JP3995400B2 - Document reader - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for adjusting a light amount of a light source of a document reading device in an image forming apparatus.
[0002]
[Prior art]
There are two methods for reading a document: a document moving method and a document fixing method. In recent years, a document reading device having both methods is often used to make the device compact. In such a reading method, there has been a problem that the optical unit including the platen glass is distorted due to the amount of heat generated from the light source for irradiating the document, and the reading accuracy is changed.
[0003]
In particular, in the document moving method in which the optical unit is fixed and read, a problem occurs greatly. In order to reduce the heat generated from the light source, the document passes through the reading unit in synchronization with the document transport timing of the document reading device. There is also an apparatus which is controlled so as to irradiate the light source only occasionally.
[0004]
For example, in Japanese Patent Laid-Open No. 9-212066, when the temperature of each unit of the image forming apparatus rises above a predetermined temperature, a fan is operated to lower the temperature of the raised unit, thereby cooling air. A configuration has been proposed in which the temperature is lowered by generating a flow.
[0005]
Further, as a prior art in which this method is applied to an optical unit, a technique for controlling the operation of a fan using a nonvolatile RAM and keeping the temperature in the optical unit constant is disclosed in Japanese Patent Laid-Open No. 5-333627. Has been.
[0006]
[Problems to be solved by the invention]
As described above, the conventional technique does not prevent the temperature of the optical unit itself from increasing, but merely discloses a technique or method for decreasing the temperature increased in the optical unit. Conventionally, it is difficult to say that this is a fundamental temperature rise prevention measure.
[0007]
In addition, in the above two conventional examples, a sensor for detecting the increased temperature of the optical unit and a control circuit for comparing the detected value with the normal value (reference value) are required. The size of the apparatus is increased and the contents of the control are complicated, which increases the cost.
[0008]
Furthermore, the provision of a fan increases the possibility of sucking dust and dust from the outside of the device, and these foreign substances adhere to the mirror and lens, causing streaks in the image and reducing the image quality. There was a thing.
[0009]
Further, in the method of turning on the light source only at the time of reading a document, even if the temperature rise can be slightly reduced, the light amount changes due to the ON / OFF operation of the light source, and it becomes difficult to obtain a stable light amount. There was a difficulty.
[0010]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide an original reading apparatus capable of suppressing the heat generation phenomenon itself of an optical unit.
[0011]
[Means for Solving the Problems]
In the present invention, means for solving the above-described problems are configured as follows.
[0012]
(1) Document fixing type document reading process for reading an image of a document stationary on the first document table while moving an exposure light source below the first document table, and moving on the second document table A document moving apparatus that selectively reads an image of a document that is being read by stopping the exposure light source at a predetermined position below the second document table;
An input voltage to the exposure light source at the time of the document movement type document reading process is set lower than an input voltage to the exposure light source at the time of the document fixing type document reading process,
The level of light applied to the original from the exposure light source during the original moving type original reading process is substantially equal to the level of light applied to the original from the exposure light source during the original fixing type original reading process. With a depth of focus A condensing lens for condensing the irradiation light on the original from the exposure light source at the predetermined position on the original reading position on the second original table, the original reading position on the second original table and the predetermined position So that the amount of light applied to the original on the second original plate by the exposure light source at the predetermined position does not become insufficient due to a decrease in the input voltage to the exposure light source. It is characterized by.
[0022]
(2) The input voltage to the exposure light source at the time of the document movement type document reading process is set to 80% of the input voltage to the exposure light source at the time of the document fixing type document reading process. To It is characterized by setting.
[0023]
(3) The condensing lens is Document reading position on the second document table It arrange | positions in the position which does not block the optical path of the received light image information from.
[0024]
According to this configuration, by arranging a condensing lens between the light source and the document reading position, only the irradiation light on the document surface is collected, and the illuminance on the document surface without affecting the received light image information. Can be improved.
[0025]
(4) The condenser lens is As the second document table It is configured to be shared with platen glass.
