Projection lens and projection device

Abstract

To provide a miniaturized projection lens.SOLUTION: A projection lens 40 is provided, comprising, in order from the magnification side, a first lens group G1 having positive or negative refractive power, an aperture stop, and a second lens group G2 having positive refractive power, the first lens group G1 comprising a first sub lens group G1m having a negative refractive index and a second sub lens group G1p having a positive refractive index arranged in order from the magnification side. The projection lens satisfies the following conditional expressions: 0.1<1 / fg1p-1 / fg1 m<0.25, ω>50, 2.5<(DL1×LL)×F / IH2<6.5, 3.0<BF / F<5.0, where fg1p represents a composite focal length of the first sub lens group G1m, fg1m represents a composite focal length of the second sub lens group G1p, ω represents a maximum half view angle of the projection lens, IH represents an image circle, DL1 represents an effective radius of a lens closest to a screen, LL represents a total lens length, F represents a composite focal length of all lenses, BF represents an air-equivalent back focal length in length.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a projection lens for enlarging and projecting an image, and to a projection device incorporating the same. [Background technology]

[0002] A known projection lens system includes a first lens group I with negative refractive power and a second lens group II with positive refractive power, arranged from the magnification side with the largest air gap between them. The lens group is approximately telecentric on the reduction side and achieves a half angle of view of 60 degrees or more (see Patent Document 1). In this projection lens, the first lens group includes groups 1A, 1B, and 1C. Group 1A includes a lens with aspherical surfaces on both sides. Group 1B includes a negative meniscus lens with a convex surface facing the magnification side, a negative lens with a large curvature on the reduction side, and a biconcave lens. Group 1C includes at least one positive lens. The second lens group II includes a lens with an aspherical surface and two triplet lenses, with an aperture stop located near the lens closest to the magnification side. The triplet lenses are formed by placing three lenses close to each other or cementing two or more lenses together. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-190999 Summary of the Invention [Problem to be solved by the invention]

[0004] The projection lens has a large lens diameter and length, which affects the size and weight of the projection device in which it is incorporated, and also affects the degree of freedom in exterior design and the degree of freedom in designing space when applied to a projection device, etc. [Means for solving the problem]

[0005] A projection lens according to one aspect of the present invention comprises, in order from the magnification side, a first lens group having positive or negative refractive power, an aperture stop, and a second lens group having positive refractive power, The first lens group includes, in order from the magnification side, a first sub-lens group having a negative refractive index and a second sub-lens group having a positive refractive index, The following conditional expression is satisfied: 0.1<1 / fg1p-1 / fg1m<0.25 … (1) ω>50 … (2) 2.5<(DL1×LL)×F / IH 2 <6.5 … (3) 3.0 <BF / F<5.0 … (4) Here, the value fg1p is the composite focal length of the first sub-lens group, the value fg1m is the composite focal length of the second sub-lens group, the value ω is the maximum half angle of view of the projection lens, the value IH is the image circle, the value DL1 is the effective radius of the lens closest to the screen, the value LL is the total lens length, the value F is the composite focal length of all lenses, and the value BF is the back focus distance in air equivalent length.

[0006] A projection device according to one aspect of the present invention comprises the above-described projection lens and an image forming unit that forms a projected image on the reduction-side conjugate plane of the projection lens, and the image forming unit has a light source device and a light modulation element that modulates light from the light source device. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram illustrating a projection device including a projection lens according to an embodiment. [Figure 2] 1 is a diagram showing the configuration and light rays of a projection lens according to an embodiment of the present invention. [Figure 3] 3A and 3B are diagrams illustrating focusing of a projection lens according to an embodiment. [Figure 4] FIG. 2 is a diagram illustrating a projection lens according to the first embodiment. [Figure 5] FIG. 3 is a diagram showing longitudinal aberration characteristics of the projection lens of Example 1. [Figure 6]4 is a diagram showing the lateral aberration characteristics of the projection lens of Example 1. FIG. [Figure 7] FIG. 10 is a diagram illustrating a projection lens according to a second embodiment. [Figure 8] FIG. 10 is a diagram showing longitudinal aberration characteristics of the projection lens of Example 2. [Figure 9] FIG. 10 is a diagram showing the lateral aberration characteristics of the projection lens of Example 2. [Figure 10] 10A and 10B are diagrams illustrating a projection lens according to a third embodiment. [Figure 11] FIG. 10 is a diagram showing longitudinal aberration characteristics of the projection lens of Example 3. [Figure 12] FIG. 10 is a diagram showing the lateral aberration characteristics of the projection lens of Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0008] [First embodiment] A projection lens according to an embodiment of the present invention and a projection device incorporating the same will be described below with reference to the drawings.

[0009] As shown in FIG. 1, a projection device 2 incorporating a projection lens 40 according to the embodiment includes an optical system section 50 that projects image light, and a circuit device 80 that controls the operation of the optical system section 50.

[0010] In the optical system section 50, the light source device 10 emits light containing R light, G light, and B light in a homogenized state. The light source device 10 includes a light source lamp such as an ultra-high pressure mercury lamp, a two-stage integrator lens having a plurality of lens elements arranged in an array, a polarization conversion element that converts the light that has passed through the two-stage integrator lens into predetermined linearly polarized light, and a superimposing lens that superimposes the illumination light emitted from the latter-stage integrator lens on the display areas of the liquid crystal panels 29R, 29G, and 29B.

[0011] The first dichroic mirror 21 reflects the R light incident from the light source device 10 and transmits the G and B light. The R light reflected by the first dichroic mirror 21 passes through a reflecting mirror 25 and a field lens 28R and enters a liquid crystal panel 29R, which is a light modulation element OM. The liquid crystal panel 29R forms an R image by modulating the R light in accordance with an image signal.

[0012] The second dichroic mirror 22 reflects the G light from the first dichroic mirror 21 and transmits the B light. The G light reflected by the second dichroic mirror 22 passes through a field lens 28G and enters a liquid crystal panel 29G, which serves as a light modulation element OM. The liquid crystal panel 29G forms a G image by modulating the G light in accordance with an image signal. The B light transmitted through the second dichroic mirror 22 passes through relay lenses 23 and 24, reflecting mirrors 26 and 27, and a field lens 28B and enters a liquid crystal panel 29B, which serves as a light modulation element OM. The liquid crystal panel 29B modulates the B light in accordance with an image signal to form a B image.

[0013] The cross dichroic prism 31 is a prism for light synthesis, and synthesizes the light modulated by each of the liquid crystal panels 29R, 29G, and 29B to form image light, which is then directed to the projection lens 40.

