Fixed focus lens and projector

Abstract

To more minimize a fixed focus lens.SOLUTION: A fixed focus lens comprises, in order from an enlargement side to contraction side: a first lens group G1 that has positive refractive power; an aperture stop ST; and a second lens group G2 that has the positive refractive power. In the first lens group G1, any of a lens 41 on the most enlargement side and a second lens 42 from the enlargement side is an aspherical surface lens C1, and lenses on the contraction side are telecentric, and the following expression is satisfied. ω>45 (1), 0.15<L1H / LL<0.4 (2), and 2.5<BF / F<3.5 (3) where a value ω is a maximum half-angle of view of the fixed focus lens 40, a value L1H is height of a light ray through which maximum image height passes in a lens surface 41 s on the most enlargement side of the fixed focus lens 40, a value LL is a length of the fixed focus lens 40, a value BF is an air equivalent length back focus, and a value F is a focal length of an entire system of the fixed focus lens 40.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a fixed-focus lens and a projector equipped with a fixed-focus lens. [Background technology]

[0002] A known projection lens consists of, from the magnification side, a first lens group with negative refractive power and a second lens group with positive refractive power, and is approximately telecentric on the reduction side (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-104048 Summary of the Invention [Problem to be solved by the invention]

[0004] The above-mentioned projection lens is an optical system that has a wide angle and relatively good image performance, but the lens length and diameter are large, which causes problems such as poor installation and restrictions on product design and aesthetics. [Means for solving the problem]

[0005] A fixed focus lens according to one aspect of the present invention comprises, in order from the magnification side to the reduction side, a first lens group having positive refractive power, an aperture stop, and a second lens group having positive refractive power, wherein in the first lens group, either the lens closest to the magnification side or the lens second from the magnification side is an aspherical lens, and the reduction side is telecentric, and satisfies the following conditional expression: ω>45 … (1) 0.15 <L1H / LL<0.4 … (2) 2.5 <BF / F<3.5 … (3) Here, the value ω is the maximum half angle of view of the fixed focus lens, the value L1H is the height of the ray of light passing through the maximum image height on the lens surface on the most magnifying side of the fixed focus lens, the value LL is the length of the fixed focus lens, the value BF is the air-equivalent back focus length, and the value F is the focal length of the entire fixed focus lens system.

[0006] A projector according to one aspect of the present invention includes an image forming unit having a light modulation element that modulates light from a light source device to form image light, and the above-described fixed focus lens that projects the image light from the image forming unit. [Brief explanation of the drawings]

[0007] [Figure 1] 1A and 1B are diagrams illustrating a projector including a fixed focus lens according to an embodiment. [Figure 2] 1A and 1B are diagrams showing the configuration and light rays of a fixed focus lens according to an embodiment of the present invention; [Figure 3] 1A and 1B are diagrams illustrating a state in which a fixed focus lens of an embodiment projects onto a screen. [Figure 4] 1 is a diagram illustrating a configuration of a fixed focus lens according to a first embodiment. [Figure 5] 4 shows longitudinal aberration characteristics of the fixed focus lens of Example 1. [Figure 6] FIG. 10 is a diagram illustrating the configuration of a fixed focus lens according to a second embodiment. [Figure 7] 10 shows longitudinal aberration characteristics of the fixed focus lens of Example 2. [Figure 8] FIG. 10 is a diagram illustrating the configuration of a fixed focus lens according to a third embodiment. [Figure 9] 10 shows longitudinal aberration characteristics of the fixed focus lens of Example 3. [Figure 10] FIG. 10 is a diagram illustrating the configuration of a fixed focus lens according to a fourth embodiment. [Figure 11] 10 shows longitudinal aberration characteristics of the fixed focus lens of Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Embodiment] A fixed focus lens 40 according to an embodiment of the present invention and a projector 2 incorporating the same will be described below with reference to the drawings.

[0009] As shown in FIG. 1, a projector 2 incorporating a fixed focus lens 40 according to the embodiment includes an optical system section 60 that projects image light, and a circuit device 80 that controls the operation of the optical system section 60.

[0010] In the optical system section 60, 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 fixed focus lens 40.

[0014] Fixed-focus lens 40 is a projection lens that enlarges and projects image light modulated by each liquid crystal panel 29R, 29G, and 29B and combined by cross dichroic prism 31 onto screen SC (not shown). Liquid crystal panels 29R, 29G, and 29B form image forming unit 20a that forms a projection image on reduction-side conjugate plane RC (see FIG. 2, which will be described later) of fixed-focus 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 liquid crystal panels 29R, 29G, and 29B provided in the optical system unit 60 based on the output of the image processing unit 81, and a main control unit 88 that comprehensively controls the operation of these circuit units 81, 82, 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 fixed focus lens 40 of the embodiment will be specifically described below with reference to Fig. 2 and Fig. 3. Fig. 2 shows the configuration and ray diagram of the fixed focus lens 40 of the embodiment. Fig. 3 is a diagram showing the projection state onto the screen SC of the fixed focus lens 40 of the embodiment. The fixed focus lens 40 illustrated in Fig. 2 has the same configuration as the fixed focus lens 40 of Example 1, which will be described later.

[0019] Fixed-focus lens 40 of the embodiment projects an image formed on the projection surface of liquid crystal panel 29G (29R, 29B) onto screen SC. Here, a prism PR corresponding to cross dichroic prism 31 in FIG. 1 is disposed between fixed-focus lens 40 and liquid crystal panel 29G (29R, 29B).

[0020] The fixed-focus lens 40 is composed of, in order from the enlargement side (screen SC) to the reduction side, a first lens group G1 with positive refractive power, an aperture stop ST, and a second lens group G2 with positive refractive power. By making the refractive power of the first lens group G1 positive, the overall length and maximum diameter of the fixed-focus lens 40 can be reduced.

[0021] The fixed-focus lens 40 is telecentric on the object side or reduction side where the liquid crystal panels 29G (29R, 29B) are located. This increases the light utilization efficiency when the light modulated by each liquid crystal panel 29G (29R, 29B) is combined in the cross dichroic prism 31 to generate image light, and makes it easier to absorb variations in assembly. Note that telecentricity also includes the case of being approximately telecentric, in which the chief ray is approximately parallel to the optical axis OA.

