JP4188716B2 - Image reading device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image reading apparatus that irradiates an original with an exposure lamp and receives reflected light by a photoelectric conversion element to read an electric signal for the original image in units of lines and has two or more different line periods. In particular, the present invention relates to an image reading apparatus that can eliminate the variation in the amount of light for each line and solve the problem that a difference occurs in the integrated amount of light for each line, resulting in white horizontal stripes in the read image.
[0002]
[Prior art]
2. Description of the Related Art In general, an image reading apparatus is known in which an original is irradiated with an exposure lamp and reflected light is received by a photoelectric conversion element to read an electric signal for the original image in units of lines and have two or more different line periods. Yes.
As a prior art, Japanese Patent Laid-Open No. 2000-323292 (the phase comparator 13 compares the phase of the oscillation signal of the frequency variable oscillator 11 divided by the frequency divider 12 with that of the external synchronization signal Sync). The oscillation frequency of the variable frequency oscillator 11 is controlled in accordance with the phase difference, whereby the oscillation phase of the variable frequency oscillator 11 is phase-locked by the external synchronization signal Sync, and the oscillation signal of the variable frequency oscillator 11 is sent to the gate signal generation circuit 5. The switching element of the inverter circuit 3 is opened / closed by the output of the gate signal generation circuit 5 to convert the DC voltage output from the DC power source 5 into an AC voltage, and the AC voltage output from the inverter circuit 3 passes through the step-up transformer 2. The lamp 1 is applied to the lamp 1 and the lamp 1 is turned on).
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-323292
[Problems to be solved by the invention]
However, in the general image reading apparatus, since the reading cycle of each line and the light amount control cycle (lamp lighting cycle) are asynchronous, when the lamp lighting cycle is not sufficiently small with respect to one line cycle, The number of lamp lighting pulses included in one line cycle varies for each line, and due to the variation, a difference occurs in the integrated light quantity for each line, resulting in a problem of white stripes in the read image.
Therefore, in Patent Document 1, the oscillator of the inverter of the power feeding device that supplies power to the lamp is a frequency oscillator, and the frequency variable oscillator is controlled so that the oscillation signal from the frequency variable oscillator is phase-locked to the external synchronization signal. Thus, the dielectric barrier discharge fluorescent lamp is caused to emit light in synchronization with the external synchronization signal without causing fluctuations in the amount of light.
However, the above-described method of causing the frequency to be varied and synchronized to emit light has the disadvantage that the lamp lighting frequency is variable, so that it may deviate from the optimum lighting condition (lighting frequency) of the lamp and the circuit configuration is complicated. It was.
Accordingly, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a line synchronization signal that defines the reading start timing of each line in an image reading apparatus having two or more different one-line periods. The lamps are turned on synchronously, and the number of lighting pulses for lighting the lamps in a plurality of line periods with different one line periods is fixed to the set number of pulses in each line period. It is an object of the present invention to provide an image reading apparatus capable of controlling an oscillation circuit to eliminate a light amount fluctuation for each line and to solve a problem that a difference occurs in an integrated light amount for each line and a white horizontal stripe in a read image.
[0004]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the invention according to claim 1 is different in that an electric signal for an original image is read line by line by irradiating an original with a lamp and receiving reflected light by a photoelectric conversion element. An image reading apparatus having at least two line periods, an inverter unit for lighting the lamp in synchronization with a line synchronization signal defining a reading start timing of each line having two or more different line periods, and a predetermined An oscillation clock that outputs an oscillation clock at a predetermined period according to a time constant of a capacitor and a resistor set to a value, and discharges the charge charged in the capacitor by the line synchronization signal; and asynchronous with the line synchronization signal in is input, the finger power supply of the lamp ON / OFF control signal for switching the supply / non-supply of power to the oscillation circuit to said oscillator circuit A manner that period, a lighting control unit for the oscillation circuit is the oscillation clock of a predetermined cycle to be output, is controlled to supply as a lamp lighting signal of each of the inverter unit in the two or more different line cycle, And the time constants of the capacitor and the resistor of the oscillation circuit are set such that the number of pulses of the lamp lighting signal output within the two or more different line periods becomes a fixed number of pulses according to each line period. It is characterized by setting to.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is an overall configuration diagram of an embodiment of a color image reading apparatus according to the present invention.
The function of each part will be described with reference to FIG.
First, the scanner main body will be described. The document placed on the document table glass 8 is irradiated by the first mirror 3 and the lamp 2. Here, the first mirror 3 and the lamp 2 are mounted on the first carriage 31 and perform scanning while moving the lower part of the document table. The reflected light from the original is scanned by the first mirror 3 and the second mirror 5 and the third mirror 4 on the second carriage 32, converged by the lens 1, and applied to the SBU 10 on which the CCD is mounted. Is photoelectrically converted into an electric signal.
