JP3552536B2 - Image reading device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image reading apparatus used in, for example, a copying machine or a facsimile, and more specifically, to read a large number of documents continuously using a light source such as a fluorescent lamp whose light amount changes depending on an ambient temperature or the like. Related to a simple image reading device.
[0002]
[Prior art]
Conventionally, as this type of image reading apparatus, there is an image reading apparatus that adjusts the light amount of a light source every time one page of a document is read to absorb a fluctuation in the light amount of the light source (Japanese Patent Publication No. 5-30102).
[0003]
[Problems to be solved by the invention]
However, if the light amount of the light source is adjusted every time the image is read as in the above-described conventional example, the light amount is frequently adjusted, so that the warm-up time and the reading time for the first copy are delayed, and the productivity is reduced. Is reduced.
[0004]
In addition, frequent adjustment of the light amount may increase the fluctuation of the light amount. For example, during continuous reading, the light amount decreases significantly, and the correction value is adjusted, so that the adjustment value of the light amount, that is, the dimming value, greatly increases. After the continuous reading is completed, the light source is turned on after the ambient temperature decreases. Sometimes the light intensity of the light source is saturated.
[0005]
SUMMARY OF THE INVENTION It is an object of the present invention to provide an image reading apparatus which can compensate for fluctuations in light amount due to aging of a light source without requiring frequent light amount adjustment, and can achieve both productivity and image quality.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, an image reading apparatus according to the first aspect of the present invention includes a light source for irradiating an original, reading means for photoelectrically reading an image of the original, a reference density plate, and the reference density by the reading means. Light amount correction means for correcting the light amount of the light source based on the reference read data obtained by reading the plate, and light amount correction time determining means for determining a light amount correction time by the light amount correction means based on the lighting time of the light source. It is characterized by having.
[0007]
According to the first aspect of the present invention, the light quantity correction timing determination means determines a light quantity correction timing by the light quantity correction means based on the lighting time of the light source. Therefore, it is possible to determine a light amount correction timing according to the degree of deterioration of the light source with time. Therefore, it is possible to balance the productivity and the image quality by compensating for the decrease in brightness due to the deterioration of the light source over time while suppressing the frequency of light amount adjustment.
[0008]
The invention according to claim 2 is based on a light source for irradiating the original, reading means for photoelectrically reading the image of the original, a reference density plate, and reference reading data obtained by reading the reference density plate by the reading means. And a light quantity correction means for correcting the light quantity of the light source, and a light quantity correction timing determining means for determining the light quantity correction timing by the light quantity correction means based on the number of times of reading the original.
[0009]
According to the second aspect of the present invention, the light quantity correction timing determination means determines the light quantity correction timing by the light quantity correction means based on the number of times of reading the document. Therefore, it is possible to determine a light amount correction timing according to the degree of deterioration of the light source with time. Therefore, it is possible to balance the productivity and the image quality by compensating for the decrease in brightness due to the deterioration of the light source over time while suppressing the frequency of light amount adjustment. According to the second aspect of the present invention, the number of times the original is read can be counted by the existing counter, so that the light amount can be compensated at low cost.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.
[0011]
FIG. 1 shows the overall configuration of a digital copying machine including an image reading section IR as an embodiment of the image reading apparatus of the present invention. The digital copying machine reads an original image and converts it into image data, an image reading unit IR, a memory unit 8 for storing image data output from the image reading unit IR, and an output from the memory unit 8. The printer unit 2 is configured to print and output image data.
[0012]
The image reading section IR has an exposure lamp 3 for irradiating the original with light, imaging optical systems 5a, 5b, and 5c for guiding reflected light from the original, and an image sensor 6 for converting input light into electric signals. And an image processing unit 7 including an analog processing unit for performing a quantization process on an output signal of the image sensor 6 and a digital image processing unit for performing various image processing and image processing on the quantized image signal. The image sensor 6 is mainly composed of a CCD (charge coupled device). The image reading section IR includes a storage section for storing one-line image data for performing various adjustments and image processing, and a CPU (Central Processing Unit) for monitoring the data. Although not described in detail here, this CPU also performs slider control, various kinds of communication, setting and processing of various kinds of image processing, and the like. The image reading device IR will be described later in detail with reference to FIG.
[0013]
Further, the digital copying machine is provided with an automatic document feeder FDH, and the automatic document feeder FDH can read a document by the image reading unit IR while feeding a document to a specific position on the document table 10 (a so-called image reading unit IR). Sink).
[0014]
The memory unit 8 will be briefly described below. The memory unit 8 includes an image memory (not shown), a compression unit, a code memory (a large-capacity storage unit such as a hard disk drive (HDD)), and a decompression unit. The image signal from the image reading unit IR is written to a first image memory including a ring buffer and the like of the memory unit 8, then compressed by the compression unit, and written to the code memory. The image data written in the code memory is read out according to an instruction of the CPU of the image reading unit IR or another CPU of the digital copying machine, expanded by the expansion unit, and then stored in a page memory or the like. 2 is written to the image memory unit 2 and then output to the printer unit 2.
[0015]
According to the digital copying machine shown in FIG. 1, an original is read once by the image reading section IR, and the image data is stored in the memory section 8 so that the image data can be read from the memory section 8 a plurality of times. Can make multiple copies. Further, by controlling the memory unit 8, the image can be rotated. Also, 2-in-1 (copying two documents on one sheet) is possible.
[0016]
In particular, when the automatic document feeder FDH is used, the document can be read continuously for many hours until the storage capacity of the memory unit 8 is exhausted. Thus, users can make ever larger numbers of copies.
[0017]
Further, the printer unit 2 in FIG. 1 will be briefly described below. The printer unit 2 controls the modulation of the semiconductor laser 11 based on the image data input from the memory unit 8, scans the laser beam guided to the optical systems 12a and 12b on the photosensitive drum 13, and scans the photosensitive drum 13. A printed image is obtained on paper by an electrophotographic process for developing, transferring, and the like the latent image formed on the recording medium 13. The modulation control of the semiconductor laser 11 includes on / off control, intensity control, PWM (pulse width modulation) control, and the like.
[0018]
Next, the image reading unit IR (particularly, reading processing including an optical system and data calculation processing) according to the present invention will be described with reference to FIG. As shown in FIG. 2, as the light source 3 for illuminating the original 21, a fluorescent lamp 22 that is inexpensive and can obtain a large amount of light with low power consumption is used. The fluorescent lamp 22 is generally a hot cathode tube in which mercury gas is sealed.