[0022] The first lens group G1 is composed of, from the reduction side, lenses 45-41 having positive, positive, negative, negative, and negative refractive powers. The lenses 45-41 are single lenses or cemented lenses. Specifically, from the magnification side, the first lens group G1 is composed of, from the magnification side, a first lens 41 having negative refractive power, a second lens 42 having negative refractive power, a third lens 43 having negative refractive power, a fourth lens 44 having positive refractive power, and a fifth lens 45 having positive refractive power. The first lens group G1 is configured with multiple negative lenses 41n-43n arranged on the magnification side to spread light rays toward the magnification side. Furthermore, the first lens group G1 is configured with multiple positive lenses 44p, 45p arranged on the reduction side to achieve compactness. Here, a configuration in which the first lens group G1 has a stronger positive power is more suitable for a compact configuration, but this is not preferable because it generates aberrations. In this configuration, by arranging two positive lenses side by side on the reduction side, the amount of aberration generated per positive lens is reduced, making it possible to reduce the size.

[0023] In the first lens group G1, either the first lens 41, which is closest to the magnification side, or the second lens 42, which is second from the magnification side, is an aspherical lens C1. By using the aspherical lens C1 for either the lens 41, 42, which is closest to the magnification side or second from the magnification side, it is possible to achieve both correction of field curvature and distortion and compactness.

[0024] The lenses 41 to 45 that make up the first lens group G1 are made of glass or plastic. The aspherical lens C1 of the first lens group G1 is preferably made of plastic from the standpoints of weight reduction and ease of processing. However, the aspherical lens C1 may also be made of glass.

[0025] In the example of FIG. 2, the first lens 41 is, for example, a negative lens 41n made of a single lens, and is arranged on the most magnification side. The first lens 41 is an aspherical lens C1 made of plastic. The second lens 42 is, for example, a negative lens 42n made of a single lens. The third lens 43 is, for example, a negative lens 43n made of a cemented lens 43u. The cemented lens 43u is, for example, composed of a combination of a negative lens 43a and a positive lens 43b, from the magnification side. The fourth lens 44 is, for example, a positive lens 44p made of a cemented lens 44u. The cemented lens 44u is, for example, composed of a combination of a positive lens 44a and a negative lens 44b, from the magnification side. The fifth lens 45 is, for example, a positive lens 45p made of a single lens.

[0026] It is desirable that the fixed-focus lens 40 performs focusing by moving one or two of the lenses 41 to 45 in the first lens group G1 in the direction of the optical axis OA.

[0027] The second lens group G2 is composed of, from the magnification side, lenses 51 to 54, 59 having negative, positive, positive, negative, and positive refractive powers or powers. The lenses 51 to 54, 59 are single lenses or cemented lenses. Specifically, the second lens group G2 is composed of, from the magnification side, a sixth lens 51 having negative refractive power, a seventh lens 52 having positive refractive power, an eighth lens 53 having positive refractive power, a ninth lens 54 having negative refractive power, and a tenth lens 59 having positive refractive power. Because the first lens group G1 has positive refractive power, the second lens group G2 corrects aberrations by making the sixth lens 51 on the magnification side closest to the first lens group G1 a negative lens 51n. For compactness, it is preferable to arrange a lens with strong positive refractive power near the aperture stop ST in the second lens group G2. However, if a single lens has positive power, aberration correction becomes difficult. For this reason, the seventh lens 52 and the eighth lens 53 in the second lens group G2, which are located near the aperture stop ST, are arranged with divided positive power. A tenth lens 59 with positive refractive power is located on the reduction side of the second lens group G2 to ensure telecentricity. The tenth lens 59, located closest to the reduction side, may be a positive lens group 59g, and may be composed of multiple single lenses, multiple cemented lenses, or a combination of single lenses and cemented lenses, as long as it has positive refractive power overall. Furthermore, to correct aberrations that become necessary due to the addition of the tenth lens 59, a ninth lens 54 with negative refractive power is located on the magnification side of the tenth lens 59 in the second lens group G2.

[0028] The second lens group G2 includes an aspherical lens C2 with positive refractive power, which effectively suppresses astigmatism and enables a smaller lens diameter and lower costs than when the second lens group G2 is composed of only spherical lenses.

[0029] The sixth lens 51 in the second lens group G2, which is closest to the magnification side, is a negative cemented lens 51u made up of lenses 51a and 51b having positive and negative refractive powers, which enables the fixed-focus lens 40 to achieve a wider angle of view, a smaller size, and reduced chromatic aberration.

[0030] The lenses 51 to 54 and 59 that make up the second lens group G2 are made of glass or plastic. The aspherical lens C2 of the second lens group G2 is preferably made of glass from the standpoints of light resistance and component costs. However, the aspherical lens C2 may also be made of plastic.

[0031] In the example of FIG. 2, the sixth lens 51 is a negative lens 51n, for example, made up of a cemented lens 51u, and is located on the magnification side, i.e., the side closest to the aperture stop ST. The cemented lens 51u is, from the magnification side, for example, a combination of a positive lens 51a and a negative lens 51b. The seventh lens 52 is, for example, a positive lens 52p made up of a single lens, and is an aspherical glass lens C2. The eighth lens 53 is, for example, a positive lens 53p made up of a single lens. The ninth lens 54 is, for example, a negative lens 54n made up of a cemented lens 54u. The cemented lens 54u is, from the magnification side, for example, a combination of a negative lens 54a and a positive lens 54b. The tenth lens 59 is, for example, a positive lens 59p made up of a single lens. Specifically, the tenth lens 59 is, for example, a positive lens 55 and a positive lens 56. The tenth lens 59 in FIG. 2 can also be considered a positive lens group 59g, consisting of two positive single lenses arranged side by side. The tenth lens 59 may be configured, for example, as a single lens or a cemented lens.

[0032] The aperture stop ST is a surface for defining the F-number and is a surface that is placed at a position where the chief ray passes through the optical axis OA. The aperture stop ST may or may not be an opening member that actually blocks light as a stop.

[0033] The fixed focus lens 40 of the embodiment satisfies the following conditional expressions. ω>45 … (1) Here, the value ω is the maximum half angle of view of the fixed focus lens 40. Conditional expression (1) expresses the widening of the angle of view of the fixed focus lens 40.

[0034] The fixed focus lens 40 of the embodiment satisfies the following conditional expressions. 0.15 <L1H / LL<0.4 … (2) Here, the value L1H is the height of the ray of light through which the maximum image height passes at the most magnification-side lens surface of the fixed focus lens 40, specifically, the magnification-side lens surface 41s of the first lens 41, and the value LL is the length of the fixed focus lens 40.