The first and second carriages 31 and 32 on which the first mirror 3, the lamp 2 and the second mirror 5, and the third mirror 4 are mounted, respectively, are driven from the carriage home position to the maximum scanning region using the traveling body motor 9 as a drive source. It can move in the direction (left and right in the figure).
Next, the ARDF (automatic duplex document feeder) unit will be described. Documents loaded along the document guide 12 of the document table 11 are called by the calling roller 14 and the sheet feeding belt 16 when single-sided document reading is selected. The conveyance roller 15, separation roller 17, and first conveyance roller 18 are fed to the second conveyance roller 21 and the discharge roller 23 through the reading position between the DF original glass 6 and the reflection guide plate 20, and the original is discharged. Is done. A registration sensor 19 is arranged in front of the DF original glass, and can detect the timing of the paper entering (leading edge) and the trailing edge of the reading part.
On the other hand, when double-sided original reading is selected, first, the front side of the original is read in the same manner as when single-sided original reading is selected.
An explanation will be given regarding the reading of the surface of the document. The calling roller 14, the feeding roller 16, the conveying roller 15, the separation roller 17, and the first conveying roller 18 pass through the reading position between the DF original glass 6 and the reflection guide plate 20, and then the second conveying roller 21 and the paper discharge. The branch claw 24 is switched downward without being discharged into the roller 23 and is transported onto the reversing table 26 by the reversing roller 25. After the trailing edge of the original passes through the paper discharge roller 23, the branch claw 24 is switched upward, and the reversing roller is temporarily stopped.
[0006]
Next, the reading of the back side of the original will be described. In order to read the back side of the original, the reverse roller 25 once stopped is rotated in the opposite direction to the original so that the original is turned to the reverse table 26. From the DF original glass 6 and the reflection guide plate 20 through the first conveyance roller 18 and the reading position between the reflection guide plate 20 and the second conveyance roller 21 and the discharge roller. The paper is fed to the paper roller 23, and then the original is discharged. When the original passes through the reading position between the DF original glass 6 and the reflection guide plate 20 together with the reading of the front and back surfaces, the original is irradiated by the lamp 2 stopped near the reading position, and the reflected light is The first mirror 3 and the second mirror 5 and the third mirror 4 which are integrally formed are scanned. Thereafter, photoelectric conversion is performed as in the case of the document table.
Note that the paper feeding mechanisms of the ARDF calling roller 14, the paper feeding belt 16, the conveying roller 15, and the separation roller 17 are driven by a paper feeding motor (not shown). Further, the transport mechanisms of the first transport roller 18, the second transport roller 21, the paper discharge roller 23, and the reverse roller 25 are driven by a transport motor (not shown).
Further, in the ARDF, a set sensor 13 for detecting whether or not a document is set on the document table 11 in order to detect the document, a width size detection sensor 28 for detecting the document size, and a first document length sensor. 29, a second document length sensor 30, and a document trailing edge sensor 27 for detecting the trailing edge of the document. The scanner body is equipped with an SCU 7 that controls the operation of the color image reading apparatus including the scanner body and ARDF.
[0007]
2 and 3 are control block configuration diagrams of the image reading apparatus shown in FIG.
In FIG. 2 and FIG. 3, the reflected light of the original that has entered the CCD 100 on the SBU 10 is converted into an analog signal having a voltage value corresponding to the light intensity in the CCD 100, and is output separately into odd bits and even bits. The The analog image signal of the SBU 10 is input to the A / D converter 102 after the dark potential portion is removed by the analog processing circuit 101 on the VIOB 33, the odd bits and the even bits are combined, and the gain is adjusted to a predetermined amplitude. Signaled. The digitized image signal is subjected to shading correction by the shading unit 103, subjected to image processing such as gamma correction and MTF correction by the IPU 104 on the SCU 7 from the VIOB 33, and then stored as image data together with a synchronization signal image clock. The data is input to the memory controller 105 for managing the means (SDRAM 106) and stored in the image memory 106 composed of SDRAM.
The image data stored in the image memory 106 is sent to the external I / F driver 107 and transferred to the output device 120 such as a personal computer or a printer. The external I / F driver generically describes drivers such as SCSI, IEEE 1394, LAN, and local video signals.
