Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
2000-10-02
2001-12-11
Phan, James (Department: 2872)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C358S481000, C358S496000
Reexamination Certificate
active
06330096
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light-beam scanning type image reader, and more particularly to an improvement in the method of adjusting lengths across which a scan body is scanned or read.
2. Description of the Related Art
A light-beam scanning type image reader is known in which an image signal is obtained by scanning a light beam on a scan body recorded with an image and photoelectrically reading luminescent light emitted according to the recorded image.
As the light-beam scanning type image reader, a radiation image recording-reproducing system and an autoradiographic system have been proposed and already been put to practical use by the applicant of this application. These systems take advantage of the photostimulated luminescence (PSL) of a storage-type phosphor (stimulatable phosphor) in which the phosphor is irradiated with radiation (X-rays, &agr;-rays, &bgr;-rays, &ggr;-rays, electron rays, ultraviolet rays, etc.) and emits luminescent light according to the stored radiation energy when irradiated with excitation light such as visible light, etc. That is, by irradiating a radiation image, transmitted through a human body, etc., to a storage-type fluorescent sheet, or by exposing the tissue of a living organism, containing a drug labeled with a radioactive substance, to direct contact with the storage-type fluorescent sheet only for a predetermined time, the radiation image, such as the transmitted radiation image, the directly exposed image, etc., is temporarily stored and recorded on the storage-type fluorescent sheet. Then, excitation light, such as laser light, etc., is scanned on the storage-type fluorescent sheet to obtain photostimulated fluorescent light according to the radiation image, stored and recorded on the sheet. The obtained photostimulated fluorescent light is converted to an electrical image signal. Based on the image signal, the radiation image is output as a visible image to a recording material such as a photosensitive material, etc., or to a cathode-ray tube (CRT) display unit, etc.
In these light-beam scanning type readers, a light beam, reflected and deflected by a rotating polygon mirror, is scanned on a scan body in a horizontal scanning direction, and at least either the light beam or the scan body is scanned in a vertical scanning direction approximately perpendicular to the horizontal scanning direction. Through a combination of the horizontal scan and the vertical scan, the light beam is uniformly scanned on the scan body.
In the case where an image signal is read out from a scan body by the above-mentioned image reader, incidentally, image signals must be obtained at a fixed number of pixels from a scan body, if the scan body has a fixed form.
However, there are cases where fabricated image readers have a different number of pixels because of the cumulation of allowable fabrication errors, etc., of each component of the optical system, electrical system, mechanical system, etc., which constitute the image reader. Because of this, image signals cannot be always obtained at a fixed number of pixels from a fixed form of scan body. In addition, there are instances where a desired number of pixels vary with each user of the image reader. Thus, it is desired that these cases are flexibly handled.
SUMMARY OF THE INVENTION
The present invention has been made in view of the aforementioned circumstances. Accordingly, it is the primary object of the present invention to provide a light-beam scanning type image reader that is capable of readily adjusting the number of pixels which can be obtained from a scan body.
The light-beam scanning type image reader of the present invention employs a predetermined scan body (calibration sheet) to obtain the number of pixels in a horizontal scanning direction and the number of pixels in a vertical scanning direction, and adjusts either the number of drive-clock pulses for a rotating polygon mirror or the number of A/D sampling clock pulses so that the obtained number of horizontal pixels becomes equal to a desired number of horizontal pixels, and also adjusts the number of vertical scanning clock pulses for vertical scanning means so that the obtained number of vertical pixels becomes equal to a desired number of vertical pixels.
That is, a first light-beam scanning type image reader of the present invention comprises:
light-beam generation means for generating a light beam;
first clock generation means for generating a first clock pulse;
second clock generation means for generating a second clock pulse;
a rotating polygon mirror, which rotates at a speed of rotation based on the first clock pulse generated by the first clock generation means, for reflecting and deflecting the light beam so that the light beam is repeatedly scanned on a scan body in a horizontal scanning direction;
vertical scanning means for scanning at least either one of the light beam or the scan body with respect to the other in a vertical scanning direction approximately perpendicular to the horizontal scanning direction at a speed based on the second clock pulse generated by the second clock generation means;
photoelectric detection means for photoelectrically detecting in sequence luminescent light emitted from the scan body by scanning the light beam on the scan body;
sampling-clock generation means for generating a fixed analog-to-digital (A/D) sampling clock pulse;
analog-to-digital conversion means for converting analog signals, detected and obtained by the photoelectric detection means, to digital signals according to the A/D sampling clock pulse generated by the sampling-clock generation means;
clock-cycle computation means for computing a cycle of the first clock pulse so that a number of the digital signals, obtained according to a horizontal length of a predetermined scan body, becomes equal to a first desired number of pixels, and for computing a cycle of the second clock pulse so that a number of the digital signals, obtained according to a vertical length of the predetermined scan body, becomes equal to a second desired number of pixels;
clock-cycle storage means for storing the cycle of the first clock pulse and the cycle of the second clock pulse computed by the clock-cycle computation means; and
drive-clock control means for adjusting a cycle of the first clock pulse and a cycle of the second clock pulse, based on the cycle of the first clock pulse and the cycle of the second clock pulse stored in the clock-cycle storage means.
The predetermined scan body is, for example, a scan body of the same size as a scan body from which an image is read out, and can employ a test scan body to which radiation is uniformly irradiated, etc. The size of the predetermined scan body does not need to be exactly the same as the size of a scan body from which an image is read out. When the size ratio between the predetermined scan body and a scan body from which an image is read out is known, each clock pulse for a scan body from which an image is read out can be easily adjusted. Such a predetermined scan body does not necessarily need to be uniformly irradiated with radiation, and is sufficient if the lengths in the horizontal and vertical scanning directions can be computed based on an image signal read out. For example, it may be a scan body wherein only the circumferential edge portion is colored with high density so that a photoelectrically detected image signal can change sharply. This explanation for the predetermined scan body applies to the following description.
In a preferred form of the first light-beam scanning type image reader of the present invention, the first clock generation means is equipped with first reference-clock generation means for generating a first reference clock pulse which is higher in frequency than the first clock pulse, and a first frequency-dividing circuit, which has a variable frequency-dividing ratio, for dividing frequency of the first reference clock pulse so that the frequency of the first reference clock pulse becomes equal to the frequency
Fuji Photo Film Co. , Ltd.
Phan James
Sughrue Mion Zinn Macpeak & Seas, PLLC
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