Fixed focus lens and projector

Abstract

And a fixed focus lens and a projector. And the fixed focus lens is more miniaturized. The fixed-focus lens comprises, in order from the magnification 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, either a lens (41) closest to the magnification side or a second lens (42) from the magnification side is an aspheric lens (C1), the reduction side is telecentric, and the following conditional expressions are satisfied: [Omega] gt, [Omega] gt, [Omega] gt, [Omega] gt, [Omega] gt, [Omega] gt, [Omega] gt, [Omega] gt, [Omega] gt, [Omega] gt, [Omega] gt; 45... (1) 0.15 lt; l < 1H > / L < lt >; 0.4... (2) 2.5 lt; bF / Flt; (3) the value omega is the maximum half-field angle of the fixed-focus lens, the value L1H is the height of light passing through the maximum image height in a lens surface (41s) closest to the magnification side of the fixed-focus lens, the value LL is the length of the fixed-focus lens, the value BF is the back focal length air conversion value, and the value F is the focal length of the whole system of the fixed-focus lens.

Description

Technical Field

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

[0002] As a projection lens, there is known a projection lens which is composed of a first lens group having negative refractive power and a second lens group having positive refractive power in order from the magnification side, and is substantially telecentric on the reduction side (Patent Document 1).

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 2009-104048

[0004] The above-mentioned projection lens is an optical system that satisfies wide-angle and relatively good image performance. However, due to the large lens length and lens diameter, there are problems such as poor installation performance and restrictions on product design and layout. Summary of the Invention

[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 second lens from the magnification side is an aspherical lens, the reduction side is telecentric, and the following conditional expression is satisfied:

[0006] ω>45…(1)

[0007] 0.15 <L1H / LL<0.4…(2)

[0008] 2.5 <BF / F<3.5…(3)

[0009] Here, the value ω is the maximum half field of view of the fixed-focus lens, the value L1H is the height of the light passing through the maximum image height on the lens surface closest to the magnification side of the fixed-focus lens, the value LL is the length of the fixed-focus lens, the value BF is the air-converted value of the back focal length, and the value F is the focal length of the entire fixed-focus lens system.

[0010] A projector according to one aspect of the present invention includes: an image forming unit having a light modulator that modulates light from a light source device to form image light; and the above-mentioned fixed-focus lens that projects the image light from the image forming unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a diagram illustrating a projector including a fixed-focus lens according to an embodiment.

[0012] Figure 2 This figure shows the structure and ray diagram of a fixed-focus lens according to an embodiment.

[0013] Figure 3 It is a diagram showing a projection state of a fixed-focus lens on a screen according to an embodiment.

[0014] Figure 4 1 is a diagram showing the structure of a fixed focus lens according to Example 1;

[0015] Figure 5 The longitudinal aberration characteristics of the fixed focus lens of Example 1 are shown.

[0016] Figure 6 This is a diagram showing the structure of a fixed-focus lens according to Example 2.

[0017] Figure 7 The longitudinal aberration characteristics of the fixed focus lens of Example 2 are shown.

[0018] Figure 8 This is a diagram showing the structure of a fixed-focus lens according to Example 3.

[0019] Figure 9 The longitudinal aberration characteristics of the fixed focus lens of Example 3 are shown.

[0020] Figure 10 This is a diagram showing the structure of a fixed-focus lens according to Example 4.

[0021] Figure 11 The longitudinal aberration characteristics of the fixed-focus lens of Example 4 are shown.

[0022] Description of labels

[0023] 2 projector; 10 light source device; 20a image forming unit; 23, 24 relay lenses; 25, 26, 27 reflecting mirrors; 28B, 28G, 28R field lenses; 29B, 29G, 29R liquid crystal panel; 31 cross-dichroic prism; 40 fixed focus lens; 41-45, 51-54, 59 lenses; 41n, 42n, 43n, 51n, 54n negative lenses; 44p, 45p, 52p, 53p, 59p, 55, 56 positive lenses; 59g lens group; 43u, 44u, 51u, 54u cemented lenses; 60 optical system part; 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. DETAILED DESCRIPTION

[0024] [Implementation Method]

[0025] Hereinafter, a fixed-focus lens 40 according to an embodiment of the present invention and a projector 2 incorporating the fixed-focus lens 40 will be described with reference to the drawings.

[0026] like Figure 1 As shown, the projector 2 incorporating the fixed focus lens 40 of the embodiment includes an optical system portion 60 for projecting image light and a circuit device 80 for controlling the operation of the optical system portion 60 .

[0027] In the optical system section 60, the light source device 10 emits uniform light including R, G, and B light. 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 light passing through the two-stage integrator lens into predetermined linearly polarized light; and a superimposing lens that superimposes the illumination light emitted from the subsequent integrator lens on the display areas of the liquid crystal panels 29R, 29G, and 29B.

[0028] The first dichroic mirror 21 reflects the R light incident from the light source device 10 and transmits the G and B lights. The R light reflected by the first dichroic mirror 21 passes through the reflector 25 and the field lens 28R and enters the liquid crystal panel 29R, which serves as the light modulator OM. The liquid crystal panel 29R modulates the R light according to the image signal, thereby forming an R-colored image.

[0029] 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, serving as a light modulator OM. The liquid crystal panel 29G modulates the G light according to the image signal, thereby forming a G-color image. The B light that has passed through the second dichroic mirror 22 passes through relay lenses 23 and 24, reflective mirrors 26 and 27, and a field lens 28B and enters a liquid crystal panel 29B, serving as a light modulator OM. The liquid crystal panel 29B modulates the B light according to the image signal, thereby forming a B-color image.

