JP2006115288A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To illuminate only a region corresponding to a detected document size in an image reading apparatus that selectively illuminates only a document region corresponding to a document size detection result using a line light source composed of a plurality of white LEDs. The auxiliary means for correcting the light amount at the edge during control is used to improve the edge drop of the light distribution, and the optimum shading correction is performed for each paper size.
An image reading apparatus comprising: a document size detecting unit; a white LED array light source; a white LED array partial lighting control unit; a document edge light amount assisting unit; a unit for performing shading correction for each document size;
[Selection] Figure 1

Description

  The present invention relates to an image reading apparatus configured by using a line light source (line light source) configured by using a light emitting element such as an LED with low power consumption as a document illumination unit.

  Conventionally, a cylindrical tube light source (linear light source) such as a halogen lamp, a fluorescent lamp, or a xenon tube has been used as a document illumination unit of an image reading apparatus. Halogen lamps have been used in image readers for a long time because of their high light intensity and high response to instantaneous lighting, but their use in image reading devices in recent years has decreased due to their high power consumption and large amount of heat generation. In recent years, the use of a fluorescent lamp and a discharge tube such as a xenon tube with low power consumption occupy the mainstream of image reading apparatuses in recent years.

  However, fluorescent lamps tend to be refrained from the use of mercury, which is used to secure the light intensity due to the problems of rising characteristics of light intensity and stability of light intensity, and the recent trend to reduce harmful substances. Although the startup characteristics are excellent, the amount of light is slightly small, the amount of heat generation increases as the amount of light increases, and high voltage power supply of about 1000V to 2000V is necessary. Against this backdrop, the adoption of illumination means using semiconductor light sources such as LEDs, whose light emission amount has been increasing dramatically in recent years, has become a reality in terms of further reducing power consumption and reducing harmful substances. ing.

  Incidentally, although the above-described conventional document illumination means is a linear light source, it cannot partially control lighting. This is because the halogen lamp is composed of a plurality of filaments connected in series, so that partial power supply control is not possible, and the fluorescent lamp and xenon tube use a discharge phenomenon between the electrodes. It is a factor. For this reason, it is common knowledge that the original illumination lamp used in the image reading apparatus controls the lighting of the entire lamp to read the image regardless of the original size, and performs correction control so that the light distribution of the lamp is uniform. The image was scanned. Therefore, the image reading apparatus handled in offices, convenience stores, stationery stores, etc. illuminates the entire area of the document main scanning direction 297 mm (maximum reading width at the time of setting the A3 size in the R direction as an AB document) During the reading of the document under the open state of the document pressure plate or the document conveying device of the image reading device, the document irradiation light leaking from the region other than the set document width (when a document having a width of less than 297 mm) is set to the operator's eyes It gave a strong stimulus to the eyes and sometimes had an adverse effect on the eyes.

  However, in the conventional image reading apparatus using the document illumination means that cannot control partial lighting, call the operator's attention near the platen glass of the image reading apparatus “Please do not look directly at the document illumination light.” There is no way to take any measures other than sticking a warning label that says, or writing a warning text to warn of the danger of direct viewing of the original illumination light in the instruction manual. It has been left as a common sense of reading devices.

  The common sense (fixed concept) of the image reading apparatus is reviewed, and the original is illuminated by using the original illumination means in which (white) LEDs are formed in an array as the original illumination means of the image reading apparatus in consideration of the environment. The following has been proposed as a document reading apparatus for scanning a document.

  (Conventional Example 1) A control unit that uses a white LED array in which light emitting elements are arranged in a zigzag pattern as a light source for irradiating a document, and changes a lighting region of the white LED array in accordance with the document size and application, and a lighting region control unit In addition, there is one that includes a lighting on / off control unit and a lighting light quantity control unit, and controls lighting of only the document size area detected by the document size detection unit (see, for example, Patent Document 1).

  (Conventional example 2) A white LED array in which light emitting elements are arranged in parallel to the main scanning direction is used as a light source for illuminating a document, and the amount of light emitted by the white LEDs is individually controlled by controlling the amount of current to each light emitting element. There are some which eliminate the shadow generated in the central part of the Book original or the like by adjusting to. (For example, refer to Patent Document 2).

  (Conventional Example 3) Further, the white LED is arranged in an array in the main scanning direction, and has a plurality of heat generating means and a plurality of temperature detecting means arranged in the vicinity of the LED array and along the extending direction, and the LED array. Lighting control is performed, and the heating means is driven and controlled in accordance with the detection result of each temperature detection means, thereby suppressing fluctuations in the amount of illumination light and the emission spectrum. (For example, refer to Patent Document 3).

(Conventional example 4) Also, it has LED light sources of R, G, and B colors, and sets the lighting time and current value for color copying and black and white copying, and corrects the amount of light in the effective image area. Some perform optimal light amount adjustment in an effective image area. (For example, refer to Patent Document 4).
JP 2002-247296 A JP 2002-314760 A JP 2002-281240 A JP 2001-169054 A

  However, in the above conventional example 1, only the document area of the document size detected by the document size detection unit can be controlled to be turned on. However, since the image is read with the light emitting element outside the document area turned off, the document illumination is performed. The amount of light at the edge of the document is less than when the entire area of the instrument is controlled to light, and in a reduction optical system with a condenser lens, the cosine fourth law or vignetting It is difficult to improve the phenomenon of attenuating the amount of light, and the S / N at the edge of the document becomes extremely poor, and it is difficult to solve the problem that the image becomes black.

  In the above-described conventional example 2, it is possible to adjust the light amount of the individual light emitting elements. However, by controlling the light amount within a predetermined range of the document area, the light amount with respect to the low density portion (document floating portion) in the document is controlled. It raises the fog and is different from the adjustment to read the original faithfully.

  Further, in the above-described conventional example 3, the light source is obtained by adjusting the temperature in the vicinity of the LED array in order to compensate for non-uniform illuminance and color variation caused by the temperature change of each LED due to the heat generated when the white LED array is continuously lit. However, it is not for correcting the edge illuminance at the time of partial lighting according to the document size.

  In the conventional example 4, the light quantity correction in the effective image area having a plurality of colors such as R, G, and B is optimally adjusted by controlling the lighting time and the current value of the LED. Because it does not consider the light quantity shortage from outside the area and the light quantity deterioration due to cosine fourth law or vignetting, it causes a significant light quantity shortage at the end of the effective area, resulting in a fogged image or an image with extremely poor S / N. The optimal light intensity adjustment cannot be executed.

