JPS6347025B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an image reading device that reads images using a solid-state image sensor (solid-state imaging device) such as a CCD or a MOS transistor. The purpose of this is to eliminate unevenness in image reading caused by variations in sensitivity between individual light-receiving cells.

FIG. 1 is a schematic diagram of the configuration of a general image reading device using a solid-state image sensor. Reference numeral 1 denotes a document to be read and processed, and it is fed in a sub-scanning direction in the y direction with the image surface facing downward by a feeding means not shown in the figure. The image surface is exposed to light by the illumination means 2 in the process of passing through the exposure section a during the feeding with an illumination line in the main scanning direction x--x perpendicular to the document sub-scanning feeding direction.
Exposure reflected light from the document surface at the exposure section a is imaged by the photographing lens 3 onto the light receiving section of the solid-state image sensor 4. The solid-state image sensor 4 is a one-dimensional type in which a large number of light-receiving cells are arranged parallel to the original illumination line, that is, in the main scanning direction x-x. Convert to signal.

The image of the document 1 is then imaged from the leading edge to the trailing edge by the sub-scanning feed y, exposure of the document in the main scanning direction x-x in the exposure section a, and the self-scanning function of the sensor 4 that receives the exposure reflected light. Full reading is done sequentially. Time-series electric pixel signals, which are image reading signals sequentially output from the sensor 4, are reproduced as images by an attached reproduction device (not shown) via a processing circuit (not shown), or by a facsimile system. If so, it is transmitted to a receiving station elsewhere.

Note that the original 1 is fed with the image surface facing upward, and the illumination means 2 and
There are systems in which a reading system such as a lens 3 and sensor 4 is arranged above the document moving path, and there are systems in which the document 1 is fixed and the reading system is moved relative to the fixed document.

By the way, in the above-mentioned apparatus, it is ideal that the document exposure in the exposure section a is uniform in each part along the main scanning direction x-x of the document surface, but it is quite difficult to achieve uniform exposure. It is. That is, a fluorescent lamp, which is a linear light source, is generally used as the illumination means 2, but the light emitted from the fluorescent lamp is not uniform along its length, and the luminance is usually lower at both ends than in the center. It has a distribution. However, due to the blackening phenomenon of both ends over time, the luminance of both ends decreases in comparison with the center. Therefore, the main scanning direction x of the document surface
-Exposure unevenness occurs with respect to x. Also, uneven exposure can occur depending on how the fluorescent lamp is installed. Similar problems exist with other line light sources.

Even if the surface of the document is illuminated with even exposure, if the exposure light reflected from the surface of the document is imaged on the light-receiving surface of the sensor 4 via the photographic lens 3 as in the illustrated example, the cosine of the lens is 4. Due to the decrease in the amount of light at the periphery of the image formed based on the power law, an imbalance occurs in the amount of light formed at the center area of the sensor 4 and the areas at both ends thereof.

Furthermore, the sensor 4 itself also has a ±10% gap between each light receiving cell.
There is some degree of light sensitivity variation, and in practice, the main scanning direction x
- Each part does not have uniform photosensitivity along x.

That is, the above-described uneven exposure of the original, a decrease in the amount of peripheral light of the imaging light due to the lens 3, and variations in sensitivity between sensor cells appear as non-uniformity in image reading.

Therefore, as a means to eliminate this image reading non-uniformity, a standard document reading comparison method has been generally adopted in the past. This causes the sensor 4 to once read the white uniformly coated surface without an image as a standard document before starting regular document reading. The output unevenness between the time-series signals corresponding to the individual sensor cells output from the sensor 4 due to this reading is caused by a combination of factors such as uneven exposure of the original, a decrease in the peripheral light intensity of the imaged light of the lens 3, and variations in sensitivity of the individual sensor cells. This represents the degree of non-uniformity in image reading between sensor cells. Therefore, after storing the standard document reading time-series signal in the control circuit as correction data, regular document reading is started and the individual signal components of the time-series read signal for each main scan of the document reading are corrected as described above. Modulation processing is performed in a direction to correct read non-uniformity based on the data.