[0030] The cross dichroic prism 31 is a prism for light synthesis, and synthesizes the light modulated by the liquid crystal panels 29R, 29G, and 29B into image light, and directs the image light toward the fixed focus lens 40 .

[0031] The fixed focus lens 40 is a projection lens that amplifies the image light modulated by the liquid crystal panels 29R, 29G, and 29B and synthesized by the cross dichroic prism 31 and projects it onto a screen SC (not shown). The liquid crystal panels 29R, 29G, and 29B are located on the reduction side conjugate plane RC of the fixed focus lens 40 (see the following). Figure 2 ) forms an image forming unit 20a for projecting an image.

[0032] The circuit device 80 includes: an image processing unit 81, which is input with an external image signal such as a video signal; a display driving unit 82, which drives the liquid crystal panels 29R, 29G, and 29B provided in the optical system part 60 according to the output of the image processing unit 81; and a main control unit 88, which uniformly controls the operations of these circuit parts 81, 82, etc.

[0033] The image processing unit 81 converts the input external image signal into an image signal including grayscales of each color, etc. The image processing unit 81 can also perform various image processing such as distortion correction and color correction on the external image signal.

[0034] The display driving 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 cause the liquid crystal panels 29R, 29G, and 29B to form an image corresponding to the image signal or an image obtained by performing image processing on the image.

[0035] Below, refer to Figure 2 and Figure 3 The fixed focus lens 40 according to the embodiment will be described in detail. Figure 2 1 and 2 show the structure and light ray diagram of the fixed focus lens 40 according to the embodiment. Figure 3 : is a diagram showing a projection state of the fixed focus lens 40 according to the embodiment onto the screen SC. Figure 2 The fixed focus lens 40 illustrated in the example has the same structure as the fixed focus lens 40 of Example 1 described later.

[0036] The fixed focus lens 40 of the embodiment projects the image formed on the projection surface of the liquid crystal panel 29G (29R, 29B) onto the screen SC. Here, a lens equivalent to Figure 1 The cross dichroic prism 31 is a prism PR.

[0037] The fixed-focus lens 40 is composed, in order from the screen SC (magnification side) toward the reduction side, of a first lens group G1 having positive refractive power, an aperture stop ST, and a second lens group G2 having positive refractive power. By setting the refractive power of the first lens group G1 to be positive, the overall length and maximum diameter of the fixed-focus lens 40 can be suppressed.

[0038] Fixed-focus lens 40 is telecentric on the object side or reduction side where liquid crystal panel 29G (29R, 29B) is located. This improves light utilization efficiency and easily absorbs assembly variations when light modulated by each liquid crystal panel 29G (29R, 29B) is combined in cross dichroic prism 31 to form image light. Telecentricity also includes a substantially telecentric state where the principal ray is approximately parallel to optical axis OA.

[0039] The first lens group G1 is composed, in order from the reduction side, of lenses 45 to 41 having positive, positive, negative, and negative refractive powers. Lenses 45 to 41 are single lenses or cemented lenses. Specifically, the first lens group G1 is composed, in order from the magnification side, of a first lens 41 with negative refractive power, a second lens 42 with negative refractive power, a third lens 43 with negative refractive power, a fourth lens 44 with positive refractive power, and a fifth lens 45 with positive refractive power. To spread light toward the magnification side, the first lens group G1 is configured with multiple negative lenses 41n to 43n on the magnification side. Furthermore, to achieve miniaturization, the first lens group G1 is configured with multiple positive lenses 44p and 45p on the reduction side. While a strong positive refractive power configuration for the first lens group G1 is suitable for a compact structure, it is not preferred because it causes aberrations. In this configuration, by arranging two positive lenses in parallel on the reduction side, the amount of aberration generated per one positive lens is reduced, thereby achieving miniaturization.

[0040] In the first lens group G1, either the first lens 41 located most toward the magnification side or the second lens 42 located second from the magnification side is an aspherical lens C1. By using the aspherical lens C1 as either the first lens 41 located most toward the magnification side or the second lens 42 located second from the magnification side, correction of field curvature and distortion aberrations and miniaturization can be achieved simultaneously.

[0041] The lenses 41 to 45 constituting the first lens group G1 are made of glass or plastic. From the perspective of weight reduction and ease of processing, the aspheric lens C1 of the first lens group G1 is preferably made of plastic. Alternatively, the aspheric lens C1 may be made of glass.

[0042] exist Figure 2 In the example, the first lens 41 is a negative lens 41n composed of, for example, a single lens, and is arranged closest to the magnification side. The first lens 41 is an aspheric lens C1 made of plastic. The second lens 42 is a negative lens 42n composed of, for example, a single lens. The third lens 43 is a negative lens 43n composed of, for example, a cemented lens 43u. The cemented lens 43u is composed of, for example, a combination of a negative lens 43a and a positive lens 43b in order from the magnification side. The fourth lens 44 is, for example, a positive lens 44p composed of a cemented lens 44u. The cemented lens 44u is composed of, for example, a combination of a positive lens 44a and a negative lens 44b in order from the magnification side. The fifth lens 45 is a positive lens 45p composed of, for example, a single lens.

[0043] The fixed focus lens 40 preferably performs focusing by moving any one or two lenses 41 to 45 in the first lens group G1 in the direction of the optical axis OA.

