JPH0321160A - Image reading device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image reading device and an image reading device for forming an image signal that is faithful to the ribs.

In recent years, manuscripts have been read using solid-state imaging devices such as CCDs, and the read electrical signals are further converted into analog and digital signals, which are then subjected to various digital processing, and then formed into images with printers or sent to remote locations. The device has been put into practical use. In order to stabilize the operation of this type of device, an image signal correction circuit is used that corrects the image signal due to uneven light emission of the fluorescent lamp, uneven light intensity distribution of the optical system, uneven sensitivity of the CCD, etc. using a tental signal. There are many things. Conventionally, this type of circuit, especially equipment that handles high-speed image signals, has had to use expensive circuit elements in order to perform high-speed processing, and therefore, when complex correction processing and high accuracy are required. had the disadvantage that it was very expensive due to the large circuit scale.

For example, in a correction method that stores the image signal of a standard white board as a digital correction signal in memory, etc., and corrects the image signal of the read document based on this data, high-speed processing is performed to store the image signal in memory. A large amount of noise will be mixed into the corrected signal. Therefore, in order to remove this noise, it was necessary to take the average value of neighboring pixels.

For this reason, additional circuits such as adder circuits, multiplier circuits, circuits for controlling the timing of calculations, etc. are required, and devices capable of high-speed operation must be used, resulting in very high costs.

Furthermore, in this type of device, even if there is a defect in the read image, there is no way to discover the cause of the failure other than to make a hard copy using a printer or the like and check the image quality. Therefore, it takes time to discover a failure, resulting in, for example, decreased productivity in a factory and decreased serviceability in the market.

Furthermore, in this type of apparatus, the amount of light for exposing the document is controlled in order to maintain the read image at a constant density level.

However, when fluorescent lights are used, there is a drawback that if the fluorescent lights are dimmed when they are cold, they do not turn on easily and cannot be dimmed sufficiently.

In addition, in this type of device, for example, if the tube wall temperature of a fluorescent tube deviates from the temperature range suitable for operation, it becomes difficult to turn on or the luminous efficiency decreases, so reading the image under such conditions will result in poor image quality. However, there were disadvantages in that the image quality deteriorated and noise from flickering lights was mixed into the read image.

The present invention has been made in view of the above points, and an object of the present invention is to expose a document with an appropriate amount of light by optimizing the temperature of a light source for document exposure and to perform good image reading. a reading means for photoelectrically reading a document image exposed by the light source, a detection means for detecting the temperature of the light source, and a control for controlling the temperature of the light source based on the temperature detected by the detection means. The present invention provides an image reading device having means.

Another object of the present invention is to provide an image reading device that prevents image reading when the temperature of the light source is not at a predetermined value when reading an image exposed by a light source.

Another object of the present invention is to provide an image reading device that performs dimming control of the light source after completion of temperature control of the light source and then corrects the read signal when reading an image exposed by the light source.

Hereinafter, the present invention will be explained in detail based on examples.

FIG. 1 is a simplified configuration diagram of a document reading device to which the present invention is applicable.

A document placed face down on a document table 9 is illuminated with a fluorescent light 2, and an image of the document is formed on a line-reading CCDT via reflection mirrors 3, 5 and an optical lens 6, and the document is scanned in the main scanning direction. Perform reading. The fluorescent lamp 2 and the reflecting mirrors 3 and 5 are moved by an optical system motor (not shown) along a guide rail 8 to scan the document table 9 and perform reading in the sub-scanning direction.

The CCD 7 converts the original image into an electrical signal. In this embodiment, so-called shading such as uneven light emission of the fluorescent lamp 2, uneven density due to dirt on the reflective mirrors 3 and 5, uneven luminous intensity distribution of the optical lens 7, etc. is removed.

In this embodiment, a standard white plate 1 serving as a reference is read prior to the above-mentioned scanning, and then scanning is performed and image signal correction is performed based on the read signal of the standard white plate.

The standard white plate 1 is a plate for measuring the above-mentioned image signal, and its entire surface is uniformly painted, for example, white.

FIG. 2 is a diagram showing an example of a circuit configuration of a document reading device for performing image signal correction according to the present invention.

The document is illuminated by a fluorescent light 15, and the reflected light forms an image of the document on the COD 7 via the optical lens 6. C.C.
D7 converts the original image into an electrical signal, and outputs data for one line of raw scanning as an analog electrical signal in accordance with the main scanning synchronization signal.

