projection lens

Abstract

A projection lens includes a first lens group and a second lens group in order from a magnifying side to a reducing side. The first lens group and the second lens group are separated by a minimum inner diameter of a lens barrel. The first lens group includes 4 to 6 spherical lenses, and the refractive power of the first lens group is negative. The second lens group includes 4 to 6 lenses, one of which is an aspherical lens, and the refractive power of the second lens group is positive. The transmittance of the projection lens at a wavelength of 365 nm is greater than or equal to 75%.

Description

TECHNICAL FIELD

[0001] The present application relates to a lens, in particular to a fixed focus projection lens. BACKGROUND

[0002] Optical lenses are usually applied to image taking or projection, and thus the waveband used is usually visible light or infrared light. However, with the progress of technology, products applied to ultraviolet light are gradually increasing. For example, 3D printers using ultraviolet light sources. Therefore, there is an urgent need to develop optical lenses that can provide good imaging or image taking effects and provide smaller aberrations. SUMMARY

[0003] The present application is directed to a projection lens that can provide good optical effects in the ultraviolet light waveband.

[0004] The projection lens of one embodiment of the present application sequentially includes a first lens group and a second lens group from the magnification side to the reduction side. The first lens group and the second lens group are separated by the minimum inner diameter of the lens barrel. The first lens group includes 4 to 6 spherical lenses, and the refractive power of the first lens group is negative. The second lens group includes 4 to 6 lenses, one of which is an aspherical lens, and the refractive power of the second lens group is positive. The transmittance of the projection lens at a wavelength of 365 nm is greater than or equal to 75%.

[0005] The projection lens of one embodiment of the present application sequentially includes a first lens group and a second lens group from the magnification side to the reduction side. The first lens group is composed of 3 to 5 spherical lenses, the refractive power of the first lens group is negative, and the first lens group is disposed in a first lens barrel. The second lens group includes an aspherical lens and is composed of 5 to 7 lenses. The refractive power of the second lens group is positive, and the second lens group is disposed in a second lens barrel. The transmittance of the projection lens at a wavelength of 365 nm is greater than or equal to 75%.

[0006] Based on the above, since the transmittance of the projection lens of one embodiment of the present application at a wavelength of 365 nm is greater than or equal to 75%, the projection lens is suitable for use in the ultraviolet light waveband. BRIEF DESCRIPTION OF DRAWINGS

[0007] Figure 1 shows a cross-sectional schematic view of a projection lens of a first embodiment of the present application;

[0008] Figure 2 shows a cross-sectional schematic view of a projection lens of a second embodiment of the present application;

[0009] Figure 3 shows a cross-sectional schematic view of a projection lens of a third embodiment of the present application;

[0010] Figure 4 A cross-sectional view of a projection lens according to a fourth embodiment of the present application. DETAILED DESCRIPTION

[0011] Reference will now be made in detail embodiments of the application, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.

[0012] Figure 1 A cross-sectional view of a projection lens according to a first embodiment of the present application. Please refer to Figure 1 In this embodiment, the projection lens 100 comprises a lens group G1 and a lens group G2 in sequence from the magnification side Al to the demagnification side A2.

[0013] In this embodiment, the lens group G1 (may be referred to as a first lens group) comprises 4 to 6 spherical lenses, and the refractive power of the lens group G1 is negative. In detail, the lens group G1 comprises a lens LI (may be referred to as a first lens), a lens L2 (may be referred to as a second lens), a lens L3 (may be referred to as a third lens), a lens L4 (may be referred to as a fourth lens), a lens L5 (may be referred to as a fifth lens), and a lens L6 (may be referred to as a sixth lens) in sequence from the magnification side Al to the demagnification side A2 along the optical axis I. The lenses LI to L6 of the lens group G1 are all glass spherical lenses. In addition, the refractive powers of the lenses LI to L6 are positive, negative, negative, negative, positive, and positive, respectively.

[0014] In another embodiment, the lens group G1 can also be composed of 3 to 5 spherical lenses, for example Figure 4 the projection lens 400.

