Fixed focus projection lens module

Abstract

This invention provides a fixed-focus projection lens module for projecting an image beam provided by a light valve onto a screen. The fixed-focus projection lens module includes, sequentially from the screen side to the display side along the optical axis, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and a light-transmitting element. The first lens, second lens, third lens, fourth lens, and seventh lens have negative, positive, negative, positive, and positive refractive powers, respectively. The fixed-focus projection lens module satisfies: 1 < |OAL / BFL| < 2.1, where OAL is the distance on the optical axis from the screen side of the first lens to the display side of the seventh lens, BFL is the distance on the optical axis from the screen side of the light-transmitting element to the display surface of the light valve, and the light-transmitting element is the first optical element without refractive power located after the seventh lens along the optical axis from the screen side to the display side. The fixed-focus projection lens module provided by this invention is lightweight and simultaneously meets the requirements of high projection resolution.

Description

Technical Field

[0001] This invention relates to an optical lens, and more particularly to a fixed-focus projection lens module. Background Technology

[0002] With the development of modern technology, there is an increasing demand for lightweight, slim, and compact projectors, such as portable pocket projectors. In terms of lens design, to meet the requirements of a lightweight and compact projector, the lens must also be lightweight, slim, and compact while maintaining high resolution. However, most zoom lenses on the market today have an architecture with two or more lens groups. When focusing, the distance between multiple lens groups needs to be adjusted, making the zoom lens mechanism large and complex, increasing manufacturing costs and assembly difficulties. Furthermore, the use of glass lenses in current lenses also contributes to their relatively heavy weight. Summary of the Invention

[0003] This invention provides a fixed-focus projection lens module that meets the requirements of being lightweight, thin, and compact, while also meeting the requirements of high projection resolution.

[0004] Other objects and advantages of the present invention can be further understood from the technical features disclosed herein.

[0005] To achieve one, some, or all of the above objectives, or other objectives, an embodiment of the present invention provides a fixed-focus projection lens module for projecting an image beam provided by a light valve onto a screen. The fixed-focus projection lens module includes, sequentially from the screen side to the display side along the optical axis, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and a light-transmitting element. Each of the first lens to the light-transmitting element has a screen side facing the screen side and allowing the image beam to pass through, and a display side facing the display side and allowing the image beam to pass through. The first lens, second lens, third lens, fourth lens, and seventh lens have negative, positive, negative, positive, and positive refractive powers, respectively. The fixed-focus projection lens module satisfies: 1 < |OAL / BFL| < 2.1, where OAL is the distance on the optical axis from the screen side of the first lens to the display side of the seventh lens, BFL is the distance on the optical axis from the screen side of the light-transmitting element to the display surface of the light valve, and the light-transmitting element is the first optical element without refractive power located after the seventh lens along the optical axis from the screen side to the display side.

[0006] Based on the above, in one embodiment of the present invention, the fixed-focus projection lens module is designed as a single-group architecture including a first lens to a seventh lens, and conforms to 1 < |OAL / BFL| < 2.1. Compared with traditional fixed-focus lenses with normal projection ratios, the fixed-focus projection lens module architecture of the embodiment of the present invention is simpler, easier to assemble, and has a shorter manufacturing time than zoom lenses. Moreover, it can meet the requirements of being thin, short, and small while achieving high resolution (931p / mm).

[0007] To make the above features and advantages of the present invention more apparent and understandable, specific embodiments are described below in conjunction with the accompanying drawings. Attached Figure Description

[0008] Figure 1 This is a block diagram of a fixed-focus projection lens module on a screen, according to an embodiment of the present invention, in which an image beam provided by a light valve is projected onto the screen.

[0009] Figure 2 This is a schematic diagram of a fixed-focus projection lens module according to a first embodiment of the present invention.

[0010] Figure 3 for Figure 2 The modulation transfer function (MTF) diagram of the fixed-focus projection lens module.

[0011] Figure 4 for Figure 2 Lateral color diagram of a fixed-focus projection lens module.

[0012] Figures 5A to 5C for Figure 2 Field curvature and distortion aberration maps of a fixed-focus projection lens module.

[0013] Figures 6A to 6F They are respectively Figure 2 Transverse ray fan plot of a fixed-focus projection lens module at different image heights.

[0014] Figure 7 This is a schematic diagram of a fixed-focus projection lens module according to a second embodiment of the present invention.

