JPS58174921A - Laser light scanner - Google Patents

Abstract

PURPOSE:To measure the intensity of laser light on a scanning body to be scanned exactly and to make the density of a reproduced image adequate, by providing a refractive optical element which conducts the drift light of the laser light always to the center of a photodetector which monitors the intensity of the laser light in front of the photodetector. CONSTITUTION:The laser light 2 from a laser light source 1 is scanned on an storage type phosphor sheet 4 by a galvanometric mirror 3 in a main scanning direction A, and the sheet 4 is moved in a subscanning direction B. A photodetector 7 consisting of a photodiode for measuring the intensity of the light 2 is installed on the extension line of a main scanning line 8 on the outside of the sheet 4. Even if the drift light 10, 10' are generated by the laser light 2 which deviates from a reference position in the stage of starting reading, the light 2 is made incident to approximately the center of the detector 7 by a cylindrical lens 9; therefore, the intensity of the laser light is measured surely and exactly.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a laser charging and scanning device that scans to read and record images, and more specifically, it has a source detector that focuses the laser beam to be scanned and monitors the intensity of the laser source. This invention relates to a laser source scanning device.

2. Description of the Related Art Conventionally, laser beam scanning devices have been widely used that read or record images by two-dimensionally scanning a scanned object with a laser beam in main scanning and sub-scanning.

Examples of laser beam scanning devices that perform reading include computer input devices and image reading devices such as facsimile machines. In this device, a laser beam is scanned two-dimensionally across the original, and the resulting reflected light (in the case of paper originals) or transmitted light (in the case of film originals) is received by a photodetector. The image information is read by outputting the image information recorded on it as a serial electrical signal.

Further, as a laser beam scanning device for recording, for example, a device that scans a recording material such as a photosensitive material two-dimensionally with a modulated laser beam according to image information to form an image, and a device that forms an image on a recording material such as a photosensitive material, etc. This is a so-called laser printer, in which a laser beam modulated according to the image information is scanned two-dimensionally on the photoconductor, forming a latent image on the photoconductor, which is then developed with toner, transferred to recording paper, and fixed. Things are known...
reactor.

Such laser beam scanning devices for reading and recording images have the following five drawbacks.

In other words, in a scanning optical system that includes a laser light source, mirrors, lenses, optical deflectors, etc., there are fluctuations in the amount of light due to deterioration of the laser light source and fluctuations in the transmittance of the entire optical system due to dust, etc. In the long term, the intensity of the laser beam is 10
Even if the signal read by such a laser scanning optical system, which avoids fluctuations of up to 20%, is reproduced as it is, it is not always possible to obtain an image with an appropriate density. Furthermore, in the case of recording, it goes without saying that if there is a variation in the intensity of the laser beam on the object to be scanned (recording material such as a photographic light-sensitive material) as described above, the reproduced image will not have an appropriate density.

To solve this problem, the intensity of the laser beam is measured once just before image reading or recording, and based on this measured value, in the case of reading, the power of the laser light source is adjusted or the power of the photodetector is adjusted. By adjusting the gain and then taking the image a, it is possible to read the image under proper axl conditions.For recording, it is necessary to adjust the power of the laser light source or use the optical modulator. An attempt has been made to overcome this problem by controlling the intensity of the laser beam, thereby making it possible to record images with appropriate density. For this,
Conventionally, the intensity of this laser light has been measured by inserting a No. 7 mirror into the optical system upstream of the optical deflector (on the laser light source side), or by controlling the optical deflector to ,
The laser beam is extracted by excessively deflecting the laser beam to an extension of the main scanning line of the laser beam, and is guided to a photodetector such as a photodiode to measure its intensity.

However, in the measurement method that inserts a Fumira in the middle of the scanning optical system, it is possible to always make the stationary laser beam enter the center of the photodetector, but the precision of the laser beam on the object to be scanned is The drawback was that it was not possible to measure exact strength.

In addition, in a measurement method in which a deflector is controlled to cause the laser beam to enter a photodetector that monitors the intensity of the laser beam at one end of the main scanning direction, the positional deviation of the main scanning end of the optical deflector is Therefore, it is difficult to ensure that the laser beam always performs main scanning to a constant position, and in reality, the laser beam may generate drift light that deviates from the reference position.

When this drift light occurs, the laser light may miss the photodetector, or the laser light may enter the periphery of the photodetector whose sensitivity is different from the center, making it impossible to reliably and accurately measure the intensity of the laser light. there were.

The drawback of the above-mentioned laser beam scanning device is that, for example, as disclosed in Japanese Patent Application Laid-open No. 12,429/1987 by the present applicant, once radiographic image information is accumulated and recorded on a stimulable phosphor sheet, Laser light, which is excitation light, is scanned two-dimensionally on this stimulable phosphor sheet to generate stimulated luminescence light, and the resulting stimulated luminescence light is read out optically by a detector to generate an image signal. A radiological diagnostic system is disclosed in Japanese Patent Laid-Open No. 121.04-3/1980, which performs appropriate image processing based on this electric signal, and further records and reproduces a radiation image on a recording material such as a photosensitive material based on this electrical signal. X that seems to be
Line image information is once recorded on a low-gamma photographic film, which is an intermediate medium, and then a laser beam is scanned two-dimensionally on the photographic film to read the recorded information as an electrical signal and perform appropriate image processing. Furthermore, in radiological diagnostic systems that record and reproduce X-ray images on recording materials based on this electrical signal, variations in the output of the laser light source used and the transmittance of the entire scanning optical system affect the resulting reproduced image. This was a particularly serious problem because it directly affected the concentration, resulting in a serious negative impact on diagnostic performance.