The amplifier circuit 10 amplifies this signal and converts it to the A/D converter 1.
After being converted into a digital signal in step 1 and subjected to shading correction in a shading correction circuit 12, it is connected to an external circuit as a digital image signal output.

The external circuit is, for example, a binary signal conversion circuit such as a binarization circuit or a dither processing circuit. The binary signal is, for example, LBP
, image electronic files, electronic transmission equipment, and other equipment.

In FIG. 2, a control circuit 21 is a control circuit for controlling the shading correction circuit 12 and the temperature and dimming of the fluorescent lamp 5, and operates upon receiving instructions from the main body control circuit 24.

An operation section 25 is connected to the main body control circuit 24, and issues instructions to start reading the document and displays the status of the apparatus.

The dimming circuit 18 is a control circuit for controlling the light amount of the fluorescent lamp 15, and performs dimming by controlling the lighting time by pulse width modulation according to instructions from the control circuit 2l.

The thermistor 13 adjusts the tube wall temperature of the fluorescent light 15 to ijll+
This is a temperature sensor for determining the temperature. The measured output of the thermistor 13 is A/D converted by an A/D converter 22 and inputted to the control circuit 21, and the input data is used to control the temperature control circuit 19.
By controlling the dryer circuit 20, the heat-retaining heater 14, and the cooling fan motor 16, the temperature of the tube wall of the fluorescent lamp 15 is set to 4. Control is performed so that the fluorescent lights around 0'C emit light most efficiently and stably.

Specifically, the temperature of the tube wall of the fluorescent light 13 is measured using thermistor 3, and when the measured temperature is below 40°C, the heater 14 is turned on and the fan motor 16 is turned off.
When the temperature is above 'C, the heater 14 is turned off and the fan motor 16 is turned on to control the temperature. In reality, the fluorescent lamp itself generates heat due to its own light emission, so it is necessary to provide a hysteresis characteristic to the above-mentioned on/off temperature settings.

Figure 3 shows the Schiede ink correction circuit 12 and the control circuit 2]
FIG. 2 is a more detailed configuration diagram of FIG.

The image signal output from the A/D converter 1l is of type D.
The timing is adjusted by the flip-flop 50, and the result is input to the ROM 54 which stores the calculation result of the shading correction, and is corrected. The output signal of the D-type flip-flop 50 is passed through a gate circuit 5 as necessary so that an image signal for one main scanning line, that is, a CCD] line can be stored in the RAM 52.

The RAM 52 stores an image read from the standard white board 1, and reads it out in synchronization with the actual original read image.
By applying it to the address signal line of ROM54, the ROM
By reading out the calculation results of the shading ink correction stored in the 54, it is possible to remove shading caused by uneven light emission of the fluorescent lamp 2, uneven density due to dirt on the reflective mirrors 3 and 5, uneven luminous intensity distribution of the optical lens 7, etc. Perform the calculation for.

The D type flip-flop 53 is a circuit for adjusting the timing of the image signal read out from the RAM 52.

The selector 57 is a switching circuit for switching between the address signal output by the CPU 60 and the count signal (horizontal address signal) of the counter 58 that counts the CL○CK signal when reading the pixel signal from the CCD 7. .

That is, when writing the image signal data of the standard white board 1 to the RAM 5 2, and when reading it and performing shading correction, it is switched to the horizontal address signal of the counter 58, and when the CPU 60 directly reads the contents of the RAM 52, it is switched to the horizontal address signal of the counter 58. It is used by switching to the output shift signal of the CPU 60.

The counter 58 is initialized by a synchronizing signal HSYNC signal indicating the start of reading 1 line of main scanning, and repeats the counter 1 operation for each line.

The counter 59 counts this HSYNC signal by 1 and 1 and is used, for example, when changing the pattern in the sub-scanning direction when performing dither processing.

The timing control circuit 66 is a circuit that receives commands from the CPU 60 and controls the selector 57, the gate circuit 51, and the bidirectional bus driver 56.

The timing control circuit 66 controls the following three types of operation modes.

(1) Aging Data Sampling This is an operation mode in which the image signal read from the Moto standard white board 1 is stored in the RAM 52. Game 1/Circuit 51 H S Y
The image signal is written into the RAM 52 by switching the selector 57 to the address signal of the counter 58 by operating in a section corresponding to l main scanning lines indicated by the NC signal.

