JP6598050B2 - Projection device and projection system - Google Patents

Description

  The present invention relates to a projection device for enlarging and projecting an image displayed on an image display element onto a projection surface such as a screen, and a projection system including the projection device and the screen.

The projection device illuminates a display screen of an image display element called a light valve such as a DMD (Digital Micromirror Device) or a liquid crystal display panel, and an enlarged image of a display image of the image display element is received by a projection optical system. It is comprised so that it may project on the screen which forms a projection surface.
In recent years, in particular, there has been an increasing demand for front projection projectors having a short projection distance and a very short projection distance capable of displaying a large screen. As a means for realizing a small and ultra-short projection distance, a combination of a refractive optical system and a curved mirror is disclosed in, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2007-079524) and Patent Document 2 (Japanese Patent Laid-Open No. 2009-251458). ), Patent Document 3 (Japanese Patent Laid-Open No. 2011-242606), Patent Document 4 (Japanese Patent Laid-Open No. 2009-216883), and the like.
In recent years, even in such ultra-short projection projectors, there is a strong demand for higher brightness. At the same time, sufficient consideration is given to temperature characteristics due to the heat generated by absorbing light from the lamp and power supply. An optical system is required.

In particular, in a projector with an ultra short projection distance, since the projection angle is large, the depth of focus is only about several centimeters at the point farthest from the optical axis, which is the axis shared by the peripheral part, particularly the refractive optical system. It is very narrow compared to the front projector. For this reason, the occurrence of curvature of field due to the temperature rise, which has not been a major problem with conventional projectors, has resulted in a significant problem that the focal position of the periphery of the screen is greatly displaced, resulting in significant degradation of resolution. .
However, Patent Documents 1 to 4 do not describe any correction of curvature of field due to a temperature rise, and are insufficient when considering the specifications of recent projectors.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a small and high-performance projection apparatus that has a very short projection distance and can achieve high brightness.

In order to achieve the above-mentioned object, the present invention
A projection apparatus for magnifying and projecting an image displayed on the image display element onto a screen, the projection apparatus, a projection having a refractive optics and a reflective optics having a reflective optical element having at least one power An optical system , wherein the refractive optical system has at least one cemented lens;
In the refractive optical system,
The temperature coefficient of the relative refractive index at the e-line in the range of 40-60 degrees of the positive lens P1 is dnTP,
The partial dispersion ratio of g-line and F-line of the positive lens P1 is θgFP,
The temperature coefficient of the relative refractive index at the e-line in the range of 40-60 degrees of the negative lens N1 is dnTN,
The partial dispersion ratio of the negative lens N1 is θgFN,
The partial dispersion ratio θgf is represented by the formula: θgf = (Ng−NF) / (NF−NC), where θgf is the partial dispersion ratio.
The refractive index for g-line is Ng,
The refractive index for F-line is NF,
Let NC be the refractive index for C-line,
The cemented lens has the following conditional expressions (1), (2), (3), (4):
4 <dnTP (1)
0.61 <θgFP (2)
3 <dnTN (3)
0.59 <θgFN (4)
It includes at least one positive lens P1 and one negative lens N1 that satisfy the above.

According to the present invention, there is provided a projection apparatus for enlarging and projecting an image displayed on an image display element on a screen, the projection apparatus including a refractive optical system and a reflective optical element having at least one power. A projection optical system having an optical system, the refractive optical system having at least one cemented lens,
In the refractive optical system,
The temperature coefficient of the relative refractive index at the e-line in the range of 40-60 degrees of the positive lens P1 is dnTP,
The partial dispersion ratio of g-line and F-line of the positive lens P1 is θgFP,
The temperature coefficient of the relative refractive index at the e-line in the range of 40-60 degrees of the negative lens N1 is dnTN,
The partial dispersion ratio of the negative lens N1 is θgFN,
The partial dispersion ratio is θgf, and the partial dispersion ratio θgf is expressed by the formula: θgf = (Ng−NF) / (NF−NC),
The refractive index for g-line is Ng,
The refractive index for F-line is NF,
Let NC be the refractive index for C-line,
The cemented lens has the following conditional expressions (1), (2), (3), (4):
4 <dnTP (1)
0.61 <θgFP (2)
3 <dnTN (3)
0.59 <θgFN (4)
By providing at least one positive lens P1 and one negative lens N1 that satisfy the above conditions, it is possible to provide a projection device that has a very short projection distance, can achieve high brightness, is small, has high performance, and has excellent temperature characteristics. it can.

