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 device that reads an image from a document. [Background technology]

[0002] An image reading device irradiates a document with light and receives the reflected light to read an image. Patent Document 1 discloses an image reading device having an LED array as an illumination mechanism, in which a plurality of light-emitting diodes (LEDs) are linearly arranged on a substrate. Patent Document 2 describes an image reading device having a configuration in which a light guide that guides light emitted from the LED is closely attached to the LED, and the light irradiated from the LED is highly efficiently focused on the surface of the document. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-228040 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-134745 Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, an image reading device includes a platen on which a document is placed and a pressure plate that presses the document on the platen to prevent the document from floating during reading. In such an image reading device, user operations such as placing a document and opening and closing the pressure plate cause friction and peeling between the pressure plate and the document. This can cause the pressure plate to become charged.

[0005] When a charged pressure plate is closed while a scanning unit containing an LED board with an LED mounted and a light guide is located directly below the platen glass, the light guide may become induced charged by the charged pressure plate. If the light guide becomes charged, a discharge may occur between the light guide and the LED terminals. Furthermore, the destination of discharge from the charged light guide is not limited to the LED terminals, but may also be the wiring on the LED board or the terminals of mounted electronic components other than the LED.

[0006] If a discharge occurs at the terminals of an LED or an electronic component, the LED or the semiconductor device that controls the LED's lighting may malfunction. If the LED or semiconductor device malfunctions, the image reading device may not be able to obtain enough light to read the image, and the image on the document may not be read accurately.

[0007] In view of the above-mentioned problems, the present invention has as its main object to suppress a decrease in image reading accuracy caused by the light guide being charged. [Means for solving the problem]

[0008] The image reading device of the present invention includes a platen glass on which a document is placed, a pressure plate attached to the platen glass so as to be able to open and close, a light emitting unit that emits light to be irradiated onto the document, a light guide that guides the light emitted from the light emitting unit to the document, a substrate on which the light emitting unit is mounted, a light receiving unit that receives the light reflected by the document and reads an image of the document, and a light receiving unit of the substrate facing the platen glass. No. 1 and a ground pattern provided on the surface and grounded, the ground pattern discharging the electric charge of the pressure plate. [Effects of the Invention]

[0009] According to the present invention, it is possible to prevent a decrease in image reading accuracy caused by the light guide being charged. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating the configuration of an image reading device. [Figure 2] FIG. [Figure 3] FIG. [Figure 4] FIG. 2 is a detailed explanatory diagram of an LED array board and an LED control board. [Figure 5] (a) and (b) are detailed diagrams of the LED array unit. [Figure 6] A-A' cross-sectional view of the LED array unit. [Figure 7] FIG. 10 is an explanatory diagram of a second example of an LED array unit. [Figure 8] 10(a) and 10(b) are explanatory diagrams of a third example of an LED array unit. [Figure 9] FIG. 10 is an explanatory diagram of a fourth example LED array unit. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present invention will now be described in detail by way of example with reference to the drawings.

[0012] (Image reader) 1 is a diagram illustrating the configuration of an image reading device according to this embodiment. The image reading device 100 includes a reading unit 101, a belt 102, a motor 103, a platen glass 104, and a pressure plate 105. The belt 102 is driven to rotate by the motor 103, and moves the reading unit 101 in the direction of the arrow (scanning direction). An original 106 is placed on the platen glass 104 and pressed down by the pressure plate 105. The pressure plate 105 is attached to the platen glass 104 so as to be able to open and close. The reading unit 101 reads an image from the original 106 placed on the platen glass 104 while being moved in the scanning direction by the belt 102.

[0013] (Reading unit 101) 2 is an explanatory diagram of the configuration of the reading unit 101. The reading unit 101 includes an LED array unit 201 which is a light-emitting unit, a plurality of plane mirrors 202a to 202d, an imaging lens 203, an image sensor 204 which is a light-receiving unit, and an image sensor board 205 on which the image sensor 204 is mounted. The LED array unit 201 includes an LED array board 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 guide that guides light emitted from the LEDs to the original 106.

[0014] The reading unit 101 irradiates light from an LED array unit 201 onto an original 106 placed on an original platen glass 104. The light is reflected by the original 106. The light reflected by the original 106 is guided to an imaging lens 203 by plane mirrors 202a to 202d, and an image is formed on the light receiving surface of an 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 an image sensor board 205, converted into image data representing the image of the original, and output.

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

[0016] The reading unit 101 includes an LED array board 206 and an LED control board 302. The LED array board 206 has an LED array 301 mounted thereon, in which a plurality of LEDs are arranged in series to irradiate the document 106 with light. The LED control board 302 has an LED control unit 303 mounted thereon. 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 of the LED array 301 by supplying power from a power source to each LED of the LED array 301 based on an LED lighting control signal obtained from the CPU 300.

