JP2015049340A - Projection optical system, image display device including the same, and method for adjusting image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection optical system that can favorably adjust curvature of an image plane even when temperature changes, and that can suppress degradation in resolution in a periphery of a screen.SOLUTION: A projection optical system 100 enlarges and projects an image formed on a display panel 1 onto a screen via a refractive optical system 2, and the projection optical system comprises a first lens group G1 that does not move upon focusing and one or more second lens groups G2 that move upon focusing. A diaphragm 3 is disposed in the first lens group G1, and a correction lens group CL is disposed in an enlarging side of the diaphragm 3. Curvature of an image plane induced by changes in temperature can be adjusted by moving the correction lens group CL in a direction of the optical axis. The first lens group G1 is composed of a first lens L1 to a ninth lens L9. In the second lens groups G2, a front second lens group G2F is composed of a tenth lens L10 to a twelfth lens L12, while a rear lens group G2R is composed of a thirteenth lens L13 and a fourteenth lens L14.

Description

  The present invention relates to a projection optical system that enlarges and projects an image formed on a display panel onto a screen via a refractive optical system, an image display apparatus including the projection optical system, and a method for adjusting the image display apparatus.

In recent years, a projector device is widely known as an image display device that enlarges and projects an image of a display panel onto a screen by a projection optical system. In recent years, in particular, there has been an increasing demand for an ultra-wide-angle front projection projector that can display a large screen while reducing the projection space. When the super wide angle is supported, a floating focus is used to correct the curvature of field.
When the projector device is used for a long time, it is due to a change with time of the optical element accompanying a temperature rise or a change of a member holding the optical element. Resolution deteriorates. One reason for this is due to the back focus shift. As means for eliminating the back focus shift in response to a temperature rise, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2010-256394), Patent Document 2 (Special) No. 2004-264570) and Patent Document 3 (Japanese Patent Laid-Open No. 2008-26864).
Among these, in Patent Document 1, the focal length of the projection lens associated with a temperature change is obtained by making the temperature coefficient of the expansion / contraction amount of the expansion / contraction member in the optical axis direction of the projection lens correspond to the temperature coefficient of increase / decrease in the focal length of the projection lens Is offset by the expansion and contraction of the elastic member.

In Patent Document 2, the cam ring is moved by changing the temperature coefficient of the cam ring that determines the position of the lens frame in the optical axis direction and the correction cylinder that determines the position of the cam ring in the optical axis direction. The back focus shift due to the temperature change is canceled.
Furthermore, in Patent Document 3, a projection lens unit incorporated in a projector has a movable lens barrel that can move in the optical axis direction, and the movable lens barrel is moved away from the image-forming optical element by bimetal thermal deformation. , The back focus shift is eliminated.

However, the conventional techniques described in Patent Documents 1 to 3 described above have the following problems.
That is, in the above-described conventional projection optical system, even if the back focus shift can be eliminated, the field curvature caused by the temperature change of the focus group cannot be adjusted. The problem remains that the resolution of the part deteriorates rapidly.
The present invention has been made in view of the above-described problem, and provides a projection optical system that can satisfactorily adjust the curvature of field even when the temperature rises and suppress degradation in resolution at the periphery of the screen. It is aimed.

The projection optical system according to the present invention achieves the above-described object,
In a projection optical system that enlarges and projects an image formed on a display panel onto a screen via a refractive optical system,
The refractive optical system includes a first lens group that is fixed at the time of focusing and one or more second lens groups that are moved at the time of focusing on an optical path from the reduction side to the magnification side.
In the first lens group, a diaphragm is disposed, and a correction lens group is disposed on the enlargement side from the diaphragm,
The light flux that passes from the entrance surface to the exit surface of the correction lens group is φ1 that is the thinnest light flux between the entrance surface and the exit surface, and the thickness of the light beam that passes through the stop is φ2. When
The aperture is defined by the following conditional expression (1):
(1) 1.0 <φ1 / φ2 <1.8
It is characterized by being arranged to satisfy.

According to the present invention,
In a projection optical system that enlarges and projects an image formed on a display panel onto a screen via a refractive optical system,
The refractive optical system includes a first lens group that is fixed at the time of focusing and one or more second lens groups that are moved at the time of focusing on an optical path from the reduction side to the magnification side.
In the first lens group, a diaphragm is disposed, and a correction lens group is disposed on the enlargement side from the diaphragm,
In particular, the thickness of the light beam that passes from the entrance surface to the exit surface of the correction lens group becomes the thinnest between the entrance surface and the exit surface is φ1, and the thickness of the light beam that passes through the stop is φ2. When
The aperture is defined by the following conditional expression (1):
(1) 1.0 <φ1 / φ2 <1.8
By being arranged to satisfy
By moving the correction lens group, it is possible to perform correction that contributes only to off-axis aberrations without contributing to axial aberrations in the projection optical system, thus maintaining the resolution at the center of the screen, It is possible to suppress resolution degradation at the periphery of the screen.

