JPH09153988A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce deterioration in image brought by a change in the bright ness. SOLUTION: A read original irradiation light detection signal detected by a photo sensor 1(9) is amplified by a signal processing circuit 2, an offset voltage is adjusted and an electric signal equivalent to a timewise fluctuation in brightness on an original face caused by illumination of a ceiling light is obtained and fed to an arithmetic circuit 14. The arithmetic circuit 14 uses an output electric signal from the signal processing circuit 2 to conduct processing for differential arithmetic operation so as to eliminate the brightness fluctuation due to the ceiling light in an image signal from an one-dimensional image sensor 3. Thus, the image signal whose fluctuation in brightness of the ceiling light is considerably suppressed is extracted from the arithmetic circuit 14 and the resulting image signal is converted into a digital signal by an A-D converter 15 and the digital signal is outputted to a post-stage circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading device, and more particularly to an image reading device for reading characters or images and converting them into digital data.

[0002]

2. Description of the Related Art Among image reading devices, one widely known as an image scanner using a one-dimensional image sensor is one in which a manuscript surface is placed upside down on a box-shaped device, and the image sensor is placed below the image sensor. Scans and reads the original, a flatbed type, a handy type in which the user moves the device over the original to perform sub-scanning, and the original and the reading unit including the one-dimensional image sensor are separated from each other. It can be roughly divided into camera types.

Of these, the camera type image reading device is
You can read originals such as uneven books and vertically installed boards, compared with other image reading devices,
It is characterized in that there are few restrictions on the subject (reading document) such as size, orientation, and flatness.

Such a camera-type image reading device mainly uses a one-dimensional image sensor as an image-electrical signal conversion element, and combines this with a sub-scanning operation in a direction orthogonal to the longitudinal direction of the one-dimensional image sensor. Read the 3D image. Further, it is necessary that the document surface has a predetermined brightness corresponding to the sensitivity of the one-dimensional image sensor and the storage time. Lighting by general ceiling lights, such as users creating documents and using word processors, or using electronic blackboards for meetings with several people,
As an example of a camera-type image reading device that realizes reading, an image scanner (model number DS-3000) sold by Chinon Co., Ltd. and an image scanner sold by Casio Computer Co., Ltd. Photographs)) and so on.

FIG. 13 shows a basic configuration of the above-mentioned conventional camera type image reading apparatus. As shown in the figure, as a main mechanism related to image reading, a one-dimensional image sensor 3 for converting an image of a read original 7 into an electric signal, and an image of the read image is formed on a light receiving surface of the image sensor 3. It includes a lens 5 for scanning and a sub-scanning mechanism 4 for sequentially inputting images on the scanning line 8 on the scanning original 7. The camera type is characterized in that the sub-scanning mechanism 4 and the document surface of the read document 7 are separated from each other as compared with other types of image scanners.

As the sub-scanning mechanism 4, two methods are generally adopted. One is the lens that forms the image you want to read on the light receiving surface of the image sensor, and
A two-dimensional image sensor moves in parallel to perform sub-scanning. The other is equipped with a reflecting mirror between the read original and the lens to reach the one-dimensional image sensor, and the reflecting mirror is rotated to change the reflection angle. By doing so, sub-scanning is performed. Here, the sub-scanning mechanism 4 uses the latter reflecting mirror 6
2 shows a mechanism for sub-scanning the image formed on the one-dimensional image sensor 3 by utilizing the rotation of No. 1 by utilizing the change of the reflection angle.

The shorter the time for reading the document surface is, the more convenient for the user, and the more quickly the document can be read, which is convenient because it can be used for other image processing such as color correction and character recognition. One factor for reducing the read time is to shorten the read time per line read by the one-dimensional image sensor.

In an image sensor, an optical semiconductor such as a phototransistor or a photodiode, which generally corresponds to each pixel, is irradiated with light and accumulated as electric charge.
After the accumulated charge is transferred to the register, it is sequentially transferred to the adjacent register and transferred. If the reading time is shortened, the accumulation time for accumulating charges in the optical semiconductor may be insufficient. Therefore, the sensitivity of the optical semiconductor is improved, or the intensity of the irradiation light is increased to deal with the problem. As a method of improving the reading time by using a specific one-dimensional image sensor, increase the light irradiating the original surface and shorten the accumulation time as much as possible to shorten the reading time per line. it can.

[0009]

However, if the reading time is made shorter than a specific time, the influence of the ceiling light as external light appears as a stripe line in the main scanning direction in the read image data, which is a bad influence. give. That is, generally, in the room, the conventional image reading apparatus shown in FIG. 13 is illuminated by the ceiling lamp 23, and the document surface of the read document 7 also receives the light emitted from the ceiling lamp 23. , This ceiling light 23 is a commercial power supply frequency (50 Hz in eastern Japan, 60 H in western Japan) supplied by an electric power company.
In the case of a fluorescent lamp, the brightness changes at a frequency corresponding to this commercial power supply frequency (100 Hz in East Japan).

However, when the accumulation time corresponding to the reading time by the one-dimensional image sensor 3 is almost equal to the cycle corresponding to the commercial power supply frequency in the usage area (about 10 ms in eastern Japan), there is little adverse effect. , As the cycle becomes shorter than this, adverse effects will start to appear.