[0026]
According to this configuration, it is possible to reduce the size of the mechanism and simplify the configuration by integrating the platen glass together with the condenser lens, rather than arranging the condenser lens alone (independently). it can.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
A document reading apparatus according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of an image forming apparatus, and a document table 21 made of transparent glass or the like is provided at the top of the apparatus. A scanner optical system 100 is disposed below the document table 21. The scanner optical system 100 converts an exposure light source 22 for irradiating light on a document (not shown) placed on a document table 21 and reflected light from the document, for example, a one-dot chain line in the figure. As shown in FIG. 2, a reflecting mirror 23 composed of a plurality of mirrors led to a photoelectric conversion element (CCD) 25 disposed on the other side (right side) through the imaging lens 24 in the scanner optical system 100, and in the optical path The imaging lens 24 and the CCD 25 are provided. A movable document reading apparatus 500 (not shown in FIG. 1) shown in FIG. 2 is mounted on the upper part of the apparatus main body. The document reading unit 200 is configured as described above.
[0033]
The original image data read by the CCD 25 is subjected to image processing, and then a laser scanning unit (hereinafter referred to as LSU 30) irradiates the surface of the photosensitive member 26 with laser light to form an electrostatic latent image. . The photoconductor 26 has a drum shape that is driven to rotate counterclockwise. Around the photoconductor 26, a laser beam is emitted from a laser irradiation point toward the rotation direction (counterclockwise) of the photoconductor 26 by a laser. A developing device 27 that develops the electrostatic latent image on the exposed surface of the photoconductor 26 into a visible image with toner, a transfer charger roller 28 that transfers the toner image on the photoconductor 26 to a sheet, and the photoconductor 26 at a predetermined potential. A main charger 29 for charging, an LSU 30 for irradiating the laser toward the laser irradiation point of the photosensitive member 26, and the like are sequentially provided. Thus, the image forming unit 300 is configured.
[0034]
Further, the transfer paper P is stored in the paper tray 31, and a pickup roller 32 for feeding the transfer paper P is disposed at the front end of the paper tray 31, and is directed toward the downstream side (for convenience, transfer Based on the input sensor switch 33 for detecting the passage of the transfer paper P and the detection signal from the input sensor switch 33, the flow of the paper P (the paper feed tray) is upstream and the paper discharge side is downstream. The PS roller 34 for aligning the toner image on the photoconductor 26 and the transfer paper, the transfer charger 28 for transferring the toner image on the photoconductor 26 to the transfer paper P, and the toner image on the transfer paper P are heated. The fixing roller 35 for fixing the sheet, the sheet discharge detection switch 36 for detecting the passage of the transfer sheet P at the position immediately before the sheet discharge, and the sheet discharge roller 37 for discharging the transfer sheet P are disposed. The transfer paper P is discharged to the side of the image forming unit 300 and discharged forward from the lower part of the document reading unit 200. Note that 39 is a manual feed tray and 40 is a pickup roller. The paper transport system 400 is configured as described above.
[0035]
Next, the configuration of the movable document reading apparatus 500 mounted on the upper part of the apparatus main body will be described with reference to FIG. That is, a document tray 1 on which a document to be read is placed is provided in an inclined state in the upper part of the apparatus, and a document feeder 9 including a pickup roller 2 and a separating plate 3 is disposed at the downstream end thereof. The document feeder 9 is connected to a main conveyance path 4 formed to be curved in a substantially arc shape downward, and a document entry sensor 5 is provided at an intermediate portion thereof. On the side, a PS roller 6 is provided.
[0036]
A strip-shaped platen glass 7 is provided at the downstream end of the main conveyance path 4, and a document pressing plate 8 is close to the platen glass 7 in a state where it is urged downward by a spring 81. Is provided. A paper discharge conveyance path 10 inclined upward is connected to the downstream side of the platen glass 7, and a conveyance roller 13 is provided in the middle of the paper discharge conveyance path 10.
[0037]
A reverse discharge paper discharge roller 14 is provided at the downstream end of the paper discharge conveyance path 10, and an intermediate tray swinging operation is performed between the paper discharge roller 14 and the intermediate tray 16. A plate 15 is provided, and a document discharge tray 17 is provided below the intermediate tray 16. A sub transport path 18 extending from the downstream side of the paper discharge transport path 10 to the main transport path 4 is formed.
