Image analysis – Image transformation or preprocessing – Measuring image properties
Reexamination Certificate
2001-09-12
2004-04-06
Couso, Yon J. (Department: 2625)
Image analysis
Image transformation or preprocessing
Measuring image properties
C358S001500, C358S001900
Reexamination Certificate
active
06718071
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image reading apparatus and method suitable for use in the correction of skew error of a medium.
2. Description of the Related Art
In recent years, an image reading apparatus has been developed that allows documents of multiple sizes to be read. For this purpose, the image reading apparatus is provided with detection means for detecting the size of documents.
Operation of the conventional image reading apparatus will be described below with reference to a flow chart of
FIGS. 4A and 4B
, and an explanatory view of a sensor unit of FIG.
5
. The sensors shown in
FIG. 5
are sensors of a transmission type, and a skew angle is detected with sensors SB
4
, SB
5
, SF
1
, SA
4
, and SA
3
.
Before starting the reading of documents, an operator first sets the size of the document (S1). Then, at the start of reading, the rotation of a conveyance motor for driving a conveyance roller or the like is started (S2). When a predetermined time, for example 50 msec, has elapsed after the start of the rotation of the conveyance motor, a first clutch and a second clutch are switched on to start driving the conveyance roller (S4).
When the first document is picked, it is determined whether or not any of a plurality of size sensors (4 sensors in the example shown) has been turned, that is, whether a document has been detected or not (S5). If it is determined at step S5 that no document has been detected by the size sensors, it is determined whether SF
1
has detected a document or not(S6). If, at step S6, it is determined that no document has been detected by SF
1
, it is determined at step S7 whether a certain time (2 seconds in this example) has elapsed after the start of picking of documents or not. If, at step S7, it is determined that the 2 seconds have not elapsed, picking of documents is retried at a shorter interval (in units of 0.5 second in this example) at step S8. On the other hand, if it is determined, at step S7, that the 2 seconds have elapsed, judging that the document has not been conveyed normally, pick error processing is performed (S9). Then, the conveyance motor is stopped (S10), and the operator confirms the existance of the document again, and repeats the pick operation.
On the other hand, if, at step S6, it is determined that a document has been detected by SF
1
, and judging that some trouble has occurred because no document has been detected by any of size sensors at step S5, pick error processing is performed at step S9. Then, at step S10, the conveyance motor is stopped.
If, at step S5, it is determined that any of the size sensors has detected the document, and judging that picking of the document has been normally completed, the name of the size sensor that was first turned on is stored in a memory (S11), and counting of the pulses of the conveyance motor after the size sensor detected the document is started (S12). Next, the present state of the sensor is stored in the memory (S13). At step S14, it is determined whether a size sensor for a size exceeding the set document size is ON or OFF. If it is determined to be ON, the process moves to step S15. If it is determined to be OFF, the process moves to step S17.
At step S15, the skew error correction processing is performed. That is, at step S16, the conveyance motor is stopped, and then the pick operation is repeated. At step S17, it is determined whether or not SF
1
has detected the document. If, at step S17, it is determined that SF
1
has not detected the document, it is checked, at step S18, whether or not the count of pulses has exceeded a specified number of pulses. Since necessary number of pulses after the size sensor detects the document until SF
1
detects the same document, when the document is conveyed normally, is known beforehand, it can be determined whether the document has been conveyed normally or not by counting the pulses after the size sensor detects the document until SF
1
detects the same document and by comparing the number of counted pulses with the specified number.
If the counted number exceeds the specified number, and judging that the document has not been conveyed, jam error processing is performed (S19). That is, the conveyance motor is stopped at step S20, and then the pick operation is repeated. On the other hand, if, at step S18, the counted number does not exceed the specified number of pulses, the process returns to step S13.
On the other hand, at step S17, if SF
1
has detected the document, the first clutch is turned off and driving of the pick roller is stopped (S21). Then, calculation of skew (skew angle) is performed (S22). At step S23, it is determined whether or not an abnormal deviation (skew angle of 10° or more) has occurred. If it is determined that abnormal deviation has occurred, the process moves to step S15. If it is determined that abnormal deviation has not occurred, the process moves to step S24. Then, the pulses of the conveyance motor after SF
1
detected the document are counted (S24). Thereafter, it is determined whether the surface reading timing sensor SF
2
has detected the document or not (S25).
If, at step S25, it is determined that SF
2
has detected the document, the second clutch is turned off and pick operation for the next document is performed at S26. On the other hand, if, at step S25, it is determined that SF
2
has not detected the document, it is determined at step S27 whether or not the counted number of pulses has exceeded the specified number of pulses. If the counted number has exceeded the specified number of pulses, jam error processing is performed (S19). If the counted number has not exceeded the specified number of pulses, the process returns to step S25, where it is again determined whether or not SF
2
has detected the document.
Here, in the case of an image reading apparatus, the skew of the conveyed medium manifests itself as tilting of the read image. Therefore, the occurrence of skew error has been conventionally detected based on the degree of tilting of read image.
FIG. 6
is a view useful for explaining the conventional method of skew detection. In this figure, the portion enclosed by dotted line shows the state of a document read when no skew has occurred, as seen on a display. The portion enclosed by solid line shows the state of the document read when skew has occurred, as seen on a display.
In the figure, A shows the amount of skew in the main scanning direction, and corresponds to the difference between left end and right end of the leading edge of the document. B shows the amount of skew in the subscanning direction, and, in this figure, corresponds to the difference of the leading edge and the trailing edge of the document.
In this detection method, the proportion of the values A and B shown in
FIG. 6
, in relation to the length of sheet in the main scanning direction and in the subscanning direction respectively, was determined, and if A/B was 1% or less of the length of sheet in the main-/sub-scanning direction, respectively, the document was regarded as normal, and if A/B was beyond this range, the document was determined to be abnormal.
However, with this detection method, an operator had to identify the difference in both main- and sub-scanning directions on the display. Thus, for each document read, an operator had to identify on the display whether skew error has occurred or not, and this put a heavy burden on the operator.
Further, in recent years, the operation speed of a document reading apparatus has become increasingly higher so that it has become more and more difficult for an operator to confirm whether skew error has occurred or not for each document. Even if occurrence of skew error is identified, there is another problem that it is very difficult to perform proper skew error correction processing corresponding to the skew error rapidly.
When amount of skew error is calculated from the read image, the document usually has a white background, and the images or the characters are colored in most cases. Thus, in ord
Amagai Tamio
Kimura Takeshi
Maruyama Hiroyuki
Yamazaki Noriaki
Yoshida Mitsuhiro
Couso Yon J.
PFU Limited
Westerman Hattori Daniels & Adrian LLP
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