In FIG. 1, reference numeral 5 denotes a standard document member fixedly disposed close to the document moving path on the side opposite to the illumination means 2 with the document moving path in the document exposure section a. The lower surface facing 2 has been treated with a white surface. Until the document 1 enters the exposure section a, the lower surface of the standard document member 5 is exposed to light by the illumination means 2, and the reflected light is imaged on the sensor 4, and when the document 1 enters the exposure section a. The original 1 is exposed to light by passing under the lower surface of the standard original member 5, and the reflected light is imaged on the sensor 4.

FIG. 2 is a block diagram of an example of the image reading non-uniformity correction circuit, in which 6 is a circuit changeover switch, and its movable element 61 is connected to the apparatus shown in FIG. The document 1 is kept in contact with the terminal 62 side until it reaches the immediately preceding part a, and when the leading edge of the original 1 reaches the exposure area a, its arrival is detected, and from then on until the original 1 finishes passing through the exposure area a. The relationship is such that it is switched and held on the terminal 63 side.

Then, until the original 1 reaches the part directly in front of the exposure part a, the lower surface of the standard original member 5 in the exposure part a is illuminated by the illumination means 2, and the reflected light is imaged on the sensor 4. Reading signals for the five sides are output. The signal enters the A/D converter 7 via the mover 61 and terminal 62 of the switch 6, is converted into a digital signal, and is stored in the memory 8 as correction data. Thereafter, the leading edge of the original 1 reaches just before the exposure area a and enters the exposure area a, causing the mover 61 of the switch 6 to move to the end point 63.
At the same time, the sensor 4 of the original 1 starts sequentially reading the original surface, and the reading signal is input to the correction circuit 9 via the movable element 61 and the terminal 63 of the switch 6. On the other hand, the correction circuit 9 receives the signal of the correction data stored in the memory 8.
The original reading signal is converted into an analog signal by the A converter 10 and inputted, and is inputted to the correction circuit based on this correction signal. The original reading signal is appropriately corrected and inputted to the image reproduction circuit or transmission circuit 11. It is something. 12 is a sequence control circuit for each of the control circuits described above.

By the way, the above-mentioned correction method allows each light-receiving cell of the sensor 4 to read information of the same color tone, thereby eliminating uneven exposure of the original, a decrease in the peripheral light intensity of the imaged light of the lens 3, and variations in sensitivity between the individual light-receiving cells of the sensor. The sensor 4 outputs a time-series signal corresponding to each light-receiving cell representing the degree of image reading non-uniformity between individual sensor light-receiving cells that is caused by a combination of Therefore, the exposure surface of the standard document member 5 is made to have a uniform color tone surface in each part in the main scanning direction x-x so that each light receiving cell of the sensor 4 reads information of the same color tone. It is required that the person has the following. However, it is quite difficult to form a completely uniform color tone surface on each part of the exposed surface of the standard document member 5 in the main scanning direction xx. Furthermore, during use, the exposure surface becomes randomly contaminated with dust, scratches, etc., which tends to impair uniformity, and has the disadvantage that the accuracy of the correction data signal is reduced.

The present invention also uses a standard original reading comparison method to correct the non-uniformity of the regular original reading signal, but it uses a method in which each light-receiving cell of the sensor 4 reads the same part surface (same location) of the standard original. By doing so, the problems of poor correction accuracy and deterioration of accuracy due to non-uniformity of color tone and dirt along the main scanning direction x-x of the standard document are solved.

That is, by repeating the reading of the surface of a standard document member by moving the member step by step in the main scanning direction by the individual light-receiving cell array pitches of the solid-state image sensor. The gist of the present invention is an image reading device characterized in that reading signals related to body parts are obtained and each of the signals is used as the correction data signal.

