JP2863191B2 - Image reading device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus used for a facsimile, an image scanner, and the like. The present invention relates to an image reading apparatus configured to be able to correct the output from the photoelectric conversion unit in accordance with the change (referred to as a shading change).

[Prior art] Conventionally, a strip light source such as a halogen lamp or a fluorescent lamp has been used as a light source of an image reading apparatus. Since the light quantity increases with time and shifts to a constant light quantity after power-on, the read output from the photoelectric conversion unit also changes along the sub-scanning direction (light source moving direction) in proportion to the initial fluctuation. Will be done.

In order to solve such a problem, a method of detecting the fluorescent lamp tube wall temperature conventionally used for the light source and controlling a fluorescent lamp driving voltage according to the temperature, and a method of controlling the fluorescent lamp ON / OFF every time the document is read without changing the fluorescent lamp ON / OFF. There is a method of keeping the illuminance constant by turning on the fluorescent lamp even during standby for reading. However, the former requires a temperature sensor and a fluorescent lamp driving voltage control circuit, which complicates the circuit configuration and increases the cost.

In the latter case, since the fluorescent lamp is turned on even while the original is being read, the life of the fluorescent lamp is shortened and power consumption is increased.

In order to solve such a drawback, a white diffuse reflection portion is provided in a parallel line shape close to the main scanning line of the optical system unit incorporating the light source, and the optical information of the additional main scanning line and the white color are reflected. There has been proposed an apparatus that detects light information from a diffuse reflection unit from a photoelectric conversion unit and performs shading correction while performing arithmetic processing on the ratio or difference between the two. (Japanese Patent Publication No. 61-51820) "Problem to be Solved by the Invention" However, a long tape-shaped white diffuse reflection member is attached along the main scanning direction of the optical system unit, in other words, over the entire width of the document. Mounting using means,
Not only is it difficult, but also wrinkles and bends are apt to occur during the attachment (sticking), and light information from the reflecting part due to adhesion of oils and fats and other partial stains generated at the time of sticking. Fluctuates, and accurate and accurate shading correction becomes impossible.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described drawbacks of the related art, and has as its object to provide an image reading apparatus that can be easily mounted and accurately and reliably perform shading correction.

"Means for Solving the Problems" In order to achieve the above technical object, the present invention provides a reference reflector that guides a photoelectric conversion unit to a partial reflector at a predetermined portion of a band-shaped light source as optical information, and the light source includes the reference reflector. The reference reflector is disposed integrally with the document surface so as to be relatively movable along the document scanning direction, and is included in the document reading information based on the optical information detected on the photoelectric conversion unit side. In an image reading apparatus configured so that an illuminance change component can be substantially offset (removed or canceled out), the reference reflector is disposed at a position deviating from the reading area in the document surface reading width direction, and the center of the band light source is arranged. An image reading device having the following configuration, characterized in that the reflection angle of the reference reflector is set so that radiated light in the region can be introduced as optical information to the photoelectric conversion element side.

The reference reflector 12 which guides the partial radiated light at a predetermined portion of the band light source 11 to the photoelectric conversion unit 2 as optical information is located at a position outside the reading area H in the document surface reading width direction, specifically, a band light source. At the longitudinal end side of 11, a point provided by setting the reflection angle of the reference reflector 12 as radiation information of the central area of the band-shaped light source as light information.The reflector 12 is integrated with the light source for document surface irradiation. A point attached to the illumination unit 1 side and configured to be relatively movable with respect to the document surface along a document scanning direction orthogonal to the document surface reading width direction. Optical information from the reflector 12 and a document obtained by irradiating the document surface. In this case, the read information and the photoelectric conversion unit 2 are configured to be detectable. In this case, the photoelectric information may be received by a conversion element 21 different from the photoelectric conversion element group 22 that receives the read information. Also, if necessary, the above information is photoelectrically converted with a level difference. It is preferable that the information can be received on the side of the unit 2 because the mixture of both information can be completely prevented.

A point in which the illuminance change component included in the document reading information can be substantially offset based on the optical information detected by the photoelectric conversion unit 2 side. That is, for example, a desired offset based on a detection signal corresponding to the optical information Data may be selected or derived, and shading correction of the digital signal corresponding to the read information may be performed using the derived offset data.

`` Operation '' The present invention, since the light amount distribution in the longitudinal direction of the belt-shaped light source 11 is known in advance, without obtaining light information based on the light amount distribution substantially the same as the document read information as in the prior art,
For example, if it is configured such that radiated light at a specific portion of the belt-shaped light source 11 can always be received at the fixed position by the reference reflector 12, the light information guided to the photoelectric conversion unit 2 side using the reference reflector 12 and the light information The light quantity distribution naturally has a corresponding relationship.

Therefore, by moving the reference reflector 12 integrally with the belt-shaped light source 11, it is possible to continuously detect a change in illuminance corresponding to the document scanning direction on the photoelectric conversion unit 2 side as optical information,
Thus, accurate shading correction can be performed by using the optical information.

Note that the specific portion receives the radiated light in the central region because other noise light easily enters on the end side of the belt-shaped light source 11.

As a result, the reflector 12 need only have a size capable of partially reflecting only a specific portion of the belt-like light source 11, so that there is no need to use a reflective tape of the same order as the document reading width unlike the related art. This allows the reflector 12 to be attached (sticked).
At the same time, the mounting work is facilitated without wrinkling or bending.