  From the above examples, an original area lighting method that can eliminate unnecessary illumination light in the area outside the original document and reduce the burden on the eyes of the operator becomes important from the viewpoint of future energy saving and environmental response. However, the conventional image reading apparatus only mentions that the document area is selectively illuminated, so that an illumination system that maintains a uniform light distribution by actually entering from the area outside the document. There was no mention of the need to compensate for the decline in illuminance at the document edge.

  Accordingly, an object of the present invention is to perform conventional lighting control for illuminating means that does not illuminate unnecessary areas outside the document, lighting control for the document edge auxiliary illumination means, and optimal shading correction for each document size. Provided is an image reading apparatus equipped with a low power consumption original illuminating means capable of obtaining a light distribution characteristic equivalent to that of an image forming apparatus using a light source such as a halogen lamp, a fluorescent lamp, or a xenon tube for each original size. That is.

  The present invention provides a partial lighting control unit of a document illuminating unit for controlling lighting only in the document area corresponding to the document size detected by the document size detecting unit, and a document edge auxiliary lighting unit corresponding to the detected document size. By performing the lighting control and the optimal shading correction for each document size, it is possible to provide an image reading apparatus capable of realizing the optimum image reading by the minimum lighting control of the document illumination element.

  In order to solve the above-mentioned problems / objects, the present invention provides a document illumination means (line light source) composed of a plurality of light emitting elements, a photoelectric conversion means for reading reflected document light, a document size detection means, and a detection document. In an image reading apparatus configured to include a document area lighting control unit, a shading correction unit, and an operation unit corresponding to a main scanning area of a size, each document size with respect to an edge (edge) of a set document An image reading apparatus characterized by having auxiliary illumination means for compensating the amount of light, shading correction in the lighting control state of only the document area, and document scanning using the document illumination means. It is to provide.

  The present invention relates to an apparatus for illuminating only a document area and scanning a document by using a document illumination unit composed of a white LED array. Compensate the image quality by improving the light distribution characteristics and performing optimal shading correction for each document size, and the document illumination light leaks out of the document outside area, which harms the health of the eyes of the operator. There is an effect to prevent that.

Example 1
Hereinafter, embodiments of the image reading apparatus of the present invention will be described. FIG. 1 shows a block diagram of an image reading apparatus of the present invention. First, a hardware configuration related to image formation will be described. Reference numeral 101 denotes a controller of the image reading apparatus, which includes storage means centered on the CPU (112), signal processing means (119) including shading means, lamp control means (110), and the like. As an arithmetic processing unit of the image reading apparatus, there is a CPU 107, and conditions and the like generated during the operation of the apparatus are stored as temporary storage in the internal RAM (114) or the partial RAM (116).

  A ROM (117) stores a main program of the image reading apparatus. In recent years, ROMs are often composed of semiconductor memories in which programs can be rewritten, such as flash memories, and flash memories are frequently used at the time of soft stability improvement before the transition to inexpensive mask ROMs. An EEPROM (115) is a backup memory, and is a memory (storage device) for backing up setting contents that are difficult to be deleted when the power is turned off, such as the device operation mode and factory adjustment result. The signal processing means (119) has an image of ASIC in this case, and has a configuration in which most of the signal processing means in this case are integrated.

  Although there are many detailed processes, the configuration of the ASIC unit has been simplified and described in accordance with the present invention. The pulse generation means (121) includes a driving clock for a photoelectric conversion element (108) (hereinafter referred to as CCD) such as a CCD and CIS, a processing clock inside an ASIC (not shown), and a synchronization signal inside an original reading device (not shown). And so on. When the CCD driving pulse output from the pulse generation means (121) and the conversion clock (not shown) for the A / D conversion means (109) are supplied to the image reading means (102), the CCD (108) The analog output is converted into a digital signal (video signal) via the A / D conversion means (109). The image reading apparatus adjusts the black signal level and the white signal level inside the apparatus. The black signal level is obtained by setting the DC offset of the signal level of the CCD (108) when the light source (103) is turned off to an initial setting value (for example, Processing is performed by adjusting the output value of the A / D converter (109) to a level of about 08 (HEX) by DC offset adjusting means (not shown). The white level adjustment is performed when the signal level of the shading plate (white reference plate) CCD (108) (not shown) in the light source (103) lighting state is the target level (for example, F0 (HEX) when the resolution is 8 bits). Level matching is performed by adjusting the gain of a variable amplifier (not shown) so that the level becomes a certain level. (However, if the light source has a dimming function and the supply current of the white LED can be adjusted for each LED, the light source may be adjusted.

  The S / N ratio is better when the amount of light is increased than when the gain is adjusted. In this case, shading correction for correcting light distribution unevenness of the light source (original illuminating means = light source) (103) and sensitivity unevenness of the CCD (108) is collectively processed by the image processing means (122). . When shading correction is executed via the image processing means (122), a correction coefficient corresponding to the video signal is obtained and stored in the storage means (123).

  The correction coefficient stored in the storage means (123) is referred to when reading an image, and uneven light distribution and uneven sensitivity are improved. The transmitter (120) supplies the main clock of the signal processing means (119). Similarly, the oscillator (113) supplies the main clock of the CPU (114).

  Next, the remaining configuration will be described along the control of the image reading apparatus. When a document pressure plate (not shown) is set in the image reading device (not shown), the operator first opens the document pressure plate (not shown) and sets the document (not shown) at a predetermined position on the image reading device. Then, the document pressure plate (FIG. 1-104 is described as document conveying means) is closed.

  At this time, when the original pressure plate is closed and becomes less than a predetermined angle, the DF opening / closing SW (107) is turned on (L → H or H → L), and the CPU indicates that the original pressure plate is in the closing state. Input to the input port (112). The CPU (112) determines that a document has been set from the level change of the input port, drives the document size detection means (106), and detects the document size. (There are several document size detection methods, and any method can obtain the same result. Therefore, this time, the number of reflection type document size detection sensors is two on the main scanning width side, and the sub scanning width side is two. The arrangement of the document size detection means will be described with reference to FIG.