(2) Scheidink correction mode This is an operation mode in which the image signal input to the D type flip-flop 50 is corrected based on the image signal written in the RAM 52. At this time, the selector 57 is operated by the address signal of the counter 58, and sequentially reads out the data written in the two-state ink data sampling mode from the RAM 52. Make corrections. Gate 1 circuit 51 does not operate at this time.

(3) CPU mote There is an operation mode that allows the CPU 60 to directly read and write the contents of the RAM 52. At this time, the bidirectional hash driver 56 is activated, is directly connected to the data path of the CPU 60, and is used to read the contents of the RAM 52 and perform arithmetic processing, or conversely change the contents. At this time, the selector 57 is switched to the address signal line of the CPU 60,
Further, the gate circuit 51 does not operate.

Now, in the circuit described above, the CPU 60 executes the control program stored in the ROM 6 and executes the working RAM.
62, I/O port 63, serial circuit 64, and display circuit 65 are used to perform IIj control.

The timer 67 is a circuit that provides pulses to the CPU 60 at fixed time intervals. The CPU 60 manages time by using this pulse signal as an interrupt signal.

Next, the principle of dimming will be explained using FIG. 4.

In FIG. 4, the horizontal axis indicates an interval of 1 frame, and the vertical axis indicates the gray level of the image signal. In this embodiment, the standard white board 1 is read, and the above shading data
This corresponds to data stored in RAM 52 in sampling mode.

In this embodiment, the data stored in the RAM 52 is 6 bits, and the value 63 is the blackest level, and the value O is the whitest level.

Now, in FIG. 4, curve a shows a state where the amount of light from the fluorescent lamp 15 is insufficient, curve b shows a state where the amount of light is appropriate, and curve C shows a state where the amount of light is too large. The shading correction method in this embodiment is based on the standard white plate 1.
Since the correction is performed based on the data read, when the reading is saturated as shown in curve C, the correction cannot be made.

Furthermore, if the amount of light is insufficient as shown by curve a, the amount of correction by calculation increases, resulting in a disadvantage that the S/N ratio of the read image signal deteriorates. Therefore, the amount of light from the fluorescent lamp 15 needs to be controlled so that the whitest point X of the read data just reaches the value O, as shown by curve b.

FIG. 5 shows an example of data stored in the RAM 52 when the fluorescent light 15 deteriorates after the fluorescent light 15 is dimmed using the standard white board 1.

Curve d shows a state in which the fluorescent lamp 15 has deteriorated so much that even when it is fully lit, the black level remains by a value L and the dimming is insufficient.

Curve e shows a state where both ends of the fluorescent lamp 15 have progressed to blackening and the amount of light at the end of the tube has decreased.

Assuming that the curve f is normal data, the density levels at both ends of the valid section in one frame are set to the value n1 and the value 1 (.Similarly, the density levels at both ends of the effective section of the curve e are set to the value m1 and the value j.

As explained above, in the aging correction in this embodiment, when the read value of the standard white plate 1 is dark as shown by the curve a in FIG. 4, the S/N deteriorates.

Therefore, in order to prevent this, the darkness limit is set to a predetermined value α
It is possible to determine the deterioration of the fluorescent lamp 15 by comparing this with the concentration level of the effective section.

In the example of FIG. 5, the state of m>α>n, j>α>1 is shown. Of course, in the above deterioration judgment, only one end has a value, for example, m>α, j<α. It goes without saying that it may be determined that the fluorescent lamp 15 has deteriorated even if the value exceeds α.

Figure 6 shows that there are defects in the CCD 7, RAM 52, etc.
FIG. 3 is an explanatory diagram for detecting a failure such as a defect occurring in a read image.

Generally speaking, when the above-described defect occurs, the density level of the corresponding pixel becomes a constant value, or the dynamic range deteriorates extremely. In FIG. 6, the curve t represents the RAM 52 when the fluorescent light 15 is dimmed.
The curve U shows the read data when the fluorescent light 15 is bright after dimming. The peak value p1 and the peak value r indicate the case where the density of the defective pixel is constant, and the peak value q1 and the peak value S indicate the case where the dynamic range of the defective pixel has decreased.