[0019]
As shown in FIG. 5, the amount of light of the fluorescent lamp 22 greatly varies depending on the tube wall temperature (ambient temperature). In order to suppress the fluctuation of the light amount, a heater 23 is wrapped around the fluorescent lamp 22, and the heater 23 is an example of a tube wall temperature control unit based on a signal from a temperature sensor 25 such as a thermistor for detecting the tube wall temperature. The temperature is controlled by a certain temperature adjusting circuit 26 so that the tube wall temperature is kept within a predetermined temperature range. This stabilizes the light quantity of the fluorescent lamp 22 and improves the rising characteristics.
[0020]
Further, the light quantity fluctuation of the fluorescent lamp 22 also occurs due to a variation in the mounting position of the fluorescent lamp 22 and a change with time of the fluorescent lamp 22. Further, the light amount differs for each component of the fluorescent lamp 22. Therefore, in the market, it is necessary to adjust the light amount not only when the fluorescent lamp 22 but also the surrounding mechanical parts are replaced.
[0021]
In this embodiment, the fluorescent lamp 22 (hot cathode tube) is used as the light source, but a halogen lamp, a discharge lamp using a rare gas (cold cathode tube), or the like may be used as the light source. In this case, the characteristic of the light amount change is different from that of the fluorescent lamp 22.
[0022]
The dimming inverter 27, which is an example of the light amount control unit, adjusts the light amount of the fluorescent lamp 22 (ie, dimming) by changing the lamp current value. In addition, as a method of the light control, a control method of varying the duty of lighting on / off may be adopted.
[0023]
The dimming inverter 27 is controlled by a digital control signal (dimming value) from the CPU 28 to change a lamp current value input to the fluorescent lamp 22. The digital control signal indicates a light amount level value, that is, a dimming value. As shown in FIG. 6, the relationship between the dimming value and the relative light amount of the fluorescent lamp 22 is a non-linear relationship. Line segments extending up and down from the white circles in the curve represent variations in the relative light amounts depending on the components. By changing the digital control signal in the range of 0 to 255, for example, the relative light amount can be changed in the range of 25% to 100%. The light intensity control by the dimming inverter 27 is used to roughly adjust the light intensity, and is used to prevent a light intensity fluctuation due to a component variation or a temperature change.
[0024]
The CCD 30, which is an example of a reading unit, is a photoelectric conversion element that outputs a voltage linearly with respect to incident light from the lens 31. As shown in FIGS. 7A to 7C, the CCD 30 usually has at least two output systems OS1 and OS2 for high-speed operation. 7, 50 is an output buffer, 51 is a photodiode, and 52, 53, 54, and 55 are transfer registers. 7A shows a normal type with two registers and two outputs, FIG. 7B shows a type with four registers and four outputs, and FIG. 7C shows a type with two registers and four outputs.
[0025]
The CCD is a device whose characteristics vary greatly depending on components. For example, the sensitivity of the CCD 30 varies, for example, by ± 20 to 30% depending on components, and the amount of exposure is adjusted to obtain a certain CCD output voltage. There is a need to. The variation due to the individual difference of the saturation output voltage of the CCD 30 is 20% or more as shown in FIG.
[0026]
In addition, as shown in FIG. 8, for example, the CCD 30 has a large variation in electrical characteristics and signal output delay amount. There are also characteristic differences caused by differences in the output system of the CCD 30, and characteristic differences caused by chip warpage. Furthermore, there are variations in MTF (modulation transfer function) characteristics and spectral sensitivity characteristics, and variations in pixel positions with respect to the package. Therefore, the characteristic values of the CCD measured in advance and the values to be referred to when performing various processes are stored in the storage means in the product when assembling the CCD unit or the product.
[0027]
The reading processing unit IR includes a CDS unit 32 having a sample and hold function represented by CDS (correlated double sampling), an AMP (amplifier) unit 33 having an amplification function, and a clamp unit 35 having a clamp function. Have. Further, the reading processing unit IR has a quantizing function, an output synthesizing function, and the like, which will be described later.
[0028]
The CDS unit 32 calculates a difference between a signal in a period representing a black output and a signal in a signal period in one pixel of the CCD 30 by two input sampling pulses, thereby obtaining a waveform of the waveform output from the CCD 30. Except for a noise portion generated by the drive pulse (RS), only a stable portion of the signal output is extracted. Here, variations in the temperature characteristics of the CCD 30 itself are absorbed. The causes of variation in the CDS unit 32 include errors due to differences in sampling positions, in addition to variations in gain of the CDS 32 itself (about ± 30%) and variations in input signal amplitude limitation (for example, 1 V).
[0029]
When high-speed operation is performed, since the period of one pixel is very short, a lot of noise occurs in the CCD output waveform. Therefore, in order to hold correct data, the sampling pulse width is set to ns (10 ^-9 Second), and the adjustment of the sampling position is also ns (10 ^-9 Seconds) must be performed in order. Therefore, a timing fine adjustment circuit 88 as shown in FIG. 9 is required. The timing fine adjustment circuit 88 is a circuit for finely adjusting the sampling pulse width and the sampling timing.
[0030]
As shown in FIG. 10, the timing fine adjustment circuit 88 adjusts the pulse width and the timing by controlling the timing of at least one or more reference pulses CK. Then, the control value of the adjustment is stored in the storage means at the time of assembly adjustment, and at the time of product operation, the CPU 28 reads the control value and sets it in the timing adjustment circuit 88. Here, the CDS unit 32 performs correlated double sampling as the sample and hold function, but may have another sample and hold function.
[0031]
The AMP unit 33 amplifies the signal sampled and held by the CDS unit 32 with an operational amplifier. Here, the amplification factor (also referred to as gain) varies due to variations in the characteristics of the operational amplifier itself and variations in elements (such as resistors) that determine the amplification factor. Here, the amplification factor of the AMP unit 33 is fixed (excluding variations and characteristic changes). However, similarly to the clamp unit 35 described below, the amplification factor of the AMP unit 33 is set to a D / A converter. It may be arbitrarily variably controlled by using the above.