The present invention eliminates the above-mentioned drawbacks of the prior art, reliably and accurately measures the intensity of the laser light on the object to be scanned, and corrects variations in the output of the laser light source and the transmittance of the entire scanning optical system. The object of the present invention is to provide a laser beam scanning device.

Such an object of the present invention is to detect the drift light of the laser light in front of the photodetector which is located on the extension line of the main scanning line outside the object to be scanned and which receives the laser light and monitors the intensity of the laser light. This is achieved by a laser beam scanning device characterized by being provided with a refractive optical element that always guides the light to the center of the photodetector.

According to the present invention, even if the optical deflector is not precisely controlled and drift light occurs in which the laser beam deviates from the reference position, the refractive optical element allows the laser beam to be positioned at the center of the photodetector. The intensity of the laser light on the scanning body can be measured reliably and accurately.Therefore, it is possible to correct variations in the output of the laser light source and the transmittance of the entire scanning optical system.

The present invention also relates to reading and recording of radiation images in a radiation image conversion system using a stimulable phosphor as disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 55-12,429, or Japanese Patent Application Laid-Open No. 54-121.043. When fluctuations in the intensity of laser light on a scanned object are a major problem, such as when reading and recording X-ray images in an XfIJ image conversion system using a low-gamma photographic film as an intermediate medium, as disclosed in No. It is particularly preferably used.

In the present invention, a refractive optical element refers to a cylindrical lens, a convex lens, etc. that refracts light in the positive direction, and has the effect of always refracting laser light moving in the main scanning direction toward the center of the photodetector. It is something to do. In other words, for example, if a cylindrical lens is placed outside the document with its axis perpendicular to the main scanning direction, and the laser beam is scanned across the cylindrical lens in the main scan, the laser beam will be refracted by the cylindrical lens. Therefore, while passing through the cylindrical lens, it always passes through one point. This one point is defined by the optical distance a from the output point of the optical deflector (for example, the reflection point of the galvanometer mirror) to the cylindrical lens, and the condensing distance f of the cylindrical lens. An embodiment of the present invention in which the object of the present invention is achieved by arranging the cylindrical lens so that this point is located at a distance from the cylindrical lens so that this point is located exactly in the center of the photodetector. This will be explained in detail based on the drawings.

FIG. 1 is a schematic diagram showing a first embodiment of the present invention,
1 is an embodiment of a laser phototaxis reading device based on a radiation imaging system using a stimulable phosphor sheet.

In this embodiment, reading is performed as follows. Laser light 2 from a laser light source 1 is scanned by a galvanometer mirror 3 onto a stimulable phosphor sheet 4 in a main scanning direction A. Further, the stimulable phosphor sheet 4 is moved in the sub-scanning direction B and is two-dimensionally scanned by the laser beam 2. The light emitted from the scanned stimulable phosphor sheet 4 by the scanning of the laser beam 2, the stimulated luminescent light, enters the incident end 5a of the light transmitting member 5 made of a transparent sheet and is transmitted therein. The light is focused on the light receiving surface of the photomultiplier tube 6. The emission end of the light transmission member 5 is annular to match the shape of the circular light-receiving surface of the photomultiplier tube 6, and light is transmitted from one linear end to one end of the annular shape by total reflection.

A cut filter is inserted between the photomultiplier tube 6 and the annular exit end of the light transmission member 5, which does not pass the wavelength range of the laser beam 2 but only transmits the wavelength range of the stimulated luminescent light. For example, the 20 wavelength range of laser light is the 300-500 wavelength range of stimulated luminescence light.
600-700n so as not to overlap with nm.
In the case of m, the cut filter may be a long wavelength cut filter that cuts wavelengths longer than 500 nm.

By inserting the cut filter in this way, the stimulated luminescence light from the stimulable phosphor sheet can be detected separately from the laser light 2, so image information can be detected with a high SA ratio.

A photodetector 7 consisting of a photodiode for measuring the intensity of the laser beam 20 is installed on an extension of the main scanning line 8 outside the stimulable phosphor sheet 4, which is the object to be scanned. Photodetector 7
A cylindrical lens 9 that refracts light in the main scanning line direction is installed in front of the cylindrical lens 9, which deflects drift light 10 and 10' that deviates in the main scanning line direction due to failure to accurately control the optical deflector 3. It is configured to always lead to the center of the photodetector 7.