[0035] Conditional expression (2) is an expression for reducing the size of the fixed-focus lens 40 in the height direction, that is, reducing the lens diameter. By setting the value L1H / LL of the above conditional expression to be equal to or greater than the lower limit, it is possible to achieve size reduction in the height direction while effectively correcting field curvature and distortion. By setting the value L1H / LL of the above conditional expression to be equal to or less than the upper limit, it is possible to prevent the fixed-focus lens 40 from increasing in height, and to satisfy the required product height.

[0036] The fixed focus lens 40 of the embodiment satisfies the following conditional expressions. 2.5 <BF / F<3.5 … (3) Here, the value BF is the air-equivalent back focal length, and the value F is the focal length of the entire fixed-focus lens 40 system.

[0037] Conditional expression (3) is an expression for ensuring an appropriate back focus. By setting the value BF / F of the above conditional expression to be equal to or greater than the lower limit, it is possible to ensure the length necessary for placing an insert such as a prism PR. By setting the value BF / F of the above conditional expression to be equal to or less than the upper limit, it is possible to satisfy the requirements for a reduced lens length and a wider angle of view of the fixed-focus lens 40.

[0038] The fixed focus lens 40 of the embodiment satisfies the following conditional expressions. 3.0 <Fg1p / F<25.0 … (4) Here, the value Fg1p is the focal length of the lens in the first lens group G1 that is closest to the reduction side, specifically the fifth lens 45, and the value F is the focal length of the entire fixed focus lens system.

[0039] Conditional expression (4) is an expression for reducing the size and correcting aberrations of the fixed-focus lens 40. By setting the value Fg1p / F of the above conditional expression to be equal to or greater than the lower limit, it is possible to maintain size reduction while favoring aberration correction. By setting the value Fg1p / F of the above conditional expression to be equal to or less than the upper limit, it is possible to achieve size reduction while favoring aberration correction.

[0040] The fixed focus lens 40 of the embodiment satisfies the following conditional expressions. 0.2 <Fg2p1 / Fg2p2<1.2 … (5) Here, the value Fg2p1 is the focal length of the positive single lens or positive cemented lens arranged closest to the magnification side in the second lens group G2, specifically the seventh lens 52, and the value Fg2p2 is the focal length of the positive single lens or positive cemented lens arranged second closest to the magnification side in the second lens group G2, specifically the eighth lens 53.

[0041] Conditional expression (5) expresses the power distribution of the two positive lenses arranged on the magnification side in the second lens group G2. By satisfying conditional expression (5), it is possible to effectively correct various aberrations caused by the downsizing and widening of the angle of view of the fixed-focus lens 40.

[0042] The fixed focus lens 40 of the embodiment satisfies the following conditional expressions. 0.8<|Fg2n1 / Fg2p3-|<2.8 … (6) Here, the value Fg2n1 is the focal length of the negative single lens or negative cemented lens arranged closest to the reduction side in the second lens group G2, specifically the ninth lens 54, and the value Fg2p3- is the focal length of the negative single lens or negative cemented lens arranged closest to the reduction side in the second lens group G2, specifically the positive lens arranged closer to the reduction side than the ninth lens 54, specifically the tenth lens 59. The positive lens arranged on the reduction side is composed of one or more single lenses or cemented lenses.

[0043] Conditional expression (6) is an expression for correcting telecentricity and lateral chromatic aberration. By setting the value Fg2n1 / Fg2p3- of the above conditional expression to be equal to or greater than the lower limit, telecentricity can be ensured. By setting the value Fg2n1 / Fg2p3- of the above conditional expression to be equal to or less than the upper limit, lateral chromatic aberration can be effectively corrected.

[0044] The fixed focus lens 40 of the embodiment satisfies the following conditional expressions. 0.45 <LS / LL<0.65 … (7) Here, the value LS is the distance from the lens surface on the most enlargement side of the fixed focus lens 40, specifically the lens surface 41s of the first lens 41, to the aperture stop ST, and the value LL is the length of the fixed focus lens 40.

[0045] Conditional expression (7) relates to the reduction of the lens diameter and telecentricity. By setting the value LS / LL of the above conditional expression to the lower limit or more, telecentricity can be ensured. By setting the value LS / LL of the above conditional expression to the upper limit or less, the reduction of the lens diameter can be achieved.

[0046] The fixed-focus lens 40 described above is composed of, in order from the enlargement side to the reduction side, a first lens group G1 having positive refractive power, an aperture stop ST, and a second lens group G2 having positive refractive power. In the first lens group G1, the lens closest to the enlargement side or either the lens 41 or 42 second from the enlargement side is an aspherical lens C1, and the reduction side is telecentric, satisfying the following conditional expression: ω>45 … (1) 0.15 <L1H / LL<0.4 … (2) 2.5 <BF / F<3.5 … (3) Here, the value ω is the maximum half angle of view of fixed-focus lens 40, the value L1H is the height of the ray of light passing through the maximum image height on the lens surface on the most magnifying side of fixed-focus lens 40, the value LL is the length of fixed-focus lens 40, the value BF is the air-equivalent back focus length, and the value F is the focal length of the entire fixed-focus lens 40 system.

[0047] In the fixed focus lens 40, the refractive power of the first lens group G1 is made positive, thereby making it possible to reduce the overall length and maximum diameter of the fixed focus lens 40. The lenses 41 and 42 on the most enlargement side or the second from the enlargement side are aspherical lenses C1, making it possible to correct field curvature and distortion while also achieving compactness.

[0048] Conditional formula (1) expresses the widening of the angle of view of the fixed-focus lens 40. Conditional formula (2) expresses the need to reduce the size of the fixed-focus lens 40 in the height direction. By setting the value L1H / LL in the above conditional formula to the lower limit or more, it is possible to achieve a reduction in size in the height direction while effectively correcting field curvature and distortion. By setting the value L1H / LL in the above conditional formula to the upper limit or less, it is possible to prevent the fixed-focus lens 40 from increasing in height, thereby satisfying the required product height. Conditional formula (3) expresses the need to ensure an appropriate back focus. By setting the value BF / F in the above conditional formula to the lower limit or more, it is possible to ensure the length necessary to place an insert such as a prism PR. By setting the value BF / F in the above conditional formula to the upper limit or less, it is possible to reduce the lens length of the fixed-focus lens 40 and achieve a wide angle of view.

[0049] As described above, fixed-focus lens 40 is a compact projection lens that is bright and provides high image quality despite its wide angle of view. In other words, fixed-focus lens 40 achieves both a wide angle of view of 90 degrees or more and a compact size, and can effectively correct various aberrations. This allows for a smaller product size and reduced costs without sacrificing resolution.