[0015] In this embodiment, the lens group G2 (may be referred to as a second lens group) comprises 4 to 6 lenses. The refractive power of the lens group G2 is positive, and one of the lenses of the lens group G2 is an aspherical lens. In detail, the lens group G2 comprises a lens L7 (may be referred to as a seventh lens), a lens L8 (may be referred to as an eighth lens), a lens L9 (may be referred to as a ninth lens), and a lens L10 (may be referred to as a tenth lens) in sequence from the magnification side Al to the demagnification side A2 along the optical axis I. The lenses L7 to L9 of the lens group G2 are all glass spherical lenses. The lens L10 is designed as a glass aspherical lens to eliminate optical aberration. In addition, the refractive powers of the lenses L7 to L10 are negative, positive, positive, and positive, respectively.

[0016] In another embodiment, the lens group G2 can also be composed of 5 to 7 lenses, for example Figure 4 the projection lens 400.

[0017] In the present embodiment, the lens group G1 is disposed in a lens barrel B1 (which can be referred to as a first lens barrel), and the lens group G2 is disposed in a lens barrel B2 (which can be referred to as a second lens barrel). The projection lens 100 further includes a main barrel MB, and the lens barrel B1 and the lens barrel B2 are disposed in the main barrel MB. Here, the lens barrel B1 covers the lens barrel B2, and the main barrel MB covers the lens barrel B1 and the lens barrel B2. Further, the lens group G1 and the lens group G2 are separated by the minimum inner diameter of the lens barrel. The minimum inner diameter of the lens barrel is, for example, the position of the stop S between the lens L6 and the lens L7.

[0018] In one embodiment, the projection lens 100 includes ten lenses whose refractive powers, in order from the magnification side Al to the reduction side A2, are positive, negative, negative, negative, positive, positive, negative, positive, positive, and positive.

[0019] In the present embodiment, since the projection lens 100 is designed to have good optical performance in the ultraviolet light wavelength band, the projection lens 100 preferably does not have a cemented lens. That is, the lenses of the projection lens 100 are preferably maintained at a distance from each other by a mechanism.

[0020] In the present embodiment, the transmittance of the projection lens 100 at a wavelength of 365 nm is equal to or greater than 75%. Further, the material of each lens of the projection lens 100 has a transmittance of equal to or greater than 80% at a wavelength of 365 nm and a thickness of 10 mm, so that the projection lens 100 is suitable for use in the ultraviolet light wavelength band.

[0021] In the present embodiment, the projection lens 100 satisfies the following conditional expression: 13 ≦ TTL / H ≦ 21, where TTL is the total length of the projection lens 100, and H is the image height of the imaging surface of the projection lens 100 on the reduction side A2, where the imaging surface is, for example, the position of the digital micromirror device 150.

[0022] In the present embodiment, the throw ratio of the projection lens 100, which is the ratio of the distance between the projection lens 100 and the projection screen on the magnification side Al (projection distance) to the width of the projection screen, is 1.0.

[0023] In the present embodiment, the F-number (Fno) of the projection lens 100 is 2.2.

[0024] In the present embodiment, the lens group G1 and the lens group G2 are each variable with respect to the distance between the imaging surfaces on the reduction side A2.

[0025] In the present embodiment, the optical distortion of the projection lens 100 is less than 0.25%.

[0026] In the present embodiment, the effective focal length (EFL) of the projection lens 100 is greater than or equal to 8 and less than or equal to 14.

[0027] In the present embodiment, the actual design of each element is shown in Table 1 below.

[0028] Table 1

[0029]

[0030] Please refer to Table 1 simultaneously. Figure 1 In the present embodiment, the projection lens 100 has the following arrangement: the lens L1 has the surface S3 and the surface S4 in sequence from the magnification side A1 to the reduction side A2; the lens L2 has the surface S5 and the surface S6 in sequence from the magnification side A1 to the reduction side A2; and so on. The surface corresponding to each element is not repeated here. The aperture S and the display surface of the digital micromirror device (DMD) 150 are represented by the surface S15 and the surface S30, respectively, and the radius of curvature of each is infinite (i.e., a plane perpendicular to the optical axis I).

[0031] In addition, the interval in Table 1 is the interval between the surface and the next surface from the magnification side A1 to the reduction side A2. For example, the thickness of the lens L1 is 2.96E+00 mm, the distance between the lens L1 and the lens L2 is 1.00E-01 mm, the thickness of the lens L2 is 1.37E+00 mm, the distance between the lens L2 and the lens L3 is 3.36E+00 mm, and so on.

