JPH01177263A - Laser beam projecting device - Google Patents

Abstract

PURPOSE:To obtain a laser beam projecting device improving the picture quality of a reading picture by reducing a tailing component involved to a laser beam. CONSTITUTION:The laser beam projecting device 25 consists of a laser oscillator 5, a beam expander 6, a tailing removing means 30, a high speed angle changing mirror 7 and ftheta lens 8. The tailing removing means 30 removes a tailing comonent involved to a laser beam is provided between the beam expander 6 and the high speed angle changing mirror 7, and is formed in a truncated angular cone shape with combining four members 31-34 of a trapezoid shape. Then, the members 31-34, a material which can obstruct the transmission of the laser beam is applied. Thus, since the tailing component is reduced by providing the tailing removing means 30 and obstructing the transmission of the tailing component involved to the laser beam, the picture quality of a reading picture can be improved.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides a method for writing image information on an image recording medium or reading out image information from the image recording medium. The present invention relates to a laser beam irradiation device used to irradiate laser beams to objects.

(Prior art) In the past, images stored on film, especially images from X-ray film, were placed on a Scherkasten or similar device and diagnosed directly with the naked eye. After scanning with light and converting it into an electrical signal, various types of image processing such as spatial frequency processing and gradation processing are performed to emphasize information useful for medical diagnosis, and then the information is reproduced for diagnosis.

With this method, more diagnostic information (1q) can be obtained from one X-ray i-image, improving diagnostic performance. Furthermore, it is also expected to improve the efficiency of storing and retrieving X-ray image information.

The system configuration diagram shown in FIG. 5 will be explained as follows. The image stored on the film 1 is read by the film image reading device 2 by scanning the film 1 with a laser beam. This read information is sent to the data processing device 3 after being converted into a digital signal. The data processing device 3 performs data processing such as frequency emphasis and edge emphasis on the sent image information. This provides images with excellent diagnostic suitability. The display device 4 visualizes the data-processed image.

FIGS. 6(a) and 6(b) show a conventional film image reading device 2.
It is a conceptual diagram. 5 is a laser oscillator that generates a laser beam, and 6 is a beam expander that expands the aperture of the incident laser beam to an arbitrary size to reduce the spread angle of the laser beam.

For example, the beam diameter of the laser beam can be set to 5 by the beam expander 6.
When magnified twice, the spread angle of the laser beam decreases to 115.

Reference numeral 7 designates a high-speed angle change mirror that reflects the incident laser light in the main scanning direction at a constant angular velocity, and a galvanometer or polygon is generally used.

Reference numeral 8 denotes an fθ lens, which serves to focus the laser beam on the same plane by keeping the linear velocity constant when the laser beam is incident at a constant angular velocity.

Reference numerals 9a and 9b are film feed rollers, which hold the film 10 on which image information is stored and run the film 10 at a predetermined speed in a direction perpendicular to the main scanning direction (sub-scanning direction).

The entire surface of the film 10 is scanned by the laser beam by the sub-scanning by the film feed rollers 9a and 9b and the main scanning by the high-speed angle change @7.

11 is a laser beam that has passed through the film 10 and entered,
It is a condenser that guides the light to the detector 12 that converts it into an electric signal, and includes an optical system such as a bundled optical fiber and a lens.
A transparent acrylic resin or the like whose output end is processed so as to efficiently transmit incident light to the detector 12 is used.

An electronic circuit is connected after the detector 12, and in this electronic circuit, the light that has passed through the film 10 is correlated with the position information of each pixel and converted into a digital signal in time series.

The principle of film density measurement is as follows.

The reference amount of light incident on the detector 12 is Io, the amount of light incident on the detector 12 when there is no film and when there is a film is T1 and I2, respectively, and the density at that time is D1.
and D2, the relationship between density and light amount is Dl = -l
0g11/Io, D2=-10(]I2/Io.

At this time, if we calculate the density D3, which is the difference between the density D2 when there is a film and the density D1 when there is no film, we get D3
=D2-Dl =-10(lI2/It,
This indicates the density of the film.

That is, if you measure and memorize the density D1 when there is no film in advance, then measure the density D2 when the film is placed, and calculate the difference between it and the previously memorized density, that value will be the same as that of the film. This indicates the density D3.

FIG. 7 shows the electronic circuit of the film image reading device 2. As shown in FIG. As described above, since the concentration has a log dimension, the signal converted into an electrical signal by the detector 12 is first converted into a log signal by the log amplifier 13.

The sample/hold circuit 14 holds the output signal of the log amplifier 13 in the previous stage in synchronization with a clock signal input from a controller (not shown) that manages the entire electronic circuit. converts the signal held by the sample/hold circuit 14 into a digital quantity.

