JP3761069B2 - Image reading device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a reading apparatus, and more particularly to a reading apparatus applicable to a digital copying machine, a scanner apparatus, and the like.
[0002]
[Prior art]
In the conventional reading device, the black pixel area of the CCD or a partial area of the data is sampled as a black level after AD conversion, and subtracted and removed as an offset level from the data of the effective pixel area. To obtain image data. This sampling region is presented by a gate signal, and a subtraction value is determined by averaging the plurality of sampled data.
Further, in such a reading apparatus, the error detection means for the lamp burnout (non-lighting) is turned on by detecting a certain white level using the reference white plate data when the shading process is performed or the read data. The non-lighting is determined.
[0003]
For example, Japanese Patent Laid-Open No. 10-257249 discloses data obtained by optically reading an image of a document irradiated with light from a light source and a reference density plate, and a light quantity change detecting means reading the reference density plate with a CCD. A method is disclosed in which the amount of light quantity change of the light source is obtained by sampling every predetermined period, and further, the light quantity level of the light source for reading the image of the original is set.
Further, in the conventional reading apparatus, the reference white plate reading area where shading is performed and the area where the document is read have gate signals in the sub-scanning direction, and shading data according to the assertion (on state) of each gate signal. Sampling and image data processing are performed.
[0004]
[Problems to be solved by the invention]
In the conventional error detection means for lamp burnout (non-lighting), when reading a document, the scanner normally reads the reference white plate 20 for each scan, and performs gain adjustment and shading correction data generation for white level optimization. It has been broken. Specifically, the state of the lamp 24 is monitored using the value of the shading data (for example, the peak value is detected), and when this value is smaller than a predetermined threshold value, or within the reading area of the reference white plate Then, the gain adjustment is performed before shading is started, and error processing is performed by determining that the lamp is not lit (lamp out) based on the white level peak value for gain adjustment detected at this time.
As described above, in the conventional image reading apparatus, the white level is detected at a fixed timing in the reading sequence control to determine the lamp abnormality, so that even if an abnormality occurs at the detection interval, the state remains as it is. Left unattended.
Also, in reading devices that use sheet-through document feeders (document feeders: DF), the white plate is read once every multiple times without reading the reference white plate for each scan to ensure productivity. The shading data and the gain correction value are also used until the next generation. In this case, the influence of the lamp abnormality affects the reading of a plurality of documents, which is not preferable from the viewpoint of safety as well as quality. A situation may arise.
[0005]
Therefore, an object of the present invention is to always detect and store the peak data of the main scanning line regardless of the reference white plate area, etc., and determine whether the value is appropriate, that is, whether the reference value has been reached, It is to be able to perform error determination at an arbitrary time.
[0006]
Regardless of the lamp status, the position of the sampling gate signal is changed according to shading and the assertion gate signal of the document reading area signal, and the position of the black pixel sampling gate signal is changed according to the lamp on / off control. Thus, in the shading and document reading area, the black pixel area is sampled and the offset level is removed as described above to obtain image data, and in the other areas, the effective pixel area is sampled. By returning the carriage while the lamp is lit or lighting, information on the background level of the document can be taken in without adding a new circuit.
[0007]
[Means for Solving the Problems]
The invention of claim 1 includes a correcting means and reading means for converting an image of readings taken document to a digital signal, which based on the reference white sheet data read by said reading means, for correcting processing the digital signal read, The storage means for storing the peak value of the digital signal of the read image, and the reading means performs reading at a timing other than the reading of the reference white plate or the original image, and the obtained read data and the storage means stored in the storage means In an image reading apparatus having an abnormality detecting means for detecting an abnormality of a light source based on a peak value, the gate signal asserting area for sampling optical black pixel data of the reading means can be changed, and the reference white plate and the original When reading an image, the gate signal is asserted in the optical black pixel region, and the reference white plate and When other than reading the manuscript image is characterized by asserting the effective pixel region.
A second aspect of the present invention, in the image reading apparatus according to claim 1, characterized in that to detect the background level of the document during carriage return asserts the effective pixel area the gate signal.
A third aspect of the present invention, in the image reading apparatus according to claim 1, characterized in that to determine the level of the background plate asserts the gate signal in the effective pixel region during sheet-through DF mounted.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a typical reading device, and FIG. 2 is a partial view thereof, FIG. 2A is a plan view, and FIG. 2B is a partial sectional view. A pressure plate 18 having a document feeder (simply called DF) 10 is pivotally supported at one end of a document table 16 on the upper surface of the scanner body 14 so as to be freely opened and closed. The document table 16 includes a contact glass 16B, and is placed on the document D to be read. A carriage 28 having a lamp 24 is disposed below the contact glass 16, and when the document is placed stationary on the contact glass 16 </ b> B, the carriage 28 moves from its standby position toward the other end of the document table. The original is irradiated while moving, and the original is read. When the sheet-through type DF is used, the carriage 28 moves from the standby position to the lower side of the reading window and stops and moves at that position. The original D is irradiated and the original is read.