[0050] The projector 2 described above includes the image forming unit 20a having the light modulation element OM that forms image light by modulating light from the light source device 10, and the fixed-focus lens 40 described above that projects the image light from the image forming unit 20a. This makes it possible to reduce the size of the projector 2 that includes the fixed-focus lens 40.

[0051] [Example] The following describes examples of the fixed focus lens 40. The meanings of the specifications common to Examples 1 to 4 described below are summarized below. F: Fixed focal length of lens 40 Fno: F number IH: Maximum image height of lens TTL: Distance from the most magnifying lens surface 41s of the fixed-focus lens 40 to the original image LL: Length of the fixed focus lens 40 (the distance from the most magnifying lens surface 41s of the fixed focus lens 40 to the final surface) BF: Air-equivalent back focus length LS: distance from the most enlarged lens surface 41s of the fixed focus lens 40 to the aperture stop ST L1H: the height of the ray of light passing through the lens surface 41s on the most enlarged side of the fixed-focus lens 40, at which the maximum image height passes FG1: Focal length of the first lens group G1 FG2: Focal length of the second lens group G2 R: paraxial radius of curvature D: Axial distance (lens thickness or lens spacing) Nd: Refractive index of d line (reference wavelength 588 nm) Vd: Abbe number of d line (reference wavelength 588 nm)

[0052] The displacement amount z of the aspherical surface is specified by the following polynomial (aspherical surface equation): TIFF2025139225000002.tif16166However, c: Curvature (1 / R) h: Height from the optical axis OA k: conic constant of the aspheric surface Ai: ith aspherical coefficient In the tables of each example, surface number 0 indicates the image surface (projection surface) on the screen SC, "ST" indicates the aperture stop ST, "INF" indicates infinity, and the final surface number indicates the display surface of the liquid crystal panel 29G, etc. Furthermore, surfaces with an "*" after the surface number are aspherical surfaces.

[0053] Example 1 The overall specifications of the fixed focus lens 40 of the first embodiment are shown below. F=7.733(mm) Fno=1.787 IH=11.000(mm) TTL=143.235(mm) LL=108.290(mm) BF=25.729(mm) LS=54.091(mm) L1H=17.778(mm) FG1=100.000(mm) FG2=28.467(mm)

[0054] The lens surface data for Example 1 is shown in Table 1 below. [Table 1] Surface number RD Nd Vd 0 inf 970.00 1* -8.01 3.00 1.5350 55.7 2* -15.20 3.35 3 33.48 1.50 1.9108 35.3 4 15.14 9.97 5 -25.11 0.90 1.9534 31.3 6 23.27 9.00 1.8052 25.5 7 -28.25 1.09 8 157.09 9.00 1.6477 33.9 9 -14.71 0.90 1.9108 35.3 10 -43.95 3.87 11 -208.19 9.00 1.7080 27.0 12 -35.88 2.50 13(ST) inf 2.67 14 -70.32 9.00 1.8720 19.4 15 -17.76 0.90 1.9537 32.3 16 46.53 0.52 17* 21.93 7.69 1.5158 64.0 18* -23.50 0.25 19 -163.74 5.27 1.4875 70.2 20 -23.13 1.00 21 -50.58 1.00 1.9533 31.0 22 19.88 7.41 1.4970 81.6 23 -70.37 0.25 24 58.92 9.00 1.4970 81.5 25 -32.51 0.25 26 200.00 9.00 1.4970 81.6 27 -45.21 2.00 28 inf 27.05 1.5168 64.2 29 inf 5.89 30 inf 0.00

[0055] Table 2 below shows the aspheric coefficients of the lens surfaces of Example 1. In Table 2 and the following tables, powers of 10 (for example, 1.00×10 +18 ) is expressed using E (for example, 1.00E+18). [Table 2] Aspheric coefficients Face number: 1 K A3 A4 A5 A6 A7 A8 A9 A10 -3.58126E+00 2.88609E-03 1.03740E-04 -3.32812E-05 2.26227E-06 -6.15336E-08 3.30677E-11 3.16484E-11 -4.49379E-13 Face number: 2 K A3 A4 A5 A6 A7 A8 A9 A10 -2.33776E+00 1.65997E-03 8.35030E-04 -1.03708E-04 6.58898E-06 -4.24075E-07 2.97433E-08 -1.24458E-09 1.92977E-11 Face number: 17 K A4 A6 A8 A10 0.00000E+00 -1.91954E-05 2.11260E-08 -3.87908E-10 1.33369E-12 Face number: 18 K A4 A6 A8 A10 -9.75759E+00 -5.74762E-05 5.03735E-07 -2.27919E-09 5.16313E-12

[0056] Fig. 4 is a cross-sectional view of a fixed focus lens 40 of Example 1. The fixed focus lens 40 shown in Fig. 4 corresponds to the fixed focus lens 40 of the embodiment.

[0057] The fixed-focus lens 40 enlarges and projects an image on a display surface such as the liquid crystal panel 29G onto the screen SC (see FIG. 3). The fixed-focus lens 40 includes, in order from the screen SC on the enlargement side, a first lens group G1 with positive refractive power, an aperture stop ST, and a second lens group G2 with positive refractive power. A prism PR is disposed between the second lens group G2 and the liquid crystal panel 29G. The fixed-focus lens 40 is approximately telecentric on the reduction side.

[0058] The first lens group G1 is composed of, in order from the magnification side, a first lens 41, a second lens 42, a third lens 43, a fourth lens 44, and a fifth lens 45. The first lens 41 is a plastic negative aspherical lens C1 (negative lens 41n). The second lens 42 is a negative meniscus lens (negative lens 42n). The third lens 43 is a negative cemented lens 43u (negative lens 43n) consisting of a biconcave lens (negative lens 43a) and a biconvex lens (positive lens 43b). The fourth lens 44 is a positive cemented lens 44u (positive lens 44p) consisting of a biconvex lens (positive lens 44a) and a negative meniscus lens (negative lens 44b). The fifth lens 45 is a positive meniscus lens (positive lens 45p).