  With the document size detection means arranged in this way, AB document sizes of B5, A4, B5R, A4R, B4, and A3 can be detected. Further, there are a total of four types (B5R / A4R / B5 = B4 / A4 = A3) regarding the main scanning document width. The detected document size is stored in the built-in RAM (114) of the CPU (112) or the external RAM (116) connected via the address / data bus (118). At the same time, a mirror base unit (not shown) (a document scanning unit including a light source, a reflection mirror, etc.) is moved to a shading plate (reference white plate) reading position (not shown). The movement control of the mirror base unit is performed after the document size is determined, from the CPU to the optical motor / control circuit (105) (not shown) such as control signals (CW / CCW switching signal, motor clock, phase current control signal (DC level)). ). (In the above description, the optical motor is described assuming a two-phase stepping motor.

The motor control signal is converted into excitation patterns of + A phase, -A phase, + B phase, and -B phase by a driver (not shown) on the control circuit (105) and supplied to the motor. When the mirror unit moves to the shading plate reading position (when the count number of the motor clock necessary for the movement reaches the necessary count number), the CPU (112) determines the lamp control means (110 based on the stored document size data). Serial data (images are shown in FIGS. 9-909 and 910) for controlling the lighting of the document area by the light emitting element selection means (111) incorporated in the light source (103) is created, and a white LED array driver (not shown) of the light source (103) is created. Forwarded to the department. (The lighting / non-lighting control of the light emitting element, the issuing element selecting means, and the light emitting element register configuration will be described later with reference to FIGS. 8, 9, and 10.)
The document area lighting control serial data is held in a white LED array driver (not shown), and a copy button (not shown) which is one function of the input means (128) prepared on the operation unit (125) is pressed. As a result, a lamp ON / OFF signal (not shown) is separately generated from the output port of the CPU (112), and the lighting control of the light source (103) corresponding to the detected original scanning width is performed. At the same time, the drive control of the CCD (108) is performed, the CCD drive pulse (not shown), the conversion clock for the A / D conversion means (109), and the CCD-ON signal are controlled, and the reading level of the shading plate is A. The signal is input to the signal processing means (119) via the / D conversion means (109). A shading correction coefficient is calculated from the read image data of the shading plate. (Refer to the following prior art documents for the means for calculating the shading correction coefficient: Japanese Patent Laid-Open No. 7-298046, Japanese Patent Laid-Open No. 11-69154) Normally, the CCD-ON signal uses the output port of the CPU and the drive power supply for the CCD (108) The CCD (108) is turned off in synchronism with the CCD-OFF signal.

  In addition, although it is a problem in control, the CCD-ON / OFF signal and the CCD drive pulse are controlled in synchronization. (If the CCD is always in the ON state, it is not preferable from the viewpoint of power consumption, temperature rise in the machine, and unnecessary radiation, so the ON control is performed in synchronization with the copy button.) In the operation unit (125), the display means (127) is the number of copies. A man-machine interface for checking under the setting conditions of the image reading apparatus such as a copy mode, in this case, a liquid crystal panel is assumed, and a display control means (126) is assumed to be a liquid crystal controller (driver).

  Based on the device configuration described above, the phenomenon in question, the operation flow of this case, and the hardware configuration / control configuration will be described in order.

  FIG. 2 is an example showing generally known optical characteristics. Fig.2- (a) is a diagram showing the cosine fourth law, and Fig.2- (b) is a diagram showing vignetting. The cosine fourth law is a law of physics, but it is a law that points out that the brightness of a light beam incident at an angle with respect to the optical axis decreases in proportion to the fourth power of the cosine of the incident angle. The amount of light decreases as the distance from the optical axis increases. That is, the incident light is incident on the optical axis as shown in FIG. 2-201, and the amount of light at the speed of light (205) that forms an image on the imaging surface (204) through the condenser lens (203) is “1”. Incident light having an angle Θ passes through the condenser lens (203), and the amount of light at the speed of light (206) that forms an image on the imaging plane (204) is “cos 4Θ”.

  For example, when Θ = 30 °, cos 4 (30 °) = 0.5625.

  According to this law, even when a lens that is not affected by light vignetting is used, incident light having an incident angle of 33 ° or more can only obtain a light amount of 50% or less with respect to the optical axis. I understand.

  FIG. 12 shows the relationship between the incident angle and the attenuation rate. 1201 is a graph showing the values of cos and cos 4 from Θ: 0 ° to 90 °. 1202 is a table showing values of cos 4 from Θ: 0 ° to 90 °. Further, as an image of the image reading apparatus, the light amount on the photoelectric conversion means is inversely proportional to the square of the distance and is proportional to the cosine fourth power, as shown by 1204, from an image diagram (1203) considering the distance L between the light source and the photoelectric conversion means. It can be seen that there is a relationship. Here, E indicates the light amount of the light source, and EL indicates the light amount on the photoelectric conversion means.

  Next, vignetting will be described, and vignetting is blocked by the lens edges and frames before and after the aperture without passing through the entire aperture diameter, which is the effective aperture, where the light bundle incident on the lens periphery is, This is a decrease in the amount of light at the periphery. That is, as shown in FIG. 2- (b), the central light speed (201) and the peripheral light speed (through the front frame (207), the diaphragm (211), and the rear frame (208) constituting the lens barrel (212) 202), the width of the speed of light passing through the aperture (211) is clearly different as shown in the figure, and the amount of light at the imaging position (209) at the peripheral light speed is lower than the imaging position (210) at the central light speed. I understand that.

  That is, it is considered from the time when a halogen lamp was used as an image illuminating means that the peripheral light amount is significantly lower than the central consideration amount for these reasons. In the halogen lamp, the light amount due to cosine fourth law, vignetting, etc. In anticipation of down, a light source with a light distribution characteristic was prepared in which the amount of light at both ends of the lamp was raised from the center. Specifically, the arrangement density of the filaments that hit the light-emitting portion was increased only at both ends of the tube to take measures (not shown). In addition, fluorescent lamps, xenon tubes, etc., emit light by using discharge between electrodes, but the light distribution can be adjusted somewhat, but the phosphor coating process becomes complicated (unstable) and halogen For the reason that the amount of light does not rise as much as the lamp, etc., the tube length was made longer and the flat light distribution part was made longer. Therefore, the depth direction of the document reading apparatus equipped with the halogen lamp is long.

  For these reasons, it is necessary to devise a technique for raising the amount of light at the edge of the document when illuminating only the document illumination means constituted by the white LED array, particularly the document area.