[0044] The second lens group G2 is composed, in order from the magnification side, of lenses 51 to 54, and lens 59, each having negative, positive, positive, negative, and positive refractive powers. Lenses 51 to 54, and lens 59 are single lenses or cemented lenses. Specifically, the second lens group G2 is composed, in order from the magnification side, of the sixth lens 51 with negative refractive power, the seventh lens 52 with positive refractive power, the eighth lens 53 with positive refractive power, the ninth lens 54 with negative refractive power, and the tenth lens 59 with positive refractive power. Because the first lens group G1 has positive refractive power, the second lens group G2 corrects aberrations by configuring the sixth lens 51, the lens closest to the first lens group G1 on the magnification side, as a negative lens 51n. To minimize the size of the second lens group G2, it is preferable to place a lens with strong positive refractive power near the aperture stop ST. However, if a single lens bears the positive refractive power, aberration correction becomes difficult. Therefore, the seventh lens 52 and the eighth lens 53 in the second lens group G2, located near the aperture stop ST, are configured with positive refractive power in a split configuration. To ensure telecentricity, a tenth lens 59 with positive refractive power is located on the reduction side of the second lens group G2. Furthermore, the tenth lens 59 closest to the reduction side may be composed of multiple single lenses, multiple cemented lenses, or a combination of single and cemented lenses, as long as it forms a positive lens group 59g and has positive refractive power as a whole. Furthermore, in order to correct aberrations required by the addition of the tenth lens 59, the second lens group G2 includes a ninth lens 54 with negative refractive power located on the magnification side of the tenth lens 59.

[0045] The second lens group G2 includes an aspherical lens C2 having positive refractive power. This effectively suppresses astigmatism, and enables a smaller lens diameter and lower costs compared to a case where the second lens group G2 is composed only of spherical lenses.

[0046] The sixth lens 51 closest to the magnification side in the second lens group G2 is a negative cemented lens 51u composed of lenses 51a and 51b having positive and negative refractive powers.

[0047] The lenses 51 to 54 and 59 constituting the second lens group G2 are made of glass or plastic. From the perspective of light resistance and component cost, the aspherical lens C2 of the second lens group G2 is preferably made of glass. Alternatively, the aspherical lens C2 may be made of plastic.

[0048] exist Figure 2In the example, the sixth lens 51 is a negative lens 51n composed of, for example, a cemented lens 51u, and is arranged on the magnification side, that is, the side closest to the aperture stop ST. The cemented lens 51u is composed of, for example, a combination of a positive lens 51a and a negative lens 51b in order from the magnification side. The seventh lens 52 is a positive lens 52p composed of, for example, a single lens, and is an aspherical lens C2 made of glass. The eighth lens 53 is a positive lens 53p composed of, for example, a single lens. The ninth lens 54 is a negative lens 54n composed of, for example, a cemented lens 54u. The cemented lens 54u is composed of, for example, a combination of a negative lens 54a and a positive lens 54b in order from the magnification side. The tenth lens 59 is a positive lens 59p composed of, for example, a single lens. Specifically, the tenth lens 59 is composed of, for example, a positive lens 55 and a positive lens 56. Figure 2 The tenth lens 59 can also be said to be a positive lens group 59g formed by arranging two positive single lenses. In addition, the tenth lens 59 can also be composed of, for example, a single lens or a cemented lens.

[0049] The aperture stop ST is a surface for defining the F number and is disposed at a position where the principal ray passes through the optical axis OA. The aperture stop ST may or may not include an opening member having a light-blocking property as an actual aperture.

[0050] The fixed focus lens 40 according to the embodiment satisfies the following conditional expressions.

[0051] ω>45…(1)

[0052] Here, the value ω is the maximum half-angle of view of the fixed-focus lens 40. Conditional expression (1) is an expression indicating the widening of the angle of the fixed-focus lens 40.

[0053] The fixed focus lens 40 according to the embodiment satisfies the following conditional expressions.

[0054] 0.15 <L1H / LL<0.4…(2)

[0055] Here, the value L1H is the height of a ray passing through the maximum image height on the most magnification-side lens surface of the fixed focus lens 40 , specifically, the magnification-side lens surface 41 s of the first lens 41 , and the value LL is the length of the fixed focus lens 40 .

[0056] Conditional equation (2) is a formula for miniaturizing the height direction of the fixed-focus lens 40, that is, miniaturizing the lens diameter. By setting the value L1H / LL in the above conditional equation to a value greater than the lower limit, miniaturization in the height direction can be achieved while effectively correcting field curvature and distortion. By setting the value L1H / LL in the above conditional equation to a value less than the upper limit, the height of the fixed-focus lens 40 can be suppressed from increasing, thereby meeting product height requirements.

[0057] The fixed focus lens 40 according to the embodiment satisfies the following conditional expressions.

[0058] 2.5 <BF / F<3.5…(3)

[0059] Here, the value BF is the air-converted value of the back focus, and the value F is the focal length of the entire fixed focus lens 40 system.

[0060] Conditional equation (3) is used to ensure an appropriate back focus. By setting the value BF / F in the conditional equation above the lower limit, the length required for inserts such as the prism PR can be ensured. By setting the value BF / F in the conditional equation below the upper limit, the lens length of the fixed-focus lens 40 can be reduced and the angle of view can be widened.

[0061] The fixed focus lens 40 according to the embodiment satisfies the following conditional expressions.

[0062] 3.0 <Fg1p / F<25.0…(4)

[0063] Here, the value Fg1p is the focal length of the lens closest to the reduction side in the first lens group G1 , specifically, the fifth lens 45 , and the value F is the focal length of the entire fixed focus lens system 40 .

