JP2018132565A - Projection optical system and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a new projection optical system that includes a dioptric system and a reflection optical system having a refractive power, and considers the influence of heat.SOLUTION: The projection optical system is a projection optical system that enlarges and projects, on a projection target surface SC, an image displayed on an image forming part V of an image display element, and comprises a dioptric system 11 including a plurality of lens groups and a reflection optical system 12. The reflection optical system includes at least one reflection optical element 12 having a refractive power; the dioptric system 11 includes one or more positive lenses P1 of one type and one or more positive lenses P2 of the other type; the positive lenses P1 are formed of a lens material satisfying the conditions (1) and (2); and the positive lenses P2 are formed of a lens material satisfying the conditions (3) and (4).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a projection optical system and an image display device.

Various types of image display devices (hereinafter also referred to as “projectors”) that display an image displayed on the projection surface by enlarging an image displayed on the image forming unit of the image display element have been known. Yes. As the image display element, various so-called “light valves” such as DMD (digital mirror device) and liquid crystal panel are known. The image forming unit is a “portion on which an enlarged image is displayed” in the light valve.
An image that is enlarged and projected on the projection surface is also referred to as a “projected image or enlarged image” below.
The projection optical system is an optical system that enlarges and forms an image displayed on the image forming unit on the projection surface, and various types have been proposed. The projected surface is generally a “screen surface”.
As a configuration of the projection optical system, one that realizes a short projection distance by combining a refractive optical system and a “reflective optical system having refractive power” is known (Patent Documents 1 to 3, etc.). The “refractive optical system” is an optical system configured by a combination of a plurality of lenses. The projection distance can be shortened by reflecting the imaging light beam that has passed through the refractive optical system toward the projection surface by a reflective optical system having refractive power.
Recently, there is a strong demand for “brightness of the enlarged image” that is enlarged and projected onto the projection surface. However, if a bright enlarged image is to be realized, heat generation will inevitably increase in the light source and drive power source, and projection optics will increase. The influence of heat on the system is unavoidable. When the temperature of the projection optical system rises due to heat, the field curvature and chromatic aberration are easily affected, and the resolution is also affected and the resolution is easily lowered.

  An object of the present invention is to realize a novel projection optical system that has a refractive optical system and a reflective optical system having a refractive power, and that takes into consideration the influence of heat.

A projection optical system according to the present invention is a projection optical system that enlarges and projects an image displayed on an image forming unit of an image display element on a projection surface, and includes a refractive optical system having a plurality of lens groups, and a reflective optical system The reflective optical system has at least one reflective optical element having refractive power, and the refractive optical system has at least one of two types of positive lenses P1 and P2, and the positive lens P1 is a temperature coefficient of relative refractive index at the D-line in the range of 20 ° C. to 40 ° C .: dndTP1, Abbe number: vdP1.
(1) 2 <dndTP1
(2) 60 <vdP1
The positive lens P2 is formed of a lens material satisfying
Abbe number: vdP2 is the condition:
(3) 50 <vdP2
And the refractive indices for g-line, F-line, d-line, and C-line are ng, nF, nd, and nC, respectively.
θgF2 = (ng−nF) / (nF−nC)
ΘgF2 defined by the above and the Abbe number: vdP2
ΔθgF2 = θgF2 − (− 0.001618 × vdP2 + 0.6415)
ΔθgF2 defined by the condition:
(4) 0.004 <ΔθgF2
It is formed with the lens material which satisfies these.

  According to the present invention, it is possible to realize a novel projection optical system that has a refractive optical system and a reflective optical system having refractive power, and that takes into consideration the influence of heat.

It is a figure which shows one Embodiment of an image display apparatus explanatoryly. FIG. 3 is a diagram illustrating an example of an image forming unit in an image display device. It is a figure for demonstrating the position of the angle of view (F1-F13) in the image formation part area | region in a to-be-projected surface (screen). It is a figure explaining the refractive optical system of the projection optical system used for the image display apparatus shown in FIG. FIG. 3 is a diagram illustrating a spot diagram of each angle of view at a long distance of the projection optical system of Example 1. FIG. 6 is a diagram showing spot diagrams of respective angles of view at a reference distance of the projection optical system of Example 1. FIG. 3 is a diagram illustrating a spot diagram of each angle of view at a short distance of the projection optical system of Example 1. It is a figure which shows the spot diagram of each view angle in the long distance at the time of the temperature rising of the projection optical system of Example 1. FIG. It is a figure which shows explanatoryally another form of implementation of an image display apparatus. It is a figure for demonstrating the refractive optical system of the projection optical system used for the image display apparatus shown in FIG. FIG. 6 is a diagram showing a spot diagram of each angle of view at a long distance of the projection optical system of Example 2. FIG. 6 is a diagram illustrating a spot diagram of each angle of view at a reference distance of the projection optical system of Example 2. FIG. 6 is a diagram showing spot diagrams of respective angles of view at a short distance of the projection optical system of Example 2. It is a figure which shows the spot diagram of each angle of view in the long distance at the time of temperature rising of the projection optical system of Example 2. FIG. It is a figure which shows other another form of implementation of an image display apparatus explanatoryly. It is a figure for demonstrating the refractive optical system of the projection optical system used for the image display apparatus shown in FIG. It is a figure which shows the spot diagram of each view angle in the long distance of the projection optical system of Example 3. FIG. It is a figure which shows the spot diagram of each angle of view in the reference distance of the projection optical system of Example 3. FIG. It is a figure which shows the spot diagram of each angle of view in the short distance of the projection optical system of Example 3. FIG. It is a figure which shows the spot diagram of each view angle in the long distance at the time of the temperature rising of the projection optical system of Example 3. FIG.

Prior to describing specific embodiments, a projection optical system and an image display apparatus of the present invention will be described.
As described above, the projection optical system of the present invention includes a refractive optical system and a reflective optical system, the refractive optical system includes a plurality of lens groups, and the reflective optical system includes a “reflective optical element having refractive power”. Have at least one.
Of the lenses constituting the “refractive optical system having a plurality of lens groups”, at least one of two types of positive lenses P1 and P2 is included. That is, one or both of the positive lens P1 and the positive lens P2 may be included.
The positive lens P1 is formed of a lens material that satisfies the following conditions (1) and (2).
(1) 2 <dndTP1
(2) 60 <vdP1
“DndTP1” in condition (1) is “temperature coefficient of relative refractive index at D line (wavelength 589.29 nm)” in the range of 20 ° C. to 40 ° C., and “vdP1” in condition (2) is Abbe number It is.

The positive lens P2 is formed of a lens material that satisfies the following conditions (3) and (4).
(3) 50 <vdP2
(4) 0.004 <ΔθgF2
“VdP2” in the condition (3) is an Abbe number.
“ΔθgF2” in the condition (4) is defined by the following equation (A).

(A) ΔθgF2 = θgF2 − (− 0.001618 × vdP2 + 0.6415)
“VdP2” in the formula (A) is the Abbe number of the lens material of the positive lens P2 as described above. “ΘgF2” is the “partial dispersion ratio” of the lens material of the positive lens P2, and the refractive index of the lens material at the g-line (wavelength 435.83 nm): Ng, F-line (wavelength 486.13 nm). Is defined by the following formula (B) by refractive index: NF, refractive index at d line (wavelength: 587.56 nm): Nd, refractive index at C line (wavelength: 656.27 nm): NC.
θgF2 = (ng−nF) / (nF−nC)
Parameter (4) parameter: ΔθgF is well known as “an anomaly dispersion equation”, the vertical axis is the partial dispersion ratio: θgF, the horizontal axis is Abbe number: vd, and OHARA's NSL7 (511605) Represents the difference between the equation of a straight line connecting PBM2 and PBM2 (620363) and θgF of each glass type.