  Next, the configuration of the present invention will be described with reference to FIG. Reference numeral 301 denotes an original platen glass of the original reading apparatus, and the original is set with the upper left side of the original platen glass as an abutting reference. The shading plate (white reference plate) (302) is illuminated by the white LED array (307), and the original reflected light passes through the first mirror, the second mirror, and the third mirror (not shown) through the condenser lens (309). It has a configuration for forming an image on the CCD (310). Here, reference numeral 308 is formed on the white LED array (307), and the document end portion shown in B5R (311), A4R (312), B5 (313) / B4 (314), and A4 (315) / A3 (316). The auxiliary light source arranged in the white light source (307) is determined in accordance with the document size detected by the document size detection means (303, 304, 305, 306). That is, if a B5 (313) size document is detected by the document size detection means, the position of the shading plate (302) 320 is set as the document edge, and the document abutting position indicated by 317 or the document abutting side outside the document The lighting control of the LED up to the area and the auxiliary light source (308) corresponding to the positions 320 and 317 are turned on. Similarly, in the case of a B5R (311) document, up to the position 318 of the shading plate, in the case of an A4R (312) document, up to the position 319 of the shading plate, in the case of an A4 (315) / A3 (316) document. Lighting control is performed up to the position 321 of the shading plate. In the figure, reference numeral 322 denotes an optical center. That is, in the portion located in both the main scanning directions from the position indicated by 322, the light amount is significantly reduced due to the influence of the cosine fourth law and vignetting.

  An actual light distribution example is shown in FIG. (Note that the explanatory diagram in FIG. 4 actually shows the light distribution characteristic indicated by the solid line as shown by 414 and 415. However, in writing the explanatory diagram, the part in question in this case (light distribution in the shaded part) In order to clearly show “down”, the explanatory diagram is based on the light distribution characteristic indicated by the broken line.) FIG. 4 is a light distribution diagram when white LED lighting control is performed in the document size region. (b) shows the light distribution (413) (light distribution of a halogen lamp, a fluorescent lamp, a xenon tube, and a white LED light source that lights the entire area) when the entire area is lit (not the original area alone). (However, in this explanation, the light distribution characteristics are shown as flat characteristics except for the end portions. However, in actuality, control is performed so that the control current of the white LED increases from the center to the outside of the light emitting element. (If not, it will be understood that the light distribution characteristic of the saddle type will be obtained, and the reduction in the amount of light at the edge of the document is remarkably illustrated.) That is, the area outside the document is sufficient with respect to the abutting reference position (401). By arranging white LED elements and similarly arranging sufficient white LED elements in an area exceeding the A3 original width, the light distribution (412) in the original area is kept flat. Here, reference numeral 402 denotes the edge light amount distribution of the white LED array.

  FIG. 4- (a) shows the light distribution in which the white LED array light source is controlled to be turned on only in the area corresponding to the document size. Reference numeral 411 indicates a region with a light amount of 1/2 as a guideline, which means that the S / N deteriorates twice or more even if it is compensated by shading correction. In the figure, reference numerals 403, 405, 407, and 409 indicate the lighting areas of the white LED array light source, and the light amount at the B5R document end (404) and the light amount at the A4R document end (406), respectively. As shown in B5 / B4, the amount of light at the document end is reduced (408), and the amount of light at the end of the document, A4 / A3 is decreased (410), the attenuation of the amount of light increases as the position of the end of the document is farther from the optical center. .

  Since the purpose of this case is to remove the influence on the eyes of the operator when using the white LED array light source, fogging at the edge of the document caused by the phenomenon as shown in FIG. A white LED light source having an auxiliary light source as shown in FIG. 5 has been proposed in order to improve image roughness caused by S / N deterioration. First, the most important point is that the irradiation spot of the light emitting element of the white LED light source (516) is surely applied to the document end portion of the standard document (517). For example, the light emitted by the white LED indicated by 505 forms an irradiation spot as indicated by 508 on the document (501). The radiation spot (508) is represented by a double circle, but this shows an image in which the amount of light decreases as it moves away from the center, and the irradiation spot near the center with a high amount of light illuminates the edge of the original (501). It shows that it is.

  On the contrary, with this arrangement, the array leaks a slight amount of light from the edge of the document, but the irradiation spot of the white LED has a certain degree of directivity, so it does not directly affect the operator. Further, in the example shown in the edge light quantity assist (518), in order to prevent the light distribution at the document edge from being extremely reduced due to the absence of the document illumination light from the area outside the document, An auxiliary light source is arranged. Therefore, the original (501) forms irradiation spots 509 and 510 by the auxiliary light sources (504 and 507), and four irradiation spots (508, 509, and so on) by using white LEDs 504 to 507 at the end of the original. 510, 511). Reference numeral 512 denotes a light distribution characteristic of the illumination light supplied by the mutual illumination effect of the irradiation spot (511) of the white LED constituting the white LED array.

  Reference numeral 515 denotes a document edge, and the light distribution is 514 when there is no auxiliary light source, and 513 when the auxiliary light source is lit. By providing this auxiliary light source at the edge of the original, the light distribution of the original area illumination light is improved as shown in FIG. (However, in this explanation, the light distribution characteristics are shown like the flat characteristics except for the edges, but in practice, unless the white LED is mounted with increasing mounting density from the center to the outside, the vertical shape is used. Needless to say, the light distribution characteristic is as shown in the light distribution flat in order to make the light amount reduction at the edge of the document remarkable.

  The actual light distribution characteristics in this case have characteristics as shown in 612 and 613, 612 shows the light distribution characteristic in which the white LED outside the document outside the document abutting position is lit, and 613 is in the document region. The light distribution characteristic when only lighting is controlled is shown. Furthermore, the portion where the light amount down portion at the document edge portion is supplemented by the auxiliary light source, and the portions 604, 606, 608, and 610 are also reflected in the actual light distribution characteristics. Note that reference numeral 601 denotes a document abutting position. Reference numeral 602 denotes the edge light distribution characteristic of the white LED array, similar to 402.

  Reference numerals 603, 605, 607, and 609 denote lighting regions of the white LED array (the lighting regions are the same as those without the auxiliary light source in FIG. 4). Thus, although there is a difference in the light amount attenuation rate due to the difference in the position condition of the document edge from the optical center, the B5R document edge light distribution (604), the A4R document edge light distribution (606), and B4 / B5, respectively. Since the document edge light distribution (608) and the A4 / A3 document edge light distribution (610) are sufficiently corrected as compared with the light distribution 1/2 area, the effect of improving the fog at the document edge and the S / S N improvement effect can be realized.

