JPH04350620A - Light beam scanning device - Google Patents

Abstract

PURPOSE:To scan a large-sized body such as an industrial fluorescent material sheet with a light beam although the size of the light beam scanning device is small by arranging an optical deflector and the scanned body so that the length of the optical path from the optical deflector to the scanned body is different between both main-scanning ends of the scanned body. CONSTITUTION:An accumulative fluorescent sheet A which is conveyed in a subscanning direction crossing exciting light L, deflected in a main-scanning direction shown by an arrow (a), at right angles is irradiated with the exciting light L to generate stimulated luminous flux corresponding to the image information recorded on the sheet A, and the stimulated fluorescent light is measured, processed, and read. In this case, the optical path length of the exciting light L from a galvanometer mirror 14 to the sheet A is made different between both end parts of the sheet A in the main scanning direction. Consequently, the scanning angle of the beam to the sheet A by the optical deflector is made small and the dead space from the optical deflector to the scanned body is reduced to realize size reduction.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light beam scanning device applied to image reading devices, image recording devices, etc. Specifically, the present invention relates to a light beam scanning device that is small in size yet capable of scanning a large-sized object with a light beam.

0002

[Prior Art] Certain types of phosphors are exposed to radiation (X-rays, α-rays,
When the phosphor is irradiated with β-rays, γ-rays, electron beams, ultraviolet rays, etc., it accumulates some of this radiation energy, and then when this phosphor is irradiated with excitation light such as visible light, the accumulated energy is It is known that it exhibits stimulated luminescence depending on the
A phosphor exhibiting such properties is called a stimulable phosphor (stimulable phosphor).

By using this stimulable phosphor, radiation image information of objects such as human bodies and buildings can be stored on a sheet having a layer of stimulable phosphor (hereinafter referred to as stimulable phosphor sheet).
This phosphor sheet is scanned two-dimensionally with excitation light such as a laser beam to generate stimulated luminescent light, and this stimulated luminescent light is read photoelectrically to generate an image signal. The present applicant has proposed a radiation image information recording and reproducing system that outputs the radiation image of the subject as a visible image to a recording material such as a photographic light-sensitive material or a display device such as a CRT based on this image signal ( Japanese Patent Publication No. 55-12429
No. 56-11395, etc.).

Similar to radiographs such as X-rays, such radiographic image information recording and reproducing systems are used not only for medical purposes such as medical diagnosis and inspection, but also in recent years for non-destructive inspection of buildings, aircraft, etc. It is also suitably applied to industrial applications.

In such a radiation image information recording and reproducing system, image recording on the phosphor sheet is performed by irradiating the phosphor sheet with radiation that has passed through an object such as a human body or a building. On the other hand, reading of the radiation image information stored and recorded on the phosphor sheet in this manner is carried out in the following manner by a radiation image information reading device applying a so-called light beam scanning device.

[0006] A light beam scanning device is a light beam scanning device that two-dimensionally scans an object to be scanned, which is conveyed in a sub-scanning direction substantially orthogonal to the main-scanning direction, with a light beam deflected in a main-scanning direction. This is a device that irradiates (scans) the entire surface of an object to be scanned. In order to read a phosphor sheet in the radiation image information reading device described above, the light beam scanning device conveys the phosphor sheet carrying radiation image information in the sub-scanning direction and uses excitation light ( By scanning this phosphor sheet with a light beam), the radiation image information accumulated and recorded on the phosphor sheet is read.

Specifically, excitation light of a constant intensity emitted from an excitation light source such as a He-Ne laser is reflected and deflected in the main scanning direction by an optical deflector such as a galvanometer mirror, and is reflected and deflected in the main scanning direction by an optical deflector such as a galvanometer mirror. The phosphor sheet is irradiated through the optical element.

[0008] Here, the phosphor sheet is conveyed on a belt conveyor,
The paper is transported by a transport device such as a nip roller in a sub-scanning direction that is substantially perpendicular to the previous main-scanning direction. Therefore, the excitation light deflected in the main scanning direction can two-dimensionally scan the entire surface of this phosphor sheet.

