JP2005045309A - Control method of image scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control method of an image scanner provided with a cold cathode tube lamp as a light source capable of properly reducing a rising time of the cold cathode tube lamp and surely improving an image read in an actual image reading operation in response to ambient temperature around the light source. <P>SOLUTION: An initial voltage higher than the rated voltage is applied to the cold cathode tube lamp to raise the cold cathode tube lamp, a photosensor for image reading sequentially senses the luminous quantity in a rising state of the cold cathode tube lamp by each reference time, after a rate of a luminous quantity change by each reference time reaches a reference value or below on the basis of a result of the sensing, the gain and the white color reference are adjusted to apply analog / digital conversion to an image signal, and thereafter the initial voltage is switched into the rated voltage so that the image reading apparatus is brought into a state wherein the image reading apparatus can carry out image reading, and the reference time is set shorter as the ambient temperature around the light source is higher. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for controlling an image reading apparatus that reads an image of a document that is used alone as a scanner or mounted in a copying machine, a facsimile, or the like, and more particularly, an image reading apparatus that includes a cold cathode tube lamp as a light source. The present invention relates to an apparatus control method.
[0002]
[Prior art]
In general, in an image reading operation, an image reading device irradiates a document with light from a light source, guides the reflected light to a photosensor such as a CCD through a condensing lens while reflecting the reflected light by a plurality of mirrors. The document image is acquired (read) as an electrical signal (image signal).
[0003]
Here, as a light source of the image reading device, a xenon lamp has been generally used conventionally. However, the xenon lamp has an advantage that the rise until reaching a stable light quantity is remarkably fast, but has a short life, is expensive, and is unsuitable for downsizing. Therefore, in recent years, cold cathode tube lamps that have a longer life and are cheaper than xenon lamps and are excellent in miniaturization have come to be applied as light sources.
[0004]
However, this cold-cathode tube lamp (hereinafter sometimes simply referred to as “cold-cathode tube”) has a certain amount of time to rise until it reaches a stable light amount, as shown in FIGS. It has the characteristic of requiring This rise time is reflected in the waiting time before starting the actual image reading operation. Therefore, when using the cold cathode fluorescent lamp as a light source, it is required to make some contrivance in order to shorten the waiting time associated with the rising of the cold cathode fluorescent lamp as much as possible.
[0005]
As a conventional device for this, attention is paid to the dependence of the rise time on the temperature of the tube wall, which is one of the characteristics of the cold cathode tube, that is, the ambient temperature near the light source (the rise time becomes shorter as the ambient temperature becomes higher), The cold-cathode tube during standby is lit up and self-heated, or preheated by a special heating mechanism (for example, diverting the heat source of the fixing device in the mounted image forming apparatus) Thus, the temperature is constantly maintained at a high temperature (see, for example, Patent Document 1).
[0006]
As another contrivance, the rise time dependency on the applied voltage, which is a characteristic of the cold cathode tube, which is different from the above temperature dependency (the rise time becomes shorter as the applied voltage to the cold cathode tube is higher). At the time of start-up, a voltage higher than the voltage applied during the image reading operation is applied to the cold cathode tube (for example, see Patent Document 2). In this case, the rise time, that is, the high voltage application time, becomes longer as the elapsed time from the end of the immediately preceding image reading operation becomes longer in consideration of self-heating due to the lighting of the cold cathode tube in the immediately preceding image reading operation. Some are set to be.
[0007]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-99194 [Patent Document 2]
JP-A-1-267630
[Problems to be solved by the invention]
However, among the above-described conventional devices, the former consumes electric power along with auxiliary lighting of the cold cathode tube during standby, causes a decrease in the lifetime of the cold cathode tube, or cools down during standby. There is a problem that the structure of the image reading apparatus itself becomes complicated with the provision of a heating mechanism for preheating the cathode tube. Further, for an optical sensor for image reading, it is necessary to perform calibration such as gain adjustment and white reference adjustment for A / D conversion of an image signal based on the light quantity of the cold cathode tube. Since the voltage applied to the tube is constant between the rising edge and the image reading operation, if the calibration is not performed at an appropriate timing, the image read in the subsequent actual image reading operation will be white. In some cases, a so-called white spot in the image occurs.
[0009]
On the other hand, the latter does not cause power waste, cold cathode tube life reduction, or complicated structure like the former, but at the actual start-up of the cold cathode tube, the ambient temperature difference near the light source between the seasons and usage environment Is not considered, the rise time for applying the high voltage may be substantially inappropriate. This is because, as a characteristic of a cold cathode tube, its rise time varies depending on the environmental temperature.