[0038]
The document reading mode configured as described above will be described. When reading by the document moving method is selected, the first carriage 11 having the light source 22 and the first mirror 231 and the second and third mirrors 232 are read. , 233 move from the home position H1 set at the left end to the home position H2 of the document movement type document reading apparatus 500 provided at the right end, and the home position until the reading of the requested number of sheets is completed. Wait at H2.
[0039]
In this document movement type document reading apparatus 500, the documents placed on the document tray 1 are conveyed one by one to the main conveyance path 4 by the document feeding unit 9 constituted by the pickup roller 2 and the separating plate 3. The After the conveyed document is confirmed by the document input sensor 5, the document is temporarily stopped by the PS roller 6 arranged for adjusting the leading edge of the document and the image reading timing, and then conveyed again in a timely manner. When the document passes through the document reading section (platen glass 7 and document pressing plate 8) 19, the document is irradiated by the light source 22, and the image information of the document is read by the CCD 25 via the reflecting mirror 23 and the imaging lens 24. The image information is subjected to image processing by a control unit (not shown).
[0040]
The document read in this way passes through the discharge roller 14 that can rotate in the reverse direction of the paper discharge section via the conveyance roller 13, and the position of the intermediate tray swing plate 15 (at the home position MH1 and the home position MH2). The document transport direction is determined by any one of them, and the document is transported to the intermediate tray 16 or the document discharge tray 17.
[0041]
Next, the “single-sided reading process” performed by the mobile document reading apparatus 500 having such a configuration will be described based on the flowcharts of FIGS. 3 and 4.
[0042]
First, after a print request (S401), printing conditions such as the number of prints, magnification, paper size, single-sided printing, etc. are input (in this case, “single-sided printing” is selected) (S402) Is placed on the document tray 1, document reading processing is started (S404). Details of the single-sided document reading process (S404) are shown in FIG.
[0043]
First, when single-sided reading processing is selected (because “single-sided printing” is selected), the process proceeds to S501 in FIG. 4 and whether the intermediate tray swinging plate 15 of the document discharge unit is at the home position MH1. It is determined whether or not (S501). At this time, the home position MH1 is indicated by a solid line in FIG. 2. When the home position MH1 is set at this position, the document after reading is led out to the document discharge tray 17.
[0044]
In S501, when the intermediate tray swing plate 15 is not at the home position MH1, the intermediate tray swing plate 15 is moved to the home position MH1 (S509). As described above, after the position of the intermediate tray swinging plate 15 is determined, the document is conveyed by the document feeding pickup roller 2 (S502), and is temporarily stopped by the PS roller 6 (S503). At the same time, the document is conveyed again (S504).
[0045]
The conveyed document is read by the document reading unit 19 (S505). It is determined whether or not the document read at this time is input to the memory in the control unit (S506). This determination is made by setting the number of single prints or multiple prints when the number of prints is set in S402.
[0046]
In S506, multi-printing is indicated when a memory input is performed, and single printing is indicated when image information of a document read without performing memory input is processed by the control unit and then transmitted to the laser light emitting unit of the image forming unit. (S510). As described above, during the image processing, the document is conveyed to the discharge roller 14 that can be rotated in the reverse direction via the conveyance roller 13, and the rotation in the document discharge direction and the intermediate tray swinging plate 15. Are led out to the document discharge tray 17 (S507).
[0047]
The single-sided original is read by the operation of the original conveying mechanism and the original reading unit 19. Needless to say, “single-sided printing” includes not only the case where the image information to be read is only on one side, but also the case where the user's reading request is for single-sided reading even when there is image information on both sides.
[0048]
Next, “double-sided reading processing” by the movable document reading apparatus 500 will be described with reference to FIGS. 3 and 5.
First, when the double-sided reading process is selected in the original reading process (S404), the process proceeds to S601 in FIG. 5, where the double-sided original is conveyed by the pickup roller 2 and temporarily stopped by the PS roller 6 as described above. (S602). Next, it is determined whether or not the intermediate tray swing plate 15 is at the home position MH2 (S603).