[0014] The projection lens 40 is a projection lens that enlarges and projects the image light modulated by each of the liquid crystal panels 29R, 29G, and 29B and combined by the cross dichroic prism 31 onto a screen SC (see FIG. 2, which will be described later). The liquid crystal panels 29R, 29G, and 29B form an image forming unit 20a that forms a projection image on a reduction-side conjugate plane RC (see FIG. 2) of the projection lens 40.

[0015] The circuit device 80 comprises an image processing unit 81 to which an external image signal such as a video signal is input, a display driving unit 82 that drives the liquid crystal panels 29R, 29G, and 29B provided in the optical system part 50 based on the output of the image processing unit 81, a lens driving unit 83 that operates a driving mechanism (not shown) provided in the projection lens 40 to adjust the state of the projection lens 40, and a main control unit 88 that comprehensively controls the operation of these circuit parts 81, 82, 83, etc.

[0016] The image processing unit 81 converts the input external image signal into an image signal including color gradations, etc. The image processing unit 81 can also perform various types of image processing, such as distortion correction and color correction, on the external image signal.

[0017] The display drive unit 82 can operate the liquid crystal panels 29R, 29G, and 29B based on the image signal output from the image processing unit 81, and can form an image corresponding to the image signal or an image obtained by applying image processing to the image signal on the liquid crystal panels 29R, 29G, and 29B.

[0018] The lens driver 83 operates under the control of the main controller 88 and adjusts the imaging state of the projection lens 40 by appropriately moving some of the optical elements that make up the projection lens 40 along the optical axis OA via actuator AC. In this case, the lens groups to be moved can be moved individually, or they can be linked together using a cam mechanism. In this way, when the magnification is changed electrically using actuator AC, the projection lens 40 can be smoothly brought into focus, and by combining it with a focus sensor (not shown), an AF operation can be achieved that automatically adjusts the focus position depending on the installation location of the projector 2 and the projection direction.

[0019] The actuator AC etc. may be omitted. In other words, the focus of the projection lens 40 may be adjusted by manually moving some of the optical elements that make up the projection lens 40 using a mechanical mechanism including a cam mechanism etc.

[0020] The lens driving unit 83 may change the vertical position and projection state of the image projected onto the screen SC (see Figure 2) by adjusting the tilt, which moves the entire projection lens 40 in the vertical direction perpendicular to the optical axis OA.

[0021] The projection lens 40 of the embodiment will be specifically described below with reference to Fig. 2. The projection lens 40 illustrated in Fig. 2 has the same configuration as the projection lens 40 of Example 1, which will be described later.

[0022] The projection lens 40 of the embodiment projects an image formed on the liquid crystal panel 29G (29R, 29B) or the projection surface of the image forming unit 20a onto a screen SC. Here, a prism PR corresponding to the cross dichroic prism 31 in FIG. 1 is disposed between the projection lens 40 and the liquid crystal panel 29G (29R, 29B).

[0023] The projection lens 40 includes, in order from the screen SC on the enlargement side, a first lens group G1 having positive or negative refractive power, an aperture stop ST, and a second lens group G2 having positive refractive power.

[0024] The first lens group G1 consists of, from the magnification side, a negative first lens L1g1, a negative second lens L2g1, a negative third lens L3g1, a positive fourth lens L4g1, and a positive fifth lens L5g1. In other words, the first lens group G1 is configured with five lenses, from the magnification side, combining negative, negative, negative, positive, and positive refractive powers. Focusing on the smallest lens elements, the first lens group G1 includes, from the magnification side, a first lens L11, a second lens L12, a third lens L13, a fourth lens L14, a fifth lens L15, a sixth lens L16, and a seventh lens L17. The positive fourth lens L4g1 is a cemented lens composed of the fourth lens L14 and the fifth lens L15. The positive fifth lens L5g1 is a cemented lens composed of the sixth lens L16 and the seventh lens L17. That is, the first lens L1g1, the second lens L2g1, and the third lens L3g1 are single lenses. In the above, the first lens L1g1, ie, the first lens L11, is a lens with aspherical surfaces on both sides.

[0025] The first lens group G1 includes, in order from the magnification side, a first sub-lens group G1m having a negative refractive index and a second sub-lens group G1p having a positive refractive index. The first sub-lens group G1m includes a first lens L1g1, a second lens L2g1, and a third lens L3g1. That is, the first sub-lens group G1m is composed only of lenses L1g1, L2g1, and L3g1 having negative refractive power. The second sub-lens group G1p includes a fourth lens L4g1 and a fifth lens L5g1. That is, the second sub-lens group G1p is composed only of lenses L4g1 and L5g1 having positive refractive power. In the example of FIG. 2, the first lens group G1 has positive refractive power as a whole. By making the first lens group G1 positive, the overall lens length and effective diameter can be reduced. Furthermore, by appropriately adjusting the negative refractive power of the first sub-lens group G1m and the positive refractive power of the second sub-lens group G1p in the first lens group G1, the projection lens 40 can achieve both compactness and good correction of various aberrations. Here, the refractive power is defined as the reciprocal of each focal length.

[0026] In the first lens group G1, at least one of the third lens L3g1, which is the negative lens located closest to the reduction side, and the fourth lens L4g1 and fifth lens L5g1, which are positive lenses, is a cemented lens. That is, in the illustrated embodiment, the fourth lens L4g1 and the fifth lens L5g1, which are positive lenses, are cemented lenses, but the third lens L3g1 may also be a cemented lens. In this way, by using a cemented lens, chromatic aberration of magnification can be effectively suppressed even in a compact size.

[0027] In the first lens group G1, the first lens L1g1 is a lens with a large change in sag amount and is basically made of a plastic glass material, but is not limited to this. The other lenses L2g1 to L5g1 are made of a glass glass material from the viewpoint of light resistance, but are not limited to this.

[0028] The second lens group G2 consists of, from the magnification side, a negative first lens L1g2, a negative second lens L2g2, a positive third lens L3g2, a negative fourth lens L4g2, a positive fifth lens L5g2, and a positive sixth lens L6g2. In other words, the second lens group G2 is configured with six lenses: a negative-negative-positive-negative-positive-positive lens, from the magnification side. Focusing on the smallest lens elements, the second lens group G2 includes, from the magnification side, a first lens L21, a second lens L22, a third lens L23, a fourth lens L24, a fifth lens L25, a sixth lens L26, a seventh lens L27, an eighth lens L28, a ninth lens L29, and a tenth lens L30. The negative first lens L1g2 is a cemented lens consisting of the first lens L21 and the second lens L22. The positive third lens L3g2 is a cemented lens composed of the fourth lens L24, the fifth lens L25, and the sixth lens L26. The negative fourth lens L4g2 is a cemented lens composed of the seventh lens L27 and the eighth lens L28. In other words, the second lens L2g2, the fifth lens L5g2, and the sixth lens L6g2 are single lenses. In the above, the second lens L2g2, i.e., the third lens L23, is a double-sided aspherical lens. By including at least one aspherical lens with negative refractive power in the second lens group G2, various aberrations such as field curvature can be suppressed.