At the start of reading, the laser beam 2 is excessively deflected by the optical deflector and is guided to the photodetector 7 installed outside the object to be scanned. At this time, the optical deflector was not accurately controlled and the laser beam deviated from the reference position.Drift light10.10
Even if ' occurs, the cylindrical lens 9 allows the laser beam 2 to enter approximately the center of the photodetector 7. Therefore, the laser beam 2 will not miss the light-receiving part of the photodetector 7, or the laser light will not enter the peripheral part of the light-receiving part, which has a different sensitivity from the center, and the intensity of the laser light can be reliably and accurately measured. can do. If the power of the laser light source or the amplification degree of the photodetector is controlled based on the value of the intensity of the laser light measured in this way, signal detection can be performed at an appropriate level5, and a high ratio can be achieved. It is possible to obtain a radiation image having an appropriate density and excellent suitability for observation and interpretation.

When image information is read out using reflected light from a sheet on which image information is recorded in a density pattern on a paper document, image reading can be performed in substantially the same manner as in this embodiment, but in this case, this is not necessary.

In addition, when reading image information from a sheet on which image information is recorded in a density pattern on a film original, it is necessary to read out the image information using transmitted light. The scanner may be placed on the back side of the object to be scanned, which is a film original, along the scanning line.

FIG. 2 is a schematic diagram showing a second embodiment of the present invention,
This is an embodiment of a laser beam scanning recording device.

In this embodiment, recording is performed as follows.

Laser light 12 emitted from a laser light source 11 is modulated by a light modulator 13 according to the image to be output, and then directed by a light deflector 14 such as a galvanometer mirror onto a recording medium 15 which is an object to be scanned such as a photographic light-sensitive material. The incident light is deflected by The recording medium 15 is moved in a direction perpendicular to the main scanning direction to perform sub-scanning, and an image is recorded over the entire surface of the recording medium 15 by two-dimensional scanning.

A photodetector 16 made of a photodiode or the like that measures the intensity of the v-sample light 12 is installed on an extension of the main scanning line outside the recording medium 15 that is the object to be scanned.
In front of the is a lens 17 that refracts light in the main scanning line direction.
is installed, and is configured to always guide drift lights 18 and 18', which are shifted in the main scanning line direction due to failure to accurately control the optical deflector 14, to the center of the photodetector 16.

At the start of recording, the laser beam 12 is excessively deflected by the optical deflector 14, so that the laser beam is guided to a photodetector 16 installed outside the recording medium 15. At this time, even if the optical deflector 14 is not precisely controlled and the laser beam 12 produces a drift beam 18, 18' that deviates from the reference position, the lens 17 allows the laser beam to always enter the center of the photodetector 16. It will be done. Therefore, the laser light does not miss the photodetector 16 or enter the peripheral part of the light receiving part, which has a different sensitivity from the center, and the intensity of the laser light can be measured reliably and accurately. can. By adjusting the driver 19 of the optical modulator 13 based on the value of the intensity of the laser beam measured in this way, it is possible to record an image at an appropriate density. Although the intensity of the laser beam can be adjusted by controlling the output of the laser light source 11, it is preferable to adjust the intensity of the laser beam using the optical modulator 13.

In addition to photographic light-sensitive materials that directly produce visible images, the recording medium may also be an electrophotographic light-sensitive plate that uses a photoconductor to form a latent image, develop a toner, transfer it to recording paper, and fix it. .

In each of the embodiments described above, the object to be scanned is made of a flat sheet, but the object to be scanned is a cylindrical rotating drum.
It may also be made by rolling soba. In this case, sub-scanning is performed by rotating the rotary drum.

As described in detail above, according to the present invention, a photodetector for monitoring the intensity of the laser beam is provided on an extension of the main scanning line outside the object to be scanned, and the laser beam is placed in front of the photodetector. By providing a refractive optical element that guides the drift light to the photodetector, it becomes possible to reliably and accurately measure the intensity of the laser light on the object to be scanned. Therefore, just before image reading or recording, the intensity of the laser beam is measured, and based on this measured value, for reading, for example, the power of the laser light source or the gain of the photodetector is adjusted, and for recording, for example, By adjusting the power of the laser light source or the optical modulator, reading and recording can always be performed under appropriate conditions.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a first embodiment of the present invention,
1 is an embodiment of a laser phototaxis reading device based on a radiation imaging system using a stimulable phosphor sheet. FIG. 2 is a schematic diagram showing a second embodiment of the present invention,
This is an embodiment of a laser beam scanning recording device. 1.11...Laser light source 2,12...Laser light 3.14...Light deflector 4...Storage phosphor sheet 5...Light transmission member 6...Photomultiplier tube 7.1
6... Photodetector 9, 17... Lens 10
, Ic, 18.18'... Drift
Driver 13... Optical modulator 19... Optical modulator driver

Claims (1)

[Claims] A laser consisting of a laser light source, a main scanning means that performs main scanning by scanning a laser beam emitted from the laser light source onto a scanned object, and a sub-scanning means that performs sub-scanning in a direction perpendicular to the main scanning direction. In the optical scanning device, a photodetector is provided on an extension line of the main scanning line outside the object to be scanned and monitors the intensity of the laser beam, and the drift light of the laser beam is transmitted in front of the photodetector. A laser beam scanning device characterized by being provided with a refractive optical element that guides the light to a photodetector.