JPH07121051B2 - Film image reader - Google Patents

Description

The present invention relates to a film image reading apparatus for reading a film photographed by an X-ray apparatus or the like as image information and displaying it on a screen, and more particularly, The present invention relates to an improvement in the shape of a light receiving unit that prevents vertical stripes and horizontal stripes that occur on an image when dust or dirt adheres to a film or a light receiving unit.

(Prior Art) For example, when a doctor diagnoses a patient while looking at an X-ray film, the X-ray film is placed on a Schaukasten (film observation device) and the film is observed directly by visual observation. . However, as image processing technology progresses, in recent years, images recorded on film are scanned with a laser beam that is narrowed down and the transmitted light is converted into an electrical signal before spatial frequency processing or gradation processing. Various kinds of image processing such as the above have been performed to emphasize information effective for medical diagnosis, and then reproduced to be used for diagnosis. With this method, one X
More effective diagnostic information can be obtained from the radiograph than before, and the diagnostic performance is improved. Furthermore, it is expected to improve the efficiency of storage and retrieval of X-ray films.

FIG. 7 shows a conventional example of such a film image reading apparatus, in which the course of the laser light emitted from the laser oscillator 1 is changed by the mirror 2 and enters the beam expander 3.

The beam expander 3 reduces the divergence angle of the incident laser light. If the beam diameter of the laser light is ω, the wavelength is λ, and the divergence angle is θ, the divergence angle θ≈λ / πω.
For example, if the beam diameter of the laser light is expanded five times with the beam expander 3, the spread angle of the laser light is reduced to about 1/5.

Then, the laser light having the reduced spread angle is incident on the side surface of the polygon 4. As shown, the polygon 4 has an octagonal columnar shape and rotates at a constant angular velocity. Therefore, the reflection angle of the laser light incident on the side surface changes according to the rotation of the polygon 4, and the main scanning is performed.

The fθ lens 5 serves to make the linear velocity of the laser light emitted from the polygon 4 constant, at the image forming position on the main scanning line, and the laser light emitted from the fθ lens 5 is reflected by the mirror 6. Then, after passing through the film 7, the diffuser 8
Incident on.

The diffuser 8 has a rectangular incident surface shape along the main scanning direction, non-directionally diffuses the laser light which is transmitted through the film 7 and is incident, and the diffused laser light is photoed through the light guide 9. Introduce to Maru 10.

The photomultiplier 10 converts the laser light guided by the light guide 9 into an electric signal, and the obtained electric signal is supplied to an electronic circuit described later, and this electronic circuit allows the light transmitted through the film 7 to be emitted. Image data is generated by being converted into a digital signal in time series in association with the position information of each pixel. The light guide 9 is made of a bundle of optical fibers or a transparent acrylic resin.

Further, the film 7 is sent from the diffuser 8 side to the photomultiplier 10 side (in the direction of the arrow in the figure) at a constant speed on the upper side of the diffuser 8 by a roller (not shown), and thereby the sub-scanning is performed. That is, the entire film 7 is scanned by the main scanning by the polygon 4 and the sub-scanning by feeding the film 7.

In the film image reading apparatus configured as described above,
The principle of measuring the film density will be described below.

Let Io be the reference light quantity incident on the Photomalu 10, and let the light quantities incident on the Photomalu 10 with and without the film 7 on the diffuser 8 be I ₁ and I ₂ , respectively, and the densities at that time be D ₁ respectively. , D ₂ , the relationship between the density and the light amount is given by the following equations (1) and (2).

D ₁ = −1ogI ₁ / I ₀ (1) D ₂ = −1ogI ₂ / I ₀ (2) From the equations (1) and (2), the density when the film 7 is present
Density difference between D ₂ and density D ₁ without film 7
D ₃ is calculated by the following equation (3).