[0032]
Next, the clamp unit 35 has a D / A converter, inputs a setting signal from the CPU 28 to the A / D converter 37 via the D / A converter, and sets the black reference voltage of the CCD 30 to A / D. The black reference voltage of the CCD 30 is changed to an arbitrary level so as to be at the lower limit voltage level of the / D converter 37. Thereby, optimal quantization of the CCD output can be achieved. Factors of variation in the clamp unit 35 include variations in the gain of the D / A converter itself, conversion errors, and variations in the reference voltage, in addition to variations in the clamp unit 35 itself. Here, the black reference voltage of the CCD 30 refers to a voltage output when the pixels of the CCD 30 are optically shielded. By adjusting the black reference voltage of the CCD 30 to the level set for each line, it is possible to absorb a temporal change in temperature characteristics of the CCD 30 and other elements and circuit systems.
[0033]
Next, the A / D converter 37 arbitrarily varies the reference voltage (top side) with a signal from the CPU 28 via the D / A converter, and aims at the CCD output voltage from the clamp unit 35. In the reading density range. The A / D converter 37 quantizes (converts to digital signals) the CCD output voltage into, for example, 256 gradations. In addition, since the period of one pixel is very short at the time of high-speed operation, the A / D converter 37 needs a fine adjustment circuit for adjusting the (quantization) sampling position, similarly to the CDS unit 32. The A / D converter 37 can set the maximum quantization range at a level that does not saturate even if the CCD output voltage and the circuit gain are the maximum values. As in the case of the clamp unit 35, the causes of variation in the A / D converter 37 include the gain and conversion error of the D / A converter itself, and variations in its reference voltage. In addition, there is a possibility that data to be quantized may vary (error) depending on the sampling position.
[0034]
Next, the output synthesizing unit 38 synthesizes the two digital signals that have been subjected to the parallel processing according to the two outputs of the CCD 30 into a serial signal in the order of the pixels read by the CCD 30. Here, the timing of the synthesized clock for synthesizing the outputs is important. In particular, when the operation of the CCD 30 is high-speed or the output of the CCD 30 becomes three or more, the timing margin at the time of synthesizing is further reduced. It is necessary to make fine adjustments in accordance with the timing of the A.D. Of course, the timing may be fixed, but may be varied according to the CCD output delay time stored in advance, or may be varied in conjunction with the sampling timing of the CDS unit 32 or the like.
[0035]
Next, the shading correction unit 40 uses the CCD 30 to detect the uneven light distribution of the exposure lamp 3, that is, the fluorescent lamp 22, the total uneven light distribution of the optical system due to the sag around the lens 31, and the sensitivity unevenness of each pixel of the CCD 30 as shown in FIG. The correction is performed by performing arithmetic processing based on the data of one line read from the white reference density plate 41 (shading correction plate) shown in FIG. In this embodiment, since the exposure lamp 3 is constituted by the fluorescent lamp 22, dripping (light quantity reduction) in the peripheral portion is large. When the exposure lamp 3 is formed of a halogen lamp, there is a light amount ripple at the filament.
[0036]
The image monitor 45 has a function of causing the CPU 28 to monitor one-line data in the main scanning direction by hardware. The monitoring function includes the following. (1) The CPU 28 directly monitors data of at least one point (specific address) of one line. (2) One line of image data in the main scanning direction is stored in the memory 46, and the CPU 28 monitors the image data in the memory 46. (3) A histogram of one line or a plurality of lines is created, and the result is monitored by the CPU 28. (4) The edge address of one or more lines is detected, and the result is monitored by the CPU 28. Further, a ROM 101 and a RAM 102 are connected to the CPU 28.
[0037]
In this embodiment, the processing circuit from the CCD 30 to the A / D converter 37 and the output synthesizing unit 38 is configured as a single substrate, in addition to the device of the substrate wiring pattern and the enhancement of GND (ground). As a result, external noise and radiation noise are reduced, and S / N degradation due to an increase in noise during high-speed operation is reduced.
[0038]
In this embodiment, the imaging lens 31, the substrate, and its holding member are formed as one unit (hereinafter, referred to as a CCD unit), and mechanical adjustment such as a focus position in the unit is performed. I have. This makes it easy to replace parts on the market.
[0039]
Further, the substrate has a memory 46 including an electrically readable and writable storage means for storing the read characteristics as described above during assembly adjustment. The storage means may be, for example, a semiconductor such as a memory, or a non-semiconductor such as a dip switch or a substrate pattern for reading only. The reading characteristics stored in the memory 46 include the following. First, the following information (i) to (v) are stored in advance.
[0040]
(I) variations in CCD reading characteristics, such as sensitivity, saturation output voltage, and differences in electrical characteristics such as differences in characteristics of two or more output systems with respect to standard values,
(Ii) Analog total gain, for example, S / H (sample hold) gain, input limiting voltage, gain of amplification processing section (AMP section 33), gain of clamp section 35, quantization section (A / D converter 37) Variation of the gain relative to the standard value,
(Iii) sampling timing information, that is, timing control values of the CDS unit 32 as an S / H (sample and hold) unit, the A / D converter 37 as a quantization unit, the output synthesizing unit 38, etc.
(Iv) Exposure amount and initial data, that is, a dimming value determined by a combination of an optical component such as a lamp at the time of assembly and the above-mentioned CCD unit, a digital value at the time of reading a reference white plate, and a value indicating a light distribution ratio.
(V) Information required at the time of assembly adjustment.
[0041]
Information that may be rewritten during assembly adjustment or product operation includes the following (vi) to (ix).
[0042]
(Vi) In various adjustments, when the adjusted value is apparently abnormal, a default value to be set as a temporary value,
(Vii) Abnormality or caution, location of trouble occurrence and its frequency,
(Viii) The number of times of reading in the case of manual placing, automatic document feeding, double-sided printing, etc.
(Ix) Lamp lighting frequency.
[0043]
Next, various adjustments and correction items will be described below in the order of (a) first light amount adjustment, (b) second light amount adjustment, (c) offset adjustment, and (d) gain adjustment.
[0044]
(A) The first light amount adjustment involves light amount peak detection, and is performed at the time of power-on or software reset at the time of assembly adjustment or replacement of parts in the market. Here, the component replacement includes not only the fluorescent lamp 22 but also mechanical components (reflector of the imaging optical system 5, a fluorescent lamp holding member, etc.) that determine the amount of light incident on the CCD 30, and a CCD unit. . The CCD unit is, as described above, a single substrate for performing signal processing from the lens 31 and the CCD 30 to the output synthesizing unit 38 and a component unit for holding and positioning them, and is easily replaceable. Things.