Further, the end light distribution, 604, 606, 608, and 610 differ from each other due to factors such as the cosine fourth law, vignetting, and illuminance variation of the white LED. Each time the lighting region (603, 605, 607, 609) of the white LED light source is selected, it is necessary to individually perform shading correction, calculate an optimal correction coefficient, and perform image formation. (When all white LEDs are turned on only for shading correction, the correction coefficient at the edge of the document is different, and shading stripes may occur in the edge image.)
Next, regarding the lighting control of the white LED array light source, two types of light source lighting control regions of FIG. 7- (a) and FIG. 7- (b) are conceivable. FIG. 7- (a) shows an example of a document reading apparatus equipped with a white LED light source (704) configured with a margin to the area outside the document. Reference numeral 701 denotes a shading plate, reference numeral 702 denotes an original platen glass, and an original (703) is set to an abutting reference (based on the upper left of the original platen glass).

  As an advantage in this case, since a plurality of white LEDs are arranged in the area outside the original on the abutting reference side, the amount of light at the end of the abutting side can be reduced little. Further, the decrease in the amount of light at the edge of the opposite document edge can be improved by turning on the auxiliary light source. A white circle 705 means that the white LED is lit, and a black circle 706 means that the white LED is off. FIG. 7- (b) shows an example of a document reading apparatus equipped with a white LED light source (708) configured to illuminate only the document region. Reference numeral 707 denotes a shading plate, and reference numeral 702 denotes an original platen glass. The original (703) is set to an abutting reference (based on the upper left of the original platen glass). The advantage of this configuration is that the external dimensions of the document reading apparatus can be reduced. The white LED is turned on and off in the same manner as in FIG. 7- (a). A white circle 705 means that the white LED is on, and a black circle 706 means that the white LED is off. It means that. Further, the auxiliary light source at the edge of the document is lit at both ends, reducing the reduction in the amount of light at the edge.

  Next, the structure of the white LED array light source is shown in FIG. In this case, the white LED part (a) and the auxiliary light source part (b) for illuminating the document are separately provided, and two white LEDs are used as the light source 809 of the auxiliary light source part. This is in order to make a difference such as using it. The lighting method of the white LED is the same for both (a) and (b). Hereinafter, the configuration of the white LED array light source will be described with reference to FIG. 8, FIG. 9, and FIG. In FIG. 8, reference numeral 801 denotes a white LED element. Reference numeral 802 denotes a switch transistor for turning ON / OFF the current flowing through the white LED.

  The amount of light emitted from the white LED is limited by a current control resistor existing between the white LED and the transistor (802). If the resistance value is small, the amount of light emitted from the white LED increases. The amount of emitted light decreases. Reference numeral 804 denotes a shift register (D flip-flop) for transferring the selection signal of the white LED array, and transfers the white LED selection data (806) in synchronization with the transfer clock (807). The data set in the shift register (804) continues to be held in the same state unless the reset signal (805) is input, the transfer clock (807) does not advance, or the power supply (not shown) is stopped. After the data has been transferred to each shift register (804), if the LAMP lighting signal (808) is supplied with an active "H", an AND circuit ( The output of 803) is held at “H”, and the transistor (802) is turned on. That is, the white LED array is turned on.

  Since this configuration has the same circuit configuration in FIGS. 8A and 8B, the individual description of FIG. 8B is omitted. Subsequently, the transfer image of the white LED selection data will be described with reference to FIG. For example, there is a white LED array as shown at 901, and the data for turning on the white LEDs from Q1 ′ to Q4 ′ is the data for the last 4 clocks of 9 clocks of the transfer clock (908) as shown at 910. Is a selection signal having a width of.

  That is, the selection signals selected by the white LED selection unit (not shown) are arranged in order from the light emitting elements arranged at a long transfer distance with respect to the registers corresponding to the number of elements of the white LED array. Then, the data is transferred between the shift registers in order such as 910⇒909 by the same number of transfer clocks as the number of light emitting elements. The explanation of FIG. 8 is double, 903 is a reset signal for resetting the data of the shift register, 904 is a white LED selection signal (909, 910), 905 is a transfer clock (908), and 907 is a power supply supplied to the white LED. is there. Reference numeral 902 denotes an arrow to indicate that it is located at the edge of the document.

  Next, FIG. 10 will be described. FIG. 10 shows the above-described configuration in a simple block diagram. That is, when a detection result of a pressure plate closing detection sensor (not shown) serves as a trigger and a document size detection result by the document size detection means (1002) is input to the input port of the CPU (1001), the lamp control means (1003) is displayed. The original size code is sent to the light emitting area selection means (1004). In the light emitting area selecting means (1004), the white LED corresponding to the document area is set to “H” active and shifted to the shift register (1005).

  When data is set in the shift register, it is transferred to and held in the shift register of the white LED light source (1007) by a transfer clock (not shown). When the copy button is pressed by the operator, the CPU (1001) starts a document reading operation, and executes lighting control of the white LED light source (1007) from the lamp ON / OFF switch (1006).

  Reference numerals 1007_1 and 1007_2 denote examples of the data transfer shift register configuration of the auxiliary light source and the white LED array for document illumination. In the configuration of 1007_1, data (1009) corresponding to the white LED area corresponding to the document size is transferred in advance, and finally the data for auxiliary light source (1008) is transferred continuously. The advantage of this configuration is that, when detecting the main scanning width of the document using the white LED light source, the auxiliary light source data (1008) is transferred for 5 clocks and the lamp lighting signal is sent following the reset signal (not shown). Thus, it is possible to control the lighting of the auxiliary light source at the edge of the document. That is, if the reflected document light illuminated by the auxiliary light source can be read by a CCD (not shown), the main scanning width of the original can be determined, and the cost can be reduced by two original reflective sensors for main scanning. Become.

  Next, regarding the configuration of 1007_2, this is a configuration in which transfer registers are connected in the order of arrangement of the white LED array and the auxiliary light source. That is, according to the data transfer direction (1019), the auxiliary light source 5 (1018), the white LED for document illumination (1017), the auxiliary light source 4 (1016), the white LED for document illumination (1015), and the auxiliary light source 3 (1014). The white LED for document illumination (1013), the auxiliary light source 2 (1012), the white LED for document illumination (1011), and the auxiliary light source 1 (1010) are transferred in this order. This configuration has the shortest wiring length.

