JP2002101278A - Original reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve handleability by reducing waiting time before starting actual reading of an original and thereby improving the read speed. SOLUTION: A CPU 11 executes reading of an original D if necessary after a lapse time from the lighting start becomes a time t1 or more required that a lighting amount of an exposure lamp 3 reaches the necessary minimum amount of a CCD sensor 6 after lightning of the lamp 3 is started. In a transient area of light emitting of the lamp 3, the CPU 11 makes a signal processor 7 obtain correction data for shading correction at each period of time required for raising the light emitting amount by a predetermined level, after the time t1 has passed since the lamp 3 is lit, and executes the shading correction based on the correction data by the processor 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an original reading apparatus for exposing an original with a cold-cathode tube type exposure lamp, reading the original, and performing shading correction.

[0002]

2. Description of the Related Art The light emission amount of a cold-cathode tube type exposure lamp gradually increases when driving is started, and reaches a certain stable light emission amount.

For this reason, in the conventional document reading apparatus, the reading of the document is started after the light emission amount of the exposure lamp is stabilized at a stable light emission amount.

[0004] Even if reading is performed only in a stable state as described above, the amount of stable light emission changes over time, so shading correction is performed to compensate for the effect.

In shading correction, data obtained when a reference surface forming a reference color (white or black) is read is stored as correction data, and image data obtained by actually reading a document is stored as described above. Correction is performed based on certain correction data. Conventionally, the acquisition of correction data is performed immediately before reading one document every time one document is read.

[0006]

By the way, in the cold-cathode tube type exposure lamp, it takes a long time, for example, 270 seconds, for the light emission amount to rise to a stable light emission amount after the driving is started. For this reason, immediately after the power is turned on, the waiting time until the reading of the document can be started becomes long, and the usability is reduced.

In addition, since it takes a little time to obtain a correction value for shading correction, the waiting time until the start of reading one document is also long.

The present invention has been made in view of such circumstances, and has as its object to reduce the waiting time before starting the actual reading of an original, thereby improving the reading speed. An object of the present invention is to provide a manuscript reading device that is easy to use.

[0009]

To achieve the above object, a first aspect of the present invention is to provide a method for controlling the amount of light emitted from the exposure lamp when the exposure lamp is turned on when the exposure lamp is off. A reading permission means implemented by software processing of a CPU, for example, which permits reading of a document from a predetermined timing exceeding a minimum light amount required by an image sensor such as a CCD sensor. During the period from the minimum light amount to the stable light emission amount in the stable light emission state, the correction data is obtained at a predetermined timing when the light emission amount of the exposure lamp exceeds the minimum light amount, and thereafter, at least the exposure The correction data is obtained at each predetermined timing at which the light emission amount of the lamp increases by a fixed amount, for example, by software of a CPU. And a correction data acquisition control means implemented by E A treatment.

[0010] By taking such measures, it is permitted to read the original in the transition area of the exposure lamp. When reading a document in the transition region of the light emission of the exposure lamp, the light emission amount of the exposure lamp exceeds the minimum light amount at a predetermined timing, and thereafter, the light emission amount of the exposure lamp increases by a fixed amount at a predetermined timing. In each case, at least correction data is obtained, and shading correction based on the correction data is performed. Therefore, the reading of the document can be started before the exposure lamp reaches the stable light emission state, and the change in the light emission amount of the exposure lamp is compensated by the shading correction, and the sufficient reading quality is secured.

According to a second aspect of the present invention, the correction data acquisition control means according to the first aspect of the present invention, wherein the light emission amount of the exposure lamp is set at a predetermined timing after the light emission amount of the exposure lamp exceeds the minimum light amount. The acquisition of the correction data is performed only at predetermined timings that increase by a fixed amount.