As an example, it is assumed that an image reading apparatus in which the reading time per line by the one-dimensional image sensor 3 is 1.4 ms and the storage time is also 1.4 ms is used in an area of eastern Japan. As described above, in eastern Japan, the ceiling lamp 23 causes the brightness of the document surface to repeat bright and dark in units of 10 ms, so that the image sensor 3 reads about 7 lines in 10 ms. Therefore, the ceiling light 2
Brightness and darkness due to the change in brightness of No. 3 are converted into electric signals in units of about 7 lines, and appear as dark and light stripe lines in a cycle of about 7 lines, which adversely affects the read image quality.

The present invention has been made in view of the above points,
An object of the present invention is to provide a camera-type image reading apparatus using a one-dimensional image sensor, which can reduce image quality deterioration due to temporal brightness change on the original surface.

[0013]

In order to achieve the above object, the present invention uses a sub-scanning mechanism to scan incident light from a read original to a one-dimensional image sensor in the sub-scanning direction to scan a one-dimensional image. In an image reading device that outputs a two-dimensional image signal from the sensor, an optical sensor that directly or indirectly detects a change in the brightness of external light applied to the document surface of the read document and converts the change into an electrical signal. It is configured to include an arithmetic means for receiving the output signal of the optical sensor and the image signal from the one-dimensional image sensor as input signals and canceling and removing the change component of the brightness of the external light from the image signal and outputting the cancelled component. .

Here, the above-mentioned computing means delays the periodic signal component of the output signal of the optical sensor in accordance with the storage time for one line of the one-dimensional image sensor, and the one-dimensional image sensor. From the image signal and the output signal of the delay circuit to cancel and remove the change component of the brightness of the external light from the image signal and output it, or after sampling the output signal of the optical sensor, First sample and hold means controlled at a holding timing during the period in which the image signals accumulated by the two-dimensional image sensor are sequentially transferred, the image signal from the one-dimensional image sensor and the output signal of the first sample and hold means And an arithmetic circuit for calculating and canceling the change component of the brightness of the outside light from the image signal and outputting the cancelled component.

Further, in the present invention, the first to the light sensors are used.
The signal from the photosensor is sampled during a certain one-line period during which the one-dimensional image sensor photoelectrically converts incident light and accumulates charges in the signal path up to the sample-holding means, and the corresponding line is accumulated. A delay corresponding to the delay by the delay circuit may be provided by including the second sample hold means controlled by the timing of holding until the result is transferred to the register and output as an image signal is started. Here, the second sample-hold means is provided with a storage circuit that stores the output signal of the photosensor in a capacitor corresponding to the storage amount accumulated as electric charge according to the amount of light at the time of storage in the one-dimensional image sensor. May be.

Further, according to the present invention, the calculation means can reduce the influence of external light received on the original surface in the main scanning direction in the middle of the signal path from the optical sensor to the first sample hold means. Correspondingly, there is provided a main scanning direction correction circuit for inclining the output signal from the optical sensor sample-held by the first sample-hold means,
It is desirable that the influence of the external light applied to the document surface can be removed even if there is a deviation depending on the reading position in the main scanning direction.

Further, according to the present invention, a light source for irradiating the document surface of the read document and a change in the brightness of the light projected on the document surface of the read document are directly or indirectly detected and converted into an electric signal. An optical sensor for conversion and a dimming circuit for controlling the brightness of the light emitted from the light source according to the output signal of the optical sensor so that the brightness of the light received from the document surface by the optical sensor becomes constant. It is characterized by

The optical sensor used in the present invention is provided between the reflecting mirror constituting the sub-scanning mechanism and the one-dimensional image sensor, and the rotation of the reflecting mirror changes the image formed on the one-dimensional image sensor. In accordance with the above, the configuration may be such that the portion on the document surface that receives light changes. Further, it is desirable to provide a green filter on the light receiving surface of the optical sensor in that the wavelengths of the spectral sensitivities of the one-dimensional image sensor and the optical sensor can be matched.

According to the present invention, the light received by the one-dimensional image sensor is affected by the external light, whose brightness changes with the passage of time, on the surface of the original, and the output image signal of the one-dimensional image sensor is affected. Even if the signal component due to the external light is superimposed, the external light reflected from the document surface is received by the optical sensor and converted into an electric signal, and the arithmetic means calculates the image signal based on the electric signal. Due to
It is possible to significantly reduce or remove a signal component due to external light in the image signal.

Further, according to the present invention, the brightness of the light source is adjusted so that the brightness of the light emitted from the light source onto the document surface is constant according to the output signal of the optical sensor. Therefore, the signal component due to the external light in the image signal can be significantly reduced or removed.

[0021]

Next, an embodiment of the present invention will be described. FIG. 1 shows a first image reading apparatus according to the present invention.
The block diagram regarding the mechanism of embodiment of FIG. As shown in FIG. 1, the mechanism of the image reading apparatus of this embodiment includes a one-dimensional image sensor 3 for converting an image of a document into an electric signal, a sub-scanning mechanism 4 for sequentially inputting partial images in a desired direction, A lens 5 for forming an image of a read image on the read document 7 on the light receiving surface of the one-dimensional image sensor 3 and the optical sensor 1 which is a feature of the present invention, and a signal from the optical sensor 1 is further provided. It has a signal processing circuit 2 for processing.