[0009] Stimulated luminescence light corresponding to the radiographic image information accumulated and recorded there is generated from the part of the phosphor sheet that is irradiated with the excitation light. This stimulated luminescence light is directly incident on the incident surface of the light guide, or is reflected by a condensing mirror disposed opposite to this incident surface, enters the incident surface of the light guide, is transmitted by the light guide, and is excited. After passing through a filter that cuts light in the wavelength range, it enters a photomultiplier tube, where it is photoelectrically converted into an electrical signal, processed, and reproduced as a visible image on a CRT or photosensitive material, or as a visible image on a CRT or photosensitive material. Recorded and stored on a recording medium.

[0010] Such a light beam scanning device is suitable not only for the above-mentioned radiation image information reading device but also for image recording devices such as laser beam printers, copying machines, printing plate making devices, and image reading devices such as film digitizers. applied to.

[0011]

[Problems to be Solved by the Invention] By the way, when scanning a large object to be scanned using such a light beam scanning device, it is necessary to increase the size of the device in accordance with the increase in the size of the object to be scanned. .

As described above, the light beam scanning device scans an object to be scanned, which is conveyed in the sub-scanning direction, with a light beam deflected in the main scanning direction, which is substantially perpendicular to the sub-scanning direction. Therefore, in order to scan the entire surface of the object to be scanned,
The scanning length of the light beam (in the main scanning direction) is required to be greater than the width of the object being scanned in the main scanning direction, and in order to scan the entire surface of a large object, the focal length of the light beam optical system must be increased. ,
Furthermore, it is necessary to ensure a sufficient scanning length by increasing the scanning angle of the light beam by the optical deflector.

[0013] Therefore, the optical path length of the light beam becomes longer,
Moreover, the optical device of the light beam scanning device also becomes large, resulting in an extremely large light beam scanning device with a longer distance from the optical deflector to the object to be scanned and a large dead space.

In particular, when the above-mentioned radiation image information recording and reproducing system is applied to industrial applications such as non-destructive inspection of buildings and aircraft, large phosphor sheets are often used, and the radiation image information Since the size of the reading device also increases, improvements are required.

An object of the present invention is to solve the problems of the prior art described above, and despite the small size of the device and the small scanning angle of the light beam, it is possible to use a large-sized phosphor sheet for industrial use. An object of the present invention is to provide a light beam scanning device capable of scanning an object to be scanned with a light beam.

[0016]

[Means for Solving the Problems] In order to achieve the above object, the present invention deflects a light beam in the main scanning direction by an optical deflector, so that the light beam is transported in the sub-scanning direction substantially orthogonal to the main scanning direction. A light beam scanning device for two-dimensionally scanning a scanned object, wherein the optical path length from the optical deflector to the scanned object is at different positions at both ends of the scanned object in the main scanning direction. A light beam scanning device is provided, characterized in that a scanning body and the optical deflector are arranged.

[0017]

The present invention provides a light beam scanning device for two-dimensionally scanning an object to be scanned, which is conveyed in a sub-scanning direction substantially orthogonal to the main-scanning direction, with a light beam deflected in the main-scanning direction. , the object to be scanned and the optical deflector are arranged relative to each other so that the optical path length from the optical deflector to the object to be scanned is different at both ends of the object to be scanned in the main scanning direction, and sub-scanning conveyance is performed. The object to be scanned is arranged so that the center line of the scanning angle of the optical deflector and the main scanning line defined on the object to be scanned by the light beam are not perpendicular to each other, and the object to be scanned is conveyed in the sub-scanning direction. It scans the body.

In a conventional optical beam scanning device, the optical path length from the optical deflector to the object to be scanned is made equal at both ends of the object to be scanned in the main scanning direction, that is, the length of the optical path from the optical deflector to the object to be scanned is made equal to the scanning angle of the optical deflector. The object to be scanned is conveyed in the sub-scanning direction and scanned by the light beam in a state where the center line and the main scanning line defined on the object by the light beam are perpendicular to each other, and image reading, image recording, etc. are performed. be exposed. However, in such conventional light beam scanning devices, in order to apply large objects such as industrial phosphor sheets as objects to be scanned, the focal length of the light beam optical system must be increased, and the optical deflector must be It is necessary to increase the scanning angle of the light beam by increasing the main scanning length, which means that the light beam scanning device is large and has a longer distance to the object to be scanned than the optical deflector and has a large dead space. As mentioned above, it is put away.