The lens material satisfying the conditions (3) and (4) is “a glass material with high anomalous dispersion”, and “uses one or more positive lenses P2 formed of such a material in the refractive optical system”. Therefore, advanced chromatic aberration correction can be performed, and a “high-definition color projection image” can be obtained using an “image display element capable of displaying a high-definition image”.
However, a lens material that satisfies the conditions (3) and (4) generally has “a large value with a negative refractive index temperature coefficient value”. For this reason, the “negative change in refractive power” due to temperature change increases. For this reason, the positive refractive power of the positive lens P2 changes in a direction that is weakened by the influence of the temperature increase of the projection optical system.
When the positive lens P1 that satisfies the conditions (1) and (2) satisfies the condition (1), the positive refractive power changes in a direction in which the positive refractive power increases as the temperature rises.
Therefore, the resolution performance of the projection optical system can be reduced by “cancelling the decreasing tendency of the positive refractive power in the positive lens P2 by the increasing tendency of the positive refractive power in the positive lens P1” due to the temperature rise of the projection optical system. It is possible to “maintain well” regardless of the temperature change of the projection optical system.

More preferably, the parameters of the conditions (1) to (4) satisfy the following conditions (1A) to (4A).
(1A) 3 <dndTP1
(2A) 62 <vdP1
(3A) 72 <vdP2
(4A) 0.0048 <ΔθgF2
More preferably, each parameter of the conditions (2) and (4) satisfies the following conditions (2B) and (4B).
(2B) 62 <vdP1 <70
(4B) 0.007 <ΔθgF2.

It is preferable that the two types of positive lens P1 and positive lens P2 further satisfy the following condition (5).
(5) 0.1 <FP2 / FP1 <2
In condition (5), “FP1” is the focal length of the positive lens P1 at the d-line, and “FP2” is the focal length of the positive lens P2 at the d-line.
Condition (5) regulates a preferable range of the ratio of the refractive powers (both positive) of the positive lens P1 and the positive lens P2.
Imaging of a projected image by a projection optical system with a short projection distance requires a high degree of temperature correction when attempting to form a high-definition projected image with a narrow depth of focus on the projection surface and high resolution.
If the lower limit value of the condition (5) is not reached, the refractive power of the positive lens P1 becomes relatively smaller than the refractive power of the positive lens P2, and the decrease of the refractive power of the positive lens P2 due to the temperature rise is reduced. It tends to be difficult to compensate with an increase in the refractive power of P1. On the contrary, when the upper limit of the condition (5) is exceeded, the refractive power of the positive lens P2 becomes relatively small with respect to the refractive power of the positive lens P1, and the refractive power of the positive lens P2 decreases with increasing temperature. As a result, the refractive power of the positive lens P1 is excessively increased, so that proper temperature correction tends to be difficult, and resolution performance is likely to deteriorate.

The parameter of the condition (5) is more preferably the following condition:
(5A) 0.1 <FP2 / FP1 <2
Is preferably satisfied.

  As described above, one or more positive lenses P1 can be used. However, if the positive lens P1 made of a lens material that satisfies the conditions (1) and (2) is formed as a “spherical lens” that can be realized at low cost, projection is possible. This is effective in reducing the cost of the optical system, and even if two or more positive lenses P1 are used, an increase in the cost of the projection optical system can be suppressed.

The positive lens P2 has a condition that the temperature coefficient of relative refractive index with respect to the D line in the temperature range of 20 ° C. to 40 ° C .: dndTP2
(6) 0> dndTP2
Is preferably satisfied.
By using the positive lens P2 that satisfies the condition (6) together with the positive lens P1 that satisfies the condition (1), even in an “ultra-short projection projector” having an extremely short projection distance, the amount of movement of the image plane due to the temperature change is reduced. it can.
The parameter of the condition (6) is more preferably the following condition:
(6A) -3> dndTP2
Is preferably satisfied.

The refractive optical system has “a plurality of lens groups” as described above, and the positive lens P1 and the positive lens P2 can basically be appropriately arranged in the plurality of lens groups.
When the projection optical system is affected by heat from a heat source such as a light source, the temperature relationship is not uniform in the refractive optical system due to the positional relationship between the heat source and the refractive optical system, and a temperature gradient is generated in the lens group arrangement direction. Likely to happen. In view of this point, it is preferable that the positive lens P1 and the positive lens P2 are included in “the same lens group”. When the positive lens P1 and the positive lens P2 are included in the same lens group, the distance between the positive lenses is reduced, the temperature difference between the lenses due to the temperature gradient is reduced, and the performance deterioration due to the temperature change is efficiently compensated. It can be carried out.
Here, the “lens group” refers to a plurality of lenses held by one lens holding member.

The positive lens P1 and the positive lens P2 are preferably included in a lens group including an aperture stop. When the positive lens P1 included in the lens group including the aperture stop satisfies the condition (2) and the positive lens P2 satisfies the conditions (3) and (4), chromatic aberration, particularly “axial chromatic aberration” is obtained. It can be highly corrected.
On the other hand, in the vicinity of the aperture stop, the temperature is likely to rise and the temperature is likely to increase due to “the light beam being narrowed”. When the positive lens P1 arranged at such a position satisfies the condition (1), the image plane movement due to the temperature change of the projection optical system can be highly corrected.

  The “aperture stop position” refers to a “position where the thickness of a bundle of rays (total light flux) from the entire area of the image display element is the smallest” that passes through the refractive optical system.

  The positive lens P1 is also preferably arranged on the “reduction side with respect to the aperture stop”. The temperature tends to be particularly high on the reduction side of the aperture stop, and by arranging the positive lens P1 on the “reduction side of the aperture stop”, it is possible to perform good temperature compensation.

  Both the positive lens P1 and the positive lens P2 are preferably included in the “lens group on the most reduction side”. The lens group on the most reduction side tends to be close to a heat source such as an illumination optical system, and particularly tends to be at a high temperature. By disposing the positive lens P1 and the positive lens P2 in the lens group on the most reduction side, performance compensation with respect to a temperature change becomes easy.

  Further, when there are a plurality of “moving lens groups” that move in accordance with focusing and the positive lens P1 and the positive lens P2 are provided in the moving lens group, the positive lens P1 and the positive lens P2 are “the same moving lens group”. Is preferably included. This is because even if the lens group is displaced due to focusing, the relative positional relationship between the positive lens P1 and the positive lens P2 can be kept unchanged, so that correction according to temperature change is facilitated.

  More preferably, the positive lens P1 and the positive lens P2 are preferably arranged in a “lens group that does not move during focusing”. Temperature correction can be performed without taking into account the displacement accompanying the focusing and the change in the positional relationship.