(A), (b) is a figure for demonstrating the structure of the projection optical system which concerns on the 1st Embodiment of this invention, (a) is ZY sectional drawing, (b) ) Is a movement locus diagram schematically showing the movement locus of each lens group when the projection optical system is focused from the long distance side to the short distance side. (A), (b) is a figure for demonstrating the projection optical system which concerns on 2nd Embodiment which provides a reflective optical system and dustproof glass in the expansion side rather than the refractive optical system in FIG. Among these, (a) is a ZY sectional view, and (b) is a movement locus diagram schematically showing the movement locus of each lens group when the projection optical system is focused from the long distance side to the short distance side. It is. (A), (b), (c), and (d) are graphs showing the field curvature in the projection optical system when the horizontal axis is the amount of displacement in the optical axis direction and the vertical axis is the angle of view. Among these, (a) is a graph showing the state of curvature of field at the design value, and (b) shows the deviation of the optical axis direction and the state of curvature of field when the temperature rises from the initial state. (C) is a graph showing the curvature of field when only the so-called back focus adjustment is performed, which is the distance between the tip of the lens and the display panel when the temperature rises, and (d) is the back focus. 6 is a graph showing a state in which correction of curvature of field and adjustment of back focus are performed in the projection optical system according to the present invention for the adjustment of the zoom lens. (A), (b) is a figure which shows the structure of the image display apparatus which concerns on the 3rd Embodiment of this invention, Among these, (a) is a projection optical system and reflection optical system which are shown in FIG. In addition, a ZY sectional view showing the configuration of an image display device including an illumination unit and various circuit units, (b) is a lens group when the projection optical system is focused from a long distance side to a short distance side. It is a movement locus | trajectory diagram which shows typically a movement locus | trajectory. (A) is ZY sectional drawing which shows the structure of Example (numerical example) 1 of the projection optical system based on the 4th Embodiment of this invention, (b) is a projection optical system far side. It is a movement locus | trajectory diagram which shows typically the movement locus | trajectory of each lens group when focusing to the near distance side from. It is a front view which shows typically the display panel formed by arrange | positioning 25 angles of view in an image formation area. (A), (b), (c) is a graph which respectively shows the result of having calculated the spot diameter projected from the projection optical system based on the lens data shown in the specific Table 2 of Example 1 shown in FIG. Among them, (a) is a graph showing a change in the RMS spot diameter at each angle of view when the distance to the screen is a long distance (80 inches), and (b) is a case of a reference distance (60 inches). (C) is a similar graph in the case of a short distance (48 inches). (A), (b), and (c) show specific lens data when the temperature of the projection optical system based on the lens data shown in Table 2 of Example 1 shown in FIG. Is a graph showing the results of calculating the RMS spot diameter projected from the projection optical system for the case where the change is as shown in Table 7, in which (a) shows the distance to the screen is a long distance (80 inches). ) Is a graph showing a change in the RMS spot diameter at each angle of view, (b) is a similar graph in the case of a reference distance (60 inches), and (c) is a short distance (48 inches). It is the same graph in the case of. (A), (b), and (c) are the cases where the specific lens data changes as shown in Table 7 as the temperature of the projection optical system of Example 1 shown in FIG. The result of calculating the RMS spot diameter projected from the projection optical system in which specific lens data is changed as shown in Table 9 by moving the correction lens of the projection optical system by a predetermined distance in the direction away from the display panel. Among these, (a) is a graph showing changes in the RMS spot diameter at each angle of view when the distance to the screen is a long distance (80 inches), and (b) is a reference distance (60). (C) is a similar graph for a short distance (48 inches). (A) is ZY sectional drawing which shows the structure of Example (numerical example) 2 of the projection optical system which concerns on the 5th Embodiment of this invention, (b) is a long distance side of a projection optical system. It is a movement locus | trajectory diagram which shows typically the movement locus | trajectory of each lens group when focusing to the near distance side from. It is a typical front view of the display panel formed by arranging 25 angles of view in the image forming area. (A), (b), (c) is a graph which respectively shows the result of having calculated the spot diameter projected from the projection optical system based on the lens data shown in the specific Table 11 of Example 2 shown in FIG. Among them, (a) is a graph showing a change in the RMS spot diameter at each angle of view when the distance to the screen is a long distance (80 inches), and (b) is a case of a reference distance (60 inches). (C) is a similar graph in the case of a short distance (48 inches). (A), (b), and (c) show a temperature increase of 40 ° C. with respect to the projection optical system based on the lens data shown in Table 11 of Example 2 shown in FIG. When lens data changes as shown in Table 17, it is a graph which shows the result of having calculated the RMS spot diameter projected from a projection optical system, respectively, (a) is a long-distance distance to a screen among these. It is a graph which shows the change of the RMS spot diameter in each view angle in the case of (80 inches), (b) is the same graph in the case of a reference distance (60 inches), (c) is a short distance ( 48 inches) is a similar graph. (A), (b), and (c) are states in which the projection optical system of Example 2 shown in FIG. The result of calculating the RMS spot diameter projected from the projection optical system in which specific lens data is changed as shown in Table 19 by moving the correction lens of the projection optical system by a predetermined distance in the direction away from the display panel, respectively. Of these graphs, (a) is a graph showing changes in the RMS spot diameter at each angle of view when the distance to the screen is a long distance (80 inches), and (b) is a reference distance (60 inches). ) In the case of a short distance (48 inches). (A), (b), (c) is a projection optical system according to Example 1 shown in FIG. 5, in which a lens other than the correction lens, for example, a sixth lens is moved by 0.15 mm in the direction approaching the display panel. 6 is a graph showing changes in the RMS spot diameter with respect to each angle of view at the time, (a) is a long distance, (b) is a reference distance, and (c) is a graph in each case of a short distance.

Hereinafter, based on an embodiment of the present invention, a projection optical system according to the present invention, an image display apparatus including the same, and an adjustment method of the image display apparatus will be described in detail with reference to the drawings.
Before describing specific examples, a conceptual or principle embodiment of the present invention will be described.
First, in the projection optical system, the principle of the occurrence of the field curvature and the adjustment method when the temperature rises will be described using the conceptual graph of FIG.
Each graph shown in FIGS. 3A, 3 </ b> B, 3 </ b> C, and 3 </ b> D shows the curvature of field in the projection optical system when the horizontal axis is the amount of displacement in the optical axis direction and the vertical axis is the angle of view. Represents each.
Among these, (a) shows the state of curvature of field at the design value, and the curvature of field is well corrected.
(B) shows the state of field curvature when the temperature rises, and a large field curvature is generated off-axis and in the optical axis direction.
(C) shows the field curvature when only the back focus (the distance between the lens tip and the display panel) is adjusted when the temperature rises. In this state, the deviation in the optical axis direction can be eliminated. However, the curvature of field that has largely occurred off-axis remains.

(D) shows the state of curvature of field in the projection optical system according to the present invention, and the adjustment of the back focus at the time of temperature rise is performed together with the means for eliminating the back focus shift caused by the known temperature rise. By moving the correction lens of the projection optical system according to the invention, it is possible to satisfactorily adjust the curvature of field that has largely occurred off-axis.
All the embodiments have a structure that cancels back focus shift due to temperature change. Specifically, this is the structure described in FIG. A projection optical system holding member (corresponding to the frame member 91) for holding the projection optical system and holding it in the housing (housing) of the projector device, a holder member (corresponding to the holder member 92) for holding the display panel, and the projection optical system An elastic member (corresponding to the elastic member 94) that connects the holding member and the holder member is provided. This expansion member expands due to temperature fluctuations, and when the back focus shifts to the downstream side of the optical path due to temperature rise, the expansion member causes the temperature coefficient of the expansion / contraction amount of the expansion member to shift the display panel to the downstream side of the optical path. It has been decided.
The structure for canceling the back focus shift due to the temperature change is not limited to the above, and the structures disclosed in Patent Document 2, Patent Document 3, and the like may be used.

In particular, in the case of an ultra-wide-angle projection optical system, the effect of adjusting the field curvature shown in (d) above is great.
Based on the above, the following configuration is indispensable for maintaining good resolution even when the temperature rises. When the projector device is used for a long time, the resolution deteriorates due to a change in the optical element accompanying a temperature rise with time and a change in the member holding the optical element. One reason for this is due to a back focus shift. By eliminating the back focus shift, resolution degradation can be suppressed over the entire screen. However, even if the back focus shift can be eliminated, the field curvature caused by the temperature change of the focus group cannot be adjusted, so the resolution of the screen periphery rapidly deteriorates with respect to the screen center. End up.

Therefore, in the present invention, in order to satisfactorily adjust the curvature of field caused by the temperature change of the focus group,
In a projection optical system that enlarges and projects an image formed on a display panel onto a screen via a refractive optical system,
The refractive optical system includes a first lens group that is fixed at the time of focusing on the optical path from the reduction side to the magnification side, and has a positive refractive power, and one or more lens groups that move at the time of focusing. A second lens group having a refractive power of
In the first lens group, a stop (aperture stop) is disposed, and a correction lens group is disposed on the enlargement side from the stop,
The light flux that passes from the entrance surface to the exit surface of the correction lens group is φ1 that is the thinnest light flux between the entrance surface and the exit surface, and the thickness of the light beam that passes through the stop is φ2. When
The aperture is defined by the following conditional expression (1):
(1) 1.0 <φ1 / φ2 <1.8
It is characterized by being arranged so that the above may be satisfied (corresponding to claim 1).