1 is a cross-sectional view showing a configuration of a projection apparatus according to a first embodiment of the present invention and Example 1 together with an optical path. FIG. It is explanatory drawing which shows the arrangement | positioning relationship between the center of the image formation part in which an image is formed, and an optical axis, and the image formation part has shifted predetermined amount to the Y direction with respect to the optical axis. It is a 1st embodiment of the present invention, and is a sectional view showing a moving position of a focusing lens for every projection size of a projection optical system used for a projection device concerning Example 1, among these (a) Is the case where the projection size is on the far side (100 inches), and (b) shows the case where the projection size is on the near side (80 inches). FIG. 6 is a characteristic diagram showing the relationship between the height from the optical axis of a double-sided aspheric negative meniscus lens included in the third lens group in Example 1 and the power difference in a room temperature and 40 ° environment. In the projection optical system according to Example 1 of the present invention, the angle of view (evaluation point) of the image display area virtually displayed on the image display element with the lens optical axis of the refractive optical system as the origin is shown. is there. It is a figure which shows the spot diagram on the screen (in the case of 100 inches) of the light emitted from each evaluation point shown in FIG. It is a figure which shows the spot diagram on the screen (in the case of 80 inches) of the light emitted from each evaluation point shown in FIG. It is a figure which shows the spot diagram on the screen (in the case of 60 inches) of the light emitted from each evaluation point shown in FIG. It is a figure which shows the spot diagram on the screen (in the case of 100 inches) of the light emitted from each evaluation point shown in FIG. 5 when temperature rises from room temperature (20 degree | times) to 20 degree | times. It is a figure which shows the spot diagram on the screen (in the case of 80 inches) of the light emitted from each evaluation point shown in FIG. 5 when temperature rises from room temperature (20 degree | times) to 20 degree | times. It is a figure which shows the spot diagram on the screen (in the case of 60 inches) of the light emitted from each evaluation point shown in FIG. 5 when temperature rises from room temperature (20 degree | times) to 20 degree | times. It is the 2nd Embodiment of this invention, and is sectional drawing which shows the structure of the projection apparatus which concerns on Example 2 with an optical path. It is a 2nd embodiment of the present invention, and is a sectional view showing a movement position of a focusing lens for every projection size of a projection optical system used for a projection device concerning Example 2, and (a) ) Is for a long distance (100 inches), and (b) is a case where the projection size is a short distance (80 inches). FIG. 6 is a characteristic diagram showing the relationship between the height from the optical axis of a double-sided aspheric negative meniscus lens included in the third lens group in Example 2 and the power difference between room temperature and 40 ° environment. 6 is a diagram showing a spot diagram on a 100-inch screen corresponding to each evaluation point (each angle of view) shown in FIG. 5 in the projection apparatus according to Example 2. FIG. FIG. 6 is a diagram showing a spot diagram on an 80-inch screen corresponding to each evaluation point (each angle of view) shown in FIG. 5 in the projection apparatus according to Example 2. FIG. 6 is a diagram showing a spot diagram on a 60-inch screen corresponding to each evaluation point (each angle of view) shown in FIG. 5 in the projection apparatus according to Example 2. 6 is a diagram showing a spot diagram on a 100-inch screen corresponding to each evaluation point (each angle of view) shown in FIG. 5 in the projection apparatus according to Example 2. FIG. FIG. 6 is a diagram showing a spot diagram on an 80-inch screen corresponding to each evaluation point (each angle of view) shown in FIG. 5 in the projection apparatus according to Example 2. FIG. 6 is a diagram showing a spot diagram on a 60-inch screen corresponding to each evaluation point (each angle of view) shown in FIG. 5 in the projection apparatus according to Example 2.

Hereinafter, based on an embodiment of the present invention, a projection apparatus according to the present invention and a projection system including the projection 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.
The present invention is a projection apparatus for enlarging and projecting an image displayed on an image display element on a screen, the projection apparatus including a refractive optical system and a reflective optical element having at least one power. has a projection optical system having bets in the refractive optical system includes at least one cemented lens, the cemented lens, the following conditional expression (1), (2), (3), (4) It is characterized by including at least one positive lens P1 and one negative lens N1 to be satisfied (corresponding to claim 1).
4 <dnTP (1)
0.61 <θgFP (2)
3 <dnTN (3)
0.59 <θgFN (4)
Where dnTP: temperature coefficient of relative refractive index at e-line in the range of 40-60 degrees of the positive lens P1 θgFP: partial dispersion ratio of g-line and F-line of the positive lens P1 dnTP: 40-60 of the negative lens N1 The temperature coefficient of the relative refractive index at the e-line in the angle range θgFN: partial dispersion ratio of the negative lens N1 θgf: partial dispersion ratio, and the partial dispersion ratio θgf is expressed by the equation: θgf = (Ng−NF) / (NF−NC )
Ng: Refractive index for g-line NF: Refractive index for F-line NC: Refractive index for C-line

  When the glass materials of the positive lens P1 and the negative lens N1 satisfy the conditional expressions (1) and (3), not only the focal length change due to temperature rise can be corrected by the two lenses, but also the image. The change in surface curvature can also be adjusted to a high degree, and in an ultra-short projection projector, good resolution can be obtained every corner even when the temperature rises.

Further, temperature compensation can be performed by satisfying conditional expressions (1) and (3), but this is not sufficient for correcting aberrations, particularly correction of chromatic aberration. Conditional expressions (2) and (4) It is possible to satisfy both optical performance and temperature characteristics for the first time by satisfying simultaneously. More preferably, it is desirable to satisfy the following conditional expressions (1 ′) and (3 ′): 4.8 <dnTP (1 ′)
3.5 <dnTN (3 ')
More preferably, the cemented lens is preferably disposed on the enlargement side with respect to the aperture stop (corresponding to claim 2). With the arrangement as described above, aberration correction can be performed effectively. Here, the aperture stop means that the thickness of the bundle of light rays (total light flux) from the entire image display element passing through the refractive optical system is the smallest.

More preferably, the cemented lens, it is preferable (corresponding to claim 3) included in the lens group including the apertures aperture. A lens group having an aperture stop is a lens group that easily rises in temperature because light concentrates. By arranging the cemented lens in the lens group, a projection optical system having good temperature characteristics can be obtained.
More preferably, the cemented lens is preferably included in a lens group closest to the image display element (corresponding to claim 4), and the cemented lens is disposed in a lens group closest to the image display element. Thus, a projection optical system with good temperature characteristics can be obtained.
More preferably, the cemented lens is preferably included in a lens group that does not move during focusing (corresponding to claim 5). This is because good temperature characteristics can be obtained even in each image size.