[0049]
At this time, the home position MH <b> 2 is indicated by a broken line in FIG. 2. When the home position MH <b> 2 is set at that position, the document after reading is led out to the intermediate tray 16. If the intermediate tray swing plate 15 is not at the home position MH2 in S603, the intermediate tray swing plate 15 is moved to the home position MH2 (S624). As described above, after the position of the intermediate tray swinging plate 15 is determined, the document is conveyed again in accordance with the document reading timing (S604).
[0050]
For the conveyed document, the image information of the document on the front side of the document is read by the document reading unit (S605). At this time, the image information of the read front document is input to the memory in the control unit (S606), and the stored image information of the front document is in an image-processed state.
[0051]
As described above, during image processing and memory, the document is conveyed to the discharge roller 14 that can be rotated in the reverse direction via the conveyance roller 13, and the rotation in the document discharge direction and the position of the intermediate tray swing plate 15. To the intermediate tray 16 (S607). The document guided to the intermediate tray 16 is temporarily stopped in a state where the rear end in the document transport direction is sandwiched between the discharge rollers 14 that can be rotated in the reverse direction (S608). The above is the “front document reading conveyance process”.
[0052]
Thereafter, the reversely rotatable paper discharge roller 14 rotates in the direction opposite to the rotation direction in S607, whereby the document is conveyed to the main conveyance path 4 via the sub conveyance path 18 (S609). The transported document is temporarily stopped by the PS roller 6 (S610), and is transported again in accordance with the document reading timing (S611). For the conveyed document, the document reading unit 19 reads the image information of the back document of the document (S612). At this time, the read image information of the read back side document is transmitted to the laser light emitting unit of the image forming unit 300 after image processing in the control unit (S613).
[0053]
As described above, while image processing is performed and image information is transmitted, the document is conveyed to the discharge roller 14 that can be rotated in reverse via the conveyance roller 13, and the rotation in the document discharge direction and the intermediate tray are performed. Depending on the position of the swing plate 15, it is guided to the intermediate tray 16 (S614). The document guided to the intermediate tray 16 is temporarily stopped in a state where the rear end in the document transport direction is sandwiched between the discharge rollers 14 that can be rotated in the reverse direction (S615). The above is the “reverse document reading and conveying step”.
[0054]
Further, the document once stopped is transported through the sub-conveying path 18 by the reverse rotation of the discharge roller 14 which is reverse to the rotation direction in S614 (S616). A determination is made as to whether or not the trailing edge of the document conveyed in this way has passed through the document input sensor 5 (S617).
[0055]
At this time, when the trailing edge of the document passes and there is a next document (S618), the next document is conveyed by the document feed pickup roller 2 (S619), and is temporarily stopped by the PS roller 6 (S620). Wait until the read timing comes. In this way, the original after the front and back sides are read is conveyed along the main conveyance path 4 even during the conveyance of the next original.
[0056]
When the document transported in this way passes through the paper input sensor 5, it is determined whether or not the intermediate tray swinging plate 15 of the document discharge unit is at the home position MH2 (S621). At this time, since the intermediate tray swinging plate 15 is located at the home position MH2 in S603, it moves to the home position MH1 (S625).
[0057]
In this way, the position of the intermediate tray swing plate 15 is determined. Also during this time, the document is transported and transported via the transport roller 13 to the discharge roller 14 that can be rotated in the reverse direction. The document is ejected by the rotation in the document discharge direction and the position of the intermediate tray swinging plate 15. It is discharged to the paper tray 17 (S623).
[0058]
At this time, as described above, once it is confirmed that the next original that has been waiting on the PS roller 6 has passed through the original reading unit 19 (S622). The document is conveyed and read. The above is the “original empty transport process”.
[0059]
A double-sided original is read by such operations of the original conveying mechanism and the original reading unit. The double-sided original reading process includes three original conveying processes: a “front-side original reading conveying process”, a “back-side original reading conveying process”, and an “original empty conveying process”.
