JP4392947B2 - Image reading apparatus, control method of image reading apparatus, and storage medium - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image reading apparatus, a method for controlling the image reading apparatus, and a storage medium, and more particularly to an image reading apparatus for reading reflected light or transmitted light of a document placed on a document table.
[0002]
[Prior art]
Conventionally, an image scanner using a CCD linear image sensor (hereinafter referred to as a CCD) is known as an image reading device. FIGS. 6A and 6B simply show the configuration of an apparatus called a flatbed scanner. FIG. 6A is a top view and FIG. 6B is a side view.
[0003]
In FIG. 6, D is a read original placed on the platen glass 100, and the reflected light irradiated by the light source 101 is folded back by mirrors 102, 103, 104 and imaged on the CCD 106 by the lens 105. .
[0004]
The entire original D is scanned by scanning the reading unit 107 on which the light source 101, the mirrors 102, 103, 104, the lens 105, and the CCD 106 are fixedly placed in parallel to the original table glass 100 from the left to the right in FIG. Read and obtain an image signal for one page from the CCD 106. A CCD board 113 on which the CCD 106 is placed and a main board 112 fixed to the image reading apparatus are connected by a cable 111.
[0005]
As shown in FIG. 6A, the direction from top to bottom is the main scanning direction, and the direction from right to left is the sub-scanning direction. In order to avoid the influence from external light, the inside is shielded by the exterior cover 1 and the document holder 110.
[0006]
FIG. 7 shows an example of a circuit block constituting the output level adjusting means. Reflected light irradiated from the light source 101 capable of dimming control and applied to the document or an optical signal transmitted through the document is imaged on the CCD 106 via the lens 105.
[0007]
The optical signal imaged on the CCD 106 is subjected to signal processing by the analog gain adjustment circuit 31 and then digitized by the A / D converter 32. Then, it is sequentially supplied to the shedding correction circuit 3 and the image processing circuit 4.
[0008]
The output of the A / D converter 32 is given to the light peak detection circuit 5, and the peak output in the region designated by the CPU 36 in the light peak detection circuit 5 is detected and stored in 8 bits. A control signal from the CPU 36 is supplied to the output level control circuit 6 so that the control signal can control the output level through the output level control circuit 6.
[0009]
In FIG. 7, the dimming control means of the lamp 101 is described as the output level control means, but the accumulation time control of the CCD 106, the electronic shutter level control means, the analog gain adjustment circuit 31, and the A / D not shown. Various known means such as a gain adjusting means by ref control of the converter and a level control means such as a level adjusting means in the image processing circuit 4 can be used.
[0010]
However, in order to obtain an image with a better S / N, it is most effective to use light control as shown in FIG. By the way, when performing dimming control, the temperature characteristic of the lamp is an element that cannot be ignored. FIG. 8 shows the difference in relative illuminance change depending on the lamp temperature.
[0011]
The relative illuminance in this case is defined as 100% of the illuminance at the normal temperature (25 ° C.). Actually, the illuminance of the lamp used in the scanner is about 50 to 55% in FIG. 8 and reaches a required level even at low temperatures, but it takes about 50 seconds.
[0012]
At normal temperature (25 ° C.) and high temperature (35 ° C.), the level is reached in less than about 10 seconds. Also, looking at the graph after the output level is saturated, the output continues to decrease at low temperatures, making it difficult to stabilize. As at normal temperature and high temperature, when temperature rises, there is a characteristic that it is easy to stabilize quickly.
[0013]
In other words, since the time required to reach the required level and the stabilization time are long at low temperatures, the light control time is overwhelmingly longer than at normal temperatures and high temperatures.
[0014]
As an example of controlling the output level by an optical signal by dimming control, FIG. 9 shows a flowchart relating to dimming control. In FIG. 9, step S101 is an example in which processing is performed from when the image reading apparatus is turned on.
[0015]
Usually, the light source 101 includes a cold cathode lamp, a halogen lamp, and the like, and the dimming control is usually performed by PWM control in the output level control circuit 6 having voltage control, current control, intermittent lighting control, and the like.
[0016]
In step S101, the lamp PWM is 100% because the normal lamp is ON. In step S102, a wait time of 10 seconds is provided to wait for the light quantity of the light source 101 to be stably lit. However, this wait time is not constant because it depends on the performance of the lamp and the configuration of the image reading apparatus.
[0017]
In step S 103, the light output level Pn is detected by the light peak detection circuit 5 in order to measure the stability of the light source 101. Next, in step S104, dimming control is performed until the vicinity of the target target output level Pt is reached. Next, in step S105, it is determined whether or not the light output level Pn has reached the target output level Pt. As a result of this determination, when the light output level Pn has not reached the target output level Pt, it goes without saying that the PWM of the lamp maintains 100%.