More preferably, when an axis shared by a plurality of axially symmetric lenses of the refractive optical system is an optical axis A, a lens that moves a resin lens that satisfies the following conditional expressions (5) and (6) during focusing: It is desirable to have at least one sheet in the group (corresponding to claim 6).
| P40d (h) −P20d (h) | × FP <0.02 (5)
However,
| H | <0.85 × D (6)
h: Height from the optical axis A D: Distance between the optical axis A and the point where the distance from the optical axis A is the maximum among the intersections of the reduction side lens surface and the light beam FP: The resin lens PL The paraxial focal length P40d (h): power at the point of the height h from the optical axis A at a temperature of 40 degrees P20d (h): the temperature at the point of the height h from the optical axis A of 20 degrees It is the power of time.

  By using an aspherical or free-form resin lens for the group that moves at the time of focusing, it is possible to highly correct the image plane particularly around the screen. However, if the effect of correcting the image plane is to be increased, the movement of the image plane due to a change in power increases when the temperature rises. Conditional expression (5) shows the difference in power at the lens height h, which may be 20 degrees above room temperature and at room temperature, and conditional expression (6) shows the range of the height h. Yes. In the lens diameter range of conditional expression (6), by suppressing the power difference of conditional expression (5) below the upper limit, it is possible to minimize the tilt of the image plane when the temperature rises. Further, by simultaneously satisfying conditional expressions (1), (2), (3), (4), (5), and (6), the image plane around the screen is highly corrected even when the temperature rises. It becomes possible.

More preferably, the resin lens is preferably included in a lens group that moves during focusing (corresponding to claim 7). By adopting the above arrangement, it becomes possible to effectively suppress the curvature of field accompanying the temperature change.
More preferably, the reflecting optical element is a concave mirror and preferably has a free-form surface (corresponding to claim 8). By using a free-form surface, it is possible to effectively correct field curvature .
Further preferably, an axial multiple lenses axisymmetric of the refractive optical system is shared when the optical axis A, it is desirable (corresponding to claim 9) satisfying the formula (8).
BF / Y <4.0 (8)
However,
BF: Distance between the intersection of the surface including the image display element and the optical axis A and the image display element side surface vertex of the lens closest to the image display element Y: The optical axis A and the end of the image forming unit The maximum distance from the part.

By satisfying the conditional expression (8), the projection optical system can be further downsized. More preferably, it is desirable to satisfy the following conditional expression (8 ′).
BF / Y <3.5 (8 ')
More preferably, the projection optical system is a non-telecentric optical system (corresponding to claim 10 ). Using a non-telecentric optical system is advantageous for downsizing.

  [First Embodiment]

Next, the configuration of the projection optical system of the projection apparatus of the present invention described above will be described in detail.
FIG. 1 is a sectional view showing a configuration of a projection apparatus according to a first embodiment of the present invention and Example 1 together with an optical path.
FIG. 2 is an explanatory diagram showing the positional relationship between the center of the image forming unit on which an image is formed and the optical axis. The image forming unit is shifted by a predetermined amount in the Y direction with respect to the optical axis.
FIG. 3 is a sectional view showing the moving position of the focusing lens for each projection size of the projection optical system used in the projection apparatus according to the first embodiment of the present invention and Example 1. Of these, (a) shows the case where the projection size is on the far side (100 inches), and (b) shows the case where the projection size is on the near side (80 inches).
In FIG. 1, reference numeral LV denotes an image forming unit. Specifically, the image forming unit LV is a light valve such as “DMD (Digital Micro-mirror Device)”, “transmission type liquid crystal panel”, “reflection type liquid crystal panel”, etc. The portion that is present is “the portion that forms the image to be projected”. When the image forming unit LV does not have a function of emitting light as in the case of DMD or the like, the image information formed in the image forming unit LV is illuminated with illumination light from the illumination optical system LS. The illumination optical system LS preferably has a function of efficiently illuminating the image forming unit LV.

In order to make the illumination more uniform, for example, a rod integrator or a fly eye integrator can be used. 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. A monochromatic light source such as a monochromatic LED or LD (laser diode) can also be used. Since the illumination optical system is a well-known technique, a specific example is omitted here.
In the present embodiment, a DMD is assumed as the image forming unit LV. Further, in the present embodiment, the “image forming unit that does not have the function of emitting light” is presupposed, but the “self-light emitting method having a function of emitting the generated image” may be used.
The parallel flat plate F disposed in the vicinity of the image forming unit LV is assumed to be a cover glass (seal glass) of the image forming unit LV. H indicates a projection device exterior portion, and S indicates a stop (aperture stop). Moreover, SC in FIG. 1 shows a screen.

In FIG. 1, the optical path diagram in the case of 80 inches where the front ball is extended most is shown. As shown in FIG. 1, an axis shared by a plurality of axisymmetric lenses is an optical axis A, a direction parallel to the optical axis A is a Z-axis direction, and a light beam that is emitted from the center of the image display element and passes through the center of the diaphragm S. An axis perpendicular to the axis A in the plane including the Y axis and an optical axis A and an axis perpendicular to the Y axis are assumed to be X. In FIG. 1, the clockwise rotation direction is defined as + α direction.
A light beam that is two-dimensionally intensity-modulated by the DMD by image information becomes a projection light beam as object light. The projected light beam from the image forming unit LV passes through the refractive optical system 11, the folding mirror 12, and the free-form curved concave mirror 13 to be an imaged light beam. That is, the image formed on the DMD (image forming unit LV) is enlarged and projected onto the screen SC by the projection optical system, and becomes a projected image. Here, the surface on which the image is formed is defined as an image forming surface. The optical elements of the refractive optical system 11 share an optical axis, and the image forming unit LV is shifted in the Y direction with respect to the optical axis A as shown in FIG.

