Image reading device

Abstract

To provide an image reading device that prevents a reduction in the accuracy of reading an image caused by electrification of a light guide.SOLUTION: An image reading device comprises: a document table glass on which a document is placed; a platen that is attached to the document table glass in an openable and closable manner; an LED 408 that emits light to irradiate the document; a light guide 207 that guides the light emitted from the LED 408 to the document; an LED array substrate 206 on which the LED 408 is mounted; an image sensor that receives the light reflected on the document to read an image of the document; and a ground pattern 409 that is provided on a surface of the LED array substrate 206 opposite to the document table glass and is grounded. The ground pattern 409 discharges electric charges on the electrified platen.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to an image reading apparatus that reads an image from a document.

Background Art

[0002] An image reading apparatus irradiates light on a document and receives the reflected light to read an image. Patent Document 1 discloses an image reading apparatus having an LED array in which a plurality of light-emitting diodes (LEDs) are linearly arranged on a substrate as an illumination mechanism. Patent Document 2 describes an image reading apparatus having a configuration in which a light guide that guides light emitted from an LED is adhered to the LED and the light irradiated from the LED is condensed on the paper surface of the document with high efficiency.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Generally, an image reading apparatus includes a document table glass on which a document is placed and a pressure plate that presses the document on the document table glass to prevent the document from floating during reading. In such an image reading apparatus, due to user operations such as placing the document and opening and closing the pressure plate, friction and peeling operations between the pressure plate and the document occur. As a result, the pressure plate may become charged.

[0005] When a charged pressure plate is closed while the reading unit, which includes an LED board with LEDs mounted on it and a light guide, is directly below the document glass, the charged pressure plate can inductively charge the light guide. When the light guide becomes charged, a discharge may occur between the light guide and the LED terminals. Furthermore, the discharge from the charged light guide may not be limited to the LED terminals, but may also occur at the wiring of the LED board or the terminals of other mounted electronic components.

[0006] If a discharge occurs at the terminals of an LED or other electronic component, the LED or the semiconductor device that controls its operation may malfunction. If the LED or semiconductor device malfunctions, the image reading device may not be able to obtain sufficient light emission to read the image accurately.

[0007] In view of the above-mentioned problems, the primary objective of the present invention is to suppress the decrease in image reading accuracy caused by the light guide becoming charged. [Means for solving the problem]

[0008] The image reading device of the present invention comprises a document glass on which a document is placed, a pressure plate that is attached to the document glass so as to be openable and closable, a light-emitting means for emitting light to irradiate the document, a light guide for guiding the light emitted from the light-emitting means to the document, a substrate on which the light-emitting means is mounted, a light-receiving means for receiving reflected light from the document and reading an image of the document, and a grounding pattern provided on the surface of the substrate facing the document glass and grounded, wherein the grounding pattern discharges the charge of the charged pressure plate. [Effects of the Invention]

[0009] According to the present invention, it is possible to suppress the decrease in image reading accuracy caused by the light guide becoming charged. [Brief explanation of the drawing]

[0010] [Figure 1] Configuration diagram of the image reading device. [Figure 2] Diagram illustrating the configuration of the reading unit. [Figure 3] Controller diagram. [Figure 4] Detailed diagrams illustrating the LED array substrate and LED control substrate. [Figure 5] (a) and (b) are detailed diagrams of the LED array unit. [Figure 6] Cross-sectional view of the LED array unit at line A-A'. [Figure 7] Diagram illustrating the second example of an LED array unit. [Figure 8] (a) and (b) are explanatory diagrams of the third example LED array unit. [Figure 9] Diagram illustrating the fourth example of an LED array unit. [Modes for carrying out the invention]

[0011] Preferred embodiments of this invention will be described in detail below with reference to the drawings.

[0012] (Image reading device) Figure 1 is a diagram showing the configuration of the image reading device according to this embodiment. The image reading device 100 comprises a reading unit 101, a belt 102, a motor 103, a document glass 104, and a pressure plate 105. The belt 102 is rotationally driven by the motor 103, moving the reading unit 101 in the direction of the arrow (scanning direction). The document 106 is placed on the document glass 104 and pressed down by the pressure plate 105. The pressure plate 105 is attached to the document glass 104 so as to be openable and closable. The reading unit 101 reads an image from the document 106 placed on the document glass 104 while being moved in the scanning direction by the belt 102.