[0045]
(B) The second light amount adjustment is performed to absorb a decrease in light amount during continuous reading. When a large number of documents are read by the automatic document feeder FDH, the fluorescent lamp 22 may be continuously turned on for hours. The fluorescent lamp 22 is continuously turned on when reading an image that can be stored in the image memory unit 8 composed of a hard disk or when image output is processed in parallel. When the fluorescent lamp 22 is continuously turned on, the tube wall temperature (ambient temperature) of the fluorescent lamp 22 increases due to the self-heating of the fluorescent lamp 22 and the heat generated from the CCD 30 and the substrate. As a result, the light amount is reduced by about 30 to 50% from the light amount immediately after lighting. Therefore, the CPU 28 estimates the CCD output voltage for the value adopted when the gain adjustment described in the following item (d) is performed, as in the case of the first light amount adjustment, and determines the estimated CCD output voltage as the image quality. When the CCD output voltage falls below the lower limit corresponding to the guarantee, a dimming value, that is, a light amount level value is set immediately before the next gain adjustment timing so as not to fall below the lower limit.
[0046]
In the following (c) offset adjustment and (d) gain adjustment, since the light amount adjustment cannot be performed with the accuracy of the quantization step (256 gradations), it is positioned as a fine adjustment function after the approximate light amount adjustment.
[0047]
(C) In the offset adjustment, the clamp voltage is controlled so that the digital value of the CCD output voltage becomes “0” at least when the power is turned on while the pixels of the CCD 30 are optically shielded. That is, the black level at the time of reading is adjusted. The digital value of the CCD output voltage in the optically shielded state differs depending on the system.
[0048]
(D) In the gain adjustment, since the light quantity fluctuation of the fluorescent lamp 22 is large, basically, the original 2
(D) In the gain adjustment, since the light quantity fluctuation of the fluorescent lamp 22 is large, basically, the original 2
The reference voltage of the A / D converter 37 is controlled immediately before the start of reading 1 so as to perform optimal quantization during reading of one page.
[0049]
[Trouble / Warning processing]
Next, the trouble / warning process will be described. At the time of the gain adjustment, the CCD output voltage is estimated from the light amount monitor value read from the reference density plate 41, and when the voltage falls below the lower limit of the image quality guarantee, a warning indicating replacement of the light source lamp (fluorescent lamp 22) is issued. If the output is extremely low, or if the amount of light is extremely low, a trouble is reported. The notification may be displayed on an operation panel, notified to a service base using a telephone line or the like, or the machine may be stopped.
[0050]
The brightness of the fluorescent lamp 22 gradually decreases as the lighting time elapses. The major causes of the decrease in brightness include deterioration and coloring of the phosphor due to impurity gas remaining in the tube at the time of manufacture, deterioration of the phosphor due to ultraviolet rays, and coloring of the glass tube due to ultraviolet rays. Generally, the decrease in brightness of the fluorescent lamp 22 is large at the beginning, and the decrease thereafter is gradually reduced.
[0051]
FIG. 11 shows the time-dependent deterioration characteristics of the fluorescent lamp 22. In FIG. 11, the horizontal axis indicates the cumulative lighting time of the fluorescent lamp, and the vertical axis indicates the brightness maintenance rate when the brightness when new is 100%. The counter value is shown below the horizontal axis indicating the cumulative lighting time. This counter value is the sum of the number of times a manual document is read and the number of times the automatic document feeder FDH has passed. The number of readings is a number counted by a counter provided in advance for the durability management of the scan motor. Is the number of times Therefore, it is not necessary to install a new counter for obtaining the counter value, and it is possible to avoid an increase in cost.
[0052]
The cumulative lighting time is a value obtained by multiplying the total reading number by the time (for example, 2 seconds) required to read an A3-size original at the same magnification, using the counter value as the total number of readings. However, in actual operation, there is a change in the original, paper size, and magnification. In addition, once for one-sided copy, for two-sided copy, for mixed originals, and for detecting the original size, once. The reading time per hit changes. In this embodiment, the lighting time is estimated to be longer than the actual case where the A4 size document is read based on the A3 size document reading time, and the light amount correction is performed at an earlier timing.
[0053]
In this embodiment, in FIG. 11, the light amount correction is performed every time the brightness maintenance ratio decreases by 5%. Therefore, when the counter value exceeds 90,000 times, 210,000 times, 390,000 times, 600,000 times, and 900,000 times, light amount correction is performed. The data representing the light amount correction timing is stored in the ROM 101 connected to the CPU 28 shown in FIG. 2 in advance.
[0054]
Next, an initial operation when the power is turned on in this embodiment will be described with reference to a flowchart of FIG. The initial operation at power-on includes an operation equivalent to power-on such as trouble reset.
[0055]
First, when the power is turned on, the process proceeds to step S1, in which a timer is started to start time measurement. Next, the slider 71 of FIG. 1 is moved to a predetermined reference position. Next, the slider 71 is moved to a position facing the reference density plate 41. Next, offset adjustment is performed.
[0056]
Next, the process proceeds to step S2, where it is determined whether or not the light amount correction timing has come. That is, it is determined whether the counter value has exceeded the counter value stored in the ROM 101 (90,000, 210,000, 390,000, 600,000, 900,000 times). If it is determined that the light amount correction timing is reached, the process proceeds to step S3. If it is determined that the light amount correction timing is not reached, the process proceeds to step S6, and the fluorescent lamp 22 is turned off. Step S2 constitutes a light quantity correction timing determination unit.
[0057]
In step S3, after the fluorescent lamp 22 is turned on, the process proceeds to step S4. In the above step S4, the light amount peak is detected, the dimming value is determined in step S5, the dimming value is written in the memory 46 as backup data, and the process proceeds to the next process (step S6). Steps S4 and S5 correspond to the first light amount adjustment (also warm-up and dimming irregular removal).
[0058]
In step S6, the lamp is turned off, the timer is stopped, the slider is moved to a predetermined reference position, and the startup is completed.
