# US 10,481,363 B2 · Projector and focus adjustment method

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- Number: US 10,481,363 B2
- Document ID: US10481363B2
- Status: Granted
- Kind: B2
- Application number: 16/070,211
- Filed: 2016-02-03
- Published: 2019-01-17
- Granted: 2019-11-19
- Earliest claimed: 2016-02-03
- Assignees: NEC Display Solutions, Ltd.
- Applicants: NEC Display Solutions, Ltd.
- Inventors: Shigeru Fujino
- Web page: https://patentgrep.com/patent/US10481363B2

## CPC

- G02B 7/28: Systems for automatic generation of focusing signals
- G02B 7/38: measured at different points on the optical axis {, e.g. focussing on two or more planes and comparing image data}
- G03B 13/32: Means for focusing
- G03B 21/00: Projectors or projection-type viewers; Accessories therefor (devices for changing pictures G03B23/00)
- G03B 21/14: Details
- G03B 21/53: Means for automatic focusing, e.g. to compensate thermal effects
- H04N 5/74: Projection arrangements for image reproduction, e.g. using eidophor
- H04N 9/31: Projection devices for colour picture display {, e.g. using electronic spatial light modulators [ESLM]}
- H04N 9/317: {Convergence or focusing systems (electronic adjustment of convergence H04N9/3185; convergence or focusing arrangements for cathode ray tubes H04N9/28; means for automatic focusing of projectors not peculiar to the presence of an electronic spatial light modulator G03B21/53)}
- 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)}
- H04N 23/67: Focus control based on electronic image sensor signals
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G03B: APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR (optical parts of such apparatus G02B; photosensitive materials or processes for photographic purposes G03C; apparatus for processing exposed photographic materials G03D)
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

A projector including: a display unit equipped with an image-forming surface made up of a plurality of pixels; a projection lens that is capable of focus adjustment and that projects an image that is formed on the image-forming surface onto a projection surface; a distortion correction processing unit that, on the basis of distortion correction data for correcting distortion of an image projected onto the projection surface, generates a corrected image by enlarging and/or reducing an image indicated by an input video signal and forms the corrected image on the image-forming surface; and a control unit that adjusts the focus of the projection lens on the basis of the distortion correction data such that a focus range on the projection surface is increased.

## Claims

### Claim 1

A projector comprising:
a display element that is provided with an image-forming surface comprising a plurality of pixels;
a projection lens that is capable of focus adjustment and that projects an image that is formed on said image-forming surface upon a projection surface;
a distortion correction processing unit that, based on distortion correction data for correcting distortion of an image that is projected on said projection surface, enlarges and/or reduces an image that is indicated by a video signal that is received as input to generate a corrected image and causes formation of the corrected image on said image-forming surface; and
a control unit that, based on said distortion correction data, carries out focus adjustment of said projection lens such that a focus range on said projection surface increases, wherein:
said distortion correction data include, for each of said plurality of pixels, a correction coefficient value that corresponds to a projection distance to said projection surface; and
said control unit carries out focus adjustment of said projection lens in which, from among pixel regions in which pixel having a same correction coefficient value are arranged, the pixel region having a greatest number of pixels is taken as an optimal focus point.

### Claim 2 (depends on 1)

The projector as set forth in claim 1, wherein:
said image-forming surface is demarcated into a plurality of areas and a weighting coefficient value is set for each area; and
for each pixel region, said control unit computes a value obtained by multiplying said weighting coefficient value by a number of pixels according to said area and then takes as said optimal focus point the pixel region for which the computed value is greatest.

### Claim 3 (depends on 2)

The projector as set forth in claim 2, wherein:
said plurality of areas include a first area that is positioned in a central portion of said image-forming surface and a second area that surrounds said first area; and
the weighting coefficient value of said first area is greater than the weighting coefficient value of said second area.

### Claim 4 (depends on 3)

The projector as set forth in claim 3, further comprising:
a combining unit that generates a combined image in which an image for focus adjustment is combined with said corrected image and causes the combined image to form on said image-forming surface;
wherein said projection lens includes:
a focus lens; and
an operation unit that accepts operation for focus adjustment, causes said focus lens to move along an optical axis according to the operation, and supplies an operation signal that indicates a direction of movement and an amount of movement; and
said control unit:
takes a region of pixels having a smallest correction coefficient value as a nearest focus point, takes a region of pixels having a largest correction coefficient values as a farthest focus point, and causes the combining unit to generate a first combined image in which a first image that indicates said nearest focus point is combined as said image for focus adjustment with said corrected image and a second combined image in which a second image that indicates said farthest focus point is combined as said image for focus adjustment with said corrected image;
when a user operates said operation unit to carry out focus adjustment for said first image on the projected image of said first combined image, acquires first positional information that indicates a position on said optical axis of said focus lens when focus is realized at said nearest focus point based on said operation signal;
when the user operates said operation unit to carry out focus adjustment for said second image on the projected image of said second combined image, acquires second positional information that indicates a position on said optical axis of said focus lens when focus is realized at said farthest focus point based on said operation signal; and
based on the relation of said correction coefficient values of said nearest focus point, said farthest focus point and said optimal focus point and said first and second positional information, acquires a position on said optical axis of said focus lens when focus is realized at said optimal focus point and causes said focus lens to move to the position.

