JP2011158595A - Projection optical system and projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection optical system with no movement of a lens group at zooming, excellent in impact resistance, and suitable for a compact projector, for instance, and a projector. <P>SOLUTION: In the projection optical system that uses at least one lens with variable refractive power, intervals between the respective lenses are fixed, and the refractive power of the lens with variable refractive power is changed to change the size of an image on a display element surface projected on a screen surface, thereby requiring no movable part for zooming. The projector to which the projection optical system is mounted can be reduced in size and weight. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a projection optical system such as a projector, and more particularly to a projection optical system including a zoom mechanism suitable for projecting with a dimension changed on a screen and a projector using the same.

  Conventionally, as projection optical systems such as projectors, various projection optical systems having a zoom mechanism suitable for projecting with different dimensions on a screen have been proposed. In such a projector, an actuator or the like is used during zooming, and the size of the projection image is changed by moving the lens group on the enlargement projection side, the intermediate side, or the display element surface side in the optical axis direction.

  On the other hand, in recent years, attempts have been made to reduce the size of the projector, but the mechanism for moving the lens group in the optical axis direction is an obstacle to downsizing the projector.

  When a brighter enlarged projection image is obtained, blur of the enlarged projection image can be visually confirmed by zooming. Therefore, the focal length is adjusted by providing the projection optical system with a focus function. It may lead to an increase in size.

  For example, in the projection optical system described in Patent Document 1, zoom, focus, or zoom and focus are performed by further moving the lens group using a variable focus lens.

  Furthermore, in the projection optical system described in Patent Document 2, when zooming from the wide-angle end to the telephoto end, the second lens group G2 to the fifth lens group G5 are moved to the enlarged projection side, respectively.

  In the projection optical system 3 described in the patent document, when zooming from the wide-angle end to the telephoto end, the first lens unit L1 is moved to the reduction side and the second lens unit L2 is moved to the enlargement projection side. .

JP 2006-053275 A JP 2009-128684 A JP 2003-344663 A

  However, in the projection optical system described in Patent Document 1, a good projection image can be obtained by moving a lens group other than the variable focus lens, but the mechanism is complicated and the apparatus is enlarged. It was.

  Further, in the projection optical systems described in Patent Documents 2 and 3, the dimensions of the projected image are changed by moving the lens group in the optical axis direction using an actuator or the like during zooming. The length was required and the total length was long.

  In particular, in the projection optical system described in Patent Document 2, since the four lens groups are moved in different motions, there are more mechanisms for moving the lens groups such as actuators, which increases the size of the apparatus itself. It is expected to invite. Furthermore, since the strength of the movable part is weakened by the movement of the lens group, the impact resistance performance is also lowered.

  The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a projection optical system and a projector that have no movement of a lens group at the time of zooming, have high impact resistance, and are suitable for, for example, a small projector. To do.

  The projection optical system according to claim 1 is a projection optical system composed of a plurality of lenses for enlarging and projecting an image of the display element surface on the screen surface, and uses at least one lens having a variable refractive power, and each lens. , And the size of the image of the display element surface projected onto the screen surface is changed by changing the refractive power of the lens having the variable refractive power.

  According to the present invention, in a projection optical system, at least one lens has a variable refractive power, each lens is fixed, and the refractive power of the lens having a variable refractive power is changed to change the display element projected onto the screen surface. Since the dimensions of the image on the surface are changed, a movable part is not required for zooming, and this makes it possible to reduce the size and weight of the projector equipped with the projection optical system.

  The projection optical system according to claim 2 is a projection optical system for enlarging and projecting an image of the display element surface onto the screen surface, and has at least a first lens having a variable refractive power and a positive refractive power from the enlarged projection surface side. A second lens having a negative refracting power, and a fourth lens having a positive refracting power, and the first lens to the fourth lens have fixed positions in the optical axis direction, The lens having a variable refractive power is characterized by changing a size of an image of a display element surface projected on a screen surface.

  A projection optical system having a zoom function according to the present invention includes a first lens having at least variable refractive power, a second lens having positive refractive power, and a third lens having negative refractive power from the enlarged projection plane side. Since the lens is composed of a fourth lens having a positive refractive power and has a simple lens structure using a so-called triplet, it is possible to achieve downsizing and cost reduction. Furthermore, since the optical length can be shortened, it is possible to improve the resolution and to obtain high optical performance with consideration of axial chromatic aberration, coma aberration and distortion. Further, by fixing each lens, it is possible to prevent the projection optical system from being enlarged due to the movement of the lens group during zooming, and the apparatus can be miniaturized. In addition, since the first lens to the fourth lens have fixed positions in the optical axis direction, a movable part is not required for zooming, thereby reducing the size and size of a projector equipped with the projection optical system. Weight reduction can be achieved.

  A projection optical system according to a third aspect of the present invention is the projection optical system according to the first or second aspect, wherein the projection optical system has an F number greater than 8.

  In the projection optical system, by making the F number larger than 8, it is possible to make the range of the enlarged projection image blurred at the time of zooming, so that the focusing mechanism is omitted. This makes it possible to further reduce the size of the projector.