[0059]
As described above, according to this embodiment, when the number of times of reading the original exceeds 90,000, 210,000, 390,000, 600,000, and 900,000 times, respectively, Since the light amount correction timing according to the aging of the fluorescent lamp 22 is set, the frequency of correction is suppressed, and the decrease in brightness due to the aging of the fluorescent lamp 22 is compensated, so that both productivity and image quality can be achieved. In this embodiment, the light amount correction timing is determined based on the number of times the document has been read, but the light amount correction timing may be determined based on the lighting time of the fluorescent lamp 22. However, when the light amount correction timing is determined based on the number of times the original has been read as in this embodiment, the existing counter can be used as described above, so that cost increase can be prevented.
[0060]
Here, the printer unit 2 controls the power supply of the heater 23 for the temperature control of the fluorescent lamp 22 in the same manner as the heater of the fixing unit by receiving the temperature control information from the CPU of the printer unit 2. The reason is that, in the energy saving mode in which the standby time can be set by the user, the power of the image reading unit IR is turned off to minimize the power consumption, and the reading is immediately performed simultaneously with the fixing by the printer unit 2 when returning. This is so that we can start.
[0061]
Further, in the lighting control of the fluorescent lamp 22, after the appropriate preheating time of the fluorescent lamp 22 has elapsed, regardless of the dimming value to be turned on, the light is once turned on at a dimming value of 100%, and after a predetermined time, the dimming value is changed. Control to the desired value. The reason for this is to prolong the life of the fluorescent lamp 22 and to prevent non-lighting at low temperatures and low dimming values.
[0062]
In addition, when adjusting the light amount, since conditions such as the ambient temperature and the time during which the fluorescent lamp 22 has been turned off are not known except at the time of assembling adjustment, the light amount change curve is obtained by the following method (see FIG. 3). Is estimated, and the dimming value is determined. The light quantity change curve can be estimated by using a relative value of the light quantity, but it is necessary to know the absolute light quantity in order to determine an optimal dimming value that does not saturate the CCD output. In addition, when the image quality is emphasized, it is necessary to grasp the minimum required light amount similarly to the saturation prevention. Further, the minimum required light amount may be changed according to the reading mode (character mode, photo mode, etc.).
[0063]
The first light amount adjustment performed in steps S4 and S5 in FIG. 12 will be described in detail in the next section (Details of the first light amount adjustment), but the outline will be described here. In the first light amount adjustment, the CPU 28 waits after the lamp is turned on based on a light amount change pattern that can be generated in advance based on a dimming value for lighting, and then starts monitoring the change in light amount. Then, a peak light amount and a light amount change curve are obtained, and an optimum dimming value that can absorb a light amount change due to an ambient temperature at this time or a light amount change at the time of re-lighting is estimated and set.
[0064]
Next, characteristics of the rising light amount change will be described.
[0065]
As shown in FIG. 3, there are three types of rising light amount change curves 1, 2, and 3 depending on the lighting conditions of the fluorescent lamp 22. In the light amount change curves 1, 2, and 3, the time transition and the peak value change depending on the ambient temperature, the previous lighting condition, the standby time, and the like.
[0066]
The light amount change curve 1 in FIG. 3 is a standard curve and is a general rising characteristic curve. The light quantity change curve 2 is a semi-standard type characteristic curve also called a peaky type. This quasi-standard type characteristic curve is a relatively rare characteristic that may occur depending on the temperature condition in the tube of the fluorescent lamp 22. Further, the light amount change curve 3 is called an instantaneous interruption type, and is a characteristic curve when the power is turned off and then turned on again for a short time. Therefore, the light amount change curve 3 approaches the light amount change curve 1 as the power-off time before the re-input becomes longer.
[0067]
(Details of the first light amount adjustment)
Next, the first light amount adjustment of this embodiment will be described in detail with reference to the second flowchart of FIGS.
[0068]
0. First, various initial settings are performed based on the read data of the reference density plate 41 so that the absolute light amount of the fluorescent lamp 22 can be measured. That is, the slider 71 is moved to the reference density plate 41, and the variables (the maximum value, the number of continuous light amount change tendencies, etc.) used for the processing are initialized. Then, the fluorescent lamp 22 is turned on, and time counting by the timer is started. (Steps S11 and S12)
1. Next, a predetermined time for light amount peak detection is waited while referring to the timer value. For example, it waits for 1 minute and 15 seconds. (Step S13)
2. Next, data at a specific point is sampled every second after the lamp (fluorescent lamp 22) is turned on. The data is the amount of light of the fluorescent lamp 22 read from the reference density plate 41 by the CCD 30. The specific point is a point indicating a predetermined main scanning light distribution peak when the light amount is stable. The sampling of the data uses the average value of a plurality of pixels instead of one point to improve the accuracy of the data. Further, of the first average value data, only the one with the larger light amount of ODD / EVEN in the output system of the CCD 30 is adopted as data in the subsequent processing to simplify the data processing. (Step S14)
3. Next, the maximum value of those data is detected and stored in the memory 46 (peak hold). On the other hand, the light amount is sampled every second, and the light amount change amount (difference / vector) in five seconds is obtained. (Step S15)
[0069]
That is, for example, sampling is performed in the following manner: (1) (data at 0 second), (2) (data at 1 second),... (6) (data at 5 seconds). , ((6)-(1)).
[0070]
4. Next, the light amount change tendency is determined from the light amount change amount obtained as described above (step S15). Specifically, a comparison is made between the amount of change in light amount ([6]-[1]) and the allowable range a. That is,
If | (6)-(1) | ≦ a, it is determined that the light amount is stable (no change).
[0071]
If (6)-(1)> a, it is determined that the light amount is increasing.
[0072]
If (6)-(1) <-a, it is determined that the light amount has decreased.
[0073]
Note that the allowable range a is not a fixed value but is changed according to the absolute value of data (light quantity). The reason is that the variation of the absolute value of the output data due to the component variation is large, and the data of the circuit system also varies. Therefore, if the allowable range a is set to a fixed value, the change tendency of the light quantity cannot be correctly determined. It is.
[0074]
5. Next, in step S16, the light amount peak is detected based on the continuity of the light amount change tendency, and if it is determined that the light amount peak has been detected, the following processes 1 to 3 are performed to determine the light amount change curve. I do.
[0075]
[Process 1] (Step S17) In this process 1, it is determined whether or not the light amount change curve is the light amount change curve 3 shown in FIG.