[0060]
The reason for performing these three transport steps is that two steps for document reading are naturally necessary, but after the “back side document read transport” step, the position of the intermediate tray swing plate 15 is moved. When the original is discharged to the original discharge tray 17, when placing a plurality of originals, the front and back order of the originals do not match and the pages cannot be aligned. In order to eliminate such an inconvenience, a process of “empty conveyance of the original” is provided so that the pages can be neatly arranged.
[0061]
On the other hand, the reading operation in the document fixing method is as follows.
The light source 22 for exposure, the first carriage 11 having the first mirror 231 and the second carriage 12 having the second and third mirrors 232 and 233 are waiting at the home position H1 set at the left end position in FIG. .
[0062]
In accordance with the reading start command, the first and second carriages 11 and 12 accelerate until reaching a moving speed corresponding to the required copy magnification, move at a predetermined speed, and are placed on the document table 21. Read the placed document. At that time, the wire and pulley (not shown) are set so that the second carriage 12 moves at half the speed of the first carriage 11, and both the carriages 11 and 12 move according to the required document size. Then, after reading, the robot moves in the reverse direction and returns to the home position H1.
[0063]
In the document reading unit 200 having the document moving / fixing combination configured as described above, the document moving type belt-shaped platen glass 7 may be touched by the user, and in this case, the temperature is 65 ° C. or higher. If is rising, human cells may be destroyed, which is a problem. Therefore, conventionally, it has been necessary to add a member such as a cooling fan as a measure for preventing a temperature rise near the light source 22.
[0064]
On the other hand, in the document fixing method, since the light source 22 repeatedly moves, the temperature rise of the document table (platen glass) 21 is lower than that in the document movement method, and the temperature on the platen glass 20 is maintained even when a rated voltage is input. There is no problem because the temperature does not rise to 65 ° C.
[0065]
However, in the document moving system, when 100V is input, the temperature on the platen glass 7 exceeds 65 ° C. Therefore, in the present embodiment, when reading in the document movement type is selected, the input voltage of the light source 22 is set lower than the input voltage in the document fixing type. Specifically, 100V is input when the original is fixed, and 80V is input when the original is movable.
[0066]
FIG. 6 shows a change in temperature on the platen glass 7 of the document moving system for each input voltage of the light source 22, and FIG. 7 shows a change of the temperature of the document table 21 of the document fixing system. In the document moving method, the temperature rise is also lowered by lowering the input voltage to the light source 22, and when 80V is inputted, the temperature on the platen glass 7 can be generally suppressed to 65 ° C. or lower. On the other hand, in the document fixing method, the platen glass 20 has a large surface area, and even when 100 V is input, the temperature is about 50 ° C., and there is no problem.
[0067]
As described above, the temperature of the platen glass 7 of the document moving method is set by setting the light source light amount of the optical unit when reading the document using the document moving method to be lower than the light source amount when reading the document using the document fixing method. The rise can be suppressed, and if it touches the hand, it will improve the safety of the user so that it will not burn, and it will cause deformation of surrounding parts due to the temperature rise, variation in mounting accuracy due to heat, etc. Therefore, it is possible to obtain a stable and high quality read image.
[0068]
FIG. 8 shows a configuration of a different embodiment. In this case, an optical unit (first carriage) provided with a light source 22, a first reflector 41, a first mirror 231, and an inverter (not shown) for lighting the light source 22 is provided. 11 is located at the right end of FIG. 1 and stands by at the document reading position of the document moving method. A platen glass 7 is provided above the optical unit 11, and the original G to be read is conveyed on the platen glass 7 in the direction of the arrow in the figure.
[0069]
The input voltage of the light source 22 is set to 80 V as described in the previous embodiment, and direct light from the light source 22 and indirect via the first reflector 41 are placed at the document reading position on the platen glass 7. Light is irradiated, and the reflected light of the original G is folded back by the second and third mirrors 232 and 233 (see FIG. 1) positioned further leftward through the first mirror 231 and passes through the imaging lens 24. An image is formed on the surface of the CCD 25.