  Next, a control flow in the image reading apparatus will be described with reference to FIG. 1101 and later start document reading. When the document conveying apparatus is mounted in the flow of 1103 through 1102, control differs depending on the presence or absence of a set document. However, if the document feeder is not installed, it is determined as a document pressure plate model and the process proceeds to 1104. In this description, the original platen model will be described first. In step 1104, the operator opens the original platen, and in step 1105, the original is set at the abutting reference position on the platen glass.

  Through 1106, the state of the original pressure plate is detected in the flow of 1107. When the original pressure plate is closed, the original pressure plate detecting means (not shown) detects the original pressure plate closing state and activates the original size detecting means. The document size is determined in the flow 1108. If the original pressure plate cannot be closed in the flow 1107, the flow advances to a determination flow 1118 to wait until the original size is input from an operation panel (operation unit) (not shown). If the document size is not input in the flow 1118, the flow of 1106, 1107, 1118, and 1122 is repeated within the predetermined time in the time over determination flow of 1122, and by any chance, the document size within the predetermined time at 1122 If there is no input, the original reading operation is terminated in the flow of 1123.

  If the document size is input in the flow 1118, the flow proceeds to the determination flow as to whether or not the copy button is pressed in the flow 1110 via the flow 1109. If the copy button is not pressed in the flow of 1110, the flow of 1109, 1110, and 1120 is repeated in the time over determination flow of 1120 if it is within the predetermined time. If there is no document, the document reading operation is terminated in the flow 1121.

  When the copy button is pressed in the flow 1110, the data set of the original illumination area determined from the original size is performed in the flow 1111 and the reading unit (not shown) is moved to the home position (HP) (not shown). In this case, the home position is a position where shading correction is performed. Subsequently, the document area lighting control of the document illuminating means is performed in the flow of 1112, and the shading correction coefficient is calculated while reading the density level of a shading plate (white reference plate) (not shown). When the calculation of the shading correction coefficient is completed, the original scanning is started in the state where the original illumination means in the original illumination area determined in the above 1111 flow is controlled to be turned on by the flow 1113, and when the original area in the sub-scanning direction is passed. To turn off the original illumination means.

  Through the flow of 1114, in the determination flow of 1115_next document, if there is a next document, the document setting by the operator and the copy start control are repeated again through the flow of 1102. In the 1115_next original determination flow, if there is no next original, the original reading operation is completed in the flow 1116, and the reading unit (not shown) is moved to the home position (HP) (not shown). Then, the original reading operation is terminated in the flow 1117.

  However, although the document illumination means is controlled to be turned off in the flow of 1113, when the document is read continuously, the document illumination means is not controlled to be turned on / off every time the document is scanned. Can be turned off. In the present flow description, the description has been made on the original platen, but the same applies to the original conveying apparatus. Next, a flow when a document is set on the document conveyance device in a model equipped with the document conveyance device will be described from the flow of 1103.

  When a document is set on the document conveying means in flow 1103, the main scanning width of the document is determined by the set width of a document guide (not shown) of the document conveying means in flow 1124. When the document width is determined, the flow proceeds to the copy button determination flow 1126 via the flow 1125. If the copy button is not pressed, the flow of 1125, 1126 and 1132 is repeated if it is within the predetermined time in the time over determination flow of 1132, and if the document size is not input within the predetermined time at 1132 by any chance. Completes the document reading operation in the flow 1133.

  When the copy button is pressed in the flow 1126, the original illumination area corresponding to the original main scanning width determined in the previous flow 1124 is determined in the flow 1127, the data is set, and the reading unit (not shown) is set. Move to a home position (HP) (not shown). In this case, the home position is a position where shading correction is performed. Subsequently, the document area lighting control of the document illuminating means is performed in the flow of 1128, and the shading correction coefficient is calculated while reading the density level of a shading plate (white reference plate) (not shown).

  When the calculation of the shading correction coefficient is completed, the original set on the original conveying means starts to be conveyed from the flow 1129. Further, the length in the longitudinal direction of the document being conveyed is detected by a sensor (not shown) provided in the conveyance path, and the size of the document being conveyed is determined. The document scanning is started in the state where the document illumination means in the document illumination area determined in the flow of 1130 is controlled to be turned on by the flow of 1131, and the illumination of the document illumination means is controlled to turn off when the document area passes in the sub-scanning direction. Do. When the document scanning is completed, the flow of 1114 is followed by the flow of determination of 1115_next document. If there is a next document, the flow of 1102 determines the presence or absence of the document set on the document conveying means. The flow of 1124 transition is repeated through the following flow. (Here, the flow 1115 and the flow 1103 are equivalent.) Also, in the 1115_next original determination flow, if there is no next original, the original reading operation is completed in the flow 1116. The reading unit (not shown) is moved to a home position (HP) (not shown), and the document reading operation is terminated in the flow 1117.

  In accordance with the control flow as described above, the white LED array light source is controlled to be turned on only in the document area, the shading correction is performed for each document size, and the document is read, so that the light is influenced by the influence of the cosine fourth law and vignetting. It is possible to improve the light distribution characteristic of the original illumination light that decreases as the distance from the axis increases, and to perform optimum image reading.

  In FIG. 13, a B5R size document (1307), an A4R size document (1306), a B5 / B4 size document (1305), and an A4 / A3 size document (1304) are set to the butting reference (1303). The light distribution characteristic (1301) in which only the original size area is controlled to be turned on and the light distribution characteristic (1302) when the shading correction is performed for each original size are shown. As can be inferred from this figure, even if the shading correction coefficients of all the pixels of the photoelectric conversion element that reads the A4 / A3 size of the maximum width are applied to the B5 / B4 size, the A4R size, and the B5R size, It is obvious that the correction cannot be made, and in an image reading apparatus that illuminates only the document area, the optimum image quality can be read by executing the optimum shading for each document size.

  In addition, a document pressure plate or a document conveying device for pressing the document so as not to float is normally used as the image reading device. In the embodiment of the present invention, it has been described that only the document area is illuminated by the document illumination means. However, in practice, if the document pressure plate is in a closed state, light leaking from outside the document area of the document illumination means is also given to the operator. There is little impact.