[0076]
That is, if (the number of continuous light quantity increases ≧ 5) or (the number of continuous light quantity reductions ≧ 5) or (the number of continuous light quantity stable ≧ 5) after the elapse of the light quantity peak detection standby time, the light quantity change curve is instantaneous. It is determined that the type is other than the disconnect type.
[0077]
If it is determined in step S17 that the light amount change curve is the instantaneous interruption type, the timer is stopped (S22), and the process proceeds to the dimming value determination process (step S5) in the first flowchart of FIG. On the other hand, if it is determined in the processing 1 that the light amount change curve is not the instantaneous interruption type, the following processing 2 is performed.
[0078]
[Process 2] (Steps S18, S19, S20) In this process 2, it is determined whether the type of the light amount change curve is the light amount change curve 1 or the light amount change curve 2 in FIG. 3, that is, whether the type is the standard type or the quasi-standard type. . That is, when the number of continuous light quantity reductions ≧ 10, it is determined that the light quantity change curve is the standard type.
[0079]
On the other hand, if the light amount change curve cannot be determined to be the standard type even after elapse of 20 seconds from the first time of this process 2, the light amount change curve is determined to be the quasi-standard type.
[0080]
Then, in this process 2, when it is determined that the light quantity change curve is of the standard type, the process proceeds to the dimming value determination process (step S21). On the other hand, if it is determined in the processing 2 that the light amount change curve is of the quasi-standard type, the process proceeds to the next [processing 3], the dimming value determination processing (step S25).
[0081]
[Process 3] (Steps S23 and S24) In this process 3, the valley value of the light amount change curve 2 of the semi-standard type is detected. That is, when the light amount increase or the light amount stabilization continues for 5 seconds, the current light amount data average value is set as the valley value.
[0082]
Note that the light amount peak value is the maximum value stored so far.
[0083]
And the above item 2.3.4.5. Is repeated for each data sampling until the peak of the light quantity change curve is obtained.
[0084]
6. Next, an optimum dimming value to be set is determined from the peak value (or valley value) of the obtained light quantity change curve, and a dimming value is set for the dimming inverter 27 in FIG. Means (EEPROM). The optimum dimming value here is a dimming value such that the light intensity peak does not exceed the CCD saturation level due to continuous lighting at the time of reading after setting and environmental fluctuation.
[0085]
Specifically, when the light amount change curve is determined to be the standard type, the optimum dimming value is obtained by the following equation (1). When the light amount change curve is determined to be the quasi-standard type, the optimum light control value is determined. The dimming value is obtained by the following equation (2), and when it is determined that the light quantity change curve is of the instantaneous interruption type, the previous setting value stored in the storage means (EEPROM) is used as it is.
[0086]
(1) Optimal dimming value (standard type) =
｛(Target value) × (total gain) / (peak value) × b｝ × (current dimming value)
(2) Optimal dimming value (quasi-standard type) =
{(Target value) x (total gain) / (peak value x 1.1) x b} x (current dimming value)
In the above equations (1) and (2), the (target value) is a value at which the CCD output does not saturate when the CCD sensitivity and the analog total gain are standard values. This target value may be a fixed value or may be changed based on a CCD saturation output voltage stored in advance. The term (total gain) indicates a variation of the CCD sensitivity and the analog gain from a standard value. Further, the constant (b) is a ratio between the peak generated by the dimming value and the light amount at the time of stability.
[0087]
In this embodiment, when it is not determined that the light amount peak is detected in step S16 of the flowchart of FIG. 13, the process returns to step S14 via the determination of step S26. Here, in step S26, it is determined whether or not the time counted by the timer has exceeded three minutes. If it is determined that the time has exceeded three minutes, it is determined that a trouble has occurred, and a trouble has occurred on the display panel. Is displayed. Examples of the contents of the above-mentioned troubles include lamp failure, heater failure, optical axis deviation, harness abnormality, power supply abnormality, CCD substrate failure, digital substrate failure, and the like. When the power is turned on, the CPU 28 reads out these pieces of information, that is, (target value), (total gain), and (constant (b)) from the storage means (memory 46) in advance and stores the information in the allowable range a or A trouble determination value for insufficient light quantity and a dimming value calculation formula may be determined. In addition, the sampling time, the number of times of sampling, the time used for determination, a constant, and the like may be set to numerical values for each device.
[0088]
Further, in this embodiment, the light amount peak detection is performed only at the light amount adjustment timing for a high-speed system. However, in a system with sufficient time, this method is always performed immediately before reading (before gain adjustment). By performing the dimming control described above, more accurate dimming can be performed, and a device with higher image quality can always be provided.
[0089]
In this embodiment, since the warm-up time of the printer unit 2 is generally longer than the warm-up time (first light amount adjustment time) of the image reading unit IR, the peak detection standby time is set to a fixed value. However, since the light intensity rising characteristic changes depending on the dimming value at the time of lighting (it is also affected by the ambient temperature), the peak detection standby time is varied according to the dimming value so that the reading start time is shortened as much as possible. You may.
[0090]
In the data sampling process in “item 2.” of the above embodiment, when it is detected from the sampled light amount data that the fluorescent lamp 22 (lamp) is saturated or not lit, the display panel is displayed. A trouble display may be performed. The trouble detection formula in this case is shown in the following formula. When the light quantity data does not satisfy this trouble detection formula, it is determined that a trouble due to saturation has occurred.
[0091]
Light intensity data <{(CCD saturation voltage × analog gain value) / (quantization voltage range)} × 255
Then, when it is determined that the light amount data is saturated, (i) the dimming value is reduced by one step, and the data sampling process is restarted from the beginning without storing the dimming value in the memory. This prevents an erroneous dimming value from being set due to the dimming control being disabled. When the saturation is determined, (ii) when the dimming value is the lower limit, it is determined that the saturation trouble is caused by abnormal lighting of the fluorescent lamp. If the sampling data is at the non-lighting level (minimum) for a predetermined period, it is determined that the lamp is out of trouble.
[0092]
Further, when the light amount change curve determination processing in “item 5” of the above embodiment does not end even after the maximum warm-up time (for example, 5 minutes) of the printer unit 2 of the copying machine has elapsed, a timeout trouble is generated. May be displayed on a display panel or the like.
[0093]
Next, the second light amount adjustment and the gain adjustment in this embodiment will be described.