To find a defective pixel using such data, there is a method of calculating the difference between adjacent pixels and determining the pixel as a defective pixel when the difference exceeds a predetermined value. However, this method has the disadvantage that when specific pixels are consecutive, the difference between the pixels becomes small, resulting in false detection.

Therefore, in this embodiment, after determining the average density level of curve t and curve U, this is compared with each pixel, and if there is a difference of more than a predetermined value, it is determined as an abnormal pixel. Removes shortcomings.

Furthermore, if the density level of an abnormal pixel happens to be close to the average density level, it is possible that detection failure of the abnormal pixel may occur. Therefore, it is desirable to detect the abnormal pixel using at least two or more average density levels. In this embodiment, abnormal pixels are detected with the fluorescent light 15 turned off and after dimming.

Next, the control procedure will be explained using the flowcharts shown in FIGS. 7 to 14.

FIG. 7 is a flowchart showing the main control procedure of the main body control circuit 23.

First, when the power is turned on, the operating section 24 and each drive circuit are initialized in step SPI, and a polling operation is started to start reading.

In step SP2, a branch is made to determine whether or not the switch of the reading star 1 of the operation section 24 has been pressed.

In the case of starting reading, it is confirmed in step SP3 that the reading position of the escape optical system is at the position of the standard white plate 1 (home position), and then in step SP4.
Proceed to. In step SP4, it is determined whether or not the temperature control for maintaining the temperature of the fluorescent lamp 15 at a predetermined temperature has been completed. If not, stable image reading cannot be guaranteed, so document reading is started. prevent. If the temperature control has been completed, the process advances to step SP5.

In step SP5, abnormal pixels are detected with the fluorescent light 15 turned off, and in step SP6, the fluorescent light 15 is turned off.
is turned on, and the dimming control of the fluorescent light 15 is performed in step SP7.

In step SP8, it is determined whether or not there was an error in the dimming control, and if there was an error, an error is displayed and reading of the document is prevented.

If there is no error in the dimming control, the process advances to step SP9, where an abnormal pixel is detected in the state where the fluorescent light [5] is lit, and step SP]. Proceed to O. Note that if the number of abnormal pixels is too large, an error is displayed and the reading operation is prohibited.

In step SPIO, the value read from the standard white board 1 is stored in the RAM 52.

In step SPII, the abnormal pixels detected in steps SP5 and 9 are corrected, and then in step SPII, the abnormal pixels detected in steps SP5 and 9 are corrected.
At step 12, reading and scanning of the original is started.

In step SP13, it is determined whether or not the required number of document reading scans have been completed, and if not, the process returns to step SP7 and the operations described in section 2 are repeated.

On the other hand, when the required number of document reading scans have been completed, the fluorescent light 15 is turned off, the document reading is completed, and a new reading star 1 switch is activated. 8 and 9 are flowcharts showing the control procedure of the CPU 60 of the control circuit 21. FIG.

In FIG. 8, after turning on the power, at step SP50, a flag, an I/O port 63, a serial circuit 64, a display circuit 6
After performing the initialization such as 5, the process goes to step S P 5 ].

In step SP51, it is determined whether or not there is an operation command input from the main body control circuit 23. If not, the display circuit 65 displays the status of light control, temperature control, etc. If there is a command input, the process proceeds to step SP52, and branches to each step depending on the content of the command to perform processing. The details of each process are as follows.

・Step SP53 Turn on the fluorescent light 15, set the flag FLON to 1, and similarly,
Set flag ERRCNT to O. Flowchart 1: The flags, counters, and data used in the explanation are AM62 and CP.
It refers to data that the U62 reads and writes for processing.

-Step SP54 Turn off the fluorescent light 15 and set the flag FLON to the value O.

・Step SP55 Performs dimming control.

・Step SP56 The detected error information is transferred to the main body control circuit 23.

・Step SP57 Abnormal pixels in one frame are detected.

-Step 58 The abnormal pixel detected in step SP57 is corrected.

-Step SP59 The image signal read from the standard white board 1 is stored in the RAM 52 after noise removal.

- Step SP60 The data stored in the RAM 52 is transferred to the external circuit via the serial circuit 64.

After completing the above processing steps, the process returns to step SPI and repeats the control procedure described above.

FIG. 9 shows timer processing that is executed at fixed time intervals using a pulse signal given by the timer 67. This process is performed after initialization in step SP50 is performed.
Execution begins.