The above controller divides continuous image information into pixels by generating a clock signal corresponding to the main scanning speed. The switch 16 converts the signal output from the A/D converter 15 into a calibrator buffer 17 or a line buffer 18 according to a signal instructed by the controller.
send to When the switch 16 is pressed, the density information when the film 1Q is not placed in FIG. 5 is sent to the calibration buffer 17, and the density information when the film 10 is placed is sent to the line buffer 1B. works.

Calibration buffer 17 and line buffer 18
is a circuit that functions to store digital signals of the number of pixels for one line, and advances the storage address by a clock signal input from a controller (not shown) to associate pixel position information with stored information.

19 is a difference calculation circuit, which is connected to the line buffer 18 at the previous stage.
It has a function of calculating the difference between the density information of the film stored in the film and the density information stored in the calibration buffer 17 for each corresponding pixel using a signal input from a controller (not shown). This difference becomes the density of the film.

Reference numeral 20 denotes an interface, which functions to send the output signal of the difference calculation circuit 19 to the data processing device 3.

In the above configuration, first, the density of one line when there is no film is measured, and this is stored in the calibration buffer 17. Next, the film feed roller 9a
, 9b move the film 10 in the sub-scanning direction to the high-speed angle change mirror 7.
As a result, the density of one line with the film is measured, and the measured value is stored in the line buffer 18.

Thereafter, by the action of a controller (not shown), the contents of the calibration buffer 17 and line buffer 18 are sent one after another to the difference calculation circuit 19, the difference, that is, the density of the film is calculated, and the calculation result is sent via the interface 20. The data is sent to the data processing device 3.

After one line of data is transferred to the data processing device 3, the film feed rollers 9a and 9b move the film 10 by a predetermined distance in the backward scanning direction, and the next line is measured. Such operations are performed one after another, and the entire surface of the film 10 is measured.

Incidentally, as shown in FIG. 6, dirt and dust tend to adhere to the film 10, and the dirt and dust attached to the film 10 may enter the optical system. In particular, if dirt or dust adheres to the light incident end face of the condenser 11, it will have a very negative effect on the measurement results. That is, if a film is measured with dust or the like attached to the light incident end face of the condenser 11 and the measurement results are displayed, vertical stripes will occur. This poses a major obstacle to image diagnosis. The cause of the occurrence of this vertical stripe is considered to be a delay in the response of the log amplifier 13 for the reasons described below.

By the time (e.g. 11 Js) to divide the image into pixels,
If a log amplifier that cannot rise to a predetermined concentration output is used, the following will occur. In this case, log amplifier 13
The time it takes for the film to rise to a predetermined density becomes slower as the density of the base of the film increases. That is, if the concentration of dust is, for example, density 2, the time it takes for the base to rise from a state where there is no film (in this case, the density is approximately O) to the density of dust (fi degree 2) is such that the base has a constant density ( For example, it is shorter than the time it takes to rise from a film with a density of 1) to a dust density (in this case, a density of 3). In other words, the concentration that rises within a certain period of time (eg, 11 Js) is higher when the base concentration is low than when the base concentration is high.

This will be explained as follows with reference to FIGS. 8(a) to (C). In the same figure (a), there is dust 2 on the light incident end face of the condenser 11.
It shows the state in which 1 is attached and the change in its concentration. The same figure (b) shows the state in which the film is inserted in the same figure (a).

The concentration H1 due to the dust 21 when the base concentration is approximately O in FIG. 2A is larger than the concentration H2 when the base concentration is 1 in FIG. 2B. As mentioned above, the density information shown in FIG.
Since the value of the calibration buffer 17 is subtracted for each pixel from
This becomes a signal with 82 signals on it, and this becomes a vertical stripe.

In order to solve the above-mentioned problems, the inventor of the present invention has developed a log amplifier that has a dynamic range that exceeds the concentration range of concentration information, and a frequency response that is less than the time required to convert the concentration into a digital signal per pixel. (Special application 1986-
079952).

However, when this log amplifier was incorporated into a device and its overall performance was evaluated, the frequency response was greatly improved, but still did not reach the desired value.

In order to sufficiently prevent the occurrence of vertical stripes, it is not enough to improve the performance of the log amplifier alone, and there is still room for further improvement.

The inventor of the present invention repeatedly conducted various experiments to investigate the cause of the occurrence of vertical stripes, and found that the cause lies in the waveform of the laser beam. That is, the profile of the laser beam output from the laser oscillator 5 has a Gaussian distribution as shown in FIG.

The spot diameter of the laser beam is 1/e2 of the maximum intensity of the laser beam.
This is the diameter of 13.5% of the maximum strength.

Now, the sampling pitch, which is the interval between pixels that divides the image into pixels, is 100 μm, and the main scanning spot diameter is fθ
Assume that the lens is focused to 100 μm. Figure 9 shows the state when scanning is performed using a laser beam with a spot diameter of 100 μm at a sampling pitch of 100 μm in both the main scanning direction and the sub-scanning direction, and each circle indicates the area read by one sampling. ing.