[0013] (Reading unit 101) FIG. 2 is a configuration explanatory diagram of the reading unit 101. The reading unit 101 includes an LED array unit 201 as a light emitting unit, a plurality of planar mirrors 202a to 202d, an imaging lens 203, an image sensor 204 as a light receiving unit, and an image sensor substrate 205 on which the image sensor 204 is mounted. The LED array unit 201 includes an LED array substrate 206 on which a plurality of side view type LEDs are mounted as light emitting elements, and a light guide 207 which is a light conductor that guides the light emitted from the LEDs to the document 106.

[0014] The reading unit 101 irradiates the document 106 placed on the document table glass 104 with light by the LED array unit 201. The light is reflected by the document 106. The reflected light by the document 106 is guided to the imaging lens 203 by the planar mirrors 202a to 202d and is imaged on the light receiving surface of the image sensor 204. The image sensor 204 performs photoelectric conversion of the received light and outputs an electrical signal representing the read image. The electrical signal is processed by the image sensor substrate 205 and is converted into image data representing the image of the document and output.

[0015] (Controller) FIG. 3 is an explanatory diagram of the controller of the image reading apparatus 100. The image reading apparatus 100 includes a CPU (Central Processing Unit) 300 as a controller. The CPU 300 controls the overall operation of the image reading apparatus 100. In FIG. 3, a configuration in which the CPU 300 performs light emission control of the reading unit 101 (LED array unit 201) will be described.

[0016] The reading unit 101 includes an LED array substrate 206 and an LED control substrate 302. The LED array substrate 206 is mounted with an LED array 301 in which a plurality of LEDs for irradiating light onto the document 106 are arranged in series. The LED control substrate 302 is mounted with an LED control unit 303. The LED control unit 303 is connected to the LED array 301 and the CPU 300. The LED control unit 303 is an electronic circuit that controls the light emission of each LED in the LED array 301 by supplying the power supplied from the power source to each LED in the LED array 301 based on the LED lighting control signal acquired from the CPU 300.

[0017] (LED array substrate 206 and LED control substrate 302) FIG. 4 is a detailed explanatory diagram of the LED array substrate 206 and the LED control substrate 302. The LED control substrate 302 includes an LED lighting unit 402 and current control units 404, 405, 406 as the LED control unit 303. Power is supplied to the LED control substrate 302 from the power source via a connector 401, and an LED lighting control signal is input from the CPU 300. The LED array substrate 206 includes an LED array 301 composed of a plurality of LEDs 408a to 408l and a ground pattern 409 (wiring pattern for grounding). Power is supplied to the LED array substrate 206 from the LED control substrate 302 via a connector 407. In the LED array 301 of the present embodiment, three rows of a plurality of serially connected LEDs are provided.

[0018] The LED lighting unit 402 supplies the power supplied from the power source to the LED array substrate 206 via a connector 403. At that time, the LED lighting unit 402 controls the supply and cutoff of the power based on the LED lighting control signal. Such an LED lighting unit 402 is composed of a switch circuit such as a FET (Field Effect Transistor) that supplies and cuts off the power.

[0019] Current control units 404, 405, and 406 control the current flowing through the LED array 301. The amount of light emitted from the light illuminating the document 106 must be constant. However, since each LED 408a to 408l has a different forward voltage (VF), controlling only the applied voltage will result in variations in the amount of light emitted. Current control units 404, 405, and 406 suppress such variations in the amount of light emitted by controlling the amount of current supplied to the LED array 301. The number of current control units 404, 405, and 406 is provided in proportion to the number of rows of LEDs in the LED array 301 (LEDs 408a to 408d, 408e to 408h, 408i to 408l). In this embodiment, since there are three rows of LEDs, three current control units 404, 405, and 406 are provided. Current control units 404, 405, and 406 are constant current circuits composed of, for example, operational amplifiers, current limiting resistors, etc.

