JP2000201250A - Moving object image pickup method and line scanner device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively provide necessarily sufficient picture quality whose operation distance of a picked up image is short with short scanning by arranging a MOS-type two-dimensional sensor by making it face the image pickup face of a moving object and selectively scanning the image element of the sensor and using the two-dimensional sensor as a line sensor against the motion of the moving object. SOLUTION: The gate signal of a MOS switch 53 in a first row is outputted from a vertical scanning circuit 56. The gate signals of MOS switches 55 are outputted from a horizontal scanning circuit 57 in order from a first column, a second column and a third column. The vertical scanning circuit 56 outputs gate signals of a second row, and the horizontal scanning circuit 57 outputs the signals of the respective columns in the same way as for the first row. This is repeated in the third row and is repeated by going back to the first row again. Reading in a charge transfer part is executed in such way and photodiodes are sequentially read. The signals of the respective image elements are read and an image can be read as a time sequential signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a traveling object imaging method and a line scanner apparatus for imaging a traveling object such as a printed matter, and more particularly, to a low cost, a short working distance of imaging, and a necessary and sufficient image quality for a short scanning time. And a line scanner device.

[0002]

2. Description of the Related Art There are two types of image sensors, a two-dimensional sensor and a one-dimensional sensor, as viewed from the image forming system.
The former is also called an area sensor, etc.
Two-dimensional image information can be extracted. On the other hand, the latter is also called a line sensor or a linear image sensor, and performs multiple exposures by mechanically moving either the subject or the image sensor, and performs two-dimensional exposure by combining line information. I try to get image information.

In view of the positional relationship with respect to the subject at the time of imaging, there are two types of sensors: a contact sensor and a lens reduction sensor. The former is also called a contact sensor, a contact imager, a contact image sensor, or the like, and captures images at the same magnification by bringing an image pickup element into close contact with a subject or inserting a self-fox lens or the like between them. On the other hand, in the latter, an image is optically reduced by using a lens or the like, so that a certain working distance (hereinafter referred to as an imaging working distance) is required.

Here, a line sensor is used to continuously image a running object such as a printed matter. On the other hand, the lens reduction type line sensor camera has a feature that high-speed scanning and high-resolution input are possible.

[0005]

However, the lens-reduced line sensor camera requires an imaging working distance corresponding to the object to be imaged, and thus has a problem that the installation limit is large. It is possible to arrange a large number of lens reduction type line sensor cameras in parallel to reduce the photographing range per one and to reduce the imaging working distance. However,
Since it is more expensive than a general area sensor camera, there is a cost problem.

The contact sensor is a high resolution type of 200 to 600 DPI (dot per inch) generally used in a flatbed scanner, a facsimile, a copying machine, and a low resolution type used in a whiteboard copying machine. However, since both aim to image a stationary object by mechanical scanning on the sensor side, the scanning speed is absolutely insufficient to image a running object such as a printed matter. In both the high-resolution type and the low-resolution type, since the photodiode used for imaging is large, the discharge time is long and the operation speed tends to be slow.
For this reason, if the camera is forcibly operated quickly, an image may be missed. Therefore, the contact sensor has a signal-to-noise ratio (SN).
From the viewpoint of R (signal noise retio) and the like, it is insufficient for inspection and measurement applications.

SUMMARY OF THE INVENTION An object of the present invention is to provide a niece capable of obtaining a necessary and sufficient image quality in a short scan time at a low cost, a short working distance of imaging.

[0008]

A moving object imaging method according to a first aspect of the present invention is directed to a moving object imaging method for imaging a running object such as a printed matter. By arranging a two-dimensional sensor and selectively scanning pixels of the two-dimensional sensor, by using as a line sensor for traveling of the traveling object,
This has solved the above-mentioned problem.

[0009] Further, in the moving object imaging method, by arranging a plurality of the two-dimensional sensors in parallel, it is possible to obtain a necessary resolution and an imaging range using a two-dimensional sensor mass-produced at low cost. And cost can be reduced.

Further, in the running object imaging method, color filters of different colors are attached to different rows in a direction perpendicular to the running direction of the running object, so that the first
A color image or a multispectral image can be obtained while applying the invention.

Next, a line scanner device according to a second invention of the present application is a line scanner device for picking up an image of a running object such as a printed matter, which is a MOS type two-dimensional sensor arranged to face an imaging surface of the running object. Means for selectively scanning pixels of the two-dimensional sensor to use the two-dimensional sensor as a line sensor for the traveling of the traveling object.

Hereinafter, the operation of the present invention will be briefly described.