  The positive lens P1 and the positive lens P2 are preferably “held by a metal holding member”. If the holding member that holds the positive lens P1 and the positive lens P2 is made of metal, the temperature difference between the positive lens P1 and the positive lens P2 can be quickly reduced due to the high thermal conductivity of the metal, and the temperature changes. It becomes easy to correct the optical characteristics.

  A “concave mirror” can be suitably used as the “reflecting optical element having refractive power” of the reflecting optical system that constitutes the projection optical system together with the refractive optical system. The number of reflective optical elements is not limited to one, and a plurality of reflective optical elements can be used. Further, a “plane mirror that bends the optical path” can be appropriately arranged in the projection optical system. When a concave mirror is used as the reflective optical element, it is easy to realize a good projection image by combining the refractive power of the concave mirror with the imaging function of the refractive optical system.

  In this case, the refracting optical system forms an “intermediate image conjugate with the image displayed on the image forming unit” between the refracting optical system and the concave mirror, and the intermediate image is enlarged by the concave mirror to be projected. An image can be formed as an enlarged image on the surface.

Various configurations are possible for the plurality of lens groups constituting the refractive optical system.
For example, the refractive optical system can be “configured by sequentially arranging the first to sixth lens groups from the reduction side to the enlargement side”, and “from the first to the sixth side sequentially from the reduction side to the enlargement side”. The fourth lens group may be arranged ”. Of course, the lens group configuration of the refractive optical system is not limited to these examples.

An image display apparatus (projector) according to the present invention is an image display apparatus that displays an image by enlarging and projecting an image displayed on an image forming unit of an image display element on a projection surface by a projection optical system. The projection optical system used is used.
When the projection optical system used in the image display apparatus uses a single concave mirror as the “reflecting optical element having refractive power”, the conditions are:
(7) TR <0.35
Is preferably satisfied.
The parameter “TR” in the condition (7) is from the “intersection P where the distance to the projection surface is maximum in the direction perpendicular to the projection surface” among the intersection points of the concave mirror and the imaging light ray to the projection surface. The ratio of the “distance in the direction perpendicular to the projection surface: PL” to the horizontal width of the maximum image projected on the projection surface: W: PL / W.
The “maximum image projected on the projection surface” is the maximum of the projection image projected on the projection surface, and is a projection image when the projection distance is “far”.
The larger the width of the maximum image: W, the larger the “projected image size”, and the shorter the distance: PL, the smaller the distance between the concave mirror and the projection surface (hereinafter also referred to as “projection distance”). . By satisfying the condition (7), a large projection image can be displayed with a short projection distance.

The parameter TR is more preferably the following condition:
(7A) TR <0.30
Good to be satisfied.
The image display device also has the following conditions:
(8) BF / Y <3.5
It is good to satisfy.
“BF” in the parameter of the condition (8) is between the intersection of the optical axis of the refractive optical system and the image forming unit in the projection optical system and the image forming unit of the “lens closest to the image forming unit” of the refractive optical system. On the optical axis.
That is, “BF” is “back focus” on the reduction side of the refractive optical system.
“Y” is the maximum value of the distance between the optical axis of the refractive optical system and the image forming unit.
Supplementally, the refractive optical system has a plurality of optical axis symmetric lenses. When a plurality of these optical axis symmetric lenses share a common optical axis, the shared optical axis is referred to as an “optical axis of a refractive optical system”. Among the plurality of lenses constituting the refractive optical system, there may be one or more “lenses that do not share the optical axis” with other lenses. In such a case, the optical axis shared by the “lens sharing the optical axis” other than such a lens is defined as the “optical axis of the refractive optical system”.
By satisfying the condition (8), the back focus (BF) can be shortened, so that the projection optical system can be “downsized”. When the back focus is shortened, the “most reduction lens group” close to a heat source such as an illumination light source easily rises in temperature, and the image plane easily moves due to a temperature change. However, by using the positive lens P1 and the positive lens P2, Thus, it is possible to suppress image plane movement due to temperature changes.

In addition, the above “Y” is the condition: together with “pixel pitch: PT” of the image display element.
(9) PT / Y <0.001
Is preferably satisfied.
An image display element that satisfies the condition (9) is “pixel pitch: PT is small”, and therefore, a high-definition image can be displayed. When the pixel pitch is small, the depth of focus on the projection surface is also small, and the displacement of the image plane due to the temperature change becomes sensitive to the temperature change. However, as described above, the positive lens P1 and the positive lens P2 are favorable. Can be realized.
The image display device also has the following conditions:
(10) 10 <PLQ / Y <30
Is preferably satisfied.
“PLQ” in the parameter of the condition (10) indicates that “the distance from the image forming unit is the maximum in the direction orthogonal to the image forming unit among the intersections of the optical element on the enlargement side with respect to the refractive optical system and the imaging light beam. Is the distance in the “direction perpendicular to the image forming unit” between the intersection point Q and the image forming unit, and “Y” is the distance between the optical axis of the refractive optical system and the image forming unit as described above. It is the maximum value.
Condition (10) defines a preferable size range of the entire projection optical system.
If the upper limit is exceeded, the “size of the refractive optical system in the direction of the optical axis” of the projection optical system increases, leading to an increase in the size of the image display device. If the lower limit of the condition (10) is not reached, the size of the projection optical system is reduced, which is advantageous for making the image display device compact. However, it is necessary to increase the refractive power of the lens group constituting the refractive optical system, Manufacturing sensitivity error tends to be high.
The parameter of the condition (10) is more preferably the following condition:
(10A) 10 <PLQ / Y <30
Is preferably satisfied.

Hereinafter, three examples of embodiments of the image display device and the projection optical system will be described.
FIG. 1, FIG. 9, and FIG. 15 each illustrate an embodiment of an image display device. The projection optical system used in these embodiments corresponds to specific Examples 1 to 3 of the projection optical system to be described later in the order shown.
In order to avoid complications, in FIGS. 1, 9, and 15, the same reference numerals are used for those that are not likely to be confused.
In these drawings, symbol H indicates “image display device”. Reference numeral LV denotes an “image forming unit” of the image display element, reference numeral LS denotes an “illumination optical system”, reference numeral F denotes a “transparent parallel plate”, reference numeral Pr denotes a “prism”, and reference numeral SC denotes a “projection surface”. It shows the screen that forms the entity. The transparent parallel flat plate F is assumed to be a cover glass (seal glass) of the image forming unit LV.
1, reference numeral 21 in FIG. 9, and reference numeral 31 in FIG. 15 indicate “refractive optical systems”, respectively. Reference numeral 12 in FIG. 1, reference numeral 22 in FIG. 9, and reference numerals 32 and 33 in FIG. Reflective optical system ".
In the embodiment shown in FIGS. 1 and 9, the reflecting optical system is composed of a single concave mirror 12, 22, and in the embodiment shown in FIG. 15, the reflecting optical system is a flat mirror 32 and a concave surface. A mirror 33 is used.

  Further, reference numeral 13 in FIG. 1, reference numeral 23 in FIG. 9, and reference numeral 34 in FIG. 15 indicate “dust-proof glass”.

  1, 9, and 15 indicates an “aperture stop” disposed in the refractive optical system.

  Three orthogonal axes X, Y, and Z are set as shown in FIGS. The X direction is a direction “perpendicular to the drawing”, the Y direction is a direction “parallel to the vertical direction of the drawing”, and the Z direction is a direction “parallel to the horizontal direction of the drawing”.