  A projection optical system according to a fourth aspect of the present invention is the projection optical system according to any one of the first to third aspects, wherein the lens having a variable refractive power includes a second liquid that does not mix with the first liquid and is sealed in a container. It is an optical element capable of changing the shape of the boundary surface between the first liquid and the second liquid by changing the physical quantity applied to the container.

  The lens having a variable refractive power includes an electrode provided on a member that forms an inner wall surface, and an insulating means provided between the first liquid and the second liquid, and includes a conductive liquid and an electrode. It is preferable to apply a voltage between them. For example, one of the first liquid and the second liquid is inductive and the other is insulative. Further, the first liquid and the second liquid have substantially the same density, and the first liquid and the second liquid are configured to have different refractive indexes. As a result, the boundary surface shape between the first liquid and the second liquid can be changed, and the display element surface image can be scaled without moving the lens. However, the lens having a variable refractive power is not limited to a lens using such a liquid. For example, an optical element that changes the refractive power by distorting the lens may be used.

According to a fifth aspect of the present invention, in the projection optical system according to any one of the first to fourth aspects, the following conditional expression is satisfied in the projection optical system.
1.6 <fB _1-4w / f _w <7.8 (1)
However,
fB _1-4w : Back focus of the composite system of the first lens to the fourth lens at the wide angle end f _w : Focal length of the projection optical system at the wide angle end

  If the value of conditional expression (1) becomes smaller than the lower limit of 1.6, the air space between the fourth lens and the display element becomes too small, for example, it becomes impossible to insert a reflective optical element. . On the other hand, when the value of the conditional expression (1) is larger than the upper limit of 7.8, it is advantageous for securing an air space between the fourth lens and the display element. The focal length becomes too small and the aberration increases. Therefore, by satisfying the condition of the conditional expression (1), the back focus in the synthesis system from the first lens to the fourth lens is set to a required size, and while maintaining good optical performance, It is possible to secure an air space in which a reflective optical element can be inserted between the display elements.

According to a sixth aspect of the present invention, in the projection optical system according to any one of the first to fifth aspects, the following conditional expression is satisfied in the projection optical system.
−6.0 <f _1w / f _w <−3.1 (2)
However,
f _1w : Focal length of the lens with variable refractive power at the wide angle end f _w : Focal length of the projection optical system at the wide angle end

  Further, if the value of conditional expression (2) becomes smaller than the lower limit −6.0, the power of the first lens becomes small, and the magnification after the second lens also becomes small. Will become larger. On the other hand, if the value of conditional expression (2) exceeds the upper limit of -3.1, the power of the first lens increases, and various aberrations such as spherical aberration increase. By satisfying this conditional expression (2), it is possible to maintain an appropriate total length and good optical performance while appropriately securing and changing the refractive power of the first lens.

A projection optical system according to a seventh aspect of the present invention is the projection optical system according to any one of the first to sixth aspects, wherein the fourth lens satisfies the following conditional expression.
−8.1 <(r ₄₂ + r ₄₁ ) / (r ₄₂ −r ₄₁ ) <− 1.0 (3)
However,
r ₄₂ : radius of curvature of the enlarged projection side lens surface of the fourth lens r ₄₁ : radius of curvature of the display element side lens surface of the fourth lens

  If the value of the conditional expression (3) becomes smaller than the lower limit −8.1, the principal point of the fourth lens will go too far to the image side, and thereby the synthesis system of the third lens and the fourth lens. As the power of the lens increases, coma and astigmatism increase. On the other hand, if the value of conditional expression (3) becomes larger than the upper limit of −1.0, the principal point of the fourth lens goes too far to the object side, and thereby the third lens and the fourth lens. The power of the synthesis system becomes weaker and the overall length becomes longer. By satisfying this conditional expression (3), it is possible to obtain appropriate refractive power and good optical performance of the fourth lens for ensuring the entire length necessary for miniaturization while maintaining the shape of the fourth lens appropriately. It is possible.

A projection optical system according to an eighth aspect of the present invention is the projection optical system according to any one of the first to seventh aspects, wherein the fourth lens satisfies the following conditional expression.
0.4 <f ₄ / f _w <2.2 (4)
However,
f ₄ : focal length of the fourth lens f _w : focal length of the projection optical system at the wide angle end

  If the value of conditional expression (4) exceeds the upper limit of 2.2, the power of the fourth lens becomes too weak and the back focus becomes too large, thereby reducing the compactness. On the other hand, if the value of conditional expression (4) becomes smaller than the lower limit of 0.4, sufficient back focus cannot be secured, telecentricity tends to be lost, and correction of off-axis aberrations becomes difficult. By satisfying the condition of the conditional expression (4), it is possible to specify an appropriate refractive power of the fourth lens for ensuring telecentricity.

  According to a ninth aspect of the present invention, there is provided the projection optical system according to any one of the first to eighth aspects, further comprising a fifth lens having a positive refractive power.

  In the projection optical system of the present invention, a fifth lens having a positive refractive power can be inserted. As a result, it is possible to ensure good telecentricity on the reduction side.

  A projection optical system according to a tenth aspect is characterized in that, in the invention according to any one of the first to eighth aspects, the projection optical system includes a reflective optical element having a curvature at a position closest to the display element surface. And

  In a general projection optical system, when light is incident on the display element at an angle, the color changes due to the polarization characteristics, and the reflectance deteriorates. In order to prevent this, good telecentricity on the reduction side is necessary. Therefore, in the projection optical system according to the present invention, a method of combining a triplet and a reflective optical element having a curvature on the display element surface side, a reflection having no curvature by inserting a lens having a positive refractive power on the display element surface side of the triplet. There is a method of combining optical elements.