[0029] In the second lens group G2, the lenses L1g2 to the sixth lens L6g2 are made of glass material from the viewpoint of light resistance, but the material is not limited to this.

[0030] Although not shown, the second lens group G2 may have a five-lens configuration of negative-positive-positive-negative-positive in order from the magnification side (Example 2 described later), or a six-lens configuration of positive-negative-positive-positive-negative-positive in order from the magnification side (Example 3 described later). In other words, while the second lens group G2 has a basic configuration of negative-positive-negative-positive, it is possible to add a lens with a small positive or negative refractive power on the magnification side, or to divide the positive lens following the negative lens into two.

[0031] When focusing on the arrangement of refractive powers of the projection lens 40, the first lens group G1 has a positive fifth lens L5g1 disposed on the most reduction side, and the second lens group G2 has a first lens L1g2 with negative refractive power disposed on the most enlargement side, with positive lenses L3g2, L5g2, and L6g2 disposed on the reduction side of the first lens L1g2 with negative refractive power disposed on the most enlargement side. As described above, a positive, negative, and positive lens configuration can further reduce aberrations. Because the first lens group G1 is thus composed of a negative first sub-lens group G1m and a positive second sub-lens group G1p, from the perspective of aberration correction, it is preferable to provide a negative lens as the lens on the most enlargement side of the second lens group G2.

[0032] Furthermore, when focusing on the arrangement of refractive powers of the projection lens 40, the second lens group G2 has at least three positive lenses L3g2, L5g2, and L6g2, and one of the three positive lenses L3g2, L5g2, and L6g2, the sixth lens L6g2, is arranged on the most reduction side of the second lens group G2. By dividing the positive lenses into three and arranging them, it is possible to suppress the occurrence of aberrations. Furthermore, the lens with positive refractive power arranged on the most reduction side has the effect of creating a nearly telecentric configuration as a whole.

[0033] The aperture stop ST is a surface for defining the F-number, and is placed at a position where the chief ray passes through the optical axis OA. An actual tangible object may be placed as the stop member, or no stop member may be placed at all.

[0034] The projection lens 40 of this embodiment satisfies the following conditional expressions. 0.1<1 / fg1p-1 / fg1m<0.25 … (1) ω>50 … (2) 2.5<(DL1×LL)×F / IH 2 <6.5 … (3) 3.0 <BF / F<5.0 … (4) Here, the value fg1p is the composite focal length of the first sub-lens group G1m, the value fg1m is the composite focal length of the second sub-lens group G1p, the value ω is the maximum half angle of view of the projection lens 40, the value IH is the image circle, the value DL1 is the effective radius of the lens closest to the screen SC, the value LL is the total lens length, the value F is the composite focal length of all the lenses, and the value BF is the back focus distance in air equivalent length. Note that the image circle is the height of a ray of light passing through the maximum image height on the lens surface closest to the enlargement side of the projection lens 40.

[0035] Conditional formula (1) is a formula for realizing a small lens with good resolving power. By setting the value 1 / fg1p-1 / fg1m of the above conditional formula to be equal to or greater than the lower limit, it is possible to achieve a wide angle of view while optimizing the correction of various aberrations, particularly chromatic aberration. By setting the value 1 / fg1p-1 / fg1m of the above conditional formula to be equal to or less than the upper limit, it is possible to achieve a wide angle of view while optimizing the correction of various aberrations, particularly chromatic aberration.

[0036] Conditional formula (2) expresses the widening of the angle of the projection lens 40.

[0037] Conditional formula (3) indicates the lens diameter and overall length relative to the image circle, and is an index for compactness. The value of the above conditional formula is (DL1 × LL) × F / IH 2 By setting F / IH equal to or greater than the lower limit, various aberrations such as curvature of field and distortion can be effectively corrected. 2 By making the value of the upper limit or less, it is possible to prevent the lens diameter from becoming large, thereby achieving cost reduction and size reduction.

[0038] Conditional expression (4) is an expression for ensuring an appropriate back focus. By setting the value BF / F of the above conditional expression to the lower limit or more, it is possible to ensure space for arranging an insert such as a prism PR. By setting the value BF / F of the above conditional expression to the upper limit or less, it is possible to realize a lens configuration that provides a wide angle while still effectively correcting various aberrations.

[0039] The projection lens 40 of the embodiment satisfies the following conditional expressions. 3.1 < nL2g1 × nL3g1 … (5) 0.59 < L2θgf or L3θgf … (6) Here, the value nL2g1 is the refractive index with respect to the d-line of the second lens from the magnifying side in the first lens group G1, that is, the second lens L2g1, the value L2θgf is the partial dispersion value of the second lens (the second lens L2g1), the value nL3g1 is the refractive index with respect to the d-line of the third lens from the magnifying side in the first lens group G1, that is, the third lens L3g1, and the value L3θgf is the partial dispersion value of the third lens (the third lens L3g1).

[0040] In general, the partial dispersion value θgf is defined by the following formula. The value defined by θgf = (Ng - Nf) / (Nf - Nc) Here, Ng: Refractive index of the g-line Nf: Refractive index of the f-line Nc: Refractive index of the c-line

[0041] By satisfying the conditional expressions (5) and (6), it is possible to achieve miniaturization and wide-angleization of the projection lens 40 while suppressing chromatic aberration.

[0042] The projection lens 40 of the embodiment satisfies the following conditional expressions. -1.2 < fg1m / F < -1.0 … (7) Here, the value fg1m is the combined focal length of the second sub-lens group G1p (the combined focal length of all negative lenses in the first lens group G1), and the value F is the combined focal length of all lenses.

[0043] By setting the value of fg1m / F in the above conditional expression to be not less than the lower limit value, it is possible to advantageously suppress various aberrations while ensuring sufficient back focus. By setting the value of fg1m / F in the above conditional expression to be not more than the upper limit value, it is possible to suppress various aberrations while ensuring sufficient back focus.