[0059] The second lens group G2 consists of, in order from the magnification side, a sixth lens 51, a seventh lens 52, an eighth lens 53, a ninth lens 54, and a tenth lens 59. The sixth lens 51 is a negative cemented lens 51u (negative lens 51n) consisting of a positive meniscus lens (positive lens 51a) and a biconcave lens (negative lens 51b). The seventh lens 52 is a biconvex aspherical lens C2 (positive lens 52p) made of glass. The eighth lens 53 is a positive meniscus lens (positive lens 53p). The ninth lens 54 is a negative cemented lens 54u (negative lens 54n) consisting of a biconcave lens (negative lens 54a) and a biconvex lens (positive lens 54b). The tenth lens 59 is composed of a positive lens group 59g, which includes a biconvex lens (positive lens 59p or positive lens 55) and a biconvex lens (positive lens 59p or positive lens 56).

[0060] FIG. 5 is a diagram showing longitudinal aberration characteristics (that is, spherical aberration characteristics, astigmatism characteristics, and distortion characteristics) of the fixed focus lens 40 of Example 1.

[0061] Example 2 The overall specifications of the fixed focus lens 40 of the second embodiment are shown below. F=7.663(mm) Fno=1.785 IH=11.000(mm) TTL=118.514(mm) LL=83.569(mm) BF=25.730(mm) LS=44.165(mm) L1H=22.585(mm) FG1=100.000(mm) FG2=25.123(mm)

[0062] The lens surface data for Example 2 is shown in Table 3 below. [Table 3] Surface number RD Nd Vd 0 inf 970.00 1* -7.55 3.42 1.5350 55.7 2* -12.68 9.55 3 37.85 1.50 1.9537 32.3 4 13.92 9.94 5 -22.44 0.90 1.9537 32.3 6 -33.60 2.31 1.7454 23.4 7 -28.16 1.08 8 -1394.43 5.78 1.6690 28.0 9 -11.95 0.90 1.9537 32.3 10 -32.48 3.44 11 80.96 2.84 1.9459 18.0 12 -64.39 2.50 13(ST) inf 2.50 14 -47.16 3.29 1.9127 18.6 15 -17.50 0.90 1.9537 32.3 16 45.77 1.22 17* 24.21 6.13 1.5158 64.0 18* -25.76 0.25 19 -194.36 3.68 1.4875 70.2 20 -31.13 1.00 21 -125.92 1.00 1.9505 24.2 22 18.81 6.76 1.4970 81.6 23 -66.61 0.25 24 68.16 5.49 1.4970 81.6 25 -42.99 0.25 26 39.07 6.68 1.4970 81.6 27 -57.15 2.00 28 inf 27.05 1.5168 64.2 29 inf 5.85 30 inf 0.04

[0063] Table 4 below shows the aspheric coefficients of the lens surfaces of Example 2. [Table 4] Aspheric coefficients Face number: 1 K A3 A4 A5 A6 A7 A8 A9 A10 -3.11235E+00 2.73650E-03 1.03311E-04 -3.36563E-05 2.29126E-06 -6.12689E-08 1.06250E-11 3.07311E-11 -4.32293E-13 Face number: 2 K A3 A4 A5 A6 A7 A8 A9 A10 -1.37283E+00 1.75145E-03 8.24746E-04 -1.04177E-04 6.59256E-06 -4.22368E-07 2.98700E-08 -1.23958E-09 1.93863E-11 Face number: 17 K A4 A6 A8 A10 0.00000E+00 -9.56393E-06 -4.89389E-08 1.74357E-10 2.22868E-13 Face number: 18 K A4 A6 A8 A10 -1.07408E+01 -6.26705E-05 4.29080E-07 -2.33075E-09 7.04869E-12

[0064] FIG. 6 is a cross-sectional view of a fixed focus lens 40 according to the second embodiment.

[0065] The fixed-focus lens 40 enlarges and projects an image on a display surface such as the liquid crystal panel 29G onto the screen SC (see FIG. 3). The fixed-focus lens 40 includes, in order from the screen SC on the enlargement side, a first lens group G1 with positive refractive power, an aperture stop ST, and a second lens group G2 with positive refractive power. A prism PR is disposed between the second lens group G2 and the liquid crystal panel 29G. The fixed-focus lens 40 is approximately telecentric on the reduction side.

[0066] The first lens group G1 consists of, in order from the magnification side, a first lens 41, a second lens 42, a third lens 43, a fourth lens 44, and a fifth lens 45. The first lens 41 is a plastic negative aspherical lens C1 (negative lens 41n). The second lens 42 is a negative meniscus lens (negative lens 42n). The third lens 43 is a negative cemented lens 43u (negative lens 43n) consisting of a negative meniscus lens (negative lens 43a) and a positive meniscus lens (positive lens 43b). The fourth lens 44 is a positive cemented lens 44u (positive lens 44p) consisting of a positive meniscus lens (positive lens 44a) and a negative meniscus lens (negative lens 44b). The fifth lens 45 is a biconvex lens (positive lens 45p).

[0067] The second lens group G2 consists of, in order from the magnification side, a sixth lens 51, a seventh lens 52, an eighth lens 53, a ninth lens 54, and a tenth lens 59. The sixth lens 51 is a negative cemented lens 51u (negative lens 51n) consisting of a positive meniscus lens (positive lens 51a) and a biconcave lens (negative lens 51b). The seventh lens 52 is a biconvex aspherical lens C2 (positive lens 52p) made of glass. The eighth lens 53 is a positive meniscus lens (positive lens 53p). The ninth lens 54 is a negative cemented lens 54u (negative lens 54n) consisting of a biconcave lens (negative lens 54a) and a biconvex lens (positive lens 54b). The tenth lens 59 is composed of a positive lens group 59g, which includes a biconvex lens (positive lens 59p or positive lens 55) and a biconvex lens (positive lens 59p or positive lens 56).

[0068] FIG. 7 is a diagram showing longitudinal aberration characteristics (that is, spherical aberration characteristics, astigmatism characteristics, and distortion characteristics) of the fixed focus lens 40 of Example 2.