[0064] Conditional equation (4) is an equation for miniaturization and aberration correction of the fixed focus lens 40. By setting the value Fg1p / F in the conditional equation to a lower limit or higher, miniaturization can be maintained while facilitating aberration correction. By setting the value Fg1p / F in the conditional equation to a lower limit or lower, aberration correction can be facilitated while miniaturization can be achieved.

[0065] The fixed focus lens 40 according to the embodiment satisfies the following conditional expressions.

[0066] 0.2 <Fg2p1 / Fg2p2<1.2…(5)

[0067] Here, the value Fg2p1 is the focal length of the positive single lens or positive cemented lens arranged on the most magnification side in the second lens group G2, specifically the 7th lens 52, and the value Fg2p2 is the focal length of the positive single lens or positive cemented lens arranged on the second magnification side in the second lens group G2, specifically the 8th lens 53.

[0068] Conditional expression (5) represents the diopter distribution of the two positive lenses arranged on the magnification side in the second lens group G2. By satisfying conditional expression (5), various aberrations caused by the miniaturization and widening of the fixed focus lens 40 can be well corrected.

[0069] The fixed focus lens 40 according to the embodiment satisfies the following conditional expressions.

[0070] 0.8<|Fg2n1 / Fg2p3-|<2.8…(6)

[0071] Here, the value Fg2n1 is the focal length of the negative single lens or negative cemented lens positioned most toward the reduction side in the second lens group G2, specifically the ninth lens 54. The value Fg2p3- is the focal length of the positive lens positioned more toward the reduction side than the ninth lens 54, specifically the tenth lens 59. The ninth lens 54 is a negative single lens or negative cemented lens positioned most toward the reduction side in the second lens group G2. The positive lens positioned on the reduction side is composed of one or more single lenses or cemented lenses.

[0072] Conditional equation (6) is an equation for correcting telecentricity and lateral chromatic aberration. By setting the value Fg2n1 / Fg2p3- in the conditional equation to a value greater than the lower limit, telecentricity can be ensured. By setting the value Fg2n / Fg2p3- in the conditional equation to a value less than the upper limit, lateral chromatic aberration can be effectively corrected.

[0073] The fixed focus lens 40 according to the embodiment satisfies the following conditional expressions.

[0074] 0.45 <LS / LL<0.65…(7)

[0075] Here, the value LS is the distance from the lens surface closest to the magnification side of the fixed focus lens 40 , specifically, the lens surface 41 s of the first lens 41 , to the aperture stop ST, and the value LL is the length of the fixed focus lens 40 .

[0076] Conditional expression (7) is related to miniaturization of the lens diameter and telecentricity. By setting the value LS / LL of the conditional expression above the lower limit, telecentricity can be ensured. By setting the value LS / LL of the conditional expression below the upper limit, miniaturization of the lens diameter can be achieved.

[0077] The fixed focus lens 40 described above is composed of a first lens group G1 with positive refractive power, an aperture stop ST and a second lens group G2 with positive refractive power, in order from the magnification side to the reduction side. In the first lens group G1, either the lens 41 closest to the magnification side or the second lens 42 from the magnification side is an aspheric lens C1, the reduction side is telecentric, and the following conditional expression is satisfied.

[0078] ω>45…(1)

[0079] 0.15 <L1H / LL<0.4…(2)

[0080] 2.5 <BF / F<3.5…(3)

[0081] Here, the value ω is the maximum half field of view angle of the fixed-focus lens 40, the value L1H is the height of the light passing through the maximum image height in the lens surface closest to the magnification side of the fixed-focus lens 40, the value LL is the length of the fixed-focus lens 40, the value BF is the air conversion value of the back focal length, and the value F is the focal length of the entire fixed-focus lens 40 system.

[0082] In the fixed-focus lens 40, by making the first lens group G1 have a positive refractive power, the overall length and maximum diameter of the fixed-focus lens 40 can be reduced. Since the lens 41 closest to the magnification side or the second lens 42 from the magnification side is an aspherical lens C1, correction of field curvature and distortion aberrations can be achieved while achieving miniaturization.

[0083] Conditional expression (1) is a formula for expressing the widening of the fixed focus lens 40. Conditional expression (2) is a formula for miniaturization of the fixed focus lens 40 in the height direction. By setting the value L1H / LL of the above conditional expression to be above the lower limit value, miniaturization in the height direction can be achieved, and field curvature and distortion aberration can be well corrected. By setting the value L1H / LL of the above conditional expression to be below the upper limit value, the increase in the height of the fixed focus lens 40 can be suppressed, and the product height requirement can be met. Conditional expression (3) is a formula for ensuring an appropriate back focus. By setting the value BF / F of the above conditional expression to be above the lower limit value, the length required for configuring inserts such as the prism PR can be ensured. By setting the value BF / F of the above conditional expression to be below the upper limit value, the miniaturization and widening of the lens length of the fixed focus lens 40 can be met.

[0084] As described above, the fixed-focus lens 40 achieves a compact projection lens that is bright and provides high image quality despite its narrow field of view. Specifically, the fixed-focus lens 40 achieves both a wide field of view (90 degrees or greater) and compactness, effectively correcting various aberrations. This allows for product miniaturization without sacrificing resolution, thus reducing costs.

[0085] The projector 2 described above includes an image forming unit 20a having a light modulator OM that modulates light from the light source device 10 to form image light, and the aforementioned fixed-focus lens 40 that projects the image light from the image forming unit 20a. This allows the projector 2 equipped with the fixed-focus lens 40 to be miniaturized.