On the other hand, the light beam scanning device of the present invention connects the object to be scanned and the light beam such that the optical path length of the light beam from the optical deflector to the object to be scanned is different at both ends of the object to be scanned in the main scanning direction. The deflector is arranged and conveyed in the sub-scanning direction, and the object to be scanned is scanned with the light beam. Therefore, even with a light beam scanning device that scans a large object to be scanned, the scanning angle of the light beam by the optical deflector can be reduced, and the dead space where the distance from the optical deflector to the object to be scanned is shorter can be greatly reduced. It can be made smaller and smaller.

Therefore, by applying the light beam scanning device of the present invention, radiation image information reading devices for industrial use such as non-destructive inspection of buildings, etc., which use large phosphor sheets, can be greatly improved. It can be downsized to

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The light beam scanning device of the present invention will be described in detail below with reference to preferred embodiments shown in the accompanying drawings.

FIG. 1 shows a schematic perspective view of an example in which the light beam scanning device of the present invention is applied to a radiation image information reading device (hereinafter referred to as a reading device).

The reading device 10 shown in FIG. 1 directs excitation light L (light beam) deflected in the main scanning direction shown by arrow a into the sub-scanning direction (direction of arrow b) substantially perpendicular to the main scanning direction. By irradiating the transported stimulable phosphor sheet A (hereinafter referred to as phosphor sheet A) on which radiographic image information has been accumulated and recorded, the entire surface of the phosphor sheet A is two-dimensionally scanned with excitation light L. The radiation recorded on the phosphor sheet A is generated by generating stimulated luminescence light according to the image information recorded on the phosphor sheet A, and photoelectrically measuring and processing the stimulated luminescence light. It reads image information.

Such a reading device 10 basically includes a light source 12, a galvanometer mirror 14, and a condensing guide 1.
6, a photomultiplier tube 18, a processing device 20, and a sub-scanning conveyance device (not shown) for the phosphor sheet A. Here, in the reading device 10 to which the light beam scanning device of the present invention is applied, the optical path length of the excitation light L from the galvanometer mirror 14 to the phosphor sheet A is
The central line of the scanning angle θ by the galvanometer mirror 14 and the excitation light L differ depending on both ends in the main scanning direction.
The phosphor sheet A is conveyed in the sub-scanning direction in a state where the phosphor sheet A is not perpendicular to the main scanning line S defined on the phosphor sheet A, and the radiation image information carried on the phosphor sheet A is read.

The excitation light L is emitted from the light source 12 and enters the galvanometer mirror 14 . As the light source 12, He-
Various light sources such as Ne laser and semiconductor laser can be used.

The excitation light L incident on the galvanometer mirror 14 is reflected and deflected in the main scanning direction (arrow a direction) and irradiates the phosphor sheet A. Note that the optical deflector applied to the present invention is not limited to the illustrated galvanometer mirror 14, and any known optical deflector such as a polygon mirror or a resonant scanner can be applied.

It goes without saying that in the optical path of the excitation light L, various optical elements such as various optical systems for correcting surface tilt, mirrors for changing the optical path, etc. may be arranged as necessary.

On the other hand, the phosphor sheet A has a structure in which a stimulable phosphor layer is laminated on a support such as polyethylene terephthalate, and is transported in a sub-scan direction approximately perpendicular to the main scanning direction by a sub-scan conveying means (not shown). Direction (arrow b direction)
is being conveyed in the sub-scanning direction. Therefore, the excitation light L deflected in the main scanning direction irradiates the entire surface of the phosphor sheet A two-dimensionally.

Stimulated luminescence light is emitted from the position of the phosphor sheet A that is irradiated with the excitation light L in accordance with the radiation image information stored and recorded there. This stimulated luminescent light is photoelectrically read by a condensing system consisting of a light guide 16 and a photomultiplier tube 18, and the result is sent to a processing circuit 22 of a processing device 20.
The image is then sent to the computer for image processing. The image information processed by the processing circuit 22 is reproduced as a visible image on the CRT 24 or various photosensitive materials, or stored in an image recording medium 26 or the like.

There is no particular limitation on the sub-scanning conveyance means for the phosphor sheet A, such as a pair of nip rollers arranged with the main scanning line S in between, a belt conveyor, etc. Any means of conveying objects is applicable.