[0018]
Next, detection of the light output level Pn is repeated every 0.75 seconds in step S106. When the light output level Pn reaches within ± 1% of the level target output level Pt, the control proceeds to stabilization control in step S107 and thereafter.
[0019]
In the stability check of step S108, if the fluctuation of the output level is maintained at a fluctuation of 1 level or less for a certain time (in this case, 1.5 seconds), it is determined that the output is stable and the dimming control is terminated. .
[0020]
FIG. 10 shows a change in the output level of the lamp at a low temperature (10 ° C.) and at a normal temperature (25 ° C.). At room temperature, after the wait time (T1) of 10 seconds of step S102, the output level has already reached the target output level Pt. Therefore, after the wait time of step S107 and the stability check (T2) of step S108 Then, the light control is finished.
[0021]
On the other hand, since the light output level Pn does not reach the target output level Pt in the wait time of 10 seconds at the low temperature, steps S104 to S106 are performed until the target output level Pt is reached (T3). Then, the stability check (T4) in subsequent steps S107 and S108 is performed. As described above, at low temperatures, it takes time for the lamp to stabilize compared to normal temperatures and high temperatures, so the stability check time T4 is long. Become.
[0022]
[Problems to be solved by the invention]
According to the flowchart of FIG. 9, when the ambient temperature is normal as shown in FIG. 10, the dimming control time (T1 + T2) is about 30 seconds, while the dimming control time (T3 + T4) is low. Is about 100 seconds, which is about 3 to 3 times as long as that at room temperature. In other words, there has been a problem that the total light control time is long.
[0023]
The present invention has been made in view of the above-described problems, and an object of the present invention is to shorten the time required to reach a necessary level and the time required for stabilization at a low temperature.
[0024]
[Means for Solving the Problems]
The image reading apparatus of the present invention includes a light source, an image sensor on which reflected light of an original illuminated by the light source is imaged, a detection unit that detects an output of the image sensor, and an output level of the detection unit. An image reading apparatus having a comparing means for comparing with a threshold value and a dimming means for dimming the light source so that an output of the detecting means becomes a target level, which is lower than the target level, and The first threshold value is set so that the output level of the detection means after the first time has elapsed from the start of lighting of the light source is above the normal temperature and below the low temperature, and the first threshold is set from the start of lighting of the light source. When the output level exceeds the first threshold value by the comparing means after a lapse of time, the light control means starts dimming of the light source, and the output level exceeds the first threshold value. When Le is below is characterized in that to start the dimming of the light source by the light control means after waiting until above a second threshold higher than the target level.
Another feature of the image reading apparatus according to the present invention is that the dimming means performs PWM control and maintains the PWM at 100% until the dimming starts.
According to another feature of the image reading apparatus of the present invention, after waiting until the second threshold value higher than the target level is exceeded, and further after the second time has elapsed, the light control means controls the light source. The dimming is started.
It is characterized by that.
[0025]
The control method of the image reading apparatus according to the present invention includes a light source, an image sensor on which reflected light of a document illuminated by the light source is imaged, a detection unit that detects an output of the image sensor, and an output of the detection unit. A method of controlling an image reading apparatus having a dimming unit for dimming the light source so that a level becomes a target level, and a lighting step for starting lighting of the light source,
A first time waiting step of waiting for the elapse of a first time after starting the lighting, and an output level of the detecting means lower than the target level and after the first time elapses from the start of lighting of the light source. In the first comparison, the first threshold value is set at a level lower than the upper temperature and lower, and the output level of the detection means is compared with the first threshold value after the first waiting time step. A second comparison step that waits until the output level of the detection means exceeds a second threshold value that is higher than the target level after the first comparison step, and a dimming operation that performs dimming by the dimming device. And when the output level exceeds the first threshold value in the first comparison step, the dimming step is started. In the first comparison step, the output level is set to the first level. When the value falls below the threshold, the second comparison step is performed. Characterized in that to start the dimming process later.
Another feature of the control method for an image reading apparatus according to the present invention is that it includes a second time waiting step for waiting for a second time, and the output level is set to the first level in the first comparison step. When the value falls below the threshold value, the dimming step is started after the second comparison step and after the second waiting time step.
[0026]
The storage medium of the present invention stores a program for causing a computer to execute each step of executing the control method for the image reading apparatus described above.
