JP3431586B2 - Image reading device - Google Patents

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 such as a scanner or an optical character reading device, and more particularly to an image reading device having an output level correction mechanism for correcting the output level of an image sensor using a level reference plate. Regarding the device.

[0002]

2. Description of the Related Art Generally, an image reading device such as a scanner or an optical character reading device uses a CCD image sensor by irradiating a form as a reading medium with light and capturing the reflected light with a CCD image sensor. Read the image on the form according to the output.

In such a reading device, the following correction (adjustment) is generally performed to correct the level of the output signal of the CCD image sensor when the device is manufactured. As these corrections, shading correction, gain adjustment,
There is dimming.

Shading correction is performed by using a white reference plate whose surface is set to white as a reference for level correction. That is, the shading correction means that when the reflected light from the white reference plate is input to the CCD image sensor,
This is to electrically correct the output signal of the CCD image sensor so that the output voltages from all the photoelectric conversion elements of the CCD image sensor have the same value.

The gain adjustment means adjusting the amplification degree (gain) of the signal amplifier so that the level of the output signal of the CCD image sensor after shading correction becomes a constant value. This gain adjustment is performed so that the image on the form can be correctly read even if the form having a white background and the reflectance of any light is input. This adjustment is a particularly important correction when reading a color image. There is also a method of correcting the signal level of the output signal of the CCD image sensor by adjusting the light amount of the light source instead of the gain adjustment.

However, the change of the light quantity due to the secular change of the light source,
Also, the signal level of the output signal of the CCD image sensor may change due to aging and temperature characteristics. Therefore, it is difficult to always obtain an output signal at the same level as that at the time of manufacture from the CCD image sensor.

Therefore, conventionally, at the time of starting the apparatus, a white reference plate is arranged at the reading position, and the light reflected by the white reference plate is input to the CCD image sensor.
The output signal from the image sensor is used to perform the above-mentioned shading correction, gain adjustment, and dimming, and an output level correction mechanism for disposing this white reference plate at the reading position is provided.

As such an output level correction mechanism, the one disclosed in Japanese Patent Publication No. 7-113952 is provided. This output level correction mechanism is provided with a rotation mechanism for rotating the white reference plate. When the output level is not corrected, the white reference plate is used to read the form so that the CCD image sensor can read the form. When the output level is corrected by holding it at a position deviated from the position, the white reference plate is rotated to the reading line position of the CCD image sensor.

[0009]

The rotating mechanism in the output level correcting mechanism as described above includes a solenoid connected to the white reference plate via a link mechanism, and the reciprocating movement of this solenoid is rotationally driven by the link mechanism. The white reference plate is rotated by being converted into.

In such a structure, it is difficult to move the white reference plate at high speed, and it is difficult to accurately hold the white reference plate at the reading position. Therefore, in the conventional reading device, the output level is corrected only when the device is started, but in this case, it is not possible to correct the fluctuation of the output voltage of the CCD image sensor when the device is used for a long time, This causes a decrease in reading accuracy.

The present invention has been made in view of the above points, and an object thereof is to enable the white reference plate to be operated at a high speed, and to reliably hold the white reference plate at a predetermined reading position, thereby improving the reading accuracy. To provide the image reading device.

[0012]

In order to achieve the above object, an image reading apparatus according to the present invention comprises a carrying mechanism for carrying a reading medium through a reading position, and a light source for irradiating light toward the reading position. A reading unit having a light receiving sensor for receiving the reflected light reflected at the reading position and converting it into an electric signal, and an output level correction mechanism for correcting the output voltage of the light receiving sensor according to a reference level, The output level correction mechanism includes a reference plate for taking in a reference level, and a support mechanism that rotatably supports the reference plate between the reading position and a retracted position retracted from the reading position, A cam engaged with the above support mechanism and rotating this cam
It has a driving source to drive and reads the reference plate from the retracted position.
And a drive unit for rotating the cam.
A first plate for rotating the dummy plate to the reading position and holding it for a predetermined time.
Rotating and holding the cam surface and the reference plate to the retracted position
And a second cam surface that is
It is formed in an arc shape concentric with the center of rotation, and the second cam surface is
It is formed in an arc shape eccentric to the rotation center of the cam.
It is characterized by