Here, in the reading device 10 according to the light beam scanning device of the present invention, the galvanometer mirror 14
The optical path length of the excitation light L to the phosphor sheet A differs depending on both ends of the phosphor sheet A in the main scanning direction, that is, the center line of the scanning angle θ by the galvanometer mirror 14,
In a state where the main scanning line S defined on the phosphor sheet A by the excitation light L is not perpendicular to the main scanning line S (hereinafter referred to as "disposed diagonally with respect to the galvanometer mirror 14"), the phosphor sheet A is It is scanned and conveyed.

In a reading device using a conventional light beam scanning device, the phosphor sheet A, which is the object to be scanned, is placed directly opposite the galvanometer mirror 14. Therefore, in order to make it possible to read a large phosphor sheet A, the focal length of the light beam optical system must be increased, and the scanning angle of the light beam by a light deflector such as a galvanometer mirror must be increased to increase the main scanning length. As described above, the optical beam scanning device becomes a large device with a long distance from the optical deflector to the object to be scanned and a large dead space.

On the other hand, in the reading device 10, by arranging the phosphor sheet A obliquely with respect to the galvanometer mirror 14, which is an optical deflector, as shown in FIG. Even if the sheet A is arranged at a very close distance and the scanning angle θ by the galvanometer mirror 14 is small, the scanning length by the excitation light L, that is, the main scanning line defined on the phosphor sheet A by the excitation light L S can be made sufficiently long. Therefore, although the reading device 10 can be made compact with small dead space, it is also possible to read images of large phosphor sheets A used for destructive inspection of buildings and airplanes.

In the reading device 10 to which the light beam scanning device of the present invention is applied, the distance between the galvanometer mirror 14 and the phosphor sheet A differs depending on the position on the main scanning line S. The main scanning speed of the light L and the beam diameter on the phosphor sheet A differ, and the intensity of the excitation light L varies depending on the scanning position, resulting in the obtained radiation image information becoming unclear. Sometimes. However, these disadvantages can be almost eliminated by the following method.

FIG. 2 conceptually shows a plan view of the reading device 10 shown in FIG. 1. Note that in FIG. 2, the light guide 16, photomultiplier tube 18, etc. are omitted for clearer explanation.

When the excitation light L is collimated light such as He-Ne laser light, the galvanometer mirror 14
When the phosphor sheet A is arranged obliquely to the galvanometer mirror 14, as shown in FIG.
Since the excitation light L1 enters at a position closer to the phosphor sheet A, the spot diameter of the spot S2 of the excitation light L2 is the same as the spot S1 of the excitation light L1.
It becomes larger in the main scanning direction compared to . Furthermore, since the optical path length of the excitation light L from the galvanometer mirror 14 differs depending on the position on the main scanning line S, the scanning speed with respect to a change in the scanning angle of the galvanometer mirror 14 is faster on the excitation light L2 side than on the excitation light L1 side. .

As is well known, the scanning speed of the central portion of the galvanometer mirror 14 is faster than that at both ends of the scanning angle. Therefore, when the galvanometer mirror 14 is used as the optical deflector as in the illustrated example, the excitation light L
1 near the center line of the scanning angle of the galvanometer mirror 14, and the excitation light L2 near the end of the scanning angle, and by adjusting the angle of the phosphor sheet A with respect to the galvanometer mirror 14, the scanning speed of the excitation light L can be controlled as the main The entire scanning line S can be made substantially uniform.

Furthermore, by performing sharpness correction through image processing in the processing circuit 22 and modulating the intensity of the He-Ne laser as necessary, excitation due to differences in spot diameters of spots S1 and S2 and differences in optical path length can be corrected. By correcting the intensity of the light L, clear radiation image information can be obtained. Also, the error due to the difference in beam spot diameter in the main scanning direction is
It is possible to correct the measured intensity of stimulated luminescence light by electrically processing it.

FIG. 3 conceptually shows a plan view of another example of a reading device to which the light beam scanning device of the present invention is applied. In addition,
The reading device 30 shown in FIG. 3 has the same basic configuration as the above-described reading device 10, so the same members are given the same numbers and detailed explanation thereof will be omitted. Also, in the example shown in FIG. 3, the light guide and the like are omitted.

The reading device 30 shown in FIG.
After the beam diameter of excitation light L emitted from a light source 12 such as an e-laser is expanded by a beam expander 34, this excitation light is focused in the main scanning direction (direction of arrow a) by a cylindrical lens 36, and then passed through a galvanometer mirror. 14
to scan the phosphor sheet A.