_{D 3 = D 2 -D 1 =} -1ogI 2 / I 1 ... (3) Then, the density difference D ₃ indicates the density of the film 7. That is, the density D ₁ when the film 7 is not present is measured and recorded in advance, and the density when the film 7 is placed is recorded.
After measuring D ₂ , the difference from the stored density D ₁ is calculated, and the calculated value indicates the density of the film 7.

FIG. 8 is a functional block diagram of an electronic circuit connected to the post-process of Photomul 10, in which the density of the film 7 is obtained.

As described above, since the density has a logarithmic dimension, the electric signal output from the photomultiplier 10 is converted into a logarithmic dimension by the log amp 11, and the light intensity signal is converted into a density signal, and then the sample / It is supplied to the hold circuit 12. The sample / hold circuit 12 holds the output signal of the log amplifier 11 at the preceding stage in synchronization with a clock signal given from a controller (not shown) that controls the entire electronic circuit, and is an A / D converter. Reference numeral 13 converts the signal held by the sample / hold circuit 12 into a digital signal. Then, of the output signals of the A / D converter 13, the density signal when the film 7 is not placed is input to the calibration buffer 15, and the density signal when the film 7 is placed is input to the line buffer 16. Memorized separately. At this time, the input buffers 15 and 16 are switched by the switch 14 under the control of a controller (not shown). Then, the difference calculation circuit 17 calculates the difference between the density signal stored in the line buffer 16 and the density signal stored in the calibration buffer 15 to obtain the density of the film 7.

Then, the obtained density signal of the film 7 is output to a data processing device (not shown) via the interface 18 and imaged.

FIG. 9A is a view of the diffuser 8 and the light guide 9 as seen from the feeding direction of the film 7, and shows the state in which the film 7 is not present. Now the dust on the diffuser 8
When 19 adheres, the density signal obtained as a result of the main scanning by the laser light has a high density only in the portion where the dust 19 adheres, and therefore, only the position corresponding to the dust 19 is extremely large as shown in FIG. growing. Therefore, this density signal is stored in the calibration buffer 15 shown in FIG.

On the other hand, as shown in FIG. 10 (A), when the film is placed on the diffuser 8 with the dust 19 adhering thereto, the density signal by the main scanning becomes as shown by the solid line in FIG. 10 (B). That is, since the laser light is diffused due to the presence of the film 7, the density signal in the portion where the dust 19 is present is not as local as when the film 7 is not present, and becomes a smooth mountain that spreads somewhat laterally. Note that, here, for ease of explanation, no image is recorded on the film 7. And
The density data shown by the solid line in FIG. 10 (B) is recorded in the line buffer 16 in FIG.

After that, the difference calculation circuit 17 calculates the difference between the recording data of the line buffer 16 and the storage data of the calibration buffer 15, so that the density signal as shown in FIG. 1 is obtained. That is, the dust 19 adheres to the diffuser 8 to cause a sharp valley in the concentration signal.

This phenomenon similarly occurs in all main scans, and as a result, there is a problem that white vertical stripes occur in the film image displayed as an image.

Further, FIG. 12 is a sectional view of the diffuser 8 and its peripheral portion as viewed from the main scanning direction side. As shown in the figure, the laser light 20 reflected by the mirror 6 is incident on the film 7 in an oblique direction in order to prevent interference with the reflected light by the film 7. At this time, the laser light 20 is set so as to enter the diffuser 8 substantially at the center thereof, but the laser light 20 is always in the diffuser because each side surface of the polygon 4 shown in FIG. It does not always enter the central portion of No. 8. That is, the polygon 4 has eight side faces, and when the reflection angle slightly changes for each side face due to the presence of the surface inclination, the central portion of the diffuser 8 is shown by the dotted line of the laser beam 20 in FIG. The laser light 20 will be incident at a position somewhat away from the body.

As a result, the amount of light incident on the diffuser 8 changes for each reflecting side surface of the polygon 4, which causes a problem that horizontal stripes occur in image data obtained by capturing this light.

