JP3946171B2 - Method for controlling image reading apparatus - Google Patents

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 on 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 conventional devices described above, in the former, power is wasted along with auxiliary lighting of the cold cathode tube during standby, and the lifetime of the cold cathode tube is reduced, or cooling during standby is performed. 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 the actual temperature difference of the ambient temperature near the light source between the seasons and the usage environment when the cold cathode tube actually starts up. 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 a high level and can reliably improve an image read by an actual image reading operation.
[0011]
[Means for Solving the Problems]
To achieve the above object, an image reading apparatus control method according to the present invention includes an initial voltage higher than a voltage applied when an image reading operation is performed in the image reading apparatus control method including a cold cathode tube lamp as a light source. The cold cathode tube lamp is started up by applying the light, and the light quantity at the rising edge of the cold cathode tube lamp is sequentially detected by the optical sensor for image reading every reference time, and the light quantity at the reference time based on the detection result After the rate of change falls below the reference value, gain adjustment and white reference adjustment for A / D conversion of the image signal are performed, and then the initial voltage is switched to a voltage applied when performing the image reading operation. It is one that transition to a state capable of image reading operation, the reference time, the environmental temperature in the vicinity of the light source is set higher short, the reference value, the gain adjustment and the white reference Amount in starting an integer is adapted to be set so as to stabilize the amount of light near the time of performing the image reading operation.
[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 the initial voltage higher than the voltage applied during the image reading operation applied in the actual image reading operation is applied to the cold cathode tube, the rise time of the cold cathode tube is appropriate. Shortened to In addition, calibration such as gain adjustment and white reference adjustment is performed while the initial voltage is applied to the cold cathode tube, and thereafter, an image reading operation in which the applied voltage to the cold cathode tube is lower than the initial voltage is performed. Since it is switched to the voltage to be applied at the time of execution and the image reading operation is possible, in the image read in the subsequent actual image reading operation, the adjusted gain and the white reference are surely exceeded. As a result, a good image is obtained.
[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 light amount change rate per unit 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, first, in step # 5, the CPU 2 gives a lighting command to the driver 5, thereby applying an initial voltage V ₁ higher than the rated voltage V ₂ to the cold cathode tube 4 to light it. 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 reference time B for extraction elapses in step # 15 (step # 25), the cold cathode tube is detected by the CCD 3 in step # 30. A light quantity X _{n + 1} of 4 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. The light quantity change rate Y calculated from (1) 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]
If the light quantity change rate Y (= (X _{n + 1} −X _n ) / X _n ) is equal to or smaller than the reference value C in step # 35, it is temporarily determined that the cold cathode tube 4 has reached a stable light quantity. In step # 40, when the reference time B has elapsed, in step # 45, the light amount _{Xn + 2} of the cold cathode tube 4 is detected again by the CCD 3. Subsequently, at step # 50, the light amount change rate Y is calculated from the detected light amounts _{Xn + 1} and _{Xn + 2} at step # 30 and # 45 from the above equation (1), and this light amount change rate Y is used as a reference value. Compare again with C.
[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, the cold cathode tube 4 finally reaches a stable light quantity. Judge that it was done. Thereafter, in step # 55, the gain for A / D converting the image signal to the CCD 3 based on the light quantity X _{n + 2} of the cold cathode tube 4 while applying the initial voltage V ₁ to the cold cathode tube 4. Calibration such as adjustment and 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 and X _{n + 1} is replaced with X _n . If the light quantity change rate Y (= (X _{n + 2} −X _{n + 1} ) / X _{n + 1} ) is not less than the reference value C in step # 50, the process proceeds to step # 95 and X _{n + 2} is set. Both are replaced with _Xn , and both return to step # 25 to repeat the same operation as described above. 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 . Is switched to the lower rated voltage V ₂ and shifts to the reading operation Ready, so that in the image read in the subsequent actual image reading operation, the adjusted gain and the white reference are not reliably exceeded. 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. The operation is shifted to Ready (application of the rated voltage V ₂ ). It should be noted that the light quantity is once 0 (zero) immediately before the read operation Ready, but this is because the voltage application to the cold cathode tube 4 is temporarily stopped and the voltage is switched from the initial voltage V ₁ to the rated voltage V ₂ . It represents what has been done.
[0028]
In addition, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present 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 including the cold cathode tube lamp as the light source, the initial voltage higher than the voltage applied when performing the image reading operation. The cold cathode tube lamp is started up by applying the light, and the light quantity at the rising edge of the cold cathode tube lamp is sequentially detected by an optical sensor for image reading every reference time, and the light quantity at each reference time based on the detection result After the rate of change falls below the reference value, gain adjustment and white reference adjustment for A / D conversion of the image signal are performed, and then the initial voltage is switched to a voltage applied when performing the image reading operation. It is one that transition to a state capable of image reading operation, the reference time, the environmental temperature in the vicinity of the light source is set shorter the higher the reference value, the gain adjustment and the white reference adjustment Amount at the time of start, the so has manner is set to be near the stable light quantity when the image reading operation, when the rise of the cold cathode tube, a reference time corresponding to the environmental temperature around the light source The rate of change in the amount of light is compared and determined every time, so that the fact that the cold-cathode tube has reached a stable amount of light can be determined quickly and accurately according to the ambient temperature. At the same time, since the initial voltage higher than the voltage applied when performing the image reading operation applied in the actual image reading operation is applied to the cold cathode tube, the rise time of the cold cathode tube is appropriate. Shortened to Moreover, calibration such as gain adjustment and white reference adjustment is performed while the initial voltage is still applied to the cold cathode tube, and thereafter, an image reading operation in which the applied voltage to the cold cathode tube is lower than the initial voltage is performed. Since it is switched to the voltage to be applied at the time of execution and the image reading operation is possible, in the image read in the subsequent actual image reading operation, the adjusted gain or white reference is surely exceeded. As a result, a good image is obtained.
[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 test results obtained by the control method of the present invention, and is a table summarizing the light quantity change rates of the cold cathode tubes 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 the amount of light of a cold cathode tube.
FIG. 6 is a graph showing light quantity characteristics 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 provided with a cold cathode tube lamp as a light source,
The cold cathode tube lamp is started up by applying an initial voltage higher than the voltage applied when performing the image reading operation, and the light quantity of the rising of the cold cathode tube lamp is sequentially read at every reference time. After the light amount change rate for each reference time based on the detection result becomes equal to or less than the reference value, gain adjustment and white reference adjustment for A / D conversion of the image signal are performed, and then the initial voltage Is switched to a voltage to be applied when performing the image reading operation to shift to a state in which the image reading operation is possible,
The reference time is set shorter as the environmental temperature near the light source is higher ,
The control method for an image reading apparatus, wherein the reference value is set such that a light amount when starting the gain adjustment and white reference adjustment is close to a stable light amount when performing the image reading operation . 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. The method of controlling an image reading apparatus according to claim 1 , wherein the light quantity change rate per unit time is larger as the ambient temperature near the light source is higher.

Images