[0013]

[0014]

According to the image reading apparatus configured as described above, since the drive unit of the output level correction mechanism is configured to move the reference plate by rotating the cam, the reference plate is switched to the reading position at high speed. be able to. As a result, the reference level can be read and output level correction can be performed each time the reading medium is read, and an image reading apparatus with improved reading accuracy can be obtained.

[0016]

Further, according to the above configuration, the reference plate can be stopped at the reading position for a predetermined time even while the cam is rotating, and the reference level in the stationary state can be accurately detected. can do. Since it is not necessary to stop the rotation of the cam, the output level correction can be easily speeded up.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION An optical character reading device according to a first embodiment of the present invention will be described in detail below with reference to the drawings. As shown in FIG. 1, the optical character reading device includes a substantially rectangular box-shaped housing 10, and on the front surface of the housing, a hopper table 12 on which a form P serving as a reading medium is placed, and a respective hopper table 12 that has been read. First and second stackers 14 and 15 for accumulating the forms P are provided.

In the case 10, a plurality of forms P placed on the hopper table 12 are taken into the case one by one, and a case where two or more forms are taken in by the paper feed rollers. Is provided with a separator 20 that separates the second and subsequent forms from the first form and prevents feeding of the second form.

Further, in the housing 10, the form P taken in by the paper feed roller 18 is stored in the first and second stackers 1.
A transport mechanism for transporting to either of 4 and 15 along a predetermined transport path 16 is provided. As shown in FIGS. 1 and 2, this transport mechanism includes a plurality of guide plates 23 arranged along the transport path 16, a plurality of guide rollers 22, and a drive motor functioning as a drive source for driving the guide rollers. 54 is provided. At the terminal end of the transport path 16, a sorting gate 24 that sorts the form P transported through the transport path to the first or second stacker 14 or 15 is provided.

A reading position R is set in the vicinity of the supply roller 18 in the conveying path 16, and characters or the like are read from the form P conveyed through the conveying path 16 in the housing 10 at the reading position R. A reading unit 27 for reading

The reading section 27 includes a CCD image sensor 34 as a light receiving sensor mounted on a printed circuit board 32 provided on the inner wall of the housing 10, and a light source 26 for irradiating light toward a reading position R. The mirrors 28 and 30 and the converging lens 31 are provided for inputting the form P passing through the reading position or the reflected light reflected by a white reference plate described later that has been moved to the reading position to the CCD image sensor 34. The lens 31 as seen from the CCD image sensor 34
Is focused on the reading position R. Therefore, the image of the form P and the reference level of the white reference plate are read by the CCD image sensor 34 at the reading position R. Then, the image data read by the CCD image sensor 34 is converted into an electric signal, and the control unit 3
3 and image processing is performed there.

As shown in FIGS. 1 to 3, an output level correction mechanism 36 for correcting the output level is provided below the reading position R in the housing 10. The output level correction mechanism 36 has a white reference plate 42 whose surface is set to white and serves as a reference for capturing a reference level.
And a support mechanism 40 that rotatably supports the white reference plate 42 between a read position R and a retracted position retracted from the read position, and the white reference plate 42 reads the retracted position through the support mechanism. And a drive unit 50 that rotates between the position and the position.

The white reference plate 42 is formed in an elongated rectangular shape longer than the width of the form P, and extends in the direction orthogonal to the transport path 16. Both ends of the white reference plate 42 are bent at right angles to form an arm 44. These arms 44 are rotatably supported by a support shaft 45 via bearings, and the support shaft is supported by a frame (not shown) of the housing 10. The arm 44, the support shaft 45, and the frame form a support mechanism 40.