(Problems to be Solved by the Invention) As described above, in the conventional film image reading apparatus,
If the dust 19 adheres to the diffuser 8, white vertical stripes are generated on the image, which is a drawback. Also, polygon 4
If the side surface of the diffuser has a tilt, the position of the laser light incident on the diffuser 8 changes, so that the amount of incident light changes and horizontal stripes occur on the image.

The present invention has been made to solve such a conventional problem, and an object thereof is to prevent the generation of vertical stripes and horizontal stripes even when dust is attached or polygons are tilted. It is to provide a film image reading device.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention irradiates a laser beam to scan an image on a film, and collects transmitted light of the film by a light receiving means. After that, in the film image reading apparatus which converts the electric signal by the photoelectric conversion means and reads the image on the film as the electric signal, the light receiving means is the light-shielding incident chamber, and the film is formed in the incident chamber. It is characterized by having an opening through which the transmitted light enters, and a converging unit that is formed in the entrance chamber and reflects / focuses the light incident through the opening toward the photoelectric conversion means.

(Operation) With the above-described configuration, even if dust enters from the opening of the light receiving unit, it is extremely rare that the dust adheres to the laser light incident position. It is rarely received, and even if dust adheres to the incident position, the laser light image formation position and the incident position are sufficiently separated from each other. The diameter is enlarged. Therefore, the change of the density signal due to the dust is almost negligible.

Further, since the laser light applied to the film enters the light receiving means through the opening after being diffused by the film, even if the incident position of the laser light slightly changes due to the surface tilt of the polygon, it is affected by this. There is no such thing.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of a film image reading apparatus to which the present invention is applied. The same parts as those in FIG. 7 described in the prior art are designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 1, a box-shaped hollow light-receiving portion 23 is provided on the lower side of the film 7, and a wall surface inside the light-receiving portion 23 is coated with a paint that reflects the laser light omnidirectionally. Also,
A photomultiplier 10 is attached to the side surface 23a of the light receiving portion 23 on the side where the film 7 is sent out at a substantially right angle thereto, and a side surface 23b facing the side surface 23a is formed by an arcuate curved surface.

Further, a slit 22 is formed along the main scanning direction on the side surface 23b side of the upper surface of the light receiving portion 23, and the laser light reflected by the mirror 6 enters the light receiving portion 23 through the slit 22,
This incident light is reflected / focused by the arcuate side surface 23b and is sent to the photomultiplier 10.

FIG. 2 is a cross-sectional view of the apparatus of this embodiment as viewed from the main scanning direction. The laser light main-scanned by the polygon 4 passes through the fθ lens 5 and is reflected by the mirror 6 and is obliquely directed to the film 7. Incident. Then, the laser light transmitted through the film 7 is incident on the arc-shaped curved surface 23b of the light receiving portion 23, is reflected and focused, and is then condensed by the photomultiplier 10.

Now, even if dust 19 enters the light receiving portion 23 from the slit 22 and adheres to the bottom surface of the light receiving portion 23, the laser light enters the slit 22 in an oblique direction and enters the arc-shaped side surface 23b. The laser light is extremely rarely directly incident on the dust 19, and is hardly affected by the dust 19.

Even if the dust 19 unfortunately adheres to the incident position 24 of the laser light, the incident position 24 is sufficiently distant from the position where the laser light passes through the film 7, so that the beam diameter is expanded. Therefore, the influence of dust 19 can be almost ignored.

Also, there is a mess on the side surface of the polygon 4, and the film 7
Even when the position of the laser beam incident on the laser beam is shifted, this laser beam is diffused by transmitting through the film 7, and the light receiving section 23
Since the light is reflected omnidirectionally inside and is taken into the Photomalu 10, the amount of light taken into the Photomalu 10 is hardly affected by the surface tilt of the polygon 4. Therefore, even if the polygon 4 has a surface tilt, horizontal stripes do not occur on the image.

