# US 7,612,951 B2 · Projection lens unit

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- Number: US 7,612,951 B2
- Document ID: US7612951B2
- Status: Granted
- Kind: B2
- Application number: 11/728,120
- Filed: 2007-03-23
- Published: 2007-10-11
- Granted: 2009-11-03
- Earliest claimed: 2006-03-24
- Assignees: Konica Minolta Opto, Inc.
- Inventors: Atsuo Masui; Tokuji Matsuda; Kohei Wataru
- Web page: https://patentgrep.com/patent/US7612951B2

## CPC

- G02B 7/028: {with means for compensating for changes in temperature or for controlling the temperature; thermal stabilisation}
- G02B 7/023: {permitting adjustment}
- G02B 13/22: Telecentric objectives or lens systems
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A projection lens system 1A enlarges and projects onto a screen 8, via a plurality of lenses G1 to G16, image light emitted from, a light source 4 and modulated by DMDs 3r to 3b. A movable lens barrel 25 holds the lens G16, having positive power, which is positioned closest to the DMDs 3r to 3b. An outer tube 24 holds the movable lens barrel 25 to enable movement in the optical axis direction. Through thermal deformation at the time of an increase in temperature, the bimetal member 27 moves the movable lens barrel 25 in the optical axis direction so as to recede from the image formation devices which are the DMDs 3r to 3b.

## Claims

### Claim 1

A projection lens unit comprising:
a projection lens system which enlarges and projects image light from an image formation device onto a screen; and a lens barrel which holds lenses of the projection lens system, wherein
the lens barrel comprises:
a movable lens barrel which holds one or a plurality of lenses, among the lenses of the projection lens system, having positive power and positioned closest to a side of the image formation device;
a holding tube which holds the movable lens barrel so as to be movable in an optical axis direction;
a reference surface perpendicular to the optical axis;
a thermal deformation member including a bimetal member which is deformed so as to increase a thickness thereof at the time of a temperature increase and which is disposed between the reference surface and the movable lens barrel; and
an elastic member which presses the movable lens barrel and the bimetal member in the optical axis direction toward the image formation device against the reference surface.

### Claim 2 (depends on 1)

The projection lens unit according to claim 1, wherein the projection lens system further comprises a diaphragm, and wherein the lenses of the projection lens system include one or a plurality of lenses positioned on the side of the image formation device with respect to the diaphragm, having positive power, and having an Abbe number exceeding 70.

### Claim 3 (depends on 1)

The projection lens unit according to claim 1, wherein a focal length of the one or plurality of lenses held by the movable lens barrel is set so as to have the following relation to an equivalent in air of a back focal length:
1<f/LBair<5
f: focal length
LBair: the equivalent in air of the back focal length.

### Claim 4 (depends on 1)

The projection lens unit according to claim 1, wherein the number of lenses held by the movable lens barrel is two or less.

### Claim 5 (depends on 1)

The projection lens unit according to claim 1, wherein the projection lens system is a zooming lens system, and the movable lens barrel is held fixed during zooming.

### Claim 6 (depends on 1)

The projection lens unit according to claim 1, wherein the projection lens system is a telecentric optical system having an air equivalent back focal length equal to two or more times a diagonal length of the image formation device.

### Claim 7 (depends on 1)

The projection lens unit according to claim 1, wherein an inner peripheral surface or outer peripheral surface of the movable lens barrel is slidably in contact with the holding tube, and a length in the optical axis direction of the contact portion between the movable lens barrel and the holding tube is 15 mm or greater.

### Claim 8 (depends on 1)

The projection lens unit according to claim 1, wherein the bimetal member is flat or is ring-shaped with a depression on a low-expansion side.

### Claim 9 (depends on 1)

The projection lens unit according to claim 1, wherein
the movable lens barrel has a flange portion, and
the bimetal member is positioned between the reference surface and the flange portion.

