JPH04104658A - Film picture reader - Google Patents

Abstract

PURPOSE:To prevent generation of longitudinal stripes even when a film with dust or dirt adhered thereto is measured by providing a light collection device having a slit along a main scanning direction and making a laser beam transmitted through the film incident in an oblique direction according to the slit to the reader. CONSTITUTION:A rectangular slit 22 whose major axis is along with the main scanning is formed to a light collection device 21 to receive a laser beam transmitted through a film and the laser beam through the slit 22 and made incident in the light collection device 21 is reflected in a wall face of the light collection device 21 and made incident in a detector 12, in which the beam is converted into an electric signal. Since the laser beam is made incident in the inner wall face of the light collection device 21 via the slit 22 in the oblique direction when no film 1 is placed, even if dust or dirt exists, it is fallen down to the bottom and the laser beam is made incident in the inner wall where no dust nor dirt exists. On the other hand, when the film 1 is located, the laser beam transmitted through the film 1 is diffused on the film face and made incident in the light collection device 21, the density is taken lower. Thus, in any case, the effect of dust or dirt is not caused, then no longitudinal stripe is caused.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a film image reading device that reads radiation image information recorded on an image storage medium such as an X-ray film, and more specifically, To provide a film image reading device that does not generate vertical stripes harmful to a doctor's diagnosis even when measuring a film with dirt or dust.

(Prior Art) When making a diagnosis based on an image stored on an image storage medium such as a film, especially an image taken from an After scanning the stored image with a narrowly focused laser beam and converting the transmitted light into an electrical signal, various image processing such as spatial frequency processing and gradation processing is performed to obtain information useful for medical diagnosis. After being emphasized, it is regenerated and used for diagnosis. In this method, one X
More effective diagnostic information can be obtained from radiography, improving diagnostic performance. It is also expected to improve the efficiency of storing and retrieving X-ray films.

FIG. 6 shows the configuration of a diagnostic system employing such a method. An image recorded on a film 1, which is an image recording medium, is read by scanning the film 1 with a laser beam using a film image reading device 2. 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 makes it possible to obtain images with excellent diagnostic suitability.

The display device 4 visualizes the data-processed image.

FIGS. 7(a) and 7(b) are conceptual diagrams of a conventional film image reading device 2 used in such a system.

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, when the beam diameter of the laser beam is expanded five times by the beam expander 6, the spread angle of the laser beam decreases to 115.

Reducing the spread angle of laser light is essential in order to narrow down the beam diameter. Reference numeral 7 denotes an optical deflector that reflects the incident laser beam at a constant angular velocity in the main scanning direction, and a polygon or a galvanometer is generally used. 8 is an fθ lens, and when a laser beam with a constant angular velocity enters,
It serves to keep the linear velocity constant and focus the laser beam on the same plane.

Reference numerals 9a and 9b are film feed rollers, which hold the film 1 on which image information is recorded and run the film 1 at a predetermined speed in a direction approximately perpendicular to the main scanning direction (sub-scanning direction).

The entire surface of the film 1 is scanned by the laser beam by the sub-scanning by the film feed rollers 9a and 9b and the main scanning by the optical deflector 7.

11 is the laser beam that has passed through the film 1 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 this electronic circuit converts the light transmitted through the film 1 into a digital signal in time series in association with the position information of each pixel.

The principle of film density measurement is described below. Let the reference amount of light incident on the detector 12 be IO, the amounts of light incident on the detector 12 without a film and with a film be 1 and 12, respectively, and the densities at that time be D1 and D2, respectively, then the density and The relationship between the amount of light is D, = -logl, /Io, D2 = -1agI2 /I
.

becomes.

At this time, when 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, is calculated, D3=D2-01=-1ogI2/I1, which indicates the density of the film. That is, if you measure and record the density without the film in advance, measure the density D2 with the film placed, and calculate the difference from the previously memorized density D1, the value is This indicates the density D3 of the film.

FIG. 8 shows the electronic circuit of the film image reading device 2. As shown in FIG. Since the concentration has a log dimension as described above, 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 preceding stage in synchronization with a clock signal input from a controller (not shown) that manages the entire electronic circuit.
5 converts the signal held by the sample/hold circuit 14 into a digital signal.

The above controller divides continuous image information into pixels by generating a clock signal corresponding to the main scanning speed. The switch 16 sends the signal output from the A/D converter 15 to the calibration buffer 17 or the rain buffer 18 according to a signal instructed by the controller. That is, the density information when the film 1 is not placed in FIG. 7 is sent to the calibration buffer 17,
The switch 16 operates so that the density information when the film 1 is placed is sent to the line buffer 18.