[0032] In the present embodiment, the effective focal length (EFL) of the projection lens 100 is greater than or equal to 8 and less than or equal to 14.

[0033] In the embodiment, the total length (TTL, the distance from the surface S3 of the lens L1 to the surface S23 of the lens L10) of the projection lens 100 is 76.98 mm. The field of view (FOV) of the projection lens 100 is 50.38 degrees, and the effective focal length (EFL) of the projection lens 100 is 8.37 mm.

[0034] In the embodiment, the interval between two lenses of the projection lens 100 is less than or equal to 0.01 mm, and the two lenses are non-cemented lenses. For example, the interval between the lens L7 and the lens L8 is 0.001 mm. Since the projection lens 100 is designed to have good optical effects in the ultraviolet light waveband, the two lenses with an interval less than or equal to 0.01 mm in the projection lens 100 are non-cemented lenses, and the interval is preferably maintained by a mechanism.

[0035] Further, in the embodiment, a digital micro-mirror device 150 with a smaller size can be used, and a transmissive smooth picture (TSP) 120 is used to replace the existing high-specification product, thereby saving costs. The TSP 120 is a flat plate, which can make the pixel points of the projected image slightly blurred by vibration to avoid the granular appearance of the pixels being observed by the user.

[0036] Table 2 below lists the quadratic surface coefficient value K and the non-spherical surface coefficients of the surface S22 and the surface S23 of the lens L10. The non-spherical surface polynomial can be expressed by the following formula:

[0037]

[0038] where x is the offset (sag) in the optical axis I direction, c' is the reciprocal of the radius of the osculating sphere, that is, the reciprocal of the radius of curvature near the optical axis, K is the quadratic surface coefficient, y is the non-spherical surface height, that is, the height from the center of the lens to the edge of the lens. A-G represent the non-spherical surface coefficients of the non-spherical surface polynomial.

[0039] Table 2

[0040]

[0041] Based on the above, since the transmittance of the projection lens 100 of the embodiment of the present application at a wavelength of 365 nm is greater than or equal to 75%, the projection lens 100 is suitable for use in the ultraviolet light waveband. Further, the lens group G2 includes a non-spherical lens for eliminating optical aberration, so that the projection lens 100 can provide good optical effects.

[0042] The following describes a projection lens of a second embodiment of the present application, the actual designs of the elements of which can be seen from the following Table 3.

[0043] Table 3

[0044]

[0045] Figure 2 A cross-sectional schematic diagram of a projection lens of a second embodiment of the present application is shown. Reference is made simultaneously to Figure 2 and Table 3. In this embodiment, the projection lens 200 comprises nine lenses, the refractive powers of which, from the magnifying side Al to the reducing side A2, are positive, negative, negative, positive, positive, negative, positive, positive, and positive, respectively. In addition, the stop S is disposed between the lens L5 and the lens L6.

[0046] In this embodiment, the lens LI is a positive meniscus lens with the concave surface facing the reducing side A2; the lens L2 is a negative meniscus lens with the concave surface facing the reducing side A2; the lens L3 is a double concave lens; the lens L4 is a positive meniscus lens with the concave surface facing the magnifying side Al; the lens L5 is a positive meniscus lens with the concave surface facing the magnifying side Al; the lens L6 is a negative meniscus lens with the concave surface facing the magnifying side Al; the lens L7 is a positive meniscus lens with the concave surface facing the magnifying side Al; the lens L8 is a double convex lens; and the lens L9 is a double convex lens.

[0047] It is worth mentioning that in the embodiment of Table 3, the total length of the projection lens 200 is 74.47 mm (the sum of the interval values of the surfaces S3 to S21 in Table 3). The angle of view of the projection lens 200 is 50.37 degrees, and the effective focal length of the projection lens 200 is 8.37 mm.

[0048] The following Table 4 lists the quadratic surface coefficient values K and the aspheric surface coefficients of each order of the surface S20 and the surface S21 of the lens L9, wherein the aspheric surface equation can refer to the above formula (1).

[0049] Table 4

[0050]

[0051] The following describes a projection lens of a third embodiment of the present application, the actual designs of the elements of which can be seen from the following Table 5.