  In the projection optical system of the present invention, by inserting an optical element with a curvature, it is possible to ensure good telecentricity on the reduction side and to keep the entire length short.

  A projector according to an eleventh aspect uses the projection optical system according to any one of the first to tenth aspects.

  According to the present invention, it is possible to provide a projection optical system and a projector that do not move the lens group during zooming, have high impact resistance, and are suitable for, for example, a small projector.

It is a schematic block diagram of the projector concerning this Embodiment. It is an expanded sectional view of the 1st lens L1. FIG. 3 is a sectional view in the optical axis direction of the projection optical system of Example 1 at the wide angle end. FIG. 4 is an aberration diagram of Example 1 (spherical aberration (a), astigmatism (b), distortion (c)) at the wide-angle end. FIG. 2 is a sectional view in the optical axis direction of the projection optical system of Example 1 in the middle. FIG. 4 is an aberration diagram (spherical aberration (a), astigmatism (b), distortion aberration (c)) of Example 1 in the middle. FIG. 3 is a sectional view in the optical axis direction of the projection optical system of Example 1 at the telephoto end. FIG. 6 is an aberration diagram of Example 1 (spherical aberration (a), astigmatism (b), distortion (c)) at the telephoto end. FIG. 6 is a sectional view in the optical axis direction of the projection optical system of Example 2 at the wide angle end. FIG. 6 is an aberration diagram (spherical aberration (a), astigmatism (b), distortion (c)) of Example 2 at the wide-angle end. FIG. 6 is a sectional view in the optical axis direction of the projection optical system of Example 2 in the middle. FIG. 6 is an aberration diagram (spherical aberration (a), astigmatism (b), distortion (c)) in Example 2 in the middle. It is an optical axis direction sectional view of the projection optical system of Example 2 at the telephoto end. FIG. 6 is an aberration diagram of Example 2 (spherical aberration (a), astigmatism (b), distortion (c)) at the telephoto end. FIG. 10 is a cross-sectional view in the optical axis direction of the projection optical system of Example 3 at the wide angle end. FIG. 6 is an aberration diagram of Example 3 at the wide-angle end (spherical aberration (a), astigmatism (b), distortion (c)). It is sectional drawing of the optical axis direction of the projection optical system of Example 3 in the middle. FIG. 6 is an aberration diagram (spherical aberration (a), astigmatism (b), distortion (c)) in Example 3 in the middle. It is an optical axis direction sectional view of the projection optical system of Example 3 at the telephoto end. FIG. 6 is an aberration diagram of Example 3 at the telephoto end (spherical aberration (a), astigmatism (b), distortion (c)). FIG. 10 is a cross-sectional view in the optical axis direction of the projection optical system of Example 4 at the wide-angle end. FIG. 6 is an aberration diagram of Example 4 (spherical aberration (a), astigmatism (b), distortion (c)) at the wide-angle end. It is sectional drawing of the optical axis direction of the projection optical system of Example 4 in the middle. FIG. 8 is an aberration diagram (spherical aberration (a), astigmatism (b), distortion (c)) in Example 4 in the middle. It is an optical axis direction sectional view of the projection optical system of Example 4 at the telephoto end. FIG. 6 is an aberration diagram of Example 4 (spherical aberration (a), astigmatism (b), distortion (c)) at the telephoto end.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a projector PJT according to the present embodiment.

  In the projector PJT shown in FIG. 1, the illumination light radiated from the light emitting part of the light source LD, which is a semiconductor laser (or LED), is converted into parallel light by the condenser lens COL, and then reflected optically as a prism. The light is transmitted through the transmitting / reflecting surface TRP of the element PZ and separated by polarization, and the display element surface DE is irradiated while maintaining telecentricity. The light beam reflected on the display element surface DE is modulated according to the image on the display element surface DE, enters the reflective optical element PZ, is transmitted through the transmission / reflection surface TRP, and has a positive refractive power. After passing through the fourth lens L4 having, the third lens L3 having negative refractive power, and the second lens L2 having positive refractive power, it passes through the first lens L1 having variable refractive power, and the image of the display element surface DE is displayed. The image is enlarged and projected on a projection surface (not shown) on the screen. Here, by changing the shape of the boundary surface of the first lens L1 having a variable refractive power, the lenses L1 to L4 are fixed to a lens frame (not shown), and the size of the image on the display element surface is changed without being moved. Can be made.

  As a modification of the present embodiment, a fifth lens L5 having a positive refractive power can be fixedly disposed between the fourth lens L4 having a positive refractive power and the reflective optical element PZ.

  FIG. 2 is a schematic configuration diagram of the first lens L1 and its driving unit. In FIG. 2, the enlarged projection plane is on the right side. Reference numeral 40 denotes a lower container formed of a nonconductor. A first recess 41 is formed in the peripheral portion of the bottom surface (the right inner surface in the figure) of the lower container 40, and the first sealing plate 2 is disposed on the inner diameter side (center side) than this. The 2nd recessed part 42 to hold | maintain is formed. The first sealing plate (member for sealing the liquid) 2 is made of transparent acrylic or glass.