### Claim 10

A projection lens unit comprising a projection lens system which enlarges and projects light from an image formation device onto a screen and a lens barrel which holds lenses of the projection lens system, wherein the lens barrel comprises:
a movable lens barrel which holds one or a plurality of lenses, among the lenses of the projection lens system, having positive power and positioned closet to a side of the imager formation device;
a holding tube which holds the movable lens barrel so as to be movable in an optical axis direction;
a reference surface perpendicular to the optical axis;
a thermal deformation member including a bimetal member which is deformed so as to decrease thickness thereof at the time of a temperature increase and which is disposed between the reference surface and the movable lens barrel; and
an elastic member which presses the movable lens barrel and the bimetal member in the optical axis direction toward the screen against the reference surface.

### Claim 11 (depends on 10)

The projection lens unit according to claim 10, wherein
the movable lens barrel has a flange portion, and
the bimetal member is positioned between the reference surface and the flange portion.

### Claim 12

A projection lens unit comprising: a projection lens system which enlarges and projects image light from an image formation device onto a screen; and a lens barrel which holds lenses of the projection lens system, wherein the lens barrel comprises:
a movable lens barrel which holds one or a plurality of lenses, among the lenses of the projection lens system, having positive power and positioned closest to a side of the image formation device;
a holding tube which holds the movable lens barrel, so as to be movable in an optical axis direction; and
a thermal deformation member which, through thermal deformation at the time of a temperature increase, moves the movable lens barrel in the optical axis direction so as to recede from the image formation device; and
a rotation-halting mechanism which impedes rotation of the movable lens barrel about the optical axis relative to the holding tube, and which enables setting of the rotational position of the movable lens barrel about the optical axis relative to the holding tube to a plurality of positions.

### Claim 13 (depends on 10)

The projection lens unit according to claim 10, wherein the projection lens system comprises a diaphragm, and wherein the lenses of the projection lens system include one or a plurality of lenses positioned on a side of the image formation device with respect to the diaphragm, positive power and having an Abbe numbers higher than 70.

### Claim 14 (depends on 10)

The projection lens unit according to claim 10, wherein the bimetal member is ring-shaped with a depression on a high-expansion side.

### Claim 15 (depends on 10)

The projection lens unit according to claim 10, wherein a focal length of the one or plurality of lenses held by the movable lens barrel is set so as to have the following relation to an equivalent in air of a back focal length:
1<f/LBair<5
f: focal length
LBair: the equivalent in air of the back focal length.

### Claim 16 (depends on 10)

The projection lens unit according to claim 10, wherein the number of lenses held by the movable lens barrel is two or less.

### Claim 17 (depends on 10)

The projection lens unit according to claim 10, wherein the projection lens system is a zooming lens system, and the movable lens barrel is held fixed during zooming.

### Claim 18 (depends on 10)

The projection lens unit according to claim 10, wherein the projection lens system is a telecentric optical system having an air equivalent back focal length equal to two or more times a diagonal length of the image formation device.

### Claim 19 (depends on 10)

The projection lens unit according to claim 10, wherein an inner peripheral surface or outer peripheral surface of the movable lens barrel is slidably in contact with the holding tube, and a length in the optical axis direction of the contact portion between the movable lens barrel and the holding tube is 15 mm or greater.

### Claim 20 (depends on 1)

The projection lens unit according to claim 1 wherein the thermal deformation member further includes a ring-shaped base, and wherein the bimetal member includes a plurality of bimetal members fastened to the ring-shaped base.

### Claim 21 (depends on 10)

The projection lens unit according to claim 10, wherein the thermal deformation member further includes a ring-shaped base, and wherein the bimetal member includes a plurality of bimetal members fastened to the ring-shaped base.

### Claim 22 (depends on 1)

The projection lens unit according to claim 1, wherein the reference surface is formed integrally with the holding tube.

### Claim 23 (depends on 10)

The projection lens unit according to claim 10, wherein the reference surface is formed integrally with the holding tube.

### Claim 24 (depends on 23)

The projection lens unit according to claim 23, wherein the holding tube holds the lenses positioned on the screen side with respect to the one or plurality of lenses held by the movable lens tube, and wherein an inner peripheral surface of the movable lens barrel is slidably in contact with the holding tube.