  As shown in these drawings, the Z direction is a direction orthogonal to the screen SC and the image forming unit LV, and the screen SC and the image forming unit LV are parallel to the XY plane.

Also, in these figures, “point P” means “projected surface SC among the intersections of concave mirrors 12, 22, and 33 and the imaging light beam described above in relation to the parameter of condition (7). An intersection P where the distance to the projection surface SC is the maximum in the vertical direction is the “projection distance”, and the distance in the direction parallel to the Z direction between the intersection P and the screen SC is the condition (7 The distance described in relation to the parameter “TR” in FIG.
In FIG. 1, FIG. 9, and FIG. 15, “point Q” is larger than the refractive optical systems 11, 21, and 31 described above in relation to “PLQ” in the parameter of condition (10). Among the intersections between the optical element on the side and the imaging light beam, the “intersection Q at which the distance from the image forming unit LV is maximum” in the direction orthogonal to the image forming unit LV (Z direction).

“Point Q” corresponds to “point P” described above in the embodiment of FIGS. In the embodiment shown in FIG. 15, the point Q is “the intersection where the imaging light ray intersects with the dust-proof glass 34 and has the maximum distance in the Z direction from the image forming unit LV” in the dust-proof glass 34. .
That is, in the embodiment of FIGS. 1 and 9, the “optical elements on the enlargement side relative to the refractive optical system” that define the point Q are the concave mirrors 12 and 22, but in the embodiment shown in FIG. The “optical element on the enlargement side with respect to the refractive optical system” that defines the point Q is the “dust-proof glass 34”.

As the image display element, light valves such as “DMD”, “transmission type liquid crystal panel”, and “reflection type liquid crystal panel” can be used as appropriate, and an image is displayed on the image forming unit LV.
The illumination optical system LS is for illuminating an image formed on the image forming unit LV when the image display element does not have a function of emitting light, and the image display element is a “two-dimensional array of light emitting elements”. Thus, it is not necessary to use the “self-emission method having a function of emitting the generated image” as in FIG.

  In the embodiment described below, “DMD” is assumed as an image display element, and an image formed by the inclination of individual micromirrors in a two-dimensional micromirror array in DMD is illuminated from illumination optical system LS. Illuminate with light. The illumination optical system LS preferably has a function of efficiently illuminating the image forming unit LV. For example, a rod integrator or a fly eye integrator can be used to make the illumination more uniform.

  As a light source for illumination, a white light source such as an ultra-high pressure mercury lamp, a xenon lamp, a halogen lamp, or an LED can be used, and a monochromatic light source such as a monochromatic light emitting LED or LD can also be used.

  The image display apparatus that will be described below is assumed to project a “color image” on the screen SC.

In the image display apparatus shown in FIGS. 1 and 9, three DMDs are used as image display elements, and a red component image, a green image component, and a blue image component of a color image are included in the image forming unit of these three DMDs. Formed and displayed, these color image components are illuminated with corresponding colored illumination light.
Each illumination light is modulated by each color image component, is “color synthesized” by the prism Pr, and enters the projection optical system as an imaging light beam.
In the image display device shown in FIG. 15, one DMD is used as an image display element, and a red component image, a green image component, and a blue image component of a color image are cyclically displayed on the image forming unit LV. Corresponding colors of illumination light are sequentially emitted in synchronization with the displayed color component images. Each illumination light is modulated by each color image component and enters the projection optical system as an imaging light beam.

  The imaging light beam passes through the refractive optical systems 11, 21, and 31, is reflected by the reflective optical systems 12, 22, and “32 and 34”, and is irradiated toward the screen SC through the dust-proof glasses 13, 23, and 34. The “color enlarged image” is formed on the screen SC. In the case of the image display device of FIG. 15, the enlarged image of the color is sequentially switched as the projected image of red, green, and blue, and is visually synthesized as a “color enlarged image”.

Here, the “image forming unit” in the image display element and the image display area of the screen that forms the substance of the projection surface will be described with reference to FIGS.
FIG. 2 shows the image forming unit LV of the image display element. In the figure, the X and Y directions are as described above, and the direction orthogonal to the drawing of FIG. 2 is the Z direction, which is parallel to the optical axis of the refractive optical system. As shown, the “optical axis” orthogonal to the drawing is the origin of the XY plane.
As shown in the figure, the image forming portion LV has a rectangular shape that is long in the X direction, and its center (image forming portion center) is shifted from the optical axis position in the positive direction in the Y direction (upward in the drawing) as shown. ing.
The maximum distance among the distances between the “optical axis” and the image forming unit LV in the drawing is “Y” in the conditions (9) and (10), and this distance “Y” is not related to the Y direction. .
FIG. 3 illustrates the “image forming area” on the screen in an explanatory manner. Since the image forming unit region is an enlargement of the image forming unit LV shown in FIG. 2, the image forming unit region has a similar shape to the image forming unit, but the size differs depending on the “magnification magnification by the projection optical system”.

  As shown in the figure, typical 13 points, F1 to F13, are defined in the image forming area, and these are called view angles F1 to F13.

"Example of projection optical system"
Hereinafter, specific examples of the projection optical system used in the image display apparatus shown in FIGS. 1, 9, and 15 will be described as Examples 1 to 3.
Each of the refractive optical systems 11, 21, and 31 used in the projection optical systems of Examples 1 to 3 is composed of a plurality of rotationally symmetric lenses, and all the lenses are “light” as shown in the figure. "Sharing axes".

  In Example 1 and Example 2, “one concave mirror” is used as the reflecting optical system, and “one plane mirror and one concave mirror” is used as the reflecting optical system in Example 3. .

FIG. 4 shows the configuration of the refractive optical system in Example 1 and the displacement of the lens group accompanying focusing from the long distance side to the short distance side.
FIG. 10 shows the configuration of the refractive optical system in Example 2 and the displacement of the lens unit accompanying focusing from the long distance side to the short distance side. FIG. 10 shows the configuration of the refractive optical system in Example 3 and the distance from the long distance side to the near side. FIG. 16 shows the displacement of the lens group accompanying focusing on the distance side.
In order to avoid complication, in FIG. 4, FIG. 10, and FIG. 16, the same symbols are used for those that are considered not to be confused. The left side of these figures is “reduction side”, and the right side is “enlargement side”
It is. Reference numeral LV represents the image forming unit as described above, and reference numeral BF represents BF (back focus of the refractive optical system) under the above condition (8).
The first lens group I to the sixth lens group VI are sequentially represented by reference numerals I to VI. In Example 1 and Example 2, the refractive optical system is configured by the first to sixth lens groups I to VI, and in Example 3, the refractive optical system is configured by the first to fourth lens groups I to IV. Yes.
The positive lens P1 is represented by the symbol P1, and the positive lens P2 is represented by the symbol P2.

In the following description regarding the examples, the meanings of the symbols are as follows.
f: Focal length of the entire system
NA: Numerical aperture
ω: Half angle of view (deg)
R: radius of curvature (for aspheric surfaces, the paraxial radius of curvature)
D: Surface spacing
Nd: Refractive index
νd: Abbe number
K: Aspherical conical constant
Ai: i-th aspherical constant
C: Paraxial curvature (reciprocal of paraxial radius of curvature)
Cj: free-form surface coefficient.