[0086] [Example]

[0087] Hereinafter, an embodiment of the fixed focus lens 40 will be described. The meanings of the specifications common to the following embodiments 1 to 4 are summarized as follows.

[0088] F: Fixed focus lens 40 The focal length of the entire system

[0089] Fno: F number

[0090] IH: Maximum image height of the lens

[0091] TTL: distance from the lens surface 41s closest to the magnification side of the fixed focus lens 40 to the source image

[0092] LL: Length of the fixed focus lens 40 (the distance from the lens surface 41s on the most magnification side of the fixed focus lens 40 to the final lens surface)

[0093] BF: Back focus air conversion value

[0094] LS: distance from the lens surface 41s on the most magnification side of the fixed focus lens 40 to the aperture stop ST

[0095] L1H: Height of a ray passing through the maximum image height on the lens surface 41s closest to the magnification side of the fixed focus lens 40

[0096] FG1: Focal length of the first lens group G1

[0097] FG2: Focal length of the second lens group G2

[0098] R: paraxial curvature radius

[0099] D: Axis distance (lens thickness or lens distance)

[0100] Nd: Refractive index of d-line (reference wavelength 588 nm)

[0101] Vd: Abbe number of d-line (reference wavelength 588nm)

[0102] The displacement z of the surface on the aspherical surface is determined by the following polynomial (aspherical surface formula).

[0103]

[0104] in,

[0105] c: curvature (1 / R)

[0106] h: height from the optical axis OA

[0107] k: conic constant of the aspheric surface

[0108] Ai: aspheric coefficient of order i

[0109] In the tables of the respective examples, surface number 0 represents the image plane (projected surface) on the screen SC, "ST" represents the aperture stop ST, and "INF" represents infinity. The last number in the surface number represents the display surface of the liquid crystal panel 29G, etc. Surfaces with an "*" after the surface number are aspherical surfaces.

[0110] (Example 1)

[0111] The overall specifications of the fixed focus lens 40 of Example 1 are shown below.

[0112] F=7.733(mm)

[0113] Fno=1.787

[0114] IH=11.000(mm)

[0115] TTL=143.235(mm)

[0116] LL=108.290(mm)

[0117] BF=25.729(mm)

[0118] LS=54.091 (mm)

[0119] L1H=17.778(mm)

[0120] FG1=100.000(mm)

[0121] FG2=28.467(mm)

[0122] Table 1 below shows the data of the lens surface of Example 1.

[0123] [Table 1]

[0124]

[0125] Table 2 below shows the aspheric coefficients of the lens surface of Example 1. In Table 2 and the following tables, powers of 10 (e.g., 1.00×10 +18 ) is assumed to be an expression using E (e.g., 1.00E+18).

[0126] [Table 2]

[0127]

[0128] Figure 4 4 is a cross-sectional view of the fixed focus lens 40 according to Example 1. Figure 4 The fixed-focus lens 40 shown corresponds to the fixed-focus lens 40 of the embodiment.

[0129] The fixed focus lens 40 magnifies the image on the display surface of the liquid crystal panel 29G and projects it onto the screen SC (see Figure 3The fixed-focus lens 40 includes, in order from the screen SC on the magnification 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 substantially telecentric on the reduction side.

[0130] The first lens group G1 is composed, in order from the magnification side, of 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 negative aspheric lens C1 (negative lens 41n) made of plastic. 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) composed 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) composed 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).

[0131] The second lens group G2 consists, in order from the magnification side, of the sixth lens 51, the seventh lens 52, the eighth lens 53, the ninth lens 54, and the tenth lens 59. The sixth lens 51 is a negative cemented lens 51u (negative lens 51n) composed of a positive meniscus lens (positive lens 51a) and a biconcave lens (negative lens 51b). The seventh lens 52 is a glass biconvex 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) composed of a biconcave lens (negative lens 54a) and a biconvex lens (positive lens 54b). The tenth lens 59, forming a positive lens group 59g, is composed of a biconvex lens (positive lens 59p or positive lens 55) and a biconvex lens (positive lens 59p or positive lens 56).

[0132] Figure 5 Graphs showing longitudinal aberration characteristics (ie, spherical aberration characteristics, astigmatism characteristics, and distortion characteristics) of the fixed-focus lens 40 of Example 1. FIG.

[0133] (Example 2)

[0134] The overall specifications of the fixed focus lens 40 of Example 2 are shown below.

[0135] F=7.663(mm)

[0136] Fno=1.785

[0137] IH=11.000(mm)

[0138] TTL=118.514(mm)

[0139] LL=83.569(mm)

[0140] BF=25.730(mm)

[0141] LS=44.165(mm)

[0142] L1H=22.585(mm)

[0143] FG1=100.000(mm)

[0144] FG2=25.123(mm)

[0145] Table 3 below shows the data of the lens surface of Example 2.

[0146] [Table 3]

[0147]

[0148] Table 4 below shows the aspheric coefficients of the lens surface of Example 2.

[0149] [Table 4]

[0150]

[0151] Figure 6 4 is a cross-sectional view of the fixed focus lens 40 according to the second embodiment.

[0152] The fixed focus lens 40 magnifies the image on the display surface of the liquid crystal panel 29G and projects it onto the screen SC (see Figure 3 The fixed-focus lens 40 includes, in order from the screen SC on the magnification 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 substantially telecentric on the reduction side.