As is clear from FIGS. 9 and 10, the sampled value is the spot diameter (beam diameter) of the laser beam I! It is a value obtained by weighting the density of the area irradiated with 1 by Gaussian distribution.

Assuming that main scanning is performed from left to right in Figure 10,
It can be seen that the laser beam, which is longer than the spot diameter, has already irradiated a pixel preceding the target pixel. That is, the first
When a film 10 with a constant density is placed on the condenser 11 as shown in Fig. 1(a), a change in density as shown in Fig. 1(b) should normally be detected, but the laser Since the light has a Gaussian distribution, the so-called "tailing" of the laser light causes the actually detected waveform to become as shown in FIG. That is, no matter how fast the frequency response of the log amplifier is made, as long as the intensity distribution of the laser light irradiating the film 10 has a Gaussian distribution, there is a limit to the overall improvement of the frequency response.

Considering that the intensity of laser light transmitted through a film with a density of 4 is 1/10,000 as compared to a film with a density of 0, the trail of the laser light is extremely long. Even if the spot diameter is made extremely small relative to the sampling pitch, very long tails occur, so no significant effect can be expected. Also, considering that the width of the actual film is 14 inches, the spot diameter is 8 inches with the fθ lens 8.
It can only be narrowed down to about 0 μm.

(Problems to be Solved by the Invention) As described above, there is a limit to the overall improvement of frequency response in film image reading devices, for example, due to the trailing component contained in laser light.

SUMMARY OF THE INVENTION The present invention aims to eliminate the above-mentioned drawbacks, and its purpose is to provide a laser beam irradiation device that improves the quality of read images by reducing trailing components contained in laser beams. be.

[Structure of the Invention] (Means for Solving the Problems) The present invention writes image information onto or extracts image information from the recording medium by irradiating the image recording medium with a focused laser beam. In a laser beam irradiation device that enables reading out image information, a laser beam transmission hole is formed of a member capable of blocking transmission of the laser beam, and the laser beam transmission hole prevents the transmission of trailing components contained in the laser beam. A tailing removal means is provided for removing the trailing component by blocking it at other parts.

(Function) In the present invention, the above-mentioned tailing removal means is provided to prevent the transmission of the trailing component contained in the laser beam, thereby reducing the trailing component.

(Example) Hereinafter, the present invention will be explained in detail with reference to Examples.

FIGS. 1(a) and 1(b) show an embodiment of the present invention, in which the present invention is applied to a film image reading device. In the figure, the laser beam irradiation device 25 includes a laser oscillator 5. Beam expander 62 tail removal means 30
．． It has a high-speed angle change mirror 7° fθ lens 8.

In addition, FIG. 6(a) in FIGS. 1(a) and (b).

Components having the same functions as those shown in (b) are given the same reference numerals, and detailed explanation thereof will be omitted.

The apparatus of this embodiment differs from the conventional apparatus shown in FIGS. 5(a) and 5(b) in that it includes a tail removal means 30.

This tailing removal means 30 removes trailing components contained in the laser beam, and is provided between the beam expander 6 and the high-speed angle change mirror (eg, galvanometer or polygon) 7.

FIG. 2(a) is a perspective view showing a specific configuration of the tailing removal means 30, and the figure (b> is taken along the line AA' in the same figure (a>).
FIG. As shown in the figure, this tail removal means 3
0 is formed into a truncated pyramid shape by combining four trapezoidal members 31, 32, 33, and 34. Part 3
1 to 34 are those capable of blocking the transmission of laser light. In this embodiment, mirrors are used as the members 31 to 34. The reflective surfaces of the mirrors 31 to 34 serve as the outer wall surface of the tail removal means 30. A square laser beam transmission hole 35 is formed by the combination of these four mirrors 31 to 34. The laser beam emitted from the beam expander 6 in FIG. For example, when the beam diameter of the laser beam emitted from the beam expander 6 is 5#, the diameter 12 of the laser beam transmission hole 35 is set to 5 m. One end surface 36 of the mirror forming the transmission hole 35 is formed to be parallel to the incident laser beam, and the mirror tip 38 is a knife edge.

This is due to the need to suppress diffraction of the incident laser beam as much as possible.

Next, the operation of the embodiment device configured as described above will be explained.

