JP2009200623A - Document reader apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten the document read time resulting from processing for adjusting the volume of light in a document reader apparatus. <P>SOLUTION: When power of a document reader apparatus 10 is turned on, a CPU 31 performs start-up initialization processing and determines the light source intensity at the time of initialization, which is then stored in a memory 32. Upon detecting a read-out request, the CPU 31 determines the light source intensity at the time of scanning not by try and error but based on a formula using the light source intensity at the time of initialization, the exposure time at the time of initialization, and the exposure time at the time of scanning. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an original reading apparatus including a light source device having a point light source as a light source.

  In a document reading device, for example, a scanner, a document is read by receiving reflected light or transmitted light of light emitted from the light source device to the document by an image sensor, for example, a CCD. Therefore, it is required that the amount of light emitted from the light source device to the document is adjusted so as not to exceed the readable range of the image sensor (the output signal value is not saturated). In the conventional light source device, a cold cathode discharge tube whose illuminating light luminance is difficult to take a constant value is used as a light source because of its characteristics. Therefore, whether or not the image sensor is saturated each time a document is read. Such a determination and brightness adjustment of the light source device so as not to be saturated have been performed (for example, see Patent Document 1).

Japanese Patent Laid-Open No. 10-233891

  However, the brightness adjustment process is a time-consuming process, and if the brightness adjustment process is executed every time the document is read, there is a problem that it takes time to read the document.

  The present invention has been made to solve the above-described problems, and has an object to shorten a document reading time caused by a brightness adjustment process in a document reading apparatus.

  In order to solve at least a part of the above problems, the present invention adopts the following various aspects.

  A first aspect provides a document reading device. An original reading apparatus according to a first aspect includes a light source device using a light emitting diode as a light source, an initialization light source luminance determining unit that determines initialization light source luminance of the light source device using an initialization scanning condition, and A scanning light source luminance setting unit that sets the scanning light source luminance of the light source device during document scanning using the determined initialization light source luminance, the initialization scanning condition, and scanning scanning condition.

  According to the document reading apparatus according to the first aspect, the light source luminance at the time of scanning of the light source device using the light emitting diode as the light source when scanning the document using the light source luminance at initialization, the scanning condition at initialization, and the scanning condition at scanning Therefore, the document reading time resulting from the light amount adjustment process can be shortened.

  In the document reading apparatus according to the first aspect, the initialization scanning condition and the scanning scanning condition may be an initialization exposure time and a scanning exposure time, respectively. Since the exposure amount required at the time of scanning is obtained by the product of the exposure time and the luminance of the light source device, in this case, the light source luminance at the time of scanning can be obtained using each exposure time.

  In the document reading apparatus according to the first aspect, the initialization exposure time and scanning exposure time may be determined based on initialization resolution and scanning resolution, respectively. In this case, an exposure amount suitable for the set resolution can be realized.

The document reading apparatus according to the first aspect further includes a light source luminance control unit that controls the luminance of the light source device by controlling a driving duty ratio of the light emitting diode.
The initialization light source luminance determining unit determines the initialization light source luminance by determining an initialization driving duty ratio, and the scanning light source luminance setting unit includes the initialization exposure time and the scanning time. The light source luminance at the time of scanning may be set by setting the driving duty ratio at the time of scanning using the ratio with the exposure time and the driving duty ratio at the time of initialization. In this case, the light source luminance during scanning can be easily obtained.

  In the document reading apparatus according to the first aspect, the light source luminance setting unit at the time of scanning is a calculation obtained by multiplying the ratio of the exposure time at the time of initialization and the exposure time at the time of scanning by the driving duty ratio at the time of initialization. If the value is less than the set upper limit value of the duty ratio in the light source luminance control unit, the calculated value is set to the scanning drive duty ratio, and the ratio between the initialization exposure time and the scanning exposure time is set to When the calculated value obtained by multiplying the initialization drive duty ratio is equal to or greater than the set upper limit value, the set upper limit value may be set to the scanning drive duty ratio. In this case, when the calculated value is less than the set upper limit value, it is possible to realize the light source luminance at the time of scanning suitable for the exposure time at the time of scanning, and when the calculated value is equal to or higher than the set upper limit value, the upper limit drive duty ratio is achieved. Corresponding scanning light source luminance can be realized.