In Example 1 and Example 2, “aspherical surface” is used as the surface shape of the concave mirror forming the reflective optical system, and in Example 3, “free curved surface” is used as the surface shape of the concave mirror in the reflective optical system. It is used.
“Aspherical shape” is a paraxial curvature: C, height from axis: H, conic constant: K, aspheric coefficient of each order: Ai, and ξ as “aspheric amount in axial direction” Well-known formula:
ξ = CH ² / [1 + √ (1− (1 + K) C ² H ² )] + ΣAiH ⁱ
The shape is specified by giving C, K, and Ai.
“The shape of the free-form surface” is a well-known formula using paraxial curvature: C, height from the axis: H, conic constant: K, free-form surface coefficient: Cj, and η as the amount of free-form surface in the optical axis direction:
^{η = CH 2 / [1 +} √ (1- (1 + K) C 2 H 2)] + ΣCjx m y n
Is represented by
x and y represent the coordinate position of the coordinate system fixed on the concave mirror with “H = 0” as the “origin” on the free-form surface, and “j” in the free-form surface coefficient Cj is
j = [{(m + n) ² + m + 3n} / 2] +1
Defined by
The shape of the free-form surface is specified by giving the paraxial radius of curvature, the conic constant, and the free-form surface coefficient. In the following, regarding the quantity having the dimension of length, the unit is “mm” unless otherwise specified.
"Example 1"
As shown in FIG. 4, the refractive optical system in the projection optical system of Example 1 includes a first lens group I having a positive refractive power and a positive refractive power in order from the image forming unit LV side to the enlargement side. A second lens group II having positive refractive power, a third lens group III having positive refractive power, a fourth lens group IV having positive refractive power, a fifth lens group V having negative refractive power, and a negative A sixth lens unit VI having refractive power is included. A concave mirror 21 is arranged on the enlargement side of the refractive optical system as shown in FIG.
When focusing from the long distance side to the short distance side, the second lens group II, the fourth lens group IV, and the fifth lens group V move to the image forming unit LV side, and the third lens group III moves to the enlargement side. To do. The first lens group I and the sixth lens group VI do not move during focusing.

  The first lens group I includes, in order from the reduction side, a biconvex lens, a double-sided aspherical biconvex lens, a “three-piece cemented lens in which a biconvex lens, a biconcave lens, and a positive meniscus lens are cemented”, a double-sided aspherical biconvex lens, A cemented lens in which a meniscus lens and a biconvex lens are cemented, an aperture stop, a cemented lens in which a negative meniscus lens and a biconvex lens having a stronger convex surface on the enlargement side are cemented, and a positive meniscus lens and a biconcave lens are cemented. "Joint lens" is arranged.

  The positive meniscus lens on the magnification side of the “three-piece cemented lens” in the first lens group I is the positive lens P1, and the biconvex lens in the cemented lens on the reduction side of the aperture stop is the positive lens P1.

  The second lens group II is composed of “a cemented lens in which a biconvex lens and a biconcave lens are cemented”, and the third lens group III is composed of “a biconvex lens and“ a cemented lens in which a positive meniscus lens and a negative meniscus lens are cemented ”. The fourth lens group IV includes one double-sided aspherical positive meniscus lens, the fifth lens group V includes a biconvex lens, a negative meniscus lens, and a double-sided aspherical biconcave lens, and the sixth lens group VI includes one sheet. It consists of a biconcave lens.

The data of Example 1 of the projection optical system is shown below.
Numerical aperture: 0.2273
The data of Example 1 is shown in Table 1. The “surface number” shown in the leftmost column is the surface number 1 for the image forming unit LV, and the surface numbers 2 to 5 are the surfaces of the transparent parallel flat plate F and the prism Pr. Surface number 6 is the lens surface on the most reduction side of the refractive optical system. This also applies to Example 2 below.

“Variable intervals with focusing”
Table 2 shows variable intervals associated with focusing at short distance, reference distance (reference and display), and long distance.

"Aspherical data"
An aspherical surface is a surface obtained by adding “*” to the surface number in the above data (this is the same in other examples below), and the data is shown in Table 3.

In the above notation, for example, “2.8853E-10” means “2.8853 × 10 ⁻¹⁰ ”. The same applies to the following.

"Parameter: TR value"
Table 4 shows the parameter TR with respect to the projection distance.

  In the first embodiment, the specification of the image forming unit LV is as follows.

Dot size: 5.4 μm
Lateral direction (X direction) length: 14.6664 mm
Longitudinal direction (Y direction) length: 8.2512 mm
Distance in the Y direction (shift amount) from the optical axis to the center of the image forming unit: 5.5256 mm.

Spot diagrams corresponding to the respective angles of view F1 to F13 shown in FIG. 3 are shown in FIGS. Each spot diagram shows imaging characteristics (mm) on the screen surface for wavelengths: 638 nm (red), 550 nm (green), and 455 nm (blue).
Each of the spot diagrams in FIGS. 5 to 7 is for a temperature of 20 ° C., and the spot diagram shown in FIG. 8 is for a screen size of 150 inches when the temperature is increased by 20 ° C. to 40 ° C. Is. It is clear that there is no difference from that when the temperature is 20 ° C. (FIG. 5), and the projection optical system of Example 1 is “good temperature correction”.

In Example 1, as a glass material satisfying the conditions (1) and (2) for the positive lens P1 arranged on the reduction side from the aperture stop, “OHARA L-BSL7 nd: 1.51633, vd: 64.06, dndT: 4.7, θgF: 0.5333), and the balance between the fluctuation of the focal length due to the temperature change and the expansion of the mechanical holding portion due to the heat is balanced.
Further, the positive lens P1 is a spherical lens to reduce the cost. Further, as a glass material satisfying the conditions (3) and (4) for the positive lens P2 arranged on the reduction side from the aperture stop, “OH-ARA S-FPL51 nd: 1.49700, vd: 81.54, dndT: −6 .2, θgF: 0.5375, ΔθgF: 0.028 ”is used to suppress the occurrence of chromatic aberration.

  Temperature compensation is performed by using a positive lens P2 made of a material having a negative and large refractive index temperature coefficient and a positive lens P1 made of a material having a positive and large refractive index temperature formation.

"Example 2"
As shown in FIG. 10, the refractive optical system in the projection optical system of Example 2 includes a first lens group I having a positive refractive power and a negative refractive power sequentially from the image forming unit LV side toward the enlargement side. A second lens group II having a positive refractive power, a third lens group III having a positive refractive power, a fourth lens group IV having a negative refractive power, a fifth lens group V having a negative refractive power, and a negative And a sixth lens group VI having refractive power. On the enlargement side of the refractive optical system, a concave mirror 22 is arranged as shown in FIG.
When focusing from the long distance side to the short distance side, the second lens group II, the fourth lens group IV, and the fifth lens group V move to the image forming unit LV side, and the third lens group III moves to the enlargement side. To do. The first lens group I and the sixth lens group VI do not move during focusing.

The first lens group I includes, in order from the reduction side, a biconvex lens, a double-sided aspherical biconvex lens, a “three-piece cemented lens in which a biconvex lens, a biconcave lens, and a biconvex lens are cemented”, a double-sided aspherical biconvex lens, The lens includes a cemented lens in which a biconcave lens and a positive meniscus lens are cemented, an aperture stop, a biconvex lens, and a cemented lens in which a positive meniscus lens and a biconcave lens are cemented.
The biconvex lens on the reduction side in the “three-piece cemented lens” in the first lens group I is the positive lens P1, and the biconvex lens on the magnification side is the positive lens P2.