By taking such means, the acquisition of correction data in the transition region of the exposure lamp is performed at a predetermined timing determined based on the amount of change in the amount of light emitted from the exposure lamp, regardless of the state of execution of document reading. It is performed every time. Therefore, by appropriately setting the amount of change in the light emission amount of the exposure lamp between the timings at which the correction data is obtained, the execution frequency of the correction data in the transient region of the exposure lamp is minimized within a range that does not affect the read image quality. Can be kept to a minimum.

According to a third aspect of the present invention, when the exposure lamp is in a stable light-emitting state, at least a plurality of the light-emitting elements in the stable light-emitting state within a time required for a predetermined amount of change with time to occur. A correction data acquisition control means for acquiring the correction data at a predetermined timing every time when the original can be read, for example, realized by software processing of a CPU.

By taking such means, the acquisition of the correction data in the stable light emission state of the exposure lamp can be performed based on the change in the light emission amount of the exposure lamp, regardless of the execution state of the original reading. This is performed at each timing. Accordingly, by appropriately setting the timing interval for acquiring the correction data, the frequency of executing the acquisition of the correction data in the stable light emission state of the exposure lamp can be minimized within a range that does not affect the read image quality.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a main configuration of a document reading apparatus according to this embodiment.

As shown in FIG. 1, the document reading apparatus according to this embodiment includes a document table 1, a shading correction plate 2, an exposure lamp 3, mirrors 4, 5, a CCD sensor 6, a signal processing unit 7,
Lighting circuit 8, carriage driving mechanism 9, timer 10 CPU
11, a ROM 12, and a RAM 13. Then, a CCD sensor 6, a signal processing unit 7, a lighting circuit 8, a carriage driving mechanism 9, a timer 10, a CPU 11, a ROM 1
2 and the RAM 13 are connected to each other via a bus 14. Further, the CCD 6 and the signal processing unit 7 are directly connected without passing through the bus 14.

The document table 1 is a transparent plate made of glass or the like, and a platen document D is placed on its upper surface. A shading correction plate 2 whose lower surface is entirely white is attached to the lower surface of the original table 1 outside the area where the original D is placed.

The exposure lamp 3 is of a cold-cathode tube type, and exposes the reading surface (lower surface in the figure) of the original D which faces the original table 1 therebetween.

The mirror 4 reflects an optical image coming from the direction of the document table 1 toward the mirror 5.

The exposure lamp 3 and the mirror 4 are fixed to the same carriage (not shown), and move along the document table 1 with the two states shown by broken lines in the figure as being located at both ends. It is possible.

The mirror 5 is fixed at the position shown in the figure, and reflects the light image reflected by the mirror 4 further toward the CCD sensor 6.

The CCD sensor 6 scans a CCD image along an optical image arriving from the mirror 5, that is, along an optical path indicated by a chain line
It receives the light image guided to the sensor 6 and generates corresponding image data. Then, the CCD sensor 6 gives the generated image data to the signal processing unit 7.

The signal processing section 7 performs various known signal processing including shading correction on the image data supplied from the CCD sensor 6.

The lighting circuit 8 controls the application of a driving voltage to light the exposure lamp 3.

The carriage driving mechanism 9 includes, for example, a motor and a gear mechanism, and reciprocates a carriage on which the exposure lamp 3 and the mirror 4 are mounted.

The timer 10 measures the elapsed time since the reset by the CPU 11.

The CPU 11 controls the components of the original reading apparatus according to the control program stored in the ROM 12 to realize the operation of the original reading apparatus.

The ROM 12 stores a control program for the CPU 11, various setting data, and the like.

The RAM 13 stores various information necessary for the CPU 11 to perform various processes.

By the way, as the processing means realized by the CPU 11 by software processing based on the control program stored in the ROM 12, in addition to the well-known general processing means in the document reading apparatus, read permission means and correction data acquisition control means are provided. Have.

The reading permission means permits or prohibits the reading of the original. After the power of the exposure lamp 3 is turned on when the power is turned on, the light emission amount of the exposure lamp 3 is set to the CCD.
The execution of document reading is permitted only after a predetermined timing exceeding the minimum light amount required by the sensor 6.