  The document reading apparatus according to the first aspect further has a calculated value obtained by multiplying the initialization drive duty ratio by a ratio of the initialization exposure time and the scanning exposure time to the set upper limit value or more. In this case, an amplifying unit for amplifying the drive current of the light emitting diode input to the light source device so as to obtain a luminance value corresponding to the calculated value may be provided. In this case, even when the calculated value is equal to or greater than the set upper limit value, it is possible to realize a scanning light source luminance corresponding to a calculated value suitable for the scanning exposure time.

  The second aspect provides a method for setting light source luminance during scanning in an original reading apparatus including a light emitting diode as a light source. In the scanning light source luminance setting method according to the second aspect, the initialization light source luminance of the light source device is determined using the initialization scanning condition, and the determined initialization light source luminance and the initialization scanning condition are determined. Setting a light source luminance during scanning of the light source device during document scanning using a scanning condition during scanning.

  According to the scanning light source luminance setting method according to the second aspect, it is possible to obtain the same operation and effect as the original reading apparatus according to the first aspect, and in the same manner as the original reading apparatus according to the first aspect. It can be realized in various ways. Furthermore, the second aspect can also be realized as a computer program recorded on a computer-readable medium such as a computer program, CD, DVD, or HDD.

  Hereinafter, an original reading apparatus according to the present invention will be described based on examples with reference to the drawings.

FIG. 1 is an explanatory diagram schematically showing a schematic configuration of a document reading apparatus according to the present embodiment. FIG. 2 is an explanatory view of the frame included in the document reading apparatus according to the present embodiment as viewed from the irradiation surface of the light source device for reflection. The document reading apparatus 10 according to this embodiment includes a reflection light source device 12, a document placement glass 111, a document cover 112, a scanning unit 13, a movable mirror unit 14, an optical lens unit 15, an imaging unit 16, and a transmission light source device 20. The control device 30 is provided.

  The transmissive light source device 20 is a light source device used for a transmissive original such as a negative film or a positive film. The transmissive light source device 20 is provided with a visible light source and an infrared light source, and both light sources emit light from the same opening to the transmissive original. A detailed configuration of the transmissive light source device 20 will be described later. The transmissive light source device 20 is disposed in the document cover 112, and the reflective light source device 12 is disposed in the scanning unit 13. The light source device 20 for transmission can be moved in the arrow direction (sub-scanning direction) within the document cover 112 in conjunction with the scanning unit 13 by a driving mechanism (not shown).

  In this embodiment, as shown in FIG. 3, a light emitting diode LD that is a point light source and does not change in light amount with time is used as the light source in each of the light source devices 12 and 20. FIG. 3 is an explanatory diagram conceptually showing an example of an arrangement of light emitting diodes as light emitting sources in the light source device of the present embodiment. That is, the light source devices 12 and 20 can provide a light amount that does not vary during each lighting, and can provide a light amount that does not vary during the period from the start of lighting to the turn-off during each lighting. The luminance of the light emitting diode LD is adjusted by adjusting the drive duty ratio (pulse current waveform width). The light emitting diode LD may be either a side light emitting type or a top surface light emitting type.

  The scanning unit 13 includes a reflecting mirror 131 in addition to the reflecting light source device 12. The scanning unit 13 is moved in the direction of the arrow by a drive mechanism (not shown), scans the document 40 placed on the document placement glass 121, and executes the reading process of the document 40.