[0027]
[Action]
Since the present invention has the above technical means, when it is determined that the environmental temperature is low, the output level is raised to a level above the target level, so that the lamp enters the stabilization control. It is possible to shorten the time until the output is stabilized.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
FIG. 1 is a flowchart for explaining an image reading apparatus, a control method for the image reading apparatus, and a processing procedure of a storage medium according to the first embodiment of the present invention.
[0029]
Since the first step S201 is taken from the time when the image reading apparatus is turned on as an example, the explanation starts from the lamp ON in the sense that the lighting of the light source 101 is started. Examples of the normal light source 101 include a cold cathode lamp and a halogen lamp. Dimming control includes voltage control, current control, and intermittent lighting control.
[0030]
Further, the actual control is usually based on PWM control in the output level control circuit 6 shown in FIG. In step S201, since the lamp is normally ON, the lamp PWM is 100%.
In the next step S202, a wait time of 10 seconds is provided to wait for the light quantity of the light source 101 to be stably lit. However, this wait time depends on the performance of the light source 101 and the configuration of the image reading apparatus, and is not constant. Absent.
[0031]
In this embodiment, the threshold value Ps of the lamp output is set in advance to a level that exceeds the normal temperature and decreases below the low temperature after the first time T1 ′ (in this case, 10 seconds) in FIG. 3 has elapsed. In step S204, the bright peak output level Pn detected in step S203 after the elapse of time T1 ′ is compared with the threshold value Ps. Judgment is made.
[0032]
FIG. 2 shows a change in lamp tube wall temperature at the time of stabilization due to a change in lamp PWM. From FIG. 2, it can be seen that the lamp tube wall temperature at the time of stability and the PWM of the lamp have a substantially proportional relationship.
[0033]
From FIG. 8 described above, the higher the tube wall temperature of the lamp, the shorter the time for stabilization. Therefore, from FIGS. 2 and 8, in order to shorten the fourth time T4 ′, which is the lamp stabilization time, the lamp tube wall temperature is increased, that is, the lamp is stabilized in a high output state. It is important to plan.
[0034]
When the lamp output level is a low temperature state not reaching the threshold value Ps, a waiting time of a predetermined time is put in step S205 with the lamp PWM being 100%. The setting of this waiting time is the time required for stabilization rather than the increased amount of time, although the third time T3 ′ becomes longer by inserting this. By setting the fourth time T4 ′ to be shorter, as a result, the total time of the “third time T3 ′” and the “fourth time T4 ′” is set to be short.
[0035]
Then, after the light output level Pn reaches the target output level Pt, in order to wait for the light source 101 to stabilize, the stability check of the light output level Pn in steps S209 and S210 is performed for 1.5 seconds. In the meantime, the control is repeated until the change in the output level falls below “1”.
[0036]
FIG. 3 shows the time course of the output level of the lamp when this embodiment is used.
In the present embodiment, a fixed waiting time is set in the state of 100% PWM of the lamp so that the third time T3 ′ that is the dimming control time is longer than the conventional example. Then, when the light output level Pn reaches the threshold value Ps in step S204, the output level becomes higher than the target output level Pt as in the end of the third time T3 ′ in FIG.
[0037]
Then, in step S206, the level is suppressed by adjusting the PWM so that the target output level Pt ± 1% is obtained. At this time, the tube wall temperature of the lamp is already high. Since the temperature of the lamp tube wall is high in time, it becomes easy to stabilize, and the fourth time T4 ′, which is the stabilization time, can be made shorter than in the conventional example.
[0038]
The waiting time in step S205 is set so that the time for stabilization is shorter than the amount of time for the dimming control, that is, (T3′−T3) ≦ (T4−T4 ′). By setting, the total dimming control time can be shortened.
[0039]
The constant waiting time of step S205 to be entered in this embodiment varies depending on the characteristics of the lamp, etc. If the same lamp is used, the optimum lamp dimming control time can be set by simply changing the setting of this waiting time. It becomes possible to set.
[0040]
(Second Embodiment)
FIG. 4 shows a second embodiment of the present invention. In FIG. 4, since the first step S301 is taken from the time when the image reading apparatus is turned on as an example, the explanation starts from the lamp ON in the sense that the lighting of the light source 101 is started. The normal light source 101 includes a cold cathode lamp, a halogen lamp, and the like. Dimming control includes voltage control, current control, and intermittent lighting control. In the output level control circuit 6, the PWM control is usually used.
[0041]
In the first step S301, since the normal lamp is ON, the lamp PWM is 100%. In the next step S302, a wait time of 10 seconds is provided to wait for the light amount of the light source 101 to be stably lit, but this wait time is not constant because it depends on the performance of the lamp and the configuration of the image reading apparatus. .