The correction data acquisition control means controls the signal processing section 7 so as to acquire the correction data at an optimum timing according to the light emission state of the exposure lamp 3.

Next, the operation of the document reading apparatus configured as described above will be described.

The operation of generating image data according to the image of the original D by the CCD sensor 6 and performing signal processing on the image data generated by the CCD sensor 6 in the signal processing section 7 is the same as the conventional document reading operation. Since the configuration is the same as that of the apparatus, the description is omitted, and the operation after power-on and the subsequent control operation of acquiring correction data for shading correction will be described.

When the power is turned on, the CPU 11 returns to FIG.
The control process shown in FIG.

That is, the CPU 11 first instructs the lighting circuit 8 to start lighting the exposure lamp 3 (step S).
T1). At the same time, the CPU 11
Is reset (step ST2). As a result, the timer 10 measures the elapsed time from the time when the lighting of the exposure lamp 3 is started. Further, the CPU 11 sets the variable x
Is set to "1" (step ST3).

Thereafter, the CPU 11 sets the timer 10
(Hereinafter referred to as a timer value) is a predetermined value t1
It waits for the above (step ST4). That is, the CPU 11 waits until the time t1 elapses from the time when the lighting of the exposure lamp 3 is started. During this period CP
U11 does not perform processing for reading a document, and the document reading apparatus is in a document reading prohibited state.

When the timer value becomes equal to or more than the predetermined value t1, the CPU 11 checks whether the variable x is "6" (step ST5). Here, the variable x is “1”, not “6”. Therefore, in such a case, the CPU 11 updates the variable x to a value obtained by adding +1 to the previous value (step ST6). Subsequently, the CPU 11 causes the signal processing unit 7 to take in the correction data according to a well-known procedure (step ST7).

In this state, the CPU 11 waits for the timer value to be equal to or more than the predetermined value tx (here, t2) or for the need to read the document D (steps ST8 and ST9).

If it becomes necessary to read the document D, the CPU 11 performs a control process for reading one document by a well-known procedure (step ST10). Then, when reading of one document is completed, the CPU 11 returns to the standby state of step ST8 and step ST9. As described above, after the time t1 has elapsed since the start of the lighting of the exposure lamp 3, the reading of the document D is executed when it becomes necessary to read the document D. When the time t1 has elapsed from the start, the original reading apparatus is set in the original reading enabled state.

Now, steps ST8 and ST
If the timer value becomes equal to or more than the predetermined value tx in the standby state of No. 9, the CPU 11 repeats the processing from step ST5.

As a result, until the timer value becomes equal to or more than the predetermined value t6, the comparison value tx with the timer value is increased in step ST6.
Are sequentially changed to t3, t4, t5, and t6, and correction data is fetched in step ST7 every time the timer value reaches the comparison value tx or more at that time. During this time, if the reading of the document D is required, the reading of the document D is executed. Note that the most recently obtained correction data is used for the shading correction in the signal processing unit 7 when reading the document D.

In this way, t1 to t2, t2 to t3, t2 to t3, from the time when the exposure lamp 3 is started to be turned on to the time t6 after the time exceeds the predetermined time t1.
In each period of t3 to t4, t4 to t5, and t5 to t6, each time point of t1, t2, t3, t4, and t5 (however,
If the document is being read at each time, the correction data acquired at the time immediately after the document reading) is used.

The predetermined times t1 to t6 are set, for example, as follows.

FIG. 3 shows a state in which the exposure lamp 3 exposes the shading correction plate 2 and the carriage is fixed at a position where the mirror 4 reflects the reflected light image from the shading correction plate 2 to the mirror 5. FIG. 6 is a diagram showing a change in output voltage of the CCD sensor 6 when light emission of the CCD sensor is started. Under this condition, the output of the CCD sensor 6 is almost proportional to the light emission amount of the exposure lamp 3, and the curve in FIG.