[0044] FIG. 3 is a diagram illustrating focusing of the projection lens 40 of the embodiment. For focusing, at least two or more lenses constituting the first lens group G1 are moved in the same direction on the optical axis OA. This allows focusing while effectively correcting field curvature when the projection distance is changed. In the illustrated example, the first lens group G1 includes a first focus group FG1 and a second focus group FG2. The first focus group FG1 is composed of the second lens L2g1 to the fourth lens L4g1, and the second focus group FG2 is composed of the fifth lens L5g1. When changing the projection position from a far distance to a near distance, the first lens group G1 is first moved toward the enlargement side and then toward the reduction side, and the second focus group FG2 is moved only toward the enlargement side. However, the focusing is not limited to the one shown in the figure, and for example, the first lens L1g1 to the fourth lens L4g1 of the first lens group G1 can be the first focusing group, and the fifth lens L5g1 can be the second focusing group. Furthermore, the second lens L2g1 of the first lens group G1 can be the first focusing group, the third lens L3g1 and the fourth lens L4g1 can be the second focusing group, and the fifth lens L5g1 can be the third focusing group.

[0045] As described above, the projection lens 40 of the embodiment consists of, from the magnification side, a first lens group G1 having positive or negative refractive power, an aperture stop, and a second lens group G2 having positive refractive power, and the first lens group G1 consists of, from the magnification side, a first sub-lens group G1m having a negative refractive index and a second sub-lens group G1p having a positive refractive index, and satisfies the following conditional expression: 0.1<1 / fg1p-1 / fg1m<0.25 … (1) ω>50 … (2) 2.5<(DL1×LL)×F / IH 2 <6.5 … (3) 3.0 <BF / F<5.0 … (4) Here, the value fg1p is the composite focal length of the first sub-lens group G1m, the value fg1m is the composite focal length of the second sub-lens group G1p, the value ω is the maximum half angle of view of the projection lens, the value IH is the image circle, the value DL1 is the effective radius of the lens closest to the screen, the value LL is the total lens length, the value F is the composite focal length of all lenses, and the value BF is the back focus distance in air equivalent length.

[0046] In the projection lens 40, by appropriately adjusting the negative refractive power of the first sub-lens group G1m and the positive refractive power of the second sub-lens group G1p in the first lens group G1, the projection lens 40 can achieve both compactness and good correction of various aberrations. In particular, by making the first lens group G1 positive, the overall lens length and effective diameter can be reduced. By satisfying conditional expressions (1) to (4), it is possible to realize a compact lens that has a wide angle of view and good resolving power while ensuring an appropriate back focus.

[0047] The projection device 2 described above includes the projection lens 40 and the image forming unit 20a that forms a projected image on the reduction-side conjugate plane RC of the projection lens 40. The image forming unit 20a includes the light source device 10 and the light modulation element OM that modulates the light from the light source device 10. This makes it possible to reduce the size of the projection device 2 that includes the projection lens 40.

[0048] [Example] The following describes examples of the projection lens 40. The meanings of the specifications common to Examples 1 to 3 described below are summarized below. R radius of curvature D Axis surface spacing (lens thickness or lens spacing) Refractive index of Nd d line Vd Abbe number of d line DL Lens Diameter

[0049] The aspherical surface is specified by the following polynomial (aspherical surface formula): TIFF2025153289000002.tif16166However, c: Curvature (1 / R) h: Height from the optical axis k: conic constant of the aspheric surface Ai: High-order aspherical coefficients of the aspherical surface Note that surface number 0 refers to the image surface (projection surface) on screen SC, STO refers to aperture stop ST, INF refers to infinity, and the final surface number refers to the display surface of liquid crystal panel 29G etc. Furthermore, surfaces with an "*" after the surface number are aspherical surfaces.

[0050] Example 1 The lens surface data for Example 1 is shown in Table 1 below. [Table 1] Surface number RD Nd Vd DL 0 Variable 1 1* -11.3599 4.386822 1.535037 55.7 35.21467 2* -22.0291 Variable 2 24.76318 3 35.5076 1.2 1.903659 31.3 18.71956 4 14.24023 13.20791 13.26067 5 -35.1455 4.117401 1.72916 54.7 12.3022 6 44.91622 2.637517 11.69227 7 75.90936 10.14208 1.6727 31.1 12 8 -18.1594 1.2 2.001 29.1 11.68956 9 -27.9899 Variable 3 12 10 38.91473 10 1.592701 35.3 11.6 11 -17.629 1.2 2.001 29.1 10.65539 12 -25.079 0.5 10.79873 13STO INF 0.830188 9.531606 14 -73.3449 2.755345 1.910822 35.3 9.507041 15 12.35393 7.879494 1.808095 22.8 9.52856 16 -8.5018E+3 1.480487 9.811811 17* -31.2815 1.269549 1.51633 64.1 9.899212 18* -49.8173 0.15 10.7 19 39.01397 7.24514 1.496999 81.6 10.76345 20 -20.4555 1.2 1.953749 32.3 10.92799 21 91.33022 7.629593 1.496999 81.6 11.91 22 -19.6921 0.2 12.6 23 -868.528 1.2 2.001 29.1 13.73117 24 30.88643 7.914476 1.48749 70.2 14.34479 25 -51.5769 0.1 15.22188 26 75.27753 6.502286 1.496999 81.6 17.34157 27 -55.1305 0.1 17.66078 28 138.4343 7.459241 1.48749 70.2 18.24151 29 -38.2797 1 18.31672 30 INF 30.69 1.516798 64.2 17.1191 31 INF 8.985093 12.90079

[0051] Table 2 below illustrates the movement of the focus lens when focusing for Example 1. "Variable 1" refers to the axial distance from the screen SC to the first lens L1g1 of the first lens group G1. "Variable 2" refers to the axial distance from the first lens L1g1 to the second lens L2g1 of the first focus group FG1. "Variable 3" refers to the axial distance from the fourth lens L4g1 of the first focus group FG1 to the fifth lens L5g1 of the second focus group FG2. [Table 2] Variable 1 Variable 2 Variable 3 640 10.013 17.754 906 9.770 17.663 1270 9.572 17.602 1380 9.650 17.577

[0052] Table 3 below shows the aspheric coefficients of the lens surfaces of Example 1. In Table 3 and the following tables, powers of 10 (for example, 1.00×10 +18 ) is expressed using E (for example, 1.00E+18). [Table 3] Surface number K A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15 1 -5.5043E+00 1.3374E-03 -3.4730E-05 -8.1789E-09 1.1034E-08 3.2123E-10 -1.2359E-11 5.2033E-14 -5.4867E-17 -5.6451E-17 3.2394E-18 -8.3012E-21 -4.9489E-22 2 -1.9912E+01 1.1467E-03 7.9764E-05 -6.2684E-06 7.8212E-08 6.1753E-09 -1.4514E-10 -8.8148E-13 -5.2935E-14 -1.1461E-15 1.0105E-16 Surface number K A1 A2 A3 A4 17 -5.8178E+00 1.4983E-04 -1.4916E-06 5.6793E-09 -1.3130E-11 18 1.4085E+01 1.9533E-04 -1.3108E-06 4.0419E-09 -4.7318E-12

[0053] Fig. 4 is a cross-sectional view of the projection lens 40 of Example 1. The projection lens 40 shown in Fig. 4 corresponds to the projection lens 40 of the first embodiment.