[0042]
In this embodiment, the threshold value Ps of the lamp output is set in advance to a level that exceeds the normal temperature after the first time T1 ″ (in this case, 10 seconds) in FIG. The bright output level Pn detected in step S303 after the elapse of time T1 ″ and the threshold value Ps are compared in step S304, and when the bright output level Pn ≦ Ps, it is determined that the scanner body is in a low temperature environment. .
[0043]
If it is determined in step S304 that the environment is a low temperature environment, the light output level Pn is detected in step S306, and whether the light output level Pn has reached Pvt set higher than the target output level Pt in step S307. Determine whether or not. If the result of this determination is that it has not reached, after waiting for step S308, the processing of step S306 and step S307 is performed again.
[0044]
When the light output level Pn reaches Pvt, after the waiting time of 5 seconds in step S309, the dimming control in step S305 is performed. If the light output level Pn has reached the threshold value Ps in step S304, it is determined that the environment is at room temperature or higher, and step S305 is performed.
[0045]
Next, in step S310, step S305 is repeated until the light output level Pn reaches the target output level Pt. When the output level Pn reaches the target output level Pt, the process proceeds to the stabilization control in step S311 and step S312. If the fluctuation of the output level is suppressed to 1 level in the meantime, it is determined that the output has been stabilized, and all the light control is finished.
[0046]
FIG. 5 shows the time course of the output level of the lamp when this embodiment is used.
If it is determined in step S304 that the temperature is low, the light output level Pn is raised to a target Pvt higher than the target output level Pt with the lamp PWM maintained at 100%. The lamp tube wall temperature can be brought to a higher state than in the conventional example by always raising the target output level to a level higher than the target output level Pt.
[0047]
When the target Pvt is reached, a specific waiting time (in this case, 5 seconds) is inserted to further increase the temperature of the lamp tube wall, and to some extent cause variations in the lamp output level before entering the dimming control in step S305. Can be kept within the range.
[0048]
In step S310, the level is suppressed by adjusting the PWM so that the target output level Pt ± 1%. However, since the lamp tube wall temperature is already high at this time, the subsequent stabilization control is performed. In time, as shown in FIG. 8, it becomes easy to stabilize, and the stabilization time T4 ″ can be made shorter than the conventional stabilization time T4.
[0049]
The third time T3 ″ in the present embodiment is longer than the above-described third time T3, but the stabilization time is shorter than the amount of increase in the third time T3 ″ in the present embodiment. Can be. That is, the total light control time can be shortened by setting the level Pvt in step S307 and the waiting time in step S309 so that (T3 ″ −T3) ≦ (T4−T4 ″). is there.
[0050]
FIG. 11 shows an example of a computer system constituting the image reading apparatus of the present invention.
FIG. 11 is a diagram illustrating a configuration of a control device of a general image reading device. In FIG. 11, reference numeral 1200 denotes a computer PC. The PC 1200 includes a CPU 1201 and executes network printing device control software stored in a ROM 1202 or a hard disk (HD) 1211 or supplied from a floppy disk drive (FD) 1212 and connected to the system bus 1204. To control.
[0051]
A RAM 1203 functions as a main memory, work area, and the like for the CPU 1201. A disk controller (DKC) 1207 is a hard disk (boot program (start program: a program that starts execution (operation) of personal computer hardware and software)), a plurality of applications, editing files, user files, a network management program, and the like. HD) 1211 and floppy disk (FD) 1212 are controlled.
[0052]
A network interface card (NIC) 1208 is used when the image reading apparatus according to the embodiment is connected to a network via the LAN 1220.
[0053]
The program stored in the CPU 1201, the ROM 1202 or the hard disk (HD) 1211 of the PC 1200 constitutes an environment determination unit, a light control unit, a level detection unit, a control unit, and the like in the image reading apparatus of the present embodiment.
[0054]
(Other embodiments of the present invention)
The present invention may be applied to a system composed of a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.) or an apparatus composed of a single device.
[0055]
In addition, for operating various devices so as to realize the functions of the above-described embodiments, for realizing the functions of the above-described embodiments for an apparatus or a computer in the system connected to the various devices. Implementations by supplying software program codes and operating the various devices in accordance with programs stored in a computer (CPU or MPU) of the system or apparatus are also included in the scope of the present invention.
[0056]
In this case, the program code itself of the software realizes the functions of the above-described embodiment, and the program code itself and means for supplying the program code to the computer, for example, the program code are stored. This storage medium constitutes the present invention. As a storage medium for storing the program code, for example, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.