There are several methods for the sub-scanning mechanism 4 which is one of the components of this image reading apparatus. That is, as shown in FIG. 1, a reflecting mirror 6 for reflecting a partial image of a read image in a desired direction and a rotating mechanism 8 for rotating the reflecting mirror 6 are provided, and the reflecting mirror 6 is rotated to obtain a desired image. There is a method of performing sub-scanning by projecting a partial image on the one-dimensional image sensor 3. Further, a method of performing sub-scanning by sequentially projecting partial images in a desired direction by moving the reflecting mirror 6 in parallel instead of rotating it, or there is no reflecting mirror 6 and instead an image is formed by a lens. There is a method of performing sub-scanning by sequentially capturing partial images by moving the existing one-dimensional image sensor on the imaging plane.

The optical sensor 1 is arranged so as to be able to receive the reflected light from the original surface of the read original 7, and the brightness of the external light radiated to the original surface in any of the above sub-scanning methods. The change in the height can be detected directly. Further, a signal processing circuit 2 and an arithmetic circuit (not shown) described later.
It is possible to achieve the object of the present invention by performing signal processing according to.

That is, the optical sensor 1 is prepared as a light receiving element separately from the one-dimensional image sensor 3 and directly detects a change in brightness from the original surface. The signal received by the optical sensor 1 is a mixture of the brightness of a plurality of pixels, and is reflected from the document surface of the read document 7 without being affected by the fine pattern or characters of the read document 7. The change in brightness corresponding to the passage of time is detected, and the detection signal is input to the signal processing circuit 2 described later and signal processed.

FIG. 2 shows a second image reading apparatus according to the present invention.
The block diagram regarding the mechanism of embodiment of FIG. In the figure, the same components as those of FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. The second embodiment is characterized in that the optical sensor 9 is attached between the one-dimensional image sensor 3 and the reflecting mirror 6 for the sub-scanning, and particularly, is attached to the side of the lens 5. The optical sensor 9 can receive the light on the document surface of the read document 7 through the sub-scanning reflecting mirror 6.

As a result, when the reflecting mirror 6 is rotated in accordance with the operation of the sub-scanning mechanism 4 and the reading line 8 portion on the original surface read by the one-dimensional image sensor 3 changes in the sub-scanning direction one after another, this change occurs. Similarly, the optical sensor 9 receives light of a plurality of pixels in a range 10 centered on the reading line 8 read by the one-dimensional image sensor 3 and corresponds to the elapsed time of the brightness reflected from the original surface of the read original 7. Detect changes indirectly. That is, in this embodiment, the range 10 on the original surface received by the optical sensor 9 also changes in the sub-scanning direction as the reading line 8 being read by the one-dimensional image sensor 3 moves, whereby the ceiling in the sub-scanning direction is changed. It is possible to deal with the intensity of the influence of the light.

Next, the image processing section in the image reading apparatus according to the present invention will be described. This image processing unit is
The processing circuit for digitally converting the image signal obtained by the three-dimensional image sensor 3 constitutes the image reading apparatus of the present invention together with the mechanical section shown in FIGS. FIG. 3 is a block diagram showing the basic configuration of this image processing unit. Here, the one-dimensional image sensor 3 and the optical sensor 1 (or 9), which are the main parts of the mechanical section of FIGS. 1 and 2, are represented symbolically for drawing.

As shown in FIG. 3, the image processing unit for processing the image signal from the one-dimensional image sensor 3 receives a signal from the one-dimensional image sensor 3 and a pre-processing circuit 13 for adjusting the offset voltage and the gain. , And optical sensor 1
It is composed of an arithmetic circuit 14 having a function of arithmetically operating the signal processed from (9), and an A / D converter 15 for converting an output from the arithmetic circuit 14 into a digital signal.

In this image processing unit, the optical sensor 1
The read original irradiation light detection signal detected in (9) is amplified by the signal processing circuit 2, the offset voltage is adjusted, and an electric signal corresponding to the temporal brightness variation on the original surface due to the ceiling lamp irradiation. And is supplied to the arithmetic circuit 14. The arithmetic circuit 14 uses the output electric signal of the signal processing circuit 2 to perform a differential arithmetic process so as to remove the fluctuation of the brightness due to the ceiling light from the image signal from the one-dimensional image sensor 3. In this way, the arithmetic circuit 14
An image signal in which a variation in brightness due to a ceiling light is significantly suppressed is taken out from, is converted into a digital signal by the A / D converter 15, and is output to a subsequent circuit.