[0094]
As shown in FIG. 4, when the fluorescent lamp 22 is continuously lit for a long time, the light amount of the fluorescent lamp 22 increases by about + 20% to −40% with respect to the light amount immediately after the lighting due to a rise in the tube wall temperature (ambient temperature). Is known to fluctuate. Note that this fluctuation value changes depending on the system configuration, the temperature control temperature, and the like. In particular, when the temperature is low, the change in the amount of light in units of time is large when the amount of light rises after lighting, and the decrease in the amount of light after the peak is small. On the other hand, when the temperature is high, the light quantity rise after lighting is small, but the light quantity change (decreased absolute light quantity) per unit time at the light quantity fall after the peak tends to be large.
[0095]
Since it is difficult to accurately grasp the tube wall temperature (ambient temperature) at the time of reading the document, the light amount change during the document reading is determined based on the light amount change curve having the largest light amount variation as shown in FIG. The light amount is corrected so that it always falls within the allowable range for guaranteeing the image quality. This light amount correction includes dimming control for adjusting the output of the dimming inverter 27 and gain adjustment for adjusting the amplification factor of the amplifier.
[0096]
Next, operations of the second light amount adjustment and the gain adjustment of this embodiment will be described with reference to a third flowchart shown in FIGS. 15 and 16 and a fourth flowchart shown in FIG.
[0097]
First, the CPU 28 executes gain adjustment based on information such as a document size and a reading mode set from an operation panel or the like in accordance with the temporal change characteristic curve of the light amount (FIG. 4) stored in the memory 46 in advance. The timing is determined (step S31). The CPU 28 determines the execution timing of the gain adjustment immediately before the document reading timing at which it is predicted that the fluctuation of the light intensity after the previous gain adjustment is not tolerable in guaranteeing the image quality in view of the time variation characteristic of the light intensity.
[0098]
Next, the fluorescent lamp 22 is turned on (step S32), and before reading the first page of the document 21, the slider 71 of FIG. 1 is moved to a position facing the reference density plate 41 (step S33). The read data of one line 41 in the main scanning direction is stored in the image monitor 45 of FIG. Then, the CPU 28 obtains the maximum value (light amount monitor value) of the read data, and performs light amount correction (gain adjustment) so as to perform optimal reading (step S34).
[0099]
After the optimal quantization dynamic range is set by the gain adjustment, shading correction data for light distribution correction is fetched, and image reading is started at the reading position by the automatic document feeder FDH (step S35, S36).
[0100]
Next, the process proceeds to step S37, where it is determined whether there is a next document. If it is determined that there is a next document, the process proceeds to step S41. If it is determined that there is no next document, the process proceeds to step S38. In step S38, the lamp (the fluorescent lamp 22) is turned off, and the shading correction ends. Then, the process proceeds to step S39, where it is determined whether a warning or trouble has occurred. If it is determined that no warning or trouble has occurred, the process ends. On the other hand, if it is determined that a warning or a trouble has occurred, the process proceeds to step S40, where the warning or the trouble is displayed, and the processing for them is executed.
[0101]
On the other hand, in step S41, when it is determined that the above-mentioned gain adjustment execution timing set in step S31 has come, the process proceeds to step S42, and whether or not it is the dimming value variable timing, that is, the dimming value variable flag is turned on. It is determined whether or not. On the other hand, if it is determined in step S41 that the gain adjustment timing has not come, the process returns to step S36 to perform image reading. The dimming value variable flag is a flag that is turned on in S57 of FIG.
[0102]
If it is determined in step S42 that the timing is not the variable light control value timing, the process returns to step S33, and the slider 71 is moved from the reading position 4 by the automatic document feeder FDH to the position facing the reference density plate 41. Then, the process proceeds to step S34, and the light amount correction and the light distribution correction are performed at the opposed position. In the light amount correction, gain adjustment is performed to decrease or increase the gain in accordance with the excess or deficiency of the gain, and in the light distribution correction, shading correction data is fetched. Thereafter, the slider 71 is returned to the position 4 for continuous document reading.
[0103]
On the other hand, if it is determined in step S42 that the dimming value variable flag is ON, the process proceeds to step S43, where it is determined whether the dimming value is 100%. If it is determined that the above condition is satisfied, the process proceeds to step S45, and the warning flag is turned on. On the other hand, if it is determined in step S43 that the dimming value is not 100%, the process proceeds to step S44, where the dimming value is changed, and the process returns to step S33.
[0104]
Next, the gain adjustment in step S34 will be described with reference to the flowchart in FIG. First, in step S51, initialization is performed, and shading correction is turned off. Next, proceeding to step S52, it is determined whether or not the slider 71 is located at the position facing the reference density plate 41. If it is determined that the slider 71 is located at the facing position, the process proceeds to step S53 to monitor the light amount. That is, the read data of one line in the main scanning direction of the reference density plate 41 is stored in the image monitor 45, and the light amount monitor value that is the maximum value of the read data is obtained. Next, the process proceeds to step S54, where it is determined whether or not the light amount monitor value is within the image quality guarantee range. If the light amount monitor value is out of the image quality guarantee range, the process proceeds to step S57, and the light amount monitor value is set to the image quality guarantee range. If so, the process proceeds to step S55. In step S57, the dimming value determination variable flag is set, and the dimming value (that is, the output current value of the dimming inverter 27) is determined so that the optimal light amount is obtained at the next gain adjustment. .
[0105]
As described above, from the time when the image reading in step S36 is started and the output of the original image is completed, the time when the slider 71 is moved to the position of the reference density plate 41 in step S33, the steps S37 and S37 are performed. Through S41, S42, S43, and S44, in this step S44, the dimming inverter 27 is set to the dimming value determined in advance in step S57. Therefore, since the light quantity fluctuation during reading due to the change of the light control value before reaching the reference density plate 41 is eliminated, the gain adjustment processing can be performed in the light quantity stable state, and the deterioration of the image quality can be prevented. Further, since no special time is required only for the light amount correction, the productivity can be improved.
[0106]
Next, the process proceeds to step S55 to determine and set the gain adjustment value, and then proceeds to step S56 to fetch the shading correction reference data and end the gain adjustment process.
[0107]
In the above description, the fluctuation of the light amount is described, but the light distribution also changes at a smaller rate than the fluctuation of the light amount. For this reason, when correcting the light amount fluctuation, the shading correction data may also be taken in at the same time in step S35 to correct the light distribution. Thus, the number of reciprocating movements in which the slider 71 is moved to the reference density plate 41 (shading plate) and then returned to the document reading position 4 can be reduced. Therefore, the read image quality can be improved while minimizing the decrease in productivity. In this case, in addition to the light quantity change curve shown in FIG. 4, a light distribution temporal change characteristic curve may be stored in the memory 46. In some cases, only the light distribution correction may be performed instead of the light amount correction.