In step SP61, a process is performed to control the temperature of the tube wall of the fluorescent lamp 15 to about 40° C., which allows stable lighting.

Next, flowcharts and FIGS. 10 to 14, which describe in more detail the processing contents explained in FIGS. 8 and 9, will be explained.

FIG. 10 is a flowchart describing in detail the control contents of step SP61. Step SPIOO is
A disconnection of the thermistor l3 is detected, and if the thermistor is disconnected, the error details are stored in the RAM 62 and displayed in step SP51. Various errors described below are handled in the same way, and the error details are transferred to the main body control circuit 23 in step SP56 as necessary.

Now, if a disconnection is detected, temperature regulation control is impossible, so the process proceeds to step SPIIO, where both the heater 14 and the fan motor 16 are turned off, and the control is ended. If the thermistor disconnection is not detected, the temperature measurement output of the thermistor 13 is converted from analog to digital using the A/D converter 22 in step SPIOI, and this measurement output is converted to T0.
Let it be C.

The above-mentioned thermistor disconnection detection in step SPIOO may be performed by determining that the thermistor is disconnected when the measured temperature T reaches a discrete value that cannot be taken originally (a value that can be taken when the disconnection occurs).

In step SP102, it is determined whether or not the measured temperature T is less than 30. If not, the process proceeds to step 104, and it is determined whether or not the measured temperature T is less than 40. Step SP10
2. By executing step SP104, T<3
0, step SP103, 30≦T<40, step SP105, and T≦40, step SP10.
6 will be executed.

In step SPI03, the flag HTUP, which takes a value of 1 when the temperature control of the fluorescent lamp I5 is completed, is set to a value of 0, indicating that the temperature control is insufficient. Conversely, in step SP106, the plug HTUP is set to the value 1.

In step SP105, the flag FLON is checked to determine whether the fluorescent light 15 is on. Flag FLON
When is 1, that is, when the fluorescent lamp 15 is on, the tube wall temperature rises due to self-heating, so proceed to step SP109, turn off the heater 14, and turn off the fan motor l6, so that the measured temperature T is Control is performed so that the value slowly approaches 40. If the flag FLON has a value of 0, the process proceeds to step SP107.

In step SP107, the flag H T E R R, which becomes 1 when it is determined that the heater 4 is disconnected, is checked.
If the value is 1, the process proceeds to step SPIIO, and the heater l4
is turned off, and the fan motor 16 is turned on to perform cooling for safety.

In step SP108, the heat 14 is turned on and the fan is turned on.
The motor l6 is turned off and control is performed to increase the tube wall temperature of the fluorescent lamp 15.

In step SPILL, the flag HTON, which takes the value 1 when the heater 14 is turned on, is checked, and if the value is O, the process proceeds to step SP112, where the flag I-IT O N is set to the value l,
Counter HTC that measures the energization time of the heater 14
Initialize by setting NT to the value O.

In step SPI13, the counter I-IT C N
T is incremented by 1, and when the energization time measured by the counter HTCNT exceeds the allowable time M in step SP115, the heater 14 is determined to be disconnected and the process proceeds to step SP114.

In step SP114, the flag HTERR is set to the value 1, and error processing for heater disconnection is performed.

The flag HTON is set to the value O in step SP116 after the heater l4 is turned off.

According to the temperature control described in paragraphs-1-2 and -1-2 below, the control temperature is divided into two points of 30° (:, /1.0°C) and has a hysteresis special feature, so stable control is possible. It is now possible.

Next, the procedure for controlling the dimming of the fluorescent lamp 15 will be explained using FIG. 11.

In step SP150, the flag, data, and counter are initialized prior to control. Data F1, D A
i'A is dimming data given to the dimming circuit 18; a value of 255 means full lighting, and a value of O means lights out.

Data OFFSET is data FI-DA i'
A i. There are m values to add and subtract. Kaunk F I. ．．
CNT is a counter for counting the number of times for repeat control. The counter FLERR is a non-counter for measuring the turning on and off state of the fluorescent lamp 15, and counts the number of times when the data read for dimming control is very dark.

In addition, the image signals handled in this embodiment are 6 hits 1 (values 0 to 63), and the RAM 52 uses 8 hits 1, so the top 2 hits 1 are used for purposes other than image signal storage. It is used for the purpose of

In step SP151, the process waits for the previously output dimming data to appear as a change in the amount of light from the fluorescent lamp 15, and then proceeds to the next step.

