JPH0259964B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a device that reads image information by scanning excitation light two-dimensionally on a stimulable phosphor sheet on which image information is stored and recorded, and particularly in the return path of reciprocating main scanning. The present invention relates to an image scanning reading device that erases lines.

Certain fluorophores are exposed to radiation (X-rays, α-rays, β-rays,
When irradiated with γ-rays, ultraviolet rays, etc., a part of this radiation energy is accumulated in the phosphor, and when this phosphor is irradiated with excitation light such as visible light, the phosphor increases depending on the accumulated energy. is known to exhibit stimulated luminescence, and phosphors exhibiting this property are called stimulable phosphors.

By using this stimulable phosphor, radiation image information of a human body, etc. is temporarily stored in a sheet having a layer made of a stimulable phosphor (hereinafter referred to as a ``stimulable phosphor sheet'' or simply ``sheet''). This stimulable phosphor sheet is scanned with excitation light such as a laser beam to generate stimulated luminescent light, and the resulting stimulated luminescent light is read out photoelectrically to obtain an image signal. The applicant has already proposed a radiation image recording/reading system that outputs a visible image to a recording material such as a photographic light-sensitive material, CRT, etc. based on a signal. (Tokukai Akira
No. 55-12429, No. 56-11395, etc. ) The image scanning/reading device in this radiation image recording/reading system scans a stimulable phosphor sheet two-dimensionally using a laser beam or the like as excitation light, and uses photoelectric detection of the stimulated luminescent light emitted at that time to detect the stimulated luminescent light emitted at that time. A method is adopted in which image signals are obtained by detecting images in time series using a device. Two-dimensional scanning at this time is performed by performing main scanning and sub-scanning on the sheet using excitation light, but for this purpose, generally the sheet is moved in one direction to perform sub-scanning, and the sheet is moved in the same direction as the sheet. Main scanning is performed by reciprocating the excitation light in a perpendicular direction.

A commonly used means for performing this main scanning includes a galvanometer mirror that reciprocates along a fixed trajectory at a fixed speed. Since the sub-scanning is performed continuously at a constant speed, the scanning line drawn on the stimulable phosphor sheet by this main scanning means is a polygonal line having a fixed angle with respect to the direction perpendicular to the sub-scanning direction. It is formed in a shape (pine needle-like). In this case, since the diameter of the light beam is a certain size, the scanning lines overlap at the point where scanning is switched from forward scanning to backward scanning or vice versa. Especially when trying to perform high-precision reading by increasing the scanning line density,
Since each round trip scan line is scanned close to each other, the amount of overlap between the scan lines is increased.

A stimulable phosphor sheet has the property that once it is irradiated with excitation light and emits stimulated luminescence light, the amount of accumulated information decreases, so when the above-mentioned overlap of scanning lines occurs, the actual When performing a reading scan, the image information in the overlapping area has already been read and reduced by the excitation light irradiation during the previous retrace scan, making it difficult to read the image information accurately during the next scan. There was a problem that it was not done.

In order to solve this problem, a light beam is prevented from passing on the optical path of the light beam in this image scanning/reading device only during the retrace scanning period in synchronization with the reciprocating main scanning of the main scanning means. A countermeasure has been proposed in which a light beam is not irradiated onto the sheet during the retrace scanning period by inserting a light shielding means that operates as shown in FIG. (Applicant: Fuji Photo Film Co., Ltd., filed on June 24, 1981) This light shielding means is usually arranged at a position where the light beam between the excitation light source and the galvanometer mirror as the main scanning means is focused. It has a substantially vertical rotation axis and is provided with a plate-shaped shutter member at its tip that blocks the beam only during the retrace scanning period. However, since such a countermeasure uses a mechanical light shielding means, there is a limit to the response speed (approximately 50 Hz to 100 Hz), and there is a problem in that it is difficult to support higher-speed reading scanning.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image scanning reading device capable of reading image information at high speed and accurately by eliminating the reduction in image information due to duplication of reciprocating main scanning lines. That is.

The image scanning reading device of the present invention includes an excitation light source, and main scanning means for performing main scanning by reciprocally scanning a light beam emitted from the excitation light source onto a stimulable phosphor sheet on which image information is accumulated and recorded. , an image comprising sub-scanning means for sub-scanning in a direction perpendicular to the main-scanning direction, and reading means for photoelectrically reading stimulated luminescence light corresponding to image information emitted from the stimulable phosphor sheet. In the scanning reading device, a beam focusing means for focusing the light beam at one point on the optical path of the light beam is provided, and the reciprocating main scanning means is provided on the optical path between the focusing means and the excitation light source. An acousto-optic modulator is provided which diffracts the light beam to generate diffracted light other than zero-order light during the retrace scanning period of the main scan in synchronization with the retrace scanning period of the main scan, and further includes an acousto-optic modulator that diffracts the light beam to generate diffracted light other than the zero-order light, and further includes a beam focusing position focused by the focusing means. The present invention is characterized in that a light shielding plate having a pinhole that allows only the 0th order diffracted light from the acousto-optic modulator to pass through is provided.