  A second electrode ring 43 is provided on the entire inner periphery of the peripheral wall of the lower container 40, and the surface of the second electrode ring 43 is made of an acrylic resin or the like that also covers the electrode end face 43a. An insulating layer 44 is formed in close contact.

  Here, the peripheral wall portion of the lower container 40 is inclined with respect to the optical axis X so that the right end side is closer to the optical axis X than the left end side in the drawing. For this reason, the first electrode ring 43 and the insulating layer 44 are both inclined with respect to the optical axis X.

  Further, the thickness of the insulating layer 44 gradually increases toward the right in the figure. Further, the water repellent layer 11 is formed by applying a water repellent treatment agent below the entire inner circumference of the insulating layer 44. Further, a hydrophilic treatment agent is applied to the left side of the entire inner circumference of the insulating layer 44 to form the hydrophilic layer 12.

  Reference numeral 50 denotes an upper container formed of a non-conductor, and holds a second sealing plate (member for sealing liquid) 6 formed of transparent acrylic or glass on the inner diameter side thereof. A sheet-like first electrode ring 51 is formed in close contact with the right end surface of the peripheral portion of the upper container 50.

  An insulating layer 52 is formed in close contact with the surface of the first electrode ring 51. The insulating layer 52 is insulated so as to have an exposed portion 51a for contacting the first liquid 21 described later and applying a voltage thereto. The layer 52 is formed so as to cover only the outer edge side of the first electrode ring 51.

  Then, the peripheral wall portion of the lower container 40 and the upper container 50 are sealed in a liquid-tight manner, thereby being surrounded by the lower container 40, the upper container 50, the first sealing plate 2, and the second sealing plate 6. A container having a predetermined volume of liquid chamber is formed.

  This container has an axisymmetric shape with respect to the optical axis X. The liquid chamber is filled with two types of liquids as follows.

  First, in the state where the optical axis X of the lower container 40 to which the first sealing plate 2 is attached is oriented in the vertical direction, the upper surface of the first sealing plate 2 that is the bottom surface of the liquid chamber and the peripheral side of the lower container 40 The second liquid 22 is dripped onto the bottom surface of these layers (which correspond to the interface-facing surfaces) by an amount so that the height of the liquid column is intermediate between the water-repellent film 11 on the peripheral wall portion.

  The second liquid 22 is a colorless and transparent silicone oil having a specific gravity of 1.06 and a refractive index of 1.489 at room temperature. Subsequently, the remaining space in the liquid chamber is filled with the first liquid 21. The first liquid 21 is an electrolyte having a specific gravity of 1.06 and a refractive index of 1.400 at room temperature (electrically conductive or polar), in which water and ethyl alcohol are mixed at a predetermined ratio and a predetermined amount of sodium chloride is added. Liquid). The zoom ratio can be increased by increasing the refractive power difference between the first and second liquids 21 and 22.

  That is, as the first and second liquids 21 and 22, liquids having the same specific gravity, different refractive indexes, and incompatible with each other (insoluble) are selected. And both the liquids 21 and 22 form the interface 24, and each exists independently, without mixing.

  The shape of the interface 24 is determined by the balance of the three interfacial tensions acting on the inner surface of the liquid chamber (container), the three substances of the first liquid 21 and the second liquid 22, that is, the outer edge of the interface 24. Then, two types of liquids are sealed by attaching the upper container 50 to which the second sealing plate 6 is attached to the lower container 40.

  Reference numeral 31 denotes a power supply circuit connected to the first electrode ring 25 and the second electrode ring 3.

  Two amplifiers (not shown) of the power feeding circuit 31 are respectively connected to the first electrode ring 51 and the second electrode ring 43 along the right end surface of the upper container 50 in the direction orthogonal to the optical axis 51b, 43b.

  In the above configuration, when a voltage is applied to the first liquid 21 via the first electrode ring 51 and the second electrode ring 43, the interface 24 is deformed by a so-called electrowetting effect.

  Next, the deformation of the interface 24 in the first lens L1 and the optical action caused by this deformation will be described.

  First, when no voltage is applied to the first liquid 21, as shown in FIG. 2, the shape of the interface 24 is such that the interface tension between the two liquids 21 and 22, the first liquid 21 and the insulating layer 44. It is determined by the interfacial tension between the water repellent film 11 or the hydrophilic film 12, the interfacial tension between the second liquid 22 and the water repellent film 11 or the hydrophilic film 12 on the insulating layer 44, and the volume of the second liquid 22.

  On the other hand, when a voltage is applied to the first liquid 21 from the power supply circuit 31, the interfacial tension between the first liquid 21 and the hydrophilic film 12 decreases due to the electrowetting effect, and the first liquid 21 becomes the hydrophilic film 12. Over the boundary between the water repellent film 11 and the water repellent film 11. As a result, the height of the second liquid 22 on the optical axis increases.

  In this way, the application of voltage to the first liquid 21 through the first and second electrode rings 51 and 43 changes the balance of the interface tension between the two liquids, and the interface 24 between the two liquids 21 and 22 changes. The shape changes. In this way, an optical element that can freely change the shape of the interface 24 by controlling the voltage of the power feeding circuit 31 can be realized.