Step S P1. At step 52, the image signal read from the standard white board 1 is stored in the RAM 52 through the shading data sample link mode.

Step S P1. 53, four consecutive pixels of the image signal data stored in the RAM 152 are added as one block, and the block with the smallest numerical value (the brightest) is detected (one L block, added value S).

Step SPI! In step SP155, set the data OFFSET to half the value.
When the value becomes less than 1, a process is performed to set the value to 1. By repeating the control, the value of data OFFSET becomes 64, 32, 16, 8, 4, 2.
, 1, 1, etc.

At step SP156, branching is performed depending on the value of the addition value S.

In step SP157, data F
Subtract data OFFSET from L D AT A,
Control to reduce the amount of light.

In step SP158, data FLDA. T
It is determined whether A has become a negative value, and if it is negative, the data FI-DATA is set to 0 in step SP159, and processing is performed as a dimming error l.

Dimming error 1 is treated as an error because it is a logically impossible state in which a white level signal is read even though the data supplied to the dimming circuit 18 indicates that the light is off. In this case, it is possible to consider that a defect has occurred in the dimming circuit 18, the amplifier circuit 10, etc.

On the other hand, if the added value S is not the value O, step ST'l
Proceeding to step 60, it is determined whether the added value S is dark data above the value 24012J, and if the value is 240 or more, it is assumed that the fluorescent light 5 is not lit and the counter F L E is set.
Increment R by 1.

At step SP161, the amount of light is considered to be insufficient, so the data FI. Data O to D A T A
Control is performed to increase the amount of light by adding F F S E 'F.

Step S P1. 6 In 2, the data FLDAT
Confirm that A does not exceed 255, and if the value exceeds 255, data FI. , set DATA to the value 255. Here, the reason why an error is not made as an insufficient amount of light is that when a fluorescent light is turned on, the amount of light gradually increases from the start of lighting.

Step S P1. At step 63, the data FLDATA calculated in the steps described above is output to the dimming circuit 18, and the counter FLCNT is incremented by one.

In step SP164, the dimming control is ended when the counter FLCNT reaches 50, and in step SP67 it is determined whether the counter FLERR exceeds the value 25, and if it exceeds the value, the fluorescent light 15 is turned off. It doesn't light up easily,
Alternatively, it is assumed that the light does not turn on at all and is treated as a dimming error.

Step S P1. 6 At 5, the counter FLCN
It is determined whether or not T has reached 25, and if not, the counter FI. E R R is value 15
If the value exceeds 15, it is assumed that the fluorescent light 15 is not turning on easily and the counter FLC is determined.
Continue the above step SP15 until NT reaches the value 50.
1 to step SP162 are repeated. After controlling 25 times or 50 times, step SP168
Proceed to.

In step SP168, the average value of the effective pixels at both ends described in FIG. 5 is calculated to remove noise. (
Average value A) In step SP169, the difference between the l pixel average value obtained by dividing the added value S by the value 4 and the above average value A is calculated, and if the difference exceeds the value 15, it is determined that the end portion of the fluorescent lamp 15 has deteriorated. The dimming error 3 is processed as recognized.

The processes of step SP169 and step SP169 are performed individually at both ends of the effective pixel.

In step SP170, it is determined whether the added value S is controlled to be around the value O by checking whether the added value S is less than the value 8.

If the added value S is equal to or greater than 8, processing for dimming error 4 is performed, assuming that the deterioration of the fluorescent lamp 15 has progressed throughout the tube and the amount of light is insufficient.

According to the dimming control described above, it is possible to easily detect abnormalities during dimming, and the data OFFSE
By making the value of T variable, convergence of control is prevented, and when the rise characteristics during lighting are not good, stable dimming control can be performed by lengthening the control time.

Next, the control procedure for the shading process will be explained using FIG. 12.

In step SP200, the counter CNT is set to the value O,
All the shading buffer portions of the RAM 62 are set to the value O.

In step SP201, the image signal obtained by reading the standard white board 1 in the above-mentioned shedding data sampling mode is stored in the RAM 52, added to the contents of the previous shedding buffer for each corresponding pixel, and stored in the shedding buffer. .

In step Sl203, the counter CNT is incremented by 1, and steps SP201 to SP203 are repeated until the value reaches 4.