[0054] The projection lens 40 enlarges and projects an image on a display surface such as the liquid crystal panel 29G at a magnification that corresponds to the distance to the screen SC. The F-number of the projection lens 40 is 1.64.

[0055] The projection lens 40 comprises, in order from the screen SC on the enlargement side, a first lens group G1 having positive refractive power, an aperture stop ST, and a second lens group G2 having positive refractive power, and is approximately telecentric on the reduction side.

[0056] The first lens group G1 consists of, from the magnification side, a negative first lens L1g1, a negative second lens L2g1, a negative third lens L3g1, a positive fourth lens L4g1, and a positive fifth lens L5g1. In other words, the first lens group G1 is configured with five lenses, from the magnification side, combining negative, negative, negative, positive, and positive refractive powers. The first lens L1g1 is a single lens consisting of only the first lens L11, and is a plastic, aspherical, negative lens. The second lens L2g1 is a negative meniscus single lens consisting of only the second lens L12, and the third lens L3g1 is a biconcave single lens consisting of only the third lens L13. The fourth lens L4g1 is a cemented lens consisting of a biconvex, positive fourth lens L14 and a negative meniscus fifth lens L15. The fifth lens L5g1 is a cemented lens that combines a biconvex, positive sixth lens L16 and a negative meniscus seventh lens L17.

[0057] The second lens group G2 consists of, from the magnification side, a negative first lens L1g2, a negative second lens L2g2, a positive third lens L3g2, a negative fourth lens L4g2, a positive fifth lens L5g2, and a positive sixth lens L6g2. In other words, the second lens group G2 is configured with six lenses, from the magnification side, consisting of a negative, negative, positive, negative, positive, and positive lenses. The first lens L1g2 is a cemented lens consisting of a biconcave, negative first lens L21 and a biconvex, positive second lens L22. The second lens L2g2 is a single lens consisting of only the third lens L23, a glass-molded, aspherical, negative meniscus lens. The third lens L3g2 is a cemented lens consisting of a biconvex, positive fourth lens L24, a biconcave, negative fifth lens L25, and a biconvex, positive sixth lens L26. The fourth lens L4g2 is a cemented lens consisting of a biconcave negative seventh lens L27 and a biconvex positive eighth lens L28. The fifth lens L5g2 is a biconvex single lens consisting only of the ninth lens L29, and the sixth lens L6g2 is a biconvex single lens consisting only of the tenth lens L30.

[0058] Furthermore, during focusing, the first focus group FG1, which is composed of the second lens L2g1, the third lens L3g1, and the fourth lens L4g1, moves toward the enlargement side and then moves toward the reduction side, while the second focus group FG2, which is composed only of the fifth lens L5g1, moves in one direction toward the enlargement side.

[0059] FIG. 5 is a diagram showing the longitudinal aberration characteristics (that is, the spherical aberration characteristics, the astigmatism characteristics, and the distortion characteristics) of the projection lens 40 of the first embodiment.

[0060] FIG. 6 is a diagram showing the lateral aberration characteristics (tangential and sagittal aberration characteristics at three relative image heights of 1.0, 0.5, and 0.1) of the projection lens 40 of Example 1.

[0061] Example 2 The lens surface data for Example 2 is shown in Table 4 below. [Table 4] Surface number RD Nd Vd DL 0 Variable 1 1* -13.2957 1.9379 1.5350 55.7 23.08 2* -27.4494 6.0000 18.87 3 32.7803 1.2000 2.0010 29.1 16.39 4 15.2848 10.3868 12.73 5 -29.6199 1.0000 2.0010 29.1 12.07 6 17.0000 7.8077 1.8052 25.4 11.95 7 -60.2319 0.1000 12.11 8 -79.1855 6.4264 1.6398 34.4 12.11 9 -15.4518 1.7139 1.7292 54.6 12.20 10 -37.2466 Variable 2 12.86 11 44.3732 6.2372 1.5163 64.1 12.64 12 -57.6254 Variable 3 12.31 13STO INF 19.8659 10.77 14* -82.0104 2.6286 1.8088 40.9 10.14 15* -5.2991E+3 5.6433 10.20 16 50.3247 3.7430 1.8697 20 12.24 17 -84.9098 1.7786 12.29 18 -119.5998 1.2000 1.9537 32.3 12.15 19 29.5162 9.1840 1.4875 70.2 12.22 20 -20.3785 0.2000 12.60 21 39.9087 1.0000 2.0010 29.1 12.71 22 18.9392 11.7268 1.5174 52.4 12.18 23 -16.5651 1.2000 2.0010 29.1 12.27 24 -66.2727 0.1000 13.72 25 -605.1143 7.5058 1.4875 70.2 14.20 26 -20.8503 1.0000 14.60 27 INF 27.0520 1.5168 64.2 13.85 32 INF 8.9410 11.96

[0062] Table 5 below illustrates the movement of the focus lens when focusing for Example 2. "Variable 1" refers to the axial distance from the screen SC to the first lens L1g1 of the first focus group FG1. "Variable 2" refers to the axial distance from the fourth lens L4g1 of the first focus group FG1 to the fifth lens L5g1 of the second focus group FG2, and "Variable 3" refers to the axial distance from the fifth lens L5g1 to the aperture stop ST. [Table 5] Variable 1 Variable 2 Variable 3 640 16.083 3.286 906 16.019 3.633 1270 15.974 3.912 1380 15.965 3.948

[0063] Table 6 below shows the aspheric coefficients of the lens surfaces of Example 2. [Table 6] Surface number K A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15 1 -9.9355E+00 2.1859E-03 -4.7136E-05 -9.6137E-07 1.6932E-08 1.3830E-09 1.1156E-11 3.4235E-13 -2.1159E-14 -1.6193E-15 -4.3853E-17 9.2938E-20 1.4293E-19 2 -5.5429E+01 2.1857E-03 7.2818E-05 -7.0166E-06 5.9860E-08 5.1486E-09 -1.6499E-10 -3.1002E-13 -4.2487E-14 -1.6340E-15 6.2934E-17 Surface number K A1 A2 A3 A4 A5 A6 14 9.3122E+00 3.2227E-05 -9.4929E-08 -5.6015E-10 5.3903E-12 -2.1957E-14 15 1.0000E+02 4.6173E-05 -4.0661E-08 -5.8274E-10 5.1885E-12 -1.9464E-14

[0064] 7 is a cross-sectional view of the projection lens 40 of Example 2. The projection lens 40 enlarges and projects an image on a display surface such as a liquid crystal panel 29G at a magnification corresponding to the distance to the screen SC. The F-number of the projection lens 40 is 1.84.