  The second lens group II is composed of “a cemented lens of a biconvex lens and a biconcave lens cemented on its enlargement side”, and the third lens group III is composed of a biconvex lens and “a cemented biconvex lens and a negative meniscus lens. The fourth lens group IV includes a double-sided aspherical biconvex lens and a negative meniscus lens. The fifth lens group V includes a biconvex lens and a cemented lens in which a positive meniscus lens and a biconcave lens are cemented. ”And a double-sided aspherical biconcave lens, and the sixth lens group VI comprises one negative meniscus lens.

The data of Example 2 of the projection optical system is shown below.
Numerical aperture: 0.2222
The data of Example 2 is shown in Table 5.

“Variable intervals with focusing”
Table 6 shows variable intervals associated with focusing at a short distance, a reference distance, and a long distance.

"Aspherical data"
Table 7 shows the aspherical data.

"Parameter: TR value"
Table 8 shows the parameter TR with respect to the projection distance.

  In the second embodiment, the specifications of the image forming unit LV are the same as those of the first embodiment, including the distance (shift amount) in the Y direction from the optical axis to the center of the image forming unit: 5.5256 mm.

Spot diagrams corresponding to the respective angles of view F1 to F13 shown in FIG. 3 are shown in FIGS. As in the first embodiment, each spot diagram shows imaging characteristics (mm) on the screen surface for wavelengths: 638 nm (red), 550 nm (green), and 455 nm (blue).
Each of the spot diagrams in FIGS. 11 to 13 is when the temperature is 20 ° C., and the spot diagram shown in FIG. 8 is for a screen size of 150 inches when the temperature is raised by 20 ° C. to 40 ° C. Is. There is no difference from that when the temperature is 20 ° C. (FIG. 11), and it is clear that the projection optical system of Example 2 is “good temperature correction”.

In Example 2, as a glass material satisfying the conditions (1) and (2) for the positive lens P1 arranged on the reduction side from the aperture stop, “J-PKH1 nd of Hikari Glass Co., Ltd .: 1.5186, vd: 69.89” , DndT: 3.6, θgF: 0.5318), and the balance between the variation of the focal length due to the temperature change and the expansion of the mechanical holding portion due to the heat is balanced.
Further, the positive lens P1 is a spherical lens to reduce the cost. Further, as a glass material satisfying the conditional expressions (3) and (4) for the positive lens P2 arranged on the reduction side from the aperture stop, “OH-ARA S-FPL51 nd: 1.49700 vd: 81.54, dndT: −6 .2, θgF: 0.5375, ΔθgF: 0.028 ”is used to suppress the occurrence of chromatic aberration.

  Temperature compensation is performed by using a positive lens P2 made of a material having a negative and large refractive index temperature coefficient and a positive lens P1 made of a material having a positive and large refractive index temperature formation.

"Example 3"
As shown in FIG. 16, the refractive optical system in the projection optical system of Example 3 includes a first lens group I having a positive refractive power and a positive refractive power sequentially from the image forming unit LV side toward the enlargement side. A second lens group II having a negative refractive power, a third lens group III having a negative refractive power, and a fourth lens group IV having a positive refractive power.
As shown in FIG. 15, on the enlargement side of the refractive optical system 31, a flat mirror 32 and a concave mirror 33 are arranged as a refractive optical system as shown in FIG.
In the third embodiment, a free curved surface is employed as the mirror surface shape of the concave mirror 33.
During focusing from the long distance side to the short distance side, the second lens group II and the third lens group III move to the image forming unit side, and the fourth lens group IV moves to the enlargement side. The first lens group I does not move during focusing.

  The first lens group I includes, in order from the reduction side, a double-sided aspherical biconvex lens, a positive meniscus lens, a negative meniscus lens, “a cemented lens in which a negative meniscus lens and a positive meniscus lens are cemented”, an aperture stop, and a negative meniscus lens. And a double-sided aspherical biconvex lens, a negative meniscus lens, a “junction lens in which a biconvex lens and a biconcave lens are cemented”, and a biconvex lens.

  The positive meniscus lens with the second convex surface from the reduction side facing the enlargement side is the positive lens P1, and the positive meniscus lens in the cemented lens provided on the reduction side of the aperture stop is the positive lens P2.

  The second lens group II is composed of one positive meniscus lens, the third lens group III is composed of a biconcave lens, a biconcave lens, and a double-sided aspheric negative meniscus lens, and the fourth lens group IV is composed of one sheet. It consists of a double-sided aspherical positive meniscus lens.

The data of Example 3 of the projection optical system is shown below.
Numerical aperture: 0.200
The data of Example 3 is shown in Table 9. The “surface number” shown in the leftmost column is the surface number 1 for the image forming unit LV, and the surface numbers 2 and 3 are the surfaces of the transparent parallel flat plate F. Surface number 4 is the lens surface on the most reduction side of the refractive optical system.

“Variable intervals with focusing”
Table 10 shows variable intervals associated with focusing at a short distance, a reference distance, and a long distance.

"Aspherical data"
Table 11 shows the aspherical data.

"Free-form surface data"
The free-form surface is a surface obtained by adding “**” to the surface number in the above data, and the data is shown in Table 12.

"Parameter: TR value"
Table 13 shows the parameter TR with respect to the projection distance.

  In Example 3, the specification of the image forming unit LV is as follows.

Dot size: 7.56um
Horizontal direction (X direction) Length: 14.55152mm
Longitudinal direction (Y direction) length: 8.1648 mm
Distance in the Y direction from the optical axis to the center of the image forming unit (shift amount): 5.3024 mm
In the in-focus state where the projected image is maximized, the “X- and Y-direction coordinates” of the incident side surface of the plane mirror 32, the concave mirror 33, and the dust-proof glass 34 from the vertex of the lens surface on the most magnified side, and the tilt angle Table 14 shows α (the angle (degree) clockwise between the surface normal and the optical axis (Z direction) is +).

The surface normal of the 35th surface (concave mirror 33) is an angle formed by the η axis and the optical axis in the above-described free-form surface definition formula.
Spot diagrams corresponding to the angles of view F1 to F13 shown in FIG. 3 are shown in FIGS. As in the first embodiment, each spot diagram shows imaging characteristics (mm) on the screen surface for wavelengths: 638 nm (red), 550 nm (green), and 455 nm (blue).
Each of the spot diagrams in FIGS. 17 to 19 is when the temperature is 20 ° C., and the spot diagram shown in FIG. 20 is for a screen size of 100 inches when the temperature is raised by 20 ° C. to 40 ° C. Is. It is clear that the difference is slightly different from that when the temperature is 20 ° C. (FIG. 11), and the projection optical system of Example 3 is also “good temperature correction”.