[0070]
In this case, since the input voltage of the light source 22 is set to 80V, there is no problem because the temperature rise can be suppressed low, but the light amount of the light source 22 is lower than the light amount at the input 100V when the original is fixed. As the amount of light decreases, the amount of light applied to the CCD 25 also decreases in proportion to this, and the output voltage of the CCD 25 decreases. Noise is generated on the CCD substrate due to various factors, and the noise component appears to have a constant magnitude. Therefore, when the output of the CCD 25 is lowered, the influence of the noise increases and the S / N ratio is deteriorated. When the S / N deterioration is significant, the reproducibility of the read image is affected and the image quality is lowered.
[0071]
Therefore, in the present invention, as shown in FIG. 8, the second reflector 43 is formed on the apparatus exterior frame 42 at the reading position by the document movement method, and the indirect light via the second reflector 43 is also transmitted to the platen glass 7. The light is focused on the reading position above. As a result, even when the input voltage of the light source 22 is 80 V, the illuminance on the original surface can be equivalent to that when the original is fixed, and the heat generation phenomenon can be suppressed.
[0072]
By the way, in the comparative example shown in FIG. 9 (conventional case), in the document moving method, the trailing edge of the document G is lifted, and when the ratio of the direct light of the light source 22 is large, lizard is generated, which affects the image. To do. In the present embodiment, as described above, indirect light from the second reflector 43 increases, so that the ratio of indirect light in the amount of light irradiated to the reading position increases as shown in FIG. It becomes possible to eliminate the lizard. In other words, since the amount of indirect light is larger than the amount of direct light, the generation of lizards can be eliminated.
[0073]
FIG. 11 shows another embodiment. In this case, a condensing lens 45 is arranged in the vicinity of the document movement type reading position, and the irradiation light from the light source 22 is condensed at the reading position on the platen glass 7. The illuminance at the irradiation point a on the reading surface is improved. That is, the condensing lens 45 is disposed at an intermediate position between the light source 22 and the irradiation point “a” of the original G.
[0074]
In such a configuration, the illuminance at the reading position (irradiation point a) through the condensing lens 45 disposed between the platen glass 7 decreases the input voltage to the light source 22 as shown in FIG. However, it is possible to ensure sufficient document surface illuminance (irradiation light amount) to obtain a good image.
[0075]
As shown in FIG. 12, by selecting the depth of the condenser lens 45, the irradiation light can be improved to the level of 1 ′ (symbol ●) even when the input voltage is 1 (symbol ○). Since the input voltage is low, the S / N ratio is significantly reduced. When the S / N is significantly reduced, the reproducibility of the read image is affected and the image quality is lowered. Therefore, it is not preferable to lower the input voltage too much. For example, it is possible to prevent a decrease in the S / N ratio by maintaining a certain height, such as 2, 3, and as a result, good image quality. Can be secured. Specifically, the input voltage is preferably about 80V.
[0076]
In this way, by setting the input to the light source 22 low, it is possible to suppress the temperature rise itself of the light source 22 and improve the safety of the user. Therefore, it is possible to obtain a stable read image by preventing the variation in the mounting accuracy due to, and to suppress a decrease in the S / N ratio and to obtain a good image quality.
[0077]
FIG. 13 shows a further different embodiment. In this case, a condensing platen glass 71 is disposed at the original reading position, and a structure in which a normal platen glass and a condensing lens are used together, and the light emitted from the light source 22 is as follows. Then, the light is condensed at the reading position (irradiation point a) of the original G through the condensing lens portion 171 of the condensing platen glass 71, and the reflected light from the original as shown in FIG. The image is further folded back by the second and third mirrors 232 and 233 positioned in the left direction via the mirror 231 and imaged on the surface of the CCD 25 through the imaging lens 24. At this time, it is assumed that the condensing lens unit 171 collects only the irradiation light from the light source 22 and is set to a position that does not block the reflected light path from the document surface.
[0078]
In this case, the input voltage of the light source 22 is set to 100 V in the document fixing method and 80 V in the document moving method, and the amount of light applied to the document surface is set to be the same level in any reading method as shown in FIG. To do. Thus, by using the condensing platen glass 71 also as the condensing lens, the configuration can be simplified as compared with the case where the single condensing lens 45 as shown in FIG. 11 is arranged. Can be made more compact and less expensive.