An ordinary CCD (charge coupled device):
(Charge-coupled device) area sensor camera, progressive scanning (ra
ster scan / sequential scan). On the other hand, a MOS (metal oxide semiconductor: metal-oxide film-semiconductor) area sensor camera can perform arbitrary scanning (ransom scan / random access), has a high operation speed, and has a required and sufficient image quality and a short scanning time. Can be obtained at Also, MOS area sensor cameras are mass-produced and low cost. Furthermore, because of such a low cost, a plurality of units can be arranged side by side as in the embodiment described later, and in this case, the imaging working distance can be shortened.

In the present invention, the area sensor is used as a line sensor by utilizing such arbitrary scanning. Therefore, the working distance of imaging is short at low cost, and necessary and sufficient image quality can be obtained in a short scan time.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

In any of the embodiments of the present invention, the present invention is applied, and the embodiment shown in FIG.
The MOS area sensor shown in FIG. The first embodiment uses one MOS area sensor. In the second embodiment, as shown in FIG. 10, a plurality of MOS area sensors are juxtaposed in a direction perpendicular to the traveling direction of the traveling object. In the third embodiment, as shown in FIG. 13, color filters of three different colors are attached to different columns in a direction orthogonal to the traveling direction of the traveling object to obtain a color image or a multispectral image.

In order to explain the operation of these embodiments,
First, the difference between the area sensor and the line sensor will be described, and then the difference between the contact sensor and the lens reduction sensor will be described.
After that, the difference between the CCD image sensor and the MOS image sensor will be described, and then the first embodiment using the MOS area sensor will be described. Further, a second embodiment will be described, and a third embodiment will be described in which a color filter and a spectroscope are mounted on the front surface of the MOS area sensor to form a color sensor.

FIG. 1 is a perspective view for explaining the operation of the lens reduction type area sensor.

In FIG. 1, a picture 1a or 1b on the right side of the running paper 1 forms an image through a lens 10 on an area sensor 12, in which pixel sensors are two-dimensionally arranged, as indicated by broken lines. Since the paper 1 is in the printing process, the arrow 3
You are traveling in the direction of. Also, the paper surface 1 is a pattern 1a or 1b.
Are printed, and these are the inspection targets.

The area sensor 12 can capture an image by one image pickup. However, since it takes time to capture an image, it is necessary to strike a strobe or the like to obtain a still image of the running object. Further, at least the imaging range of the object to be imaged needs to be parallel to the area sensor and flat. Furthermore, it is necessary to uniformly illuminate the imaging range, which is not easy.

FIG. 2 is a perspective view for explaining the operation of the lens reduction type line sensor.

The illustrated line sensor 14 can capture only one scanning line of image and signal in one image pickup. Therefore, it is necessary to form a two-dimensional image by performing sub-scanning (horizontal synchronization) in synchronization with the traveling of the traveling object as indicated by the arrow 3. When obtaining a two-dimensional image in this way, only the imaging range on the scanning line needs to be parallel to the line sensor 14 and flat. Further, the imaging range to be uniformly illuminated is substantially linear, and flat illumination can be performed relatively easily using a linear light source.

FIG. 3 is a perspective view for explaining the operation of the contact type line sensor.

The contact line sensor 20 shown in FIG. 3 forms an image at the actual size unlike the area sensor shown in FIG. 1 and the line sensor shown in FIG. Contact type line sensor 20
Then, as shown in FIG. 4, between the paper surface 1 and the image sensor 22,
The SELFOC lens 24 and the like are provided, and are arranged at an interval of several millimeters from the end face of the SELFOC lens 24 to the paper surface 1. The short interval becomes the imaging working distance. For this reason, the imaging working distance unlike a lens reduction type sensor is not required, and the degree of freedom of sensor installation is high. In the contact type line sensor, the resolution is determined by the physical arrangement interval of the sensor of each pixel.

Conventionally, in a printed matter inspection apparatus, a contact line sensor having photodiodes arranged linearly has been used. In this case, there is a limit in making the photodiode element small, and therefore, the resolution cannot be made smaller than several millimeters. Currently available off-the-shelf line sensors have a resolution of about 200 to 600 DPI (dots per inch) and a length of an imaging range of about 200 mm for facsimile and the like. Or 30 for whiteboard
Some are about DPI. For this reason, there is no printer that satisfies all conditions such as scanning speed, resolution, and subject width when used for inspection of printed matter.

Next, the difference between the CCD image sensor and the MOS image sensor will be described with reference to FIGS.

FIG. 5 is a block diagram showing a functional configuration of an image sensor for one pixel.

As shown in the figure, the functional configuration of the image pickup device (image sensor) is the same as that of the CCD image sensor or MOS image sensor,
And a charge storage unit 32, and a charge transfer unit 34.