[0010]
Accordingly, the present invention has been made in view of the above problems, and in an image reading apparatus provided with a cold cathode tube lamp as a light source, the rise time of the cold cathode tube lamp is appropriately set according to the environmental temperature in the vicinity of the light source. It is an object of the present invention to provide a control method that can be shortened to an excellent level and can reliably improve an image read by an actual image reading operation.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, an image reading apparatus control method according to the present invention is an image reading apparatus control method including a cold cathode tube lamp as a light source, wherein an initial voltage higher than a rated voltage is applied to the cold cathode tube. The lamp is started up, and the light quantity of the cold-cathode tube lamp rise is detected by the optical sensor for image reading sequentially every reference time, and the light quantity change rate per reference time based on the detection result becomes below the reference value. Thereafter, gain adjustment and white reference adjustment for A / D conversion of the image signal are performed, and then the initial voltage is switched to the rated voltage to shift to a state where an image reading operation is possible, The reference time is set shorter as the ambient temperature near the light source is higher.
[0012]
As a result, when the cold cathode tube rises, the change rate of the amount of light is compared and determined for each reference time corresponding to the ambient temperature in the vicinity of the light source, so that the cold cathode tube has reached a stable amount of light according to the ambient temperature. It can be accurately and quickly identified. At the same time, since an initial voltage higher than the rated voltage applied in the actual image reading operation is applied to the cold cathode tube, the rise time of the cold cathode tube is appropriately shortened. Moreover, calibration such as gain adjustment and white reference adjustment is performed with the initial voltage applied to the cold cathode tube, and then the applied voltage to the cold cathode tube is switched to a rated voltage lower than the initial voltage. Therefore, in the image read by the subsequent actual image reading operation, the adjusted gain and the white reference are not reliably exceeded, and as a result, a good image is obtained. It becomes.
[0013]
Here, it is determined with high certainty that the cold cathode tube has reached a stable light amount, and from the viewpoint of performing calibration on it, when the light amount change rate is continuously below the reference value a plurality of times, It is preferable to perform the gain adjustment and the white reference adjustment.
[0014]
Also, from the temperature dependence of the cold cathode tube, as the environmental temperature increases, the rise time of the cold cathode tube is shortened, that is, the rate of change in light quantity per unit time at the time when the stable light quantity is reached, Based on this, it is preferable that the value obtained by dividing the reference value by the reference time is larger as the ambient temperature near the light source is higher.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a method for controlling an image reading apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of an image reading apparatus according to the present invention, FIG. 2 is a flowchart showing the operation of the image reading apparatus in the control method of the present invention, and FIG. 3 is an example of a data table used in the control method. is there.
[0016]
An image reading apparatus 1 according to the present embodiment is mounted on a copying machine that is an image forming apparatus. As shown in FIG. 1, a CPU 2 that generally controls the entire apparatus, and an optical sensor for image reading. CCD 3, cold cathode tube lamp 4, driver 5 for driving the cold cathode tube 4, temperature sensor 6 for detecting the ambient temperature in the vicinity of the cold cathode tube lamp 4, and program formulas and data tables to be described later are stored. And a memory 7 to be configured. Further, the image signal of the original image read by the CCD 3 by the image reading operation of the image reading device 1 is sent to the image forming unit 8, and the image forming unit 8 forms the image on a sheet or the like.
[0017]
Next, the operation when the cold cathode tube rises in such an image reading apparatus will be described with reference to FIGS. As shown in FIG. 2, CPU 2, first in step # 5, it gives lighting command to the driver 5, thereby turning on by applying a high initial voltages V ₁ than the rated voltage V ₂ to the cold cathode tube 4. At the same time, the ambient temperature A in the vicinity of the cathode tube lamp 4 is detected by the temperature sensor 6 (step # 10), and the reference time B and the reference time B and the memory 7 are detected based on the ambient temperature A as a detection result from the temperature sensor 6. A reference value C is extracted (step # 15).
[0018]
Here, in the memory 7, as shown in FIG. 3, a reference time B and a reference value C corresponding to the environmental temperature A are preset and stored. The reference time B corresponds to a light amount detection pitch in the CCD 3 to be described later, and the reference value C serves as an index for comparison judgment of the light amount change rate calculated from the light amount detected by the CCD 3.
[0019]
In the present embodiment, the temperature is divided into three according to the environmental temperature A. When the environmental temperature A is low, A <15 ° C., the reference time B is 1.5 seconds and the reference value C is 1.2%. In the middle section of 15 ° C. ≦ A <20 ° C., B is 1 second in 2 seconds and C is 2%, and in the high ambient temperature section of 20 ° C. ≦ A, B is 0.2 seconds and C is 1%. ing. The reason why the reference time B is shorter as the environmental temperature A is higher is that the rise time of the cold cathode tube 4 is shorter as the environmental temperature A is higher than the temperature dependence of the cold cathode tube 4. That is, in order to accurately and quickly determine that the cold-cathode tube 4 has reached a stable light amount while taking into consideration that the light amount change rate per unit time becomes large, and when the ambient temperature A is low, the reference time B This is because the amount of change in light quantity sufficient for comparison and judgment is secured by increasing the length of time, and when the ambient temperature A is high, the amount of change in light quantity is sufficiently secured even if the reference time B is shortened. is there. Further, in particular, since the rate of change in light quantity per unit time when the stable light quantity is reached increases as the environmental temperature A increases, a value C / that is obtained by dividing the reference value C in each section by each reference time B B increases as the environmental temperature A increases (see the right column in FIG. 3).