[0069] Example 3 The overall specifications of the fixed focus lens 40 of the third embodiment are shown below. F=7.723(mm) Fno=1.770 IH=11.000(mm) TTL=138.779(mm) LL=103.834(mm) BF=25.433(mm) LS=58.044(mm) L1H=20.478(mm) FG1=100.000(mm) FG2=29.427(mm)

[0070] The lens surface data for Example 3 is shown in Table 5 below. [Table 5] Surface number RD Nd Vd 0 inf 970.00 1* -8.34 3.16 1.5350 55.7 2* -15.43 6.44 3 40.44 1.50 1.9108 35.3 4 16.25 10.95 5 -23.58 0.90 1.9528 29.4 6 20.05 10.05 1.8052 25.5 7 -26.52 1.52 8 43.41 7.68 1.6477 33.9 9 -17.17 1.50 1.9108 35.3 10 -48.02 4.32 11 -26.39 7.53 1.6089 34.4 12 -22.87 2.50 13(ST) inf 2.50 14 -140.97 7.80 1.7190 24.7 15 -15.20 1.20 1.9532 30.6 16 -87.61 1.86 17* -488.26 6.75 1.5831 59.5 18* -23.13 0.36 19 -1274.80 6.18 1.4875 70.2 20 -18.96 1.00 21 -24.81 0.90 1.9536 31.9 22 27.02 8.12 1.4970 81.6 23 -28.05 0.25 24 49.94 8.86 1.4970 81.6 25 -27.91 2.00 26 inf 27.92 1.5168 64.2 27 inf 5.06 28 inf -0.04

[0071] Table 6 below shows the aspheric coefficients of the lens surfaces of Example 3. [Table 6] Aspheric coefficients Face number: 1 K A3 A4 A5 A6 A7 A8 A9 A10 -3.99905E+00 1.72316E-03 2.76621E-04 -4.66566E-05 2.70660E-06 -6.15956E-08 -3.21503E-10 3.86939E-11 -4.87810E-13 Face number: 2 K A3 A4 A5 A6 A7 A8 A9 -4.65649E+00 8.09638E-04 8.66766E-04 -1.07594E-04 6.72218E-06 -4.26697E-0 7 2.98113E-08 -1.22653E-09 1.91291E-11 Face number: 17 K A4 A6 A8 A10 0.00000E+00 -1.11194E-06 -1.60113E-08 8.69281E-10 -7.60260E-12 Face number: 18 K A4 A6 A8 A10 -7.64631E+00 -4.42317E-05 3.00047E-07 -2.71940E-10 -2.16604E-12

[0072] FIG. 8 is a cross-sectional view of a fixed focus lens 40 according to a third embodiment.

[0073] The fixed-focus lens 40 enlarges and projects an image on a display surface such as the liquid crystal panel 29G onto the screen SC (see FIG. 3). The fixed-focus lens 40 includes, in order from the screen SC on the enlargement side, a first lens group G1 with positive refractive power, an aperture stop ST, and a second lens group G2 with positive refractive power. A prism PR is disposed between the second lens group G2 and the liquid crystal panel 29G. The fixed-focus lens 40 is approximately telecentric on the reduction side.

[0074] The first lens group G1 is composed of, in order from the magnification side, a first lens 41, a second lens 42, a third lens 43, a fourth lens 44, and a fifth lens 45. The first lens 41 is a plastic negative aspherical lens C1 (negative lens 41n). The second lens 42 is a negative meniscus lens (negative lens 42n). The third lens 43 is a negative cemented lens 43u (negative lens 43n) consisting of a biconcave lens (negative lens 43a) and a biconvex lens (positive lens 43b). The fourth lens 44 is a positive cemented lens 44u (positive lens 44p) consisting of a biconvex lens (positive lens 44a) and a negative meniscus lens (negative lens 44b). The fifth lens 45 is a positive meniscus lens (positive lens 45p).

[0075] The second lens group G2 consists of, in order from the magnification side, a sixth lens 51, a seventh lens 52, an eighth lens 53, a ninth lens 54, and a tenth lens 59. The sixth lens 51 is a negative cemented lens 51u (negative lens 51n) consisting of a positive meniscus lens (positive lens 51a) and a negative meniscus lens (negative lens 51b). The seventh lens 52 is a glass positive meniscus aspheric lens C2 (positive lens 52p). The eighth lens 53 is a positive meniscus lens (positive lens 53p). The ninth lens 54 is a negative cemented lens 54u (negative lens 54n) consisting of a biconcave lens (negative lens 54a) and a biconvex lens (positive lens 54b). The tenth lens 59 is a positive lens group 59g consisting of a biconvex lens (positive lens 59p or positive lens 55).

[0076] FIG. 9 is a diagram showing longitudinal aberration characteristics (that is, spherical aberration characteristics, astigmatism characteristics, and distortion characteristics) of the fixed focus lens 40 of Example 3.

[0077] Example 4 The overall specifications of the fixed focus lens 40 of the fourth embodiment are shown below. F=7.721(mm) Fno=1.770 IH=11.000(mm) TTL=125.559(mm) LL=90.614(mm) BF=25.433(mm) LS=53.086(mm) L1H=18.638(mm) FG1=18.593(mm) FG2=28.872(mm)

[0078] The lens surface data for Example 4 is shown in Table 7 below. [Table 7] Surface number RD Nd Vd 0 inf 970.00 1* -8.36 3.00 1.5350 55.7 2* -14.06 3.88 3 58.16 1.50 1.9435 35.3 4 15.18 13.09 5 -17.50 0.90 1.6087 63.6 6 61.49 7.71 1.7958 26.6 7 -33.77 1.13 8 66.42 7.65 1.6462 30.0 9 -14.59 1.50 1.9290 33.5 10 -58.48 4.69 11 41.73 5.52 1.5096 68.9 12 -27.65 2.50 13(ST) inf 2.50 14 -35.21 4.85 1.8091 21.1 15 -13.72 1.20 1.9441 32.8 16 62.50 0.83 17* 29.00 5.14 1.5831 59.5 18* -26.71 0.46 19 -71.15 4.73 1.4875 70.2 20 -18.56 1.00 21 -42.67 0.90 1.9350 32.9 22 23.07 7.78 1.4970 81.6 23 -28.86 0.25 24 47.10 7.89 1.4970 81.6 25 -28.01 2.00 26 inf 27.92 1.5168 64.2 27 inf 5.05 28 inf -0.03

[0079] Table 8 below shows the aspheric coefficients of the lens surfaces of Example 4. [Table 8] Aspheric coefficients Face number: 1 K A3 A4 A5 A6 A7 A8 A9 A10 -3.39154E+00 2.15602E-03 2.41356E-04 -4.48586E-05 2.70605E-06 -6.28296E-08 -3.61127E-10 3.98374E-11 -4.36008E-13 Face number: 2 K A3 A4 A5 A6 A7 A8 A9 A10 -1.60057E+00 9.94345E-04 8.85844E-04 -1.05953E-04 6.67814E-06 -4.30964E-07 2.95958E-08 -1.23045E-09 1.99243E-11 Face number: 17 K A4 A6 A8 A10 0.00000E+00 -5.57911E-0 6 6.47592E-08 -8.97472E-11 2.45827E-13 Face number: 18 K A4 A6 A8 A10 -9.64465E+00 -7.34991E-06 3.68708E-07 -9.53547E-10 1.54239E-12

[0080] FIG. 10 is a cross-sectional view of a fixed focus lens 40 according to a fourth embodiment.