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. Reference numeral 19 denotes a difference calculation circuit, which calculates the difference between the film density information stored in the line buffer 18 at the previous stage and the density information stored in the calibration buffer 17 for each corresponding pixel using a signal input from a controller (not shown). It has a function to calculate. By calculating this difference, shading correction is performed and the density of the film is calculated. Reference numeral 20 denotes an interface, which functions to send the output signal of the difference calculation circuit 19, that is, the density signal, 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, film feed rollers 9a, 9
b moves the film 1 in the sub-scanning direction to the main scanning line formed by the optical deflector 7.
The density of the line 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, and the difference, that is, the density of the film is calculated, and the calculation result is sent to the data via the interface 20. It is sent to the 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 1 by a predetermined distance in the sub-scanning direction, and the next line is measured. Such operations are performed one after another to measure the entire surface of the film 1.

(Problem to be Solved by the Invention) Conventional film image reading devices can convert film image information into digital density information with high accuracy, but since the film 1 is generally electrically charged, dirt and dust may collect on it. However, when measuring a film that has dirt or dust attached to it, there is a problem that the dirt or dust may enter the optical system.

In particular, if dirt or dust adheres to the light input end face of the condenser 11, it will have a very negative effect on the measurement results.

That is, when a film is measured with dust attached to the light input end face of the condenser 11 and the measurement results are displayed on the display device 4 shown in FIG. It becomes a big hindrance. This vertical stripe must be removed.

The data to be sent to the data processing device 3 is the content of the line buffer 18 in which the density of one line of image is stored in the difference calculation circuit 19 of the electronic circuit shown in FIG. 8, and the density when there is no film is stored. Since the difference in the contents of the calibration buffer 17 is calculated for each pixel, even if dust adheres to the light input end face of the condenser 11, it will be canceled and will not be sent to the data processing device 3. Met. It was unclear why white vertical stripes appear on the display device 4 when dust adheres to the light input end face of the condenser 11.

The present invention has been made in response to the above-mentioned problems.
It is an object of the present invention to provide a film image reading device that does not generate vertical stripes even when measuring a film to which dirt or dust is attached.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the present invention scans an image on a film along the pixels with a laser beam and measures the amount of light transmitted through the image. In a film image reading device that converts the density of an image scanned by a laser beam into a digital quantity corresponding to the position of each pixel, a laser beam is arranged to perform main scanning by irradiating the film surface with a laser beam from an oblique direction. The present invention is characterized by comprising a laser light source having a slit extending along the main scanning direction and a condenser that allows the laser light transmitted through the film to be incident in an oblique direction along the slit.

(Function) When there is no film, the laser light enters the inner wall of the condenser from an oblique direction through the slit.

As a result, even if dirt and dust are present, they are not present on the inner wall surface and fall to the bottom, so that the laser beam is incident on the inner wall surface where dirt and dust are not present. On the other hand, when there is a film, the laser light that has passed through the film is diffused on the film surface and enters the condenser, so the concentration can be kept low.

As a result, vertical stripes do not occur in either case, since they are not affected by dirt or dust.

(Example) Prior to detailed description of the present invention, the principle of the present invention will be explained.

The inventor of the present invention repeatedly conducted various experiments to solve this problem, and found that the white vertical stripes are caused by the fact that when there is no film, the laser beam directly irradiates the dust. Mountains occur, but if there is a film, the laser light that passes through the film is diffused by the film and enters the condenser, so the beam diameter of the laser light that irradiates the dust becomes very thick, and the line buffer 18 They came to the conclusion that this is because only small piles form where there is trash.

This can be explained as follows. Figure 9(a) shows dust 25 on the light input end face of the condenser 11 when there is no film.
FIG. 9(b) shows the contents of the calibration buffer 17 at that time. The horizontal axis shows the distance in the main scanning direction, and the vertical axis shows the density, where the density is high above the vertical axis and low below. In FIG. 9(b), there is no diffusion due to the film, so an extremely sharp peak can be seen at the location of the dust 25. The width of this mountain is determined by the spot diameter of the laser beam and the size of the dust, and the height of the mountain depends on the concentration of the dust.