When the light flux from the entire area of the display panel passes through the projection optical system, the thickness of the light flux at any position in the optical axis direction (here, the length parallel to the short side direction of the display panel) is φ. It is defined as
The conditional expression (1) is a conditional expression for satisfactorily adjusting the field curvature. When the upper limit of the conditional expression (1) is exceeded, the field curvature is over-adjusted and falls below the lower limit of the conditional expression (1). And the field curvature are under-adjusted, and in both cases, the field curvature cannot be adjusted well.
By adopting such a configuration, it is possible to realize a projection optical system that can satisfactorily adjust the curvature of field that occurs with changes in temperature and suppress degradation in resolution at the periphery of the screen.
Normally, even if the curvature of field can be corrected by moving the lens, other aberrations (spherical aberration, coma aberration) are deteriorated. As a result, the resolution at the center of the screen should also deteriorate. However, as described above, since the correction lens arranged at the position satisfying the conditional expression (1) on the enlargement side is moved from the stop as described above, in the projection optical system, the on-axis aberration is reduced. Therefore, correction that does not contribute but contributes only to off-axis aberrations can be performed.
Therefore, it is possible to suppress degradation in resolution at the periphery of the screen while maintaining resolution at the center of the screen.

Further, in order to satisfactorily adjust the curvature of field, it is desirable that the stop be disposed at a position where the reduction side of the refractive optical system is non-telecentric (corresponding to claim 2).
As described above, the stop is disposed at a position where the reduction side of the refractive optical system is non-telecentric, so that the height of the light beam passing through the correction lens can be increased, and the effect of adjusting the curvature of field is improved. be able to.
In the projection optical system configured as described above, the correction lens group is moved along the optical axis so that the focal length of the entire refractive optical system increases as the temperature rises. You may comprise so that the curvature of field which generate | occur | produced with the temperature rise can be adjusted (corresponding to Claim 3).
In the projection optical system configured as described above, when the temperature of the refractive optical system rises, the correction lens group is moved in a direction away from the display panel. It is desirable that the curvature of field can be adjusted (corresponding to claim 4).
This prescribes the moving direction of the correction lens group, and it is possible to satisfactorily adjust the curvature of field both when the temperature rises and when the temperature falls.

In the projection optical system configured as described above, the focal length of the correction lens group (the combined focal length in the case of two or more lenses) is defined as f1, and the refractive optical system is combined. When the focal length is f2,
The following conditional expression (2):
(2) 1.6 <f1 / f2 <2.0
Is preferably satisfied (corresponding to claim 5).
Conditional expression (2) defines the power of the correction lens group. If the upper limit of conditional expression (2) is exceeded, the power becomes too strong and the field curvature is over-adjusted. On the other hand, if the lower limit of conditional expression (2) is not reached, the power becomes too weak and the field curvature becomes insufficiently adjusted.
When the maximum movement amount that can move the correction lens group in the optical axis direction is Δd, and the paraxial lateral magnification of the refractive optical system is M,
The following conditional expression (3):
(3) 0.06 <Δd / M <0.09
Is preferably satisfied (corresponding to claim 6).

Conditional expression (3) defines the maximum amount of movement by which the correction lens group can be moved. If the upper limit of conditional expression (3) is exceeded, the movement amount becomes too large and the field curvature is over-adjusted. Become. On the other hand, if the lower limit of conditional expression (3) is not reached, the amount of movement becomes too small, and the field curvature becomes insufficiently adjusted.
In the projection optical system, it is preferable that all the correction lenses are spherical lenses (corresponding to claim 7).
Thus, by forming the correction lens with only a spherical lens without forming an aspherical surface, it is possible to reduce costs while suppressing curvature of field.
In addition, by using the projection optical system as described above, it is possible to provide an image display device that can adjust the curvature of field well even when the temperature rises and suppress resolution degradation at the periphery of the screen ( Corresponding to claim 8).
As an adjustment method for an image display apparatus including a projection optical system that enlarges and projects an image formed on a display panel onto a screen via a refractive optical system, the following method is preferable.

That is, the refractive optical system includes a first lens group that is fixed at the time of focusing and one or more second lens groups that are moved at the time of focusing on an optical path from the reduction side to the magnification side.
In the first lens group, a diaphragm is disposed, and a correction lens group is disposed on the enlargement side from the diaphragm,
What is necessary is just to adjust so that the said correction | amendment lens group may be moved to an optical axis direction at the time of temperature fluctuation.
It is to be noted that the adjustment of the field curvature is adjusted by the movement of the correction lens, and the deviation in the optical axis direction is adjusted by a known method, for example, the method described in Patent Documents 1 to 3 described above. do it.

[First Embodiment]
Next, a plurality of embodiments of the projection optical system according to the present invention will be described sequentially.
FIGS. 1A and 1B are diagrams for explaining the configuration of the projection optical system according to the first embodiment of the present invention. Among these, FIG. 1A shows ZY of the projection optical system. Sectional view (b) is a movement locus diagram schematically showing the movement locus of each lens group when the projection optical system is focused from the long distance side to the short distance side.
In FIG. 1A, the refractive optical system 2 has a positive refractive power composed of the first lens L1 to the ninth lens L9 sequentially on the optical path from the reduction side to the enlargement side where the display panel 1 is disposed. The first lens group G1, the front second lens group G2F having negative refractive power composed of the tenth lens L10 to the twelfth lens L12, and the positive rear power consisting of the thirteenth lens L13 to the fourteenth lens L14 The second side lens group G2R is configured.
The front second lens group G2F and the rear second lens group G2R constitute a second lens group G2.
The first lens group G1 includes a diaphragm 3. The diaphragm 3 is arranged at a position where the reduction side of the refractive optical system 2 is non-telecentric.
In the first lens group G1, a correction lens CL (which may be referred to as a third lens L3) for correcting curvature of field is arranged on the enlargement side from the stop 3.

The first lens group G1 is fixed during focusing, and the second lens group G2 moves during focusing.
Of the second lens group G2, the front side second lens group G2F and the rear side second lens group G2R are on the optical axis when focusing from the long distance side to the short distance side, as shown in FIG. Are moved with different movement trajectories on the optical axis.
The correction lens CL functions to adjust the curvature of field caused by the temperature change by moving in the optical axis direction. More specifically, when the temperature of the refractive optical system 2 rises, the correction lens group CL is moved in the direction away from the display panel 1 (the right direction in FIG. 1), and is generated as the temperature rises. It is configured so that the curved curvature of field can be adjusted.
In the projection optical system 100, the display panel 1 is disposed at the most reduction side end of the refractive optical system 2, and an image formed on the display panel 1 is enlarged and projected onto a screen (not shown) via the refractive optical system 2. To do.
If the display panel 1 uses DMD (Digital Micro-mirror Device) or the like, a small and light projection optical system can be realized.

By using a plurality of display panels 1 such as red, green, and blue, irradiating illumination light transmitted through the color filter to each of them, and causing the light synthesized by the color synthesizing means to enter the projection optical system A color image can be projected on the screen.
A thin panel (for example, about 1 mm) transparent panel is disposed immediately before the display panel 1.
In FIG. 1, the Z direction is the optical axis direction, and the Y direction is a direction perpendicular to the optical axis and parallel to the short side of the display panel 1. Α is a rotation angle around the X axis orthogonal to the ZY cross section.
According to the projection optical system 100 according to the first embodiment configured as described above, it is possible to satisfactorily adjust the field curvature even when the temperature rises, and to suppress the resolution deterioration of the peripheral portion of the screen.