[0017] (LED array board 206 and LED control board 302) 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, and 406 as an LED control unit 303. Power is supplied to the LED control substrate 302 from a power supply 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 configured of a plurality of LEDs 408a to 408l, and a ground pattern 409 (a wiring pattern for grounding). Power is supplied to the LED array substrate 206 from the LED control substrate 302 via a connector 407. The LED array 301 of this embodiment has three rows of a plurality of LEDs connected in series.

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

[0019] The current control units 404, 405, and 406 control the current flowing through the LED array 301. The light irradiated onto the document 106 needs to have a constant light emission intensity. However, because the forward voltage (VF) of each LED 408a to 408l varies, simply controlling the applied voltage can result in variations in the light emission intensity. The current control units 404, 405, and 406 suppress such variations in the light emission intensity by controlling the amount of current supplied to the LED array 301. The number of current control units 404, 405, and 406 corresponds to the number of LED columns (LEDs 408a to 408d, 408e to 408h, and 408i to 408l) in the LED array 301. In this embodiment, since there are three LED columns, three current control units 404, 405, and 406 are provided. The current control units 404, 405, and 406 are constant current circuits configured, for example, with operational amplifiers, current-limiting resistors, and the like.

[0020] The LED array substrate 206 applies power supplied from the LED control substrate 302 via a connector 407 to the first LED in each column of the LED array 301. In this embodiment, power is applied to the anode terminals of the LEDs 408a, 408e, and 408i. The cathode terminals of the rearmost LEDs 408d, 408h, and 408l in each column are connected to corresponding current control units 404, 405, and 406 of the LED control substrate 302 via the connector 407. The column of LEDs 408a to 408d has its light emission amount controlled by adjusting the current amount using the current control unit 404. The column of LEDs 408e to 408h has its light emission amount controlled by adjusting the current amount using the current control unit 405. The column of LEDs 408i to 408l has its light emission amount controlled by adjusting the current amount using the current control unit 406.

[0021] In this embodiment, the LED array 301 is configured with three rows of four LEDs connected in series, each row being connected in parallel. The number of LEDs connected in series and the number of rows of LEDs in the LED array 301 can be freely set depending on the area to be illuminated. The wider the area to be illuminated, the greater the number of LEDs connected in series and the greater the number of rows of LEDs.

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

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

[0024] The LED array unit 201 has electrically grounded ground patterns 409 provided on each of the upper side (first surface) and lower side (second surface) of the LED array substrate 206. The first surface of the LED array substrate 206 faces the platen glass 104. The second surface of the LED array substrate 206 faces the image sensor 204 and does not face the platen glass 104. The ground pattern 409 on the first surface of the LED array substrate 206 is formed in the longitudinal direction of the LED array substrate 206 and is connected to the ground pattern 409 on the second surface of the LED array substrate 206 via a through hole. The ground pattern 409 on the second surface of the LED array substrate 206 is connected to the LED control substrate 302 via a connector 407.

[0025] The LEDs 408a to 408h and wiring patterns 501a and 501b that electrically connect the LEDs 408a to 408h are mounted on the second surface of the LED array substrate 206. The row of LEDs 408a, 408b, 408c, and 408d is connected in series by the wiring pattern 501a, which is a conductive member. The row of LEDs 408e, 408f, 408g, and 408h is connected in series by the wiring pattern 501b, which is a conductive member. Because the wiring pattern 501a and the wiring pattern 501b are connected in parallel, the row of LEDs 408a, 408b, 408c, and 408d and the row of LEDs 408e, 408f, 408g, and 408h are connected in parallel. The wiring patterns 501a and 501b are connected to the LED control substrate 302 via the connector 407.

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

[0027] The light guide 207 is arranged 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 light incident on the incident surface 208 from the LED 408 toward the original 106. The LED 408 has a terminal 602 soldered to a part of the wiring pattern 501. The ground pattern 409 formed on the upper surface side (first surface side) of the LED array substrate 206 is not coated with solder resist that serves as an insulating film.

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

[0029] (Second example of LED array unit 201) 7 is an explanatory diagram of a second example of an LED array unit 201. This explanatory diagram is a cross-sectional view taken along the line A-A' in FIG. 5. Normally, the wiring pattern 501 is provided on the mounting surface of the LEDs 408 (the lower surface (second surface) of the LED array substrate 206). However, depending on the substrate shape and the amount of wiring, there are cases where the wiring pattern 501 must be disposed on the upper side (first surface) of the LED array substrate 206, which is the surface on which the LEDs 408 are not mounted.