Note that the diffracted light other than the 0th-order light herein refers to higher-order diffracted light such as the 1st-order light, the 2nd-order light, the -1st-order light, and the -2nd-order light. In addition, an acousto-optic modulator is an optical modulator that uses the acousto-optic effect, and utilizes the fact that the intensity of the first-order diffracted light in the Debashiers effect or Black diffraction is approximately proportional to the ultrasonic output, and modulates the ultrasonic output to produce light. It performs modulation. Therefore, although the modulation bandwidth is on the order of several hundred MHz, the extinction ratio can be made extremely small, and the device has the advantage of having good operational stability against temperature changes.

Furthermore, in the present invention, the light shielding plate having a pinhole that allows only the zero-order light to pass through is provided at the beam focusing position focused by the focusing means because the diffracted beams by the acousto-optic modulator are extremely close to each other. This is because unless the beam diameter is at a small position, it will be difficult to block only the diffracted light other than the zero-order light.

According to the image scanning reading apparatus of the present invention, an acousto-optic modulator is provided on the optical path between the excitation light source and the light beam focusing means of this apparatus, and the modulation of this modulator is used as the main scanning means of the reciprocating main scanning means of this apparatus. Synchronized with scanning, the light beam from the excitation light source is diffracted only during the retrace scan period to generate diffracted light of 1st order or higher or -1st order or lower, and the excitation light is further directed to the beam focusing position of the light beam focusing means. A light-shielding plate having a pinhole that allows only the 0th-order light to pass through is provided to block diffracted light other than the 0th-order light diffracted during the retrace scanning period. Unlike a blanking device using blanking means, it has excellent responsiveness (approximately tens of thousands of times more responsive than mechanical light shielding means), and can therefore easily support high-speed reading scanning. In other words, according to this device, even when performing high-speed image reading, it is possible to prevent the irradiation of excitation light onto the stimulable phosphor sheet by retrace scanning, and the amount of information accumulated on the sheet can be prevented from being irradiated by retrace scanning. Since the image information is not reduced by , accurate reading of image information can be performed. Further, this acousto-optic modulator can accurately and quickly control variations in light beam output, and is useful as a light amount stabilizing means. Furthermore, compared to conventional mechanical light shielding means, it has the advantage of being extremely reliable since it does not have any moving parts. Therefore, the image scanning reading device of the present invention using such an acousto-optic modulator has extremely high practical value.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing an embodiment of an image scanning reading device according to the present invention.

In FIG. 1, a magnetic layer 2a is laminated on the surface of an endless belt 2 which is drivably suspended around a pair of rollers 1a and 1b, and a stimulable phosphor sheet 3 is adhered thereon by magnetic force. 2 is driven by the rotation of rollers 1a and 1b (arrow A), and at the same time a laser light source 5 is placed on this sheet 3.
An image scanning/reading device that scans and irradiates a light beam 4 from a galvanometer mirror 6 in a direction (arrow B) perpendicular to the moving direction A of the endless belt 2, and scans the sheet 3 two-dimensionally with the light beam 4. This shows that. That is, a pair of rollers 1a, 1
The sub-scanning means consisting of the belt 2 and the endless belt 2 perform sub-scanning in the A direction, and the galvanometer mirror serving as the main scanning means performs sub-scanning in the direction B perpendicular to the sub-scanning.
main scanning is being performed. The endless belt 2 is made by laminating a magnetic layer 2a on a flexible endless belt-shaped support 2b.

The stimulable phosphor sheet 3 has a magnetic layer 3a and a stimulable phosphor layer 3b.
In b, an image of radiation transmitted through the object is stored and recorded. When this sheet 3 is irradiated with a light beam 4,
The irradiated part exhibits stimulated luminescence, and this stimulated luminescence is focused by a total reflection light guide plate 7 made of, for example, an acrylic plate, and detected by a photoelectric detector 8 such as a photomal. An image signal is obtained. The image signal is obtained as a time-series image signal according to two-dimensional scanning, and is used for image processing and reproduction. Further, on the optical path of the light beam 4 from the laser light source 5, an acousto-optic modulator 12 is located next to the laser light source 5, and between the acousto-optic modulator 12 and the galvanometer mirror 6, a pair of convex lenses 9a and 9b are connected. A light beam focusing means 9 is provided, and a light shielding plate 10 having a pinhole through which only the zero-order light from the acousto-optic modulator 12 passes is provided at the beam focusing position of the light beam focusing means 9.