[Second Embodiment]
Next, the projection optical system according to the second embodiment will be described with reference to FIGS.
Among these, FIG. 2A is a ZY sectional view of the projection optical system, and FIG. 2B is a schematic diagram showing the movement locus of each lens group when the projection optical system is focused from a long distance to a short distance. FIG.
In addition to the first embodiment shown in FIG. 1, the projection optical system 100 shown in FIG. 2A has a reflection optical system 4, that is, a reflection optical system 4 </ b> A and a reflection optical system on the enlargement side with respect to the refractive optical system 2. The difference is that the system 4B and the dustproof glass 5 are provided. The refractive optical system 2 is substantially the same as that of the first embodiment shown in FIG.
In FIG. 2, the reflection optical system 4A is a plane mirror (or free-form surface mirror), and the reflection optical system 4B is a concave mirror composed of a free-form surface. In the refractive optical system 2, an intermediate image of the display panel 1 is formed once by the first lens group G1 and the second lens group G2. The intermediate image is configured to greatly jump up by the reflection optical system 4A and the reflection optical system 4B which are non-optical axis optical systems, pass through the dust-proof glass 5 which is a transparent member, and project onto a screen (not shown). Yes.

[Third Embodiment]
Next, an image display apparatus according to the third embodiment will be described with reference to FIGS.
FIG. 4A is a ZY sectional view of the image display device, and FIG. 4B schematically shows the movement trajectory of each lens group when the projection optical system is focused from a long distance to a short distance. It is a movement locus shown.
The image display device 200 shown in FIG. 4A is different in that it includes an illumination unit 101 and various circuit units 102 in addition to the projection optical system 100 according to the second embodiment shown in FIG. ing.
The refractive optical system 2 is substantially the same as the first embodiment shown in FIG. 1, and the reflective optical systems 4A and 4B are refracted according to the second embodiment shown in FIG. Since it is almost the same as the refractive optical system related to the optical system 100, a duplicate description is omitted.
4A, an image display device 200 according to the third embodiment includes an illumination unit 101 for illuminating the display panel 1 and various circuit units 102 inside the device.
The illumination unit 101 illuminates the display panel 1, and a halogen lamp, a xenon lamp, a metal halide lamp, an ultrahigh pressure mercury lamp, an LED, or the like can be used as a light source. For example, these light sources preferably irradiate the display panel 1 with a uniform illuminance distribution through an integrator rod or an illumination lens as appropriate.

According to the image display device configured as described above, the image of the display panel 1 irradiated with the uniform illuminance emitted from the illumination unit 101 is the coaxial optical from the first lens group G1 and the second lens group G2. Once formed as an intermediate image by the system, the intermediate image is magnified by the reflecting optical system 4A and the reflecting optical system 4B, which are non-coaxial optical systems, and projected onto a screen (not shown) as an enlarged image.
At the time of focusing, the first lens group G1 does not move, and the front lens group G2F and the rear lens group G2R as the focusing lens group are displayed, for example, when focusing from the long distance side to the short distance side. It moves in a direction away from the panel 1 and with a different amount of movement.
Further, the correction lens CL is located on the enlargement side of the stop 3 of the first lens group G1 as the fixed lens group in order to satisfactorily correct the field curvature generated by the temperature change of the second lens group G2 as the focusing lens group. The positioned correction lens group CL is moved in the optical axis direction.

Hereinafter, embodiments of the projection optical system of the present invention and specific examples (numerical examples) will be described.
The meanings of common symbols in the first and second embodiments described below are as follows.
r: radius of curvature d: spacing between surfaces nd: refractive index of d-line νd: Abbe number of d-line α: linear expansion coefficient at −30 ° C. to 70 ° C. (unit: × 10 ⁻⁷ / ° C.)
β: relative refractive index temperature coefficient of e-line at 20 ° C. or higher (unit: × 10 ⁻⁶ / ° C.)
The aspherical shape used here is such that the reciprocal of the paraxial radius of curvature (paraxial curvature) is C, the height from the optical axis is Y, the conic constant is K, and the above-mentioned aspherical coefficients are used. The shape is specified by giving a paraxial radius of curvature, a conical constant, and an aspheric coefficient to Equation (4), where X is an aspheric amount in the optical axis direction.

  Here, the meanings of symbols used in the expression (4) representing the aspheric surface are as follows.

X: distance from the tangential plane at the aspherical vertex of the aspheric surface at height Y from the optical axis Y: height from the optical axis r: paraxial radius of curvature of the aspheric surface K: cone multiplier A4, A6, A8, A10, A12: the aspheric coefficients, among the numerical example, E-XY ^{is 10 -XY} have the meanings, E + XY is the meaning of 10 ^{+ XY.}

  The polynomial free-form surface is expressed by the following equation (5).

  A surface comprising a polynomial free-form surface is defined by the following equation (5) using a local orthogonal coordinate system (X, Y, Z) with the surface vertex as the origin.

However, the meanings of the symbols used in the above formula (5) are as follows.
Z: Amount of displacement in the Z-axis direction at the position of height h (based on the surface vertex)
h: Height in a direction perpendicular to the Z axis (h ² = X ² + Y ² )
c: paraxial curvature k: conic coefficient C _j : polynomial free-form surface coefficient The free-form surface term is expressed by the following equation (6).

FIG. 5 (a) shows the configuration of Example (Numerical Example) 1 of the projection optical system according to the fourth embodiment of the present invention, and the state of light passing through the lens and the reflection by the reflection optical system. It is ZY sectional drawing which shows the optical path which shows the reflective state of a light ray. FIG. 5B is a movement locus diagram schematically showing the movement locus of each lens group when the projection optical system is focused from the long distance side to the short distance side.
The projection optical system 100-1 shown in FIG. 5A is a positive lens including a first lens L1 to a ninth lens L9 sequentially from the reduction side (panel 1-1 side) to the enlargement side along the optical axis. A first lens group G1-1 having refracting power, a front second lens group G2F-1 having negative refracting power consisting of a tenth lens L10 to a twelfth lens L12, and a thirteenth lens L13 to a fourteenth lens L14. And a rear second lens group G2R-1 having a positive refractive power.
The front second lens group G2F-1 and the rear second lens group G2R-1 are both moving lens groups that move during focusing, and are collectively referred to as a second lens group G2-1. In addition, the first lens group G1-1 and the second lens group G2-2 are referred to herein as a refractive optical system 2-1.
The first lens group G1-1, which is a fixed lens group at the time of focusing, has a diaphragm 3-1, and the diaphragm 3-1 is disposed at a position where the reduction side of the refractive optical system 100-1 is non-telecentric. The

The first lens group G1-1 is provided with a correction lens CL-1 that adjusts the curvature of field caused by the temperature change.
Here, the refractive optical system 2-1 according to Example 1 will be described more specifically.
In FIG. 5, in the refractive optical system 2-1 of Example 1, the first lens group G <b> 1 has a convex surface directed toward the reduction side in order from the reduction side (display panel 1-1 side) to the enlargement side. A first lens L1 composed of a positive meniscus lens, a second lens L2 composed of a biconvex lens having a convex surface having a larger curvature than the magnification side toward the reduction side, and a biconvex lens having a convex surface having a curvature larger than the reduction side toward the magnification side. A third lens L3, a fourth lens L4 composed of a negative meniscus lens with a concave surface facing the reduction side, a fifth lens L5 composed of a biconvex lens with a convex surface having a larger curvature than the reduction side facing the magnification side, and from the reduction side From a sixth lens composed of a biconcave lens with a large curvature facing the magnification side, a seventh lens L7 composed of a positive meniscus lens with a convex surface facing the magnification side, and a negative meniscus lens with a convex surface facing the magnification side That the eighth lens L8, composed of the ninth lens L9 Metropolitan curvature than the reduction side is a biconvex lens having a large convex surface on the enlargement side.
Of the lenses constituting the first lens group G1-1, the two lenses, the third lens L3 and the fourth lens L4, and the seventh lens L7 and the eighth lens L8, are closely bonded to each other. The cemented lens is integrally joined to form a cemented lens composed of two lenses.