Here, the reading device 30 applies the light beam scanning device of the present invention, and the optical path length of the excitation light L from the galvanometer mirror 14 to the phosphor sheet A is different at both ends of the main scanning line S. Therefore, in a cylindrical lens having a focal position at a position where the optical path length of the excitation light L is longer, for example, the incident position of the excitation light L4 is the focal length (position).
A cylindrical lens 36 is used.

In the reading device 30 having such a configuration, although the spot S4 of the excitation light L4 is imaged, it is incident on the phosphor sheet A obliquely as before, so the spot diameter is It becomes slightly thicker in the main scanning direction. On the other hand, although the excitation light L3 is incident almost perpendicularly to the phosphor sheet A, it is not focused on the spot S.
3 is slightly thicker than the imaged state.

Therefore, by appropriately selecting the focal length and focal position of the cylindrical lens 36, the spot diameter of the excitation light L that scans the phosphor sheet A can be made approximately equal over the entire main scanning line S. According to the reading device 30 shown in FIG. 3, more accurate radiation image information can be read.

Note that the reading device 30 shown in FIG. 3 also performs sharpness correction,
Of course, the intensity of the He-Ne laser may be modulated if necessary.

In the reading device 10 shown in FIG.
Although the light guide 16 was arranged on the surface to be scanned (front surface) side of the phosphor sheet A to perform image reading, the present invention is not limited to this. For example, as shown in FIG. Using a phosphor sheet A2 with a transparent body, phosphor sheet A2
A configuration may also be adopted in which a condensing guide 38 is provided on the back side of the camera to read images. With the above configuration, it is possible to prevent the device from increasing in size due to the light guide, and it is possible to realize a more compact reading device.

A reading device to which the light beam scanning device of the present invention is applied is particularly suitable for applications that do not require high-precision image reading, such as industrial applications such as non-destructive inspection of buildings. be. Further, by using a reading device to which the present invention is applied, a preliminary inspection may be performed over a wide area using a large phosphor sheet, and a high-precision inspection may be performed again at a location where an abnormality has been detected.

Although the above-mentioned example was an example in which the light beam scanning device of the present invention was applied to a radiation image information reading device, the present invention is applicable not only to the radiation image information reading device but also to film digitizers, laser beam printers, The present invention can be suitably applied to various image reading or recording devices such as X-Y plotters, copying machines, printing plate-making machines, etc., especially devices that handle large-sized recording materials, manuscripts, etc.

Although the light beam scanning device of the present invention has been described in detail above, the present invention is not limited thereto, and various improvements and changes may be made without departing from the gist of the present invention. Of course.

[0049]

Effects of the Invention As described in detail above, the light beam scanning device of the present invention is capable of light beam scanning of a large object to be scanned even if the device size is small, and is suitable for use in destructive inspection of buildings, etc. Conventionally, it was impossible to avoid increasing the size of the equipment, such as radiation image information reading equipment used in industrial applications, but it is now possible to significantly downsize image reading equipment and image recording equipment that apply large objects to be scanned. can.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view of an example in which a light beam scanning device of the present invention is applied to a radiation image reading device.

FIG. 2 is a diagram conceptually showing a plane of the radiation image information reading device shown in FIG. 1;

FIG. 3 is a diagram conceptually showing a plane of another example in which the light beam scanning device of the present invention is applied to a radiation image reading device.

FIG. 4 is a diagram conceptually showing a plane of another example in which the light beam scanning device of the present invention is applied to a radiation image reading device.

[Explanation of symbols]

10, 30 Radiation image information reading device 12 Light source 14 Galvanometer mirror 16 Light guide 18 Photomultiplier tube 20 Processing equipment 22 Processing circuit 24 CRT 26 Image recording medium 34 Beam expander 36 Cylindrical lens A, A2 Phosphor sheet L Excitation light S Main scanning line

Claims (1)

[Claims] 1. A light beam scanning device that deflects a light beam in a main scanning direction by an optical deflector and two-dimensionally scans a scanned object being conveyed in a sub-scanning direction substantially orthogonal to the main scanning direction. The object to be scanned and the optical deflector are arranged at positions where the optical path lengths from the optical deflector to the object to be scanned are different at both ends of the object to be scanned in the main scanning direction. Light beam scanning device.