In the first embodiment, the system is configured by using the refractive optical system 11, the folding mirror 12, and one free-form curved concave mirror 13. The number of mirrors may be increased, but this is not preferable because the configuration is complicated and the size and cost are increased.
As the brightness increases, in the illumination optical system LS, the heat generated by absorbing power and heat from the lamp and the lamp increases. Especially in projectors using non-telecentric optical systems, the amount of light absorbed into the lens barrel increases greatly by shortening the back focus for miniaturization. It is necessary to compensate for the temperature within this lens group.

Therefore, in Example 1, glass materials satisfying the conditional expressions (1), (2), (3), and (4) for the positive lens P1 and the negative lens N1 of the cemented lens disposed on the enlargement side from the stop S, respectively. (For example, S-NBH56 nd of OHARA, nd: 1.85478, νd: 24.799 dnTP: 5.1, θgFP: 0.6122, TAFD25 nd of HOYA: 1.90366, νd: 31.315 dnTN: 3.6 , ΘgFN: 0.5947) is used to balance the fluctuation of the focal length and the thermal expansion of the mechanical holding unit. In addition to the above, by making the positive lens closest to the image display element an aspherical lens, it is possible to adjust the temperature change of the field curvature more highly.
Further, by appropriately disposing the cooling mechanism, it is possible to suppress the temperature change and the temperature change of the field curvature with respect to the group that moves at the time of focusing including the aspherical lens.
The light passing through the refractive optical system 11 forms an intermediate image conjugate with the image information formed in the image forming unit LV as a spatial image on the image forming unit LV side with respect to the folding mirror 12. The intermediate image does not need to be formed as a planar image, and is formed as a curved surface image in both the first embodiment and the other embodiments. The intermediate image is enlarged and projected by the free curved concave mirror 13 arranged on the most magnified side, and projected on the screen SC. The intermediate image has field curvature and distortion, but this can be corrected by using the free-form curved concave mirror 13 as the concave mirror.

For this reason, the burden of aberration correction on the lens system is reduced, which increases the degree of design freedom and is advantageous for downsizing and the like. In addition, the free-form surface here means that the curvature in the X direction according to the position in the X direction is not constant at any position in the Y direction, and the Y direction according to the position in the Y direction at any position in the X direction. An anamorphic surface whose curvature is not constant.
It is desirable to install a dustproof glass 14 between the free curved concave mirror 13 and the screen SC. In the first embodiment, a flat glass is used as the dust-proof glass 14, but it may have a curvature or may be an optical element having a power such as a lens. In addition, although it is arranged to be inclined rather than perpendicular to the optical axis A, this angle may be arbitrary and may be perpendicular to the optical axis A.

Next, Embodiment 1 of the present invention will be described in detail with reference to FIG.
The meanings of symbols in Example 1 and Example 2 described later are as follows.
f: Focal length of 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 order aspherical constant Cj: Free-form surface coefficient The aspherical shape is the reciprocal of the paraxial radius of curvature (paraxial curvature). The following equation (9) is well known, where the height from the optical axis is H, the conic constant is K, the aspheric coefficients of the above orders are used, and X is the aspheric amount in the optical axis direction:

The shape is specified by giving a paraxial radius of curvature, a conic constant, and an aspherical coefficient.
In addition, the free-form surface shape is defined by taking the reciprocal of the paraxial radius of curvature (paraxial curvature) as C, the height from the optical axis as H, the conic constant as K, using the above-mentioned free-form surface coefficient, and X as the free-axis direction As the amount of curved surface, the following well-known formula (10)

  However,

The shape is specified by giving a paraxial radius of curvature, a conic constant, and a free-form surface coefficient.
As shown in FIG. 1, an axis that is in the normal direction of the image forming unit and is parallel to the optical axis A, which is an axis shared by the axisymmetric lens, is emitted from the center of the image display element. Of the in-plane axes including the passing light beam, the axis perpendicular to the axis A is the Y axis, the axis perpendicular to the optical axis A and the Y axis is the X axis, and in FIG. 1, the clockwise rotation direction is the + α direction. .
The radius of curvature p at the distance h from the optical axis in the aspherical surface was calculated using the following equation. The aspherical expression f (h) is differentiated by h and obtained using the following expression.

FIG. 3 shows the lens configuration of the refractive optical system according to the first embodiment of the present invention and Example 1, and the state of focusing. This refractive optical system has a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a negative refractive power in order from the image forming unit side to the enlargement side. A third lens group G3 and a fourth lens group G4 having a positive refractive power are arranged. Focusing with respect to fluctuations in the projection distance is such that the positive second lens group G2 and the negative third lens group G3 move to the image forming unit side when focusing from the long distance (100 inches) side to the short distance (80 inches) side. Then, the positive fourth lens group G4 moves to the enlargement side.
The first lens group G1 includes, in order from the image forming unit LV side, a first lens L1 including a double-sided aspherical biconvex lens having a convex surface having a larger curvature than the magnifying side on the image forming unit side, and a convex surface on the image forming unit side. A second lens L2 composed of a negative meniscus lens directed to the third lens L3, a third lens L3 composed of a negative meniscus lens having a convex surface directed toward the image forming portion, and a fourth lens composed of a positive meniscus lens directed toward the image forming portion. A cemented lens composed of L4, an aperture stop S, a fifth lens L5 composed of a negative meniscus lens having a convex surface facing the enlargement side, and a double-sided aspheric surface with a convex surface having a larger curvature than the image forming unit side facing the magnification side A sixth lens L6 made of a convex lens, a seventh lens L7 made of a negative meniscus lens having a convex surface facing the image forming portion, and a biconvex lens having a convex surface having a larger curvature than the image forming portion on the enlargement side A cemented lens composed of an eighth lens L8 and a ninth lens L9 composed of a biconcave lens having a concave surface having a larger curvature than the magnification side on the image forming unit side, and a convex surface having a larger curvature than the magnification side on the image forming unit side. And a tenth lens L10 composed of a directed biconvex lens.