The stop 3-1 is interposed between the fifth lens L5 and the sixth lens L6 that constitute the first lens group G1-1.
Of the second lens group G2-1, the front second lens group G2F-1 is enlarged from the tenth lens L10, which is a positive meniscus lens having a convex surface directed toward the reduction side, in order from the reduction side to the enlargement side. An eleventh lens L11 composed of a negative meniscus lens having a concave surface facing the side, and a twelfth lens L12 composed of a biconcave lens having a concave surface having a larger curvature than the reduction side facing the magnification side.
Further, in the second lens group G2-1, the rear second lens group G2R-1 is a thirteenth lens L13 formed of a negative meniscus lens having a concave surface directed toward the enlargement side in order from the reduction side toward the enlargement side. And a fourteenth lens L14 composed of a biconvex lens having a convex surface having a larger curvature than that on the enlargement side and directed toward the reduction side.
In Example 1, the optical data of each optical element is as shown in Table 1 below.

In Table 1, the lens surface with the surface number indicated by “* (asterisk)” in the remarks column is an aspherical surface.
That is, in Table 1, the third surface, the fourth surface, the nineteenth surface, the twenty-third surface, the twenty-third surface, the twenty-fourth surface, the twenty-fifth surface, the twenty-sixth surface, the twenty-seventh surface, which are marked with “*”. Each optical surface of the 28th surface is an aspheric surface, and the parameters of each aspheric surface in the equation (4) are as shown in the following table (2). The ninth lens L9 as the correction lens CL is formed of a spherical lens without forming an aspherical surface.

Further, the intermediate image of the display panel 1-1 emitted from the final lens surface of the second rear lens group G2R-1 is sequentially reflected by the free-form surface mirror 4A-1 and the free-form surface mirror 4B-1, and this reflection optics. For example, although not shown in FIG. 5 through the dust-proof glass 5-1 disposed on the enlargement side from the system 4-1, it is emitted to the right side (enlargement side) of FIG. The image is projected onto a screen arranged along the vertical direction, and the image on the display panel 1-1 is enlarged and projected.
Here, the pixel size, the horizontal and vertical sizes of the display panel 1-1 in Example 1, and the distance from the optical axis to the lower side of the display panel 1-1 are as shown in Table 3 below.

In Table 3, the display panel 1-1 is assumed to be a digital micromirror device whose diagonal is 0.65 inches. However, the size and type of the display panel 1-1 are not limited to this. For example, the diagonal dimension of the display panel 1-1 may be 0.55 inches, and the type is transmissive. Or a reflective liquid crystal panel.
Moreover, although the distance from the optical axis to the lower side of the display panel 1-1 is separated by 1.413 mm in Table 3, this distance can also be arbitrarily changed.
The position of the surface vertex of the free-form surface mirror 4A-1 of the reflective optical system 4-1 is the intersection (Z, Y) of the plane including the display panel 1-1 and the optical axis in the ZY cross section shown in FIG. = (0,0), the position is fixed at (Z, Y) = (179.463, -9364).
The position of the surface vertex of the other free-form surface mirror 4B-1 is the intersection of the plane including the display panel 1-1 and the optical axis in the ZY cross section shown in FIG. 5 (Z, Y) = (0, 0). ), The position is fixed at (Z, Y) = (191.409, 70.687).
A surface comprising a polynomial free-form surface is defined by the above equation (5) using a local orthogonal coordinate system (X, Y, Z) with the surface vertex as the origin, and the shape is given by giving a polynomial free-form surface coefficient C _j Identify.
The free-form surface coefficient (C _j ) of the polynomial free-form surface of the 30th surface that is the reflection surface of the free-form surface mirror 4A-1 in the reflective optical system 4-1, is as shown in the following table (a). The free-form surface coefficient (C _j ) of the polynomial free-form surface of the 31st surface, which is the reflection surface of the free-form surface mirror 4B, is as shown in Table 4 (b) below.

On the enlarged side of the free-form curved mirror 4B-1, a dustproof glass 5 that is formed with a constant thickness (3.0 mm) as a whole is disposed.
Since the dust-proof glass 5 has no optical power, even if there is a slight error in the mounting position of the dust-proof glass 5, the image quality of the image is less affected. And although illustration was abbreviate | omitted in the expansion side (FIG. 5 right side) of this dustproof glass 5-1, arrangement | positioning of the projection surface of a screen is planned substantially parallel to an optical axis (Z direction).
In the projection optical system 100-1 according to Example 1 configured as described above, the light beam emitted from the display panel 1-1 enters the first lens group G1-1 of the refractive optical system 2-1, and After sequentially passing through the first lens group G1-1 and the second lens group G2-1, it is folded back by the free-form surface mirror 4A-1, and then reflected by the free-form surface mirror 4B-1, via the dust-proof glass 5-1. Projected onto a screen (not shown).
During focusing, the first lens group G1 does not move. For example, when focusing from the long distance side to the short distance side, the front second lens group G2F-1 of the second lens group G2 is a display panel. The rear second lens group G2R-1 moves in a direction away from 1-1, and moves in a direction away from the display panel 1-1 by a different movement amount from the front second lens group G2F.

Specifically, when the front second lens group G2F-1 and the rear second lens group G2R-1 are moved to the short distance side through the reference from the long distance side, the variable lens group interval is As shown in Table 5.
That is, the lens distance d18 between the ninth lens CL and the tenth lens L10, the distance d24 between the twelfth lens L12 and the thirteenth lens L13, the distance d28 between the fourteenth lens L14 and the dummy surface 29th surface, and the 35th surface. The distance d35 between the image plane and the image plane changes as shown in Table 5 as the distance d35 moves from the long distance side to the reference to the short distance side.

  Table 6 shows specific examples of the Y, Z, and α eccentricities of the 29th to 34th surfaces.

Next, in the case where the projection optical system 100 according to Example 1 shown in FIG. 5 is in a temperature environment as designed, and a change in the RMS spot diameter when a temperature increase of 40 ° C. occurs with respect to this temperature environment. 7, FIG. 8, FIG. 9 and Table 1, Table 7, Table 8, Table 9, and Table 10 will be described.
First, the specific data of the lens data of the projection optical system 100-1 according to Example 1 shown in FIG. 5 is as shown in Table 1. The projection optical system 100-1 has a temperature rise of 40 ° C. In this case, specific lens data changes as shown in Table 7 below.