[0153] The first lens group G1 consists, in order from the magnification side, of 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 negative aspheric plastic 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) composed 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) composed 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).

[0154] The second lens group G2 consists, in order from the magnification side, of the sixth lens 51, the seventh lens 52, the eighth lens 53, the ninth lens 54, and the tenth lens 59. The sixth lens 51 is a negative cemented lens 51u (negative lens 51n) composed of a positive meniscus lens (positive lens 51a) and a biconcave lens (negative lens 51b). The seventh lens 52 is a glass biconvex 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) composed of a biconcave lens (negative lens 54a) and a biconvex lens (positive lens 54b). The tenth lens 59, forming a positive lens group 59g, is composed of a biconvex lens (positive lens 59p or positive lens 55) and a biconvex lens (positive lens 59p or positive lens 56).

[0155] Figure 7 Graphs showing longitudinal aberration characteristics (ie, spherical aberration characteristics, astigmatism characteristics, and distortion characteristics) of the fixed-focus lens 40 of Example 2. FIG.

[0156] (Example 3)

[0157] The overall specifications of the fixed focus lens 40 of Example 3 are shown below.

[0158] F=7.723(mm)

[0159] Fno=1.770

[0160] IH=11.000(mm)

[0161] TTL=138.779(mm)

[0162] L=103.834(mm)

[0163] BF=25.433(mm)

[0164] LS=58.044(mm)

[0165] L1H=20.478(mm)

[0166] FG1=100.000(mm)

[0167] FG2=29.427(mm)

[0168] Table 5 below shows the data of the lens surface of Example 3.

[0169] [Table 5]

[0170]

[0171] Table 6 below shows the aspheric coefficients of the lens surface of Example 3.

[0172] [Table 6]

[0173]

[0174] Figure 8 4 is a cross-sectional view of the fixed focus lens 40 according to Example 3.

[0175] The fixed focus lens 40 magnifies the image on the display surface of the liquid crystal panel 29G and projects it onto the screen SC (see Figure 3 The fixed-focus lens 40 includes, in order from the screen SC on the magnification 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 substantially telecentric on the reduction side.

[0176] The first lens group G1 is composed, in order from the magnification side, of 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 negative aspheric lens C1 (negative lens 41n) made of plastic. 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) composed 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) composed 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).

[0177] The second lens group G2 consists, in order from the magnification side, of the sixth lens 51, the seventh lens 52, the eighth lens 53, the ninth lens 54, and the tenth lens 59. The sixth lens 51 is a negative cemented lens 51u (negative lens 51n) composed of a positive meniscus lens (positive lens 51a) and a negative meniscus lens (negative lens 51b). The seventh lens 52 is a positive meniscus 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) composed of a biconcave lens (negative lens 54a) and a biconvex lens (positive lens 54b). The tenth lens 59, forming a positive lens group 59g, is composed of a biconvex lens (positive lens 59p or positive lens 55).

[0178] Figure 9 Graphs showing longitudinal aberration characteristics (ie, spherical aberration characteristics, astigmatism characteristics, and distortion characteristics) of the fixed-focus lens 40 of Example 3. FIG.

[0179] (Example 4)

[0180] The overall specifications of the fixed focus lens 40 of Example 4 are shown below.

[0181] F=7.721(mm)

[0182] Fno=1.770

[0183] IH=11.000(mm)

[0184] TTL=125.559(mm)

[0185] LL=90.614(mm)

[0186] BF=25.433(mm)

[0187] LS=53.086(mm)

[0188] L1H=18.638(mm)

[0189] FG1=18.593(mm)

[0190] FG2=28.872(mm)

[0191] Table 7 below shows the data of the lens surface of Example 4.

[0192] [Table 7]

[0193]

[0194] Table 8 below shows the aspheric coefficients of the lens surface of Example 4.

[0195] [Table 8]

[0196]

[0197] Figure 10 4 is a cross-sectional view of a fixed focus lens 40 according to Example 4.

[0198] The fixed focus lens 40 magnifies the image on the display surface of the liquid crystal panel 29G and projects it onto the screen SC (see Figure 3 The fixed-focus lens 40 includes, in order from the screen SC on the magnification 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 substantially telecentric on the reduction side.

[0199] The first lens group G1 consists, in order from the magnification side, of 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 negative aspheric plastic 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) composed 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) composed 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).

[0200] The second lens group G2 consists, in order from the magnification side, of the sixth lens 51, the seventh lens 52, the eighth lens 53, the ninth lens 54, and the tenth lens 59. The sixth lens 51 is a negative cemented lens 51u (negative lens 51n) composed of a positive meniscus lens (positive lens 51a) and a biconcave lens (negative lens 51b). The seventh lens 52 is a glass biconvex 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) composed of a biconcave lens (negative lens 54a) and a biconvex lens (positive lens 54b). The tenth lens 59, forming a positive lens group 59g, is composed of a biconvex lens (positive lens 59p or positive lens 55).

[0201] Figure 11 Graphs showing longitudinal aberration characteristics (ie, spherical aberration characteristics, astigmatism characteristics, and distortion characteristics) of the fixed-focus lens 40 of Example 4.

[0202] For reference, Table 9 below shows Examples 1 to 4 corresponding to the conditional expressions (1) to (7).