A roller 48 functioning as a cam follower is rotatably attached to the extending end of one arm 44. The central axis of rotation of the roller 48 is the white reference plate 42.
It runs parallel to.

The drive unit 50 has a cam 52 that is in rolling contact with the roller 48, and a drive motor 54 that rotationally drives the cam 52 via a gear train 55. The roller 48 is elastically pressed against the cam surface of the cam 52 by a torsion spring 46 as a biasing member that is provided between the arm 44 and the frame of the housing 10. Then, by rotationally driving the cam 52, the roller 48 moves following the cam, so that the white reference plate 42 moves to the support shaft 45.
It rotates between the reading position R and the retracted position around the center.

More specifically, as shown in FIG. 4, the cam 52 has a substantially elliptical shape and has two first cam surfaces 52a.
And two second cam surfaces 52b, and the first and second cam surfaces are alternately and continuously formed. First
The cam surface 52a is formed in an arc concentric with the rotation center C of the cam 52, and has a radius r and a central angle θ. Also, the second
The cam surface 52b is formed in an arc that is eccentric by an eccentric amount e in a direction protruding with respect to the rotation center C.

When the cam 52 rotates, as shown in FIG. 4, the white reference plate 42 is rotated and held in the retracted position while the second cam surface 52b is in contact with the roller 48. Further, as shown in FIG. 5, while the first cam surface 52a is in contact with the roller 48, the white reference plate 42 is rotated to the reading position and is held at this reading position. Here, since the first cam surface 52a is formed concentrically with the center of rotation C, the white reference plate is rotated while the cam 52 rotates by the angle θ while the first cam surface 52a is in contact with the roller 48. 42 is held stationary at the reading position.

Next, the image reading operation and the output level correcting operation of the optical character reading device configured as described above will be described. In the state before the start of the reading operation, the white reference plate 42 is held at the retracted position and is separated from the reading position R. Then, at the start of reading, output level correction is first performed. That is, the drive motor 54 is operated to rotate the cam 52, and the white reference plate 42 is rotated from the retracted position to the reading position R. The white reference plate 42 has a first cam surface 52.
While a is in contact with the roller 48, it is held at the reading position R in a stationary state, and the cam 52 further rotates to move the second cam surface 52.
When b comes into contact with the roller 48, it is returned to the retracted position. At this point, the rotation of the cam 52 is stopped and the white reference plate 42 is held at the retracted position.

While the white reference plate 42 is stationary at the reading position R, the light emitted from the light source 26 and reflected by the surface of the white reference plate 42 is reflected by the mirrors 28, 30 and the lens 31. Is input to the CCD image sensor 34. Then, the CCD image sensor 34 converts the received light into an electric signal and inputs the electric signal to the control unit 33. The control unit detects the reference level based on the electric signal, and the CCD image sensor according to the detected reference level. Of the output voltage, that is, the output level is corrected.

After the above-mentioned output level correction is completed, the forms P on the hopper table 12 are taken in one by one by the supply roller 18 and conveyed along the conveying path 16. Then, at the reading position R, the form P is read from the light source 26.
The reflected light is input to the CCD image sensor 34 via the mirrors 28, 30 and the lens 31. Then, the CCD image sensor 34 converts the received light into an electric signal and inputs the electric signal to the control unit 33, and the control unit subjects the electric signal to image processing to read the image read from the form P.

Further, after the form P is read, until the next form P reaches the reading position R, the driving unit 50 is turned on again.
Then, the white reference plate 42 is moved to the reading position R, and the above-mentioned output level correction is performed. After that, the output level correction and the form reading described above are alternately repeated until the form P on the hopper table 12 is exhausted. Then, the read form P is sorted by the sorting gate 24 into the first or second stack 14 or 15 and accumulated.

According to the optical character reader constructed as described above, since the drive unit 50 of the output level correction mechanism 36 is configured to move the white reference plate 42 by rotating the cam 52, the white reference plate is used. The plate 42 can be switched to the reading position at high speed. As a result, the reference level can be read every time when each form P is read, and the output level can be corrected at any time, and the reading accuracy can be improved.