The second lens group G2 is composed of a single eleventh lens L11 made of a positive meniscus lens having a convex surface facing the image forming unit.
The third lens group G3 includes a twelfth lens L12 made of a biconcave lens having a concave surface having a larger curvature than the magnification side on the image forming unit side, and a resin double-sided aspheric negative meniscus lens having a convex surface facing the image forming unit side. A thirteenth lens L13 made of PL is used.
The fourth lens group G4 includes a fourteenth lens L14 made of a double-sided aspheric positive meniscus lens having a convex surface facing the enlargement side.
A refractive optical system is constituted by the lens group, and a folding mirror 12 (surface 30) and a free-form curved concave mirror 13 (surface 31), which are plane mirrors, are installed on the enlargement side.
The eighth lens L8 is referred to as a positive lens P1, and the ninth lens L9 is referred to as a negative lens N1.
Table 1 below shows lens data. In the table, a surface number with * indicates an aspherical surface, and a surface number with ** indicates a free-form surface.

That is, in Table 1, the optical surfaces of the fourth surface, the fifth surface, the thirteenth surface, the fourteenth surface, the twenty-sixth surface, the twenty-seventh surface, the twenty-eighth surface, and the twenty-ninth surface marked with “*” are shown. The parameters of each aspheric surface in the equation (9) are as shown in Table 2 below.
In the aspheric coefficient, “En” represents “power of 10”, that is, “× 10n”, and for example, “E-05” represents “× 10-5”.

DA, DB, DC, DD, DE in Table 1 are variable intervals.
Among these, the variable distance DA is the distance between the first lens group G1 and the second lens group G2, that is, the variable distance between the surface 21 and the surface 22. The variable interval DB is the interval between the second lens group G2 and the third lens group G3, that is, the variable interval between the surface 23 and the surface 24. The variable distance DC is the distance between the third lens group G3 and the fourth lens group G4, that is, the variable distance between the surface 27 and the surface 28.
The variable distance DD is the distance between the fourth lens group G4 and the folding mirror 12, and DE is the variable distance between the free-form curved concave mirror 13 and the screen surface SC.
In this way, the projection optical system moves the second lens group G2 and the third lens group G3 to the image forming unit side in FIG. 3 when focusing from a long distance to a short distance side in focusing with respect to fluctuations in the projection distance. Then, the fourth lens group G4 moves to the enlargement side. Thus, by changing the enlargement ratio, the diagonal size of the projected image is adjusted from 80 inches to 100 inches in accordance with the projection size.
The surface distances DA, DB, DC, DD, DE at which the lens group distance changes during focus adjustment are shown in Table 1 as “Variable DA”, “Variable DB”, “Variable DC”, “Variable DD”, “Variable”. DE ”, and the surface separations DA to DE change as shown in Table 3 below with respect to the projected image diagonal sizes of 100, 80, and 60 inches.

  The free-form surface shape is given by the reciprocal of the paraxial radius of curvature (paraxial curve) C, the height H from the optical axis, the conic constant K, and the free-form surface coefficient shown in Table 4 below. As the amount of curved surface, the shape is specified by the above equation (10).

  The projection distance and TR have values as shown in the following table 5 according to the short distance, the reference, and the long distance. Here, TR is expressed as [distance from the intersection of free-form curved concave mirror 13 and axis A to the screen] / [screen width].

Hereinafter, other specific numerical values of the DVD used in the image forming unit LV of the first embodiment will be shown.
DMD size Dot size: 7.56μm
Horizontal length: 14.5152mm
Longitudinal length: 8.1648mm
Optical axis to element center: 5.30 mm
BF / Y: 3.45
Table 6 shows the position coordinates of the folding mirror 12 and the free curved concave mirror 13 from the apex in the in-focus state where the projection image of the lens located closest to the reflecting surface is maximum. Regarding rotation, the angle formed by the surface normal and the optical axis is shown.

FIG. 6 (in the case of 100 inches), FIG. 7 (in the case of 80 inches), and FIG. 8 (in the case of 60 inches) correspond to the respective spot angles shown in FIG. Each spot diagram shows imaging characteristics (mm) on the screen surface at wavelengths of 625 nm (red), 550 nm (green), and 425 nm (blue). It can be seen that a good image is formed.
Table 7 below shows the paraxial focal length of the first lens unit in the entire system in the case of 100 inches when the temperature is 20 degrees and the temperature is increased by 20 degrees.

It can be seen that the fluctuation of the focal length when the temperature changes is suppressed.
FIG. 9 to FIG. 11 show spot diagrams at various image sizes (100 inches, 80 inches, and 60 inches) when the temperature rises by 20 degrees from room temperature (20 degrees).
9 to 11 show good imaging performance even when the temperature rises.
In this embodiment, the values corresponding to the conditional expressions (1) to (8) are as follows and satisfy the conditional expressions (1) to (8), respectively.
Conditional expression (1): dnTP = 5.1
Conditional expression (2): θgFP = 0.6122
Conditional expression (3): dnTN = 3.6
Conditional expression (4): θgFN = 0.5947
Conditional expression (5): | P40d (h) −P20d (h) | × FP = 0.02 or less Conditional expression (6): 0.85 × D = 16.745
Conditional expression (7): TR = 0.261 (in the case of a short distance of 60 inches)
: TR = 0.254 (in case of standard 80 inch)
: TR = 0.249 (in the case of a long distance of 100 inches)
Conditional expression (8): BF / Y = 3.45
Further, as shown in FIG. 4, the conditional expression (5) is satisfied within the range of the conditional expression (6).
[Second Embodiment]