FIG. 4 shows a circuit system diagram of the first embodiment of the image processing section in the image reading apparatus according to the present invention.
3, the same components as those of FIG. 3 are denoted by the same reference numerals. In FIG. 4, the preprocessing circuit 13 is an operational amplifier 13
1, a variable resistor VR1, a fixed resistance, and a variable gain inverting amplifier circuit. The arithmetic circuit 14 is an operational amplifier 14
It is an adder circuit using 1. The pre-processing circuit 16 constitutes a signal processing circuit 2a (first embodiment of the signal processing circuit 2), and includes an operational amplifier 161, a variable resistor VR2,
This is a variable gain common-mode amplifier circuit composed of fixed resistors.

In this image processing unit, the image signal taken out from the one-dimensional image sensor 3 is supplied to the preprocessing circuit 13, and the offset voltage is adjusted and the inverting amplification is performed by using the operational amplifier 121. On the other hand, the detection signal from the optical sensor 1 or 9 is a signal corresponding to the brightness of the document surface which changes with the passage of time, and is supplied to the preprocessing circuit 16 (signal processing circuit 2a) to be in phase with the adjustment of the offset voltage. Is amplified. The arithmetic circuit 14 has the opposite phase of the image signal from the pre-processing circuit 13 and the pre-processing circuit 16 (the signal processing circuit 2
The signals corresponding to the brightness of the document surface, which changes with the passage of time from a), are in phase and are added by the operational amplifier 141 and output.

Here, the image signal from the one-dimensional image sensor 3 taken out from the pre-processing circuit 13 is superimposed on the signal corresponding to the image on the document surface with the signal component corresponding to the brightness of the document surface changing with the passage of time. Of these, the signal component corresponding to the brightness of the document surface, which changes with the passage of time, is canceled and removed by the arithmetic circuit 14 from the signal from the preprocessing circuit 16 (signal processing circuit 2a), and the image of the document surface is removed. Is taken out without being removed, is sent to the D / A converter 15, is converted into a digital image signal, and is output.

In the one-dimensional image sensor 3, an optical semiconductor such as a phototransistor or a photodiode corresponding to pixels arranged in a line is irradiated with light to perform photoelectric conversion and, as a charge, a predetermined period (length). Is called accumulation time). After that, the charges accumulated by the trigger signal given the reading time per line at a constant interval are transferred to the register corresponding to each pixel, sequentially transferred to the adjacent register in synchronization with the transfer clock signal and accumulated in each pixel. The charges that have been transferred are transferred one after another, and the signals corresponding to the pixel arrangement are output over time, so a signal that changes according to the brightness of each pixel that is received at the same time during the accumulation time is obtained as an image signal. To be Therefore, the image signal output from the one-dimensional image sensor 3 is the brightness received during the accumulation period corresponding to the immediately preceding line, not the brightness at the time when the image signal is output.

FIG. 5 is a circuit system diagram of the second embodiment of the image processing section for performing signal processing corresponding to the brightness received during the accumulation period corresponding to the immediately preceding line. 4, the same components as those of FIG. 4 are denoted by the same reference numerals, and the description thereof will be omitted. The embodiment shown in FIG. 5 is characterized in that a signal processing circuit 2b including a preprocessing circuit 17 and a delay circuit (phase circuit) 18 is provided in place of the signal processing circuit 2a of FIG.

The pre-processing circuit 17 is a variable gain inverting amplifier circuit including an operational amplifier 171, a variable resistor VR3, and a fixed resistor. The delay circuit 18 has a configuration using an operational amplifier 181, a capacitor 182, and a fixed resistor.
The input signal is directly input to the inverting input terminal of 81, and the input signal is input to the non-inverting input terminal after being delayed by an integrating circuit including a resistor and a capacitor 182. Therefore, although the delay circuit 18 also has an inverting function, it does not necessarily have to be an inverting function and may be designed so that the signal from the one-dimensional image sensor 3 and the signal from the optical sensor 1 have opposite phases. Good.

As a result, the detection signal from the optical sensor 1 or 9 corresponding to the brightness of the original surface which changes with the passage of time is supplied to the pre-processing circuit 17 for adjustment of the offset voltage and inversion amplification, and then delay. It is supplied to the circuit 18 to delay the phase of the periodic signal and then input to the arithmetic circuit 14.

In the present embodiment, the delay caused by the periodic signal input from the optical sensor 1 or 9 passing through the delay circuit 18 is matched with the delay of the accumulation time in the one-dimensional image sensor 3, It is possible to more effectively cancel the periodic signal that adversely affects the image when the differential of the signal is obtained by the arithmetic circuit 14 connected in the subsequent stage.

FIG. 6 is a block diagram of a third embodiment of the image processing section in the image reading apparatus according to the present invention.
5, the same components as those of FIG. 5 are denoted by the same reference numerals, and the description thereof will be omitted. In the circuit shown in FIG. 6, the optical sensor 1 or 9
The signal processing circuit 2 for processing the output signal from the sample holding timing generating circuit 19 and the sample holding timing generating circuit 19 are replaced with the delay circuit 18 of FIG.
It is characterized in that the signal processing circuit 2c is provided with a sample hold circuit 20 which performs a sample and hold operation according to the output signal of. An output drive signal of an image sensor drive signal generation circuit 21 that drives the image sensor 3 is input to the sample hold timing generation circuit 19.