[0203] [Table 9]

[0204] Example 1 Example 2 Example 3 Example 4 The value ω of conditional expression (1) 54.522 55.324 54.448 54.536 The value of conditional expression (2) is L1H / LL 0.164 0.302 0.197 0.206 The value of conditional expression (3) is BF / F 3.327 3.458 3.293 3.294 The value of conditional expression (4) is Fg1p / F 7.690 3.786 20.000 4.331 The value of conditional expression (5) is Fg2p1 / Fg2p2 0.428 0.226 1.050 0.503 The value of conditional expression (6) |Fg2n1 / Fg2p3-| 1.009 2.579 0.822 1.350 The value of conditional expression (7) LS / LL 0.499 0.536 0.559 0.585

[0205] [Other matters]

[0206] The structure described above is an example, and various changes can be made within the scope of achieving the same function.

[0207] For example, in each embodiment, one or more lenses having substantially no refractive power can be added before and after the lenses constituting each lens group G1 or G2.

[0208] Furthermore, the object of magnification and projection by the fixed focus lens 40 is not limited to the image formed by the liquid crystal panel, and an image formed by a light modulation element such as a digital micromirror device can be magnified and projected.

[0209] [Summary of the present disclosure]

[0210] The following is a summary of the present disclosure.

[0211] (Note 1)

[0212] A fixed focus lens, which is composed of a first lens group with positive refractive power, an aperture stop and a second lens group with positive refractive power in order from the magnification side to the reduction side.

[0213] 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.

[0214] The reduced side is telecentric,

[0215] The following conditions are met:

[0216] ω>45...(1)

[0217] 0.15 <L1H / LL<0.4…(2)

[0218] 2.5 <BF / F<3.5…(3)

[0219] Here, ω is the maximum half-field angle of the fixed-focus lens,

[0220] L1H is the height of the light that passes through the lens surface closest to the magnification side of the fixed focus lens with the maximum image height.

[0221] LL is the length of the fixed focus lens,

[0222] BF is the air conversion value of the back focal length.

[0223] F is the focal length of the entire fixed focus lens system.

[0224] By setting the refractive power of the first lens group in this fixed-focus lens to be positive, the overall length and maximum diameter of the fixed-focus lens can be reduced. By using an aspherical lens as the lens closest to the magnification side or as the second lens from the magnification side, correction of field curvature and distortion can be achieved while also achieving miniaturization.

[0225] Conditional expression (1) represents the widening of the angle of view of a fixed-focus lens.

[0226] Conditional equation (2) is a formula for miniaturizing the height direction of a fixed-focus lens. By setting the value L1H / LL in the above conditional equation to a value greater than the lower limit, miniaturization in the height direction can be achieved while effectively correcting field curvature and distortion. By setting the value L1H / LL in the above conditional equation to a value less than the upper limit, the height increase of the fixed-focus lens can be suppressed, thereby meeting product height requirements.

[0227] Conditional equation (3) is used to ensure an appropriate back focus. By setting the value BF / F in the conditional equation above the lower limit, the length required for inserts such as prisms can be ensured. By setting the value BF / F in the conditional equation below the upper limit, the lens length of the fixed-focus lens can be reduced and the angle of view can be widened.

[0228] (Note 2)

[0229] The fixed focus lens according to Supplementary Note 1, wherein the first lens group is composed of single lenses or cemented lenses having positive-positive and negative-negative refractive powers in order from the reduction side.

[0230] In order to spread light toward the magnification side of the first lens group, such a fixed-focus lens requires a structure in which negative lenses are arranged sequentially from the magnification side. For miniaturization, a positive lens is required on the reduction side. While a strong positive refractive power configuration is suitable for compact structures, it introduces aberrations, making it undesirable. In this structure, by arranging two lenses with positive refractive power on the reduction side, the amount of aberration generated by each positive lens is reduced, enabling miniaturization.

[0231] (Note 3)

[0232] The fixed focus lens according to Supplementary Note 1 or 2, wherein the second lens group is composed of single lenses or cemented lenses having negative-positive, positive-negative-positive refractive powers in order from the magnification side.

[0233] In the above configuration, since the first lens group has positive refractive power, it is preferable to use a negative lens to correct aberrations in the lens closest to the first lens group, on the magnification side. To achieve miniaturization, lenses with strong positive refractive power are used near the aperture stop. However, if the positive refractive power is shared by a single lens, aberration correction becomes difficult. Therefore, it is preferable to arrange the positive refractive power in a divided manner. To ensure telecentricity, a positive lens is required on the reduction side, and a negative lens is required to correct this.

[0234] (Note 4)

[0235] The fixed-focus lens according to any one of Supplementary Notes 1 to 3, wherein the second lens unit includes an aspherical lens having positive refractive power.

[0236] This effectively suppresses astigmatism, and enables reduction in lens diameter and cost compared to a case where the second lens unit is composed of only spherical lenses.

[0237] (Note 5)

[0238] The fixed focus lens according to any one of Supplementary Notes 1 to 4, wherein the lens closest to the magnification side in the second lens group is a negative cemented lens composed of lenses having positive and negative refractive powers.

[0239] This allows the fixed-focus lens to achieve a wider angle, be more compact, and suppress chromatic aberration.

[0240] (Note 6)

[0241] The fixed-focus lens according to any one of Supplementary Notes 1 to 5, wherein the fixed-focus lens satisfies the following conditional expression:

[0242] 3.0 <Fg1p / F<25.0…(4)

[0243] Here, Fg1p is the focal length of the lens closest to the reduction side in the first lens group.

[0244] Conditional equation (4) is a formula for miniaturization and aberration correction of fixed-focus lenses. By setting the value Fg1p / F in the conditional equation to a value greater than the lower limit, miniaturization can be maintained while facilitating aberration correction. By setting the value Fg1p / F in the conditional equation to a value less than the upper limit, aberration correction can be facilitated while achieving miniaturization.