FIG. 12 is a cross-sectional view showing the configuration of the projection apparatus according to the second embodiment of the present invention and Example 2 together with an optical path.
FIG. 13 is a cross-sectional view showing the moving position of the focusing lens for each projection size of the projection optical system used in the projection apparatus according to the second embodiment of the present invention and Example 2. Of these, (a) shows the case where the projection size is on the far side (100 inches), and (b) shows the case where the projection size is on the near side (80 inches).
In FIG. 12, symbol LV indicates an image forming unit. Specifically, the image forming unit LV is a light valve such as “DMD (Digital Micro-mirror Device)”, “transmission type liquid crystal panel”, “reflection type liquid crystal panel”, etc. The portion that is present is “the portion that forms the image to be projected”. When the image forming unit LV does not have a function of emitting light as in the case of DMD or the like, the image information formed in the image forming unit LV is illuminated with illumination light from the illumination optical system LS. The illumination optical system LS preferably has a function of efficiently illuminating the image forming unit LV. In order to make the illumination more uniform, for example, a rod integrator or a fly eye integrator can be used. 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. A monochromatic light source such as a monochromatic LED or LD (laser diode) can also be used. Since the illumination optical system is a well-known technique, a specific example is omitted here.

In the present embodiment, a DMD is assumed as the image forming unit LV. Further, in the present embodiment, the “image forming unit that does not have the function of emitting light” is presupposed, but the “self-light emitting method having a function of emitting the generated image” may be used.
The parallel flat plate F disposed in the vicinity of the image forming unit LV is assumed to be a cover glass (seal glass) of the image forming unit LV. H indicates a projection device exterior portion, and S indicates a stop (aperture stop). Further, SC in FIG. 12 shows a screen.
FIG. 12 shows an optical path diagram in the case of 80 inches where the front ball is most extended. As shown in FIG. 12, an axis shared by a plurality of axisymmetric lenses is an optical axis A, a direction parallel to the optical axis A is a Z-axis direction, and a light beam that is emitted from the center of the image display element and passes through the center of the diaphragm S. An axis perpendicular to the axis A in the plane including the Y axis and an optical axis A and an axis perpendicular to the Y axis are assumed to be X. In FIG. 12, the clockwise rotation direction is defined as + α direction.
A light beam that is two-dimensionally intensity-modulated by the DMD by image information becomes a projection light beam as object light. The projected light beam from the image forming unit LV passes through the refractive optical system 11, the folding mirror 12, and the free-form curved concave mirror 13 to be an imaged light beam. That is, the image formed on the DMD (image forming unit LV) is enlarged and projected onto the screen SC by the projection optical system, and becomes a projected image.

Here, the surface on which the image is formed is defined as an image forming surface. The optical elements of the refractive optical system 11 share an optical axis, and the image forming unit LV is shifted in the Y direction with respect to the optical axis A as shown in FIG.
In the second embodiment, the system is configured by using the refractive optical system 11, the folding mirror 12, and one free-form curved concave mirror 13. The number of mirrors may be increased, but this is not preferable because the configuration is complicated and the size and cost are increased.
As the brightness increases, in the illumination optical system LS, the heat generated by absorbing power and heat from the lamp and the lamp increases. Especially in projectors using non-telecentric optical systems, the amount of light absorbed into the lens barrel increases greatly by shortening the back focus for miniaturization. It is necessary to compensate for the temperature within this lens group.

Therefore, in Example 2, glass materials satisfying conditional expressions (1), (2), (3), and (4) for the positive lens P1 and the negative lens N1 of the cemented lens disposed on the enlargement side from the stop S, respectively. (For example, S-NBH56 nd of OHARA, nd: 1.85478, νd: 24.799 dnTP: 5.1, θgFP: 0.6122, TAFD25 nd of HOYA: 1.90366, νd: 31.315 dnTN: 3.6 , ΘgFN: 0.5947) is used to balance the fluctuation of the focal length and the thermal expansion of the mechanical holding unit. In addition to the above, by making the positive lens closest to the image display element an aspherical lens, it is possible to adjust the temperature change of the field curvature more highly.
Further, by appropriately disposing the cooling mechanism, it is possible to suppress the temperature change and the temperature change of the field curvature with respect to the group that moves at the time of focusing including the aspherical lens.

The light passing through the refractive optical system 11 forms an intermediate image conjugate with the image information formed in the image forming unit LV as a spatial image on the image forming unit LV side with respect to the folding mirror 12. The intermediate image does not need to be formed as a planar image, and is formed as a curved surface image in both the second embodiment and the other embodiments. The intermediate image is enlarged and projected by the free-form curved concave mirror 13 arranged on the most enlarged side, and projected on the screen. The intermediate image has field curvature and distortion, but this can be corrected by using the free-form curved concave mirror 13 as the concave mirror. For this reason, the burden of aberration correction on the lens system is reduced, which increases the degree of design freedom and is advantageous for downsizing and the like. In addition, the free-form surface here means that the curvature in the X direction according to the position in the X direction is not constant at any position in the Y direction, and the Y direction according to the position in the Y direction at any position in the X direction. An anamorphic surface whose curvature is not constant.
It is desirable to install a dustproof glass 14 between the free curved concave mirror 13 and the screen SC. In the second embodiment, a flat glass is used as the dust-proof glass 14, but it may have a curvature or may be an optical element having a power such as a lens. In addition, although it is arranged to be inclined rather than perpendicular to the optical axis A, this angle may be arbitrary and may be perpendicular to the optical axis A.