[0020] The LED array board 206 applies power supplied from the LED control board 302 via connector 407 to the leading LED of each row of the LED array 301. In this embodiment, power is applied to the anode terminals of LEDs 408a, 408e, and 408i. The cathode terminals of LEDs 408d, 408h, and 408l at the rear end of each row are connected to the corresponding current control units 404, 405, and 406 of the LED control board 302 via connector 407. The amount of light emitted from the row of LEDs 408a to 408d is controlled by the current control unit 404 adjusting the current. The amount of light emitted from the row of LEDs 408e to 408h is controlled by the current control unit 405 adjusting the current. The amount of light emitted from the row of LEDs 408i to 408l is controlled by the current control unit 406 adjusting the current.

[0021] In this embodiment, the LED array 301 has a configuration in which three rows of four series-connected LEDs are connected in parallel. The number of series-connected LEDs and the number of LED rows in the LED array 301 can be freely set according to the area to be illuminated. The wider the area to be illuminated, the greater the number of series-connected LEDs and the number of LED rows.

[0022] The grounding pattern 409 is a conductive member connected to the ground of the LED control board 302 via connectors 407 and 403. As a result, the grounding of the LED control board 302 and the LED array board 206 are common.

[0023] (First example of LED array unit 201) Figure 5 is a detailed configuration diagram of the LED array unit 201. The LED array unit 201 has a configuration in which a part of the LED array substrate 206 rests on a part of the light guide 207. As shown in Figure 2, when mounted on the image reading device 100, the light guide 207 is placed below and the LED array substrate 206 is placed on top of it. Figure 5(a) is a view of the LED array unit 201 from the LED array substrate 206 side (top). Figure 5(b) is a view of the LED array unit 201 from the light guide 207 side (bottom). The LED array substrate 206 is, for example, a printed circuit board.

[0024] The LED array unit 201 has electrically grounded grounding patterns 409 on both the upper (first) and lower (second) sides of the LED array substrate 206. The first side of the LED array substrate 206 is the side facing the document glass 104. The second side of the LED array substrate 206 is the side facing the image sensor 204 and is not facing the document glass 104. The grounding pattern 409 on the first side of the LED array substrate 206 is formed in the longitudinal direction of the LED array substrate 206 and is connected to the grounding pattern 409 on the second side of the LED array substrate 206 via through holes. The grounding pattern 409 on the second side of the LED array substrate 206 is connected to the LED control board 302 via a connector 407.

[0025] On the second side of the LED array board 206, LEDs 408a to 408h and wiring patterns 501a and 501b that electrically connect LEDs 408a to 408h are mounted. The rows of LEDs 408a, 408b, 408c, and 408d are connected in series by the conductive wiring pattern 501a. The rows of LEDs 408e, 408f, 408g, and 408h are connected in series by the conductive wiring pattern 501b. Because wiring patterns 501a and 501b are connected in parallel, the rows of LEDs 408a, 408b, 408c, and 408d are connected in parallel to the rows of LEDs 408e, 408f, 408g, and 408h. Wiring patterns 501a and 501b are connected to the LED control board 302 via connector 407.

[0026] Figure 6 is a cross-sectional view of the LED array unit 201 along line A-A'. In Figure 6, since LEDs 408a to 408h in Figure 5(b) are located in approximately the same position when viewed in cross-section, LEDs 408a to 408h are collectively referred to as LED 408. Similarly, wiring patterns 501a and 501b are collectively referred to as wiring pattern 501.

[0027] The light guide 207 is positioned so that the light incident surface 208 faces the light-emitting surface 601 at one end of the side-view type LED 408. The light guide 207 guides the light incident on the incident surface 208 from the LED 408 toward the document 106. The LED 408 has its terminals 602 and a portion of the wiring pattern 501 soldered to it. The grounding pattern 409 formed on the upper surface (first surface) of the LED array substrate 206 does not have solder resist, which serves as an insulating film, applied to it.

