manner, sensor chips 1, 3.5 and sensor chips 2.4
(Hereinafter, the row with sensor chips 13 and 5 will be referred to as an odd numbered row, and the row with sensor chips 2.4 will be referred to as an even numbered row). Here, the distance between odd numbered columns and even numbered columns should be as short as possible. For this reason, the photoelectric conversion element on the sensor chip is usually not placed in the center of the sensor chip, but is offset as shown in FIG. In other words, sensor chips 1 and 3.5 in odd rows and sensor chip 2 in even rows.
．． 4 is designed to have the same performance, but there is a difference in current consumption due to manufacturing variations.

This difference in current consumption is shown as ΔI in FIGS. 7 and 8. Therefore, the odd row sensor chips 1, 3.5
There is a possibility that the supply voltage may be different between the sensor chips 2 and 4 in the even rows.

However, in this embodiment, the sensor chips 1, 3.5 in the odd-numbered rows and the sensor chips 1, 3.5 in the odd-numbered rows are always driven at the same time, or the sensor chips in the odd-numbered rows and the sensor chips in the even-numbered rows. Even row sensor chip 2.4
It is possible to stabilize the current consumption by compensating for the difference in current consumption.

FIG. 3 is a diagram showing measurement results of changes in current consumption in the contact type image sensor according to this embodiment. As can be seen from this figure, the current consumption does not change significantly and is stable, and the voltage supplied to the sensor chips 1 to 5 is also stable. Therefore, the output level from the sensor chips 1 to 5 does not change due to a change in the supply voltage, and a high-quality image signal without "uneven density,""whitestripes," or "black stripes" can be obtained.

Note that the present invention is not limited to the above embodiments. For example, in the above embodiment, two drivers are always in operation, but three or more drivers may be operated. Further, in the above embodiment, the sensor chips in the odd-numbered rows and the sensor chips in the even-numbered rows are driven at the same time, but the combination of sensor chips to be driven simultaneously may be any desired combination. Furthermore, in the above example, 5
Although a contact type image sensor configured with one sensor chip is illustrated, it is of course applicable to an image sensor having a different number of sensor chips.

In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] According to the present invention, the driving means for activating the plurality of driving means corresponding to the plurality of sensor chips arranged in a staggered manner at the same time, for example, are applied to at least the sensor chips in different rows. By selecting a predetermined combination containing corresponding sensors, a predetermined number of two or more operating states are always maintained, so power is stably supplied to each sensor chip, and as a result, high-quality image signals can be obtained. This is a close-contact image sensor that can generate images.

[Brief explanation of the drawing]

1 to 3 are diagrams explaining a contact type image sensor according to an embodiment of the present invention, in which FIG. 1 is a block diagram showing the configuration, FIG. 2 is an operation time chart, and FIG. 3 is a consumption diagram. A diagram showing the measurement results of the current transition, and FIGS. 4 to 8 are diagrams each explaining the prior art. 3゜4゜5...sensor chip, 11゜゜] 3゜14゜5... driver, 16... control circuit, 7... image processing circuit.

Claims (2)

[Claims] (1) A plurality of sensor chips configured by one-dimensionally arranging a large number of photoelectric conversion elements arranged in a staggered pattern, each of which is provided corresponding to each of the plurality of sensor chips and operates sequentially in a predetermined order. A close-contact type image sensor comprising a plurality of driving means for driving corresponding sensor chips, the contact-type image sensor comprising: a control means for always keeping the driving means in two or more predetermined operating states. image sensor. (2) The close contact according to claim (1), wherein the control means selects the driving means to be activated at the same time in a predetermined combination including at least driving means corresponding to sensor chips in different rows. Shape image sensor.