Next, the relationship between the dimensions of the light receiving section 23 and the condensing characteristics of laser light will be described. In FIG. 3 (A), the light receiving portion 23 is formed on the film 7
FIG. 4 is a cross-sectional view as seen from the feeding direction of the. “In this example, the width L1 of the light receiving unit 23 (hereinafter, referred to as“ main scanning direction length ”) is configured to be slightly longer than the width L3 of the film 7. Further, the laser light for irradiating the film 7 is obliquely incident in the main scanning direction as shown in the figure. For this reason,
When the corner 25 of the light receiving portion 23 is close to the end portion of the film 7, the laser light is incident on the corner 25. Further, since the corner 25 has a lower reflection efficiency than other incident positions, the density signal of the received light is at the end of the light receiving portion 23 at the end of the light receiving portion during the calibration without the film 7, as shown in FIG. 3 (B). It will stick out.

On the other hand, when the film 7 is present, the laser light is diffused when passing through the film 7 as shown in FIG. 4 (A), so the density signal of the received light is represented by the solid line in FIG. 4 (B). It shows a somewhat smooth transition as shown.

Therefore, when the difference between the two density signals is obtained, the signal becomes a signal protruding downward at the end as shown in FIG. 4C, and when this is imaged, white vertical stripes occur. In order to eliminate this, when the laser light irradiates the end portion of the film 7, the main scanning direction length L1 of the light receiving portion 23 is increased so that the transmitted light does not enter the corner 25 of the light receiving portion 23. Good.

This will be described with reference to FIG. The figure shows polygon 4,
The positional relationship between the film 7 and the light receiving portion 23 is shown.

If the distance from the laser light emitting position of the polygon 4 to the film 7 is L4, the distance from the film 7 to the laser light incident position 24 of the light receiving unit 23 is L5, and the film width is L3, the main scanning of the light receiving unit 23 is performed. The direction length L1 may satisfy the following expression (4).

L1 ≧ L3 · (1 + L5 / L4) (4) That is, if the length L1 in the main scanning direction is sufficient to satisfy the expression (4), the laser light transmitted through the film 7 enters the corner 25 of the light receiving portion 23. And the disturbance of the density signal at the end of the light receiving section 23 is eliminated.

Next, the distance L2 from the laser light incident position 24 to the incident surface of the photomultiplier 10 (hereinafter, referred to as "length in the sub-scanning direction") will be described with reference to FIG.

The photomultiplier 10 collects and receives the laser light incident on each point at the incident position 24, and the intensity of the received light varies depending on each point on the incident position 24. That is, the light reflected at the central portion 26 and the light reflected at the corners 25 are
The amount of light received at differs by (COSθ) times. (However,
θ is an angle formed by a line connecting the central portion 26 and the light receiving portion of the Photomul 10 and a line connecting the corner 25 and the light receiving portion of the Photomul 10. Therefore, in the normal photomultiplier 10, it is necessary to correct the amount of received light based on the angle at which the laser light is received, which is called shading correction. However,
This shading correction is generally possible only when (COSθ) is larger than 0.8 due to the characteristics of the photomultiplier 10. Therefore, the sub-scanning direction length L2 must be increased to the extent that this condition is satisfied. That is, the following expression (5) must be satisfied.

^{COSθ = L2 / {2 2 +} L1 2/4} 1/2 ≧ 0.8 ... (5) Thus, L2 ≧ 2 · L1 / 3 ... (6) that is, by increasing the distance L2 to the extent that satisfied (6) If so, shading correction can be performed with Photomal 10.