[0028] With the above configuration, even if the pressure plate 105 becomes charged due to user actions, the charge accumulated on the pressure plate 105 is discharged through the grounding pattern 409. As a result, the light guide 207 is prevented from being charged by the charge of the pressure plate 105. This prevents discharge from the light guide 207 to the terminals 602 of the LED 408 and the wiring pattern 501, and prevents failure of the LED 408 and mounted components on the LED control board 302. As a result, the image reading device 100 can accurately read the image of the document even when the pressure plate 105 is charged. In other words, it is possible to suppress the decrease in image reading accuracy caused by the charging of the light guide 207.

[0029] (Second example of LED array unit 201) Figure 7 is an explanatory diagram of the second example of the LED array unit 201. This diagram is a cross-sectional view taken along line A-A' in Figure 5. Normally, the wiring pattern 501 is provided on the mounting surface of the LED 408 (the lower side (second surface) of the LED array substrate 206). However, depending on the substrate shape and the amount of wiring, it may be necessary to place the wiring pattern 501 on the upper side (first surface) of the LED array substrate 206, which is the non-mounted surface of the LED 408.

[0030] In this case, solder resist 701 is applied as an insulating film on the wiring pattern 501 located on the first surface of the LED array substrate 206. The application of solder resist 701 suppresses discharge from the pressure plate 105 through the wiring pattern 501 located on the first surface. This suppresses the effect of the pressure plate 105's charge on the wiring pattern 501 and prevents power fluctuations to the LED array 301 due to the charge of the pressure plate 105. Solder resist is not applied to the ground pattern 409 located on the same surface, as explained in Figure 6. With this configuration, the charge accumulated on the pressure plate 105 is discharged through the ground pattern 409, ensuring a discharge path is secured.

[0031] With the above configuration, even if the wiring pattern 501 has to be placed on the document glass 104 side of the LED array substrate 206, the charge accumulated due to the charging of the pressure plate 105 is discharged through the grounding pattern 409. As a result, the light guide 207 is prevented from being charged by the charging of the pressure plate 105. This prevents the light guide 207 from discharging to the terminals 602 of the LED 408 and the wiring pattern 501, and prevents failure of the LED 408 and mounted components on the LED control board 302. As a result, the image reading device 100 can accurately read the image of the document even when the pressure plate 105 is charged. In other words, it is possible to suppress the decrease in image reading accuracy caused by the charging of the light guide 207.

[0032] (Third example of LED array unit 201) Figure 8 is an explanatory diagram of the third example of the LED array unit 201. Figure 8(a) is a view of the LED array unit 201 from the LED array substrate 206 side (top side). Figure 8(b) is a cross-sectional view taken along line A-A' in Figure 8(a).

[0033] In the third example, the grounding pattern 409 on the upper side (first surface) of the LED array substrate 206 is provided so as to cover almost the entire surface of the first surface of the LED array substrate 206. Note that, as in the second example, when the wiring pattern 501 is located on the first surface side of the LED array substrate 206, the grounding pattern 409 is provided so as to cover the area excluding the wiring pattern 501. In this configuration, the discharge effect of the grounding pattern 409 is enhanced. The larger the proportion of the upper surface of the LED array substrate 206 occupied by the grounding pattern 409, the greater the discharge effect.

[0034] (Fourth example of LED array unit 201) Figure 9 is an explanatory diagram of the fourth example of the LED array unit 201. This diagram is a cross-sectional view taken along line A-A' in Figure 5. The LED array substrate 206 is positioned on the surface of the light guide 207 facing the document glass 104. Let Xgide be the length from one end of the LED array substrate 206 to the light-emitting surface 601 of the LED 408, and let Xnongide be the length from the other end of the LED array substrate 206 to the light-emitting surface 601 of the LED 408. The LED 408 is positioned on the other end side of the LED array substrate 206 rather than the center, such that Xgide is longer than Xnongide (Xgide > Xnongide). The LED array substrate 206 is positioned on the surface of the light guide 207 on one end side. The grounding pattern 409 is provided to cover substantially the entire first surface of the LED array substrate 206, similar to Figure 8.

[0035] In this configuration, the area covered by the grounding pattern 409 over the light guide 207 increases. As a result, the possibility of the light guide 207 being electrostatically charged decreases, and discharge from the light guide 207 to the terminal 602 of the LED 408 can be prevented.