[0052] Table 5

[0053]

[0054] Figure 3 A cross-sectional schematic diagram of a projection lens of a third embodiment of the present application is shown. Reference is made simultaneously to Figure 3Table V. In this embodiment, the projection lens 300 comprises ten lenses whose refractive powers from the magnifying side Al to the reducing side A2 are in sequence positive, negative, negative, positive, positive, negative, negative, positive, positive, positive. In addition, the stop S is disposed between the lens L5 and the lens L6. The interval between the lens L7 and the lens L8 is 0.001 millimeter.

[0055] In this embodiment, the lens LI is a concave reducing side A2 positive meniscus lens; the lens L2 is a concave negative meniscus lens facing the reducing side A2; the lens L3 is a double concave lens; the lens L4 is a double convex lens; the lens L5 is a double convex lens; the lens L6 is a double concave lens; the lens L7 is a plano-concave lens; the lens L8 is a plano-convex lens; the lens L9 is a double convex lens; the lens LIO is a double convex lens.

[0056] It is worth mentioning that in the embodiment of Table V, the total length of the projection lens 300 is 80.26 millimeters (the sum of the interval values of the surface S3 to the surface S23 in Table V). The angle of view of the projection lens 300 is 48.00 degrees, and the effective focal length of the projection lens 300 is 13.00 millimeters.

[0057] The following Table VI lists the quadratic surface coefficient values K and the non-spherical surface coefficients of each order of the surface S22 and the surface S23 of the lens LIO, wherein the non-spherical surface equation can refer to the above formula (1).

[0058] Table VI

[0059]

[0060] The following will illustrate the projection lens of the fourth embodiment of the present application, and the actual design of each element can be seen from the following Table VII.

[0061] Table VII

[0062]

[0063] Figure 4 shows a cross-sectional schematic view of the projection lens of the fourth embodiment of the present application. Meanwhile, reference is made to Figure 4 Table VII. In this embodiment, the projection lens 400 comprises ten lenses whose refractive powers from the magnifying side Al to the reducing side A2 are in sequence positive, negative, negative, positive, positive, negative, negative, positive, positive, positive. In addition, the stop S is disposed between the lens L5 and the lens L6. The interval between the lens L7 and the lens L8 is 0.001 millimeter.

[0064] In this embodiment, the lens LI is a plano-convex lens; the lens L2 is a concave negative meniscus lens facing the reducing side A2; the lens L3 is a double concave lens; the lens L4 is a double convex lens; the lens L5 is a double convex lens; the lens L6 is a double concave lens; the lens L7 is a plano-concave lens; the lens L8 is a plano-convex lens; the lens L9 is a double convex lens; the lens LIO is a double convex lens.

[0065] In the example of Table 7, the total length of the projection lens 400 is 76.51 mm (the sum of the interval values of surfaces S3 to S23 in Table 7). The angle of view of the projection lens 400 is 50.08 degrees, and the effective focal length of the projection lens 400 is 12.7 mm.

[0066] Table 8 below lists the quadratic surface coefficient values K and the aspheric surface coefficients of surface S22 and surface S23 of the lens L10, wherein the aspheric surface equation can refer to the above formula (1).

[0067] Table 8

[0068]

[0069] In some embodiments of the present application, the F-number of the projection lens is greater than 2.2, and the optical distortion is less than 0.25%, which is preferable. In the lens structure, the transmittance of the single lens under 365 nm wavelength light irradiation is greater than 80%, the lens does not use cemented lenses, and the distance between the first lens group and the second lens group relative to the reduced side of the imaging surface of the lens is variable, which is more preferable.

[0070] In summary, since the transmittance of the projection lens of an embodiment of the present application under 365 nm wavelength is greater than or equal to 75%, the projection lens is suitable for use in the ultraviolet light band. Furthermore, the second lens group includes an aspheric lens for eliminating optical aberration, so that the projection lens can provide good optical effects.

[0071] Although the above embodiments of the present application are described, modifications can be made by those skilled in the art without changing the essential conditions, for example, in order to increase the manufacturing feasibility, a piece of lens with high curvature and large thickness is replaced by two pieces of lens; or in order to reduce the volume and cost, two pieces of lens are reduced to one piece of lens. Therefore, the number of lenses in the present application can be generally adjusted by those skilled in the art without changing the essential conditions, and is not limited to the number of lenses in the embodiments. The number of lenses in the claims is an equivalent alternative or obvious modification that can be reasonably predicted by those skilled in the art from the embodiments of the specification, and has the same performance or purpose. The scope of protection of the invention should be determined according to the content of the claims.

