1. An image reading apparatus comprising:
at least three line sensors having filters, respectively, different in spectral sensitivity, and arranged in a predetermined order in a subscanning direction with a distance therebetween to scan an original in the subscanning direction;
a platen arranged between the original and said at least three line sensors;
a mover moving said platen at a rate relative to said at least three line sensors, said rate being different from that of the original relative to said at least three line sensors;
an interline corrector receiving at least three data from said at least three line sensors to synchronize said at least three data to be a pixel having read a single location on the original; and
a noise pixel detector receiving said at least three data synchronized by said interline corrector, one line at a time, sequentially, said noise pixel detector including
an extractor extracting a feature pixel from each of said at least three data, said feature pixel having a predetermined feature,
a detector comparing said at least three data corresponding to a single location on the original to detect said feature pixel extracted from one of said at least three data, as a noise pixel if said feature pixel is not a feature pixel for each of said at least three data other than said one of said at least three data,
a color determiner determining a color of each pixel from said at least three data,
a determiner depending on a color of a pixel neighboring a pixel to be processed selected from pixels arranged in the main scanning direction, to determine among said at least three data first data from which a noise pixel is initially detected, and
a noise pixel determiner invalidating a noise pixel detected by said detector identical in location in the main scanning direction to said pixel to be processed, that is included in a line input prior to a line including said noise pixel detected from said first data and that is detected from data other than said first data.
2. The image reading apparatus of claim 1, wherein said determiner also depends on a direction of movement of said platen relative to said at least three line sensors to determine said first data.
3. The image reading apparatus of claim 1, wherein said determiner determines said first data whenever said direction of movement of said platen varies.
4. The image reading apparatus of claim 1, wherein:
said extractor includes a first extractor extracting from each of a plurality of data output from said at least three line sensors a first feature pixel having a predetermined feature of a first level, and a second extractor extracting from each of said plurality of data a second feature pixel having said predetermined feature of a second level; and
said detector compares said plurality of data corresponding to a single location on the original to detect a first feature pixel extracted from one of said plurality of data, as a noise pixel if a second feature pixel is also not extracted from each of said plurality of data other than said one of said plurality of data.
5. The image reading apparatus of claim 4, wherein said first level is higher than said second level.
6. The image reading apparatus of claim 4, wherein:
said first extractor includes a first edge extractor employing a first filter to extract an edge region and extracts as said first feature pixel a pixel included in an edge region extracted by said first edge extractor; and
said second extractor includes a second edge extractor employing a second filter lower in edge detection characteristic than said first filter to extract an edge region, and extracts as said second feature pixel a pixel included in an edge region extracted by said second edge extractor.
7. The image reading apparatus of claim 6, wherein said edge extractor has a plurality of types of filters corresponding to sizes of regions to output a location of a center pixel of an extracted region and a size of said region.
8. The image reading apparatus of claim 4, wherein:
said first extractor includes a first region extractor extracting a region having a limited variation in lightness and a difference from a neighboring region in lightness of at least a first threshold value, and extracts said extracted region as said first feature pixel; and
said second extractor includes a second region extractor extracting a region having a limited variation in lightness and a difference from a neighboring region in lightness of at least a second threshold value smaller than said first threshold value, and extracts said extracted region as said second feature pixel.
9. The image reading apparatus of claim 8, wherein said second extractor further includes an extender setting as a second feature pixel a pixel neighboring said second feature pixel extracted.
10. The image reading apparatus of claim 1, wherein said noise pixel determiner validates a noise pixel when said neighboring pixel varies in color.
11. The image reading apparatus of claim 1, further comprising an original transporter transporting the original while said at least three line sensors scan the original.
12. The image reading apparatus of claim 1, wherein said at least three sensors each include a filter different in spectral sensitivity to receive light reflected from the original through said filter.
13. The image reading apparatus of claim 1, further comprising a determiner depending on a variation in color from first through to second noise pixels identically located in a main scanning direction and spaced in the sub scanning direction to determine all of said first through to second noise pixels as noise pixels.