  As shown in FIG. 2, a white reference plate 114 used for a white reference determination process, which will be described later, is provided on the surface of the frame 11 that points to the document placement glass 121 facing the scanning unit 13. More specifically, a white reference plate 114 is bonded to the frame 11 near the home position of the scanning unit 13. The white reference plate 114 is provided with two reference points 114a used in position correction processing described later.

  The movable mirror unit 14 includes reflecting mirrors 141 and 142. The movable mirror unit 14 is also moved in the direction of the arrow when reading a document by a driving mechanism (not shown) in conjunction with the scanning unit 13. As the drive mechanism, for example, a known drive mechanism using a timing belt can be used.

  The optical lens unit 15 includes one or more lenses, and condenses the light input from the movable mirror unit 14 on the imaging unit 16. The optical lens unit 15 in the present embodiment has a focusing performance that reduces the deviation between the focal position of infrared light and the focal position of visible light on the imaging unit 16. That is, when visible light and infrared light having a wavelength longer than that of visible light are used, the lens has a lens performance that suppresses a shift of the focal position on the imaging unit 16 due to a difference in wavelength.

  The imaging unit 16 is a semiconductor element that outputs a voltage value corresponding to the amount of received light, and generally includes a light receiving element that converts incident light into electric charges and an element that transfers charges generated in the light receiving elements. As the imaging unit 16, for example, a CCD sensor using a charge coupled device (CCD) for a transfer circuit, or a CMOS sensor using a complementary metal oxide semiconductor (CMOS) can be used. In this embodiment, as shown in FIG. 4, the imaging unit 16 has a plurality of light receiving elements PIX arranged in the main scanning direction and the sub-scanning direction. For each light receiving element PIX, for example, main scanning is performed. R, G, and B color filters for each direction line are attached. FIG. 4 is an explanatory diagram conceptually showing an example of the light receiving element array of the imaging unit in the present embodiment. In addition, among the light receiving elements arranged in the main scanning direction, some of the light receiving elements OBP at both ends always function as optical black pixels (optical black) on which reflected light or transmitted light from the original does not enter, A signal corresponding to optical black is always output. The optical black pixel OBP is used to determine an optical black reference in a black reference determination process described later.

  The control device 30 controls on / off of the visible light source and infrared light source in the transmission light source device 20, on / off of the reflection light source device 12, and operations of the scanning unit 13 and the movable mirror unit 14. The control device 30 acquires the image data of the document 40 read through the imaging unit 16.

  As illustrated in FIG. 5, the control device 30 includes a central processing unit (CPU) 31, a memory 32, and an input / output interface 33 that are connected to each other via a bidirectional bus 34. FIG. 5 is an explanatory diagram illustrating a functional configuration of a control unit included in the document reading apparatus according to the present embodiment. The input / output interface 33 is connected to the transmissive light source device 20, the reflective light source device 12, the scanning unit 13, the movable mirror unit 14, and the imaging unit 16. The control device 30 further includes an analog front end circuit 35 and an analog front end circuit 35 for adjusting gains and offsets of analog signals of R, G, and B colors output from the imaging unit 16 as a result of reading a document. AD converter circuit 36 for converting an analog signal whose gain and offset are adjusted to a digital signal, and light source luminance for controlling the luminance ratio of each light source device by controlling the duty ratio (driving duty ratio) of the driving current for each light source device The control unit 37 and an amplification circuit 38 for amplifying the drive current for the light source devices 12 and 20 are provided.