FIG. 10(a) shows the condenser 11 when the film 1 is present.
10 is a schematic diagram of a case where dust 25 is attached to the optical input end surface of the optical input end face, and FIG. 10 (b) shows the contents of the line buffer 18 at that time. Film 1 for ease of explanation
The image is assumed to be of a certain density and not recorded. The spot diameter of the laser beam that passes through the film 1 and irradiates the dust 25 becomes very large because it is diffused by the film 1, and the spot diameter of the laser beam that passes through the film 1 and irradiates the dust 25 becomes very large. Mountains of low height are occurring.

If there were no diffusion by the film, this mountain would look like a dotted line, and the width and height of the mountain would be equal to those shown in Figure 9(b). Thermal theory In this case, it is assumed that the response of the electronic circuit shown in FIG. 8, especially the frequency response of the log amplifier 13, is sufficiently fast.

FIG. 11 shows the output of the difference calculation circuit 19 obtained by subtracting the calibration buffer 17 from the line buffer 18. Although shading has been corrected, sharp valleys can be seen where there is dust.

The image data displayed on the display device 4 is processed by the difference calculation circuit 19.
Since the difference between the line buffer 18 and the calibration buffer 17 is calculated for each pixel, a sharp valley will appear at the position where there is dust. This becomes a white vertical stripe.

It is clear that the vertical stripes are caused by dust.

Therefore, there is no problem if the film to be measured is dust-free, but since the film attracts dust with static electricity, it is not practical to do so. In particular, it is difficult to require doctors to use only films that are free of dirt and dust. There are strong expectations for preventing vertical stripes from occurring even on films with dust attached.

To measure the density of a film, it is necessary to measure the light transmitted through the film, so the influence of scattering by the film cannot be avoided. That is, it is not possible to make the mountain of dust in FIG. 10(b) have the same waveform as in FIG. 9(b), as indicated by the dotted line. Therefore, it is appropriate to change the pile of dust when there is no film in FIG. 9(b) to the pile when there is a film in FIG. 10(b).

The first measure for this is to keep your distance. That is, in the conventional device, in order to input as much light as possible that has passed through the film, the light input end faces of the film 1 and the condenser 11 are very close to each other, so that the light is directed almost to the imaging position of the fθ lens 8. There will be an input end face. In this case, the laser beam is almost focused on the dust, so if there is no film, sharp peaks will appear as shown in FIG. 9(b). However, if the optical input end face is moved away from the imaging position of the fθ lens 8,
The laser beam with a larger beam diameter will irradiate the dust, and the height of the peak in FIG. 9(b) will become lower.

The beam diameter of the laser beam at a position shifted from the imaging position can be calculated. Now the beam waist has radius r. Assuming that the radius of the beam becomes r at a point 2 away from here, the relationship between r and 2 is r=ro [1+ (λ 2 /π r o 2)
2 ko 1/2. In this formula, if 2 is 80-, then r is r.

This is approximately 2.7 times as large.

Now, the beam diameter of the laser beam is 100 μm, and the diameter of the dust is 1
Assuming 00μ mouth, Fig. 9(b) when 80mm apart.
Since the spot diameter of the laser beam that irradiates the dust becomes about 270 μm, the height of the mountain becomes about 1/4 of that when the dust is at the imaging position. Although this is a huge improvement, it is still not enough.

The second measure is to shift the main scanning position from the position where dust adheres. In this case, the laser light will irradiate the film obliquely. Laser light that has passed through the film and is widely diffused must be efficiently focused.
Conventional light guide systems are not suitable for concentrators because the angle of incidence of light is small.

The present invention has been made from this point of view, and its fundamental feature is that a pipe-shaped condenser having a length along the main scanning direction is used as a condenser.

FIG. 1 is a configuration diagram showing an embodiment of the film image reading device of the present invention, in which 1 is a film to be measured, 5 is a laser oscillator, 6 is a beam expander, 7 is an optical polarizer, and 8 is an fθ lens. is the same as the conventional configuration. Reference numeral 21 denotes a condenser having a pipe shape having a length along the main scanning direction, and a slit 22 extending along the main scanning direction is formed on the surface of the condenser.

23 and 24 are mirrors.

FIG. 2(a) is a perspective view showing the condenser 21, FIG. 2(b) is a plan view, and FIG. 2(c) is a side view. The length of the condenser 21 is longer than the width of the film to be measured, and a rectangular slit 22 along the long axis or main scanning is formed on the film side to receive the laser light that passes through the film. There is. The inner wall surface of the condenser 21, including both side surfaces, is coated with paint that reflects laser light well. The detector 12 is fixed at the center of the condenser 21 with its light detection surface facing toward the inside of the condenser 21 . The laser light that enters the condenser 21 through the slit 22 is reflected by the wall of the condenser 21, enters the detector 12, and is converted into an electrical signal.