  Further, since the first and second liquids 21 and 22 have different refractive indexes, optical power (1 / f: f is a focal length) as an optical lens is given, that is, the first The focal length of the lens L1 changes due to the shape change of the interface 24. Thereby, zooming of the projection optical system can be performed continuously. In addition, if the first and second liquids 21 and 22 have different refractive index differences, a large power change can be obtained. Even if the refractive index difference is small, a plurality of such first lenses L1 are provided. If the lens groups are connected in series, a large zoom ratio can be obtained.

Examples of a projection optical system suitable for the above projector will be described below. Symbols used in each example are as follows.
f: Focal length of the entire projection optical system fB: Back focus Fno: F number R: Radius of curvature D: Axial distance Nd: Refractive index νd of lens material with respect to d-line: Abbe number of lens material

  In each embodiment, the surface described with “*” after each surface number is a surface having an aspheric shape, and the shape of the aspheric surface has the vertex of the surface as the origin and the X axis in the optical axis direction. The height in the direction perpendicular to the optical axis is represented by the following “Equation 1”.

ただし、
Ａｉ：ｉ次の非球面係数
Ｒ：曲率半径
Ｋ：円錐定数である。

However,
Ai: i-th order aspheric coefficient R: radius of curvature K: conic constant.

  In the following (including the lens data in the table), a power of 10 (for example, 2.5 × 10-02) is represented using E (for example, 2.5E-02). Further, the surface numbers of the lens data are given in order with the enlarged projection surface side of the first lens as one surface. In addition, the unit of the numerical value showing the length as described in an Example shall be mm.

Example 1
Lens data of the projection optical system of Example 1 is shown in the following (Table 1).

(Table 1)
Example 1
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
Screen ∞ 2000.00
1 ∞ 0.30 1.52300 54.5 1.93
2 ∞ 0.50 1.48900 60.6 1.83
3 R1 0.70 1.40000 39.8 1.00
4 ∞ 0.55 1.52300 54.5 2.00
5 ∞ 1.00 1.22
6 * 12.358 1.00 1.80000 28.5 0.66
7 * -4.047 0.00 0.39
8 (Aperture) ∞ 1.00 0.33
9 * -1.688 0.70 1.75000 25.0 0.69
10 * 6.308 0.50 1.20
11 * -9.395 1.00 1.75000 57.0 1.84
12 * -2.319 0.50 1.95
13 ∞ 14.00 1.80610 40.7 2.45
14 -11.930 5.14
Display element ∞

Aspheric coefficient
6th surface K = 0.00000E + 00
A4 = -0.41856E-01
A6 = -0.23244E-01
A8 = -0.51745E-02
Surface 7 K = 0.00000E + 00
A4 = -0.74537E-01
A6 = -0.57029E-01
A8 = 0.19114E + 00
8th surface K = 0.00000E + 00
A4 = -0.17298E + 00
A6 = -0.11345E + 00
A8 = 0.10959E + 00
9th face K = 0.00000E + 00
A4 = -0.70727E-01
A6 = 0.27677E-01
A8 = -0.50679E-02
10th surface K = 0.00000E + 00
A4 = 0.16745E-01
A6 = -0.67745E-03
A8 = 0.62338E-05
11th surface K = 0.00000E + 00
A4 = 0.79285E-02
A6 = 0.28058E-03
A8 = 0.96437E-03

Focal length at each position, distance between lens final surface and paraxial imaging point at screen distance of this embodiment (L)
F number
f L Fno
Wide 9.33 4.59 15.00
Middle 9.80 1.94 14.99
Tele 9.97 0.95 14.99

Curvature radius, angle of view of each position, focal length of the first lens, total lens length
R1 Angle of view ω Focal length of the first lens Total lens length
Wide 2.96 60.40 -33.43 9.69
Middle ∞ 56.98 0.00 9.69
Tele -8.54 55.44 96.45 9.69

Zoom ratio, image height
Zoom ratio Image height
1.07 5.15

  3 is a cross-sectional view of the projection optical system of Example 1 in the wide-angle end state, FIG. 5 is a cross-sectional view of the projection optical system of Example 1 in the intermediate state, and FIG. FIG. 2 is a cross-sectional view of the projection optical system of Example 1 in the end state, but wiring and the like to the first lens L1 are omitted. The projection optical system of Example 1 includes a first lens L1 having a variable refractive power, a second lens L2 having a positive refractive power, and a third lens L3 having a negative refractive power from the enlarged projection plane side (left side). And a fourth lens L4 having a positive refractive power, and a reflective optical element PZ, both of which have a fixed position in the optical axis direction, and zooming changes the voltage applied to the first lens L1. Done in In the figure, DE is a display element screen, and only the optical path from the display element screen DE toward the enlarged projection plane is drawn. The reflective optical element PZ has a convex optical surface on the display element screen DE side.

  FIG. 4 is an aberration diagram (spherical aberration (a), astigmatism (b), distortion (c)) of Example 1 in the wide-angle end state, and FIG. 6 is an example in the intermediate state. 1 is an aberration diagram (spherical aberration (a), astigmatism (b), distortion aberration (c)), and FIG. 8 is an aberration diagram (spherical aberration (a), Astigmatism (b), distortion (c)). In the following aberration diagrams, in the spherical aberration diagram, the solid line represents the d line and the dotted line represents the g line, and in the astigmatism diagram, the solid line represents the sagittal image plane and the dotted line represents the meridional image plane.