In step SP204, the contents of the shading buffer are divided by 4 to obtain an average value, which is then stored in the RAM 52 (RAM for shading correction), and the shading process is completed.

According to the shading process described above, the RAM 52,
By simply processing the data in the RAM 62 with the CPU 60, the image signals read from the standard white plate are averaged and noise is removed.This can be achieved at a very low cost without using any special adders or dividers. There is. Further, a more advanced noise removal method using a devised algorithm can be easily applied by simply changing the control program stored in the ROM 61.

Next, the control means for abnormal pixel detection will be explained using FIG.

Steps SP250 to SP253 are steps SP200 to SP203 of shading processing.
This is a processing step corresponding to step SP25/1.
When proceeding to
The added value of the image data stored in 2 is similarly stored.

The difference from the shading process is that the data stored in the RAM 52 is processed not only after dimming but also when the fluorescent light 15 is turned off.

In step SP254, the contents of the shading buffer are divided to obtain an average value.

In step SP254, the average value AV of all pixels in the effective image section is determined, and then the process proceeds to step SP25&.

In step SP255, the counter CNT is set to 0,
The following steps SP257 to 261 are repeatedly executed until it is determined in step SP261 that the count value has reached the number of effective pixels E.

In step SP257, the value of the shading buffer specified by the contents of the counter CNT (for example, when the stored contents of the counter CNT is the value 100, the shading buffer value specified by the contents of the counter CNT is
1000th data from the beginning of the buffer) and the average value AV is calculated.

In step SP258, the absolute value of the difference Z is compared with a predetermined value C, and if it exceeds the value C, the error is large, so it is determined that the pixel is abnormal, and the process proceeds to step SP259.

In step SP259, the value of the counter CNT is stored at the address of the abnormal pixel memory (part of RA.M62) indicated by the contents of the counter ERRCNT, which is set to 0 in step SP53, It is accumulated as number 1.

At step SP260, the contents of the counter ERRCNT are incremented by 1.

According to the abnormal pixel detection explained above, since detection is performed when the light is off and when it is lit and dimmed, it happens to be detected when the difference between the abnormal pixel and the normal pixel is small. Figure 14 shows how an abnormal pixel detected by abnormal pixel detection can be replaced with the previous normal pixel to prevent detection leakage and to obtain the cumulative results of two detections. FIG. 7 is a diagram illustrating a control procedure for correcting abnormal pixels to be replaced.

Step S I) 3 0 0 is the counter E R R
This is a processing step in which the process ends when the content of CNT reaches the value 0. If the value is not 0, step S
The processes from P301 to SP303 are executed once.

In step SP301, the contents of the bar field (1 ADR) indicated by the contents of the counter ERRCN T are read from the head of the buffer for storing abnormal pixels.

In step S P 3 0 2, the M S B of the data corresponding to the ADR address from the beginning of the Schieden ink correction RAM 52 is set to the value 1.

In this embodiment, when the MSI of the RAM 52 is set to the value 1, an operation is performed in which an abnormal pixel is replaced with the previous normal pixel. Further, in step SP302, A
Although the MSB of the DR address is set to the value 1, the timing may be shifted depending on the circuit configuration, so the MSB of data before and after the ADR address may be manipulated.

Next, FIG. 15 will be explained.

FIG. 15 is a diagram describing the periphery of the RAM 52 and ROM 54 in more detail.

The D type flip-flop 50 is, for example, T T
It is a 6-bit 1 D type flip-flop such as L74LS174, and in addition to the data input terminal and data output terminal, it has clock input terminals CK,
It has clear input terminals CLR. The clear input terminal holds the signal connected to the data input terminal when the data output terminal becomes the value O when the value is set to O, and the clock input terminal CK rises and the clock is manually input.

Therefore, the data input terminal of the D type flip-flop 50 should be pulled up and the data input terminal should be pulled up. ) ih: By disconnecting the signal input to the child, it becomes possible to generate a pseudo image signal pattern of total hit l/value O or value 1 using the signal of the clear input terminal. In addition, if the signal input to the clock input terminal is made so that a rising signal does not occur at an abnormal pixel, the data output terminal will continue to output the normal pixel held by the previous clock and can be used for abnormal pixel correction. be.

