Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
1999-11-24
2002-05-14
Frech, Karl D. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S462180, C235S462240, C235S462060
Reexamination Certificate
active
06386452
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image reading device, and in particular, to an image reading device which reads an original document or image by using a light source which illuminates the original and a light sensor which receives light from the original.
2. Description of the Related Art
There have been proposed various conventional devices in which a plurality of different types of color light are emitted from plural LEDs so as to illuminate an original, and the light reflected from the original is received, as light of a plurality of different wavelengths, by a CCD sensor. For example, Japanese Patent Application Laid-Open (JP-A) No. 10-32681 discloses a reading device in which d plurality of different color lights are successively emitted so as to illuminate an object to be copied, and the light reflected from the object to be copied is read synchronously with the emission of the respective color lights. Further, Japanese Patent Application Laid-Open (JP-A) No. 7-6197 discloses a device in which a bar code is illuminated by light emitted from respective LEDs of an LED array, the light reflected from the bar code is read at a CCD line sensor, and on the basis of the amounts of light received by the respective CCDs, the duties of the period of time that light is emitted from the respective LEDs corresponding to the CCDs are set such that the bar code is illuminated at a uniform and constant amount of light.
In devices such as those described above, in order for the CCD sensor to receive a desired amount of light, the charge accumulating times of the CCD sensor (times at which the CCD sensor can receive light, i.e., light receivable times) must be varied with the plural LEDs always emitting light, or the light emitting times of the plural LEDs must be controlled with the charge accumulating times of the CCDs fixed.
If a method is used in which only one of the charge accumulating times of the CCD sensor or the light emitting times of the LEDs are controlled, not only are there fewer degrees of freedom of control, but also, fine control cannot be effected.
SUMMARY OF THE INVENTION
The present invention was achieved in light of the aforementioned, an object thereof is to provide an image reading device in which the degrees of freedom of control at the time of reading are increased.
In order to achieve the above object, a first aspect of the present invention is an image reading device comprising: a light source which illuminates an original and which is formed by a plurality of light emitting elements which emit light of different wavelengths; one or more light sensors which receive light from the original and which are formed by a plurality of light receiving elements which receive light from the light source; and control means for controlling the light sensors by using a predetermined minimum charge accumulating time as a unit such that the light sensors receive light from the original during a light receivable time which is an integer multiple of the minimum charge accumulating time, and for controlling the respective light emitting elements such that the respective light emitting elements are pulse width modulated synchronously with the light receivable time and such that one period thereof equals the minimum charge accumulating time, and emit light. Light from the light source means both light transmitted through (passing through) the original and light reflected by the original.
In the light source relating to the present invention, a plurality of light emitting elements, which emit light of different wavelengths, are provided in a row, and the light source illuminates the original. In the plural light sensors, plural light receiving elements, which receive light of different wavelengths, are provided in a row, and the plural light sensors receive light from the original.
The control means controls the respective light sensors by using a predetermined minimum charge accumulating time as a unit such that the respective light sensors receive light during a light receivable time which is an integer multiple of the minimum charge accumulating time. The control means controls the respective light emitting elements such that the respective light emitting elements are pulse width modulated synchronously with the light receivable time and such that one period thereof equals the minimum charge accumulating time, and emit light.
By using the predetermined minimum charge accumulating time as a unit, the light sensors receive light from the original during a light receivable time which is an integer multiple of the minimum charge accumulating time. The respective light emitting elements are pulse width modulated synchronously with the light receivable time and such that one period thereof equals the minimum charge accumulating time, and emit light. Thus, the number of degrees of freedom in control at the time of reading can be increased, and fine control can be carried out.
On the basis of output from the plurality of light sensors in a state in which there is no original in a case in which transmitted light from the original is to be read, and on the basis of output from the plurality of light sensors when a reference plate of a predetermined color is set instead of the original in a case in which light reflected from the original is to be read, the control means may compute a target value of at least one of a light receivable time of each of the plurality of light sensors and a light emitting pulse width of each of the plurality of light emitting elements, such that color balance and light distribution of each of the plurality of light emitting elements fall within allowable ranges, and the control means may effect control such that the at least one of the light receivable time of each of the plurality of light sensors and the light emitting pulse width of each of the plurality of light emitting elements becomes the computed target value.
In this way, the control means computes a target value of at least one of a light receivable time of each of the plurality of light sensors and a light emitting pulse width of each of the plurality of light emitting elements, such that color balance and light distribution of each of the plurality of light emitting elements fall within allowable ranges, and the control means effects control such that the at least one of the light receivable time of each of the plurality of light sensors and the light emitting pulse width of each of the plurality of light emitting elements becomes the computed target value. Thus, light of a color balance and light distribution which fall within allowable ranges can be illuminated onto the original.
The control means may control the light receivable time of each of the plurality of light sensors and the light emitting pulse width of each of the plurality of light emitting elements, such that the amount of light received from the original by each of the plurality of light sensors becomes a desired amount of light received.
The control means computes a target value of at least one of the driving current of each of the plurality of light emitting elements, the light receivable time of each of the plurality of light sensors and the light emitting pulse width of each of the plurality of light emitting elements, such that color balance and light distribution of each of the plurality of light emitting elements fall within allowable ranges, and the control means effects control such that the at least one of the driving current of each of the plurality of light emitting elements, the light receivable time of each of the plurality of light sensors and the light emitting pulse width of each of the plurality of light emitting elements becomes the computed target value. Thus, the number of degrees of freedom in control at the time of reading can be increased even more, and even more fine control can be carried out.
The control means may control the light receivable time of each of the plurality of light sensors, the light emitting pulse width of each of the plurality of li
Frech Karl D.
Fuji Photo Film Co. , Ltd.
Walsh Daniel
LandOfFree
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