  The CPU 31 executes various programs and modules stored in the memory 32. The memory 32 includes, for example, a mass storage device such as a volatile or nonvolatile storage element or a hard disk drive. Image data read and generated by the imaging unit 16 is recorded in the memory 32. The memory 32 is based on a startup initialization processing execution module M1 for executing startup initialization processing, a scanning initialization processing execution module M2 for executing scanning initialization processing, and a scanning condition (resolution). A scanning resolution-exposure time table T1 that defines the exposure time and a set luminance (drive duty ratio) storage table T2 of the set light emitting diode LD are stored. When the CPU 31 executes the startup initialization process execution module M1, an initialization light source luminance determination unit is realized, and when the scanning initialization process execution module M2 is executed, a scanning luminance setting unit is realized. . In the resolution-exposure time table T1, an exposure time corresponding to the resolution in the initialization process (position correction process) and an exposure time corresponding to a scanning condition (resolution) that can be set during actual scanning are stored in association with each other. In the startup initialization process and the scanning process described below, the CPU 31 determines the exposure time with reference to the scanning resolution-exposure time table T1. The set brightness storage table T2 stores the set brightness (drive duty ratio) of the light emitting diode LD determined in the startup initialization process. The brightness value set at the time of factory shipment is stored as an initial value, and thereafter, the brightness value can be updated with another value each time the startup initialization process is executed.

  The CPU 31 executes the startup initialization process by executing the startup initialization process execution module M1. Specifically, white reference determination processing (ALOC), black reference determination processing (ABOC), and position (magnification) correction processing (ODT) are executed. In the white reference determination process, for example, the maximum value of RGB signals output from the imaging unit 16 based on the reflected light from the white reference plate 114, which is provided in advance in the document reading device 10, is equal to or less than a predetermined signal value. Therefore, the gain amount in the analog front end circuit 35 is adjusted. Here, when the signal level is expressed by 8 bits (0 to 255), for example, the predetermined signal value is 230 ± 10, and the analog front-end circuit 35 outputs analog signals of RGB colors. It is repeatedly executed until the signal value falls within a predetermined signal value range. The analog signal used for the white reference determination process is, for example, a signal obtained by averaging the read signals obtained by moving the scanning unit 13 by four lines in the sub-scanning direction.

  In the black reference determination process, the offset amount in the analog front-end circuit 35 is adjusted so that the RGB signal values output from the imaging unit 16 based on the input signal from the optical black pixel OBP are within a predetermined signal value range. Is done. Here, when the signal level is represented by 8 bits (0 to 255), for example, the predetermined signal value range is 4 to 6, and an analog signal of each color of RGB is output from the analog front end circuit 35. The signal value is repeatedly executed so as to fall within a predetermined signal value range. The analog signal used for the black reference determination process is, for example, a signal obtained by averaging the read signals obtained by moving the scanning unit 13 by four lines in the sub-scanning direction.

  In the position correction process, for example, an image obtained by reading a reference point 114a provided in advance on the white reference plate 114 of the frame 11 of the document reading apparatus 10 is used. Specifically, the enlargement ratio or reduction ratio of the image is determined so that the distance between the two prepared reference points 114a is the same as a predetermined distance. Furthermore, the moving distance (number of motor driving steps) of the scanning unit 13 from the scanning start position (origin position) to the reference point 114a is calculated, and the scanning unit 13 uses the calculated motor driving step number to scan the original placement glass. The number of motor drive steps to be moved to the end of 121 is corrected.

  In the position correction process, it is further determined whether or not the exposure amount when reading the reference point 114a has reached the saturation exposure amount of the imaging unit 16. Here, at the time of reading the reference point 114a, the reflection light source device 12 irradiates light with a predetermined luminance over a predetermined position correction exposure time AT (X). The exposure amount is generally obtained as a product of the exposure time AT (X) during position correction and the luminance of the light source device 12 for reflection. As described above, the luminance of the reflection light source device 12 can be changed by changing the drive duty ratio of the light emitting diode. Therefore, first, it is determined whether or not the imaging unit 16 is saturated based on the brightness using the drive duty ratio stored in the memory 32 (currently set). The light emitting diode is driven using the duty ratio.