  FIG. 14 illustrates the difference in operation depending on the state of the original platen. In the image reading apparatus (1401) closed with the original document pressure plate (1403) closed, the document (1414) is set in alignment with the abutting reference (1412) on the document table glass (1410). . At this time, when the document size is designated from the operation unit (not shown) and the copy button (1408) is pressed, it is determined from the state of the pressure plate detection lever (not shown) that the document pressure plate is closed, and the white LED array ( 1416) performs lighting control of the entire area (1420). Therefore, the light distribution of the document illuminating means with respect to the document width (1418) is as indicated by 1423. That is, since the light emitting element outside the document area is turned on, shading correction is performed on the entire image reading area in a state where the decrease in the amount of light at the edge of the document is minimized, and the document is scanned. (Same as the conventional method).

  On the other hand, in the image reading apparatus (1402) in a state where the original document pressure plate (1404) is opened, when the document (1406) is set on the document table glass (1407), it is not shown. When the document size is designated from the operation unit and the copy button 1409 is pressed, it is determined from the state of the pressure plate detection lever (1405) that the document pressure plate is released, and the white LED array (1417) is displayed in the document area (1421). ) Lighting control. In the drawing, the lighting control is performed on the area including the area outside the original on the original abutting reference (1413) side.

  Here, reference numeral 1415 denotes an original, and reference numeral 1411 denotes an original table glass. Since the document place scanning width is 1419, the light distribution of the document illumination means (1417) is as indicated by 1424. That is, the amount of light on the document abutting side is the same as when the document illumination means controls lighting of the entire area. However, the opposite side of the document edge is controlled so that the drop in the amount of light is reduced by the light distribution improvement effect by an auxiliary light source (not shown). That is, the lighting control of the document illumination means corresponding to the document area is performed with the document pressure plate (1404) opened, and the lighting control state of the document illumination means corresponding to the document area is similarly corrected by performing shading correction on the document area. At this point, the document is scanned.

(Example 2)
The second embodiment of the image reading apparatus of the present invention will be described below. This configuration achieves the object by changing the following items with respect to the first embodiment.

  The configuration of the document illumination means is detected by a white LED that can irradiate an irradiation spot on the edge of each document size, and a white LED that can irradiate the irradiation spot on the inside of the document near the edge of the document. By adjusting (switching) the current of the corresponding document edge irradiation light source according to the document size and increasing the illumination light quantity at the document edge, the drop in the edge light quantity is improved.

  As the current setting means for the white LED array, the lighting control circuit is used as a current control resistor switching circuit to perform light amount control.

  Hereinafter, the configuration of the document illumination unit will be described with reference to FIG. FIG. 15A is a diagram for explaining a lighting control circuit for a white LED for illuminating a document. Reference numeral 1501 denotes a white LED element. A switch transistor 1502 turns on / off the current flowing through the white LED. The amount of light emitted from the white LED is limited by the current control resistor existing between the white LED and the transistor 1502. If the resistance value is small, the amount of light emitted from the white LED increases. The amount of emitted light decreases. Reference numeral 1504 denotes a shift register (D flip-flop) for transferring the selection signal of the white LED array, and transfers the white LED selection data (1506) in synchronization with the transfer clock (1507). The data set in the shift register (1504) continues to be held in the same state unless the reset signal (1505) is input, the transfer clock (1507) does not advance, or the power supply (not shown) is stopped.

  After the data has been transferred to each shift register (1504), when the LAMP lighting signal (1508) is supplied with an active “H”, the AND circuit ( The output of 1503) is held at “H”, and the transistor (1502) is turned on. That is, the white LED array is turned on. r1 represents the standard resistance of the white LED. FIG. 15- (b) shows a lighting control circuit including a current setting circuit which is a light amount adjusting means of the white LED. Blocks indicated by reference numerals 1509, 1512, and 1513 are respectively the white LED control circuits at the respective document edge portions or in the vicinity thereof.

The current setting circuit of the white LED 1509 has three resistors r1, r2, and r3 indicated by 1511 by ON / OFF control of the transistor 1502.
r1,
r2,
r3,
r1 · r2 // (r1 + r2) = r1 / 2 (where r1 = r2)
r1 · r3 / · (r1 + r3),
r3 · r2 // (r3 + r2),
r1 · r2 · r3 / (r2 · r3 + r3 · r1 + r1 · r2) = r1 / 3
(However, r1 = r2 = r3)
The following 7 combined resistors can be selected.

  That is, setting data for selecting three resistors r1, r2, and r3 can be transferred when the document size is determined, and the illuminance of the irradiation spot light at the document edge can be increased. In the above example of the resistance value, when r1 = r2 = r3, the resistance value is 1/2 when the two resistors are ON, and the resistance value is 1 / ON when the three resistors are ON. It becomes 3. That is, the current flowing through the white LED can be set between 1 to 3 times, and the light amount can be controlled. Further, FIG. 10 shows the connection order of serial data. In this method, by assembling with the configuration shown in 1007_2, only r1 is selected at the time other than the document edge portion, It is also possible to adjust to an equivalent light emission amount. Hereinafter, the same effect is obtained by using the above-described original illuminating means and controlling lighting of the lighting area of the original illuminating means based on the original size detection result, performing shading correction in the same lighting area, and executing original scanning. Is obtained.

It is a block diagram of this image reading apparatus. The figure explaining the influence by a cosine fourth power rule and vignetting. The figure explaining the relationship between a document illumination means and a document size. The figure explaining the light distribution example by the original document illumination means. The figure which shows the structural example of the original illumination means of this invention. 4 is a light distribution example for each document size illuminated by the document illumination unit of the present invention. FIG. 6 is an example showing two document illumination controls according to the present invention. FIG. FIG. 3 is a diagram illustrating a circuit configuration of a document illumination unit according to the first embodiment. The figure which shows the setting method of the lighting control data of the original illumination means of 1st Example. The block diagram which shows the structural example of the auxiliary light emitting element of a document illumination means. The flowchart explaining operation | movement of this invention. The graph which shows the attenuation amount of the light quantity by a cosine fourth power law. The figure which shows the relationship between document area illumination by this invention, light distribution, and shading correction. The figure explaining the control which switches the lighting area | region of a document illumination means according to the state of a document pressure plate. The figure which shows the circuit structure of the original illumination means of a 2nd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Controller of image reading apparatus 102 Image reading means 103 Light source (original illumination means)
104 Document conveying means 105 Optical motor / control circuit 106 Document size detecting means 107 DF open / close SW (pressure plate detecting means)
108 Photoelectric conversion means (CCD, CIS)
109 A / D conversion means 110 Lamp control means 111 Light emitting element selection means 112 CPU
113 Transmitter 114 CPU built-in RAM
115 EEPROM
116 External RAM
117 External ROM
118 Address / Data Bus 119 Signal Processing Means 120 Transmitter for Signal Processing Means 121 Pulse Generation Means 122 Image Processing Means Including Shading Means 123 Storage Means 124 Data Output to Image Forming Apparatus 307 Document Constructed with White LED Array Illuminating means 303 to 306 Document size detection sensor 308 Auxiliary light source 516 Example of original illuminating means composed of a white LED array formed in a staggered configuration and an auxiliary light source 701 Shading plate (white reference plate)
801 White LED
802 Transistor 803 AND circuit 804 Shift register (D flip-flop)
805 Auxiliary light source with two white LEDs 1401 and 1402 Image reading devices 1403 and 1404 Original platen 107, 1410 and 1411 Original platen glass 1408 and 1409 Copy button 1425 Image forming device