  The surface distances d18, d24, d28, and d35 in the front lens group G2F-1, the rear lens group G2R-1, the reflective optical system 4-1, etc. having the focus function at that time change as shown in Table 8 below. .

Further, in comparison with the RMS spot diameter, the RMS spot diameter of the projection optical system 100-1 based on the lens data as designed values shown in Table 1 of Example 1 is as shown in FIG.
7A shows a case where the distance to the screen is a long distance (80 inches), FIG. 7B shows a case where the reference distance is 60 inches, and FIG. 7C shows a case where the distance is 48 inches. 6 shows changes in the RMS spot diameter (unit: mm) at each angle of view, and it can be seen that the spot diameter is sufficiently small and almost no field curvature occurs.
On the other hand, when the temperature of the projection optical system 100-1 based on the lens data of Example 1 is increased by 40 ° C., as described above, the lens data changes as shown in Table 7, and the RMS spot is changed. As shown in FIG. 8, although the back focus shift is separately eliminated, the spot diameter away from the optical axis is remarkably large with respect to the angle of view near the optical axis.
A specific lens when the correction lens CL-1 for correcting the curvature of field is moved in the direction (enlargement side) away from the display panel 1-1 by 0.5 mm with respect to the projection optical system 100 in this state. The data is as shown in Table 9 below.

  Thus, when the correction lens CL-1 is moved from the display panel 1-1 to the enlargement side by 0.5 mm, the distance d16 between the 16th surface of the eighth lens L8 and the 17th surface of the correction lens CL, the correction lens CL. The distance d18 between the eighteenth surface and the nineteenth surface of the tenth lens L10, the distance d24 between the twenty-fourth surface of the twelfth lens L12 and the twenty-fifth surface of the thirteenth lens L13, the twenty-eighth surface and the dummy surface 29 of the fourteenth lens L14. Interval d28 varies as shown in Table 10, respectively.

As shown in the lens data in Table 9, the lens data obtained by moving the correction lens CL-1 by a predetermined amount (in this example, 0.5 mm) are shown in FIGS. 9A, 9B, and 9C. As shown, the spot diameter at the field angle away from the optical axis is effectively suppressed, and a spot diameter comparable to the field angle near the optical axis is obtained.
If the spot diameter is about one pixel, it can be determined that a good resolution is obtained.
That is, by moving the correction lens CL-1, the curvature of field can be satisfactorily adjusted, and resolution degradation at the periphery of the screen can be suppressed.
Table 7 is a specific example of lens data when the temperature rises by 40 ° C. with respect to the lens data of Example 1 shown in Table 1. As described above, it is a specific example of the lens interval of the focus lens group (second lens group G2-1) at that time. Here, it is assumed that the shift of the back focus due to the temperature rise is eliminated by any one of the conventional techniques such as Patent Documents 1 to 3 described above. In the calculation of the lens data shown in Table 7, it is assumed that the radius of curvature, the surface interval, and the refractive index change under the following conditions 1) to 4) when the temperature rises.

1) Curvature radius: varies with linear expansion coefficient α.
2) Lens thickness: varies with linear expansion coefficient α.
3) Distance between lenses: (design value interval) + (change in linear expansion coefficient α of holding member) − (change in lens wall thickness at linear expansion coefficient α)
However, it was assumed that holding member: aluminum (linear expansion coefficient α: 283 × 10 −7 / ° C.).
The holding member may be made of a material other than aluminum, such as magnesium alloy (linear expansion coefficient α: 260 × 10 ⁻⁷ / ° C.) or plastic (linear expansion coefficient α: 600 × 10 −7 / ° C.). Also good.
4) Refractive index: Varies with the relative refractive index temperature coefficient β.

Next, Example (Numerical Example) 2 of the projection optical system according to the fifth embodiment of the present invention will be described with reference to FIG. 10A which is a ZY sectional view. FIG. 10B is a movement locus diagram schematically showing the movement locus of each lens group when the projection optical system is focused from the long distance side to the short distance side.
A projection optical system 100-2 shown in FIG. 10A is a positive lens including a first lens L1 to a ninth lens L9 sequentially from the reduction side (panel 1-2 side) to the enlargement side along the optical axis. A first lens group G1-2 having refracting power, a front second lens group G2F-2 having negative refracting power composed of a tenth lens L10 to a twelfth lens L12, and a thirteenth lens L13 to a fourteenth lens L14. And a rear second lens group G2R-2 having a positive refractive power.
Both the front second lens group G2F-2 and the rear second lens group G2R-2 are movable lens groups that move during focusing, and are collectively referred to as a second lens group G2-2. In addition, the first lens group G1-2 and the second lens group G2-2 are herein referred to as a refractive optical system 2-2.
The first lens group G1-2, which is a fixed lens group at the time of focusing, has a stop 3-2, and the stop 3-2 is disposed at a position where the reduction side of the refractive optical system 100-2 is non-telecentric. The

The first lens group G1-2 is provided with a correction lens CL-2 that adjusts the curvature of field caused by the temperature change.
Here, the refractive optical system 2-2 according to Example 2 will be described more specifically.
10, in the refractive optical system 2-2 of Example 2, the first lens group G1-2 has a convex surface on the reduction side in order from the reduction side (display panel 1-2 side) to the enlargement side. A first lens L1 composed of a positive meniscus lens directed to the second lens L2, a second lens L2 composed of a biconvex lens having a convex surface having a larger curvature than the magnification side toward the reduction side, and a convex surface having a curvature larger than the reduction side toward the magnification side. A third lens L3 made of a convex lens, a fourth lens L4 made of a negative meniscus lens having a concave surface facing the reduction side, a fifth lens L5 made of a biconvex lens with a convex surface having a larger curvature than the reduction side directed to the magnification side, A sixth lens composed of a biconcave lens with a concave surface having a larger curvature than the reduction side facing the magnification side, a seventh lens L7 composed of a positive meniscus lens with the convex surface facing the magnification side, and a negative meniscus lens having a convex surface facing the magnification side The eighth lens L8 made of, and a ninth lens L9 Metropolitan curvature than the reduction side is a biconvex lens having a large convex surface on the enlargement side.
Among the lenses constituting the first lens group G1-2, the two lenses, the third lens L3 and the fourth lens L4, and the seventh lens L7 and the eighth lens L8, are closely attached to each other. The cemented lens is integrally joined to form a cemented lens composed of two lenses.

The stop 3-2 is interposed between the fifth lens L5 and the sixth lens L6 that constitute the first lens group G1-1. More specifically, the stop 3-2 is arranged at a position where the reduction side of the refractive optical system is non-telecentric.
Among the second lens groups G2-2, the front second lens group G2F-2 is reduced in order from the reduction side to the enlargement side, the tenth lens L10 including a positive meniscus lens having a convex surface directed toward the reduction side. An eleventh lens L11 composed of a negative meniscus lens having a concave surface having a larger curvature than the reduction side facing the enlargement side, and a twelfth lens L12 composed of a biconcave lens having a concave surface having a curvature larger than the reduction side facing the magnification side.
Of the second lens group G2-2, the rear second lens group G2R-2 is a thirteenth lens L13 formed of a negative meniscus lens having a concave surface facing the enlargement side in order from the reduction side to the enlargement side. And a fourteenth lens L14 composed of a biconvex lens having a convex surface having a larger curvature than that on the enlargement side and directed toward the reduction side.
In Example 2, the optical data of each optical element is as shown in Table 11 below.