As shown in the schematic diagram in Figure 3, during calibration without a film, the laser beam is directed diagonally to the condenser 2.
It is incident on the wall of 1. Even if dust falls to the bottom of the condenser 21, the laser beam will hit the side wall of the condenser 21, so the influence of the dust can be almost ignored. Therefore, sharp peaks as shown in FIG. 9(b) do not occur. Next, when the film is present, the laser light transmitted through the film is diffused by one surface of the film and enters the condenser 21, as shown in FIG. In this case, since the laser beam is in the same state as being very thick, the influence of dust can be ignored, and no peaks as shown in FIG. 10(b) occur.

The above-mentioned paint applied to the inner wall surface of the condenser 21 affects the shading effect.

For example, when the paint is white paint whose main component is titanium oxide, etc., the incident laser beam is reflected with good directionality, so when the laser beam is incident on the periphery of the condenser 21 and when it is incident on the center. In some cases, the intensity of the laser light incident on the detector 12 changes greatly.

When there is no film, the laser light hits the wall of the condenser 21 directly, resulting in a large shading effect. When there is a film, the laser light diffused by the film surface enters, so the shading effect is reduced. It is thicker when there is no film. Therefore, the difference calculation circuit 19 cannot correctly perform shading correction.

If the paint applied to the wall of the condenser 21 can diffuse the incident laser light non-directionally, shading correction can be achieved sufficiently. The paint mainly composed of barium sulfate or the like, which is generally applied to the inside of the integrating sphere, has the property of being able to reflect incident light non-directionally with an extremely high reflectance. By applying this paint to the wall surface of the condenser 21, sufficient shading correction can be performed using the difference calculation circuit.

The diameter of the concentrator 21 also affects shading correction. The sensitivity of the detector 12 in the direction of the incident angle is expressed as a cosine. The larger the diameter of the collector, the smaller the shading effect.

According to experiments, if the diameter of the condenser is about 70 mm, shading correction can be sufficiently performed using the difference calculation circuit. The width of the slit 22 is also an important factor that determines the performance of the condenser 21. If the width of the slit 22 is too wide, a large amount of the laser light incident on the condenser 21 will escape to the outside of the condenser. On the other hand, if it is too narrow, the laser light diffused on the film surface will not be able to enter the inside of the condenser 21 sufficiently.

Since the laser light emitted from the film is diffused by the film, it has a nearly spherical directivity characteristic as shown in FIG. If light can be received in a conical range of about 60 degrees on one side from the emission point of the film, more than 90% of the light transmitted through the film can be received.

If the inner wall surface of the condenser 21 is installed as close as possible to the film 1, the width of the slit 22 will be equal to the width of the condenser 2.
Determined by the thickness of 1. If the thickness of the condenser 21 is, for example, 1 mm, the width of the slit 22 will be 10 mm if the light can be received in a conical range of about 60 degrees on one side from the emission point of the film 1.
mm, and if the diameter of the condenser 21 is 70 mm, the ratio of the slit 22 to the circumference of the condenser 21 is about 5%, and the amount of light escaping from the condenser 21 is almost negligible.

In the configuration shown in FIG. 1, the laser beam emitted from the laser oscillator 5 is changed in direction by a mirror 23 and then enters the beam expander 6. The beam expander 6 thickens the beam diameter to an appropriate thickness and reduces the spread angle. The laser beam is reflected by the optical deflector 7 rotating at an equal angle and enters the fθ lens 8. In the drawing, the optical deflector 7 uses a polygon drawing.The laser beam that has passed through the fθ lens 8 is reflected by a rectangular mirror 24, forms an image on the film 1, and moves the film 1 at a constant linear velocity. Scan. The mirror 24 can adjust the angle of the laser beam that irradiates the film 1. If there is no film 1, the laser beam will be directed to the mirror 24.
After being reflected, the light directly enters the condenser 21. The laser beam transmitted through the film 1 enters the condenser 21 through the slit 22, is reflected omnidirectionally on the wall of the condenser 21, and then enters the detector 12 where it is converted into an electrical signal.