FIG. 13 shows the lens configuration of the refractive optical system according to the second embodiment of the present invention and Example 2, and the state of focusing. This refractive optical system has a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a negative refractive power in order from the image forming unit side to the enlargement side. A third lens group G3 and a fourth lens group G4 having a positive refractive power are arranged. Focusing with respect to fluctuations in the projection distance is such that the positive second lens group G2 and the negative third lens group G3 move to the image forming unit side when focusing from the long distance (100 inches) side to the short distance (80 inches) side. Then, the positive fourth lens group G4 moves to the enlargement side.
The first lens group G1 includes, in order from the image forming unit LV side toward the magnifying side, a first lens L1 including a double-sided aspherical biconvex lens having a convex surface having a larger curvature on the image forming unit side than the magnifying side. A second lens L2 made of a negative meniscus lens having a convex surface facing the image forming part, a third lens L3 made of a negative meniscus lens having a convex surface facing the image forming part, and a positive meniscus lens having a convex surface facing the image forming part. A fourth lens L4, a cemented lens, an aperture stop S, a fifth lens L5 including a negative meniscus lens having a convex surface on the enlargement side, and a convex surface having a larger curvature than the image forming unit side on the enlargement side. A sixth lens L6 composed of a double-sided aspherical biconvex lens, a seventh lens L7 composed of a negative meniscus lens having a convex surface facing the image forming portion, and a convex surface having a larger curvature than the image forming portion are directed to the enlargement side. A cemented lens comprising an eighth lens L8 composed of a biconvex lens and a ninth lens L9 composed of a biconcave lens having a concave surface having a larger curvature on the image forming unit side than the magnification side, and a curvature on the image forming unit side from the magnification side. The tenth lens L10 is composed of a biconvex lens having a large convex surface.

The second lens group G2 is composed of a single eleventh lens L11 made of a positive meniscus lens having a convex surface facing the image forming unit.
The third lens group G3 includes a twelfth lens L12 made of a biconcave lens having a concave surface having a larger curvature than the magnification side on the image forming unit side, and a resin double-sided aspheric negative meniscus lens having a convex surface facing the image forming unit side. A thirteenth lens L13 made of PL is used.
The fourth lens group G4 includes a fourteenth lens L14 made of a double-sided aspheric positive meniscus lens having a convex surface facing the enlargement side.
A refractive optical system is constituted by the lens group, and a folding mirror 12 (surface 30) and a free-form curved concave mirror 13 (surface 31), which are plane mirrors, are installed on the enlargement side.
The eighth lens L8 is referred to as a positive lens P1, and the ninth lens L9 is referred to as a negative lens N1.
Table 8 below shows lens data. In the table, a surface number with * indicates an aspherical surface, and a surface number with ** indicates a free-form surface.

That is, in Table 8, the optical surfaces of the fourth surface, the fifth surface, the thirteenth surface, the fourteenth surface, the twenty-sixth surface, the twenty-seventh surface, the twenty-eighth surface, and the twenty-ninth surface are marked with “*”. The parameters of each aspheric surface in the equation (9) are as shown in Table 9 below.
In the aspheric coefficient, “En” represents “power of 10”, that is, “× 10n”, and for example, “E-05” represents “× 10-5”.

DA, DB, DC, DD, and DE in Table 8 are variable intervals.
Among these, the variable distance DA is the distance between the first lens group G1 and the second lens group G2, that is, the variable distance between the surface 21 and the surface 22. The variable interval DB is the interval between the second lens group G2 and the third lens group G3, that is, the variable interval between the surface 23 and the surface 24. The variable distance DC is the distance between the third lens group G3 and the fourth lens group G4, that is, the variable distance between the surface 27 and the surface 28.
The variable distance DD is the distance between the fourth lens group G4 and the folding mirror 12, and DE is the variable distance between the free-form curved concave mirror 13 and the screen surface SC.
In this way, the projection optical system moves the second lens group G2 and the third lens group G3 to the image forming unit side in FIG. 13 when focusing from a long distance to a short distance side in focusing with respect to fluctuations in the projection distance. Then, the fourth lens group G4 moves to the enlargement side. Thus, by changing the enlargement ratio, the diagonal size of the projected image is adjusted from 80 inches to 100 inches in accordance with the projection size.
The surface distances DA, DB, DC, DD, DE at which the lens group distance changes during focus adjustment are shown in Table 8 as “Variable DA”, “Variable DB”, “Variable DC”, “Variable DD”, “Variable”. DE ”, and the surface separations DA to DE change as shown in Table 3 below with respect to the projected image diagonal sizes of 100, 80, and 60 inches.

  The free-form surface shape is given by the reciprocal of the paraxial radius of curvature (paraxial curve) C, the height H from the optical axis, the conic constant K, and the free-form surface coefficient shown in Table 4 below. As the amount of curved surface, the shape is specified by the above equation (10).

  The projection distance and TR have values as shown in the following table 12 according to the short distance, the reference, and the long distance. Here, TR is expressed as [distance from the intersection of free-form curved concave mirror 13 and axis A to the screen] / [screen width].

Hereinafter, other specific numerical values of the DVD used in the image forming unit LV of the second embodiment will be shown.
DMD size Dot size: 7.56μm
Horizontal length: 14.5152mm
Longitudinal length: 8.1648mm
Optical axis to element center: 5.30 mm
BF / Y: 3.45
Table 13 shows the position coordinates of the folding mirror 12 and the free-form curved concave mirror 13 from the apex in the in-focus state where the projection image of the lens located closest to the reflecting surface is maximum. Regarding rotation, the angle formed by the surface normal and the optical axis is shown.

FIG. 15 (in the case of 100 inches), FIG. 16 (in the case of 80 inches), and FIG. 17 (in the case of 60 inches) show the spot diagrams corresponding to each angle of view shown in FIG. Each spot diagram shows imaging characteristics (mm) on the screen surface at wavelengths of 625 nm (red), 550 nm (green), and 425 nm (blue). It can be seen that a good image is formed.
Table 14 below shows the paraxial focal length of the first lens unit in the entire system in the case of 100 inches when the temperature is 20 degrees and the temperature is increased by 20 degrees.