[0079]
【The invention's effect】
The present invention structured as described above has the following effects.
[0080]
According to the first aspect, it is possible to reduce the amount of heat generated from the light source by changing the light amount of the light source, to suppress the occurrence of the heat generation phenomenon of the optical unit, and to lower the temperature of the optical unit itself. It is possible to improve the safety, and it is possible to obtain a stable read image by preventing deformation of peripheral parts due to temperature rise and variation in mounting accuracy due to heat, and deterioration of the S / N ratio. Can be suppressed, and good image quality can be obtained.
[0084]
Collection By condensing the irradiation light from the light source with the optical lens, a sufficient irradiation light amount can be obtained with a smaller light source amount. Therefore, the light source quantity itself can be reduced, and the heat generation of the optical unit can be suppressed. It is also possible to prevent the deterioration of the S / N ratio.
[0085]
Claim 2 According to the above, by arranging a condensing lens between the light source and the document reading position, only the irradiation light on the document surface is collected and the illuminance on the document surface is improved without affecting the received light image information. Can be made.
[0086]
Claim 3 Therefore, rather than arranging the condenser lens alone (independently), the mechanism can be miniaturized by integrating it with the platen glass, and the configuration can be simplified.
[0087]
Claim 4 According to the above, by condensing the light source light amount onto the document surface by the condensing lens, it becomes possible to obtain a good image with the minimum necessary light source light amount and to suppress the heat generation of the optical unit itself. . It is also possible to prevent the deterioration of the S / N ratio.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a configuration diagram of the movable document reading apparatus.
FIG. 3 is a flowchart for explaining the document reading operation;
FIG. 4 is a flowchart in the case of the single-sided original.
FIG. 5 is a flowchart in the case of the double-sided document.
FIG. 6 is a graph showing a temperature rise of a platen glass in the document moving method.
FIG. 7 is a graph showing a temperature rise of a platen glass in the document fixing method.
FIG. 8 is a configuration diagram of a main part of a document reading apparatus according to another embodiment of the present invention.
FIG. 9 is an explanatory diagram of a comparative example in which lizard is generated at the trailing edge of the document.
FIG. 10 is an explanatory diagram showing that no rash occurs at the trailing edge of the document.
FIG. 11 is a configuration diagram of a main part of a document reading apparatus according to another embodiment of the present invention.
FIG. 12 is a graph showing the relationship between the input voltage to the light source and the amount of irradiation light.
FIG. 13 is a configuration diagram of a main part of a document reading apparatus according to still another embodiment of the present invention.
[Explanation of symbols]
11-Optical unit (first carriage)
22-Light source
41-reflector (first reflector)
43-reflector (second reflector)
45-condenser lens
100-scanner (scanner optical system)

Claims (4)

A document fixing type document reading process for reading an image of a document stationary on the first document table while moving an exposure light source below the first document table, and moving on the second document table. A document reading apparatus that selectively executes a document moving-type document reading process for reading an image of a document by stopping the exposure light source at a predetermined position below the second document table;
An input voltage to the exposure light source at the time of the document movement type document reading process is set lower than an input voltage to the exposure light source at the time of the document fixing type document reading process,
The level of light applied to the original from the exposure light source during the original moving type original reading process is substantially equal to the level of light applied to the original from the exposure light source during the original fixing type original reading process. A condensing lens for condensing irradiation light on the original from the exposure light source at the predetermined position at the original reading position on the second original table, By arranging between the reading position and the predetermined position, the amount of light applied to the original on the second original plate by the exposure light source at the predetermined position has lowered the input voltage to the exposure light source. A document reading apparatus characterized by preventing the shortage due to the above.   The input voltage to the exposure light source during the document movement type document reading process is set to 80% of the input voltage to the exposure light source during the document fixing type document reading process. Item 2. The document reading device according to Item 1.   3. The document reading apparatus according to claim 1, wherein the condenser lens is disposed at a position that does not block an optical path of received light image information from a document reading position on the second document table.   The document reading apparatus according to claim 1, wherein the condensing lens is configured to also serve as a platen glass as the second document table.

Images