In this way, in this embodiment, the scanned laser light is condensed using the box-shaped light receiving unit 23 and introduced into the photomultiplier 10, and dust 19 is attached to the laser light incident position in the light receiving unit. Since it is extremely rare to do so, it is rarely affected by dust 19. In addition, even if dust 19 adheres to the laser light incident position, since the beam diameter of the laser light is expanded at this incident position, the dust 19 does not significantly change the concentration signal. Therefore, the problem that white vertical stripes appear on the screen is eliminated. Further, even if the side surface of the polygon 4 is tilted, this is not affected, so that horizontal stripes do not occur on the screen.

Further, if the length L1 of the light receiving portion 23 in the main scanning direction is made long enough to satisfy the above formula (4) and the length L2 of the sub scanning direction is made long enough to satisfy the formula (6), the light receiving portion The laser light incident on 23 is not irregularly reflected at the corners.
It becomes possible to perform shading correction on the light received by the photomultiplier 10.

[Effects of the Invention] As described above, in the present invention, even if dust or the like adheres to the light receiving means, this effect is hardly affected, and thus the problem that white vertical stripes are generated on an image as in the conventional case is solved. To be done. Further, even if the side surface of the polygon is tilted, it is not affected and side stripes can be suppressed.

Further, the laser light incident on the light receiving means is not irregularly reflected at the end portion, and the received light can be surely shading-corrected by the photoelectric conversion means such as Photomal, so that it is recorded on the film. It is possible to obtain the effect that the image data can be read as a good image with high definition.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a view of the apparatus of this embodiment viewed from the main scanning direction side, and FIG. 3 is a laser beam incident position and a density signal when there is no film. FIG. 4 is an explanatory view showing the change of the incident position of the laser beam and the density signal when there is a film, and FIG. 5 is a polygon. FIG. 6 is an explanatory view showing the positional relationship between the film and the light receiving portion, and FIG. 6 is an explanatory view showing the relationship between the length L1 in the main scanning direction and the length L2 in the sub scanning direction of the light receiving portion. Further, FIG. 7 is a configuration diagram showing a conventional example, FIG. 8 is a block diagram showing a configuration of an electronic circuit connected to a post-process of Photomaru, and FIG. 9 is dust adhered to the diffuser when there is no film. Fig. 10 shows the density signal when there is a film, Fig. 10 shows the density signal when dust adheres to the diffuser when there is a film, and Fig. 11 shows the density difference between when there is a film and when there is no film. And FIG. 12 are explanatory views showing changes in the incident position of the laser light due to the surface tilt of the polygon. 4 ... Polygon, 7 ... Film 8 ... Diffuser, 10 ... Photomul 19 ... Dust, 22 ... Slit 23 ... Light receiving part, 24 ... Incident position

Claims (4)

[Claims] 1. An image on a film is scanned by irradiating a laser beam, transmitted light of the film is condensed by a light receiving means, and then converted into an electric signal by a photoelectric conversion means, and the image on the film is converted into an electric signal. In the film image reading apparatus for reading as a signal, the light receiving means includes an entrance chamber in a light-shielded state, an opening formed in the entrance chamber for allowing the film-transmitted light to enter the inside, and the opening formed in the entrance chamber. A film image reading device, comprising: a focusing unit that reflects and focuses light incident from the photoelectric conversion unit toward the photoelectric conversion unit. 2. The length of the incident chamber in the main scanning direction is made sufficiently long so that the light transmitted through the film does not diffusely be reflected at the end portion, and the length in the sub scanning direction is made long enough to correct shading of the light focused in the incident chamber. The film image reading apparatus according to claim 1. 3. The main operation direction length L1 is a film width L3,
From the distance L4 from the laser emitting position to the film and the distance L5 from the film to the light incident position of the light receiving means, L1 ≧
The relationship {L3 · (1 + L5 / L4)} is satisfied, and the sub-operation direction length L2 has a relationship L2 ≧ (2 · L1 / 3).
The film image reading device described. 4. The inner surface of the entrance chamber is directed to ignore incident light,
And a coating material capable of reflecting with high reflectance is applied.
4. The film image reading device according to any one of 3 to 3.