Image reading device

Abstract

To provide an image reading device that makes accurate image reading possible even when a light guide is charged.SOLUTION: The image reading device includes LEDs 408a to 408h that emit light to be irradiated on a document, a light guide 207 that guides the light emitted from the LEDs 408a to 408h onto the document, an LED array substrate 206 on which the LEDs 408a to 408h are mounted, and a grounding pattern 409 that is provided between the LED array substrate 206 and the light guide 207 and is grounded.SELECTED DRAWING: Figure 5

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 down 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 is characterized by comprising: a light-emitting means for emitting light to be irradiated onto a 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 the light reflected by the document and reading an image of the document; and a grounding pattern provided between the substrate and the light guide and grounded. [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) and (b) are another detailed structural diagram of the 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 housing of the image reading device 100 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 LED control 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 onto an original 106 placed on a platen glass 104 using an LED array unit 201. 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 LED control board 205, converted into image data, 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 for controlling light emission of the reading unit 101 by the CPU 300 will be described.

[0016] As described above, the reading unit 101 includes the LED array board 206 and the LED control board 205. The LED array board 206 is mounted with an LED array 301, in which a plurality of LEDs are arranged in series to irradiate the document 106 with light. The LED control board 205 is mounted with an LED control unit 302. The LED control unit 302 is connected to the LED array 301 and the CPU 300. The LED control unit 302 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 205) 4 is a detailed explanatory diagram of the LED array substrate 206 and the LED control substrate 205. The LED control substrate 205 includes an LED lighting unit 402 and current control units 404, 405, and 406 as the LED control unit 302. Power is supplied to the LED control substrate 205 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 205 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 a power supply to the LED array substrate 206 via a 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 an 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 must have a constant intensity. However, because the forward voltage (VF) of each LED 408a to 408l varies, controlling the applied voltage alone can result in variations in the intensity of light. The current control units 404, 405, and 406 suppress such variations in the intensity of light by controlling the amount of current supplied to the LED array 301. The number of current control units 404, 405, and 406 provided corresponds to the number of LED columns (LEDs 408a to 408d, 408e to 408h, and 408i to 408l) in the LED array 301. For this reason, three current control units 404, 405, and 406 are provided in this embodiment. 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 board 206 applies power supplied from the LED control board 205 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 LEDs 408a, 408e, and 408i. The cathode terminals of LEDs 408d, 408h, and 408l at the rear ends of each column are connected via the connector 407 to the corresponding current control units 404, 405, and 406 on the LED control board 205.

[0021] The amount of light emitted by the column of LEDs 408a to 408d is controlled by adjusting the amount of current flowing through them using a current control unit 404. The amount of light emitted by the column of LEDs 408e to 408h is controlled by adjusting the amount of current flowing through them using a current control unit 405. The amount of light emitted by the column of LEDs 408i to 408l is controlled by adjusting the amount of current flowing through them using a current control unit 406.

[0022] 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.

[0023] The ground pattern 409 is a conductive member that is connected to the ground of the LED control board 205 via the connectors 407 and 403. Therefore, the LED control board 205 and the LED array board 206 share a common ground.

[0024] (LED array unit 201) Figure 5 is a detailed configuration diagram of the LED array unit 201. Figure 5(a) is a bird's-eye view of the LED array unit 201. Figure 5(b) is a cross-sectional view taken along line A-A' in Figure 5(a). In the LED array unit 201, a light guide 207 is disposed on an LED array substrate 206. The LED array substrate 206 is, for example, a printed circuit board.

[0025] On the LED array substrate 206, LEDs 408a to 408h, an electrically grounded ground pattern 409, a wiring pattern 501 that electrically connects the LEDs 408a to 408h, and a connector 407 that is electrically connected to the external LED control substrate 205 are mounted. The rows of LEDs 408a, 408b, 408c, and 408d are connected in series by the wiring pattern 501. The rows of LEDs 408e, 408f, 408g, and 408h are connected in series by the wiring pattern 501. The rows of LEDs 408a, 408b, 408c, and 408d and the rows of LEDs 408e, 408f, 408g, and 408h are connected in parallel.

[0026] The light guide 207 is disposed so as to face the light-emitting surfaces 513 of the side-view type LEDs 408 (LEDs 408e, 408f, 408g, 408h) and the LED array substrate 206, and guides the light emitted from the LEDs 408 toward the original 106. The wiring pattern 501 is a conductive member formed on both sides of the LED array substrate 206. To prevent discharge from the light guide 207, it is preferable that the wiring pattern 501 is not formed in an area that comes into contact with the light guide 207.

[0027] 5(b), the LEDs 408 are mounted on the upper surface side (the surface facing the original 106) of the LED array substrate 206. Terminals 510 for connecting to the wiring of the LED array substrate 206 are provided on the side surfaces of the LEDs 408 in the direction in which the LEDs 408 are arranged. The terminals 510 are soldered to land patterns 511 that are part of the wiring pattern 501 on the surface of the LED array substrate 206.

[0028] The ground pattern 409 is formed on the upper surface of the LED array substrate 206. The ground pattern 409 is formed over the entire contact area with the light guide 207 on the upper surface of the LED array substrate 206 (excluding areas such as the ends where a pattern cannot be formed). A portion of the ground pattern 409 is connected to the electrical ground of the image reading device 100 via the connector 407. The ground pattern 409 is electrically connected to the light guide 207 by not applying solder resist, which makes it possible to prevent charging of the light guide 207. Because the potential of the ground pattern 409 is always at the ground level, charges on the surface of the light guide 207 in contact with the ground pattern 409 escape to the ground and are no longer charged.

