JP6497573B2 - 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, there has been a strong demand for high brightness even in ultra-short projection projectors. At the same time, an optical system that fully considers temperature characteristics due to heat from lamps and power supplies and heat generated by absorbing light. 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 thereof is to provide a small, high-performance projection apparatus that has a short projection distance and can achieve high brightness.

In order to achieve the above-described object, the present invention is a projection apparatus for enlarging and projecting an image displayed on an image display element on a screen, and includes a refractive optical system and at least one reflective optical element. And in the refractive optical system,
The temperature coefficient of the relative refractive index in the D line in the range of 40-60 degrees is dnT, and the Abbe number is νd.
Including at least one positive lens P1 and one negative lens N1, and the positive lens P1 and the negative lens N1
Conditional expressions (1) and (2 ') below:
−6 <dnT (1)
72 <νd (2 ′)
Satisfied ,
The positive lens P1 is disposed closer to the image display element than the aperture stop, and the negative lens N1 is disposed closer to the enlargement side than the aperture stop .

According to the present invention, there is provided a projection device for enlarging and projecting an image displayed on an image display element on a screen, including a refractive optical system and a reflective optical system having at least one reflective optical element,
In the refractive optical system,
The temperature coefficient of the relative refractive index in the D line in the range of 40-60 degrees is dnT, and the Abbe number is νd.
At least one positive lens P1 and one negative lens N1 are included, and the positive lens P1 and the negative lens N1 are
Conditional expressions (1) and (2 ') below:
−6 <dnT (1)
72 <νd (2 ′)
Satisfied ,
The positive lens P1 is disposed on the image display element side with respect to the aperture stop, and the negative lens N1 is disposed on the enlargement side with respect to the aperture stop, so that the projection distance is small, high performance, and excellent in temperature characteristics. Projection device can be provided.

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 (80 inches), and (b) shows the case where the projection size is on the near side (48 inches). 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 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 48 inches) of the light emitted from each evaluation point shown in FIG. 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 (60 inches). FIG. 5 is a diagram showing a spot diagram on a 100-inch screen corresponding to each evaluation point (each angle of view) shown in FIG. 4 in the projection apparatus according to Example 2. FIG. 5 is a diagram showing a spot diagram on an 80-inch screen corresponding to each evaluation point (each angle of view) shown in FIG. 4 in the projection apparatus according to Example 2. 5 is a diagram showing a spot diagram on a 60-inch screen corresponding to each evaluation point (each angle of view) shown in FIG. 4 in the projection apparatus according to Example 2. FIG.

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, comprising a refractive optical system and a reflective optical system having at least one reflective optical element, and the refractive optical system. In the system,
The temperature coefficient of the relative refractive index in the D line in the range of 40-60 degrees is dnT, and the Abbe number is νd.
Including at least one positive lens P1 and one negative lens N1, and the positive lens P1 and the negative lens N1
Conditional expressions (1) and (2 ') below:
−6 <dnT (1)
72 <νd (2 ′)
Satisfied ,
The positive lens P1 is disposed closer to the image display element than the aperture stop, and the negative lens N1 is disposed closer to the enlargement side than the aperture stop (corresponding to claim 1).

When the glass materials of the positive lens P1 and the negative lens N1 satisfy the above-described conditional expression (1), not only the focal length change due to temperature rise can be corrected by the two lenses, but also the curvature of field is particularly significant. The change can also be adjusted to a high degree, and in an ultra-short projection projector, a good resolution can be obtained in every corner even if the temperature rises. Temperature compensation can be performed by satisfying conditional expression (1). However, this is not sufficient for aberration correction, particularly color correction, and optical performance is not achieved until conditional expression (2 ') is satisfied at the same time. And temperature characteristics can be achieved. More preferably, the following conditional expression (1 ′) :
−5 <dnT (1 ′)
It is desirable to satisfy (corresponding to claim 2).
By the arrangement, such as pre SL, it is possible to perform the aberration correction effectively. Here, the “aperture stop” means a point where the thickness of a bundle of rays (overall light beam) from the entire image display element passing through the refractive optical system is the thinnest.

More preferably, the positive lens P1 and the negative lens N1 are preferably included in a group including a lens that has the highest temperature when displaying a white image (corresponding to claim 3). By disposing the lens in the lens group, a projection optical system with good temperature characteristics can be obtained.
More preferably, the positive lens P1 and the negative lens N1 are preferably included in a group closest to the image display element, for example, a first lens group (corresponding to claim 4). By disposing the lens in the lens group, a projection optical system with good temperature characteristics can be obtained.
More preferably, the positive lens P1 and the negative lens N1 are preferably included in a group that does not move during focusing (corresponding to claim 5). This is because good temperature characteristics can be obtained even at each image size.
More preferably, the refractive optical system may include a resin lens, and the resin lens is preferably included in a group including a lens having the lowest temperature when displaying a white image (corresponding to claim 6). ). With the arrangement as described above, it is possible to effectively suppress curvature of field due to temperature change.