In Table 11, the lens surface having the surface number indicated with “* (asterisk)” in the remarks column is an aspherical surface.
That is, in Table 11, the third surface, the fourth surface, the nineteenth surface, the twenty-first surface, the twenty-third surface, the twenty-fourth surface, the twenty-fifth surface, the twenty-sixth surface, the twenty-seventh surface, which are marked with “*”. Each optical surface of the 28th surface is an aspheric surface, and parameters of each aspheric surface in the equation (4) are as shown in the following table (12).

The intermediate image of the display panel 1-2 emitted from the final lens surface of the rear second lens group G2R-2 is sequentially reflected by the free-form surface mirror 4A-2 and the free-form surface mirror 4B-2. Although not shown, for example, through the dust-proof glass 5-2 disposed on the enlargement side from the system 4-2, the light is emitted to the right side (enlargement side) of FIG. Are projected onto a screen arranged along the screen, and the image on the display panel 1-2 is enlarged and projected.
Here, the horizontal size, vertical size, pixel size, and distance from the optical axis to the lower side of the display panel 1-2 in Example 2 are as shown in Table 13 below.

In Table 13, the display panel 1-2 is assumed to be a digital micromirror device whose diagonal is 0.65 inches. However, the size and type of the display panel 1-2 are not limited to this. For example, the size of the display panel 1-2 may be set to a diagonal size of 0.55 inches. A transmissive or reflective liquid crystal panel may be used.
Further, the distance from the optical axis to the lower side of the display panel 1-2 is 1.402 mm apart in Table 13, but this distance can also be arbitrarily changed.
The position of the surface vertex of the free-form surface mirror 4A-2 of the reflective optical system 4-2 is the intersection of the optical axis and the plane including the display panel 1-2 in the ZY cross section shown in FIG. = (0,0), the position is fixed at (Z, Y) = (186.223, −9.352).
The position of the surface vertex of the other free-form surface mirror 4B-2 is the intersection of the plane including the display panel 1-1 and the optical axis in the ZY cross section shown in FIG. 10 (Z, Y) = (0, 0 ), The position is fixed at (Z, Y) = (198.288, 74.717).
A surface comprising a polynomial free-form surface is defined by the above equation (5) using a local orthogonal coordinate system (X, Y, Z) with the surface vertex as the origin, and the shape is given by giving a polynomial free-form surface coefficient C _j Identify.
In the reflective optical system 4-2, the free-form surface coefficient (C _j ) of the polynomial free-form surface of the 30th surface which is the reflection surface of the free-form surface mirror 4 _</ b> A- 2 is as shown in Table 14 (a) below. The free-form surface coefficients (C _j ) of the polynomial free-form surface of the 31st surface, which is the reflection surface of the free-form surface mirror 4B-2, are as shown in Table 14 (b) below.

On the enlargement side of the free-form curved mirror 4B-2, a dustproof glass 5-2 that is entirely formed with a constant thickness (3.0 mm) is disposed.
Since the dust-proof glass 5-2 has no optical power, even if there is a slight error in the mounting position of the dust-proof glass 5-2, the image quality of the image is less affected. And although illustration was abbreviate | omitted in the expansion side (FIG. 10 right side) of this dust-proof glass 5-2, arrangement | positioning of the projection surface of a screen is planned substantially parallel to an optical axis (Z direction).
In the projection optical system 100-2 according to Example 2 configured as described above, the light beam emitted from the display panel 1-2 is incident on the first lens group G1-2 of the refractive optical system 2-2, and After sequentially passing through the first lens group G1-2 and the second lens group G2-2, it is folded back by the free-form surface mirror 4A-2, and then reflected by the free-form surface mirror 4B-2, through the dust-proof glass 5-2. Projected onto a screen (not shown).
During focusing, the first lens group G1-2 does not move. For example, when focusing from the long distance side to the short distance side, the front side second lens group G2F-2 of the second lens group G2-2. Moves in a direction away from the display panel 1-2, and the rear second lens group G2R-2 moves in a direction away from the display panel 1-2 with a different movement amount from the front second lens group G2F-2. To do.

Specifically, when the front second lens group G2F-2 and the rear second lens group G2R-2 are moved to the short distance side through the reference from the long distance side, the variable lens group interval is It is as shown in Table 15.
That is, the lens distance d18 between the ninth lens L9 and the tenth lens L10, the distance d24 between the twelfth lens L12 and the thirteenth lens L13, the distance d28 between the fourteenth lens L14 and the dummy surface 29th surface, and the 35th surface. The distance d35 between the image plane and the image plane changes as shown in Table 15 as the distance d35 moves from the long distance side to the reference to the short distance side.

  Table 16 shows specific examples of the Y, Z, and α eccentricities of the 29th to 34th surfaces.

Next, the projection optical system 100-2 according to Example 2 shown in FIG. 10 has the RMS spot diameter when the temperature environment is as designed and when a temperature increase of 40 ° C. occurs with respect to this temperature environment. The change will be described with reference to FIG. 11, FIG. 12, FIG. 13, FIG. 14, FIG. 15 and Table 17, Table 18, Table 19, and Table 20.
As shown in FIG. 11, 25 sections were set and arranged in the image forming area of the display panel 1-2.
First, the specific data of the lens of the projection optical system 100-2 according to Example 2 shown in FIG. 10 is as shown in Table 11, but the projection optical system 100-2 has a temperature rise of 40 ° C. The specific data of this lens varies as shown in Table 17 below.

  The surface distances d18, d24, d28, and d35 in the front lens group G2F-2, the rear lens group G2R-2, the reflective optical system 4-2, and the like having the focus function at that time change as shown in Table 18 below. .

Further, in comparison with the RMS spot diameter, the RMS spot diameter of the projection optical system 100-2 based on the lens data according to the design values shown in Table 11 of Example 2 is as shown in FIG.
12A shows a case where the distance to the screen is a long distance (80 inches), FIG. 12B shows a case where the reference distance is 60 inches, and FIG. 12C shows a case where the distance is 48 inches. 6 shows changes in the RMS spot diameter (unit: mm) at each angle of view, and it can be seen that the spot diameter is sufficiently small and almost no field curvature occurs.
On the other hand, when the temperature of the projection optical system 100-2 based on the lens data of Example 2 is increased by 40 ° C., the lens data changes as shown in Table 17, and the RMS spot diameter is as shown in FIG. As shown in FIG. 13, although the back focus shift is eliminated separately, the spot diameter away from the optical axis with respect to the angle of view near the optical axis is remarkably large.
A direction in which the seventh lens L7, the eighth lens L8, and the ninth lens L9 as correction lenses CL for correcting the curvature of field are moved 0.6 mm away from the display panel 1-1 with respect to the projection optical system 100-2 in this state. Specific lens data when moved in the (magnifying side direction) is as shown in Table 19 below.