(Example 2)
Lens data of the projection optical system of Example 2 is shown in (Table 2) below.

(Table 2)
Example 2
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
Screen ∞ 2000.00
1 ∞ 0.30 1.52300 54.5 1.87
2 ∞ 0.50 1.48900 60.6 1.78
3 R1 0.70 1.40000 39.8 1.69
4 ∞ 0.55 1.52300 54.5 1.42
5 ∞ 1.99 1.27
6 (Aperture) ∞ 1.66 0.38
7 * 14.637 1.50 1.54470 56.2 1.15
8 * -7.962 1.47 1.45
9 * -441.395 1.00 1.63200 23.4 1.87
10 * 4.421 1.76 2.25
11 * -4.712 1.84 1.54470 56.2 2.77
12 * -3.665 1.00 3.32
13 11.810 12.00 1.77250 49.6 4.86
14 ∞ 4.83
Display element ∞


Aspheric coefficient
7th surface K = 0.18041E + 02 10th surface K = -0.28818E + 01
A4 = 0.16258E-02 A4 = -0.51515E-02
A6 = 0.19644E-03 A6 = 0.26325E-03
A8 = 0.43649E-03 A8 = 0.61140E-07
A10 = 0.39700E-03 A10 = -0.10456E-06
8th surface K = -0.22408E + 02 A12 = 0.15624E-06
A4 = 0.34412E-03 11th surface K = -0.49824E + 01
A6 = 0.20178E-03 A4 = -0.79116E-03
A8 = -0.25847E-04 A6 = -0.29902E-03
A10 = 0.15810E-05 A8 = 0.18823E-04
9th surface K = 0.54520E + 05 A10 = 0.20227E-06
A4 = -0.58195E-02 A12 = 0.15069E-06
A6 = 0.14529E-03 12th surface K = -0.10076E + 01
A8 = -0.27043E-04 A4 = -0.39439E-03
A10 = -0.89304E-05 A6 = -0.13325E-03
A12 = -0.13634E-05 A8 = 0.66953E-07
A10 = 0.78410E-08
A12 = 0.79000E-09

Focal length at each position, distance between lens final surface and paraxial imaging point at screen distance of this embodiment (L)
F number
f L Fno
Wide 10.47 5.93 14.99
Middle 10.96 2.60 14.99
Tele 11.14 1.37 14.99

Curvature radius, angle of view of each position, focal length of the first lens, total lens length
R1 Angle of view ω Focal length of the first lens Total lens length
Wide 2.96 51.67 -33.43 28.87
Middle ∞ 48.33 0.00 28.87
Tele -8.54 46.83 96.45 28.87

Zoom ratio, image height
Zoom ratio Image height
1.06 4.80

  FIG. 9 is a cross-sectional view of the projection optical system of Example 2 in the state at the wide-angle end, FIG. 11 is a cross-sectional view of the projection optical system of Example 2 in the intermediate state, and FIG. Although it is a sectional view of the projection optical system of Example 2 in the end state, wiring to the first lens L1 and the like are omitted. The projection optical system of Example 1 includes a first lens L1 having a variable refractive power, a second lens L2 having a positive refractive power, and a third lens L3 having a negative refractive power from the enlarged projection plane side (left side). And a fourth lens L4 having a positive refractive power, and a reflective optical element PZ, both of which have a fixed position in the optical axis direction, and zooming changes the voltage applied to the first lens L1. Done in In the figure, DE is a display element screen, and only the optical path from the display element screen DE toward the enlarged projection plane is drawn. The reflective optical element PZ has a convex optical surface on the enlarged projection surface side.

  FIG. 10 is an aberration diagram of Example 2 (spherical aberration (a), astigmatism (b), distortion (c)) in the wide-angle end state, and FIG. 12 is an example in the intermediate state. 2 is an aberration diagram (spherical aberration (a), astigmatism (b), distortion aberration (c)), and FIG. 14 is an aberration diagram (spherical aberration (a), Astigmatism (b), distortion (c)).

(Example 3)
Lens data of the projection optical system of Example 3 is shown in the following (Table 3).

(Table 3)
Example 3
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
Screen ∞ 2000.00
1 ∞ 0.30 1.52300 54.5 2.73
2 ∞ 0.50 1.62390 59.1 2.62
3 R1 0.70 1.40000 39.8 2.51
4 ∞ 0.55 1.52300 54.5 2.20
5 ∞ 3.03 2.01
6 (Aperture) ∞ 1.47 0.27
7 * -33.691 2.00 1.55200 71.8 1.14
8 * -4.005 2.00 1.73
9 * -18.421 1.50 1.82200 24.2 2.52
10 * 4.113 1.50 3.48
11 * -8.246 2.00 1.72900 54.1 3.77
12 * -3.684 0.50 3.99
13 12.375 10.00 1.77500 47.1 5.36
14 ∞ 5.04
Display element ∞