[0057]
In addition, by executing the program code supplied by the computer, not only the functions described in the above embodiments are realized, but also the OS (Operating System) or other application in which the program code is running on the computer. It goes without saying that the program code is also included in the embodiment of the present invention even when the functions described in the above-described embodiment are realized in cooperation with software or the like.
[0058]
Further, after the supplied program code is stored in the memory provided in the function expansion board of the computer or the function expansion unit connected to the computer, the CPU provided in the function expansion board or function expansion unit based on the instruction of the program code The present invention also includes a case where the functions of the above-described embodiment are realized by performing part or all of the actual processing.
[0059]
【The invention's effect】
As described above, according to the present invention, the use environment can be determined with a simple configuration. In addition, regardless of the use environment, the time until the output is stabilized can be shortened, and the total scan time can be shortened.
[Brief description of the drawings]
FIG. 1 is a flowchart for explaining a first embodiment of the present invention;
FIG. 2 is a diagram illustrating a state of a change in lamp tube wall temperature at the time of stabilization due to a change in PWM of the lamp according to the embodiment.
FIG. 3 is a characteristic diagram showing a lapse of time of the output level of the lamp when the embodiment is used.
FIG. 4 is a flowchart for explaining a second embodiment of the present invention.
FIG. 5 is a characteristic diagram showing a lapse of time of the output level of the lamp in the second embodiment.
FIG. 6 is a top view illustrating a schematic configuration of the image reading apparatus.
FIG. 7 is a block diagram illustrating an example of a circuit that performs output level adjustment.
FIG. 8 is a characteristic diagram showing an example of a change over time after lighting.
FIG. 9 is a flowchart for explaining a procedure of dimming control.
FIG. 10 is an operation output characteristic diagram illustrating a change in the output level of the lamp at a low temperature (10 ° C.) and at a normal temperature (25 ° C.).
FIG. 11 is a block diagram illustrating an example of a computer system that constitutes a control device of the image reading apparatus according to the present exemplary embodiment.
[Explanation of symbols]
3 Shading correction circuit 4 Image processing circuit 5 Light peak detection circuit 6 Output level control circuit 31 Analog gain adjustment circuit 32 A / D converter 36 CPU
101 Light source 105 Lens 106 CCD

Claims (6)

A light source;
An image sensor on which reflected light of an original illuminated by the light source is imaged;
Detection means for detecting the output of the image sensor;
Comparing means for comparing the output level of the detecting means with a predetermined threshold;
An image reading device having dimming means for dimming the light source so that the output of the detecting means reaches a target level,
The first threshold value is set to a level lower than the target level, and the output level of the detection means after the first time has elapsed from the start of lighting of the light source is higher than normal and lower than low. after the lamp starts lighting by the comparing means after the lapse of the first time, the when the output level is above than the first threshold value, by the light control means starts the dimming of the light source, the first When the output level is lower than a threshold value, the image reading apparatus is configured to start dimming of the light source by the dimming unit after waiting until the second threshold value higher than the target level is exceeded. .   The image reading apparatus according to claim 1, wherein the dimming unit performs PWM control and maintains the PWM at 100% until the dimming starts.   2. The image according to claim 1, wherein dimming of the light source is started by the dimming unit after a second time has elapsed after waiting for a second threshold value higher than the target level to be exceeded. Reading device. A light source, an image sensor light reflected document illuminated by the light source is imaged, detection means for detecting an output of the image sensor, the light source so that the output level of the detecting means becomes a target level A method for controlling an image reading apparatus having a light control means for adjusting light,
A lighting process for starting lighting of the light source;
A first time waiting step of waiting for the passage of a first time after starting the lighting;
The first threshold value is set to a level lower than the target level, and the output level of the detection means after the first time has elapsed from the start of lighting of the light source is higher than normal and lower than low. after the first hour waiting step, a first comparison step for comparing the output level and the first threshold value of the detection means,
A second comparison step of waiting after the first comparison step until the output level of the detection means exceeds a second threshold value higher than the target level;
A dimming step of performing dimming with the dimming means,
The output level in the first comparison step starts the dimming step when exceeding the first threshold value, when said said output level in the first comparing step is lower than said first threshold said first A control method for an image reading apparatus, wherein the dimming step is started after two comparison steps. A second hour wait step of waiting a second time, the output level in the first comparing step has undergone the second time wait step after the second comparison step when below said first threshold value The method for controlling an image reading apparatus according to claim 4, wherein the dimming step is started later.   A computer-readable storage medium storing a program for causing a computer to execute each step according to claim 4.

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