[0020]
Returning to FIG. 2, the description of the operation will be continued. Subsequently, in step # 20, the light amount _Xn of the cold cathode tube 4 is detected by the CCD 3, and when the extraction reference time B has elapsed in step # 15 (step # 25), the cold cathode tube is detected by the CCD 3 in step # 30. 4 light quantity _{Xn + 1} is detected. Subsequently, in step # 35, the light quantity change rate Y for each reference time B from the detected light quantities _Xn and _{Xn + 1} in steps # 20 and # 30 is a program expression stored in advance in the memory 7 (1 The light quantity change rate Y is compared with the extraction reference value C in step # 15.
Y = (X _{N + 1} −X _N ) / X _N (1)
However, N = 1, 2,..., N, n + 1,.
[0021]
In step # 35, if the light quantity change rate Y (= ( _{Xn + 1− Xn} ) / _Xn ) is equal to or less than the reference value C, it is temporarily determined that the cold cathode tube 4 has reached a stable light quantity, When the reference time B elapses in step # 40, the light quantity _{Xn + 2} of the cold cathode tube 4 is detected again by the CCD 3 in step # 45. Subsequently, at step # 50, the light quantity change rate Y is calculated from the detected light quantities _{Xn + 1} and _{Xn + 2} at step # 30 and # 45 from the above equation (1), and this light quantity change rate Y is compared with the reference value C again. To do.
[0022]
If the light quantity change rate Y (= (X _{n + 2} −X _{n + 1} ) / X _{n + 1} ) is equal to or smaller than the reference value C in step # 50, it is definitely determined that the cold cathode tube 4 has reached a stable light quantity. Then, at step # 55, while applying the initial voltages V ₁ to the cold cathode tube 4, CCD 3 with respect to, based on the amount X _{n + 2} of the cold cathode tube 4, the gain adjustment and for A / D conversion of image signals Calibration such as white reference adjustment is performed. Then, at step # 60, switching the voltage applied to the cold cathode tube 4 to the rated voltage V ₂ is lower than the initial voltage V _1, the process proceeds to the image reading can state that reading operation Ready for operation (step # 65) .
[0023]
On the other hand, if the light quantity change rate Y (= (X _{n + 1} −X _n ) / X _n ) is not less than or equal to the reference value C in step # 35, the process proceeds to step # 90, where X _{n + 1} is replaced with X _n , and step # 50, if the light quantity change rate Y (= (X _{n + 2} −X _{n + 1} ) / X _{n + 1} ) is not less than or equal to the reference value C, the process proceeds to step # 95 where X _{n + 2} is replaced with X _n and both return to step # 25. The same operation as above is repeated. This is because in these cases, the cold cathode fluorescent lamp 4 does not reach a stable light quantity.
[0024]
Thus, when the cold cathode tube 4 rises, the light quantity change rate Y is compared and determined for each reference time B corresponding to the ambient temperature A in the vicinity of the light source, so that the cold cathode tube 4 has reached a stable light amount. This can be determined quickly and accurately according to the environmental temperature A. At the same time, since the initial voltage V ₁ higher than the rated voltage V ₂ applied in the actual image reading operation is applied to the cold cathode tube 4, the rise time of the cold cathode tube 4 is appropriately shortened. Is done. In addition, calibration such as gain adjustment and white reference adjustment is performed while the initial voltage V ₁ is still applied to the cold cathode tube 4, and thereafter, the applied voltage to the cold cathode tube 4 is changed from the initial voltage V ₁ . also switched to a low rated voltage V _2, the reading order is shifted to the operation Ready, in the subsequent actual image read image read by the operation, will not exceed reliably adjusted gain and white reference, the The result is a good image with no white spots.
[0025]
Further, in the present embodiment, when the light quantity change rate Y of the cold cathode tube 4 becomes the reference value C or less twice consecutively, it is definitely determined that the cold cathode tube 4 has reached the stable light quantity. However, this is for the case where noise is generated in the output relating to the light quantity from the CCD 3, and with higher certainty that the cold cathode tube 4 has reached a stable light quantity. This is to determine. Accordingly, the larger the number of times, the better. However, from the viewpoint of shortening the determination time, it is desirable that the number of times is two times or at most about three times as in the above embodiment.
