ANGLE MEASURING DEVICE AND METHOD

• US 20090231573A1
• Filed: 09/20/2006
• Published: 09/17/2009
• Est. Priority Date: 09/21/2005
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Utsuro, Hidetoshi, Takata, Kazumasa, Furuta, Tomotaka, Urashima, Takashi
• Granted Patent: US 7,821,626 B2
• Time in Patent Office: Days
• US Class Current: 356/139.100
• CPC Class Codes: G01B 11/26 for measuring angles or tapers; for testing the alignment of axes

Abstract

By diffracting light emitted from a collimator lens into lights of different orders by a transmission diffraction grating, applying the diffracted lights to a flat surface of an object, forming the light that has been reflected on the flat surface of the object and thereafter retransmitted through the transmission diffraction grating into an image in a position located apart from the optical axis of the outgoing light and measuring the angle of the object with respect to the optical axis of the collimator lens using the image location and the order of the light formed as the image, the angle in a wide range can be measured with a high resolving power.

Claims

1. An angle measuring device comprising:

a light source;

a photodetector;

a collimator lens to collimate light emitted from the light source along its optical axis;

a transmission diffraction grating which is placed in the optical axis, to make the parallel light passed through and make several lights of different orders;

an optical system to form diffracted light reflected on a flat surface of an object at the position facing the transmission diffraction grating into an image on the photodetector after making the light passed through the transmission diffraction grating; and

a calculating device to calculate an angle of the object with respect to the optical axis using an image location on the photodetector and the order of the light formed as the image.

2. The angle measuring device as defined in claim 1, further comprising:

a rotator to rotate the object so that an angle of the flat surface with respect to the optical axis is changed; and

a controller which has order specifying information to relate a rotation position of the object by the rotator with each order of the diffracted light formed as an image on the photodetector, for specifying the order of the light formed as the image by rotation position information of the object and the order specifying information.

3. The angle measuring device as defined in claim 2, wherein the rotator is a device to rotate the object along a circular arc centered on the transmission diffraction grating.

4. The angle measuring device as defined in claim 2, wherein the rotator is a device to rotate the object around a center of rotation arranged inside the object.

5. The angle measuring device as defined in claim 1, further comprising:

a light shielding member provided with a light transmitting portion, which is placed between the flat surface of the object and the transmission diffraction grating and which comprises a light passing portion, the light shielding member making a part of the diffracted lights of the orders pass through the light passing portion and shielding the other diffracted lights;

a shifter to shift the light shielding member and the transmission diffraction grating relatively in a direction intersecting the optical axis; and

a controller which has order specifying information to relate a relative displacement position of the light shielding member by the shifter with each order of the diffracted light formed as an image on the photodetector, to specify the specific order of the diffracted light by relative displacement position information of the light shielding member and the order specifying information.

6. The angle measuring device as defined in claim 5, wherein the shifter is a device to shift the light shielding member along a circular arc centered on the transmission diffraction grating.

7. The angle measuring device as defined in claim 5, wherein the light passing portion of the light shielding member is a slit-shaped opening portion, where a slit of a width equal to a width of the parallel light transmitted through the transmission diffraction grating is formed.

9. The angle measuring device as defined in claim 1, further comprising:

an angle calculating section in which, assuming that a focal distance of the collimator lens is f, a wavelength of the parallel light emitted from the lens is λ

, an interval pitch of groove portions of the diffraction grating is d, a specific order of the diffracted light is m, and a distance between the optical axis and the image location position on the photodetector is 1, then an angle φ

of the object with respect to the optical axis of the lens is calculated by the equation;

8. An angle measuring device comprising:

a light source;

a photodetector;

a collimator lens to collimate light emitted from the light source along its optical axis;

a reflection diffraction grating which is placed on the optical axis and a flat surface of an object at the position facing the collimator lens, to reflect applied parallel light by making several lights of different orders;

an optical system to form the reflected diffracted light on the photodetector; and

calculating device to calculate an angle of the object with respect to the optical axis using an image location on the photodetector and the order of the light formed as the image.

10. An angle measuring method comprising:

transmitting parallel light through a diffraction grating and making several lights of different orders by the diffraction grating;

reflecting the diffracted light on a flat surface of an object;

making the reflected diffracted light pass through the diffraction grating and then forming the light into an image; and

calculating an angle of the object with respect to an optical axis of the parallel light using an image location and the order of the light formed as the image.

11. The angle measuring method as defined in claim 10, wherein

a zeroth-order diffracted light is collimated as the image in a state in which the optical axis and the flat surface of the object are arranged perpendicular to each other, thereafter the diffracted lights whose orders are successively increased by one are each formed as the image by displacing the flat surface and the diffraction grating relatively to each other to change the angle of the flat surface with respect to the optical axis, by which order specifying information which relates a relative displacement position of the object with each order of the diffracted light formed as the image is obtained,

the order of the diffracted light formed as an image is specified by the order specifying information and relative displacement position information of the object, and the angle of the object is measured using an image location and the specified order.

12. The angle measuring method as defined in claim 11, wherein the relative displacement of the object with respect to the optical axis is to displace the object along a circular arc centered on the diffraction grating.

13. The angle measuring method as defined in claim 11, wherein the relative displacement of the object with respect to the optical axis is to rotate the object around a center of rotation arranged inside the object.

14. The angle measuring method as defined in claim 10, wherein

a light shielding member provided with a light transmitting portion, which is placed between the flat surface of the object and the diffraction grating and which comprises a light passing portion, the light shielding member making part of the diffracted lights of the orders pass through the light passing portion and shielding the other diffracted lights, is moved in a direction intersecting the optical axis with respect to the diffraction grating while successively forming the diffracted lights of the orders each into an image and order specifying information that relates a relative displacement position of the light shielding member with each order of the diffracted light formed as the image is to obtained, and

the specific order of the diffracted light is specified by the obtained order specifying information and relative displacement position information of the light shielding member, and the angle of the object is calculated on a basis of an image location and the specified order.

15. The angle measuring method as defined in claim 14, wherein the relative displacement of the light shielding member with respect to the diffraction grating is to move the light shielding member along a circular arc centered on the diffraction grating.

17. The angle measuring method as defined in claim 10, wherein

formation of the parallel light and the condensation and image formation of the diffracted light of the specific order are performed by using a collimator lens, and

assuming that a focal distance of the collimator lens is f, a wavelength of the parallel light emitted from the lens is λ

, an interval pitch of groove portions of the diffraction grating is d, a specific order of the diffracted light is m, and a distance between the optical axis and the image location is 1, then an angle φ

of the object with respect to the optical axis is calculated by the equation;

16. An angle measuring method comprising:

reflecting parallel light applied to a diffraction grating placed on a flat surface of an object and diffracting the light into lights of different orders by the diffraction grating;

focusing the reflected diffracted light and forming the light into an image; and

calculating an angle of the object with respect to an optical axis of the parallel light on a basis of an image location of the light and the order of the light.