Further, according to the present embodiment, the cam 52
Includes a plurality of first cam surfaces 52a that rotate the white reference plate 42 to the reading position R and hold it for a predetermined time, and a second cam surface 52b that rotates the white reference plate 42 to the retracted position and hold it. Since each has one, per cam rotation,
The white reference plate 42 can be reciprocated twice between the reading position R and the retracted position, and the output level correction can be easily speeded up.

Further, since the first cam surface 52a is formed in an arc concentric with the rotation center C of the cam 52, the cam 5
Even while the 2 is rotating, the white reference plate 42 can be stopped at the reading position R for a predetermined time, and the white reference plate 42 in the stationary state is used to detect the reference level to output with high accuracy. Level correction can be performed.
At the same time, since it is not necessary to stop the rotation of the cam 52,
The output level correction can be easily speeded up.

Next, the output level correction mechanism 36 in the optical character reader according to the second embodiment of the present invention will be described. As shown in FIGS. 6 and 7, according to the second embodiment, the cam 5 of the output level correction mechanism 36
2 is configured to include one first cam surface 52a and one second cam surface 52b. The first cam surface 52a has a radius r and a central angle θ, and is configured by an arc concentric with the rotation center C of the cam 52. In addition, the second cam surface 52b is
It is formed by a circular arc eccentric to the rotation center C of the cam 52 by an eccentric amount e. The radius r of the first cam surface 52a is set smaller than the radius of the second cam surface 52b.

When the cam 52 rotates, as shown in FIG. 6, the white reference plate 42 is rotated and held at the retracted position while the second cam surface 52b is in contact with the roller 48. Further, as shown in FIG. 7, while the first cam surface 52a is in contact with the roller 48, the white reference plate 42 keeps the reading position R.
And is held at this reading position. Where the first
Since the cam surface 52a is formed concentrically with the center of rotation C, the white reference plate 42 is read at the reading position R while the cam 52 is rotated by the angle θ while the first cam surface 52a is in contact with the roller 48. To be held stationary.

Further, as shown in FIGS. 8 and 9, according to the output level correction mechanism 36 in the optical character reading apparatus according to the third embodiment of the present invention, the cam 52 has the first cam surface 52a. And the second cam surfaces 52b are provided one by one. The first cam surface 52a has a radius r and a central angle θ, and is configured by an arc concentric with the rotation center C of the cam 52. In addition, the second cam surface 52b is
Is formed by a circular arc decentered by an eccentric amount e with respect to the center of rotation C. According to this embodiment, the first cam surface 52a
Radius r is set to be larger than the radius of the second cam surface 52b.

When the cam 52 rotates, as shown in FIG. 8, the white reference plate 42 is rotated and held in the retracted position while the second cam surface 52b is in contact with the roller 48. Further, as shown in FIG. 9, while the first cam surface 52a is in contact with the roller 48, the white reference plate 42 keeps the reading position R.
And is held at this reading position. First cam surface 5
Since 2a is formed concentrically with the rotation center C, the first
While the cam surface 52a is in contact with the roller 48, the white reference plate 42 is held stationary at the reading position R while the cam 52 rotates by the angle θ. However, in the third embodiment, the retracted position of the white reference plate 42 is a position rotated with respect to the reading position in the direction opposite to that of the first and second embodiments described above.

In the second and third embodiments described above, the other structures are the same as those in the first embodiment, and the same parts are designated by the same reference numerals and their detailed description will be given. Is omitted. Also in the second and third embodiments, as in the first embodiment, the white reference plate 42 is read at high speed by operating the white reference plate using the cam 52 as a rotating member. It is possible to switch to position R and easily speed up output level correction, and
The reading accuracy can be improved.