  On the other hand, when the imaging unit 16 is saturated at the brightness using the currently set drive duty ratio, the drive duty ratio is changed stepwise (for example, from 100%), and the imaging unit 16 A drive duty ratio that does not saturate is obtained. The obtained drive duty ratio is stored in the memory 32 and is used as the drive duty ratio of the light emitting diode at the time of subsequent document reading. In determining the exposure amount, for example, it is only necessary to execute determination processing and adjustment of the duty ratio for only the CCD sensor of the color component having the longest exposure time among the RGB colors.

  The document reading process in this embodiment will be described with reference to FIG. FIG. 6 is a flowchart showing a processing routine of document reading processing executed by the document reading apparatus according to this embodiment.

  When the power of the document reading apparatus 10 is turned on, the CPU 31 starts this processing routine. The CPU 31 executes a startup initialization process (step S100). Specifically, the CPU 31 executes white reference determination processing (ALOC), black reference determination processing (ABOC), and position correction processing (ODT). In the white reference determination process, the CPU 31 reads out the signal values output by all the effective pixels in the imaging unit 16, obtains the maximum value of the signal values of each RGB color, and the obtained maximum value is a predetermined signal level (maximum signal level). The gain adjustment amount in the analog front-end circuit 35 is adjusted so as not to exceed. As a result, the white reference (white) is determined.

  In the black reference determination process, the CPU 31 reads out the signal value output by the optical black pixel in the imaging unit 16 and sets the offset adjustment amount in the analog front end circuit 35 so that the signal values of RGB colors fall within a predetermined signal level range. adjust. As a result, the black reference (black) is determined.

  In the position correction process, the CPU 31 corrects the enlargement / reduction ratio and the home position (scanning start position) of the scanning unit 13 with respect to the end of the document placement glass 111 using the reference point 114a. Here, the end portion of the document placement glass 111 is the end side of the document placement glass 111 on the side close to the home position of the scanning unit 13 in the sub-scanning direction. In the position correction process, the CPU 31 further determines the driving duty ratio of the light emitting diode in the light source device 12 for reflection. The determined drive duty ratio is stored in the memory 32.

  The details of the white reference determination process, the black reference determination process, and the position correction process are as described above, and are processes known by those skilled in the art, so a brief description will be given here. The drive duty ratio determination process in the position correction process is a process executed by trial and error, and is a process that generally requires time, but is an important process for preventing the imaging unit 16 from being saturated.

  The CPU 31 stands by until a document reading request is detected (step S110: No). Specifically, the CPU 31 waits without executing the next process until a document reading button operation by the user is detected (until a document reading request is input). When the CPU 31 detects a document reading request (step S110: Yes), it executes a scanning initialization process (initialization process before reading) (step S120).

  In the scanning initialization process, the CPU 31 executes a white reference determination process, a black reference determination process, and a shading process. The shading process is a process well known to those skilled in the art, and a reading error between pixels included in the imaging unit 16 is corrected. For example, the white reference plate 114 is used to correct the white error between the pixels.

  In the initialization process at the time of scanning in the present embodiment, the luminance adjustment (drive duty ratio) process of the light emitting diode, which has been executed in the startup initialization process in order to avoid saturation of the imaging unit 16, is not executed. On the other hand, the exposure amount is generally determined by the scanning condition, that is, the multiplication of the exposure time and the luminance of the light source. Therefore, when the scanning condition at the time of scanning is different from the scanning condition at the time of position correction processing, it is required to realize an optimum exposure amount for preventing the imaging unit 16 from being saturated by adjusting the luminance of the light emitting diode. It is done. The exposure time becomes longer as the scanning condition, for example, the reading resolution becomes higher. In this embodiment, a plurality of exposure times corresponding to a plurality of settable reading resolutions are stored in advance in the memory 32 as a scanning resolution-exposure time table T1.