Aspheric coefficient
Surface 7 K = 0.50000E + 02 Surface 10 K = -0.18346E + 02
A4 = 0.35725E-01 A4 = -0.43582E-02
A6 = -0.21376E-01 A6 = 0.31964E-03
A8 = 0.48108E-02 A8 = -0.15801E-05
A10 = -0.19948E-03 A10 = -0.95419E-06
8th surface K = -0.15497E + 02 A12 = -0.28390E-08
A4 = 0.11522E-01 11th surface K = -0.94287E + 01
A6 = 0.13573E-02 A4 = -0.12289E-02
A8 = -0.10609E-02 A6 = -0.19875E-03
A10 = 0.36112E-04 A8 = 0.22777E-04
9th surface K = 0.50000E + 02 A10 = -0.28601E-06
A4 = -0.55759E-02 A12 = -0.56870E-08
A6 = 0.14154E-02 12th surface K = -0.93086E + 00
A8 = -0.30203E-04 A4 = 0.10663E-04
A10 = -0.11050E-04 A6 = -0.10821E-03
A12 = 0.60941E-06 A8 = 0.94858E-06
A10 = 0.16428E-06
A12 = 0.19198E-07

Focal length at each position, distance between lens final surface and paraxial imaging point at screen distance of this embodiment (L)
F number
f L Fno
Wide 7.52 3.37 15.01
Middle 8.53 1.94 15.02
Tele 9.02 1.25 15.02

Curvature radius, angle of view of each position, focal length of the first lens, total lens length
R1 Angle of view ω Focal length of the first lens Total lens length
Wide 10.00 66.17 -33.43 27.99
Middle ∞ 59.04 0.00 27.99
Tele -25.00 55.93 96.45 27.99

Zoom ratio, image height
Zoom ratio Image height
1.20 4.80

  FIG. 15 is a cross-sectional view of the projection optical system of Example 3 in the wide-angle end state, FIG. 17 is a cross-sectional view of the projection optical system of Example 3 in the intermediate state, and FIG. Although it is a sectional view of the projection optical system of Example 3 in the end state, wiring to the first lens L1 and the like are omitted. The projection optical system of Example 1 includes a first lens L1 having a variable refractive power, a second lens L2 having a positive refractive power, and a third lens L3 having a negative refractive power from the enlarged projection plane side (left side). And a fourth lens L4 having a positive refractive power and a reflective optical element PZ, both of which have a fixed position in the optical axis direction, and zooming is performed by changing the voltage applied to the first lens L1. Done. In the figure, DE is a display element screen, and only the optical path from the display element screen DE toward the enlarged projection plane is drawn. The reflective optical element PZ has a convex optical surface on the enlarged projection surface side.

  FIG. 16 is an aberration diagram (spherical aberration (a), astigmatism (b), distortion (c)) of Example 3 in the wide-angle end state, and FIG. 17 is an example in the intermediate state. 3 is an aberration diagram (spherical aberration (a), astigmatism (b), distortion aberration (c)), and FIG. 18 is an aberration diagram of Example 2 (spherical aberration (a), Astigmatism (b), distortion (c)).

Example 4
Lens data of the projection optical system of Example 4 is shown in the following (Table 4).

(Table 4)
Example 4
Surface number R (mm) D (mm) Nd νd Effective radius (mm)
Screen ∞ 2000.00
1 ∞ 0.30 1.52300 54.5 1.56
2 ∞ 0.50 1.48900 60.6 1.46
3 R1 0.70 1.40000 39.8 1.33
4 ∞ 0.55 1.52300 54.5 1.04
5 ∞ 1.00 0.85
6 (Aperture) ∞ 2.28 0.31
7 * -17.552 2.14 1.54470 56.2 1.51
8 * -4.075 0.45 2.14
9 * 11.056 1.00 1.63200 23.4 2.65
10 * 2.686 1.04 3.08
11 * -150.489 2.60 1.54470 56.2 3.26
12 * -5.379 1.68 3.74
13 14.073 1.20 1.80420 46.5 4.89
14 ∞ 0.50 4.88
15 ∞ 9.00 1.51680 64.2 4.88
16 ∞ 4.83
Display element ∞


Aspheric coefficient
7th surface K = 0.11484E + 03 10th surface K = -0.45618E + 01
A4 = -0.14601E-01 A4 = -0.31883E-02
A6 = 0.69146E-02 A6 = 0.14229E-03
A8 = -0.21332E-04 A8 = -0.46611E-05
A10 = 0.70141E-04 A10 = -0.51465E-06
8th surface K = -0.40725E + 01 A12 = -0.16916E-07
A4 = -0.28052E-02 11th surface K = 0.20434E + 04
A6 = 0.30757E-03 A4 = 0.16442E-02
A8 = -0.15791E-03 A6 = -0.19708E-04
A10 = 0.56720E-04 A8 = 0.79140E-05
9th surface K = 0.11078E + 01 A10 = -0.49290E-08
A4 = -0.45651E-02 A12 = -0.66733E-07
A6 = -0.13650E-03 12th surface K = -0.35296E + 01
A8 = -0.49573E-05 A4 = -0.21192E-03
A10 = 0.10394E-05 A6 = 0.29860E-04
A12 = 0.40975E-06 A8 = 0.13002E-05
A10 = -0.13258E-06
A12 = 0.65660E-08