[0072] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A projection lens, characterized in that, include: From the magnifying side to the reducing side, it includes a first lens group and a second lens group in sequence; The first lens group and the second lens group are separated by the minimum inner diameter of the lens barrel; The first lens group includes 5 spherical lenses. The refractive power of the first lens group is negative, and the refractive power of the 5 spherical lenses in the first lens group is positive, negative, negative, positive and positive in sequence from the magnification side to the reduction side. The second lens group includes four lenses, one of which is an aspherical lens. The refractive power of the second lens group is positive, and the refractive power of the four lenses in the second lens group is negative, positive, positive and positive in sequence from the magnifying side to the reducing side. The projection lens has a transmittance of 75% or greater at a wavelength of 365 nanometers. The lens closest to the magnification side among all the lenses of the projection lens has positive refractive power; and The lens closest to the minimum inner diameter in the second lens group has a negative refractive power, wherein the distance between two lenses in the projection lens is less than or equal to 0.01 mm, and the two lenses are non-cemented lenses.

2. A projection lens, characterized in that, From the magnifying side to the reducing side, the lenses sequentially include a first lens group and a second lens group, wherein... The first lens group includes five spherical lenses. The refractive power of the first lens group is negative. The first lens group is disposed inside the first lens barrel. The refractive power of the five spherical lenses in the first lens group is positive, negative, negative, positive and positive in sequence from the magnification side to the reduction side. The second lens group includes an aspherical lens, the second lens group includes 4 lenses, the refractive power of the second lens group is positive, the second lens group is disposed inside the second lens barrel, and the refractive power of the 4 lenses of the second lens group is negative, positive, positive and positive in sequence from the magnification side to the reduction side; The projection lens has a transmittance of 75% or greater at a wavelength of 365 nanometers. The lens closest to the magnification side among all the lenses of the projection lens has positive refractive power; and The lens closest to the magnifying side among all the lenses in the second lens group has a negative refractive power, wherein the effective focal length of the projection lens is greater than or equal to 8 and less than or equal to 14.

3. The projection lens according to claim 2, characterized in that, The first lens group is disposed inside the first lens barrel, the second lens group is disposed inside the second lens barrel, and the second lens barrel is covered by the first lens barrel.

4. The projection lens according to claim 3, characterized in that, It also includes a main lens barrel, and the first lens barrel and the second lens barrel are disposed inside the main lens barrel.

5. The projection lens according to claim 1 or claim 2, characterized in that, The first lens group further includes an additional spherical lens, and the refractive power of the five spherical lenses of the first lens group plus the additional spherical lens is positive, negative, negative, negative, positive and positive in sequence from the magnification side to the reduction side.

6. The projection lens according to claim 1 or claim 2, characterized in that, The second lens group also includes an additional lens, and the refractive power of the four lenses of the second lens group plus the additional lens is negative, negative, positive, positive and positive in sequence from the magnifying side to the reducing side.

7. The projection lens according to claim 1 or claim 2, characterized in that, The distance between the first lens group and the second lens group of the projection lens relative to the imaging surface on the reduced side of the projection lens is variable.

8. The projection lens according to claim 1 or claim 2, characterized in that, All lenses in the first lens group are glass spherical lenses.

9. The projection lens according to claim 1 or claim 2, characterized in that, All the lenses in the projection lenses are glass lenses.

10. The projection lens according to claim 1 or claim 2, characterized in that, The projection lens satisfies the following condition: 13≦TTL / H≦21, where TTL is the total length of the projection lens and H is the image height of the projection lens on the reduced side of the imaging plane.

11. The projection lens according to claim 1 or claim 2, characterized in that, The projection ratio of the projection lens is 1.

0.

12. The projection lens according to claim 1 or claim 2, characterized in that, The aperture number of the projection lens is 2.

2.

13. The projection lens according to claim 1 or claim 2, characterized in that, The optical aberration of the projection lens is less than 0.25%.

14. The projection lens according to claim 1 or claim 2, characterized in that, The projection lens does not have a cemented lens.

15. The projection lens according to claim 1 or claim 2, characterized in that, The material of each lens of the projection lens has a transmittance of greater than or equal to 80% at a wavelength of 365 nanometers and a thickness of 10 millimeters.

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