[0026]
Finally, an example of the test result by the above operation is shown in FIGS. FIG. 4 is a table summarizing the light quantity change rate of the cold cathode tube every predetermined time as an example, and FIG. 5 is a diagram showing the relationship between time and the light quantity of the cold cathode tube. Here, the case where the environmental temperature A is 22.6 ° C. is shown, the reference time B is 0.2 seconds, and the reference value C is 1% (see FIG. 3). Further, the light quantity (CCD output value) starts to be detected by the CCD 3 after 8 seconds from the start of lighting of the cold cathode tube 4 (application of the initial voltage V ₁ ), and the light quantity change rate Y is compared and judged every reference time B. Yes. However, in this test, when the light quantity change rate Y of the cold cathode tube 4 becomes the reference value C or less for three consecutive times, the arrival of the stable light amount of the cold cathode tube 4 is determined.
[0027]
Then, after 12.2 seconds from the start of lighting, it is definitely determined that the cold cathode tube 4 has reached a stable light quantity, calibration is performed, and then reading is performed at about 14.5 seconds from the start of lighting. It has been migrated to the operation Ready (application of rated voltage _{V 2).} Incidentally, reading while operations Ready light amount immediately before is once becomes 0 (zero), which is stopped once the voltage applied to the cold cathode tube 4, the switching voltage that is from the initial voltages V ₁ to the rated voltage V ₂ It represents what has been done.
[0028]
In addition, this invention is not limited to said embodiment, A various change is possible in the range which does not deviate from the meaning of this invention.
[0029]
【The invention's effect】
As described above, according to the control method of the image reading apparatus of the present invention, in the control method of the image reading apparatus having the cold cathode tube lamp as the light source, the cold cathode tube is applied by applying an initial voltage higher than the rated voltage. The lamp is started up, and the light quantity of the cold-cathode tube lamp rise is detected by the optical sensor for image reading sequentially every reference time, and the light quantity change rate per reference time based on the detection result becomes below the reference value. Thereafter, gain adjustment and white reference adjustment for A / D conversion of the image signal are performed, and then the initial voltage is switched to the rated voltage to shift to a state where an image reading operation is possible, The reference time is set to be shorter as the ambient temperature near the light source is higher, so when the cold-cathode tube starts up, the amount of light is emitted at each reference time corresponding to the ambient temperature near the light source. Rate is compared judged, thereby, that the cold cathode tube has reached a stable quantity of light can determine accurately promptly in accordance with the environmental temperature. At the same time, since an initial voltage higher than the rated voltage applied in the actual image reading operation is applied to the cold cathode tube, the rise time of the cold cathode tube is appropriately shortened. Moreover, calibration such as gain adjustment and white reference adjustment is performed with the initial voltage applied to the cold cathode tube, and then the applied voltage to the cold cathode tube is switched to a rated voltage lower than the initial voltage. Therefore, in the image read by the subsequent actual image reading operation, the adjusted gain and the white reference are not reliably exceeded, and as a result, a good image is obtained. It becomes.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of an image reading apparatus according to the present invention.
FIG. 2 is a flowchart showing the operation of the image reading apparatus in the control method of the present invention.
FIG. 3 is an example of a data table used in the control method of the present invention.
FIG. 4 is an example of a test result according to the control method of the present invention, and is a table summarizing a change rate of light quantity of a cold cathode tube every predetermined time.
FIG. 5 is an example of a test result obtained by the control method of the present invention, and is a diagram showing a relationship between time and light quantity of a cold cathode tube.
FIG. 6 is a diagram showing a light quantity characteristic related to temperature dependence of a cold cathode tube lamp.
FIG. 7 is a diagram showing light quantity characteristics related to applied voltage dependence of a cold cathode tube lamp.
[Explanation of symbols]
1 Image reader 2 CPU
3 CCD (light sensor)
4 Cold cathode tube lamp 5 Driver 6 Temperature sensor 7 Memory

Claims (3)

In a control method of an image reading apparatus including a cold cathode tube lamp as a light source, an initial voltage higher than a rated voltage is applied to start up the cold cathode tube lamp, and the amount of light rising from the cold cathode tube lamp is set to a reference time. Detecting with an optical sensor for image reading every time, and after adjusting the light quantity change rate for each reference time based on the detection result below a reference value, gain adjustment and white reference for A / D conversion of the image signal After that, the initial voltage is switched to the rated voltage to shift to a state where an image reading operation is possible, and the reference time is set to be shorter as the environmental temperature near the light source is higher. A control method for an image reading apparatus. The method of controlling an image reading apparatus according to claim 1, wherein the gain adjustment and the white reference adjustment are performed when the light quantity change rate is continuously equal to or less than the reference value a plurality of times. 3. The method according to claim 1, wherein a value obtained by dividing the reference value by the reference time is larger as the ambient temperature near the light source is higher.

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