[0065] The projection lens 40 comprises, in order from the screen SC on the enlargement side, a first lens group G1 having positive refractive power, an aperture stop ST, and a second lens group G2 having positive refractive power, and is approximately telecentric on the reduction side.

[0066] The first lens group G1 consists of, from the magnification side, a negative first lens L1g1, a negative second lens L2g1, a negative third lens L3g1, a positive fourth lens L4g1, and a positive fifth lens L5g1. In other words, the first lens group G1 is configured with five lenses, combining negative, negative, negative, positive, and positive refractive powers, from the magnification side. The first lens L1g1 is a single lens consisting of the first lens L11 alone and is a negative plastic lens with an aspherical surface. The second lens L2g1 is a negative meniscus single lens consisting of the second lens L12 alone. The third lens L3g1 is a cemented lens consisting of a biconcave, negative third lens L13 and a biconvex, positive fourth lens L14. The fourth lens L4g1 is a cemented lens consisting of a positive meniscus fifth lens L15 and a negative meniscus sixth lens L16. The fifth lens L5g1 is a biconvex single lens consisting of only the seventh lens L17.

[0067] The second lens group G2 consists of, from the magnification side, a negative first lens L1g2, a positive second lens L2g2, a positive third lens L3g2, a negative fourth lens L4g2, and a positive fifth lens L5g2. In other words, the second lens group G2 consists of five lenses: a negative-positive-positive-negative-positive lens, from the magnification side. The first lens L1g2 is a single lens consisting of the first lens L21 alone, and is a glass-molded, biconcave, aspherical, negative lens. The second lens L2g2 is a biconvex, positive single lens consisting of the second lens L22 alone. The third lens L3g2 is a cemented lens consisting of a biconcave, negative third lens L23 and a biconvex, positive fourth lens L24. The fourth lens L4g2 is a cemented lens consisting of a negative meniscus fifth lens L25, a biconvex, positive sixth lens L26, and a negative meniscus seventh lens L27. The sixth lens L6g2 is a single positive meniscus lens consisting of only the eighth lens L28.

[0068] Also, during focusing, the first focus group FG1, which is composed of the first lens L1g1, the second lens L2g1, the third lens L3g1, and the fourth lens L4g1, moves in one direction toward the enlargement side, and the second focus group FG2, which is composed only of the fifth lens L5g1, also moves in one direction toward the enlargement side.

[0069] FIG. 8 is a diagram showing the longitudinal aberration characteristics (that is, the spherical aberration characteristics, the astigmatism characteristics, and the distortion characteristics) of the projection lens 40 of the second embodiment.

[0070] FIG. 9 is a diagram showing the lateral aberration characteristics (tangential and sagittal aberration characteristics at three relative image heights of 1.0, 0.5, and 0.1) of the projection lens 40 of Example 2.

[0071] Example 3 The lens surface data for Example 3 is shown in Table 7 below. [Table 7] Surface number RD Nd Vd DL 0 Variable 1 1* -13.0586 4.728 1.535037 55.7 34.72 2* -34.0552 Variable 2 24.22 3 79.8793 1.593 1.72916 54.6 20.39 4 16.9770 Variable 3 14.17 5 -27.3511 1.000 2.001 29.1 11.56 6 21.2210 5.510 1.688931 31 11.55 7 -160.7270 1.089 11.75 8 54.0756 4.246 1.784723 25.6 12.22 9 -52.3136 Variable 4 12.20 10 33.1808 8.452 1.761821 26.5 11.42 11 -17.7414 1.200 2.001 29.1 10.96 12 329.5325 Variable 5 10.72 13STO -48.7040 3.668 1.48749 70.2 10.58 14 -19.3367 0.100 10.80 15* -62.2138 1.200 1.80882 40.9 10.52 16* 673.4890 5.899 10.60 17 -394.8201 2.600 1.869663 20.2 11.63 18 -57.4933 0.150 11.82 19 521.4513 4.740 1.808095 22.7 11.88 20 -29.9808 1.200 1.953749 32.3 11.91 21 44.0813 9.108 1.48749 70.2 12.16 22 -19.6604 0.200 12.60 23 60.5556 1.000 2.001 29.1 12.61 24 20.6087 11.190 1.539956 59.4 12.27 25 -18.2387 1.200 2.001 29.1 12.50 26 -50.2672 0.100 13.69 27 112.7047 7.642 1.48749 70.2 14.50 28 -24.6300 1.000 14.80 29 INF 30.690 1.516798 64.2 14.16 30 INF 9.255 12.01

[0072] Table 8 below illustrates the movement of the focus lens during focusing for Example 3. "Variable 1" refers to the axial distance from the screen SC to the first lens L1g1 of the first lens group G1. "Variable 2" refers to the axial distance from the first lens L1g1 to the second lens L2g1 of the first focus group FG1. "Variable 3" refers to the axial distance from the second lens L2g1 to the third lens L3g1 of the second focus group FG2. "Variable 4" refers to the axial distance from the fourth lens L4g1 of the second focus group FG2 to the fifth lens L5g1 of the third focus group FG3. "Variable 5" refers to the axial distance from the fifth lens L5g1 to the aperture stop ST. [Table 8] Variable 1 Variable 2 Variable 3 Variable 4 Variable 5 640 10.436 13.939 14.428 3.378 906 10.374 14.078 14.200 3.529 1270 10.335 14.157 14.055 3.635 1380 10.340 14.144 14.051 3.646

[0073] Table 9 below shows the aspheric coefficients of the lens surfaces of Example 3. [Table 9] Surface number K A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15 1 -4.9260E+00 1.5877E-03 -4.6383E-05 -4.3286E-08 2.2909E-08 2.0705E-10 -2.1960E-11 1.9795E-13 5.1193E-15 -9.3632E-17 1.1911E-18 -5.6524E-20 1.1557E-21 2 -1.4484E+01 1.5484E-03 7.5643E-05 -6.4076E-06 7.7362E-08 5.3840E-09 -1.6847E-10 -3.8239E-13 -2.7496E-14 -4.7668E-16 8.3173E-17 Surface number K A1 A2 A3 A4 A5 15 2.0584E+01 2.4597E-05 4.4584E-08 -1.4799E-09 7.7762E-12 -1.6061E-14 16 -3.9152E+04 5.1386E-05 -7.3235E-08 -2.6736E-10 1.5147E-12 -9.3397E-15

[0074] 10 is a cross-sectional view of the projection lens 40 of Example 3. The projection lens 40 enlarges and projects an image on a display surface such as a liquid crystal panel 29G at a magnification corresponding to the distance to the screen SC. The F-number of the projection lens 40 is 1.61.