[0245] (Note 7)

[0246] The fixed-focus lens according to any one of Supplementary Notes 1 to 6, wherein the fixed-focus lens satisfies the following conditional expression:

[0247] 0.2 <Fg2p1 / Fg2p2<1.2…(5)

[0248] Here, Fg2p1 is the focal length of the positive single lens or positive cemented lens disposed most on the magnification side in the second lens group.

[0249] Fg2p2 is the focal length of the positive single lens or positive cemented lens arranged on the second magnification side in the second lens group.

[0250] Conditional expression (5) represents the diopter distribution of the two positive lenses arranged on the magnification side in the second lens group. By satisfying conditional expression (5), various aberrations caused by miniaturization and widening of the fixed focus lens can be well corrected.

[0251] (Note 8)

[0252] The fixed-focus lens according to any one of Supplementary Notes 1 to 7, wherein the fixed-focus lens satisfies the following conditional expression:

[0253] 0.8<|Fg2n1 / Fg2p3-|<2.8…(6)

[0254] Here, Fg2n1 is the focal length of the negative single lens or negative cemented lens disposed most on the reduction side in the second lens group.

[0255] Fg2p3- is the focal length of the positive lens arranged on the reduction side of the negative single lens or the negative cemented lens, and the negative single lens or the negative cemented lens is arranged most on the reduction side in the second lens group.

[0256] Conditional equation (6) is used to correct telecentricity and chromatic aberration of magnification. By setting the value Fg2n1 / Fg2p3- in this conditional equation to a value greater than the lower limit, telecentricity can be ensured. By setting the value Fg2n / Fg2p3- in this conditional equation to a value less than the upper limit, chromatic aberration of magnification can be effectively corrected.

[0257] (Note 9)

[0258] The fixed-focus lens according to any one of Supplementary Notes 1 to 8, wherein the fixed-focus lens satisfies the following conditional expression:

[0259] 0.45 <LS / LL<0.65…(7)

[0260] Here, LS is the distance from the lens surface closest to the magnification side of the fixed focus lens to the aperture stop.

[0261] Conditional expression (7) is related to miniaturization of the lens diameter and telecentricity. By setting the value LS / LL of the conditional expression above the lower limit, telecentricity can be ensured. By setting the value LS / LL of the conditional expression below the upper limit, miniaturization of the lens diameter can be achieved.

[0262] (Note 10)

[0263] A projector includes: an image forming unit including a light modulating element for modulating light from a light source device to form image light; and

[0264] The fixed focus lens according to any one of Supplementary Notes 1 to 9 projects image light from an image forming unit.

[0265] This makes it possible to reduce the size of a projector including a fixed-focus lens.

Claims

1. A fixed-focus lens, which consists of, in order from the magnification side to the reduction side, a first lens group with positive refractive power, an aperture stop, and a second lens group with 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 reduced side is telecentric, The following conditions are met: ω>45…(1) 0.15 <L1H / LL<0.4…(2) 2.5 <BF / F<3.5…(3) Here, ω is the maximum half-field angle of the fixed-focus lens, L1H is the height of the light ray passing through the maximum image height on the lens surface closest to the magnification side of the fixed focus lens. LL is the length of the fixed focus lens, BF is the air conversion value of the back focal length. F is the focal length of the entire fixed focus lens system.

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

3. The fixed focus lens according to claim 1, wherein: The second lens group is composed of single lenses or cemented lenses having negative-positive-positive-negative-positive refractive powers in order from the magnification side.

4. The fixed focus lens according to claim 1, wherein: The second lens unit includes an aspherical lens having positive refractive power.

5. The fixed focus lens according to claim 1, wherein: The lens closest to the magnification side in the second lens group is a negative cemented lens composed of lenses having positive and negative refractive powers.

6. The fixed focus lens according to claim 1, wherein: The fixed focus lens satisfies the following conditional formula: 3.0 <Fg1p / F<25.0…(4) Here, Fg1p is the focal length of the lens closest to the reduction side in the first lens group.

7. The fixed focus lens according to claim 1, wherein: The fixed focus lens satisfies the following conditional formula: 0.2 <Fg2p1 / Fg2p2<1.2…(5) Here, Fg2p1 is the focal length of the positive single lens or positive cemented lens disposed most on the magnification side in the second lens group. Fg2p2 is the focal length of the positive single lens or positive cemented lens arranged on the second magnification side in the second lens group.

8. The fixed focus lens according to claim 1, wherein: The fixed focus lens satisfies the following conditional formula: 0.8<|Fg2n1 / Fg2p3-|<2.8…(6) Here, Fg2n1 is the focal length of the negative single lens or negative cemented lens disposed most on the reduction side in the second lens group. Fg2p3- is the focal length of the positive lens arranged on the reduction side relative to the negative single lens or the negative cemented lens, and the negative single lens or the negative cemented lens is arranged on the closest reduction side in the second lens group.

9. The fixed focus lens according to claim 1, wherein: The fixed focus lens satisfies the following conditional formula: 0.45 <LS / LL<0.65…(7) Here, LS is the distance from the lens surface closest to the magnification side of the fixed focus lens to the aperture stop.

10. A projector comprising: an image forming unit including a light modulating element for modulating light from a light source device to form image light; and The fixed focus lens according to any one of claims 1 to 9, which projects the image light from the image forming section.

Images