Two-dimensional image acquisition device and two-dimensional image acquisition method

Abstract

To provide a device and a method, capable of acquiring a two-dimentional image by using a two-dimentional projection data acquisition sensor.SOLUTION: A two-dimensional image acquisition device 1 comprises a two-dimensional projection data acquisition sensor 11; a stage 12; an optical system 13; and an image reconstruction part 14. The two-dimensional projection data acquisition sensor 11 outputs a one-dimensional light intensity profile (X-direction projection data) x1 to xN obtained by integrating two-dimensional light intensity profiles at a light reception part in an X direction, and outputs a two-dimensional light intensity profile (Y-direction projection data) y1 to yM obtained by integrating the one-dimensional light intensity profiles at the light reception part in the Y direction. The image reconstruction part 14 calculates the two-dimensional light intensity profile at the light reception part of the two-dimensional projection data acquisition sensor 11 by performing the image reconstruction on the basis of the X-direction projection data x1 to xN acquired in a plurality of directions and Y-direction projection data y1 to yM.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an apparatus and a method for acquiring a two-dimensional image.

Background Art

[0002] The sensors for acquiring two-dimensional projection data described in Non-Patent Documents 1 and 2 are area sensors specialized for acquiring projection data, and are also called profile sensors. The sensors for acquiring two-dimensional projection data can acquire one-dimensional light intensity profiles obtained by integrating two-dimensional light intensity profiles in the light receiving unit in the X direction and the Y direction, respectively.

[0003] FIG. 1 is a diagram showing the configuration of the light receiving unit of the sensor for acquiring two-dimensional projection data. In the light receiving unit of the sensor for acquiring two-dimensional projection data, a plurality of pixels each including two photodiodes are two-dimensionally arranged in M rows and N columns. Let the two photodiodes included in the pixel in the m-th row and the n-th column be PD1 m,n , PD2 m,n . Here, M and N are integers of 2 or more, m is an arbitrary integer of 1 or more and M or less, and n is an arbitrary integer of 1 or more and N or less.

[0004] The output terminals of the M photodiodes PD1 1,n ~PD1 M,n in the n-th column are connected by a common wiring, and the entirety of these M photodiodes is regarded as a substantial one pixel (H), and a signal value x n corresponding to the total amount of light received by these photodiodes is output through the common wiring. Thereby, the sensor for acquiring two-dimensional projection data can output one-dimensional light intensity profiles (X-direction projection data) x1 to x N obtained by integrating the two-dimensional light intensity profile in the light receiving unit in the X direction.

[0005] The N photodiodes PD2 m,1 ~PD2 m,NEach output terminal is connected by a common wiring, and the entire set of these N photodiodes is regarded as a substantial single pixel (V), and a signal value y corresponding to the sum of the light reception amounts of these photodiodes m is output through the common wiring. As a result, the two-dimensional projection data acquisition sensor integrates the two-dimensional light intensity profile in the light receiving section in the Y direction to obtain a one-dimensional light intensity profile (Y-direction projection data) y1~y M .

[0006] The X-direction projection data x1~x N output from the two-dimensional projection data acquisition sensor and the Y-direction projection data y1~y M have a smaller data volume (N + N) compared to the data volume (MN) output from a normal area sensor that acquires a two-dimensional light intensity profile (two-dimensional image) in the light receiving section. Therefore, the two-dimensional projection data acquisition sensor can detect the position of the spot light incident on the light receiving section and moving objects at high speed compared to a normal area sensor.

Prior Art Documents

Non-Patent Documents

[0007]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] Although a sensor for acquiring two-dimensional projection data can rapidly detect the position of a spot light and a moving object in a light-receiving unit, it cannot acquire a two-dimensional light intensity profile (two-dimensional image) in the light-receiving unit.

[0009] For example, a sensor for acquiring two-dimensional projection data is used to monitor some phenomenon or situation based on the detection results of the position of a spot light and a moving object in a light-receiving unit. When an abnormality is detected during this monitoring, it may be necessary to measure the two-dimensional light intensity profile in the light-receiving unit in order to investigate the abnormal state in detail. In such a case, it is conceivable to arrange a normal area sensor instead of the sensor for acquiring two-dimensional projection data, switch the traveling direction of light by a movable mirror to selectively make light incident on either the sensor for acquiring two-dimensional projection data or the normal area sensor, or split the light into two branches by a beam splitter to simultaneously make light incident on both the sensor for acquiring two-dimensional projection data and the normal area sensor. However, optical system adjustment is not easy for any of these methods.

[0010] The present invention has been made to solve the above problems, and an object thereof is to provide an apparatus and a method capable of acquiring a two-dimensional image using a sensor for acquiring two-dimensional projection data.

