IMAGING METHOD AND APPARATUS

• US 20100171835A1
• Filed: 08/27/2008
• Published: 07/08/2010
• Est. Priority Date: 08/31/2007
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Ouchi, Toshihiko, Kasai, Shintaro
• Granted Patent: US 8,233,049 B2
• Time in Patent Office: Days
• US Class Current: 348/162
• CPC Class Codes: G01N 2021/3595 using FTIR
• CPC Class Codes: G01N 21/255 Details, e.g. use of specially adapted sources, lighting or optical systems
• CPC Class Codes: G01N 21/29 using visual detection G01N21/31 takes precedence
• CPC Class Codes: G01N 21/3563 for analysing solids; Preparation of samples therefor
• CPC Class Codes: G01N 21/3581 using far infrared light; using Terahertz radiation

Abstract

An object of examination is irradiated with an electromagnetic wave including a frequency component from 30 GHz to 30 THz and a Fourier transform image of the transmitted or reflected electromagnetic wave from the object of examination is obtained. The obtained Fourier transform image is subjected to a spatial frequency filtering processing. This method can visualize only the part to be visualized in an imaging operation using a terahertz wave.

Claims

1. An imaging method using a terahertz wave, comprising:

a generation step of generating a terahertz wave;

a step of acquiring a first Fourier transform image of an object of examination, using the terahertz wave generated in the generation step and transmitted through or reflected by the object of examination;

a step of acquiring a second Fourier transform image to be used as spatial frequency filter for the first Fourier transform image; and

a step of executing an arithmetic operation processing on the first Fourier transform image and the second Fourier transform image.

2. The method according to claim 1, wherein the method further comprises a step of collimating the generated terahertz wave, and the first Fourier transform image is optically acquired.

3. The method according to claim 1, wherein the step of acquiring a first Fourier transform image includes:

a step of optically acquiring a real image of the object of examination, using the terahertz wave generated in the generation step and transmitted through or reflected by the object of examination; and

a step of subjecting the real image to Fourier transform by way of an electric arithmetic operation processing.

4. The method according to claim 1, wherein the step of acquiring a second Fourier transform image includes:

a step of acquiring a real image of the object of examination by means of visible light;

a step of acquiring a binarized image of the real image; and

a step of subjecting the binarized real image to Fourier transform by way of an electric arithmetic operation processing.

5. The method according to claim 1, wherein the step of acquiring a second Fourier transform image includes:

a step of generating a second terahertz wave having a center frequency different from the terahertz wave generated in the generation step to acquire the first Fourier transform image; and

a step of optically acquiring a Fourier transform image of the second terahertz wave transmitted through or reflected by the object of examination.

6. The method according to claim 1, wherein the step of acquiring a second Fourier transform image includes:

a step of reading out a body profile corresponding to the object of examination from average body profiles of different sexes, different ages and different nationalities stored in advance; and

a step of executing Fourier transform on the body profile corresponding to the object of examination.

7. The method according to claim 1, wherein the second Fourier transform image is optically removed or subtracted by way of an electric arithmetic operation processing from the first Fourier transform image in the step of executing an arithmetic operation processing on the first Fourier transform image and the second Fourier transform image.

8. The method according to claim 1, wherein the method further comprises a step of acquiring an inverse Fourier transform image of the image acquired in the step of executing an arithmetic operation processing on the first Fourier transform image and the second Fourier transform image.

9. An imaging apparatus, comprising:

a mechanism for irradiating an object of examination with a collimated coherent electromagnetic wave including a frequency component from 30 GHz to 30 THz;

a mechanism for acquiring a Fourier transform image of the transmitted electromagnetic wave or the reflected electromagnetic wave from the object of examination by means of an optical unit; and

a mechanism for executing a spatial frequency filtering processing on the Fourier transform image.

10. The apparatus according to claim 9, wherein the apparatus further comprises a mechanism for executing inverse Fourier transform on the Fourier transform image subjected to the spatial frequency filtering processing.

11. The apparatus according to claim 9, wherein an optical system formed by using a plurality of lenses or minors is employed for the mechanism for acquiring a Fourier transform image, and

wherein the distance from an optical plane closest to the object of examination out of optical planes of the optical system to the object of examination is greater than the distance from an optical plane closest to a detector out of the optical planes of the optical system to the detector.

12. The apparatus according to claim 9, wherein the mechanism for acquiring a Fourier transform image has a lens or a minor for forming a focused real image of the object of examination and a lens or a minor for forming a Fourier transform image of the real image.

13. The apparatus according to claim 9, wherein an optical system is employed for the mechanism for acquiring a Fourier transform image, and the optical system has a variable focus mechanism and a mechanism for changing the relative distance between the object of examination and the mechanism for acquiring a Fourier transform image or both of them.

14. The apparatus according to claim 11, wherein the detector also operates for spatial frequency filtering on the Fourier transform image.