Ant Gate 71, Inharter 72 corrects abnormal pixels,
Ant gate 70 and inharter 77 are logic circuits for generating a bang.

An1...The input terminals 74 and 76 of the gate 70 are pulled up by resistors 73 and 75, respectively, and when a pattern is generated or required, the horizontal address signal of the counter 58 or the counter By connecting to the vertical address signal No. 59, a pattern as shown in FIG. 16 can be obtained.

FIG. 16 shows that the data input terminals of the D-type flip-flop 50 are open, and the input terminals 74 and 7
6 is an example of image output when horizontal and vertical address signals are input so that the pattern has the same pitch in both the main scanning direction and the sub-scanning direction.

The hatched area indicates where all the data output terminals of the D-type flip-flop 50 have a value of 1.

The pitch and pattern of the patterns in the main scanning direction and the sub-scanning direction can be varied by selecting each address line signal to be input. For example, a striped pattern can be obtained by connecting only one of the address signals.

In addition, in this embodiment, if the 6th bit (LSB of RAM] 52 is set as the 0th hit, the 0th to 5th hits are allocated for image signal storage, and the 1st MSB of the 7th hit is allocated for abnormal pixel detection. It is possible to obtain the same effect by using an arbitrary 1, 0 pattern in the CPU 60. In this case, writing a value 1 to the 6th bit of the RAM 52 causes the D type flip-flop 50 to
The data output terminals of all become the value O.

Similarly, when writing the value 1 to the MSB of RAM52,
The AND gate 7l gates the C L O C K signal, and the abnormal pixel correction described above is performed without holding the data of the corresponding pixel.

In Figure 15, D type flip-flop 5
Abnormal pixel correction and pattern generation are performed in the D-type flip-flop 55 in the subsequent stage. It goes without saying that they may be separated like pattern generation.

The gate circuit 5l is, for example, TTL74LS244,1
・Using a light state buffer or the like, the timing control circuit 66 controls the error game 1 control signal, and when the value is set to 0, the image signal is written to the RAM 52. At this time, the value O is written into both hits of the RAM 52 by connecting the MSB, 6th bit 1st, of the input signal to GND.

The D type flip-flop 53 is, for example, T T
Use L 7 4 L S 2 7 3. The clear input terminal CLR is used as a correction enable signal, and when the value is 1, shading correction is performed according to the stored contents of the RAM 52, and when the value is 0, all outputs are the value 0, so no shading correction is performed.

The correctable signal may be normally set to a value of 1 using, for example, a dip switch, and may be set to a value of O when confirming whether the shading operation is being performed normally.

As explained above, according to the present invention, the temperature of the light source is controlled based on the temperature detected by the detection means for detecting the temperature of the light source for exposing the original, so that the original light source exposed to light by the light source controlled to an appropriate temperature is The image can be read, and therefore, good image reading is possible.

[Brief explanation of the drawing]

FIG. 1 is a simplified configuration diagram of a document reading device to which the present invention can be applied, and FIG. 2 is a configuration diagram showing a specific electric circuit configuration for performing shading correction according to the present invention.
Figure 3 is a block diagram that describes Figure 2 in more detail, Figure 4 is an explanatory diagram to explain the principle of dimming control, and Figure 5 is a diagram to explain the principle of deterioration detection of fluorescent lamp 15. An explanatory diagram, FIG. 6 is an explanatory diagram for explaining the principle of abnormal pixel detection, FIG. 7 is a control flow chart of the main body control circuit 23, and FIG.
9 is a control flow chart of the control circuit 21, FIGS. 10 to 14 are more detailed control flow charts of the control circuit 21, and FIG. 15 is a diagram showing an example of a circuit for abnormal pixel correction and pattern generation. , FIG. 16 is a diagram showing an example of a pattern, l is a standard white board, 2 and 15 are fluorescent lights, and 7 is a COD
, 13 is a thermistor, 14 is a heater, l8 is a dimming circuit,
19 is a tone circuit, 21 is a control circuit, 51 is a gate circuit,
54 is a ROM, 52 and 56 are RAMs, and 58 and 59 are counters. -497 499

Claims (1)

[Scope of Claims] A light source for exposing an original; a reading means for photoelectrically reading the original image exposed by the light source; a detection means for detecting the temperature of the light source; and a temperature detection means based on the temperature detected by the detection means. An image reading device comprising: control means for controlling the temperature of the light source.