[0108]
In addition, a mark x on a broken line extending parallel to the time axis in FIG. 4 indicates an example of the gain adjustment execution timing. Numerical values described below the line segment between the X mark and the adjacent X mark represent the number of documents to be read at the time between the X marks and the X mark. In this example, the permissible level of the light quantity fluctuation with respect to the image quality when reading one page of the document is set to 5% or less, and the time required for reading one page and the processing for moving the slider 71 to perform light quantity correction and light distribution correction are required. In consideration of time, the timing for executing the gain adjustment is determined. As can be seen from FIG. 4, it can be seen that the frequency of gain adjustment is high at the beginning of lighting, and the change in the amount of light gradually decreases with time, and the frequency of gain adjustment gradually decreases.
[0109]
By the way, when the distance between the reference density plate 41 and the document reading position 4 is 50 mm and the moving speed of the slider 71 is 400 mm / sec, the time required for the gain adjustment (that is, the reciprocating movement of the slider 71 is required). Time) is 0.5 seconds or more. Therefore, for example, assuming that gain correction is performed for each page in a high-speed system of 60 ppm (sheets / minute), it takes about 30 seconds for correction to copy 60 sheets. Therefore, in order to achieve 60 ppm after performing the gain adjustment during the reading, it is necessary to achieve a capability equivalent to 90 ppm in a system that does not perform the gain adjustment during the reading. This means that the difficulty for achieving mechanical reliability and durability is significantly increased.
[0110]
Therefore, by setting the timing of the gain adjustment based on the temporal change curve of the light amount as in the above-described embodiment, the number of times the gain adjustment is performed is reduced to a necessary minimum, and the gain adjustment during the reading is not performed. With less than 70 ppm mechanical capacity in the system, it is possible to achieve 60 ppm copy capacity when performing gain adjustment during reading.
[0111]
【The invention's effect】
As is apparent from the above, according to the image reading apparatus of the first aspect of the present invention, the light quantity correction timing determination means determines the light quantity correction timing by the light quantity correction means based on the lighting time of the light source. The timing for correcting the light amount can be determined according to the degree of the light quantity. Therefore, it is possible to balance the productivity and the image quality by compensating for the decrease in brightness due to the deterioration of the light source over time while suppressing the frequency of light amount adjustment.
[0112]
According to the second aspect of the present invention, the light quantity correction timing determination means determines the light quantity correction timing by the light quantity correction means based on the number of times of reading the document, so that the light quantity correction timing according to the degree of deterioration of the light source with time. You can decide when. Therefore, it is possible to balance the productivity and the image quality by compensating for the decrease in brightness due to the deterioration of the light source over time while suppressing the frequency of light amount adjustment. According to the second aspect of the present invention, the number of times the original is read can be counted by the existing counter, so that the light amount can be compensated at low cost.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a digital copying machine including an embodiment of an image reading apparatus of the present invention.
FIG. 2 is a block diagram of the embodiment.
FIG. 3 is a diagram showing three typical examples of a rising characteristic of a fluorescent lamp included in the embodiment.
FIG. 4 is a diagram showing a continuous lighting characteristic of the fluorescent lamp.
FIG. 5 is a temperature characteristic diagram showing how the relative light output of the fluorescent lamp changes depending on the ambient temperature.
FIG. 6 is a diagram showing a relationship between a dimming value (control value) output from the dimming inverter of the embodiment and a light amount (dimming value) of a fluorescent lamp.
FIG. 7A is a schematic diagram showing a two-register two-output type as a configuration example of the CCD according to the embodiment, and FIG. 7B is a four-register four-output type as a configuration example of the CCD; FIG. 7C is a schematic diagram showing a 2-register 4-output type as a configuration example of the CCD.
FIG. 8 is a table showing an example of electrical characteristics of the CCD according to the embodiment.
FIG. 9 is a block diagram illustrating an example of a timing fine adjustment circuit according to the embodiment.
FIG. 10 is a timing chart of the timing fine adjustment circuit.
FIG. 11 is a graph showing the aging characteristics of a fluorescent lamp when the amount of light when new is 100%.
FIG. 12 is a first flowchart illustrating a start-up operation of the embodiment.
FIG. 13 is the first half of a second flowchart for explaining the light intensity peak detection operation of the fluorescent lamp according to the embodiment.
FIG. 14 is the second half of the second flowchart.
FIG. 15 is a first half of a third flowchart for explaining light amount correction during continuous reading of originals according to the embodiment.
FIG. 16 is the latter half of the third flowchart.
FIG. 17 is a fourth flowchart illustrating the light amount correction (gain adjustment) operation in the embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Print processing unit, 2 ... Printer part, 3 ... Exposure lamp,
5 imaging optical system, 6 image sensor, 7 image processing unit,
8: memory unit, IR: image processing unit, FDH: automatic document feeder,
10: platen, 11: semiconductor laser, 12: optical system,
13: photosensitive drum, 21: original, 22: fluorescent lamp, 23: heater,
25 temperature sensor, 26 temperature adjustment circuit, 27 dimming inverter,
28 CPU, 30 CCD, 31 lens
32 ... CDS part, 33 ... AMP part, 35 ... Clamp part,
37: A / D converter, 38: output synthesizing unit, 41: reference density plate
45: image monitor unit, 46: memory.

Claims (2)

A light source for illuminating the original,
Reading means for photoelectrically reading the image of the document,
A reference density plate,
Light amount correction means for correcting the light amount of the light source based on reference read data obtained by reading the reference density plate with the reading means,
An image reading apparatus, comprising: a light quantity correction timing determining means for determining a light quantity correction timing by the light quantity correction means based on a lighting time of the light source. A light source for illuminating the original,
Reading means for photoelectrically reading the image of the document,
A reference density plate,
Light amount correction means for correcting the light amount of the light source based on reference read data obtained by reading the reference density plate with the reading means,
An image reading apparatus comprising: a light quantity correction timing determining unit that determines a light quantity correction timing by the light quantity correction unit based on the number of times of reading the document.

Images