  Therefore, in this embodiment, the drive duty ratio at startup initialization (light source brightness at startup initialization) stored in the memory 32 during the startup initialization process, the scanning condition set by the user, and the startup initialization process The driving duty ratio during scanning (light source luminance during scanning) is obtained by calculation using the scanning conditions at the time (during the position correction process). Specifically, the drive duty ratio (luminance) at the time of scanning of the light emitting diode at the time of scanning is determined using the proportional expression shown below. In the following equation, B (Y) is the calculated light source luminance (drive duty ratio) (%), B (X) is the light source luminance at startup initialization (%), and AT (X) is the exposure time at startup initialization. (Sec), AT (Y) is the exposure time during scanning (sec), CVout (Y) is an output value corresponding to the target white reference, and CVout (X) is an output value corresponding to the white reference at the time of initialization. In the following, the term “light source luminance” is also used for B (X) and B (Y), but in this case, it means a drive duty ratio (%), and an actual luminance value (for example, 0 in 8 bits). ~ 255) is not meant.

In general, since CVout (Y) has the same output value corresponding to the target white reference as the output value corresponding to the white reference used in the startup initialization process, the above expression is used in the startup initialization process. It can be said that this is an equation for obtaining the luminance of the light emitting diode during scanning by the ratio of the exposure time during the above and the exposure time during the scanning. Note that the ratio between the exposure time during the startup initialization process and the exposure time during scanning can be a value between 0 and 1, but is generally greater than 0 and 1 or less.

  When the CPU 31 finishes the initialization process at the time of scanning and determines the driving duty ratio of the light emitting diode, the CPU 31 drives the light emitting diode with the determined driving duty ratio via the light source luminance control unit 37 to execute the document reading process. (Step 130). The CPU 31 sets the calculated calculated light source luminance B (Y) value as the scanning light source luminance when the calculated calculated light source luminance B (Y) is less than or equal to the set upper limit value, or 100 or less in this embodiment. To do. For example, when the exposure time during scanning that is set with respect to the exposure time during startup initialization processing is long, that is, when a high-resolution scanning condition is set, the drive duty ratio of the light emitting diode LD is lowered. As a result, the brightness of the irradiation light emitted from the light source device 12 for reflection is reduced.

  On the other hand, when the calculated value of the calculated light source luminance B (Y) is larger than 100 (set upper limit value), 100 is set as the scanning light source luminance. This is because the light emitting diode LD is driven at a duty ratio between 0 (setting lower limit value) and 100% (setting upper limit value) and cannot be driven at a duty ratio exceeding 100%. However, when the luminance value of the irradiation light emitted from the reflection light source device 12 is less than the luminance value corresponding to the calculated light source luminance B (Y), an exposure amount that matches the set scanning condition is ensured. Cannot be obtained, and appropriate reading results cannot be obtained. Therefore, in this embodiment, the drive current for the light emitting diode LD is amplified to a predetermined value by the amplifier circuit 38, and the luminance value of the irradiation light emitted from the reflection light source device 12 corresponds to the calculated light source luminance B (Y). It is adjusted to be equal to the value. The relationship between the amplification amount for realizing the corresponding luminance value and the calculated light source luminance B (Y) exceeding 100% is stored in the memory 32 in advance.

  In the document reading process, analog signals of RGB colors are output from the imaging unit 16 in accordance with the reflected light from the document and input to the analog front end circuit 35. In the analog front end circuit 35, gain and offset adjustment processing using the set gain adjustment value and offset adjustment value is executed for the input RGB analog signals, and the adjusted RGB analog signals Is converted into a digital signal by the AD conversion circuit 36, and after predetermined image quality adjustment processing is executed, it is output as read image data to an external device such as a personal computer.

  CPU31 repeatedly performs the process of step S110-S130 until the request | requirement of power-off generate | occur | produces (step S140: No). When the power-off request is generated (step S140: Yes), the CPU 31 ends the processing routine. The power-off request is input to the CPU 31 when the user operates the power button, for example.