Besides, the present invention is not limited to the above-mentioned embodiments, but can be variously modified within the scope of the present invention. For example, the present invention is applicable not only to the optical character reading device but also to other image reading devices such as a scanner. Further, in the first embodiment, the cam is configured to include two first and second cam surfaces, but the present invention is not limited to this, and a configuration including three or more first and second cam surfaces. May be Further, in the above-described embodiment, the output level is corrected each time each form is read.
The output level may be corrected every time a plurality of reading media are read or at any timing.

[0042]

As described above in detail, according to the present invention, it is possible to operate the white reference plate at a high speed and surely hold it at a predetermined reading position during output level correction. An image reading device with improved reading accuracy can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view showing an optical character reading device according to a first embodiment of the present invention.

FIG. 2 is an enlarged side view showing an output level correction mechanism in the optical character reading device.

FIG. 3 is a perspective view showing a white reference plate and a cam of the output level correction mechanism.

FIG. 4 is a diagram schematically showing a relationship between a white reference plate moved to a retracted position and a cam in the output level correction mechanism.

FIG. 5 is a diagram schematically showing a relationship between a white reference plate moved to a reading position and a cam in the output level correction mechanism.

FIG. 6 is a diagram schematically showing a relationship between a white reference plate moved to a retracted position and a cam in the output level correction mechanism of the optical character reading device according to the second embodiment of the present invention.

FIG. 7 is a diagram schematically showing a relationship between a white reference plate moved to a reading position and a cam in the output level correction mechanism of the optical character reading device according to the second embodiment.

FIG. 8 is a diagram schematically showing a relationship between a white reference plate moved to a retracted position and a cam in the output level correction mechanism of the optical character reading device according to the third embodiment of the present invention.

FIG. 9 is a diagram schematically showing a relationship between a white reference plate moved to a reading position and a cam in the output level correction mechanism of the optical character reading device according to the third embodiment.

[Explanation of symbols]

16 ... Transport path 26 ... Light source 27 ... Reading unit 34 ... CCD image sensor 36 ... Output level correction mechanism 40 ... Support mechanism 42 ... White reference plate 44 ... Arm 48 ... Laura 52 ... Cam 52a ... 1st cam surface 52b ... second cam surface 54 ... Drive motor R ... Reading position P ... form

Front page continued (72) Inventor Hideharu Ito 1-3-3 Shinmachi, Ome-shi, Tokyo Inside Toshiba Digital Media Engineering Co., Ltd. (56) Reference JP-A-3-191662 (JP, A) JP-A 4-208935 (JP, A) JP-A-7-189856 (JP, A) JP-A-5-316300 (JP, A) JP-A-8-166639 (JP, A) JP-A-10-215352 (JP, A) Actual Kaihei 3-108875 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04N 1/04 G06T 1/00 460

Claims (3)

(57) [Claims] 1. A transport mechanism for transporting a reading medium through a reading position, a light source for irradiating light toward the reading position, and a light receiving sensor for receiving reflected light reflected at the reading position and converting it into an electric signal. And an output level correction mechanism for correcting the output voltage of the light receiving sensor according to a reference level, and the output level correction mechanism includes a reference plate for capturing the reference level, the reference plate possess a support mechanism that rotatably supported between a drive source for rotating the cam and the cam engaging with the support mechanism and a retracted position retracted from the reading position and the reading position and a driving unit for rotating the upper <br/> Symbol reference plate reading position from the retracted position, the cam is Tokoro by the reference plate is rotated to the reading position
Set the first cam surface that holds the fixed time and the reference plate to the retracted position.
And a second cam surface for rotating and holding the first cam.
The cam surface is formed in an arc shape concentric with the center of rotation of the cam.
And the second cam surface is eccentric with respect to the rotation center of the cam.
An image reading device characterized by being formed in a circular arc shape . 2. The cam has a pair of the first cam surfaces and a pair of the second cam surfaces, and the first and second cam surfaces are alternately arranged. The image reading device according to claim 1 . 3. The support mechanism includes a rotatable cam follower rollingly in contact with the cam surface of the cam, and a biasing member biasing the cam follower toward the cam. The image reading apparatus according to claim 1 .