SHAPE MEASURING DEVICE AND SHAPE MEASURING METHOD

• US 20100008543A1
• Filed: 09/23/2009
• Published: 01/14/2010
• Est. Priority Date: 04/05/2007
• Status: Active Grant

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Yamada, Tomoaki
• Granted Patent: US 8,244,023 B2
• Time in Patent Office: Days
• US Class Current: 382/106
• CPC Class Codes: G01B 11/2518 Projection by scanning of the object
• CPC Class Codes: G06T 7/521 from laser ranging, e.g. using interferometry; from the projection of structured light

Abstract

A shape measuring device includes: a slit pattern projection unit (1) for projecting a slit light onto a test object (20); an imaging lens (3) and a plane parallel plate (4) for forming a plurality of slit images, which is generated when the slit light is reflected by the object (20), separated in a direction perpendicular to a slit base line direction; an imaging unit (5) for picking up the plurality of slit images and generating a plurality of slit picture images; an XYZ stage drive unit (12) for relatively moving the slit light and the test object (20) in a direction different from the slit base line direction of the slit light; a slit picture image selection unit (8) for comparing the brightness of each pixel of slit picture image on the slit base line direction, and selecting a slit picture image having an optimum brightness to determine the shape of the test object (20) on the slit base line direction, and acquiring image data to determine the shape of the test object (20); and a shape computing unit (9) for computing a shape of the test object (20) using a relative position of the slit light with respect to the test object (20) and the slit picture image data.

Claims

1. A shape measuring device, comprising:

a projection unit that projects a slit projection pattern formed of one slit light onto a test object;

a slit image formation unit that forms a plurality of slit images, which is generated by the slit projection pattern projected from the projection unit is reflected by the test object, separated in a direction perpendicular to a slit base line direction;

an imaging unit that picks up the plurality of slit images separately formed by the slit image formation unit to generate a plurality of slit picture images;

a position adjustment unit that relatively moves the slit projection pattern and the test object in a direction different from the slit base direction of the slit projection pattern;

a slit picture image selection unit that compares brightness of each pixel of slit picture image on the slit base line direction and selects, from the plurality of slit picture images acquired by the imaging unit, a slit picture image having an optimum brightness to determine the shape of the test object on the slit base line direction, and acquires slit image data for determining the shape of the test object; and

a shape computing unit that computes a shape of the test object using a relative position of the slit projection pattern with respect to the test object, which has been relatively moved by the position adjustment unit, and the slit picture image data acquired by the slit picture image selection unit.

2. The shape measuring device according to claim 1, wherein in the imaging unit, the plurality of slit picture images are formed in the direction perpendicular to the slit base line direction separately as a first slit picture image and at least a second slit picture image, in which brightness distribution of the first slit image is changed.

3. The shape measuring device according to claim 1, wherein in the imaging unit, the plurality of slit picture images are formed in the direction perpendicular to the slit base line direction separately as a first slit picture image and a second slit picture image which is picked up in a position closer to the projection light axis than the first slit picture image.

4. The shape measuring device according to claim 1, wherein in the imaging unit, the plurality of slit picture images are formed in the direction perpendicular to the slit base line direction separately as a first slit picture image and a second slit picture image which is picked up in a position closer to the projection light axis than the first slit picture image and is formed with a smaller numerical aperture than the first slit picture image.

5. The shape measuring device according to any of claims 1 to 4, wherein that in the imaging unit, at least the first slit picture image is formed at a focal position on the image formation plane by inclining the image formation plane with respect to an optical axis of the reflected light generated when the slit projection pattern projected from the projection unit is reflected by the test object, so that the focal plane at the test object side matches the optical axis of the slit projection pattern.

6. The shape measuring device according to any of claims 1 to 4, wherein a shape calibration coefficient for each of the plurality of slit picture images is acquired using a plurality of calibration slit picture images, which the imaging unit acquires by the projection unit projecting the slit projection pattern onto the calibration plate in the same manner as the test object.

7. A method for measuring a three-dimensional shape of a test object using a shape measuring device, which includes a projection unit that projects a slit projection pattern formed of one slit light onto the test object;

a slit image formation unit that forms a plurality of slit picture images, which is generated when the slit projection pattern projected from the projection unit is reflected by the test object, separated in a direction perpendicular to a slit base line direction;

an imaging unit that picks up the plurality of slit images separately formed by the slit image formation unit to generate a plurality of slit picture images; and

a position adjustment unit for relatively moving the slit projection pattern and the test object in a direction different from the slit base direction of the slit projection pattern, the method comprising;

projecting the slit projection pattern onto the test object from the projection unit;

picking up the plurality of slit images separately formed by the slit image formation unit with the imaging unit, and generating a plurality of slit picture images;

comparing the brightness of each pixel of slit picture images on the slit base line direction and selecting a slit picture image having an optimum brightness to determine the height of the test object from the reference plane, from the plurality of slit picture images, and determining the height of the test object from the reference plane; and

measuring the shape of the test object by using a relative position of the slit projection pattern with respect to the test object which has been relatively moved by the position adjustment unit.

8. The shape measuring method according to claim 7, wherein the imaging unit generates the plurality of slit picture images, a first slit picture image and at least a second slit picture image, in which the brightness distribution of the first slit picture image is changed, are separately formed in the direction perpendicular to the slit base line direction.

9. The shape measuring method according to claim 7, wherein the imaging unit generates the plurality of slit picture images, a first slit image and a second slit image, which is picked up in a position closer to a projection light axis than the first slit picture image and is formed with a smaller numerical aperture than the first slit picture image, are separately formed in the direction perpendicular to the slit base line direction.

10. The shape measuring method according any of claims 7 to 9, wherein the imaging unit generates the plurality of slit picture images, at least the first slit picture image is formed at a focal position on the image formation plane by inclining the image formation plane with respect to an optical axis of the reflected light generated when the slit projection pattern projected from the projection unit is reflected by the test object, so that the focal plane at the test object side matches the optical axis of the slit projection pattern.

11. The shape measuring method according any of claims 7 to 9, wherein measuring the shape of the test object further comprises:

projecting the slit projection pattern onto a calibration plate from the projection unit in the same manner as the test object;

picking up a plurality of calibration slit images separately formed by the slit image formation unit with the imaging unit, and generating a plurality of calibration slit picture images;

determining a height of the calibration plate from the reference plane based on the plurality of calibration slit picture images;

acquiring a shape calibration coefficient for each of the plurality of slit picture images acquired by the imaging unit; and

calibrating the height of the test object from the reference plane, determined based on the plurality of slit picture images, and acquiring an accurate shape measurement result of the test object.