[0009]
FIG. 3 is a block diagram showing the structure of the image reading apparatus according to the present invention. The reading unit 30 is a CCD 32, an amplifier 34 for amplifying the output from the CCD 32, and an analog output signal from the amplifier 34 is converted to a digital signal. A / D converter 36 and a timing IC 38 for controlling the timing of the reading device are provided. The image processing unit 40 receives an output from the reading unit, detects a peak value of the output, a peak detection block 42, an image processing IC 44 that performs processing such as black offset processing, shading correction, gamma correction, and magnification conversion. A register (memory) 48 for storing the image processed data via the CPU 46 is provided.
At the time of reading a document, the light emitted from the light source (lamp) 24 is irradiated onto the document, and the reflected light is guided through a mirror to a reading lens (CCD) 26 provided at one end of the inside of the scanner body 14. It is converted into an electrical signal (image signal). This image signal is sent to the A / D converter 36 through an image processing circuit such as a sample hold and a signal amplifier, and is converted into a digital signal. The converted signal is subjected to processing such as black offset subtraction, shading correction, gamma correction, and scaling in the digital image processing unit, and is output as a read image. These series of operations are controlled by the CPU 46 having the reading unit 30, the image processing unit 40, and the I / F.
[0010]
(Embodiment 1)
FIG. 4 is a cross-sectional view of the main part of the reading apparatus when reading using a sheet-through type document feeder (DF).
A DF document feed roller 10A is provided in the vicinity of the opening / closing end of the pressure plate, and a reading window 12 for the document D is formed on the surface of the scanner body 14 facing the roller 10A. A carriage 28 is disposed below the document table, a reference white plate 20 is disposed below the end of the contact glass 16B along the movement path of the carriage 28, and a carriage home position sensor 40 is provided at the start end of the movement path. Is provided.
At the time of document reading, the carriage 28 moves from the standby position to the reference white plate 20 reading position, and then moves to the lower side of the collecting window 12 and stops. In this state, the carriage 28 is fed by the document feeding roll 10A of the DF 10. A document image is read. The reading apparatus has means for detecting a peak value for each main scanning line and updating this value for each line. In the update storage of the peak value, adjacent pixels are compared before performing shading correction on the data after AD conversion, the larger value is stored in the register (memory) 48, and the stored pixel data is stored. And the target pixel is compared and updated and stored only when the level of the target pixel is higher than the stored pixel. The register 48 is cleared (reset) by the line synchronization signal and updated for each line.
[0011]
The CPU that performs the reading control can monitor the state of the lamp 24 independently of the reading sequence by arbitrarily reading this register. For example, it can be controlled to read after the lamp lighting signal is turned on and after the time until light is actually emitted, or to read multiple times within the range allowed by the CPU during scanning.
In practice, it is difficult to read the register at the timing synchronized with the line sync signal, so read the register multiple times so that it does not coincide with the update timing of the register and judge the error based on the result, or read enable to the register It is necessary to devise such as reading after performing control and prohibiting writing update.
In this case, since the white plate area is not necessarily read out, it is necessary to consider the case where the level of the peak value is small. However, according to the present reading apparatus, the lamp is displayed when necessary regardless of the reading of the reference white plate. The condition can be monitored.
If the peak data does not reach the reference value even after a predetermined time has elapsed since the lamp is lit, the reading operation is stopped and an error is displayed.
[0012]
FIG. 5 shows a sequence explanatory diagram.
A line synchronization signal is generated for each main scanning line. The black pixel region signal generates a gate signal corresponding to the optical black pixel region between the line synchronization signals, and the effective pixel region signal similarly corresponds to the effective pixel region after the generation of the gate signal between the main scanning synchronization signals. A gate signal is generated.
Conventionally, a gate signal is generated corresponding to the optical black pixel (off-tick black) region of the CCD, and the level of the black pixel is determined by sampling and averaging the data in the assert region, and from the effective pixel data Image data is obtained by subtracting the level of the black pixel as an offset value. Since the position of the optical black pixel region may vary depending on the CCD, the gate signal is often configured to change the position.
In the conventional machine, the assert position is not changed during the reading operation in order to align the position with the CCD.
In contrast, in the present embodiment, as shown in FIG. 6, the assert position is changed to the original optical black pixel area or effective pixel area in accordance with whether the lamp is lit or not lit, either in hardware or software. .
The assertion (on state) start position, negate (off state) position, or assert area of this gate signal can be changed by setting it in the register (memory) 48, and this set value can be changed according to whether the lamp is lit or not lit. To change. As a result, the control described later, which was not performed in the conventional device, or whether there is a difference between the black level of the effective pixel and the level of the optical black pixel is evaluated, and if there is a difference, control is performed to correct it. Can be used in some cases.
[0013]
Since the lamp is naturally in the non-lighting state during the preheating / energy saving operation, the black pixel sampling gate is asserted in the effective pixel region as described above. At this time, since the lamp is not lit, the sampled value should not change. Nevertheless, when this sampling value changes, it is determined that the installation environment has changed, and the reader is returned from the standby state such as preheating and energy saving to the operating state. For example, when the pressure plate of the scanner is opened, it is conceivable that external light enters and the level of the effective pixel changes, so that it can be determined that the user is about to use the apparatus. Further, if the pressure plate is left open, it can be used for control such that there is no outside light at night, so that the standby state is maintained and the morning state is restored from the standby state.