FIG. 3 shows a specific example of this, in which the fixed standard document member 5 in the example in FIG. ′. The outer surface of the endless belt member 5' is painted almost uniformly white. The coating may not be applied to the entire circumference of the belt, but may be applied only to a portion thereof. Moreover, the coating is not limited to white, but may be painted in an intermediate color. 14 is a stepping motor that drives one of the belt-suspending rollers 13, 13 and rotates the belt 5' intermittently by the array pitch of each light-receiving cell of the sensor 4; 15 drives the motor 14; circuit,
16 is the circuit 15, the fluorescent light 2 which is the illumination means,
This is a sequence control circuit for the solid-state image sensor 4.

The reading of the standard original 5' is performed in the following manner. The first reading is performed by the sensor 4 while the rotation of the belt 5', which is a standard document, is stopped, and the first light-receiving cell S1 of the sensor 4 among the reading time-series signals obtained thereby.
Only the read signal corresponding to (FIG. 4) is stored in the memory 8 (FIG. 2) as correction data regarding the first light receiving cell S1. In this case, if only a portion of the belt 5', which is the standard document, is painted, the painted portion is located at a position corresponding to the first light-receiving cell of the sensor 4.

Next, the stepping motor 14 is driven to rotate the belt 5' in the main scanning direction by one pitch of the array of light receiving cells and then stop it. As a result, the belt 5' surface portion 5'', which is the standard document, which corresponded to the first light-receiving cell S1 during the previous reading, is positioned as shown in FIG. 4. Then, the sensor 4 performs the second reading. Of the read time series signals obtained thereby, only the read signal corresponding to the second light receiving cell S2 of the sensor 4 is stored in the memory 8 as correction data regarding the second light receiving cell S2.
Thereafter, by repeating such intermittent feeding and reading of the belt 5', read signals regarding the same portion surface 5'' of the belt 5', which is a standard document, are stored in the memory 8 for each of all the light receiving cells S1 to Sn up to the final cell Sn. The stored signals are then used as data for correcting the normal original reading signal.

In other words, the correction data signal is obtained by having all the light receiving cells S1 to Sn of the sensor 4 read the same part surface 5'' of the standard document.
The result is the same as when reading a standard original with a uniform color tone surface in each part in the main scanning direction x-x, and non-uniformity of color tone and dirt on the standard original surface are responsible for poor accuracy and accuracy reduction of the correction data signal. do not.

Therefore, a highly accurate correction data signal can be obtained at all times, whereby a normal image reading signal can be properly corrected, and a good reproduced image can be obtained.

In the example shown in FIG. 3, the standard document member 5' is configured as an endless belt, and the belt is rotated in steps. It may be configured to move in steps.

The standard document reading process is normally completed before the document 1 enters the exposure section a.
is read and the read signal is stored, and then a standard document is read and processed to obtain a correction data signal and stored in the memory 8. Then, when the stored document read signal is re-outputted, the signal is used for correction. A circuit configuration that performs correction processing based on data may be used.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the configuration of a general document reading device.
FIG. 2 is a block diagram of an electric circuit for correcting read signals, FIG. 3 is a schematic diagram of the configuration of an example of the device of the present invention, and FIG.
The figure is an explanatory diagram of the relationship between each light receiving cell of the sensor and the reading area surface of a standard document. 1 is a document, 2 is an illumination means, 3 is a photographing lens, 4
is a solid-state image sensor, 5 and 5' are standard originals, a
is the exposed part.

Claims (1)

[Scope of Claims] 1. A solid-state image sensor is used to read an image, and the non-uniformity of the read time-series electric pixel signals due to uneven exposure of the original, sensitivity variations of individual light-receiving cells of the solid-state image sensor, etc. In an image reading device that electrically performs correction processing using the reading time-series electric pixel signals of a standard original material surface with no image and uniform color read by the same sensor as correction data, the reading of the standard original material surface is performed. By moving the member step by step in the main scanning direction for each individual light-receiving cell array pitch of the solid-state image sensor and repeating the reading, the read signals relating to the same portion of the standard original member are obtained for each light-receiving cell, and the read signals are obtained. An image reading device characterized in that each signal is used as the correction data signal.