  As described above, according to the document reading apparatus 10 according to the present embodiment, a light emitting diode that does not change in luminance with time is provided as a light source, and in the initialization process during scanning, the luminance during scanning is determined using the starting luminance. Since the setting is performed, it is possible to reduce the time required to execute reading without saturating the imaging unit 16. In other words, since the drive duty ratio of the light emitting diode, which is generally determined by a trial and error that generally requires time, is calculated, the time required for determining the luminance can be shortened. In addition, since the luminance of the light source device using the light emitting diode as the light emitting source does not change during the period from the start to the completion of scanning, the imaging unit 16 does not change even if the luminance (drive duty ratio) of the light emitting diode during scanning is determined by calculation. There is no saturation.

  Specifically, for the brightness B (X) determined in the startup initialization process, the exposure time AT (X) as the scanning condition in the startup initialization process and the exposure time AT as the scanning condition in the scan By multiplying the ratio (Y), the luminance B (Y) at the time of scanning is obtained, so that the luminance suitable for the scanning condition at the time of scanning can be obtained.

Other examples:
(1) In the above embodiment, the brightness adjustment at the time of scanning is not performed after the startup initialization process. For example, when the scanning process is not executed for a predetermined time after the power is turned on, it is periodically started. Luminance adjustment by trial and error in the initialization process may be executed. In this case, it is possible to prevent or suppress the saturation of the imaging unit 16 with higher accuracy without causing the user to wait for the scanning process along with the luminance adjustment during scanning.

(2) In the above embodiment, the brightness at the time of start-up initialization at the time of start-up initialization processing is used, but the brightness at the time of initialization processing executed at an arbitrary timing different from the time of scanning is used without being limited to the time of start-up. May be.

(3) In the above embodiment, the optical black pixel OBP is used in the black reference determination process. However, the black reference determination process may be executed in a state where the light source device for reflection 12 is turned off. Also in shading, variations between pixels with respect to the black reference may be corrected in a state where the light source device for reflection 12 is turned off.

(4) In the above embodiment, when the value of the calculated light source luminance B (X) exceeds 100, the drive current input to the light emitting diode LD is amplified by the amplifier circuit 37, and the scanning light source luminance and the calculated light source Luminance B (X) does not match. However, the necessary exposure amount may be ensured by adjusting the exposure time without amplifying the drive current by the amplifier circuit 37. In this case, regardless of the value of the calculated light source luminance B (X), the scanning light source luminance matches the calculated light source luminance B (X).

(5) In the above-described embodiment, the reduction optical system document reading apparatus has been described as an example, but the same effect can also be obtained in a contact optical system document reading apparatus.

(6) In the above embodiment, the white light emitting diode LD is used as the light source, but, for example, red, green, and blue light emitting diodes may be used as the light source.

(7) In the document reading apparatus 10 according to this embodiment, the document 40 is read by moving the scanning unit 13, but the document 40 may be moved on a fixed scanning unit. That is, the document and the scanning unit (reading unit) may be moved relative to each other. The original means a document, an image, and other objects to be read.

(8) In the above embodiment, the document reading device 10 has been described as an example. However, in addition to this, the document reading device 10 may be used for various devices such as a facsimile, a copying machine, and a multifunction device that require adjustment of exposure before scanning. it can.

(9) In the above embodiment, 100% is used as the setting upper limit value, but it goes without saying that various values such as 90% or 110% may be used. That is, when the value is equal to or higher than the set upper limit value, the drive current may be amplified to a predetermined value by the amplifying unit 38 so as to be equal to the luminance value corresponding to the calculated light source luminance B (Y).

  As mentioned above, although this invention was demonstrated based on the Example and the modification, Embodiment mentioned above is for making an understanding of this invention easy, and does not limit this invention. The present invention can be changed and improved without departing from the spirit and scope of the claims, and equivalents thereof are included in the present invention.