[0029] With the above-described configuration, even if the pressure plate 105 or the original document 106 becomes charged due to a user's actions or the like, the amount of charge on the light guide 207 is suppressed because the light guide 207 is in contact with the ground pattern 409 over a wide area. As a result, discharge from the light guide 207 to the terminals 510 of the LEDs 408 on the LED array board 206 or to the wiring pattern 501 can be prevented. This makes it possible to prevent failures of the LEDs 408 and the components mounted on the LED control board 205 that control the lighting of the LEDs 408. As a result, the image reading device 100 can accurately read the image on the original document even if the light guide 207 becomes charged. In other words, it is possible to suppress a decrease in image reading accuracy due to charging of the light guide.

[0030] 6 is another detailed configuration diagram of the LED array unit 201. FIG. 6(a) is a bird's-eye view of the LED array unit 201. FIG. 6(b) is a cross-sectional view taken along line B-B' in FIG. 6(a). In the LED array unit 201, a light guide 207 is disposed on an LED array substrate 206. Explanations of the same components as in FIG. 5 will be omitted.

[0031] The wiring pattern 601 is formed on both sides of the LED array substrate 206. As described above, it is preferable that the wiring pattern 601 is not formed in an area that comes into contact with the light guide 207 in order to prevent discharge from the light guide 207.

[0032] If the shape of the LED array substrate 206 or the amount of wiring requires that the wiring pattern 601 be wired in the area where it contacts the light guide 207, the ground pattern 409 is formed so as to cover the lower part of the light-emitting surface 513 of the LED 408. When a side-view type LED 408 is used, this is equivalent to forming the ground pattern 409 between the land pattern 602 to which the terminal 510 of the LED 408 is soldered and the area where the light guide 207 and the LED array substrate 206 contact. With this configuration, if the light guide 207 becomes charged, it is possible to prevent discharge from the light guide 207 to the terminal 510 of the LED 408.

[0033] An electrically grounded ground pattern 409 is present between the contact portion ((i) in the figure) of the land pattern 602 and the light guide 207. As a result, even if the light guide 207 becomes charged and discharge occurs to the LED array substrate 206, the discharge occurs to the ground pattern 409, not to the terminal 510 of the LED 408. Note that the ground pattern 409 is not coated with solder resist, as in FIG. 5.

[0034] When a discharge occurs from a charged object to another object through the air, the object to which the discharge occurs is determined by the "potential difference between the charged object and the discharge destination" and the "distance between the charged object and the discharge destination." In this embodiment, the ground pattern 409 is located closer to the light guide 207 than the terminal 510 of the LED 408 or the land pattern 602. As a result, the discharge destination from the light guide 207 is the ground pattern 409. The "potential difference between the charged object and the discharge destination" can be considered to be approximately the same for conductors within an electric circuit, including the ground. This is because the charge is on the order of kV, but the potential within the electric circuit is on the order of several tens of volts.

[0035] A portion of the wiring pattern 601 may be formed in an area that contacts the light guide 207. In this case, a solder resist 512, which is an insulating film, is applied to the wiring pattern 601. Application of the solder resist 512 prevents discharge from the light guide 207 to the wiring pattern 601. Because the solder resist has high insulating properties, discharge is less likely to occur in the portion where the solder resist is applied.

[0036] With the above configuration, the image reading device 100 can prevent discharge from the light guide 207 to the terminals 510 of the LEDs 408 or the wiring pattern 601, even if the light guide 207 becomes charged due to the pressure plate 105 or the original document 106 being charged by a user's actions or the like. This makes it possible to prevent malfunctions of the LEDs 408 and the components mounted on the LED control board 205 that control the lighting of the LEDs 408. Therefore, the image reading device 100 can accurately read the image of the original document even if the light guide 207 becomes charged. In other words, it is possible to prevent a decrease in image reading accuracy caused by the light guide becoming charged.

Claims

1. 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 between the substrate and the light guide and grounded, Image reading device.

2. The ground pattern is electrically connected to the light guide.

2. The image reading device according to claim 1.

3. The ground pattern is formed at a contact portion of the substrate with the light guide.

3. The image reading device according to claim 1 or 2.

4. the light emitting means is configured by a plurality of light emitting elements connected by a wiring pattern, When the wiring pattern is wired in an area in contact with the light guide, the ground pattern is formed to cover a lower portion of the light emitting element.

2. The image reading device according to claim 1.

5. The ground pattern is provided between a land pattern to which a terminal of the light emitting element is connected and a portion where the light guide is in contact with the land pattern.

5. The image reading device according to claim 4.

6. The wiring pattern is coated with an insulating film.

6. The image reading device according to claim 4 or 5.

7. 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.

7. The image reading device according to claim 1.

8. a document table glass on which the document is placed; a pressure plate for pressing the document placed on the document table glass, The light emitted from the light emitting means is guided by the light guide and illuminates the document placed on the document table glass. The image reading device according to any one of claims 1 to 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 ground pattern is disposed below the light guide.

2. The image reading device according to claim 1.

10. When viewed from the normal direction of the surface of the substrate on which the light emitting means is mounted, 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 ground pattern is provided on the substrate, and the light guide is provided on the ground pattern.

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 continuously in the longitudinal direction 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, the wiring pattern is provided on the substrate, an insulating film is applied between the wiring pattern of the substrate and the light guide; When viewed from a normal direction of a surface of the substrate on which the light emitting means is mounted, the light guide and the ground pattern overlap, the ground pattern and the insulating film do not overlap, and the light guide and the insulating film do not overlap.

2. The image reading device according to claim 1.

16. The present invention is characterized in that the wiring pattern is provided on the substrate, the insulating film is provided on the wiring pattern, and the light guide is provided on the insulating film.

16. The image reading device according to claim 15.

Images