Focal length at each position, distance between lens final surface and paraxial imaging point at screen distance of this embodiment (L)
F number
f L Fno
Wide 8.88 4.01 15.00
Middle 9.25 1.56 15.00
Tele 9.39 0.66 15.00

Curvature radius, angle of view of each position, focal length of the first lens, total lens length
R1 Angle of view ω Focal length of the first lens Total lens length
Wide 2.96 59.63 -33.43 26.50
Middle ∞ 56.97 0.00 26.50
Tele -8.54 55.80 96.45 26.50

Zoom ratio, image height
Zoom ratio Image height
1.06 4.80

  FIG. 21 is a cross-sectional view of the projection optical system of Example 4 in the state at the wide-angle end, FIG. 23 is a cross-sectional view of the projection optical system of Example 4 in the intermediate state, and FIG. Although it is a sectional view of the projection optical system of Example 4 in the end state, wiring to the first lens L1 and the like are omitted. The projection optical system of Example 1 includes a first lens L1 having a variable refractive power, a second lens L2 having a positive refractive power, and a third lens L3 having a negative refractive power from the enlarged projection plane side (left side). And a fourth lens L4 having a positive refractive power and a fifth lens L5 having a positive refractive power, both of which have a fixed position in the optical axis direction, and the zooming is applied to the first lens L1. This is done by changing the voltage. In the figure, DE is a display element screen, and only the optical path from the display element screen DE arranged between the fifth lens L5 and the display screen DE toward the enlarged projection plane is drawn.

  FIG. 22 is an aberration diagram (spherical aberration (a), astigmatism (b), distortion (c)) of Example 4 in the wide-angle end state, and FIG. 24 is an example in the intermediate state. 4 is an aberration diagram (spherical aberration (a), astigmatism (b), distortion aberration (c)), and FIG. 26 is an aberration diagram of Example 4 (spherical aberration (a), Astigmatism (b), distortion (c)).

  Table 5 shows values of the respective examples corresponding to the respective conditional expressions.

  The present invention can provide a projection optical system suitable for a small projector.

DESCRIPTION OF SYMBOLS 11 Water repellent layer 12 Hydrophilic layer 21 1st liquid 22 2nd liquid 24 Interface 25 Electrode ring 31 Feeding circuit 40 Lower container 41 Recess 42 Recess 43 Recess 43 Electrode ring 43a Electrode end surface 44 Insulating layer 50 Upper container 51 Electrode ring 51a Exposed 51b Terminal portion 52 Insulating layer COL Condensing lens DE Display element screen L1 First lens L2 Second lens L3 Third lens L4 Fourth lens L5 Fifth lens LD Light source PJT Projector PZ Reflective optical element TRP Reflective surface

Claims (11)

  In a projection optical system composed of a plurality of lenses for enlarging and projecting an image of a display element surface on a screen surface, at least one lens having a variable refractive power is used, a distance between the lenses is fixed, and the refractive power is variable. A projection optical system characterized by changing a size of an image of a display element surface projected on a screen surface by changing a refractive power of a lens.   In a projection optical system for enlarging and projecting an image of a display element surface onto a screen surface, a first lens having at least a variable refractive power, a second lens having a positive refractive power, and a negative refractive power from the enlarged projection surface side A third lens having a positive refracting power, the first lens to the fourth lens being fixed in the position in the optical axis direction, and the lens having a variable refracting power on the screen surface. A projection optical system characterized in that the size of the image of the display element surface projected onto the screen is changed.   The projection optical system according to claim 1, wherein the projection optical system has an F number greater than 8. 4.   The lens having a variable refractive power is provided with a second liquid that is not mixed with the first liquid and enclosed in a container, and the physical quantity applied to the container is changed to change the first liquid and the second liquid. The projection optical system according to claim 1, wherein the projection optical system is an optical element capable of changing a boundary surface shape. The projection optical system according to claim 1, wherein the following conditional expression is satisfied in the projection optical system.
1.6 <fB _1-4w / f _w <7.8 (1)
However,
fB _1-4w : Back focus of the composite system of the first lens to the fourth lens at the wide angle end f _w : Focal length of the projection optical system at the wide angle end The projection optical system according to claim 1, wherein the following conditional expression is satisfied in the projection optical system.
−6.0 <f _1w / f _w <−3.1 (2)
However,
f _1w : Focal length of the lens with variable refractive power at the wide angle end f _w : Focal length of the projection optical system at the wide angle end The projection optical system according to claim 1, wherein the fourth lens satisfies the following conditional expression.
−8.1 <(r ₄₂ + r ₄₁ ) / (r ₄₂ −r ₄₁ ) <− 1.0 (3)
However,
r ₄₂ : radius of curvature of the enlarged projection side lens surface of the fourth lens r ₄₁ : radius of curvature of the display element side lens surface of the fourth lens The projection optical system according to claim 1, wherein the fourth lens satisfies the following conditional expression.
0.4 <f ₄ / f _w <2.2 (4)
However,
f ₄ : focal length of the fourth lens f _w : focal length of the projection optical system at the wide angle end   The projection optical system according to claim 1, further comprising a fifth lens having a positive refractive power.   The projection optical system according to claim 1, wherein the projection optical system includes a reflective optical element having a curvature at a position closest to the display element surface.   A projector comprising the projection optical system according to claim 1.

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