More preferably, the reflecting optical element is a concave mirror and preferably has a free-form surface (corresponding to claim 7). By using a free-form surface, it is possible to effectively correct field curvature.
More preferably, the reflecting optical element is a concave mirror, and a ratio of the distance from the intersection of the concave mirror and the optical axis of the refractive optical system to the screen / the ratio of the screen width is TR, and the following conditional expression (3):
TR <0.30 (3)
It is desirable to satisfy (corresponding to claim 8).
By satisfying the above conditional expression, a projection device having a very short projection distance can be obtained. More preferably, the following conditional expression (3 ′):
TR <0.25 (3 ')
It is desirable to satisfy.
More preferably, the distance between the intersection of the surface including the image display element and the optical axis and the image display element side surface vertex of the lens closest to the image display element is BF, and the optical axis and the end of the image forming unit Y is the maximum distance between
When an axis shared by a plurality of axially symmetric lenses of the refractive optical system is an optical axis, the following conditional expression (4):
BF / Y <4.0 (4)
It is desirable to satisfy (corresponding to claim 9).

By satisfying the conditional expression (4), the projection optical system can be further downsized. More preferably, the following conditional expression (4 ′):
BY / Y <3.5 (4 ′)
It is desirable to satisfy.
More preferably, the projection optical system including the refractive optical system and the reflective optical system is a non-telecentric optical system (corresponding to claim 10). Using a non-telecentric optical system is advantageous for downsizing.
With the configuration as described above, the projection optical system of the present invention can provide a projection device that has a very short projection distance, can achieve high brightness, is small, has high performance, and has good temperature characteristics.
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 (80 inches), and (b) shows the case where the projection size is on the near side (48 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”, and the like, which is indicated by reference numeral LV Is a “part forming an 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 position (aperture stop). Moreover, SC in FIG. 1 shows a screen.
In FIG. 1, the optical path diagram in the case of 48 inches in which the front ball is extended most is shown. As shown in FIG. 1, an axis shared by a plurality of axisymmetric lenses is an axis A, a direction parallel to the axis A is a Z-axis direction, and a plane including a light beam emitted from the center of the image display element and passing through the center of the stop S. In the figure, an axis perpendicular to the axis A is defined as a Y axis, and an axis perpendicular to the axes A and Y is defined as an 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 of the first embodiment, a glass material that satisfies the conditional expressions (1) and (2) for the positive lens closest to the image display element, the positive lens that sandwiches the stop, and the negative lens (for example, By using OHARA S-FPM3 nd: 1.53775 νd: 74.7031 DnT: -4.4), the fluctuation of the focal length and the thermal expansion of the mechanical holding unit are balanced. 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 reflection mirror. 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-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 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, the angle is not perpendicular to the axis A, but the angle is arbitrary, and the angle may be perpendicular to the 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 (5) 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 (6)

  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, a light beam that is emitted from the center of the image display element and passes through the center of the stop, which is in the normal direction of the image forming unit and is parallel to the axis A that is the axis shared by the axisymmetric lens. Among the in-plane axes including the axis A, the axis perpendicular to the axis A is the Y axis, the axis A, the axis perpendicular to the Y axis is the X axis, and in FIG. 1, the clockwise rotation direction is the + α direction.
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 (80 inches) side to the short distance (48 inches) side. Then, the positive fourth lens group G4 moves to the enlargement side.