[0030] In this case, solder resist 701 is applied as an insulating film on the wiring pattern 501 arranged on the first surface of the LED array substrate 206. Applying the solder resist 701 suppresses discharge from the pressure plate 105 through the wiring pattern 501 arranged on the first surface. This suppresses the effect of charging of the pressure plate 105 on the wiring pattern 501, preventing fluctuations in power to the LED array 301 due to charging of the pressure plate 105. As explained in FIG. 6, solder resist is not applied to the ground pattern 409 arranged on the same surface. With this configuration, a path is secured for electric charges accumulated in the pressure plate 105 to be discharged through the ground pattern 409.

[0031] With the above-described configuration, even in a configuration in which the wiring pattern 501 must be disposed on the platen glass 104 side of the LED array substrate 206, the charge accumulated due to charging of the pressure plate 105 is discharged through the ground pattern 409. As a result, the light guide 207 is prevented from being inductively charged due to the charging of the pressure plate 105. This prevents the light guide 207 from discharging to the terminals 602 of the LEDs 408 or the wiring pattern 501, thereby preventing damage to the LEDs 408 or the components mounted on the LED control substrate 302. As a result, the image reading device 100 can accurately read an image on a document even when the pressure plate 105 is charged. In other words, it is possible to suppress a decrease in image reading accuracy due to the charging of the light guide 207.

[0032] (Third example of LED array unit 201) 8A and 8B are explanatory diagrams of a third example of an LED array unit 201. Fig. 8A is a diagram of the LED array unit 201 as seen from the LED array substrate 206 side (upper side). Fig. 8B is a cross-sectional view taken along line AA' in Fig. 8A.

[0033] In the third example, the ground pattern 409 on the upper side (first surface) of the LED array substrate 206 is provided so as to cover substantially the entire first surface of the LED array substrate 206. When the wiring pattern 501 is disposed on the first surface side of the LED array substrate 206 as in the second example, the ground pattern 409 is provided so as to cover the area excluding the wiring pattern 501. In this configuration, the discharge effect of the ground pattern 409 is enhanced. The larger the proportion of the upper side of the LED array substrate 206 that the ground pattern 409 occupies, the higher the discharge effect.

[0034] (Fourth example of LED array unit 201) FIG. 9 is an explanatory diagram of a fourth example of an LED array unit 201. This explanatory diagram is a cross-sectional view taken along the line A-A' in FIG. 5. The LED array substrate 206 is disposed on the surface of the light guide 207 facing the platen glass 104. The length from one end of the LED array substrate 206 to the light-emitting surface 601 of the LED 408 is designated Xgide, and the length from the other end of the LED array substrate 206 to the light-emitting surface 601 of the LED 408 is designated Xnongide. The LED 408 is disposed closer to the other end than the center of the LED array substrate 206 so that Xgide is longer than Xnongide (Xgide > Xnongide). The LED 408 is disposed on the surface of the light guide 207 closer to one end of the LED array substrate 206. As in FIG. 8, the ground pattern 409 is provided so as to cover substantially the entire first surface of the LED array substrate 206.

[0035] In this configuration, the area where the ground pattern 409 covers the light guide 207 is increased. As a result, the possibility of the light guide 207 being inductively charged is reduced, 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 electric charge on the charged pressure plate 105 using the ground pattern 409. This configuration prevents the light guide 207 from becoming charged, even if the pressure plate 105 becomes charged due to a user's actions or the like, and can prevent discharge to the terminals 602 of the LEDs 408 and the wiring pattern 501. This makes it possible to prevent malfunctions of the LEDs 408 and the components mounted on the LED control board 302 that control the lighting of the LEDs 408. Therefore, the image reading device 100 can accurately read the image on the document even if the light guide 207 becomes charged. In other words, it is possible to prevent a decrease in image reading accuracy due to the light guide becoming charged.

Claims

1. a document 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 the electric charge of 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.

7. The image reading device according to claim 1.

8. the substrate further includes a connector for connecting to another substrate on which a control means for controlling light emission of the light emitting means is mounted, the light emitting means controls light emission by power applied from the other board via the connector; The ground pattern is grounded in common with the other substrate 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 the 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 from a direction parallel to the 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 has a plurality of light emitting elements arranged in series in the longitudinal direction of the substrate, the ground pattern is formed in the 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. The length of the ground pattern is longer than the length of the light guide in the longitudinal direction of the substrate.

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 the 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 that does not face the platen glass.

16. The image reading device according to claim 15.

Images