Image projection apparatus

• US 7,866,823 B2
• Filed: 04/23/2007
• Issued: 01/11/2011
• Est. Priority Date: 04/27/2006
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Asai, Hiromi
• Primary Examiner(s): Lee; John R
• Application Number:
  US11/738,801
• Publication Number:
  US 20070252955A1
• Time in Patent Office: 1,359 Days
• Field of Search: 353/52, 353/53, 353/101, 359/820
• US Class Current: 353/52
• CPC Class Codes: G02B 7/008 with means for compensating for changes in temperature or for controlling the temperature; thermal stabilisation
• CPC Class Codes: G03B 21/142 Adjusting of projection optics
• CPC Class Codes: G03B 21/53 Means for automatic focusing, e.g. to compensate thermal effects

Abstract

An image projection apparatus is disclosed which is capable of correcting defocusing due to changes of the temperature of a projection lens, which are caused by various factors. The image projection apparatus includes an image-forming element which is illuminated with light from a light source, a projection lens which includes a focus lens and projects light from the image-forming element onto a projection surface, plural temperature detectors which are provided at positions different from each other in the image projection apparatus. The apparatus further includes a controller which controls the position of the focus lens on the basis of the detection results by the plural temperature detectors.

Claims

1. An image projection apparatus comprising:

an image-forming element configured to be illuminated with light from a light source;

a projection lens configured to include a focus lens and configured to project light from the image-forming element onto a projection surface;

plural temperature detectors configured to be provided at positions different from each other in the image projection apparatus and configured to detect temperatures at the respective positions as detection results;

a controller configured to control the position of the focus lens on the basis of the detection results by the plural temperature detectors; and

an optical member configured to introduce the light from the image-forming element to the projection lens,

wherein a first temperature detector of the plural temperature detectors is configured to detect the temperature of the optical member or in a region adjacent thereto, and

wherein the region adjacent to the optical member is closer to the optical member than the projection lens.

2. The apparatus according to claim 1, wherein the controller is configured to determine a temperature zone on the basis of the detection result by a second temperature detector of the plural temperature detectors and is configured to obtain information for controlling the position of the focus lens on the basis of the temperature zone and the detection result by at least one other temperature detector including the first temperature detector.

3. The apparatus according to claim 2, wherein the second temperature detector is configured to detect an environmental temperature around the apparatus.

4. The apparatus according to claim 3, further comprising an AF detector configured to detect AF information used in autofocus control of the projection lens,

wherein the second temperature detector being installed near the AF detector is used also as a temperature detector for correcting the AF information detected by the AF detector in association with temperature.

5. The apparatus according to claim 1,

wherein the apparatus includes plural image-forming elements, and

wherein the optical member is configured to combine light components from the plural image-forming elements and is configured to introduce the combined light to the projection lens.

6. The apparatus according to claim 1, wherein the plural temperature detectors include a temperature detector configured to detect the temperature of the projection lens or in a region adjacent thereto.

7. The apparatus according to claim 1,

wherein the projection lens is a zoom lens capable of varying its focal length, and

wherein the controller is configured to obtain information associated with the focal length of the projection lens as information for controlling the position of the focus lens.

8. An image display system comprising:

the image projection apparatus according to claim 1; and

an image supply apparatus configured to supply image information to the image projection apparatus.