### Claim 5 (depends on 2)

The projector as set forth in claim 2, further comprising:
a combining unit that generates a combined image in which an image for focus adjustment is combined with said corrected image and causes the combined image to form on said image-forming surface;
wherein said projection lens includes:
a focus lens; and
an operation unit that accepts operation for focus adjustment, causes said focus lens to move along an optical axis according to the operation, and supplies an operation signal that indicates a direction of movement and an amount of movement; and
said control unit:
takes a region of pixels having a smallest correction coefficient value as a nearest focus point, takes a region of pixels having a largest correction coefficient values as a farthest focus point, and causes the combining unit to generate a first combined image in which a first image that indicates said nearest focus point is combined as said image for focus adjustment with said corrected image and a second combined image in which a second image that indicates said farthest focus point is combined as said image for focus adjustment with said corrected image;
when a user operates said operation unit to carry out focus adjustment for said first image on the projected image of said first combined image, acquires first positional information that indicates a position on said optical axis of said focus lens when focus is realized at said nearest focus point based on said operation signal;
when the user operates said operation unit to carry out focus adjustment for said second image on the projected image of said second combined image, acquires second positional information that indicates a position on said optical axis of said focus lens when focus is realized at said farthest focus point based on said operation signal; and
based on a relation of said correction coefficient values of said nearest focus point, said farthest focus point and said optimal focus point and said first and second positional information, acquires a position on said optical axis of said focus lens when focus is realized at said optimal focus point and causes said focus lens to move to the position.

### Claim 6 (depends on 1)

The projector as set forth in claim 1, further comprising:
a combining unit that generates a combined image in which an image for focus adjustment is combined with said corrected image and causes the combined image to form on said image-forming surface;
wherein said projection lens includes:
a focus lens; and
an operation unit that accepts operation for focus adjustment, causes said focus lens to move along an optical axis according to the operation, and supplies an operation signal that indicates a direction of movement and an amount of movement; and
said control unit:
takes a region of pixels having a smallest correction coefficient value as a nearest focus point, takes a region of pixels having a largest correction coefficient values as a farthest focus point, and causes the combining unit to generate a first combined image in which a first image that indicates said nearest focus point is combined as said image for focus adjustment with said corrected image and a second combined image in which a second image that indicates said farthest focus point is combined as said image for focus adjustment with said corrected image;
when a user operates said operation unit to carry out focus adjustment for said first image on the projected image of said first combined image, acquires first positional information that indicates a position on said optical axis of said focus lens when focus is realized at said nearest focus point based on said operation signal;
when the user operates said operation unit to carry out focus adjustment for said second image on the projected image of said second combined image, acquires second positional information that indicates a position on said optical axis of said focus lens when focus is realized at said farthest focus point based on said operation signal; and
based on a relation of said correction coefficient values of said nearest focus point, said farthest focus point and said optimal focus point and said first and second positional information, acquires a position on said optical axis of said focus lens when focus is realized at said optimal focus point and causes said focus lens to move to the position.

### Claim 7

A focus adjustment method of a projector that includes a display element that is equipped with an image-forming surface comprising a plurality of pixels and a projection lens that is capable of focus adjustment and that projects an image that is formed on said image-forming surface upon a projection surface; said focus adjustment method comprising:
based on distortion correction data for correcting distortion of an image that is projected upon said projection surface, enlarging and/or reducing an image that is indicated by a video signal that is received as input to generate a corrected image and forming the corrected image on said image-forming surface; and
based on said distortion correction data, carrying out focus adjustment of said projection lens such that a focus range on said projection surface is increased, wherein;
said distortion correction data include, for each of said plurality of pixels, a correction coefficient value that corresponds to a projection distance to said projection surface; and
the focus adjustment of said projection lens is carried out in which, from among pixel regions in which pixels having a same correction coefficient value are arranged, the pixel region having a greatest number of pixels is taken as an optimal focus point.