First, the photoelectric conversion section 30 uses a photoelectric conversion element. For example, photoelectric conversion is performed using a two-terminal element called a photodiode. In a photodiode, when a bias voltage is applied, a current proportional to the amount of received light flows, and this is used to perform photoelectric conversion.

Next, the charge storage section 32 uses a charge storage element, and performs charge storage using a capacitor, that is, a so-called capacitor. This capacitor accumulates electric charges according to the output current of the photodiode and the exposure time.

Here, an equivalent circuit of the photoelectric conversion and the charge accumulation is as shown in FIG. Reference numeral 36 is equivalent to a photodiode for photoelectric conversion, and reference numeral 38 is equivalent to a capacitor for charge storage. Terminal Out
A voltage proportional to the amount of received light is output from between put and the terminal + 5V.

After the photoelectric conversion and charge accumulation, the charge transfer section 34 performs charge transfer, that is, charge reading. In this charge transfer, charges of photoelectric conversion elements and charge storage elements arranged in a plane or a line are read out as a time-series signal.

FIG. 7 is a schematic view of a CCD type line sensor.

In this figure, a photodiode 40 and a capacitor 42 are arranged for each pixel, and an analog shift register 44 is provided for these.
The reading in the charge transfer section 34 is performed by sequential transfer (bucket relay) of charges in the CCD type, for example, as shown in FIG. In this figure, charges are bucket-relayed through an analog shift register according to a transfer clock. In addition, a two-dimensional sensor requires both horizontal scanning and vertical scanning.

FIG. 8 is a schematic diagram of a MOS type line sensor.

In this figure, in addition to a photodiode 40 and a capacitor 42, a MOS switch 48 is arranged for each pixel, and a switch switching shift register 46 is provided for these. The above-described reading in the charge transfer unit 34, that is, reading as a time-series signal, is performed by switching with a MOS switch 48 in the MOS type. In this figure, for charge transfer, MOS
The switch 48 is sequentially opened and closed. For the sequential opening and closing,
In this example, the gate pulse train is generated by sequentially shifting the pulses in the switch switching shift register 46 in accordance with the transfer clock. If the scanning portion by the switch switching shift register 46 can be arbitrarily selected, the electric charge at an arbitrary position can be taken out.

FIG. 9 is a schematic diagram of a two-dimensional MOS sensor.

In the example of this figure, to simplify the explanation,
The case where the pixel sensors are arranged in four rows and three columns is illustrated. In this figure, a photodiode 5 is provided for each pixel.
0 and a capacitor 51, a MOS switch 53
Are arranged, and a MOS switch 5 is provided for each column.
5 are provided. The MOS switch 53 is controlled by a vertical scanning circuit 56, and the MOS switch 55 is controlled by a horizontal scanning circuit 57.

The operation of the two-dimensional MOS sensor will be described. First, the gate signal of the MOS switch 53 in the first row is output from the vertical scanning circuit 56. Next, the gate signal of the MOS switch 55 is output from the horizontal scanning circuit 57 in the order of the first column, the second column, and the third column. Thereafter, a gate signal of the second row is output from the vertical scanning circuit 56, and the horizontal scanning circuit 57 outputs a signal of each column similarly to the first row. After repeating this for the third row, the procedure returns to the first row and repeats. In this manner, the above-described reading in the charge transfer unit 34 is performed, the photodiode is sequentially selected, the signal of each pixel is read, and the image can be read as a time-series signal.

Here, for example, if the vertical scanning is stopped and only the second row is always enabled and only the horizontal scanning is performed, the same function as the line sensor can be achieved.
In the first to third embodiments, the area sensor is used as a line sensor in this manner. Here, if the scanning range is limited, a captured image of only a partial rectangular area can be obtained. Further, it is possible to perform reading in a completely arbitrary order.

Currently available small and inexpensive MOS area sensors have a size of about 128 × 128 pixels to 256 × 256.
It has about the number of pixels. Mass-produced sensors are inexpensive. When obtaining the required imaging range and resolution,
It is advantageous in terms of cost to arrange a plurality of such inexpensive MOS area sensors in a direction perpendicular to the traveling direction of the traveling object. In the second embodiment, a plurality of MOS area sensors are juxtaposed as described above.

For example, with a 128 × 128 pixel camera,
1m paper width is imaged and 0.5mm / PE
A case of obtaining a resolution of L (picture element) will be considered as an example. In this case, since 2,000 pixels are required, 5
If 20 units are juxtaposed at 0 mm intervals, a resolution of 0.5 mm / PEL can be obtained. In this case, since the individual MOS area sensors do not have a large number of pixels, it is not necessary to pay much attention to lens distortion, etc. be able to.