[0075] The projection lens 40 includes, in order from the screen SC on the enlargement side, a first lens group G1 with negative refractive power, an aperture stop ST, and a second lens group G2 with positive refractive power, and is approximately telecentric on the reduction side. The aperture stop ST is provided on the lens surface of the second lens group G2.

[0076] The first lens group G1 consists of, from the magnification side, a negative first lens L1g1, a negative second lens L2g1, a negative third lens L3g1, a positive fourth lens L4g1, and a positive fifth lens L5g1. In other words, the first lens group G1 is configured with five lenses, combining negative, negative, negative, positive, and positive refractive powers, from the magnification side. The first lens L1g1 is a single lens consisting of the first lens L11 alone, and is a plastic, aspherical, negative lens. The second lens L2g1 is a negative meniscus single lens consisting of the second lens L12 alone. The third lens L3g1 is a cemented lens combining a biconcave, negative third lens L13 and a biconvex, positive fourth lens L14 alone. The fourth lens L4g1 is a biconvex, positive single lens consisting of the fifth lens L15 alone. The fifth lens L5g1 is a cemented lens that combines a biconvex, positive sixth lens L16 and a biconcave, negative seventh lens L17.

[0077] The second lens group G2 consists of, from the magnification side, a positive first lens L1g2, a negative second lens L2g2, a positive third lens L3g2, a positive fourth lens L4g2, a negative fifth lens L5g2, and a positive sixth lens L6g2. In other words, the second lens group G2 is configured with six lenses, from the magnification side: positive, negative, positive, negative, positive. The first lens L1g2 is a single lens with a positive meniscus shape consisting only of the first lens L21. The second lens L2g1 is a single lens with a glass-molded, biconcave, aspherical negative shape consisting only of the second lens L22. The third lens L3g2 is a single lens with a positive meniscus shape consisting only of the third lens L23. The fourth lens L4g2 is a cemented lens consisting of a biconvex, positive fourth lens L24, a biconcave, negative fifth lens L25, and a biconvex, positive sixth lens L26. The fifth lens L5g2 is a cemented lens that combines a negative meniscus seventh lens L27, a biconvex positive eighth lens L28, and a negative meniscus ninth lens L29. The sixth lens L6g2 is a biconvex positive single lens that consists only of a tenth lens L30.

[0078] During focusing, the first focus group FG1, which is composed only of the second lens L2g1, moves toward the enlargement side and then moves toward the reduction side. The second focus group FG2, which is composed of the third lens L3g1 and the fourth lens L4g1, moves toward the reduction side, and the third focus group FG3, which is composed only of the fifth lens L5g1, moves toward the enlargement side.

[0079] FIG. 11 is a diagram showing the longitudinal aberration characteristics (that is, the spherical aberration characteristics, the astigmatism characteristics, and the distortion characteristics) of the projection lens 40 of the third embodiment.

[0080] FIG. 12 is a diagram showing the lateral aberration characteristics (tangential and sagittal aberration characteristics at three relative image heights of 1.0, 0.5, and 0.1) of the projection lens 40 of Example 3.

[0081] For reference, Table 10 below shows Examples 1 to 3 corresponding to each of the conditional expressions (1) to (7), and Examples 1 to 5 of JP 2014-190999 A as comparative examples. [Table 10] TIFF2025153289000003.tif59166

[0082] [Other matters] The structure described above is an example, and various modifications can be made within the scope of achieving the same function.

[0083] For example, in each embodiment, one or more lenses that have no substantial power can be added before or after the lenses that make up each of the lens groups G1 and G2.

[0084] Furthermore, the object of enlarged projection by the projection lens 40 is not limited to images formed by a liquid crystal panel, but images formed by a light modulation element such as a digital micromirror device can also be enlarged and projected.

[0085] Summary of the Disclosure A summary of this disclosure is provided below.