The output light quantity rising characteristic of the exposure lamp 3 is of an integral type as shown in FIG. 3, and the curve is a log curve.

It is assumed that the illuminance when the exposure lamp 3 is in a stable light emission state is 70 klx, and the output voltage of the CCD sensor 6 at this time is 750 mV. The allowable range of the maximum output voltage of the CCD sensor 6 (the output voltage at the time of reading the white surface) for obtaining the required reading quality is 750 mV ± 5.
It is assumed that it is 0 mV. That is, the required minimum value of the maximum output voltage of the CCD sensor 6 is 700 mV.

In this embodiment, when the light emission amount of the exposure lamp 3 increases to such an extent that the maximum output voltage of 700 mV can be obtained, the document reading is permitted.

Under such conditions, the change amount Vo of the maximum output voltage of the CCD sensor 6 after the document reading permission state is reached and the exposure lamp 3 reaches the stable light emission state is as follows: Vo = 750 mV-700 mV = 50 mV Becomes

If the reading quality is affected by a change in illuminance of 1000 lx, the above-described illuminance of 70 kl
From the relation x = 750 mV, when the maximum output voltage of the CCD sensor 6 changes by about 10 mV, the reading quality is affected.

Therefore, if the correction data is fetched every time the maximum output voltage of the CCD sensor 6 changes by 10 mV, it is possible to prevent the shading correction from affecting the reading quality.

Therefore, the above-mentioned transition region of 50 mV is set to 10 m
Divided by V, 10mV, 20mV, 30mV, 40
mV and 50 mV are defined as parameters V, respectively.

Now, from the definition of the electrical transient, C · R
Vt = VL (1−ε− ^{t / T} ) in the transition region in the following equation: Vt / VL = 1−ε− ^{t / T} Vt / VL + ε− ^{t / T} = 1ε− ^{t / T} = 1−Vt / VL Ln (1−Vt / VL) = − t / T t = −ln (1−Vt / VL) T, and further expressed as T = t / −ln (1−Vt / VL) be able to.

Here, t is the time required for the exposure lamp 3 to reach a stable light emitting state after the start of lighting, and is 3 minutes (270 seconds) here. Assuming that V approaches 5 with the light intensity increased by 5% (0.05), Vt = 0.0
5. When Vo is 100% of the target value and VL = 1, T = 270 / -ln (1-0.05 / 1). When T is obtained by the above equation and the equation is obtained to obtain t when V is used as a parameter in the transient region, t = −ln (1-V / 50) × T. In this equation, parameters V, 10, 20, 3
When t is obtained by substituting 0, 40, and 50, t = 140.8 when V = 10, t = 152.4 when V = 20, t = 167.4 when V = 30, and t = 167.4 when V = 40 t = 188.5 When V = 50, t = 224.5.

Therefore, t1 = 140.8 seconds t2 = 152.4 seconds t3 = 167.4 seconds t4 = 188.5 seconds t5 = 224.5 seconds, and t6 = 270 seconds.

That is, in the characteristics shown in FIG.
When the output voltage is 0.70 V, 0.71 V, 0.72 V, 0.
T1 to t6 are set to the required time from the start of lighting until reaching 73V, 0.74V, and 0.75V, respectively.

Therefore, by the processing by the CPU 11 as described above, the CCD output voltage becomes 0.70 V, 0.71 V,
The correction data is obtained at each timing when the voltages reach 0.72 V, 0.73 V, and 0.74 V, respectively.

If t6 = 270 seconds have elapsed since the start of the lighting of the exposure lamp 3, and the exposure lamp 3 enters a stable light emitting state, the CPU 11 determines that the timer value has become equal to or greater than the predetermined value t6. Confirmation is made in steps ST8 and ST5 in FIG. And in this case, the CPU 11
Causes the signal processing unit 7 to take in the correction data according to a well-known procedure (step ST11). At the same time, the CPU 11 resets the timer 10 (Step S
T12). As a result, the timer 10 counts the elapsed time from the latest timing when the correction data is taken in thereafter.