Claims (20)

  Document illumination means (line light source) composed of a plurality of light emitting elements, photoelectric conversion means for reading reflected document light, document size detection means, document area lighting control means corresponding to the main scanning area of the detected document size, In an image reading apparatus configured to include a shading correction unit and an operation unit, an auxiliary illumination unit for supplementing the amount of light for each document size is provided at the edge of the set document. An image reading apparatus using the document illumination means to perform shading correction and document scanning in a lighting control state of only the document area.   2. The image reading apparatus according to claim 1, wherein, for each document size detected by the document size detecting means, the vicinity of the center of the light emitting element irradiation spot with respect to the document edge (edge) (a portion with a large amount of irradiation light). An image reading apparatus using document illuminating means in which a light emitting element is arranged so as to be applied.   2. The image reading apparatus according to claim 1, wherein an area corresponding to the document size set by the operation unit is controlled to be turned on, and the center of the light emitting element irradiation spot with respect to the document edge (edge) for each document size. An image reading apparatus using a document illuminating unit in which a light emitting element is arranged so as to be in the vicinity (a portion with a large amount of irradiation light).   2. The image forming apparatus according to claim 1, wherein the shading correction means has line memory means for one main scanning line or for a standard document type.   2. The image reading apparatus according to claim 1, wherein the light emitting element constituting the original illumination means is a white LED.   2. An image reading apparatus according to claim 1, wherein the lighting control of the original edge auxiliary illumination means corresponding to the area from the reference position of the original illumination means to the original edge relative to the main scanning width of the original is provided. An image forming apparatus characterized by performing shading correction and document scanning in a document area.   In the image reading apparatus according to claim 1, as the lighting area of the document illuminating means after the document size is detected, the document abutting reference side illuminates the outside of the document region sufficiently and corresponds to the region up to the document edge. An image forming apparatus characterized by performing lighting control of a document edge auxiliary illumination means for performing shading correction and document scanning in a document area.   2. The image reading apparatus according to claim 1, wherein the document illumination unit is configured as a light emitting element array configured in a plurality of rows parallel to the main scanning direction, and constitutes the document illumination unit on the document scanning line. The illumination spots of each adjacent light emitting element are arranged so as to overlap each other, and the auxiliary illumination means arranged at the end of each original size is arranged so as to overlap with the irradiation spots of the light emitting elements located at the end of the original. An image reading apparatus characterized by that.   9. An image reading apparatus according to claim 8, wherein a document illumination light source means constituting said document illumination means and a transfer register for transmitting a lighting control signal of said auxiliary illumination means are serially connected. Reader.   10. The image reading apparatus according to claim 9, wherein the transfer order of the transfer registers of the document illuminating means and the auxiliary light source means is such that the document illuminating means is transferred before the auxiliary light source means. Reader.   11. The image reading apparatus according to claim 10, wherein after the register reset signal is set for the document illuminating means, only the lighting control signal for the auxiliary light source means is lit to detect the document main scanning width. Reader.   12. The image reading apparatus according to claim 11, wherein the main scanning document width is determined from the read value of the photoelectric conversion means using the auxiliary light source means, and the sub-scanning document width is detected by the reflection type document size detection sensor. An image reading apparatus for detecting a document illumination area (document size) by means of   Document illumination means (line light source) composed of a plurality of light emitting elements, photoelectric conversion means for reading reflected document light, document size detection means, document area lighting control means corresponding to the main scanning area of the detected document size, In an image reading apparatus having a shading correction unit and an operation unit, a light amount control unit of a neighboring light emitting element that illuminates an edge of a set original is provided so that only the original region is in a lighting control state. An image reading apparatus characterized by performing shading correction and document scanning.   14. The image reading apparatus according to claim 13, wherein the light emitting element constituting the original illumination unit is a white LED.   14. The image reading apparatus according to claim 13, wherein after the document size is determined by the document size detecting means, the control means for adjusting the amount of light emitting elements that irradiates the edge of the document, and the shading correction in the set document area. And an image reading apparatus that performs document scanning.   16. The image reading apparatus according to claim 15, wherein the amount of light emitted from the light emitting element that irradiates the vicinity of the end portion of the detected document is adjusted in a brighter direction.   Document illumination means (line light source) composed of a plurality of light emitting elements, photoelectric conversion means for reading reflected document light, document size detection means, document area lighting control means corresponding to the main scanning area of the detected document size, In an image reading apparatus having a shading correction means and an operation means, the original illumination area is controlled based on the result of the opening / closing operation (state) detection means of the original pressure plate or the original conveying means and the set original size. An image reading apparatus characterized by that.   18. In the image reading apparatus according to claim 17, in the case where the document scanning is executed with the document pressure plate or the document conveying means closed, the document illumination means is lit in the entire area regardless of the detected document size. An image reading apparatus characterized in that shading correction is performed, and the document illuminating means scans the document while all areas (all light emitting elements) are turned on.   In the image reading apparatus according to claim 17, when the original platen or the original conveying unit performs the original scanning with the original platen or the original conveying unit being opened, the lighting area of the original illuminating unit is adjusted according to the detected original size, An image reading apparatus characterized in that shading correction and document scanning are performed while the document illumination means is lit in an area corresponding to the document size.   20. The image reading apparatus according to claim 19, wherein the document illuminating means has an auxiliary light source for the document edge corresponding to the document size, and the document illuminating means in the document region and the selected auxiliary light source during shading adjustment and document scanning. An image reading apparatus characterized by turning on a light source.

Images