[0086] (Appendix 1) The lens comprises, in order from the magnification side, a first lens group having positive or negative refractive power, an aperture stop, and a second lens group having positive refractive power; The first lens group includes, in order from the magnification side, a first sub-lens group having a negative refractive index and a second sub-lens group having a positive refractive index, A projection lens that satisfies the following conditions: 0.1<1 / fg1p-1 / fg1m<0.25 … (1) ω>50 … (2) 2.5<(DL1×LL)×F / IH 2 <6.5 … (3) 3.0 <BF / F<5.0 … (4) where: fg1p: composite focal length of the first sub-lens group fg1m: composite focal length of the second sub-lens group ω: Maximum half angle of projection lens IH: Image Circle DL1: Effective radius of the lens closest to the screen LL: Lens length F: Combined focal length of all lenses BF: Back focus distance in air equivalent length In such a projection lens, by appropriately adjusting the negative refractive power of the first sub-lens group in the first lens group and the positive refractive power of the second sub-lens group, the projection lens 40 can achieve both compactness and good correction of various aberrations. In particular, by making the first lens group positive, the overall lens length and effective diameter can be reduced. By satisfying conditional expressions (1) to (4), it is possible to realize a compact lens that has a wide angle of view and good resolving power while ensuring an appropriate back focus. Conditional formula (1) is a formula for realizing a small lens with good resolving power. By setting the value 1 / fg1p-1 / fg1m of the above conditional formula to be equal to or greater than the lower limit, it is possible to achieve a wide angle of view while optimizing the correction of various aberrations, particularly chromatic aberration. By setting the value 1 / fg1p-1 / fg1m of the above conditional formula to be equal to or less than the upper limit, it is possible to achieve a wide angle of view while optimizing the correction of various aberrations, particularly chromatic aberration. Conditional expression (2) expresses the widening of the angle of the projection lens. Conditional formula (3) indicates the lens diameter and overall length relative to the image circle, and is an index for compactness. The value of the above conditional formula is (DL1 × LL) × F / IH 2 By setting F / IH equal to or greater than the lower limit, various aberrations such as curvature of field and distortion can be effectively corrected. 2 By making the value of the upper limit or less, it is possible to prevent the lens diameter from becoming large, thereby achieving cost reduction and size reduction. Conditional expression (4) is an expression for ensuring an appropriate back focus. By setting the value BF / F of the above conditional expression to the lower limit or more, it is possible to ensure space for arranging an insert such as a prism. By setting the value BF / F of the above conditional expression to the upper limit or less, it is possible to realize a lens configuration that provides a wide angle while still effectively correcting various aberrations. (Appendix 2) In the first lens group, a positive lens is disposed closest to the reduction side, In the second lens group, a lens having a negative refractive power is arranged on the most magnifying side, and a positive lens is provided on the reducing side of the lens having the negative refractive power on the most magnifying side. The projection lens according to Appendix 1. As described above, by adopting a positive, negative, and positive lens configuration, more aberration can be reduced. (Appendix 3) The second lens group has at least three positive lenses, and one of the three positive lenses is arranged on the most reducing side of the second lens group. The projection lens according to any one of Appendices 1 and 2. As described above, by arranging the positive lenses in three parts, the occurrence of aberration can be suppressed. In addition, the lens having a positive refractive power arranged on the most reducing side has the effect of making the overall configuration substantially telecentric. (Appendix 4) The second lens group includes at least one aspherical lens having a negative refractive power. The projection lens according to any one of Appendices 1 to 3. Thereby, various aberrations such as field curvature can be suppressed. (Appendix 5) Satisfying the following conditional expressions: The projection lens according to any one of Appendices 1 to 4. 3.1 < nL2g1 × nL3g1 … (5) 0.59 < L2θgf or L3θgf … (6) Here, nL2g1: Refractive index of the second lens from the magnifying side of the first lens group with respect to the d line L2θgf: Partial dispersion value of the second lens nL3g1: Refractive index of the third lens from the magnifying side of the first lens group with respect to the d line L3θgf: Partial dispersion value of the third lens By satisfying conditional expressions (5) and (6), while realizing miniaturization and wide-angleization of the projection lens, suppression of chromatic aberration can be achieved. (Appendix 6) Satisfying the following conditional expressions: 6. The projection lens according to any one of claims 1 to 5. -1.2 <fg1m / F<-1.0 … (7) By setting the value fg1m / F in the above conditional expression to the lower limit or more, it is possible to advantageously suppress various aberrations while ensuring a sufficient back focus.By setting the value fg1m / F in the above conditional expression to the upper limit or less, it is possible to suppress various aberrations while ensuring a sufficient back focus. (Appendix 7) In the first lens group, a single lens or a cemented lens having negative-negative-negative-positive-positive refractive power is arranged in this order from the magnification side, the negative lens closest to the reduction side and at least one of the two positive lenses are cemented lenses; 7. The projection lens according to any one of claims 1 to 6. In this way, by using a cemented lens, chromatic aberration of magnification can be effectively suppressed even in a compact size. (Appendix 8) During focusing, at least two focus lens groups in the first lens group move in the same direction on the optical axis. 8. The projection lens according to any one of claims 1 to 7. This allows focusing while properly correcting the curvature of field when the projection distance is changed. (Appendix 9) a projection lens as set forth in any one of appendices 1 to 8; an image forming unit that forms a projection image on a reduction-side conjugate plane of the projection lens, The image forming unit has a light source device and a light modulation element that modulates light from the light source device. Projection equipment. This allows the projection device equipped with the projection lens to be made smaller. [Explanation of symbols]

[0087] 2...Projection device, 10...Light source device, 20a...Image formation section, 23, 24...Relay lens, 25, 26, 27...Reflecting mirror, 28B, 28G, 28R...Field lens, 29B, 29G, 29R...Liquid crystal panel, 31...Cross dichroic prism, 40...Projection lens, 50...Optical system section, 80...Circuit device, 81...Image processing section, 82...Display drive section, 83...Lens drive section, 88...Main control section, AC...Actuator, FG1 to FG3...Focus lens group, G1, G2...Lens group, G1m, G1p...Sub-lens group, L1g1 to L5g1...Lens, L1g2 to L6g2...Lens, L11 to L17...Lens, L21 to L30...Lens, OA...Optical axis, OM...Light modulation element, PR...Prism, RC...Reduction side conjugate surface, SC...Screen, ST...Aperture diaphragm

Claims

1. The lens comprises, in order from the magnification side, a first lens group having positive or negative refractive power, an aperture stop, and a second lens group having positive refractive power; the first lens group includes, in order from the magnification side, a first sub-lens group having a negative refractive index and a second sub-lens group having a positive refractive index; A projection lens that satisfies the following conditions: 0.1<1 / fg1p-1 / fg1m<0.25... (1) ω>50 … (2) 2.5<(DL1×LL)×F / IH ２ <6.5 … (3) 3.0<BF / F<5.0... (4) where: fg1p: composite focal length of the first sub-lens group fg1m: composite focal length of the second sub-lens group ω: maximum half angle of view of the projection lens IH: Image Circle DL1: Effective radius of the lens closest to the screen LL: Lens total length F: Combined focal length of all lenses BF: Back focus distance in air equivalent length

2. In the first lens group, a positive lens is disposed on the most reduction side, In the second lens group, a lens having a negative refractive power is disposed on the most magnification side, and a positive lens is disposed on the reduction side of the lens having a negative refractive power on the most magnification side.

2. The projection lens according to claim 1.

3. the second lens group has at least three positive lenses, one of which is disposed on the most reduction side of the second lens group; 2. The projection lens according to claim 1.

4. the second lens group includes at least one aspherical lens having negative refractive power; 2. The projection lens according to claim 1.

5. Satisfy the following condition:

2. The projection lens according to claim 1. 3.1 < nL2g1 × nL3g1 … (5) 0.59<L2θgf or L3θgf ... (6) where: nL2g1: the refractive index of the second lens from the magnification side in the first lens group with respect to the d line L2θgf: partial dispersion value of the second lens nL3g1: the refractive index of the third lens from the magnification side in the first lens group with respect to the d line L3θgf: partial dispersion value of the third lens

6. Satisfy the following condition:

2. The projection lens according to claim 1. -1.2<fg1m / F<-1.0... (7)

7. In the first lens group, a single lens or a cemented lens having a negative-negative-negative-positive refractive power is arranged in order from the magnification side, the negative lens located at the most reduction side and at least one of the two positive lenses are cemented lenses; 2. The projection lens according to claim 1.

8. During focusing, at least two or more focus lens groups in the first lens group move in the same direction on the optical axis.

2. The projection lens according to claim 1.

9. A projection lens according to any one of claims 1 to 8; an image forming unit that forms a projection image on a reduction-side conjugate plane of the projection lens, The image forming unit includes a light source device and a light modulation element that modulates light from the light source device. Projection equipment.

Images