14. An image reading apparatus comprising:
at least three line sensors having filters, respectively, different in spectral sensitivity, and arranged in a predetermined order in a subscanning direction with a distance therebetween to scan an original in the subscanning direction;
a platen arranged between the original and said at least three line sensors;
a mover moving said platen at a rate relative to said at least three line sensors, said rate being different from that of the original relative to said at least three line sensors;
an interline corrector receiving at least three data from said at least three line sensors to synchronize said at least three data to be a pixel having read a single location on the original; and
a noise pixel detector receiving said at least three data synchronized by said interline corrector, one line at a time, sequentially, said noise pixel detector including
an extractor extracting a feature pixel from each of said at least three data, said feature pixel having a predetermined feature,
a detector comparing said at least three data corresponding to a single location on the original to detect said feature pixel extracted from one of said at least three data, as a noise pixel if said feature pixel is not a feature pixel for each of said at least three data other than said one of said at least three data,
a color determiner determining a color of each pixel from said at least three data,
an order determiner depending on a color of a pixel neighboring a pixel to be processed selected from pixels arranged in the main scanning direction, to determine an order of said at least three data in which a noise pixel is detected, and
a noise pixel determiner invalidating a noise pixel detected by said detector identical in location in the main scanning direction to said pixel to be processed, that is included in a line input prior to a line including first data for which a decision is made that a noise pixel is initially detected and that is detected from second data for which a decision is made that a noise pixel is subsequently detected.
15. The image reading apparatus of claim 14, wherein said order determiner also depends on a direction of movement of said platen relative to said at least three line sensors to determine said order.
16. The image reading apparatus of claim 14, wherein said order determiner determines said order whenever said direction of movement of said platen varies.
17. The image reading apparatus of claim 14, wherein said noise pixel determiner validates a noise pixel when said neighboring pixel varies in color.
18. The image reading apparatus of claim 14, further comprising an original transporter transporting the original while said at least three line sensors scan the original.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A control apparatus which suppresses natural vibration of a controlled object including an electric motor and a machine driven by said electric motor while controlling said controlled object, said control apparatus comprising:
a control unit outputting a control signal controlling said electric motor;
a frequency analysis unit analyzing a frequency included in said control signal;
an analysis control unit controlling the start or stopping of said frequency analysis unit;
a detection unit detecting a natural frequency of said controlled object from an analysis result of said frequency analysis unit;
a band rejection filter receiving as input said control signal, stripping said control signal of said natural frequency component, and outputting the resultant control signal to said electric motor; and,
a filter characteristic setting unit setting the frequency to be stripped at said band rejection filter based on said natural frequency detected by said detection unit.
2. The control apparatus as set forth in claim 1, wherein
said control signal is a speed command or torque command, and
said analysis control unit controls said frequency analysis unit based on the value of said speed command or said torque command.
3. The control apparatus as set forth in claim 1, wherein
said apparatus comprises a higher control apparatus controlling said control unit and said analysis control unit, and
said analysis control unit makes said frequency analysis unit analyze the frequency when said higher control apparatus outputs a start command to said analysis control unit.
4. The control apparatus as set forth in claim 1, further comprising
a natural vibration generation unit adding said natural frequency component to said control signal.
5. The control apparatus as set forth in claim 1, wherein
said detection unit detects said natural frequency from a predetermined range of frequency in said analysis result.
6. The control apparatus as set forth in claim 1, wherein
said detection unit detects a frequency with a magnitude of a frequency component of a predetermined threshold value or more from said analysis result as said natural frequency and changes said predetermined threshold value based on said natural frequency.
7. The control apparatus as set forth in claim 1, wherein
said apparatus comprises a control signal limiting unit limiting the magnitude of said control signal, and,
said control signal limiting unit limits the magnitude of said control signal for a predetermined time after said filter characteristic setting unit sets said frequency stripped by said band rejection filter.
8. The control apparatus as set forth in claim 1, wherein
said filter characteristic setting unit changes the amount of attenuation of said band rejection filter based on the natural frequency detected by said detection unit.
9. The control apparatus as set forth in claim 1, wherein
said filter characteristic setting unit changes the bandwidth of the frequency stripped by said band rejection filter based on the natural frequency detected by said detection unit.
10. The control apparatus as set forth in claim 1, wherein
said frequency analysis unit comprises a sampling unit sampling said control signal at predetermined intervals, a storage unit storing said sampled control signal, and a processing unit applying a discrete Fourier transform to said control signal to compute the frequency component, and
said control apparatus comprises a sampling interval changing unit changing said predetermined interval by which said sampling unit samples the signals.