In this embodiment, the arithmetic circuit 14 uses the image signal from the one-dimensional image sensor 3 and the optical sensor 1 or 9.
The image signal is not adversely affected when the differential with the signal from the. That is, when the brightness received by the optical sensor changes, the output detection signal level of the signal from the optical sensor 1 or 9 also changes correspondingly. However, the output signal from the one-dimensional image sensor 3 is a result of accumulating the brightness captured in the accumulating period on a line-by-line basis and sequentially output according to the arrangement of each pixel, and the signal level changes with time. This is due to the difference in brightness corresponding to the position of the pixel.

Therefore, 1 from the one-dimensional image sensor 3
Differentially combining the changing output signals of the photosensor during the output time of the signal corresponding to each pixel of the line causes a change in brightness that is not originally found in the original, which adversely affects the image signal. Could give.

Therefore, in the signal processing circuit 2c, the sample and hold circuit 20 is inserted and the one-dimensional image sensor 3 is inserted.
The signal from the optical sensor 1 or 9 is kept constant during the period in which the image signal is output from. That is, the timing controlled by the sample hold timing generation circuit 19 is set to a period in which the image output signal from the one-dimensional image sensor 3 is output in the hold period and the sample period is a period in which a signal unrelated to the image signal is output. .

By the way, in FIG. 7, the reading unit 22 in which the one-dimensional image sensor 3, the sub-scanning mechanism 4, the lens 5 and the optical sensor 1 are built in one housing, and the ceiling lamp 23 (in the present embodiment, in the present embodiment). This shows the case where the ceiling lamp 23 is located above the front side 24 of the reading unit 22 opposite to the front side 24 of the reading unit 22. In this case, the influence of the light emitted from the ceiling lamp 23 is different between the range A and the range B of the read document 7, and the range A has a larger influence of the ceiling lamp 23 than the range B. I am receiving. That is, in the main scanning direction 25, the influence of the ceiling light 23 appears to be strong or weak.

Therefore, the signal processing unit shown in FIG. 8 is configured to remove the influence of the ceiling lamp 23 on the original surface in the main scanning direction 25 of FIG. FIG. 8 shows a circuit system diagram of the fourth embodiment of the image processing unit. 6, the same components as those of FIG. 6 are denoted by the same reference numerals, and the description thereof will be omitted. The embodiment shown in FIG. 8 is a signal processing circuit 2d having a configuration in which a main scanning direction correction circuit 26 including an operational amplifier 261 and a capacitor 262 is provided on the output side of the sample hold circuit 20 of the signal processing circuit 2c of FIG. The point is characteristic.

In this embodiment, the main scanning direction correction circuit 26 is provided in the signal processing path output from the optical sensor 1 or 9.
(In this embodiment, a high-pass filter) is provided so that the output signal from the optical sensor 1 or 9 processed by the sample hold circuit 20 has a slope. The influence from the optical sensor 1 or 9 is set by the main scanning direction correction circuit 26 so that the signal output becomes small during the hold period according to the configuration of FIG. 7.

That is, assuming that the output signal from the one-dimensional image sensor 3 is the main scanning signal sequentially output from the range A toward the range B shown in FIG.
During the output period of the image signal for the line, the signal in the range A strongly influenced by the ceiling light 23 is output to the front in time, and the signal in the range B less affected is output to the rear in time. It
When the main scanning direction correction circuit 26 outputs the range A from the one-dimensional image sensor 3, the optical sensor 1
Alternatively, the signal is processed so that the signal from 9 is large, and is small when the output in the range B is being made.

As a result, the arithmetic circuit 14 causes the signal from the main scanning direction correction circuit 26 and the one-dimensional image sensor 3 to operate.
By taking the differential from the signal processed by the above, the influence of the ceiling lamp 23 radiated on the document surface can be removed even if there is a bias depending on the reading position.

FIG. 9 shows a circuit system diagram of the fifth embodiment of the image processing section. 6, the same components as those of FIG. 6 are denoted by the same reference numerals, and the description thereof will be omitted. In the embodiment shown in FIG. 9, the sample-hold circuit 20 of the signal processing circuit 2c shown in FIG. 6 is divided into two sample-hold circuits 20a and 20b, which are cascade-connected, and the sample-hold timing circuits 19a and 19b are also correspondingly provided. The feature is that the signal processing circuit 2e has a configuration in which two are provided as shown in FIG.

Here, one sample hold circuit 20
a is responsible for the delay due to the accumulation time of the one-dimensional image sensor 3 described above, and another sample hold circuit 20b
Has a function of keeping the signal of the optical sensor 1 or 9 constant during the image signal output period of the one-dimensional image sensor 3, as described above.

Next, the operation of this embodiment will be described with reference to FIG.
This will be described with reference to the timing chart of FIG. A sampling period 36 by the first-stage sample hold circuit 20a in FIG.
a is 1 shown in FIG. 10 (A) as shown in FIG. 10 (C).
During the accumulation period 33 of the one-dimensional image sensor, which is the low level period of the three-dimensional image sensor line trigger signal,
The hold period 37a by the first-stage sample and hold circuit 20a is changed to the sample period 36b by the second-stage sample and hold circuit 20b shown in FIG.
The sample hold control signal c input from the sample hold timing generation circuit 19a to the sample hold circuit 20a is set.

