METHOD OF MEASURING ZOOM RATIO OF PROJECTION OPTICAL SYSTEM, METHOD OF CORRECTING PROJECTION IMAGE USING THE METHOD, AND PROJECTOR EXECUTING THE CORRECTION METHOD

• US 20100123878A1
• Filed: 10/26/2009
• Published: 05/20/2010
• Est. Priority Date: 11/17/2008
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: FURUI, Shiki
• Granted Patent: US 8,186,835 B2
• Time in Patent Office: Days
• US Class Current: 353/70
• CPC Class Codes: G01M 11/0264 by using targets or reference patterns
• CPC Class Codes: G03B 21/142 Adjusting of projection optics
• CPC Class Codes: G03B 21/147 Optical correction of image distortions, e.g. keystone
• CPC Class Codes: H04N 9/3185 Geometric adjustment, e.g. keystone or convergence optical or mechanical adjustment of convergence H04N9/317; using scanning means H04N3/22; optical or mechanical adjustments of projectors not peculiar to the presence of an electronic spatial light modulator G03B21/14
• CPC Class Codes: H04N 9/3194 including sensor feedback

Abstract

A method of measuring a zoom ratio of a projection optical system adapted to project image light representing an original image on a projection screen, the method includes: (a) projecting and displaying a measuring image including a measurement point on the projection screen so that the measurement point is displayed at a position with an offset from an optical axis of the projection optical system; (b) detecting a projected measurement point, which is the measurement point projected and displayed on the projection screen, from a measurement point detection position having a fixed position relative to the projection optical system; and (c) determining the zoom ratio using position information of the detected projected measurement point and correspondence between the position information and the zoom ratio, the correspondence being prepared previously.

Claims

1. A method of measuring a zoom ratio of a projection optical system adapted to project image light representing an original image on a projection screen, the method comprising:

(a) projecting and displaying a measuring image including a measurement point on the projection screen so that the measurement point is displayed at a position with an offset from an optical axis of the projection optical system;

(b) detecting a projected measurement point, which is the measurement point projected and displayed on the projection screen, from a measurement point detection position having a fixed position relative to the projection optical system; and

(c) determining the zoom ratio using position information of the detected projected measurement point and correspondence between the position information and the zoom ratio, the correspondence being prepared previously.

2. The method according to claim 1, wherein

step (b) includes

(b1) detecting an image of the projected measurement point on a captured image obtained by capturing the projected measurement point from the measurement point detection position by an image capturing section, and

a direction vector of an optical axis of the image capturing section and a direction vector having a direction in which the measurement point has an. offset from an optical axis of the projection optical system in the original image of the measuring image are substantially perpendicular to each other.

3. The method according to claim 2, wherein

the position information includes coordinates of the image of the projected measurement point on the captured image, and

step (c) includes

(c1) determining the zoom ratio corresponding to the coordinates of the image using the coordinates of the image and the correspondence between the coordinates of the image and the zoom ratio, the correspondence being prepared previously.

4. A method of correcting an image for correcting a projection image displayed by projecting image light representing an original image on a projection screen via a projection optical system provided with a zoom mechanism, the method comprising:

(a) projecting and displaying a measuring image including a measurement point on the projection screen so that the measurement point is displayed at a position with an offset from an optical axis of the projection optical system;

(b) detecting a projected measurement point, which is the measurement point projected and displayed on the projection screen, from a measurement point detection position having a fixed position relative to the projection optical system;

(c) determining the zoom ratio using position information of the detected projected measurement point and correspondence between the position information and the zoom ratio, the correspondence being prepared previously; and

(d) correcting keystone distortion of the projection image using the determined zoom ratio.

5. The method according to claim 4, wherein

step (b) includes

(b1) detecting an image of the projected measurement point on a captured image obtained by capturing the projected measurement point from the measurement point detection position by an image capturing section, and

a direction vector of an optical axis of the image capturing section and a direction vector having a direction in which the measurement point has an offset from an optical axis of the projection optical system in the original image of the measuring image are substantially perpendicular to each other.

6. The method according to claim 5, wherein

the position information includes coordinates of the image of the projected measurement point on the captured image, and

step (c) includes

(c1) determining the zoom ratio corresponding to the coordinates of the image using the coordinates of the image and the correspondence between the coordinates of the image and the zoom ratio, the correspondence being prepared previously.

7. A projector adapted to display a projection image by projecting image light representing an original image on a projection screen, comprising:

a projection optical system provided with a zoom mechanism, and adapted to project the image light on the projection screen;

a measurement point detection section adapted to detect a projected measurement point included in a measuring image projected from the projection optical system to the projection screen; and

a control section adapted to execute a correction of the projection image,

wherein the projected measurement point includes a zoom ratio measuring projected measurement point projected and displayed at a position with an offset from an optical axis of the projection optical system,

the measurement point detection section is disposed at a measurement point detection position having a fixed relative position to the projection optical system, and

the control section obtains position information of the detected zoom ratio measuring projected measurement point, determines the zoom ratio using correspondence between the position information and a zoom ratio corresponding to the position information, the correspondence being prepared previously, and executes correction of the projection image using the zoom ratio determined.

8. The projector according to claim 7, wherein

the measurement point detection section includes an image capturing section adapted to capture the projected measurement point, and

a direction vector of an optical axis of the image capturing section and a direction vector having a direction in which the zoom ratio measuring projected measurement point has an offset from an optical axis of the projection optical system in the original image of the measuring image are substantially perpendicular to each other.

9. The projector according to claim 8, wherein

the position information includes coordinates of an image of the zoom ratio measuring projected measurement point on a captured image captured by the image capturing section, and

the control section determines the zoom ratio corresponding to the coordinates of the image using the coordinates of the image and the correspondence between the image and the zoom ratio, the correspondence being prepared previously.