Means for Solving the Problems

[0011] The two-dimensional image acquisition apparatus of the present invention includes: (1) a sensor for acquiring two-dimensional projection data that acquires a one-dimensional light intensity profile obtained by integrating the two-dimensional light intensity profile in the light-receiving unit in the x direction and the y direction respectively; (2) an orientation changing unit that changes the relative orientation of the two-dimensional light intensity profile in the light-receiving unit; and (3) an image reconstruction unit that performs image reconstruction based on the data of the one-dimensional light intensity profile acquired by the sensor for acquiring two-dimensional projection data when the two-dimensional light intensity profile in the light-receiving unit is set in a plurality of orientations by the orientation changing unit, and obtains the two-dimensional light intensity profile in the light-receiving unit.

[0012] The orientation changing unit may include a stage for rotating the two-dimensional projection data acquisition sensor around a straight line perpendicular to the light receiving unit of the two-dimensional projection data acquisition sensor. Alternatively, the orientation changing unit may include an optical system for rotating the orientation of the two-dimensional light intensity profile in the light receiving unit of the two-dimensional projection data acquisition sensor.

[0013] The two-dimensional image acquisition method of the present invention includes: (1) a two-dimensional projection data acquisition step of acquiring a one-dimensional light intensity profile obtained by integrating the two-dimensional light intensity profile in the light receiving unit in the x direction and the y direction respectively using a two-dimensional projection data acquisition sensor; (2) an orientation changing step of changing the relative orientation of the two-dimensional light intensity profile in the light receiving unit; and (3) an image reconstruction step of performing image reconstruction based on the data of the one-dimensional light intensity profile acquired by the two-dimensional projection data acquisition sensor when the two-dimensional light intensity profile in the light receiving unit is set in each of a plurality of orientations by the orientation changing step, and obtaining the two-dimensional light intensity profile in the light receiving unit.

[0014] In the orientation changing step, the relative orientation of the two-dimensional light intensity profile in the light receiving unit may be changed using a stage for rotating the two-dimensional projection data acquisition sensor around a straight line perpendicular to the light receiving unit of the two-dimensional projection data acquisition sensor. Alternatively, in the orientation changing step, the relative orientation of the two-dimensional light intensity profile in the light receiving unit may be changed using an optical system for rotating the orientation of the two-dimensional light intensity profile in the light receiving unit of the two-dimensional projection data acquisition sensor.

Effects of the Invention

[0015] According to the present invention, a two-dimensional image can be acquired using a two-dimensional projection data acquisition sensor.

Brief Description of the Drawings

[0016]

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[0017] Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant descriptions are omitted. The present invention is not limited to these examples, but is shown by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0018] FIG. 2 is a diagram showing the configuration of the two-dimensional image acquisition device 1 including the two-dimensional projection data acquisition sensor 11. The two-dimensional image acquisition device 1 includes the two-dimensional projection data acquisition sensor 11, a stage 12, an optical system 13, and an image reconstruction unit 14. For convenience of explanation, an xyz orthogonal coordinate system is shown in this figure. The x-axis and the y-axis are parallel to the light receiving portion of the two-dimensional projection data acquisition sensor 11.

[0019] As described with reference to FIG. 1, the two-dimensional projection data acquisition sensor 11 acquires a one-dimensional light intensity profile obtained by integrating the two-dimensional light intensity profile in the light receiving portion in the X direction and the Y direction respectively. The two-dimensional projection data acquisition sensor 11 has one-dimensional light intensity profiles (X-direction projection data) x1 to x obtained by integrating the two-dimensional light intensity profile in the light receiving portion in the X direction. Ncan be output, and the one-dimensional light intensity profile (Y-direction projection data) y1~y obtained by integrating the two-dimensional light intensity profile in the light receiving unit in the Y direction M can be output.

[0020] The stage 12 supports the two-dimensional projection data acquisition sensor 11. The stage 12 may be capable of rotating the two-dimensional projection data acquisition sensor 11 around a straight line perpendicular to the light receiving unit of the two-dimensional projection data acquisition sensor 11 (a straight line parallel to the z-axis).

[0021] The optical system 13 is an optical system through which light passes before it enters the light receiving unit of the two-dimensional projection data acquisition sensor 11. The optical system 13 may be optional, but may also be capable of rotating the orientation of the two-dimensional light intensity profile in the light receiving unit of the two-dimensional projection data acquisition sensor 11.

[0022] Both or either one of the stage 12 and the optical system 13 is used as an orientation changing unit that changes the relative orientation of the two-dimensional light intensity profile in the light receiving unit of the two-dimensional projection data acquisition sensor 11.