In Example 3, as a glass material satisfying the conditions (1) and (2) for the positive lens P1 arranged on the reduction side from the aperture stop, “OHARA L-BSL7 nd: 1.51633, vd: 64.06, dndT: 4.7, θgF: 0.5333 ”is used to balance the fluctuation of the focal length due to temperature change and the expansion of the mechanical holder due to heat.
Further, the positive lens P1 is a spherical lens to reduce the cost. Further, “S-FPM3 nd: 1.53775, vd: 74.70, dndT: −4.3” is used as a glass material that satisfies the conditional expressions (3) and (4) for the positive lens P2 disposed on the reduction side of the aperture stop. , ΘgF: 0.5392, ΔθgF: 0.0186 ”, the occurrence of chromatic aberration is suppressed.
Temperature compensation is performed by using a positive lens P2 made of a material having a negative and large refractive index temperature coefficient and a positive lens P1 made of a material having a positive and large refractive index temperature formation.

  Table 15 shows parameter values of the conditions (1) to (10) in the projection optical systems of Examples 1 to 3 listed above.

As is apparent from Table 15, the projection optical systems of Examples 1 to 3 and the image display apparatus using these satisfy the conditions (1) to (10).
Other examples of the optical glass suitable for the positive lens P1 include “K-PBK40 nd: 1.51760, vd: 63.50, dndT: 4.4, θgF: 0.5340 from Sumita Glass Co., Ltd.”. It is done. Of course, it is not limited to this.
Examples of the optical glass suitable for the positive lens P2 include glass types as shown in Table 16 in addition to the above. Of course, it is not limited to these glass materials.

In the first to third embodiments described above, the light passing through the refractive optical system forms an “intermediate image conjugate to the image information formed on the image forming unit LV” on the image forming unit LV side with respect to the concave mirror. . The intermediate image does not need to be formed as a planar image, and is also formed as a “curved surface image” in the first to third embodiments. The intermediate image is “magnified and projected by the concave mirrors 12, 22, and 33 arranged on the most magnified side, and projected onto the screen SC.
The “intermediate image” has field curvature and distortion, but can be corrected by using an aspherical surface or a free-form surface for the concave mirror. This reduces the burden of aberration correction of the refractive optical system, increases the degree of design freedom, and is advantageous for downsizing the projection optical system and thus the image display apparatus.

  In the embodiment of the image display device described above, dustproof glasses 13, 23, and 34 are installed between the concave mirror and the screen. In the above embodiment, “flat glass” is used as the dust-proof glass, but it may have a curvature or may be a “optical element having refractive power” such as a lens. Moreover, although it arrange | positions inclining with respect to the Y-axis, this angle may be arbitrary and may be "perpendicular to the Y-axis".

  In Embodiments 1 to 3, “one concave mirror” is used as the “reflective optical element having refractive power” of the reflective optical system, but a plurality of concave mirrors may be used. In the third embodiment, the reflection optical system is constituted by a plane mirror and a concave mirror. However, the plane mirror 32 may have a refractive power by giving a curvature.

In the first to third embodiments, the positive lens P1 and the positive lens P2 are arranged in the “first lens group I that does not move during focusing. However, the present invention is not limited to this, and one or more movable lenses that move or move during focusing. The positive lens P1 and the positive lens P2 may be disposed in the group.
In Examples 1 to 3, the lens barrel that holds the positive lens P1 and the positive lens P2 is made of “aluminum having high thermal conductivity”.

  As described above, according to the present invention, the following novel projection optical system and image display apparatus can be realized. The projection optical system has a refractive optical system and a reflective optical system, and the influence of heat is taken into consideration.

[1]
A projection optical system for enlarging and projecting an image displayed on an image forming unit (LV) of an image display element onto a projection surface (SC), and a refractive optical system (11, 21, 31) having a plurality of lens groups And a reflective optical system (12, 22, 32, 33), the reflective optical system has at least one reflective optical element having refractive power, and the refractive optical system includes two types of positive lenses. Each of the positive lenses P1 has one or more P1 and P2 and the temperature coefficient of relative refractive index at the D-line in the range of 20 ° C. to 40 ° C .: dndTP1, Abbe number: vdP1.
(1) 2 <dndTP1
(2) 60 <vdP1
The positive lens P2 is formed of a lens material satisfying
Abbe number: vdP2 is the condition:
(3) 50 <vdP2
And the refractive indices for g-line, F-line, d-line, and C-line are ng, nF, nd, and nC, respectively.
θgF2 = (ng−nF) / (nF−nC)
ΘgF2 defined by the above and the Abbe number: vdP2
ΔθgF2 = θgF2 − (− 0.001618 × vdP2 + 0.6415)
ΔθgF2 defined by the condition:
(4) 0.004 <ΔθgF2
Projection optical system (Examples 1 to 3) formed of a lens material satisfying the above.

[2]
[1] The projection optical system according to [1], wherein the focal length of the positive lens P1 at the d-line: FP1, and the focal length of the positive lens P2 at the d-line: FP2 are:
(5) 0.1 <FP2 / FP1 <2
Projection optical system satisfying the above (Examples 1 to 3).

[3]
The projection optical system according to [1] or [2], wherein the positive lens P1 is a spherical lens (Examples 1 to 3).

[4]
The projection optical system according to any one of [1] to [3], wherein a temperature coefficient of relative refractive index of the lens material of the positive lens P2 with respect to a D line in a range of 20 ° C. to 40 ° C .: dndTP2 is ,conditions:
(6) 0> dndTP2
Projection optical system satisfying the above (Examples 1 to 3).

[5]
The projection optical system according to any one of [1] to [4], wherein the positive lens P1 and the positive lens P2 are included in a lens group (I) including an aperture stop (S). (Examples 1-3).

[6]
The projection optical system according to any one of [1] to [5], wherein the positive lens P1 is disposed closer to the reduction side than the aperture stop (S) (Examples 1 to 3). ).

[7]
The projection optical system according to any one of [1] to [6], wherein both the positive lenses P1 and P2 are included in the lens group (I) on the most reduction side (Example) 1-3).

[8]
The projection optical system according to any one of [1] to [7], having one or more moving lens groups that move or move during focusing, wherein the two positive lenses P1 and P2 are: A projection optical system included in the same moving lens group.

[9]
The projection optical system according to any one of [1] to [7], wherein the positive lens P1 and the positive lens P2 are included in a lens group that does not move during focusing (Examples 1 to 3).

[10]
The projection optical system according to any one of [1] to [9], wherein the holding member that holds the positive lens P1 and the positive lens P2 is a metal (Examples 1 to 3).

[11]
The projection optical system according to any one of [1] to [10], wherein the reflective optical element having refractive power in the reflective optical system is a single concave mirror (12, 22, 33). System (Examples 1-3).

[12]
[1] to [11] The projection optical system according to any one of [1] to [11], wherein the refractive optical system is sequentially arranged from the reduction side to the enlargement side in order from the first to sixth lens groups (I to VI). ) (FIGS. 1 and 2).

[13]
[1] to [11] The projection optical system according to any one of [1] to [11], wherein the refractive optical system is sequentially arranged from the reduction side to the enlargement side in order from the first to fourth lens groups (I to IV). (Example 3).

[14]
An image display apparatus that displays an image by enlarging and projecting an image displayed on an image forming unit (LV) of an image display element on a projection surface (SC) by a projection optical system (11, 21, 31), An image display device using the projection optical system according to any one of [1] to [13] (FIGS. 1, 9, and 15).