It can be seen that the fluctuation of the focal length when the temperature changes is suppressed.
FIG. 18 to FIG. 20 show spot diagrams at various image sizes (100 inches, 80 inches, and 60 inches) when the temperature rises by 20 degrees from room temperature (20 degrees).
18 to 20, good imaging performance is shown even when the temperature rises.
In the case of Example 2, the values corresponding to the conditional expressions (1) to (8) are as follows and satisfy the conditional expressions (1) to (8), respectively.
Conditional expression (1): dnTP = 5.1
Conditional expression (2): θgFP = 0.6122
Conditional expression (3): dnTN = 3.6
Conditional expression (4): θgFN = 0.5947
Conditional expression (5): | P40d (h) −P20d (h) | × FP = 0.02 or less Conditional expression (6): 0.85 × D = 16.745
Conditional expression (7): TR = 0.261 (in the case of a short distance of 60 inches)
: TR = 0.254 (in case of standard 80 inch)
: TR = 0.249 (in the case of a long distance of 100 inches)
Conditional expression (8): BF / Y = 3.45.
Further, as shown in FIG. 14, the conditional expression (5) is satisfied within the range of the conditional expression (6).

According to the projection device specified by the embodiment and the specific numerical examples as described above, by specifying an appropriate glass material for each of the positive lens and the negative lens in the fixed group, it is small, high performance and temperature. It is possible to obtain an image projection apparatus with an ultra-short projection distance having excellent characteristics. In the first and second embodiments described above, preferred embodiments of the present invention have been shown, but the present invention is not limited to the contents thereof.
In particular, the specific shapes and numerical values of the respective parts exemplified in Example 1 and Example 2 are merely examples of implementations in carrying out the present invention, and the technical scope of the present invention is interpreted in a limited way by these. There should be no things.
Thus, the present invention is not limited to the contents described in the present embodiment, and can be appropriately changed without departing from the gist thereof.

DESCRIPTION OF SYMBOLS 11 Refractive optical system 12 Folding mirror 13 Free-form curved concave mirror 14 Dust-proof glass G1 1st lens group G2 2nd lens group G3 3rd lens group G4 4th lens group L1-L14 1st lens-14th lens LV Image formation part N1 Negative lens P1 Positive lens PL Double-sided aspheric negative meniscus lens made of resin DA to DE Variable distance A Optical axis F Parallel plate SC Screen

JP 2007-079524 A JP 2009-251458 A JP 2011-242606 A JP 2009-216883 A

Claims (10)

A projection apparatus for enlarging and projecting an image displayed on an image display element on a screen, the projection apparatus having a refractive optical system and a reflective optical system having a reflective optical element having at least one power A positive lens P1 that has at least one cemented lens in the refractive optical system, and the cemented lens satisfies the following conditional expressions (1), (2), (3), and (4): A projection apparatus comprising at least one negative lens N1.
4 <dnTP (1)
0.61 <θgFP (2)
3 <dnTN (3)
0.59 <θgFN (4)
However,
dnTP: temperature coefficient of relative refractive index at e-line in the range of 40-60 degrees of the positive lens P1 θgFP: partial dispersion ratio of g-line and F-line of the positive lens P1 dnTN: range of 40-60 degrees of the negative lens N1 The temperature coefficient of the relative refractive index at the e-line θgFN: the partial dispersion ratio of the negative lens N1 θgf: the partial dispersion ratio, and the partial dispersion ratio θgf is expressed by the equation: θgf = (Ng−NF) / (NF−NC) Represented,
Ng: Refractive index for g line NF: Refractive index for F line NC: Refractive index for C line   The projection apparatus according to claim 1, wherein the cemented lens is disposed on an enlargement side with respect to an aperture stop.   The projection apparatus according to claim 1, wherein the cemented lens is included in a lens group including an aperture stop.   4. The projection device according to claim 1, wherein the cemented lens is included in a lens group closest to the image display element. 5.   5. The projection apparatus according to claim 1, wherein the cemented lens is included in a lens group that does not move during focusing. 6. In the projection device according to any one of claims 1 to 5, when an axis shared by a plurality of axially symmetric lenses of the refractive optical system is an optical axis A, the following conditional expression (5): A projection apparatus having at least one resin lens PL satisfying (6) in a lens group that moves during focusing.
However,
| P40d (h) −P20d (h) | × FP <0.02 (5)
| H | <0.85 × D (6)
h: Height from the optical axis A D: Distance between the optical axis A and the point where the distance from the optical axis A is the maximum among the intersections of the reduction-side lens surface and the light beam FP: of the resin lens PL Paraxial focal length P40d (h): Power at a point of height h from the optical axis A at a temperature of 40 degrees P20d (h): Temperature at a point of height h from the optical axis A at 20 degrees The power of   7. The projection apparatus according to claim 6, wherein the resin lens PL is included in a lens group that moves during focusing. The projection apparatus according to claim 1, wherein the reflective optical element is a concave mirror and has a free-form surface . In the projection device according to any one of claims 1 to 8, satisfying the following condition (8) when multiple lenses axisymmetric of the refractive optical system and the optical axis A of the shaft that share Projection device characterized by.
BF / Y <4.0 (8)
However,
BF: Distance between the intersection of the surface including the image display element and the optical axis A and the image display element side surface vertex of the lens closest to the image display element Y: The optical axis A and the end of the image forming unit The maximum value of the distance to the part. In the projection device according to any one of claims 1 to 9, projecting apparatus wherein the projection optical system is non-telecentric optical system.

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