Image reader apparatus and method of driving the same
The present invention provides an image reader apparatus capable of obtaining an image having stable brightness while suppressing an increase of the cost of the apparatus. The image reader apparatus 1 for reading an image on a document 2 being fed and outputting an image signal includes a synchronization signal generation circuit 4 for generating a synchronization signal SS synchronous with a feed timing and a feed cycle of the document 2 , a CCD 6 for reading an image on the document 2 in synchronism with the synchronization signal SS, an LED 9 for emitting white light, and a lighting control circuit 7 for turning the LED 9 on in synchronism with the synchronization signal SS and turning the light source off so that a lighting period is equalized for each line irrespective of a variation of the feed cycle of the document 2. The lighting control circuit 7 turns the LED 9 off so that the lighting period of the LED 9 is equal to a predetermined preset period.
1. An image reader apparatus for reading an image on a document being fed and outputting an image signal, comprising:
a synchronization signal generator configured to generate a synchronization signal based upon a feed cycle signal outputted from a feeder device, the feed cycle signal representing a feed timing and a feed cycle of the document;
an image sensor configured to read the image on the document in synchronism with the synchronization signal;
a light source configured to emit light; and
a lighting controller configured to turn the light source on in synchronism with the synchronization signal and to turn the light source off so that a lighting period is equalized for each line irrespective of a variation of a cycle of the synchronization signal,
wherein the lighting controller is further configured to monitor the cycle of the synchronization signal, to subject the lighting period of the light source to a feedback control, and to maintain the lighting period to be shorter than the cycle of the synchronization signal even if the maximum variation is caused to a feed speed, and
wherein the lighting controller comprises a measurement part configured to take in the synchronization signal from the synchronization signal generator and a clock signal having a predetermined cycle and to count a number of clocks of the clock signal over one cycle of the synchronization signal.
2. The image reader apparatus as recited in claim 1 , wherein the lighting controller comprises a storage part configured to hold a preset value corresponding to the preset period, a comparator part configured to compare an output value of the measurement part with the preset value and to output a coincidence signal on the condition that the output value of the measurement part coincides with the preset value, and a turning-off signal output part configured to output a turning-off signal turning the light source off in accordance with the coincidence signal outputted from the comparator part.
3. The image reader apparatus as recited in claim 1 , wherein the image sensor is a one-dimension CCD sensor configured to read each line of an image on the document.
4. The image reader apparatus as recited in claim 1 , wherein the lighting controller is further configured to control the lighting period of the light source in response to a feedback signal by adjusting the lighting period in relation to the monitored cycle of the synchronization signal.
5. The image reader apparatus as recited in claim 1 , wherein the preset period is set to be shorter than the shortest feed cycle determined by a characteristic of a feed mechanism for feeding the document.
6. A method of driving an image reader apparatus comprising a light source arranged so as to emit light to a document and an image sensor converting contrast between light and shade of an image on the document into an image signal, the method comprising:
generating a synchronization signal based upon a feed cycle signal output from a feeder device, the feed cycle signal representing a feed timing and a feed cycle of the document;
activating a reading operation of the image sensor in synchronism with the synchronization signal;
turning the light source on in synchronism with the synchronization signal and turning the light source off so that a lighting period is equalized for each line irrespective of a variation of a cycle of the synchronization signal; and
monitoring the cycle of the synchronization signal of the light source, subjecting the lighting period of the light source to a feedback control, and maintaining the lighting period to be shorter than the cycle of the synchronization signal even if the maximum variation is caused to a feed speed; and
taking in the synchronization signal from the synchronization signal generator and a clock signal having a predetermined cycle and counting a number of clocks of the clock signal over one cycle of the synchronization signal.
7. The method of driving an image reader apparatus as recited in claim 6 , wherein the image sensor is a one-dimension CCD sensor reading each line of an image on the document.
8. The method of driving an image reader apparatus as recited in claim 6 , the method further comprising:
controlling the lighting period of the light source in response to a feedback signal by adjusting the lighting period in relation to the monitored cycle of the synchronization signal.