It is explanatory drawing which shows typically schematic structure of the original document reading apparatus concerning a present Example. It is explanatory drawing which looked at the frame with which the manuscript reading device concerning this example is provided from the irradiation surface of the light source device for reflection. It is explanatory drawing which shows notionally an example of light emitting diode arrangement | positioning as a light emission source in the light source device of a present Example. It is explanatory drawing which shows notionally an example of the light receiving element arrangement | sequence of the imaging unit in an Example. It is explanatory drawing which shows the function structure of the control part with which the original document reading apparatus based on a present Example is provided. 6 is a flowchart illustrating a processing routine of document reading processing executed by the document reading apparatus according to the present embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Document reading device 11 ... Frame 12 ... Reflection light source device 13 ... Scanning unit 14 ... Movable mirror unit 15 ... Optical lens unit 16 ... Imaging unit 20 ... Transmission light source device 30 ... Control device 31 ... CPU
32 ... Memory 33 ... Input / output interface 34 ... Bidirectional bus 35 ... Analog front end circuit 36 ... AD converter circuit 37 ... Circuit 40 ... Original 111 ... Original placement glass 112 ... Original cover 114 ... White reference plate 114a ... Reference point 121 Document placing glass 131 Reflecting mirror 141 Reflecting mirror LD Light emitting diode M1 Startup initialization processing execution module M2 Scanning initialization processing execution module OBP Optical black pixel PIX Light receiving element T1 Exposure time table T2 ... Setting luminance storage table

Claims (7)

An original reading device,
A light source device using a light emitting diode as a light source;
A light source luminance determining unit at initialization for determining light source luminance at initialization of the light source device using a scanning condition at initialization;
A scanning light source luminance setting unit that sets the scanning light source luminance of the light source device during document scanning using the determined initialization light source luminance, the initialization scanning condition, and the scanning scanning condition;
Document reading device. The document reading device according to claim 1,
The document reading apparatus, wherein the initialization scanning condition and the scanning scanning condition are an initialization exposure time and a scanning exposure time, respectively. The document reading device according to claim 2,
The document reading apparatus, wherein the initialization exposure time and scanning exposure time are determined based on initialization resolution and scanning resolution, respectively. The document reading device according to claim 2 further includes:
A light source luminance control unit for controlling the luminance of the light source device by controlling a driving duty ratio of the light emitting diode;
The initialization light source luminance determining unit determines the initialization light source luminance by determining an initialization driving duty ratio,
The scanning light source luminance setting unit sets a driving duty ratio during scanning by setting a driving duty ratio during scanning using a ratio between the exposure time during initialization and the exposure time during scanning and the driving duty ratio during initialization. A document reader that sets the brightness of the light source. The document reading device according to claim 4,
The scanning light source luminance setting unit is
When the calculated value obtained by multiplying the initialization drive duty ratio by the ratio of the initialization exposure time and the scanning exposure time is less than the set upper limit value of the duty ratio in the light source luminance control unit, Set the calculated value to the scanning drive duty ratio,
If the calculated value obtained by multiplying the ratio of the exposure time during initialization and the exposure time during scanning by the drive duty ratio during initialization is greater than or equal to the set upper limit value, the set upper limit value is set to the scanning upper limit value. Set to the driving duty ratio
Document reading device. The document reading device according to claim 5 further includes:
A brightness value corresponding to the calculated value when a calculated value obtained by multiplying the ratio of the exposure time at initialization and the exposure time at scanning by the driving duty ratio at initialization is equal to or greater than the set upper limit value. An original reading device comprising an amplifying unit for amplifying the driving current of the light emitting diode input to the light source device. A light source luminance setting method at the time of scanning in an original reading apparatus provided with a light emitting diode as a light source,
Determine the light source brightness at the time of initialization of the light source device using a scanning condition at the time of initialization,
Using the determined initialization light source luminance, the initialization scanning condition, and the scanning scanning condition to set the scanning light source luminance of the light source device during document scanning;
Light source brightness setting method during scanning.

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