A laser beam (with a beam diameter of 1 beam) emitted from the laser oscillator 5 has its beam diameter expanded five times by the beam expander 6, and then enters the trailing removal means 30. FIG. 3 is an explanatory diagram of the operation of the tail removal means 30. A laser beam trailing component whose diameter exceeds 2 in the diameter of the laser beam transmission hole 35 is reflected by the mirror surface as shown by a dashed line 39, and therefore does not enter the high-speed angle change mirror 7. The tailing component reflected by the mirror surface does not directly return to the laser light source (here, meaning the beam expander 6 side) because the incident angle of the trailing component to the mirror surface is acute; It is preferable to provide a laser beam absorbing member to absorb the laser beam. FIG. 40 shows the profile of the laser beam that has passed through the laser beam transmission hole 35, and it can be seen that the waveform has been shaped by removing the trailing component. Since the laser beam transmission hole 35 is square (see FIG. 2(a)), correspondingly, the laser beam incident on the high-speed angle change mirror 7 also has a square shape as shown in FIG. 41.

The laser beam reflected by this high-speed angle change mirror 7 is f
The beam is narrowed down to a predetermined beam diameter (100 μm in this case) by a θ lens 8, and is irradiated onto a film 10 (see FIGS. 1(a) and (b)), which is an image recording medium.

FIG. 4 shows the state when the film 10 is scanned with the laser beam. As shown in FIG. 42, the laser beam irradiation field is square, and in the main scanning direction and the sub-scanning direction, pixels other than the target pixels are hardly irradiated with the laser beam. Therefore, such laser light irradiation is extremely advantageous in improving image quality compared to conventional circular irradiation (see FIG. 10).

In this way, in the device of this embodiment, the tailing removal means 3
0, film 1 is processed using laser light with tailing components removed.
0, the overall frequency response is high, and even if dirt or dust is brought into the device by the film and adheres to the light incident end surface of the condenser 11, it will be difficult for a doctor to diagnose. There are no vertical stripes that interfere with
A read image with good image quality can be obtained.

Although one embodiment of the present invention has been described above, it goes without saying that the present invention is not limited to the above embodiment, and various modifications can be made.

Although the above embodiment describes the case where the present invention is applied to a film image reading device, the present invention can also be applied to other devices. For example, a phosphor sheet (also called an imaging plate) comprising a stimulable phosphor
The present invention can also be applied to a radiation image reading device that reads radiation image information recorded on the phosphor sheet by irradiating the phosphor sheet with laser light. In addition, image information is written on the film by irradiating the film with a laser beam whose light intensity is modulated by an image signal, with main scanning by a deflection means such as a polygon, and sub-scanning perpendicular to the main scanning. The present invention can also be applied to image recording devices and the like. Irradiation with laser light from which trailing components have been removed is extremely effective in improving image quality not only in film image reading devices, but also in the above-mentioned radiation image reading devices, image recording devices, and the like.

In the above embodiment, the laser beam is irradiated in a square shape, but the shape is not limited to this. For example, even if the laser beam transmission hole 35 is made circular and the laser beam is irradiated in a circular shape, tailing may not occur. Reduction of components is possible and may achieve the objectives of the present invention.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide a laser beam irradiation device that improves the image quality of a read image by reducing the trailing component contained in the laser beam.

[Brief explanation of the drawing]

FIG. 1(a) is an explanatory diagram of one embodiment of the present invention, FIG. 1(b)
) is a side view of the main part of Figure 2(a), and Figure 2(a) is a side view of the main part of Figure 2(a).
) is a perspective view showing the detailed configuration of the tailing removal means in the apparatus of this embodiment, FIG. 2(b) is a sectional view taken along line AA' in FIG. Action diagram, 4th
The figure is an explanatory diagram of the scanning state in the device of this embodiment, FIG. 5 is a block diagram of the configuration of the image processing device, FIG. 6(a) is an explanatory diagram of a conventional film image reading device, and FIG. 6(b) is the same diagram. (a) is a side view of the main parts, FIG. 7 is a block diagram of the configuration of the electronic circuit in the film image reading device, and FIGS. 8 (a), (b), and (c) are explanations of the occurrence of vertical stripes in the conventional device. Fig. 9 is an explanatory diagram of the intensity distribution of the laser beam, Fig. 10 is an explanatory diagram of the scanning state in the conventional device, and Fig. 11 (a)
. (b) and (C) are diagrams illustrating the limits of overall frequency response improvement in the conventional device. DESCRIPTION OF SYMBOLS 10... Film (image recording medium), 25... Laser light irradiation device, 30... Trailing removal means, 35... Laser light transmission hole. Figure 5 (a) (b) To Figure 6 Figure 7 (C)

Claims (1)

[Claims] In a laser light irradiation device that makes it possible to write image information on or read image information from an image recording medium by irradiating the image recording medium with a focused laser beam, the transmission of the laser light is reduced. Tailing removal, which is formed with a laser beam transmission hole by a member capable of blocking the laser beam, and removes the trailing component contained in the laser beam by blocking the transmission of the trailing component in a portion other than the laser beam transmission hole. A laser beam irradiation device characterized by being provided with means.