[0081] The fixed-focus lens 40 enlarges and projects an image on a display surface such as the liquid crystal panel 29G onto the screen SC (see FIG. 3). The fixed-focus lens 40 includes, in order from the screen SC on the enlargement side, a first lens group G1 with positive refractive power, an aperture stop ST, and a second lens group G2 with positive refractive power. A prism PR is disposed between the second lens group G2 and the liquid crystal panel 29G. The fixed-focus lens 40 is approximately telecentric on the reduction side.

[0082] The first lens group G1 consists of, in order from the magnification side, a first lens 41, a second lens 42, a third lens 43, a fourth lens 44, and a fifth lens 45. The first lens 41 is a plastic negative aspherical lens C1 (negative lens 41n). The second lens 42 is a negative meniscus lens (negative lens 42n). The third lens 43 is a negative cemented lens 43u (negative lens 43n) consisting of a biconcave lens (negative lens 43a) and a biconvex lens (positive lens 43b). The fourth lens 44 is a positive cemented lens 44u (positive lens 44p) consisting of a biconvex lens (positive lens 44a) and a negative meniscus lens (negative lens 44b). The fifth lens 45 is a biconvex lens (positive lens 45p).

[0083] The second lens group G2 consists of, in order from the magnification side, a sixth lens 51, a seventh lens 52, an eighth lens 53, a ninth lens 54, and a tenth lens 59. The sixth lens 51 is a negative cemented lens 51u (negative lens 51n) consisting of a positive meniscus lens (positive lens 51a) and a biconcave lens (negative lens 51b). The seventh lens 52 is a biconvex aspherical lens C2 (positive lens 52p) made of glass. The eighth lens 53 is a positive meniscus lens (positive lens 53p). The ninth lens 54 is a negative cemented lens 54u (negative lens 54n) consisting of a biconcave lens (negative lens 54a) and a biconvex lens (positive lens 54b). The tenth lens 59 is a positive lens group 59g consisting of a biconvex lens (positive lens 59p or positive lens 55).

[0084] FIG. 11 is a diagram showing longitudinal aberration characteristics (that is, spherical aberration characteristics, astigmatism characteristics, and distortion characteristics) of the fixed focus lens 40 of Example 4.

[0085] For reference, the following Table 9 shows Examples 1 to 4 corresponding to each of the conditional expressions (1) to (7). [Table 9] TIFF2025139225000003.tif68168

[0086] [Other matters] The structure described above is an example, and various modifications can be made within the scope of achieving the same function.

[0087] 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.

[0088] Furthermore, the object of enlarged projection by the fixed focus lens 40 is not limited to images formed by a liquid crystal panel; images formed by a light modulation element such as a digital micromirror device can also be enlarged and projected.

[0089] Summary of the Disclosure A summary of this disclosure is provided below.

[0090] (Appendix 1) The lens comprises, in order from the magnification side to the reduction side, a first lens group having positive refractive power, an aperture stop, and a second lens group having positive refractive power; In the first lens group, either the lens closest to the magnification side or the lens second from the magnification side is an aspherical lens, The reduction side is telecentric, A fixed focal length lens that satisfies the following conditions: ω>45 … (1) 0.15 <L1H / LL<0.4 … (2) 2.5 <BF / F<3.5 … (3) where: ω: Maximum half angle of view of fixed focal length lens L1H: The height of the light ray passing through the maximum image height on the lens surface on the most magnifying side of a fixed focal length lens LL: Fixed focal length BF: Air-equivalent back focus length F: Focal length of the entire fixed-focus lens system In such a fixed focus lens, the refractive power of the first lens group is set to be positive, thereby reducing the overall length and maximum diameter of the fixed focus lens. By using an aspherical lens on the most magnification side or the second lens from the magnification side, it is possible to achieve both correction of field curvature and distortion and compactness. Conditional formula (1) expresses the widening of the angle of a fixed focus lens. Conditional formula (2) is a formula for reducing the size of a fixed focal length lens in the height direction. By setting the value L1H / LL in the above conditional formula to the lower limit or more, it is possible to achieve size reduction in the height direction while effectively correcting field curvature and distortion. By setting the value L1H / LL in the above conditional formula to the upper limit or less, it is possible to prevent the fixed focal length lens from increasing in height, and to satisfy the required product height. Conditional expression (3) 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 the length necessary to place 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 satisfy the requirements for a short lens length and a wide angle of view of the fixed focal length lens.

[0091] (Appendix 2) 2. The fixed focus lens according to claim 1, wherein the first lens group is made up of, in order from the reduction side, a single lens or a cemented lens having positive, positive, negative, negative, and negative refractive powers. In this type of fixed-focus lens, because the light rays are spread toward the magnification side of the first lens group, a configuration in which negative lenses are arranged in order from the magnification side is essential. To achieve compactness, a positive lens must be arranged on the reduction side. Furthermore, while a stronger positive power is more suitable for a compact configuration, it is undesirable because it generates aberrations. In this configuration, by arranging two lenses with positive refractive power side by side on the reduction side, the amount of aberration generated per positive lens is reduced, making compactness possible.

[0092] (Appendix 3) 3. The fixed focus lens according to claim 1, wherein the second lens group is made up of, in order from the magnification side, a single lens or a cemented lens having negative-positive-positive-negative-positive refractive power. In the above configuration, because the first lens group has positive refractive power, it is preferable to correct aberrations by using a negative lens on the lens on the magnification side closest to the first lens group. To achieve compactness, lenses with strong positive refractive power are used near the aperture stop, but if a single lens bears the positive power, it becomes difficult to correct aberrations. Therefore, it is preferable to divide the positive power and arrange it in this way. To ensure telecentricity, a positive lens must be arranged on the reduction side, and a negative lens must be arranged to correct this.

[0093] (Appendix 4) 4. The fixed focus lens according to claim 1, wherein the second lens group has an aspherical lens having positive refractive power. This effectively suppresses astigmatism, and makes it possible to reduce the lens diameter and costs compared to when the second lens group is composed of only spherical lenses.