[0014]
Specifically, the CPU 46 reads the sampled and averaged value stored in the register (memory 48) to detect the change in the value, or, in terms of hardware, a constant change to the sampled value. It is conceivable to provide a means for notifying the change by sending a command to the CPU 46 when there is, and thereby returning to the operating state.
[0015]
(Embodiment 2)
In the conventional machine, shading processing and image editing processing are performed using a gate signal in the sub-scanning direction indicating the reference white plate area and a gate signal in the sub-scanning direction indicating the document area.
In the first embodiment, the black pixel sampling gate position is changed in accordance with the lamp lighting signal. In the second embodiment, as shown in the sequence explanatory diagram of FIG. 7, the reference white plate area gate signal and the original area gate signal are used. The gate assert position is changed accordingly. In other words, the black offset needs to be subtracted to obtain image data only when generating shading data and reading the original (assuming that the black sampling gate is not used as the main scan synchronization reset signal as another application) However, at other timings, it is considered that there is no problem even if the position of the black pixel sampling gate is changed.
Therefore, in the area (B area) other than the reference white plate (A area) and the original area (A area), the assertion area is moved to the effective pixel area, for example, detection of the original background level at the carriage return, sheet through DF. It is possible to detect the level of the background plate (dirt, etc.) and to determine the change in the lamp light quantity at the time of mounting.
A means for performing this is easily obtained by changing the register value that determines the assert position of the sampling gate signal, as described in connection with the first embodiment when the respective region signals are negated. be able to.
[0016]
Next, means for detecting whether the lamp is lit will be described. For example, assume that a document is read with a sheet-through DF attached. At this time, if the lamp is lit except for the reference white plate and the original reading, the data on the background plate is sampled and it can be determined whether the lamp is lit. If it is less than or equal to the predetermined data, the error control process is performed as non-lighting. As another application, it is also possible to determine the dark start characteristic of the lamp by counting the number of lines until the value sampled from the lighting signal ON sufficiently changes.
As a result, not only the lamp is not turned on, but also the deterioration of the starting characteristics can be detected, and error control and maintenance announcement including the life can be performed to the user / serviceman.
[0017]
【The invention's effect】
According to the present invention, it has been conventionally determined whether the lamp is lit or not lit within a limited time during the reading operation, such as when reading a reference white plate. It is possible to determine lamp abnormality (error) that can obtain information and is not restricted by scanning control.
In addition, the shading and document reading areas in the reading sequence are not necessary for the black offset detection and the black offset removal in the other areas. Effective pixels can be monitored without preparing signals, processing and hardware for accurate detection.
[Brief description of the drawings]
FIG. 1 is a perspective view illustrating an entire image reading apparatus.
2A and 2B are partial views showing a main part of the image reading apparatus, in which FIG. 2A is a plan view and FIG. 2B is a partial cross-sectional view.
FIG. 3 is a block diagram for explaining the structure of the image reading apparatus.
FIG. 4 is a cross-sectional view of a main part showing an image reading unit using a sheet through DF of the image reading apparatus.
FIG. 5 is a sequence diagram of operation signals in the image reading apparatus.
FIG. 6 is another sequence diagram of operation signals in the image reading apparatus.
FIG. 7 is still another sequence diagram of operation signals in the image reading apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... DF, 12 ... Image reading window, 14 ... Image reading apparatus (scanner) main body, 16 ... Original plate, 16B ... Contact glass, 20 ... Standard white board, 26 ... Reading board, 30 ... reading unit, 32 ... CCD, 34 ... amplifier, 36 ... A / D converter, 38 ... timing IC, 40 ... image processing unit, 42. ..Peak detection block, 44... Image processing IC, 46... CPU, 48.

Claims (3)

Reading means for converting an image of the read document into a digital signal;
Based on the reference whiteboard data read by said reading means, and correcting means for correcting processing the digital signal read, a storage means for storing the peak value of the digital signal of an image read, the reference whiteboard or by the reading means reads at the timing other than the reading of the original image, in the image reading apparatus having, an abnormality detecting means for detecting the abnormality of the light source based on the peak value that is stored in the obtained read data said storage means,
A gate signal asserting area for sampling the optical black pixel data of the reading means can be changed, and when reading the reference white plate and the original image, the gate signal is asserted in the optical black pixel area, and the reference white board An image reading apparatus characterized by asserting in an effective pixel area when the document image is not read . The image reading apparatus according to claim 1,
An image reading apparatus characterized in that the gate signal is asserted in an effective pixel area and a background level of an original is detected at the time of carriage return . The image reading apparatus according to claim 1 ,
An image reading apparatus characterized in that the gate signal is asserted in an effective pixel area to determine a level of a background plate when a sheet through DF is mounted .

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