On the other hand, the second-stage sample hold circuit 20
As shown in FIG. 10 (D), the sampling period 36b by b does not overlap with the transfer period 34 in which the image signal of the one-dimensional image sensor is output, so that the output of the one-dimensional image sensor 3 shown in FIG. The signal transfer pause period 35 is set, and the hold period 37b by the second stage sample hold circuit 20b is sampled from the sample hold timing generation circuit 19b so as to cover the transfer period 34 during which the image signal of the image sensor is output. The sample hold control signal d input to the hold circuit 20b is set.

FIG. 11 shows a circuit system diagram of a sixth embodiment of the image processing section in the image reading apparatus according to the present invention. In the figure, the same components as those in FIG.
The description is omitted. In the circuit shown in FIG. 11, the optical sensor 1
Alternatively, the signal processing circuit 2 for processing the output signal from the sample holding circuit 20c and the sample and hold timing generating circuit 1 is replaced with the sample and hold circuit 20a and the sample and hold timing generating circuit 19a in FIG.
The feature is that it is a signal processing circuit 2f configured to use 9c.

The signal processing circuit 2 of the embodiment shown in FIG.
Reference numeral f is a signal processing circuit for the optical sensor signal, which incorporates the idea of the accumulation operation performed in the one-dimensional image sensor 3 when sampling the output signal from the optical sensor 1 or 9. The sample hold circuit 20c is provided between the output terminal of the operational amplifier 271 and the non-inverting input terminal of the operational amplifier 272,
A switch SW that is switching-controlled by the output control signal of the sample hold timing generation circuit 19c is provided, and the output of the operational amplifier 272 is fed back to the inverting input terminal of the operational amplifier 271 via the resistor R1 and the non-inverting input of the operational amplifier 272 is provided. Capacitor C between terminal and ground
1 and a resistor R2 connected in series, and an operational amplifier 27
In this configuration, the diodes D1 and D2 are connected in parallel between the output terminal 1 and the inverting input terminal.

In FIG. 11, the output signal of the optical sensor 1 or 9 is processed by the sample and hold circuits 20b and 20c provided in two stages as in FIG. 9, but when the sample and hold circuit 20c in the first stage performs sample and hold. To 1
The sample is performed so that the capacitor C1 electrically stores the same thing as that of storing the brightness of light by the three-dimensional image sensor 3. Therefore, the capacitance of the capacitor C1 is 1
It is necessary not to saturate within the storage time of the three-dimensional image sensor 3, and in the embodiment of FIG. 11, a capacitor of 2 μF or more is used.

By doing so, the change amount of light received from the ceiling light can be accumulated in the one-dimensional image sensor 3 and the optical sensor 1 or 9 during the accumulation period for one line, and the arithmetic circuit 14 Thus, the effect of the ceiling light can be better removed from the image signal.

As described above, the temporal fluctuation of the brightness of the light applied to the original surface of the read original 7 affects the output signal from the one-dimensional image sensor 3 and adversely affects the captured image. However, as a method of removing this adverse effect, the signal from the one-dimensional image sensor is not corrected and removed as in the above embodiment, but the light source for illuminating the document surface is corrected. Good.

FIG. 12 is a block diagram showing another embodiment of the image reading apparatus according to the present invention in this case. In FIG.
The same components as those described above are denoted by the same reference numerals. As shown in FIG. 12, in this embodiment, an optical sensor 1 for detecting a temporal change in brightness in a range corresponding to a plurality of pixels on the document surface of a read document 7 and an illumination control circuit 41 for driving illumination. An illuminating device 43 is provided which can change the brightness for illuminating the original surface with a drive signal input via the circuit 42.

Then, the signal indicating the change in brightness from the optical sensor 1 is processed by the signal processing circuit 2g to adjust the offset and the gain. The signal from the signal processing circuit 2g is input to the illuminance control circuit 41, and the brightness of the illumination device 43 is controlled via the illumination drive circuit 42 to eliminate the temporal change in the brightness of the document surface. The brightness of the lighting device 43 is controlled to be bright if the signal from the optical sensor 1 indicates that the signal is dark, and conversely if the signal from the optical sensor 1 is dark. That is, the brightness of the light emitted from the illumination device 43 is controlled according to the output signal of the optical sensor 1 so that the brightness of the light received by the optical sensor 1 from the document surface is constant.

Therefore, as the illuminating device 43, a fluorescent lamp or a light bulb that blinks at a fluctuation period of the brightness of the document surface (twice the commercial power supply frequency, 100 Hz in East Japan) or a faster cycle, or A bulb driven by direct current and continuously lit is preferable. In particular, in the case of a light source that is turned on, the method of using an inverter-driven fluorescent lamp that repeatedly blinks at a rate of 10 times or more the fluctuation cycle of the brightness of the document surface is relatively easy to control the brightness. In this case,
High frequency (normally 4
The control signal adjusted by the signal processing circuit 2g is input from the optical sensor 1 to the drive signal of 0 kHz or more), and the amplitude of the drive signal of the fluorescent lamp is amplitude-modulated so that the fluorescent lamp (illumination device 4).
The brightness of 3) can be changed.