  In this way, when the correction lens CL-2 (seventh lens L7 to ninth lens L9) is moved from the display panel 1-2 to the 0.6 mm enlargement side, the thirteenth surface and the seventh lens of the sixth lens L6. The distance d13 between the fourteenth surfaces of L17 and the distance d18 between the eighteenth surface of the ninth lens L9 and the nineteenth surface of the tenth lens L10 vary as shown in Table 20, respectively. Note that the interval d24 and the intervals d28 and d35 do not change.

As shown in the lens data in Table 19, the lens data obtained by moving the correction lens CL-2 (seventh lens L7 to ninth lens L9) by a predetermined amount (in this example, 0.6 mm) is shown in FIG. As shown in a), (b), and (c), the size of the spot diameter at the field angle away from the optical axis is effectively suppressed, and the spot diameter is about the same as the field angle near the optical axis. Is obtained. The spot diameter is calculated for a long distance (80 inches), a reference (60 inches), and a short distance (48 inches). One pixel on the screen is 1.33 mm at 80 inches, 1 mm at 60 inches, 48 It is 0.8 mm in inches.
If the spot diameter is about one pixel, it can be determined that a good resolution is obtained.
That is, by moving the correction lens CL-2, it is possible to adjust the curvature of field satisfactorily and to suppress resolution deterioration in the peripheral portion of the screen.
Table 17 is a specific example of lens data when the temperature is increased by 40 ° C. with respect to the lens data of Example 2 shown in Table 11. The focus lens group (second lens group G2- As described above, the specific example of the change in the lens interval of 2) is as described above. Here, the back focus shift due to the temperature rise is caused by any of the methods of the prior art such as the above-described Patent Documents 1 to 3. It is assumed that the problem has been resolved.

In the calculation of lens data shown in Table 17, it is assumed that the radius of curvature, the surface interval, and the refractive index change under the following conditions 1) to 4) when the temperature rises.
1) Curvature radius: varies with linear expansion coefficient α.
2) Lens thickness: varies with linear expansion coefficient α.
3) Distance between lenses: (design value interval) + (change in linear expansion coefficient α of holding member) − (change in lens wall thickness at linear expansion coefficient α)
However, it was assumed that the holding member was made of an aluminum (linear expansion coefficient α: 283 × 10 −7 / ° C.) material.
The holding member may be made of a material other than aluminum, such as magnesium alloy (linear expansion coefficient α: 260 × 10 ⁻⁷ / ° C.) or plastic (linear expansion coefficient α: 600 × 10 −7 / ° C.). Also good.
4) Refractive index: Varies with the relative refractive index temperature coefficient β.
In Example 1 and Example 2 described above, φ1 / φ2 of conditional expression (1), f1 / f2 of conditional expression (2), and Δd / M of conditional expression (3) are as shown in Table 21 below. Thus, conditional expressions (1) to (3) are satisfied.

  Note that the present invention is not limited to the above-described and illustrated embodiments or examples, and various modifications can be made without departing from the scope of the invention.

  For example, the correction lens group CL has been described with an example in which the first embodiment includes one lens and the second embodiment includes three lenses. However, when the temperature changes, the first lens group of the fixed lens group is described. Since one or more lenses adjacent to the inner moving group may be moved in the direction of the optical axis, for example, two or four lenses may be used.

  In addition, since the present invention is characterized by a refractive optical system, the configuration of the reflective optical system is not limited. For example, the reflective optical system may be composed of one sheet.

  Further, the correction lens group of the present invention is required to be arranged on the enlargement side with respect to the stop included in the first lens group. However, any lens on the enlargement side with respect to the stop in the first lens group may be used. Absent.

  Incidentally, FIG. 15 is a graph in which the spot diameter is plotted when the sixth lens L6 is moved instead of the ninth lens L9 in the first embodiment.

  As can be seen from FIG. 15, when the sixth lens L6 is moved, a back focus shift occurs, and the resolution deteriorates over the entire screen.

  Therefore, the correction lens group may not be any lens on the enlargement side of the stop, and it is desirable to move the lens having a large field curvature adjustment effect described in the present invention without deteriorating other aberrations. .

G1, G1-1, G1-2 First lens group G2, G2-1, G2-2 Second lens group G2F, G2F-1, G2F-2 Front second lens group G2R, G2R-1, G2R-2 Rear Second lens group CL, L9, L7 to L9 Correction lens 1,1-1,1-2 Display panel 2,2-1,2-2 Refractive optical system 3,3-1,3-2 Aperture 4,4 -1,4-2,4A, 4B Reflective optical system 4A-1, 4A-2 Free curved surface mirror 4B-1, 4B-2 Free curved surface mirror 5,5-1, 5-2 Dust-proof glass 100, 100-1, 100-2 Projection Optical System 101 Illumination Unit 102 Various Circuit Units 200 Image Display Device

JP 2010-256394 A JP 2004-264570 A JP 2008-026864 A

Claims (9)

In a projection optical system that enlarges and projects an image formed on a display panel onto a screen via a refractive optical system,
The refractive optical system includes a first lens group that is fixed at the time of focusing and one or more second lens groups that are moved at the time of focusing on an optical path from the reduction side to the magnification side.
In the first lens group, a diaphragm is disposed, and a correction lens group is disposed on the enlargement side from the diaphragm,
The light flux that passes from the entrance surface to the exit surface of the correction lens group is φ1 that is the thinnest light flux between the entrance surface and the exit surface, and the thickness of the light beam that passes through the stop is φ2. When
The aperture is defined by the following conditional expression (1):
(1) 1.0 <φ1 / φ2 <1.8
The projection optical system is arranged so as to satisfy the above.   The projection optical system according to claim 1, wherein the stop is arranged at a position where the reduction side of the refractive optical system is non-telecentric.   2. The projection optical system according to claim 1, wherein the correction lens group moves along the optical axis direction so that the focal length of the entire refractive optical system increases as the temperature rises.   When the temperature of the refractive optical system rises, the correction lens group is configured to move in a direction away from the display panel so that the curvature of field caused by the temperature rise can be adjusted. The projection optical system according to claim 1, wherein the projection optical system is a projection optical system. When the focal length of the correction lens group (the combined focal length in the case of two or more lenses) is f1, and the combined focal length of the refractive optical system is f2,
The following conditional expression (2):
(2) 1.6 <f1 / f2 <2.0
The projection optical system according to claim 1, wherein: When the maximum movement amount that can move the correction lens group in the optical axis direction is Δd, and the paraxial lateral magnification of the refractive optical system is M,
The following conditional expression (3):
(3) 0.06 <Δd / M <0.09
The projection optical system according to claim 1, wherein the projection optical system according to claim 1 is satisfied.   The projection optical system according to claim 1, wherein all of the correction lenses are spherical lenses.   An image display apparatus comprising the projection optical system according to claim 1. In an adjustment method of an image display device provided with a projection optical system that enlarges and projects an image formed on a display panel onto a screen via a refractive optical system,
The refractive optical system includes a first lens group that is fixed at the time of focusing and one or more second lens groups that are moved at the time of focusing on an optical path from the reduction side to the magnification side.
In the first lens group, a diaphragm is disposed, and a correction lens group is disposed on the enlargement side from the diaphragm,
A method of adjusting an image display apparatus, comprising: adjusting curvature of field caused by a change in temperature by moving the correction lens group in an optical axis direction.

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