[15]
[14] The image display device according to [14], wherein the projection optical system according to [11] is used, and among the intersections of the concave mirror and the imaging light beam, the projection target is in a direction perpendicular to the projection surface. Ratio between the distance P in the direction perpendicular to the projection surface from the intersection P at which the distance to the projection surface is maximum to the projection surface: PL and the horizontal width W of the maximum image projected on the projection surface: TR (= PL / W) is the condition:
(7) TR <0.35
Display apparatus satisfying the above (FIGS. 1, 9, 15 and Examples 1 to 3).

[16]
The image display device according to [14] or [15], wherein an intersection between the optical axis of the refractive optical system and the image forming unit (LV) in the projection optical system, and the image forming unit of the refractive optical system The distance on the optical axis between the closest lens and the image forming unit: BF, and the maximum value of the distance between the optical axis and the image forming unit: Y are:
(8) BF / Y <3.5
Display apparatus satisfying the above (FIGS. 1, 9, 15 and Examples 1 to 3).

[17]
[14] In the image display device according to any one of [16], the pixel pitch of the image forming unit: PT, and the maximum value of the distance between the optical axis of the refractive optical system and the image forming unit: Y is the condition:
(9) PT / Y <0.001
Display apparatus satisfying the above (FIGS. 1, 9, 15 and Examples 1 to 3).

[18]
[14] The image display device according to any one of [17], wherein an intersection of the optical element on the enlargement side with respect to the refractive optical system and the imaging light beam is orthogonal to the image forming unit. Intersection point Q having the maximum distance from the image forming unit in the direction to be performed, distance in the direction from the image forming unit: PLQ, and the maximum value of the distance between the optical axis of the refractive optical system and the image forming unit : Y is the condition:
(10) 10 <PLQ / Y <30
Display apparatus satisfying the above (FIGS. 1, 9, 15 and Examples 1 to 3).

The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the specific embodiments and examples described above, and is described in the claims unless specifically limited by the above description. Various modifications and changes can be made within the scope of the gist of the invention.
The effects described in the embodiments and examples of the present invention are merely a list of preferred effects resulting from the invention, and the effects of the invention are not limited to those described in the embodiments. .

Image forming unit of LV image display element
H Image display device
LS illumination optical system
F Transparent parallel plate
Pr prism
SC Projected surface (screen)
11, 21, 31 Refractive optical system
S Aperture stop
P1 positive lens P1
P2 positive lens P2
12, 22 Reflective optical system (concave mirror)
32, 33 Reflective optical system
13, 23, 34 Dust-proof glass

JP 2007-079524 A JP 2009-251458 A Japanese Patent No. 4668159

Claims (18)

A projection optical system that enlarges and projects an image displayed on an image forming unit of an image display element on a projection surface,
A refractive optical system having a plurality of lens groups, and a reflective optical system;
The reflective optical system has at least one reflective optical element having refractive power,
The refractive optical system has one or more of two positive lenses P1 and P2, respectively.
The positive lens P1 is
Temperature coefficient of relative refractive index at D line in the range of 20 ° C. to 40 ° C .: dndTP1, Abbe number: vdP1 are the conditions:
(1) 2 <dndTP1
(2) 60 <vdP1
Formed by a lens material that satisfies
The positive lens P2 is
Abbe number: vdP2 is the condition:
(3) 50 <vdP2
And the refractive indices for g-line, F-line, d-line, and C-line are ng, nF, nd, and nC, respectively.
θgF2 = (ng−nF) / (nF−nC)
ΘgF2 defined by the above and the Abbe number: vdP2
ΔθgF2 = θgF2 − (− 0.001618 × vdP2 + 0.6415)
ΔθgF2 defined by the condition:
(4) 0.004 <ΔθgF2
Projection optical system formed of a lens material that satisfies the above requirements. The projection optical system according to claim 1,
The focal length of the positive lens P1 at the d line: FP1 and the focal length of the positive lens P2 at the d line: FP2
(5) 0.1 <FP2 / FP1 <2
Projection optical system that satisfies The projection optical system according to claim 1 or 2,
A projection optical system in which the positive lens P1 is a spherical lens. The projection optical system according to any one of claims 1 to 3,
The temperature coefficient of relative refractive index of the lens material of the positive lens P2 with respect to the D line in the range of 20 ° C. to 40 ° C .: dndTP2 is the condition:
(6) 0> dndTP2
Projection optical system that satisfies The projection optical system according to any one of claims 1 to 4,
A projection optical system in which the positive lens P1 and the positive lens P2 are included in a lens group including an aperture stop. A projection optical system according to any one of claims 1 to 5,
A projection optical system in which the positive lens P1 is disposed on the reduction side with respect to the aperture stop. The projection optical system according to any one of claims 1 to 6,
A projection optical system in which both the positive lenses P1 and P2 are included in the lens group closest to the reduction side. A projection optical system according to any one of claims 1 to 7,
A projection optical system that includes one or more moving lens groups that move or move during focusing, and the two positive lenses P1 and P2 are included in the same moving lens group. A projection optical system according to any one of claims 1 to 7,
The positive lens P1 and the positive lens P2 are projection optical systems included in a lens group that does not move during focusing. The projection optical system according to any one of claims 1 to 9,
A projection optical system in which a holding member for holding the positive lens P1 and the positive lens P2 is a metal. A projection optical system according to any one of claims 1 to 10,
A projection optical system in which the reflective optical element having refractive power in the reflective optical system is a single concave mirror. The projection optical system according to any one of claims 1 to 11,
A projection optical system in which the refractive optical system is configured by arranging first to sixth lens groups sequentially from the reduction side to the enlargement side. The projection optical system according to any one of claims 1 to 11,
A projection optical system in which the refractive optical system is configured by sequentially arranging first to fourth lens groups from the reduction side to the enlargement side. An image display device that enlarges and projects an image displayed on an image forming unit of an image display element onto a projection surface by a projection optical system, and displays the image.
An image display device using the projection optical system according to any one of claims 1 to 13. The image display device according to claim 14,
The projection optical system according to claim 11 is used.
Of the intersections between the concave mirror and the imaging light beam, the direction perpendicular to the projection surface from the intersection P that maximizes the distance to the projection surface in the direction perpendicular to the projection surface. The distance between PL and the maximum image width projected on the projection surface: W ratio: TR (= PL / W) is the condition:
(7) TR <0.35
An image display device that satisfies the requirements. The image display device according to claim 14 or 15,
The distance on the optical axis between the intersection of the optical axis of the refractive optical system and the image forming unit in the projection optical system and the image forming unit of the lens closest to the image forming unit of the refractive optical system: BF, the maximum value of the distance between the optical axis and the image forming unit: Y is the condition:
(8) BF / Y <3.5
An image display device that satisfies the requirements. The image display device according to any one of claims 14 to 16, comprising:
The pixel pitch of the image forming unit: PT, the maximum value of the distance between the optical axis of the refractive optical system and the image forming unit: Y, the conditions:
(9) PT / Y <0.001
An image display device that satisfies the requirements. The image display device according to any one of claims 14 to 17,
Of the intersections between the optical elements on the magnification side of the refractive optical system and the imaging light rays, the intersection Q where the distance from the image formation unit is the maximum in the direction orthogonal to the image formation unit, and the image formation The distance in the direction from the part: PLQ, and the maximum value of the distance between the optical axis of the refractive optical system and the image forming part: Y are the conditions:
(10) 10 <PLQ / Y <30
An image display device that satisfies the requirements.

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