In actual measurement, calibration is first performed. That is, the amount of light for one line when there is no film 1 is measured and stored in the calibration buffer 17 shown in FIG. Next, a film feed mechanism (not shown) operates to move the film 1 to the main scanning position, and the amount of light for one line transmitted through the film 1 is measured.
Sent to 8th. The contents of the line buffer 18 and the contents of the calibration buffer 17 are sent one after another to the difference calculation circuit 19 in synchronization with the clock signal, and the difference for each pixel is calculated and sent to the subsequent data processing device. When the density of one line of the film 1 has been transferred to the data processing device, the film transport mechanism (not shown) is activated to move the film 1 a predetermined distance and measure the next line. . In this way, the entire surface of the film 1 is measured.

Film 1 is generally charged, so static electricity collects dust 2.
5 or dust is attached. In the unlikely event that dust 25 falls on the concentrator 21
Even if the debris 25 falls into the condenser 21, the fallen debris 25 will accumulate at the bottom of the condenser 21. Since the laser beam is designed to irradiate the film 1 obliquely, if the laser beam is directly incident on the condenser 21 without the film 1 during calibration, the laser beam should be directed so that it hits the wall on the side of the condenser 21. Since it is solid, it is not affected by the dust 25 at all. Even if extremely fine light dust sticks to the side wall of the condenser 21, for example, the influence of such dust can be ignored since that is not the focal point of the laser beam and the beam diameter is widened. It will be possible.

FIG. 5 shows the shape of a condenser 21 according to another embodiment of the present invention, in which one end surface 21A is formed into a curved shape along the main scanning direction, and the other end surface 21B is formed into a straight shape. It is something. Even with such a shape, the same effects as in the embodiment described above can be obtained.

[Effects of the invention] As described above, according to the present invention, the influence of dirt and dust attached to the condenser is eliminated, so even if a film with dirt or dust attached is measured, it will not be harmful to diagnosis. It is possible to prevent the occurrence of vertical stripes.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing an embodiment of the film image reading device of the present invention, and Fig. 2 (a), (b), and (c) are perspective views illustrating a condenser used in the device of this embodiment. , a plan view and a side view, FIG. 3 is a schematic diagram explaining the incident state of laser light when there is no film, FIG. 4 is a schematic diagram explaining the incident state of laser light when there is a film, and FIG. 5 is a perspective view showing a concentrator according to another embodiment of the present invention, FIG. 6 is a block diagram showing a diagnostic system, and FIGS. 7(a) and (b) are conceptual diagrams showing a conventional film image reading device. Fig. 8 is a block diagram showing the electronic circuit connected to the film image reading device, and Figs. 9 (a) and (b) are explanatory diagrams of the case where dust is attached to the condenser, and in this case, the light Figures 10 (a) and (b) are diagrams of the concentration distribution when light is incident, and explanatory diagrams when the film is placed on the condenser through dust, and in this case, light is incident. Concentration distribution map of time, 1st
FIG. 1 is a concentration distribution diagram showing the output of the difference calculation circuit of FIG. 1... Film, 12... Detector, 17... Calibration buffer, 18... Line buffer,
19... Difference calculation circuit, 21... Concentrator, 21A.
...Curved surface, 21B... Straight surface, 22... Slit, 25... Dust. Agent Patent Attorney Noriyuki Chika
Takeshi Kondo Fig. 2 Fig. 25 Komi L tos' light ＼ (bl Fig. Fig. main scanning and deviating details (b) Fig. King, Hosenho l dialect both 1 (bl Fig. main scanning 3 @ Zhongmei Diagram

Claims (6)

[Claims] (1) By scanning the image on the film along the pixels with a laser beam and measuring the amount of light transmitted through the image, the density of the image in the area scanned by the laser beam is converted into a digital quantity corresponding to the position of each pixel. In the film image reading device to be converted, there is a laser light source arranged to perform main scanning by irradiating laser light onto the film surface from an oblique direction, and a laser light that has a slit along the main scanning direction and passes through the film. 1. A film image reading device comprising: a condenser that allows the light to enter in an oblique direction along a slit. (2) The film image reading device according to claim 1, wherein the condenser has a pipe shape that is elongated along the main scanning direction. (3) Claim 1, wherein the condenser has one end surface formed in a curved shape along the main scanning direction, and the other end surface formed in a straight shape.
The film image reading device described above. (4) The film image reading device according to any one of claims 1 to 3, wherein the inner wall surface of the condenser is coated with a paint that reflects incident light with high reflectance. (5) The film image reading device according to any one of claims 1 to 4, wherein the condenser is arranged close to the film to be measured. (6) The film image reading device according to claim 2, wherein the pipe has a diameter of 70 mm or more.