As a control method of the illuminating device 43, a reference circuit showing a predetermined brightness is provided, the difference between the reference signal from this circuit and the signal from the optical sensor 1 is calculated, and the light source is equivalent to this difference. By performing the feedback control for controlling the brightness of the document, the brightness of the document surface can be controlled to be stable. As a result, it is possible to eliminate temporal fluctuations in brightness that have an adverse effect on the image signal.

In this embodiment, the image signal from the one-dimensional image sensor 3 is output in accordance with the timing generated by the image sensor drive circuit 45 and processed into a digital signal by the signal processing circuit 44. Is processed independently of the signal of.

As described above, in the embodiment of the present invention, the brightness of the document surface which changes with the passage of time is detected by using the optical sensor 1 or 9. However, the optical sensor 1 or 9 is generally a photodiode or A phototransistor can be used. The phototransistor and the image sensor generally have spectral sensitivities, which have different sensitivities depending on the wavelength. For example, a black and white one-dimensional image sensor has a spectral sensitivity peak at a green wavelength and a phototransistor has a spectral sensitivity peak at a wavelength greater than red. There are many things.

In the present invention, it is possible to further enhance the effect by matching the wavelength of the spectral sensitivity between the image sensor 3 and the optical sensor 1 or 9. For this reason, in the present invention, a filter that relatively well transmits green is provided in front of the phototransistor, which is the photosensor 1 or 9. By providing this filter, the output of the optical sensor 1 or 9 is slightly reduced, but the output reduction is prevented by increasing the gain of the amplifier. Further, when the one-dimensional image sensor 3 is not for black and white (for example, for color), the transmittance for red, green, and blue is good, and light of infrared and ultraviolet wavelengths is filtered by a filter that cuts the light. By matching the output characteristics from the sensor 1 or 9 with the spectral sensitivity characteristics covered by the color image sensor,
The effect of the present invention can be enhanced.

[0063]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, of the present invention, specific specifications of main components will be described. As the one-dimensional image sensor 3, a μPD3733 manufactured by NEC Corporation having a 2088-bit CCD array element is used. As the lens 5 provided on the one-dimensional image sensor 3 to form an image, a glass lens having a focal length of 40 mm and a longitude of 16 mm is used. As the sub-scanning mechanism 4, a mechanism in which a DC motor and a speed reducing mechanism are combined, or Japanese Patent Laid-Open No. 6-1
It is possible to apply the reflecting surface rotating means or the like of Japanese Patent No. 33079.

When reading one sheet by the one-dimensional image sensor, the image reflected on the reflecting mirror 6 and formed on the one-dimensional image sensor 3 by the lens 5 is read line by line and converted into an electric signal. The sub-scanning mechanism 4 rotates the reflecting mirror 6 to image the next line on the image sensor 3. This operation is repeated one after another (for example, if the number of arrays of the one-dimensional image sensor 3 is 2000 × 2800 lines, 2800
Repeat about times. ) Read the data for one screen. The light receiving surface of the optical sensor 1 is directed to the document surface, and the reflected light from the document surface is not used as a line unit but a plurality of dots are mixed in the main scanning direction and the brightness of a plurality of lines is mixed in the sub scanning direction. The light is received as and is converted into an electric signal.

As the photosensor 1 or 9 which is one of the features of the present invention, PT8L manufactured by NEC Corporation is used as a phototransistor with a lens. The spectral sensitivity of the phototransistor and image sensor is
The μPD3733, which is a one-dimensional image sensor, has a peak of spectral sensitivity at a green wavelength, and the photosensor PT8L has a peak of spectral sensitivity at a wavelength of red. Therefore, in the embodiment of the present invention, a filter which relatively well transmits green is provided on the front surface of the phototransistor PT8L which is an optical sensor.

[0066]

As described above, according to the present invention,
External light reflected from the document surface is received by an optical sensor and converted into an electric signal, and the arithmetic means performs arithmetic operation with the image signal based on the electric signal, or in response to an output signal of the optical sensor. By adjusting the brightness of the light source so that the brightness of the light emitted from the light source onto the document surface is constant, the signal component due to the external light in the image signal can be significantly reduced or eliminated. Therefore, it is possible to reduce or eliminate the adverse effect on the image signal due to the light-dark change of the frequency corresponding to the power line among the effects of the light irradiating the document surface on the image signal.

That is, according to the present invention, in a camera type image reading apparatus using a one-dimensional image sensor,
Even if the storage time per line of the one-dimensional image sensor is shorter than the cycle corresponding to the power line, the influence of the brightness that changes corresponding to the cycle of the power line can be suppressed, so when reading at high speed. It is possible to reduce the deterioration of image quality. Therefore, the present invention is effective in speeding up image reading and improving image quality without losing the simplicity of the camera-type image reading device.

[Brief description of the drawings]

FIG. 1 is a mechanism configuration diagram of a first embodiment of the present invention.

FIG. 2 is a mechanism configuration diagram of a second embodiment of the present invention.

FIG. 3 is a block diagram showing a basic configuration of an image processing unit in the device of the present invention.