[0094] (Appendix 5) 5. The fixed focus lens according to claim 1, wherein the lens in the second lens group closest to the magnification side is a negative cemented lens made up of lenses having positive refractive power and negative refractive power. This allows the fixed focus lens to achieve a wider angle, smaller size, and reduced chromatic aberration.

[0095] (Appendix 6) A fixed focus lens according to any one of appendixes 1 to 5, which satisfies the following conditional formula: 3.0 <Fg1p / F<25.0 … (4) where: Fg1p: The focal length of the lens closest to the reduction side in the first lens group Conditional expression (4) is an expression for miniaturizing a fixed-focus lens and correcting aberrations. By setting the value Fg1p / F of the above conditional expression to the lower limit or more, it is possible to maintain compactness while favoring aberration correction. By setting the value Fg1p / F of the above conditional expression to the upper limit or less, it is possible to achieve compactness while favoring aberration correction.

[0096] (Appendix 7) A fixed focus lens according to any one of appendixes 1 to 6, which satisfies the following conditional formula: 0.2 <Fg2p1 / Fg2p2<1.2 … (5) where: Fg2p1: the focal length of the positive single lens or the positive cemented lens located on the most enlargement side in the second lens group Fg2p2: the focal length of the positive single lens or the positive cemented lens located second most to the magnification side in the second lens group Conditional expression (5) expresses the power distribution of the two positive lenses located on the magnification side in the second lens group. By satisfying conditional expression (5), it is possible to effectively correct various aberrations caused by the miniaturization and wide-angle of fixed-focus lenses.

[0097] (Appendix 8) A fixed focus lens according to any one of appendices 1 to 7, which satisfies the following conditional formula: 0.8<|Fg2n1 / Fg2p3-|<2.8 … (6) where: Fg2n1: the focal length of the negative single lens or negative cemented lens located at the most reduction side in the second lens group Fg2p3-: the focal length of the negative single lens or the positive lens located on the reduction side of the negative cemented lens located on the most reduction side in the second lens group Conditional expression (6) is an expression for correcting telecentricity and lateral chromatic aberration. By setting the value Fg2n1 / Fg2p3- of the above conditional expression to be equal to or greater than the lower limit, telecentricity can be ensured. By setting the value Fg2n1 / Fg2p3- of the above conditional expression to be equal to or less than the upper limit, lateral chromatic aberration can be effectively corrected.

[0098] (Appendix 9) A fixed focus lens according to any one of appendices 1 to 8, which satisfies the following conditional formula: 0.45 <LS / LL<0.65 … (7) where: LS: Distance from the most magnifying lens surface of a fixed-focus lens to the aperture diaphragm Conditional expression (7) relates to the reduction of the lens diameter and telecentricity. By setting the value LS / LL of the above conditional expression to the lower limit or more, telecentricity can be ensured. By setting the value LS / LL of the above conditional expression to the upper limit or less, the reduction of the lens diameter can be achieved.

[0099] (Appendix 10) an image forming unit having a light modulation element that modulates light from a light source device to form image light; a fixed focus lens according to any one of Supplementary Notes 1 to 9 that projects image light from an image forming unit; A projector equipped with This allows for the miniaturization of projectors equipped with fixed focus lenses. [Explanation of symbols]

[0100] 2...Projector, 10...Light source device, 20a...Image forming unit, 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...Fixed focus lens, 41 to 45, 51 to 54, 59...Lens, 41n, 42n, 43n, 51n, 54n...Negative lens, 44p, 4 5p, 52p, 53p, 59p, 55, 56...positive lenses, 59g...lens group, 43u, 44u, 51u, 54u...cemented lenses, 60...optical system portion, 80...circuit device, 81...image processing unit, 82...display drive unit, 88...main control unit, C1, C2...aspheric lenses, G1, G2...lens group, OA...optical axis, OM...light modulation element, PR...prism, RC...reduction side conjugate surface, SC...screen, ST...aperture stop

Claims

1. The lens comprises, in order from the magnification side to the reduction side, a first lens group having positive refractive power, an aperture stop, and a second lens group having positive refractive power; In the first lens group, either the lens closest to the magnification side or the second lens from the magnification side is an aspherical lens, The reduction side is telecentric, Satisfy the following condition: Fixed focus lens. ω>45 … (1) 0.15<L1H / LL<0.4... (2) 2.5<BF / F<3.5... (3) where: ω: maximum half angle of view of the fixed focus lens L1H: the height of the ray of light passing through the maximum image height on the lens surface of the fixed focus lens closest to the enlargement side LL: length of the fixed focus lens BF: Air-equivalent back focus length F: focal length of the entire fixed focus lens system

2. the first lens group is composed of, in order from the reduction side, a single lens or a cemented lens having positive, positive, negative, negative, and negative refractive powers, The fixed focus lens of claim 1 .

3. the second lens group is composed of, in order from the magnification side, a single lens or a cemented lens having negative-positive-positive-negative-positive refractive power; The fixed focus lens of claim 1 .

4. the second lens group includes an aspherical lens having positive refractive power; The fixed focus lens of claim 1 .

5. the lens in the second lens group closest to the enlargement side is a negative cemented lens made up of lenses having positive and negative refractive powers; The fixed focus lens of claim 1 .

6. Satisfy the following condition: The fixed focus lens of claim 1 . 3.0<Fg1p / F<25.0... (4) where: Fg1p: the focal length of the lens closest to the reduction side in the first lens group

7. Satisfy the following condition: The fixed focus lens of claim 1 . 0.2<Fg2p1 / Fg2p2<1.2... (5) where: Fg2p1: the focal length of the positive single lens or the positive cemented lens arranged in the second lens group on the most enlargement side Fg2p2: the focal length of the positive single lens or the positive cemented lens arranged second most to the enlargement side in the second lens group

8. Satisfy the following condition: The fixed focus lens of claim 1 . 0.8<|Fg2n1 / Fg2p3-|<2.8... (6) where: Fg2n1: the focal length of the negative single lens or negative cemented lens arranged in the second lens group on the most reduction side Fg2p3-: the focal length of the negative single lens or the positive lens arranged on the reduction side of the negative cemented lens arranged on the most reduction side in the second lens group

9. Satisfy the following condition: The fixed focus lens of claim 1 . 0.45<LS / LL<0.65... (7) where: LS: the distance from the lens surface of the fixed focus lens on the most enlarged side to the aperture stop

10. an image forming unit having a light modulation element that modulates light from a light source device to form image light; a fixed focus lens according to any one of claims 1 to 9, which projects the image light from the image forming unit; Equipped with projector.

Images