Furthermore, an imaging lens 11 is provided between the galvanometer mirror 6 and the stimulable phosphor sheet 3 to focus the light beam 4 onto the stimulable phosphor sheet 3.

The acousto-optic modulator 12 is a galvanometer mirror 6
The modulator 12 is controlled so as to modulate the light beam from the laser light source 5 only during the retrace scan period in synchronization with the reciprocating main scan of the laser beam, and not to modulate the modulator 12 during the read scan.

That is, during read scanning, the modulator 12 does not perform modulation and only transmits most of the incident laser beam (the amount of transmitted light is 97
~98%) is transmitted as zero-order light.

This zero-order light is transmitted through the convex lens 9 of the beam focusing means 9.
The light is once focused by a, passes through a light shielding plate 10 having a pinhole provided at this focusing position, becomes parallel light again by a convex lens 9b, and enters the galvanometer mirror 6.

Note that the beam focusing means 9 has the role of expanding the beam diameter after once focusing the light beam.
The light beam 4 whose beam diameter has been expanded is passed through the imaging lens 1
1 onto the sheet 3.

The reason for expanding the beam diameter in this way is to reduce the final imaging light spot.

Also, during retrace scanning, the modulator 12 diffracts the light beam so that the modulation efficiency is maximized, and makes most of the light amount (90 to 95%) of the incident light beam diffracted light other than the zero-order light. . At this time, about 5 to 10% of the light amount of the incident light beam exists as the 0th order light, and the diffracted light other than the 0th order light is blocked from passing by the light shielding plate 10, and the 0th order light passes through the light shielding plate 10. do.

FIG. 2 shows an enlarged schematic diagram of the acousto-optic modulator 12, the light beam focusing means 9, and the light shielding plate 10 shown in FIG. This figure shows a light shielding plate 10 provided at a light beam convergence position where diffracted light other than the 0th-order light, for example, the first-order light 14 and the second-order light 15, is diffracted by the acousto-optic modulator 12 during the retrace scanning period. The figure shows how it is shielded by. In this case, as mentioned earlier, the 0th order light 13 is 5 to 10 times the amount of light of the incident beam.
%, but this is due to the general characteristics of the acousto-optic modulator, and even if this amount of light is irradiated onto the stimulable phosphor sheet 3 during retrace scanning, it will have almost no effect in practice. do not have. Additionally, when performing main scanning, retrace scanning is generally performed at a higher speed than reading scanning, so the sheet 3 during retrace scanning is
The upward irradiation energy can be further reduced.

As described in detail above, according to the present invention, an acousto-optic modulator is used to prevent the excitation light beam from being irradiated onto the stimulable phosphor sheet during retrace scanning, so that no accumulation occurs. It is possible to prevent image information from being read during retrace scanning, thereby allowing high-speed and accurate reading of image information.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing one embodiment of an image scanning reading device according to the present invention, and FIG. 2 is a partially enlarged schematic diagram of FIG. 1. 2... endless belt, 3... stimulable phosphor sheet, 5... laser light source, 6... galvanometer mirror, 8... photoelectric detector, 9a, 9b... lens of beam focusing means, 10... light shielding plate, 11... focusing lens,
12...Acousto-optic modulator.

Claims (1)

[Scope of Claims] 1. An excitation light source, main scanning means for performing main scanning by reciprocally scanning a light beam emitted from the excitation light source onto a stimulable phosphor sheet on which image information is accumulated and recorded; An image comprising a sub-scanning means for sub-scanning in a direction substantially perpendicular to the main-scanning direction, and a reading means for photoelectrically reading stimulated luminescence light corresponding to image information emitted from the stimulable phosphor sheet. In the scanning reading device, a beam focusing means for focusing the light beam at one point on the optical path of the light beam is provided, and the reciprocating main scanning means is provided on the optical path between the focusing means and the excitation light source. An acousto-optic modulator is provided which diffracts the light beam to generate diffracted light other than the zero-order light during the retrace scanning period of the main scan in synchronization with the retrace scanning period of the main scan, and further includes an acousto-optic modulator that diffracts the light beam to generate diffracted light other than the zero-order light, and further at a beam focusing position focused by the focusing means. . An image scanning reading device comprising a light shielding plate having a pinhole that allows only the zero-order diffracted light from the acousto-optic modulator to pass through.