9. The method of driving an image reader apparatus as recited in claim 6 , wherein the preset period is set to be shorter than the shortest feed cycle determined by a characteristic of a feed mechanism for feeding the document.
10. A scanner comprising a feeder device configured to feed a document and an image reader apparatus configured to read an image on the document being fed and outputting an image signal, wherein the image reader apparatus comprises:
a synchronization signal generator configured to generate a synchronization signal based upon a feed cycle signal output from a feeder device, the feed cycle signal representing a feed timing and a feed cycle of the document;
an image sensor configured to read the image on the document in synchronism with the synchronization signal;
a light source configured to emit light; and
a lighting controller configured to turn the light source on in synchronism with the synchronization signal and to turn the light source off so that a lighting period is equalized for each line irrespective of a variation of a cycle of the synchronization signal,
wherein the lighting controller is further configured to monitor the cycle of the synchronization signal, to subject the lighting period of the light source to a feedback control, and to maintain the lighting period to be shorter than the cycle of the synchronization signal even if the maximum variation is caused to a feed speed; and
wherein the lighting controller comprises a measurement part configured to take in the synchronization signal from the synchronization signal generator and a clock signal having a predetermined cycle and to count a number of clocks of the clock signal over one cycle of the synchronization signal.
11. The scanner as recited in claim 10 , wherein the lighting controller is further configured to control the lighting period of the light source in response to a feedback signal by adjusting the lighting period in relation to the monitored cycle of the synchronization signal.
12. A printer comprising a feeder device configured to feed a document and an image reader apparatus configured to read an image on the document being fed and outputting an image signal, wherein the image reader apparatus comprises:
a synchronization signal generator configured to generate a synchronization signal based upon a feed cycle signal output from a feeder device, the feed cycle signal representing a feed timing and a feed cycle of the document;
an image sensor configured to read the image on the document in synchronism with the synchronization signal;
a light source configured to emit light; and
a lighting controller configured to turn the light source on in synchronism with the synchronization signal and to turn the light source off so that a lighting period is equalized for each line irrespective of a variation of a cycle of the synchronization signal,
wherein the lighting controller is further configured to monitor the cycle of the synchronization signal, to subject the lighting period of the light source to a feedback control, and to maintain the lighting period to be shorter than the cycle of the synchronization signal even if the maximum variation is caused to a feed speed; and
wherein the lighting controller comprises a measurement part configured to take in the synchronization signal from the synchronization signal generator and a clock signal having a predetermined cycle and to count a number of clocks of the clock signal over one cycle of the synchronization signal.
13. The printer as recited in claim 12 , wherein the lighting controller is further configured to control the lighting period of the light source in response to a feedback signal by adjusting the lighting period in relation to the monitored cycle of the synchronization signal.
14. A facsimile machine comprising a feeder device configured to feed a document and an image reader apparatus configure to read an image on the document being fed and outputting an image signal, wherein the image reader apparatus comprises:
a synchronization signal generator configured to generate a synchronization signal based upon a feed cycle signal output from a feeder device, the feed cycle signal representing a feed timing and a feed cycle of the document;
an image sensor configured to read the image on the document in synchronism with the synchronization signal;
a light source configured to emit light; and
a lighting controller configured to turn the light source on in synchronism with the synchronization signal and to turn the light source off so that a lighting period is equalized for each line irrespective of a variation of a cycle of the synchronization signal,
wherein the lighting controller is further configured to monitor the cycle of the synchronization signal, to subject the lighting period of the light source to a feedback control, and to maintain the lighting period to be shorter than the cycle of the synchronization signal even if the maximum variation is caused to a feed speed; and
wherein the lighting controller comprises a measurement part configured to take in the synchronization signal from the synchronization signal generator and a clock signal having a predetermined cycle and to count a number of clocks of the clock signal over one cycle of the synchronization signal.
15. The facsimile machine as recited in claim 14 , wherein the lighting controller is further configured to control the lighting period of the light source in response to a feedback signal by adjusting the lighting period in relation to the monitored cycle of the synchronization signal.