A CPU 108, ROM 109, RAM 110, and motor controller 112 are mounted on the SCU 7. The CPU 108 is a traveling body motor 9 that is a stepping motor of the scanner body, an ARDF paper feed motor (not shown), and a transport motor (see FIG. Timing control is also performed. The ADU 42 has a function of relaying power supply of electrical components used for the ARDF unit.
The CPU 108 is connected to the lamp 2 via a lamp ballast 114.
An input port connected to the CPU 108 on the SCU 7 is connected to the main body operation panel SOP 43 via the VIOB 33. A start switch (not shown) and a stop switch (not shown) are mounted on the main body operation panel SOP43. When each switch is pressed, the CPU detects that the switch is turned on via the input port.
[0008]
Next, the present embodiment will be described with reference to FIGS. 4 and 5. First, the control of the lamp ballast 114 and the lamp 2 will be described with reference to FIG.
FIG. 4 is a configuration diagram of the lamp ballast 114 and the lamp 2.
First, in the case of synchronous lighting, when a line synchronization signal (TG-INV) defining the reading start timing of each line is input as shown in FIG. 4 , the inverter 131 that lights the lamp 2 in synchronization with the line synchronization signal is input. The connected oscillation circuit 134 oscillates. The lighting control unit 135 operates according to the clock signal output from the oscillation circuit 134 to control the inverter circuit 131.
The output from the inverter circuit 131 is applied to the lamp 2 via the step-up transformer 132. The CNT input to the lighting control unit 135 is an ON / OFF control signal for the lamp 2. That is, in the case of asynchronous lighting, the line synchronization signal (TG-INV) is fixed to the low level, and the lamp ON / OFF control signal is input to CNT.
Next, FIG. 5 shows an example of the configuration of the inverter 131.
As shown in FIG. 5, when the lamp ON / OFF control signal (CNT) is at a low level, the transistor TR1 is turned on, and power is supplied to IC1, which is an inverter control IC. IC1 which is an inverter control IC incorporates a driver and an oscillator for driving the switching element FET1, and the oscillator oscillates at a predetermined cycle according to the constants of the capacitor C1 and the resistor R3 connected to the Ct and Rt terminals. The driver (diode D1 and resistor R4) is driven by the oscillation pulse, and the switching element FET1 is driven by the output of the driver.
When the switching element FET1 is turned on by the drive signal in this way, a current flows through the path of the constant voltage power supply 130 → the primary winding of the step-up transformer 132 → the switching element FET1, and energy is stored in the step-up transformer 132.
Next, when the switching element FET1 is turned off, the current flowing through the step-up transformer 132 is cut off, the stored energy is released, and a voltage waveform having steep rises at the primary and secondary sides of the step-up transformer 132 is generated. To do.
This voltage waveform decays with time, and then when the switching element FET1 is turned on and then turned off, a voltage waveform having a steep rise again is generated as described above. That is, each time the switching element FET1 is turned on / off, a voltage waveform having a steep rise is generated again, a current repeatedly flows through the lamp 2, and the lamp 2 is turned on to emit light.
IC1, which is an inverter control IC, oscillates by a CR oscillation circuit composed of C1, R3, and VR1, but stops oscillation by discharging the capacitor C1 during the High period of the TG-INV signal, and oscillates during the Low period. Can be started and synchronized lighting can be performed.
[0009]
Next, the present embodiment will be described with reference to FIGS. 6, 7, and 8.
FIG. 6 is a timing chart showing the relationship between the lamp ON / OFF control signal (CNT) and the line synchronization signal (TG-INV). FIG. 7 shows the line synchronization signal (TG-INV) and the optical waveform of the lamp 2. FIG. 8 is a timing chart showing the relationship between the line synchronization signal (TG-INV) and the light waveform of the lamp 2.
That is, FIG. 6 shows the timing of the lamp ON / OFF signal (CNT) and the line synchronization signal (TG-INV). TG-INV is supplied for the purpose of synchronizing the lighting frequency separately from CNT. . Note that the CNT signal and the TG-INV signal are supplied asynchronously, and ON and OFF of the CNT signal are arbitrary times.
7 and 8 show the timing of the TG-INV and the inverter output (light waveform). As a condition, the overlap with the TG-INV cycle High period is the period when the FET is ON, and the actual gate voltage measurement value. ONDuty = 20% (7.1 μs / 35.7 μs) is fixed, and the delay time from when TG-INV becomes Low until the FET is turned on is shown as a fixed gate voltage measured value of 23.5 μs. FIG. 7 shows a TG-INV cycle of 339 μs, and FIG. 8 shows a TG-INV cycle of 229 μs.
[0010]
As shown in FIG. 7, when the TG-INV cycle is 339 μs, the frequency range of 8 pulses in one line cycle is obtained based on the above conditions, and the result is as follows.