In this state, the CPU 11 waits for the timer value to become equal to or more than the predetermined value t7 or for the need to read the document D (step ST13).
And step ST14). Note that the predetermined value t7 is a time within which the temporal change in the stable light emission amount does not affect the reading quality, and is set so that a plurality of originals can be read. It is desirable to set as large as possible.

If it becomes necessary to read the document D, the CPU 11 performs a control process for reading one document by a well-known procedure (step ST15). When the reading of one document is completed, the CPU 11 returns to the standby state of step ST13 and step ST14.

Now, step ST13 and step S
When the timer value is the predetermined value t in the standby state of T14,
If it becomes 7 or more, the CPU 11 proceeds to step ST11
The subsequent processing is repeated.

Thus, every time the time t7 elapses, the correction data is fetched.
Processing unit 7 when reading document D during the period
Used for shading correction in.

As described above, according to the present embodiment, when the power is turned on, the amount of light emitted from the exposure lamp 3 rises to the required minimum value (for example, 700 mV) of the CCD sensor 6 after the start of lighting of the exposure lamp 3. Time t1 required to do
Although the reading of the document D is not performed until the time has elapsed, the reading of the document D is performed if necessary after the time t1 has elapsed. Accordingly, the waiting time until the document can be read after the power is turned on is, for example, 270 seconds, which is the time required for the exposure lamp 3 to reach a stable light emitting state in the related art. In this case, the time is greatly reduced to, for example, 140.8 seconds, and the usability for the user is greatly improved.

Since the reading of the original is performed even when the transient range of the light emission amount of the exposure lamp 3 is used, the output level of the CCD sensor 6 changes due to the difference in the light emission amount of the exposure lamp 3. Since the shading correction is performed based on the correction data reacquired at each predetermined timing, it is possible to compensate for the above-described change in the output level of the CCD sensor 6 and to always perform reading with a constant quality.

Further, in the present embodiment, the timing at which the correction data is acquired is determined by the time required for the light emission amount of the exposure lamp 3 to change to the minimum change amount of the light emission amount of the exposure lamp 3 which affects the read image quality. The number of times correction data is acquired can be minimized,
As a result, it is possible to reduce the time required to acquire the correction data and improve the overall reading speed including various waiting times.

Further, according to the present embodiment, after the exposure lamp 3 is in the stable light emission state, the time is such that the variation with time of the stable light emission amount does not affect the reading quality, and a plurality of sheets are required. Since the correction data is acquired only at the interval of time t7 set as large as possible so that the original can be read, the time required for acquiring the correction data is reduced to include various waiting times. It is possible to improve the overall reading speed.

The present invention is not limited to the above embodiment. For example, the interval at which correction data is obtained may be shorter than that shown in the above embodiment.

In the above-described embodiment, the timing at which correction data is obtained is determined by time management. For example, a sensor for detecting the amount of light emitted from the exposure lamp 3 is provided, and correction is performed based on the output of this sensor. The timing for acquiring data may be determined.

In addition, various modifications can be made without departing from the spirit of the present invention.

[0071]

According to the first aspect of the present invention, reading of a document in the transition region of the exposure lamp is permitted, and the reading of the document in the transition region of light emission of the exposure lamp is performed. At least at a predetermined timing when the light emission amount of the exposure lamp exceeds the minimum light amount, and at each predetermined timing after which the light emission amount of the exposure lamp increases by a fixed amount, and the shading correction based on the correction data is performed. Document reading can be started before the exposure lamp reaches a stable light emission state, and changes in the light emission amount of the exposure lamp are compensated by shading correction to ensure sufficient reading quality. As a result, the waiting time before starting the actual document reading is reduced, thereby reducing the reading speed. A good document reader easy-to-use aims to above.