  The first lens group G1 has, in order from the image forming unit LV side, a first lens L1 composed of 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 magnifying side. A second lens L2 made of a positive meniscus lens, a third lens L3 made of a negative meniscus lens having a convex surface facing the image forming portion, and a fourth lens L4 made of a negative meniscus lens having a convex surface facing the image forming portion. A cemented lens with a fifth lens L5 made of a positive meniscus lens having a convex surface facing the image forming unit, an aperture stop S, a sixth lens L6 made of a negative meniscus lens with a convex surface facing the magnification side, and the magnification side A seventh lens L7 composed of a double-sided aspherical biconvex lens with a convex surface having a larger curvature than the image forming unit side, and an eighth lens L8 composed of a negative meniscus lens having a convex surface directed to the image forming unit side. The ninth lens L9 is a biconvex lens having a convex surface having a larger curvature than the image forming unit on the enlargement side, and the tenth lens L10 is a biconcave lens having a concave surface having a larger curvature than the enlargement side on the image forming unit side. A cemented lens and an eleventh lens L11 composed of a biconvex lens having a convex surface having a larger curvature than the image forming unit side on the enlargement side are configured. The second lens group G2 is composed of a single twelfth lens L12 made of a positive meniscus lens having a convex surface facing the image forming unit. The third lens group G3 includes a thirteenth lens L13 made of a biconcave lens having a concave surface having a larger curvature than the image forming unit side on the magnifying side, a fourteenth lens L14 made of a plano-concave lens whose magnifying side is a plane, and an image forming unit And a fifteenth lens L15 made of a double-sided aspheric negative meniscus lens having a convex surface facing the side. The fourth lens group G4 includes a sixteenth lens L16 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 the folding plane mirror 12 (surface 34) and the free-form curved concave mirror 13 (surface 35) are installed on the enlargement side.
The first lens L1 and the fifth lens L5 are referred to as a positive lens P1, and the seventh lens L7 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 fifteenth surface, the sixteenth surface, the thirty-third surface, the thirty-second surface, and the thirty-third surface marked with “*” are shown. The parameters of each aspheric surface in the equation (5) 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 23 and the surface 24. The variable distance DB is a distance between the second lens group G2 and the third lens group G3, that is, a variable distance between the surface 25 and the surface 26. The variable interval DC is the interval between the third lens group G3 and the fourth lens group G4, that is, the variable interval between the surface 31 and the surface 32. 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. In this way, by changing the enlargement ratio, the diagonal size of the projected image is adjusted to a focus size of 48 inches, 60 inches, and 80 inches according to 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 these surface intervals DA to DE change as shown in Table 3 below with respect to the projected image diagonal size of 80, 60, and 48 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 (6).

  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: 5.31 mm
BF / Y: 2.61
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.

In addition, spot diagrams corresponding to the respective angles of view shown in FIG. 4 are shown in FIGS. Each of these spot diagrams shows imaging characteristics (mm) on the screen surface for wavelengths of 625 nm (red), 550 nm (green), and 425 nm (blue). It can be seen that a good image is formed.
Table 7 shows the focal lengths of the first lens unit and the entire system when the room temperature (20 degrees) and the temperature rise by 20 degrees.

It can be seen that the fluctuation of the focal length when the temperature changes can be suppressed.
In the case of Example 1, the values corresponding to the conditional expressions (1) to (4) are as follows and satisfy the conditional expressions (1) to (4), respectively.
Conditional expression (1) dnT = −4.4
Conditional expression (2) νd = 74.7031
Conditional expression (3) TR = 0.219 to 0.232
Conditional expression (4) BF / Y = 2.61

Next, a projection apparatus according to Example 2 will be described with reference to FIG.
As shown in FIG. 8, the axis that is in the normal direction of the image forming unit and is parallel to the axis A, which is the axis shared by the axisymmetric lens, is emitted from the center of the image display element. Of the axes in the plane including the light beam, the axis perpendicular to the axis A is the Y axis, the axis A is perpendicular to the Y axis, and the axis perpendicular to the Y axis is the X axis. In FIG.
FIG. 9 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. As shown in FIG. 8, a free-form curved concave mirror 13 is provided on the most enlarged side, and focusing with respect to fluctuations in projection distance is positive when focusing from a long distance (100 inches) side to a short distance (60 inches) side. The second lens group G2 and the negative third lens group G3 move to the image forming unit side, and 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 fifth lens L5 composed of a cemented lens with L4, an aperture stop S, a negative meniscus lens having a convex surface facing the enlargement side, and a biconvex lens composed of a convex surface having a larger curvature than the image forming unit side on the magnification side. A sixth lens L6, a seventh lens L7 composed of a double-sided aspheric negative meniscus lens having a convex surface facing the image forming unit, and a biconvex lens having a convex surface having a larger curvature than the image forming surface on the enlargement side A cemented lens composed of an eighth lens L8 and a ninth lens L9 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 convex surface having a larger curvature than the image forming unit side on the magnification side And a tenth lens L10 made of a 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 negative meniscus lens having a convex surface facing the image forming portion, and a thirteenth lens L13 made of a biconcave lens having a concave surface having a larger curvature on the image forming portion side than the magnifying side. And a fourteenth lens L14 composed of a double-sided aspheric negative meniscus lens having a convex surface facing the image forming unit. The fourth lens group G4 is composed of a fifteenth lens L15 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 the folding plane mirror 12 (surface 32) and the free-form curved concave mirror 13 (surface 33) are installed on the enlargement side.
The third lens L3 is referred to as a positive lens P1, and the fifth lens L5 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 fifteenth surface, the sixteenth surface, the twenty-eighth surface, the twenty-ninth surface, the thirty-third surface, and the thirty-first surface marked with “*” are shown. The parameters of each aspheric surface in the equation (5) 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 interval DC is the interval between the third lens group G3 and the fourth lens group G4, that is, the variable interval between the surface 29 and the surface 30.
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.
As described above, in the projection optical system, when the focusing with respect to the variation in the projection distance is performed from the long distance to the short distance side, the second lens group G2 and the third lens group G3 move to the image forming unit side in FIG. 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 to the projection size up to 60 inches, 80 inches, and 100 inches according to 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 10 as “variable DA”, “variable DB”, “variable DC”, “variable DD”, “variable”. DE ”, and these surface intervals DA to DE change as shown in Table 10 below with respect to the projected image diagonal size of 60, 80, and 100 inches.