FIG. 4 is a circuit system diagram of a first embodiment of an image processing unit according to the present invention.

FIG. 5 is a circuit system diagram of a second embodiment of an image processing unit according to the present invention.

FIG. 6 is a block diagram of an image processing unit according to a third embodiment of the present invention.

FIG. 7 is a configuration diagram of the present invention for explaining the influence of a ceiling light.

FIG. 8 is a circuit system diagram of a fourth embodiment of an image processing unit according to the present invention.

FIG. 9 is a block diagram of an image processing unit according to a fifth embodiment of the present invention.

FIG. 10 is a timing chart for explaining the sample hold timing of FIG.

FIG. 11 is a circuit system diagram of a sixth embodiment of an image processing unit in the invention.

FIG. 12 is a configuration diagram of another embodiment of the present invention.

FIG. 13 is a block diagram of an example of a conventional image reading device.

[Explanation of symbols]

1, 9 Optical sensor 2, 2a to 2g Signal processing circuit 3 One-dimensional image sensor 4 Sub-scanning mechanism 5 Lens 6 Reflecting mirror 7 Reading document 8 Rotating mechanism 10 Range 13, 16, 17 Pre-processing circuit 14 Arithmetic circuit 15 A / D Converter 18 Delay circuit 19, 19a, 19b, 19c Sample and hold timing generation circuit 20, 20a, 20b, 20c Sample and hold circuit 21 Image sensor drive signal generation circuit 22 Reading unit 23 Ceiling light 25 Main scanning direction 26 Main scanning direction correction circuit 33 1-dimensional image sensor accumulation period 34 transfer period 35 transfer pause period 36a, 36b sample period 37a, 36b hold period 41 illuminance control circuit 42 illumination drive circuit 43 illumination device 45 image sensor drive circuit 48 read line

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H04N 1/40 101B

Claims (9)

[Claims] 1. An image reading apparatus which outputs a two-dimensional image signal from a one-dimensional image sensor by scanning incident light from a read document to the one-dimensional image sensor in the sub-scanning direction using a sub-scanning mechanism. From the output signal of the optical sensor and the one-dimensional image sensor, an optical sensor that directly or indirectly detects a change in the brightness of external light applied to the original surface of the read original and converts it into an electric signal And an arithmetic means for receiving the image signal of 1) as an input signal and canceling and removing the change component of the brightness of the outside light from the image signal, and outputting the image reading device. 2. The delay circuit for delaying the periodic signal component of the output signal of the photosensor in accordance with the storage time of one line of the one-dimensional image sensor, and the one-dimensional image. 2. An arithmetic circuit for calculating an image signal from a sensor and an output signal of the delay circuit to cancel and remove a change component of the brightness of the outside light from the image signal, and output the arithmetic signal. Image reader. 3. The first arithmetic operation means is controlled at a timing of holding after sampling the output signal of the optical sensor, and during a period in which the image signals accumulated by the one-dimensional image sensor are sequentially transferred. Sample hold means, an image signal from the one-dimensional image sensor, and the first signal
2. The image reading apparatus according to claim 1, further comprising: an arithmetic circuit for calculating the output signal of the sample and hold means and canceling and removing the change component of the brightness of the external light from the image signal and outputting the cancelled component. 4. The optical signal is photoelectrically converted by the one-dimensional image sensor in the course of a signal path from the optical sensor to the first sample-hold means, and the light is accumulated during one line period. It is characterized by further comprising second sample-hold means for sampling a signal from the sensor and controlling the holding result until the accumulation result of the corresponding line is transferred to a register and output as an image signal is started. The image reading device according to claim 3. 5. The second sample-hold means accumulates an output signal of the photosensor in a capacitor corresponding to an accumulation amount accumulated as an electric charge according to a light amount at a time of accumulation in the one-dimensional image sensor. The image reading apparatus according to claim 4, further comprising a storage circuit for performing the above. 6. The calculation means reduces the influence of external light received on the document surface in the main scanning direction along the signal path from the optical sensor to the first sample hold means. 4. The image reading apparatus according to claim 3, further comprising a main scanning direction correction circuit that causes the output signal from the optical sensor sample-held by the first sample-hold means to have an inclination in correspondence with the inclination. 7. The optical sensor is provided between a reflecting mirror that constitutes the sub-scanning mechanism and the one-dimensional image sensor, and an image formed on the one-dimensional image sensor by rotation of the reflecting mirror. 2. The image reading apparatus according to claim 1, wherein the portion on the surface of the original that receives light changes in response to the change. 8. An image reading apparatus for outputting a two-dimensional image signal from a one-dimensional image sensor by scanning incident light from a read document to the one-dimensional image sensor in the sub-scanning direction using a sub-scanning mechanism. A light source for irradiating the document surface of the read document with light, and an optical sensor for directly or indirectly detecting a change in the brightness of the light irradiating the document surface of the read document and converting it into an electric signal. A light control circuit for controlling the brightness of the light emitted from the light source according to the output signal of the optical sensor so that the brightness of the light received by the optical sensor from the document surface becomes constant. Characteristic image reading device. 9. The image reading device according to claim 1, wherein the photo sensor is provided with a green filter on a light receiving surface.