According to the second aspect of the present invention, the acquisition of the correction data in the transition region of the exposure lamp is performed at a predetermined timing determined based on the amount of change in the light emission amount of the exposure lamp regardless of the execution state of the original reading. Since the change amount of the light emission amount of the exposure lamp between the timings of acquiring the correction data is appropriately set, the execution frequency of the acquisition of the correction data in the transient region of the exposure lamp has an effect on the read image quality. As a result, it is possible to minimize the waiting time before starting the actual reading of the original in the transition area of the exposure lamp.

According to the third aspect of the present invention, the acquisition of the correction data in the stable light emission state of the exposure lamp is performed based on the change amount of the light emission amount of the exposure lamp regardless of the execution state of the original reading. Since the correction data acquisition is performed at each timing, by appropriately setting the timing of acquiring the correction data, the frequency of executing the correction data acquisition in the stable light emission state of the exposure lamp is minimized within a range that does not affect the read image quality. As a result, it is possible to minimize the waiting time before starting the actual reading of the original in the stable light emission state of the exposure lamp.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main configuration of a document reading apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a processing procedure of a control process by a CPU 11 in FIG. 1;

FIG. 3 is a diagram showing a change in the maximum output voltage of the CCD sensor 6 when the light emission state of the exposure lamp 3 is in a transition region.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Original platen 2 ... Shading correction plate 3 ... Exposure lamp 4, 5 ... Mirror 6 ... CCD sensor 7 ... Signal processing unit 8 ... Lighting circuit 9 ... Carriage drive mechanism 10 ... Timer 11 ... CPU 12 ... ROM 13 ... RAM 14 ... bus

Continued on the front page F term (reference) 2H108 AA01 CB01 GA01 5B047 AA01 BA02 BB02 BC11 CA19 CB04 DA04 DC06 5C072 AA01 BA05 CA04 EA05 FB13 RA15 UA02 5C077 MM03 PP06 PP72 PP78

Claims (3)

[Claims] An image sensor generates image data corresponding to a reflected light image from a document when the document is exposed by a cold-cathode tube type exposure lamp, and exposes a predetermined reference color surface by the exposure lamp. A document reading device that performs shading correction of the image data based on correction data generated by the image sensor in accordance with the reflected light from the reference color surface when the exposure lamp is in an off state. Reading permission means for permitting the start of reading of a document from a predetermined timing when the light emission amount of the exposure lamp exceeds the minimum light amount required by the image sensor when starting the lighting of the lamp; and the light emission amount of the exposure lamp. During the period from the minimum light amount to the stable light emission amount in the stable light emission state, the light emission amount of the exposure lamp Correction data acquisition control means for acquiring the correction data at a predetermined timing exceeding the minimum light amount and thereafter acquiring the correction data at every predetermined timing at which the light emission amount of the exposure lamp increases by a predetermined amount at least thereafter A document reading device comprising: 2. After a predetermined timing when the light emission amount of the exposure lamp exceeds the minimum light amount, the correction data acquisition control means performs the correction data only at a predetermined timing at which the light emission amount of the exposure lamp increases by a fixed amount. 2. The document reading apparatus according to claim 1, wherein correction data is obtained. 3. An image sensor for generating image data corresponding to a reflected light image from a document when the document is exposed by a cold cathode tube type exposure lamp, and exposing a predetermined reference color plane by the exposure lamp. A shading correction of the image data based on the correction data generated by the image sensor according to the reflected light from the reference color plane when the exposure lamp is in a stable light emitting state; In the light emission state, the correction data of the correction data is obtained at predetermined timings at each time at which it is possible to read at least a plurality of documents within a range of time required for a predetermined amount of time-dependent change in the light emission amount of the exposure lamp. A correction data acquisition control means for acquiring is provided.