For example, FIG. 10 shows an example in which a plurality of MOS area sensors are juxtaposed. In this example, a plurality of MOS area sensors 60 are juxtaposed between linear light sources 64 provided in parallel. FIG. 11 shows the MOS area sensor 60
It is the perspective view seen from the side. On the paper surface 1 side of the MOS area sensor 60, a lens 62 facing the paper surface 1 is provided. FIG. 12 is a side view of the MOS area sensor 60. As shown in FIG. 12, two linear light sources 64
, The MOS area sensor 60 captures an image of the picture on the paper 1 through the lens 62.

Finally, as shown in FIG. 13, as a third embodiment, color filters of different colors are attached to different rows in a direction orthogonal to the running direction of the object to be picked up, so that a color image or a multispectral image is obtained. A description will be given of a moving object imaging method for obtaining an image.

This figure shows a top view of a MOS area sensor to which the RGB color filters of the third embodiment are attached. In the figure, the pixel sensors E are arranged vertically and horizontally. In this embodiment, an RGB (red-green-blue) color filter is used. That is, a three-line color line sensor is formed by using only three of the 128 lines of the MOS area sensor.

In this figure, reference symbol R denotes a red filter, and one line of the pixel sensor E indicated by reference symbol RL is used for red. The symbol G is a green filter, and one line of the pixel sensor E indicated by the symbol GL is used for green. Reference numeral B denotes a blue filter, and one line of the pixel sensor E indicated by reference BL is used for blue.

As described above, according to the first to third embodiments, the present invention can be effectively applied. Therefore, the working distance of imaging is short at low cost, and necessary and sufficient image quality can be obtained in a short scan time.

[0048]

According to the present invention, it is possible to obtain a necessary and sufficient image quality in a short scan time at a low cost, a short working distance of imaging.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating an operation of a lens reduction type area sensor.

FIG. 2 is a perspective view illustrating the operation of a lens reduction type line sensor.

FIG. 3 is a perspective view illustrating the operation of a contact type line sensor.

FIG. 4 is a side view illustrating the configuration of a contact type line sensor.

FIG. 5 is a block diagram illustrating a functional configuration of an image sensor for one pixel.

FIG. 6 is an equivalent circuit diagram of photoelectric conversion and charge accumulation.

FIG. 7 is a schematic view of a CCD type line sensor.

FIG. 8 is a schematic diagram of a MOS type line sensor.

FIG. 9 is a schematic diagram of a two-dimensional MOS sensor used in the first to third embodiments to which the present invention is applied.

FIG. 10 is a view showing the second embodiment in which a plurality of MOS area sensors are juxtaposed.
Embodiment perspective view

FIG. 11 is a perspective view of the MOS area sensor viewed from the paper surface side in the embodiment.

FIG. 12 is a side view of the side view of the MOS area sensor.

FIG. 13 is a top view of a MOS area sensor to which the RGB color filters of the third embodiment are attached.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Paper surface 1a, 1b ... Picture 3 ... Paper surface running direction 10, 62 ... Lens 12 ... Area sensor 14 ... Line sensor 20 ... Contact line sensor 22 ... Image sensor 24 ... Selfoc lens 30 ... Photoelectric conversion part 32 ... Charge storage part 34 ... Charge transfer unit 36 ... Equivalent circuit of photoelectric conversion photodiode 38 ... Equivalent circuit of charge storage capacitor 40,50 ... Photodiode 42,51 ... Capacitor 44 ... Analog shift register 48,53,55 ... MOS switch 46: switch switching shift register 56: vertical scanning circuit 57: horizontal scanning circuit 60: MOS area sensor 64: linear light source R: red filter G: green filter B: blue filter

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hideto Sakata 1-1-1, Ichigaya-Kaga-cho, Shinjuku-ku, Tokyo F-term within Dai Nippon Printing Co., Ltd. 5C072 AA01 BA02 BA19 EA05 EA08 QA06 TA05 UA12 XA01

Claims (4)

[Claims] 1. A traveling object imaging method for imaging a traveling object such as a printed matter, wherein a MOS type two-dimensional sensor is arranged to face an imaging surface of the traveling object, and pixels of the two-dimensional sensor are selectively scanned. The moving object imaging method is used as a line sensor for the running of the moving object. 2. A moving object imaging method according to claim 1, wherein a plurality of said two-dimensional sensors are juxtaposed. 3. The running object imaging method according to claim 1, wherein the running object has different columns in a direction orthogonal to a running direction of the running object.
A moving object imaging method, wherein color filters of different colors are attached to obtain a color image or a multispectral image. 4. A line scanner device for imaging a running object such as a printed matter, a MOS type two-dimensional sensor arranged to face an imaging surface of the running object, and selectively scanning pixels of the two-dimensional sensor. A means for using as a line sensor for the traveling of the traveling object.