[0036] As described above, the image reading device 100 discharges the charge from the charged pressure plate 105 using the grounding pattern 409. This configuration prevents the light guide 207 from becoming charged even if the pressure plate 105 becomes charged due to user actions, and prevents discharge to the terminals 602 of the LED 408 and the wiring pattern 501. This makes it possible to prevent failure of the LED 408 and the mounted components on the LED control board 302 that controls the lighting of the LED 408. For this reason, the image reading device 100 can accurately read the image of the document even if the light guide 207 becomes charged. In other words, it is possible to suppress a decrease in image reading accuracy caused by the light guide becoming charged.

Claims

1. a platen glass on which a document is placed; a pressure plate attached to the document glass so as to be openable and closable; a light emitting means for emitting light to be irradiated onto the document; a light guide that guides the light emitted from the light emitting means to the document; a substrate on which the light emitting means is mounted; a light receiving means for receiving the light reflected by the document and reading an image of the document; a ground pattern provided on a first surface of the substrate facing the platen glass and grounded; The ground pattern discharges electric charges from the pressure plate. Image reading device.

2. The light emitting means is mounted on a second surface of the substrate that does not face the platen glass.

2. The image reading device according to claim 1.

3. The ground pattern is not coated with an insulating film.

3. The image reading device according to claim 2.

4. a wiring pattern for supplying power to the light emitting means is provided on the first surface; The ground pattern is provided so as to cover the entire surface except for the wiring pattern on the first surface.

4. The image reading device according to claim 3.

5. a wiring pattern for supplying power to the light emitting means is provided on the first surface, and the insulating film is applied to the wiring pattern.

4. The image reading device according to claim 3.

6. The ground pattern is provided so as to cover the entire surface except for the wiring pattern on the first surface.

6. The image reading device according to claim 5.

7. one end of the substrate is disposed on a surface of the light guide facing the platen glass; The light emitting means is disposed closer to the other end of the substrate than the one end of the substrate. The image reading device according to any one of claims 1 to 6.

8. The board further includes a connector for connecting to another board on which a control unit for controlling the light emission of the light emitting unit is mounted, the light emitting means controls light emission by power applied from the other board via the connector; The ground pattern is commonly grounded with the other board via the connector.

8. The image reading device according to claim 7.

9. The light emitting means has a side-view type light emitting surface, the light guide is disposed on the substrate so as to face the light emitting surface; the light emitting means and the light guide are mounted on a second surface of the substrate that does not face the platen glass; The light guide guides the light emitted from the light emitting means to the document by going around an end of the substrate.

2. The image reading device according to claim 1.

10. When viewed from a normal direction of the first surface of the substrate, the light guide and the ground pattern overlap, and the light guide and the light emitting means do not overlap.

2. The image reading device according to claim 1.

11. The light guide is provided on a surface of the substrate that does not face the platen glass.

11. The image reading device according to claim 10.

12. When viewed in a direction parallel to a surface of the substrate on which the light emitting means is mounted, the light guide and the light emitting means overlap, and the light guide and the ground pattern do not overlap.

2. The image reading device according to claim 1.

13. The light emitting means includes a plurality of light emitting elements arranged in series in the longitudinal direction of the substrate, The ground pattern is formed in a longitudinal direction of the substrate so as to overlap the light emitting means when viewed from a normal direction of the first surface of the substrate.

2. The image reading device according to claim 1.

14. In the longitudinal direction of the substrate, the length of the ground pattern is longer than the length of the light guide.

2. The image reading device according to claim 1.

15. The light emitting means is configured by connecting a plurality of light emitting elements by a wiring pattern, When viewed in a direction parallel to a surface of the substrate on which the light emitting means is mounted, the light guide and the light emitting means are adjacent to each other, and when viewed in a normal direction of the first surface of the substrate, the light emitting means and the wiring pattern are partially overlapped.

2. The image reading device according to claim 1.

16. The light emitting means, the wiring pattern and the light guide are provided on a second surface of the substrate not facing the platen glass.

16. The image reading device according to claim 15.

Images