Hereinafter, preferred embodiments of the present invention will be illustratively described in detail with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. It's just

FIGS. 1 to 3 show an image reading apparatus incorporated in an image scanner according to an embodiment of the present invention. A fluorescent lamp 11 having a reflective film 11a applied on the back side thereof, a reference reflector 12 disposed on a longitudinal end side of the fluorescent lamp 11, and an illumination unit configured to be integrally movable. On the original surface 4a, which is fixed and has a slit 10 formed on the lower surface thereof along a direction perpendicular to the main scanning direction, and a transparent glass plate 4 together with the reference reflector 12 from the fluorescent lamp 11. Is configured to be capable of irradiating the belt-shaped radiation light to the light source.

On the other hand, 2 is a CCD sensor that functions as a photoelectric conversion unit,
The light image obtained from the document surface 4a and the light information obtained from the reference reflector 12 by the irradiation of the band-shaped radiation
Optical system 3 consisting of a turning mirror and a focusing lens via 13
The optical system 3 is configured such that the optical image and the optical information are deflected and converged by the optical system 3 and can be incident on the light receiving surface of the CCD sensor 2.

Next, the configuration of the reference reflector 12, which is a main part of the present invention, will be described.

The reference reflector 12 includes a support portion 12a fixed by screws on a vertical mounting surface 14 of the frame 10 located on the longitudinal end side of the fluorescent lamp 11, and a short side direction connected to the support portion 12a ( The main body 12b is formed by bending the main body 12b at predetermined angles θ ₁ and θ ₂ in the main scanning direction and the longitudinal direction (axial direction of the fluorescent lamp 11), respectively, and the reflector main body 12b is, as shown in FIG. 4a slightly deviated from the reading in the width direction said read area H, causes disposed slit opening 13 upper position, the longitudinal direction of the body 12b bent theta ₁ is directed slightly upward, radiation of the fluorescent lamp 11 central region with light is set to be incident, the widthwise direction of the body 12b substantially to 70 ° before and after bending theta ₂ to the vertical plane, the optical information guided to be reflected CCD side by body 12b, the original surface CC that receives the light image so as not to be mixed with the light image from 4a
The CCD element 21 different from the D element group 22 can receive the optical information.

A white tape 16 is attached to the reflection surface of the main body 12b, and is disposed closer to the fluorescent lamp 11 side than the glass plate 4 so that the lighting unit 1 can travel in parallel with the glass plate 4. I do. It should be noted that bringing the reflection surface closer to the fluorescent lamp 11 side means that light information from the reflector body 12b is received by the CCD element 21 at an illuminance level larger than the light image, as described later. By incorporating the comparator 51 in the correction circuit, the separation between the two can be performed more clearly. It is desirable that the reflector be configured such that the exposed portion except for the portion where the white tape 16 is adhered is applied in black so as not to reflect the light of the light source.

FIG. 4 shows a shading correction circuit using the above-described apparatus. The light image obtained from the original surface 4a by irradiating the band-like radiation light from the fluorescent lamp 11 passes through the slit opening 13 and the optical system 3. The detection output from the CCD element group 22 is guided to the shading correction operation circuit 56 via the A / D converter 52.

On the other hand, the optical information obtained from the reference reflector 12 is similarly guided to another CCD element 21 through the slit opening 13 and the optical system 3, and the detection output from the CCD element 21 is passed through a comparator 51. After removing the light image and other noise information below a certain voltage level, a digital signal corresponding to the light information is guided to a shading correction offset determination circuit 54 via an A / D converter 53, and a predetermined offset determination value is selected. I do.

Storage means for storing shading correction data set in advance based on the offset determination value
From 55, the offset data corresponding to the optical information is read, and a digital signal corresponding to the optical image is subjected to arithmetic processing in an arithmetic circuit 56 based on the offset data, whereby the effective image data from which the illuminance change component has been removed. Can be obtained.

[Effects of the Invention] As described above, according to the present invention, since the front reference reflector can be formed in a small size and with an end width, the number of mounting steps is significantly reduced, and a reflection tape is attached to the surface of the reflector. Even in the case where wrinkles and stains due to the variation at the time of sticking are hardly generated, as a result, the reflection level is made uniform, and even if the reflection tape is discolored due to aging, it is easy to replace it. .

Also, by setting the reflection angle of the reference reflector arbitrarily, the light information of the most appropriate portion can be obtained, the shading correction accuracy can be improved, and the reflection level can be arbitrarily set by the mounting angle. Accordingly, it becomes possible to remove the noise light or the like mixed with the image reading information, and the correction accuracy is improved.

 And so on.

[Brief description of the drawings]

1 to 3 show an image reading apparatus incorporated in an image scanner according to an embodiment of the present invention. FIG. 1 is a perspective view of a main part, FIG. 2 is a front view thereof, and FIG. It is a side view. FIG. 4 is a block diagram showing a shading correction circuit used in the device.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-105766 (JP, A) JP-A-60-113575 (JP, A) JP-A-63-52568 (JP, A) 160462 (JP, A) Japanese Utility Model Showa 60-88661 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) H04N 1/04-1/207

Claims (2)

(57) [Claims] 1. A reference reflector which guides a partial radiated light at a predetermined portion of a belt-shaped light source to optical information to a photoelectric conversion unit is provided integrally with the light source. In addition to being configured to be relatively movable along the scanning direction, it is possible to substantially offset (remove or cancel) the illuminance change component included in the document reading information based on the optical information detected on the photoelectric conversion unit side. In the image reading device, the reference reflector is disposed at a position deviating from the reading area in the document surface reading width direction, and radiant light in the central area of the band light source can be introduced as optical information to the photoelectric conversion element side, An image reading apparatus wherein a reflection angle of the reference reflector is set. 2. The mounting position, mounting angle or reflection efficiency of the reference reflector is set such that the light information and the read information are received by the photoelectric conversion unit with a difference in illuminance level. 1) The image reading device according to the above.