<8 pulses / line cycle>
* Minimum frequency: 8 ON times are perfect for 312.5μs minus TG-INV period of 339μs, high period of 3.0μs and delay time of 23.5μs.
Assuming that one period is 100%, the repetition period is 820% in 312.5 μs. The time per 100% is 38.1 μs, which is 26.2 kHz.
* Maximum frequency: The time obtained by dividing 312.5 μs by 9 is the maximum frequency, which is 34.7 μs = 28.8 kHz.
<Frequency range> 26.2 kHz to 28.8 kHz → 27.5 ± 1.3 kHz
Next, when the image reading apparatus has two or more different line periods, the line period (TG-INV period) is set to 229 μs as shown in FIG. The following frequency range is obtained as follows.
<5 pulses / line cycle>
* Minimum frequency: 5 ON times are the perfect frequency for 202.5 μs minus TG-INV period 229 μs, high period 3.0 μs and delay time 23.5 μs.
Assuming that one period is 100%, the repetition period is 520% in 202.5 μs. The time per 100% is 38.9 μs, which is 25.7 kHz.
* Maximum frequency: Time obtained by dividing 202.5 μs by 6 is the maximum frequency, and 33.8 μs = 29.6 kHz.
<Frequency range> 25.7 kHz to 29.6 kHz → 27.65 ± 1.95 kHz Here, a frequency range satisfying two different line periods at the same time is obtained as follows.
* Line cycle 1 = 339 μs: 26.2 kHz to 28.8 kHz → 27.5 ± 1.3 kHz
* Line cycle 2 = 229.0 μs: 25.7 kHz to 29.6 kHz → 27.65 ± 1.95 kHz
<Frequency range> 26.2 kHz to 28.8 kHz → 27.5 ± 1.3 kHz
That is, since the frequency range that satisfies two different line periods simultaneously is 27.5 ± 1.3 kHz, it is set as such. Therefore, the oscillation frequency of the inverter is set so that the number of lighting pulses with respect to two or more different one line periods is constant.
[0011]
Here, the oscillation frequency calculated as described above changes if the ambient temperature becomes 0 ° C. and 60 ° C. with respect to the ambient temperature of 25 ° C. due to the temperature coefficient of the parts used. Set.
As an example, the total of the constant change amount of each part with respect to the ambient temperature 25 ° C. (± 0%),
± 3.0% at an ambient temperature of 60 ° C
± 2.0% at ambient temperature 0 ° C
Then, a margin of ± 3.0% is required in the previously calculated frequency range.
<8 pulses / line cycle> TG-INV cycle = 339 μs
Minimum frequency: 26.2 kHz × 103.0% = 27.0 kHz
Maximum frequency: 28.8 kHz × 97.0% = 27.9 kHz
<Frequency range> 27.0 kHz to 27.9 kHz → 27.45 ± 0.45 kHz
<5 pulses / line cycle> TG-INV cycle = 229 μs
Minimum frequency: 25.7 kHz × 103.0% = 26.5 kHz
Maximum frequency: 29.6 kHz × 97.0% = 28.7 kHz
<Frequency range> 26.5 kHz to 28.7 kHz → 27.6 ± 1.1 kHz
Here, a frequency range that satisfies two different line periods simultaneously is as follows.
* Line cycle 1 = 339 μs: 27.0 kHz to 27.9 kHz → 27.45 ± 0.45 kHz
* Line cycle 2 = 229.0 μs: 26.5 kHz to 28.7 kHz → 27.6 ± 1.1 kHz
<Frequency range> 27.0 kHz to 27.9 kHz → 27.45 ± 0.45 kHz
Therefore, the frequency range that simultaneously satisfies two different line periods when considering the temperature coefficient of the parts used is 27.45 ± 0.45 kHz, and is set as such. Therefore, the oscillation frequency of the inverter is set so that the number of lighting pulses with respect to two or more different one line periods is constant taking into account the ambient temperature change.
[0012]
Next, this embodiment will be described with reference to FIG.
In the image reading apparatus, the light emission color of the lamp is white, which means that three types of phosphors (R: red, G: green, B, which are coated on the glass inner surface with ultraviolet rays generated in the glass tube by rare gas discharge). : Blue) and converted to visible light to become white.
FIG. 9 shows light waveforms of the respective emission colors of RGB. Here, the interval between the peaks of the optical waveform is 35.7 μs when the inverter oscillation frequency is 28 kHz. In addition, as shown in the optical waveform of FIG. 9, the afterglow time of the R and G phosphors is long and the brightness can be maintained. Since the light duration is short and the difference in brightness is large, the amount of light difference between the lines is large and the color unevenness is likely to occur during asynchronous lighting.