  The free-form surface shape is given by giving 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 the following Table 11, and X is free in the optical axis direction. As the amount of curved surface, the shape is specified by the above equation (6).

  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: 2.61
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.

Further, spot diagrams corresponding to the respective angles of view shown in FIG. 4 are shown in FIGS. Each of these spot diagrams shows imaging characteristics (mm) on the screen surface for wavelengths of 625 nm (red), 550 nm (green), and 425 nm (blue). It can be seen that a good image is formed.
That is, in the projection apparatus according to the second embodiment, the spot diagram on the screen corresponding to each angle of view (evaluation point) shown in FIG. 4 is shown in FIG. 10 for 100 inches, and in the case of 80 inches. 11 and 60 inches are as shown in FIG.
As can be seen from FIG. 10 to FIG. 12, it can be seen that a good image is formed.
Next, Table 14 shows the focal length of the entire system and the focal length of the first lens group at room temperature (20 degrees) and 40 degrees when the temperature rises by 20 degrees.

It can be seen that the fluctuation of the focal length when the temperature changes can be suppressed.
In the case of Example 2, values corresponding to the conditional expressions (1) to (4) are as follows and satisfy the conditional expressions (1) to (4), respectively.
Conditional expression (1) dnT = −4.4
Conditional expression (2) νd = 74.7031
Conditional expression (3) TR = 0.215 to 0.226
Conditional expression (4) BF / Y = 2.61
According to the projection device specified by 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 and has high performance and excellent temperature characteristics. An image projection device with an ultra-short projection distance can be obtained. 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-L16 1st lens-16th lens LV Image formation part N1 Negative lens P1 Positive lens

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 at least one reflective optical element, wherein the refractive optical system In the system,
The temperature coefficient of the relative refractive index in the D line in the range of 40-60 degrees is dnT, and the Abbe number is νd.
The positive lens P1 and the negative lens N1 each include at least one lens, and the positive lens P1 and the negative lens N1
Conditional expressions (1) and (2 ') below:
−6 <dnT (1)
72 <νd (2 ′)
Satisfied,
The projection apparatus, wherein the positive lens P1 is disposed closer to the image display element than the aperture stop, and the negative lens N1 is disposed closer to the enlargement side than the aperture stop. 2. The projection apparatus according to claim 1, wherein the positive lens P <b> 1 and the negative lens N <b> 1 further satisfy the following conditional expression (1 ′):
−5 <dnT (1 ′)
A projection device characterized by satisfying   3. The projection apparatus according to claim 1, wherein the positive lens P <b> 1 and the negative lens N <b> 1 are included in a group including a lens that has the highest temperature when displaying a white image.   4. The projection apparatus according to claim 1, wherein the positive lens P <b> 1 and the negative lens N <b> 1 are included in a group closest to the image display element. 5.   5. The projection apparatus according to claim 1, wherein the positive lens P <b> 1 and the negative lens N <b> 1 are included in a group that does not move during focusing.   6. The projection apparatus according to claim 1, wherein the refractive optical system includes a resin lens, and the resin lens is included in a group having the lowest temperature when displaying a white image. Projection device.   The projection apparatus according to claim 1, wherein the reflective optical element is a concave mirror and has a free-form surface. 8. The projection apparatus according to claim 1, wherein the reflective optical element is a concave mirror, and a distance from the intersection of the concave mirror and the optical axis of the refractive optical system to the screen / screen width. The following conditional expression (3):
TR <0.30 (3)
A projection system including the screen. 9. The projection device according to claim 1, wherein a distance between an intersection between a surface including the image display element and an optical axis and a vertex of the image display element side surface of the lens closest to the image display element. Is BF, Y is the maximum distance between the optical axis and the end of the image forming unit,
When an axis shared by a plurality of axially symmetric lenses of the refractive optical system is an optical axis, the following conditional expression (4):
BF / Y <4.0 (4)
The projection device characterized by satisfying.   10. The projection apparatus according to claim 1, wherein the projection optical system including the refractive optical system and the reflective optical system is a non-telecentric optical system. 11.

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