[0023] When the two-dimensional light intensity profile is set in each of a plurality of orientations in the light receiving unit of the two-dimensional projection data acquisition sensor 11 by the stage 12 or the optical system 13 which is an orientation changing unit, the image reconstruction unit 14 inputs the data of the one-dimensional light intensity profile (X-direction projection data x1~x N , Y-direction projection data y1~y M ) acquired by the two-dimensional projection data acquisition sensor 11. The image reconstruction unit 14 performs image reconstruction based on the X-direction projection data x1~x N and the Y-direction projection data y1~y M acquired for each of the plurality of orientations, and obtains the two-dimensional light intensity profile in the light receiving unit of the two-dimensional projection data acquisition sensor 11.

[0024] The image reconstruction unit 14 may be a computer including a processing unit (such as a CPU, etc.) that performs arithmetic processing, a storage unit (such as a hard disk drive, ROM, RAM, etc.) that stores programs and various data necessary for arithmetic processing, a display unit (such as a liquid crystal display, etc.) that displays arithmetic conditions and arithmetic results, and an input unit (such as a keyboard, mouse, etc.) that accepts various inputs.

[0025] The X-direction projection data x1 to x obtained for each of a plurality of orientations N and the Y-direction projection data y1 to y M are equivalent to a sinogram composed of data acquired by a radiation detector in an X-ray CT (Computed Tomography) apparatus or a PET (Positron Emission Tomography) apparatus. Therefore, the image reconstruction unit 14 uses an algorithm for performing image reconstruction based on a sinogram in an X-ray CT apparatus or a PET apparatus, and for each of a plurality of orientations, the X-direction projection data x1 to x N and the Y-direction projection data y1 to y M to perform image reconstruction, and can obtain a two-dimensional light intensity profile in the light receiving unit of the two-dimensional projection data acquisition sensor 11. As the image reconstruction algorithm, for example, FBP (Filtered Back Projection), MLEM (Maximum Likelihood Expectation Maximization), OSEM (Ordered Subset Expectation Maximization), and DRAMA (Dynamic Row Action Maximum likelihood Algorithm) can be used.

[0026] Alternatively, the image reconstruction algorithm may be combined with compressive sensing (Non-Patent Document 3). When light enters a partial region of the light receiving part of the two-dimensional projection data acquisition sensor 11, it is effective to use an image reconstruction algorithm combined with compressive sensing. The number of measurements can be reduced, and faster image reconstruction processing becomes possible.

[0027] FIG. 3 is a diagram showing a configuration example of the optical system 13. The optical system 13 shown in this figure includes a Dove Prism 13a as an azimuth changing unit. By rotating the Dove Prism 13a around the major axis of the Dove Prism 13a, the pattern of light after passing through the Dove Prism 13a can be rotated. The rotation angle of the light pattern after passing through the Dove Prism 13a is twice the rotation angle of the Dove Prism 13a. Note that a plurality of Dove Prisms may be arranged in series.

[0028] FIG. 4 is a flowchart of the two-dimensional image acquisition method. The two-dimensional image acquisition method includes an initialization step S1, a two-dimensional projection data acquisition step S2, a determination step S3, an azimuth change step S4, and an image reconstruction step S5. Here, it is assumed that a rotatable stage 12 is used as an azimuth changing unit that changes the azimuth θ of the two-dimensional light intensity profile in the light receiving part of the two-dimensional projection data acquisition sensor 11, and the azimuth θ is sequentially increased from the initial value θ0 to the end value θ1 by a constant update amount Δθ.

[0029] In the initialization step S1, the azimuth θ is set to the initial value θ0 by the stage 12. In the two-dimensional projection data acquisition step S2, the X-direction projection data x1 to x N and the Y-direction projection data y1 to y M are acquired by the two-dimensional projection data acquisition sensor 11 at the set azimuth θ.

[0030] In the determination step S3, it is determined whether or not the azimuth θ has reached the end value θ1. If it is determined in the determination step S3 that the azimuth θ has not reached the end value θ1, in the azimuth change step S4, Δθ is added to θ to obtain a new θ, and the stage 12 is used to change to the new azimuth θ, and then the process returns to the two-dimensional projection data acquisition step S2. Steps S2 to S4 are repeated while the azimuth θ has not reached the end value θ1. If it is determined in the determination step S3 that the azimuth θ has reached the end value θ1, the process proceeds to the image reconstruction step S5.

[0031] In the image reconstruction step S5, the image reconstruction unit 14 performs image reconstruction for each of a plurality of azimuths (each azimuth θ at intervals of the update amount Δθ from the initial value θ0 to the end value θ1), and the X-direction projection data x1 to x N and the Y-direction projection data y1 to y M obtained are used to perform image reconstruction to obtain the two-dimensional light intensity profile at the light receiving unit of the two-dimensional projection data acquisition sensor 11.