Therefore, in this embodiment, when there are two or more different line cycles, synchronous lighting is performed when the line cycle is large (when the line speed is slow) as in the color mode or the two-color mode, and the monochrome mode is set. As described above, when the line cycle is small (when the line speed is fast), asynchronous lighting is performed to solve the occurrence of color unevenness. In other words, when the linear velocity is high, the lamp lighting integration time increases and the oscillation frequency fluctuation due to the effect of heat generation increases, causing a shift in synchronization, and to reduce the oscillation frequency fluctuation, the oscillation frequency accuracy is improved. Therefore, asynchronous lighting and synchronous lighting are switched according to the line cycle.
[0013]
【The invention's effect】
As understood from the above description, according to the present invention, the number of pulses the number of pulses of the lamp lighting signal within the line period in which the lamp ballast having an inverter unit outputs (light waveform) corresponding to each line period By controlling so as to be fixed (constant), there is no difference in the integrated light quantity for each line, so that it is possible to eliminate the problem of white reading of the read image.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of an embodiment of a color image reading apparatus according to the present invention.
FIG. 2 is a control block diagram of the image reading apparatus shown in FIG.
3 is a control block diagram of the image reading apparatus shown in FIG. 1. FIG.
4 is a configuration diagram of the lamp ballast 114 and the lamp 2 shown in FIG. 1. FIG.
5 is a diagram showing an example of the configuration of an inverter 131 shown in FIG.
FIG. 6 is a timing chart showing a relationship between a lamp ON / OFF control signal (CNT) and a line synchronization signal (TG-INV).
FIG. 7 is a timing chart showing the relationship between the line synchronization signal (TG-INV) and the optical waveform of the lamp 2;
FIG. 8 is a timing chart showing the relationship between the line synchronization signal (TG-INV) and the optical waveform of the lamp 2;
FIG. 9 is a diagram showing light waveforms of RGB emission colors.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Lens, 2 ... Lamp, 3 ... 1st mirror, 4 ... 3rd mirror, 5 ... 2nd mirror, 6 ... DF original glass, 7 ... SCU, 8 ... Original plate glass, 9 ... Running body motor, 10 ... SBU, 11 ... Document table, 12 ... Document guide, 13 ... Set sensor, 14 ... Roller, 15 ... Conveyance roller, 16 ... Paper feed belt, 17 ... Separation roller, 18 ... First conveyance roller, 19 ... Registration sensor, DESCRIPTION OF SYMBOLS 20 ... Reflection guide plate, 21 ... 2nd conveyance roller, 23 ... Paper discharge roller, 24 ... Branch nail | claw, 25 ... Reverse roller, 26 ... Reverse table, 27 ... Document trailing edge sensor, 28 ... Width size detection sensor, 29 ... First document length sensor, 30 ... second document length sensor, 31 ... first carriage, 32 ... second carriage, 33 ... VIOB, 42 ... ADU, 43 ... SOP, 100 ... CCD, 101 ... analog processing Circuit, 10 ... Converter, 103 ... Shading section, 104 ... IPU, 105 ... Memory controller, 106 ... Image memory, 107 ... External I / F, 108 ... CPU, 109 ... ROM, 110 ... RAM, 112 ... Motor controller, 114 ... Lamp stable 120 ... Output device 130 ... Constant voltage power supply 131 ... Inverter 132 ... Step-up transformer 134 ... Oscillator circuit 135 ... Lighting controller

Claims (1)

An image reading apparatus that irradiates an original with a lamp and receives reflected light by a photoelectric conversion element to read an electric signal for the original image in units of lines, and has two or more different line periods,
An inverter unit that lights the lamp in synchronization with a line synchronization signal that defines a read start timing of each line having two or more different line periods;
An oscillation circuit that outputs an oscillation clock at a predetermined period according to a time constant of a capacitor and a resistor set to a predetermined value, and discharges the electric charge charged in the capacitor by the line synchronization signal ;
The oscillation circuit outputs the signal while the lamp ON / OFF control signal for switching power supply / non-supply to the oscillation circuit is instructed to supply power to the oscillation circuit. A lighting control unit that controls the oscillation clock having a predetermined cycle to be supplied as a lamp lighting signal of the inverter unit within the two or more different line cycles,
The time constant of the capacitor and the resistor of the oscillation circuit is set so that the number of pulses of the lamp lighting signal output within the two or more different line periods becomes a fixed number of pulses according to each line period. An image reading apparatus.

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