[0032] Note that since the projection data in two directions is acquired, θ1 + Δθ - θ0 only needs to be 90°. For example, if the initial value θ0 is 0° and the update amount Δθ is 10°, the end value θ1 only needs to be 80°.

[0033] Next, an embodiment will be described. In this embodiment, it is assumed that the optical system 13 in FIG. 2 includes an aperture and a lens, and the aperture, the lens, and the two-dimensional projection data acquisition sensor 11 are arranged such that the light receiving unit of the two-dimensional projection data acquisition sensor 11 and the aperture have an optically conjugate positional relationship. The laser light output from the laser light source is made to enter the light receiving unit of the two-dimensional projection data acquisition sensor 11 through the aperture and the lens. A rotatable stage 12 is used as the azimuth changing unit for changing the azimuth θ of the two-dimensional light intensity profile at the light receiving unit of the two-dimensional projection data acquisition sensor 11, and the azimuth θ is sequentially increased from the initial value 0° to the end value 80° at a constant update amount of 10°.

[0034] Also, prior to the image reconstruction process by the image reconstruction unit 14, for each azimuth θ (each azimuth θ with an update amount of 10° from the initial value of 0° to the end value of 80°), the X-direction projection data x1 to x N and the Y-direction projection data y1 to y M were subjected to centering with the center of gravity after subtracting the offset. The offset is the value of the projection data output when no light is incident on the light-receiving part of the two-dimensional projection data acquisition sensor 11, and was 25 in this embodiment. The FBP method was used as the image reconstruction algorithm.

[0035] FIGS. 5 and 6 are diagrams showing two-dimensional light intensity profiles obtained by the image reconstruction process in the embodiment. FIG. 5 shows an image of the aperture. FIG. 6 is an image when a wire is arranged on a part of the aperture, and an image in which a part of the aperture is shielded by the wire is obtained.

[0036] As described above, according to this embodiment, a two-dimensional image can be acquired using the two-dimensional projection data acquisition sensor. That is, using the two-dimensional projection data acquisition sensor, the position and moving object of the spot light in the light-receiving part can be detected, and the two-dimensional light intensity profile in the light-receiving part can also be measured without using a normal area sensor.

Explanation of Reference Numerals

[0037] 1... Two-dimensional image acquisition device, 11... Two-dimensional projection data acquisition sensor, 12... Stage, 13... Optical system, 14... Image reconstruction unit.

Claims

1. A two-dimensional projection data acquisition sensor that acquires a one-dimensional light intensity profile obtained by integrating the two-dimensional light intensity profile in the light receiving unit in the x direction and the y direction respectively; An orientation changing unit that changes the relative orientation of the two-dimensional light intensity profile in the light receiving unit; An image reconstruction unit that performs image reconstruction based on the data of the one-dimensional light intensity profile acquired by the two-dimensional projection data acquisition sensor when the two-dimensional light intensity profile is set in each of a plurality of orientations in the light receiving unit by the orientation changing unit, and obtains the two-dimensional light intensity profile in the light receiving unit; A two-dimensional image acquisition device comprising:

2. The orientation changing unit includes a stage that rotates the two-dimensional projection data acquisition sensor around a straight line perpendicular to the light receiving unit of the two-dimensional projection data acquisition sensor, The two-dimensional image acquisition device according to Claim 1.

3. The orientation changing unit includes an optical system that rotates the orientation of the two-dimensional light intensity profile in the light receiving unit of the two-dimensional projection data acquisition sensor, The two-dimensional image acquisition device according to Claim 1.

4. A two-dimensional projection data acquisition step of acquiring a one-dimensional light intensity profile obtained by integrating the two-dimensional light intensity profile in the light receiving unit in the x direction and the y direction respectively using a two-dimensional projection data acquisition sensor; An orientation changing step of changing the relative orientation of the two-dimensional light intensity profile in the light receiving unit; An image reconstruction step of performing image reconstruction based on the data of the one-dimensional light intensity profile acquired by the two-dimensional projection data acquisition sensor when the two-dimensional light intensity profile is set in each of a plurality of orientations in the light receiving unit by the orientation changing step, and obtaining the two-dimensional light intensity profile in the light receiving unit; A two-dimensional image acquisition method comprising:

5. In the orientation changing step, the relative orientation of the two-dimensional light intensity profile in the light receiving unit is changed by using a stage that rotates the two-dimensional projection data acquisition sensor around a straight line perpendicular to the light receiving unit of the two-dimensional projection data acquisition sensor. The two-dimensional image acquisition method according to Claim 4.

6. In the azimuth change step, the relative azimuth of the two-dimensional light intensity profile in the light receiving unit is changed by using an optical system that rotates the azimuth of the two-dimensional light intensity profile in the light receiving unit of the two-dimensional projection data acquisition sensor. The two-dimensional image acquisition method according to claim 4.

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