[0015] Figure 8 for Figure 7 The modulation transfer function (MTF) diagram of the fixed-focus projection lens module. Detailed Implementation

[0016] The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of a preferred embodiment with reference to the accompanying drawings. The directional terms mentioned in the following embodiments (e.g., up, down, left, right, front, or back) are only for reference to the accompanying drawings. Therefore, the directional terms used are for illustrative purposes and not for limiting the present invention.

[0017] Figure 1 This is a block diagram of a fixed-focus projection lens module on a screen, according to an embodiment of the present invention, in which an image beam provided by a light valve is projected onto the screen. Figure 2 This is a schematic diagram of a fixed-focus projection lens module according to a first embodiment of the present invention. The fixed-focus projection lens module of this embodiment is applied, for example, in a projection device, but can also be applied in an image acquisition device; the present invention is not limited thereto. Please also refer to... Figure 1 and Figure 2 In this embodiment, the fixed-focus projection lens module 100 is specifically applied to a projection device, and the fixed-focus projection lens module 100 is used to project the image beam IB provided by the light valve 10 located on the display side A2 onto the screen 1000 located on the screen side A1. The fixed-focus projection lens module 100 includes, in sequence along the optical axis I from the screen side A1 to the display side A2, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, and a light-transmitting element 20.

[0018] In detail, the light valve 10 in this embodiment is, for example, a reflective light modulator such as a Liquid Crystal On Silicon panel (LCoS panel) or a Digital Micro-mirror Device (DMD). In some embodiments, the light valve 10 can also be a transmissive light modulator such as a Transparent Liquid Crystal Panel, an Electro-Optical Modulator, a Magneto-Optic Modulator, or an Acousto-Optic Modulator (AOM). This invention does not limit the type or form of the light valve 10.

[0019] In this embodiment, each of the first lens L1 to the light-transmitting element 20 has a screen side facing the screen side A1 and allowing the image beam IB to pass through (surfaces S1, S3, S5, S7, S9, S10, S12, and S14, respectively) and a display side facing the display side A2 and allowing the image beam to pass through (surfaces S2, S4, S6, S8, S10, S11, S13, and S15, respectively). The first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, and the seventh lens L7 form a lens group with an overall positive refractive power, wherein the first lens L1 to the seventh lens L7 have negative, positive, negative, positive, negative, positive, and positive refractive powers, respectively.

[0020] In this embodiment, the first lens L1 is a concave-convex lens with its convex surface facing the screen side A1, and it is a plastic aspherical lens with negative refractive power. The second lens L2 is a biconvex lens, and it is a glass spherical lens with positive refractive power. The third lens L3 is a biconcave lens, and it is a glass spherical lens with negative refractive power. The fourth lens L4 is a biconvex lens, and it is a glass spherical lens with positive refractive power. The fifth lens L5 and the sixth lens L6 form a first cemented doublet C1. The first cemented doublet C1 has positive refractive power, wherein the fifth lens L5 is a biconcave lens, the sixth lens L6 is a biconvex lens, both the fifth lens L5 and the sixth lens L6 are glass spherical lenses, and the fifth lens L5 has negative refractive power while the sixth lens L6 has positive refractive power. The seventh lens L7 is a biconvex lens, and it is a glass aspherical lens with positive refractive power.

[0021] Tables 1 and 2 below list data for a preferred embodiment of the fixed-focus projection lens module 100. However, the data listed below is not intended to limit the invention. Those skilled in the art, upon referring to the invention, may make appropriate modifications to the parameters or settings, but these modifications should still fall within the scope of the invention.

[0022] In this embodiment, the actual design of each of the aforementioned components can be seen in Table 1 below.

[0023] Table 1

[0024]

[0025]

[0026] In Table 1, the first lens L1 has surfaces S1 and S2 extending from the screen side A1 to the display side A2, and the second lens L2 has surfaces S3 and S4 sequentially extending from the screen side A1 to the display side A2. This pattern continues, and the surfaces corresponding to each element are not described again. The fifth lens L5 and the sixth lens L6 are a set of cemented lenses; therefore, surface S10 of the fifth lens L5 facing the display side A2 and surface S10 of the sixth lens L6 facing the screen side A1 are the same surface. Furthermore, in Table 1, "distance" refers to the distance between two adjacent surfaces along the optical axis I. For example, the distance corresponding to surface S1 is the distance between surface S1 and surface S2 along the optical axis I, while the distance corresponding to surface S2 is the straight-line distance between surface S2 and surface S3 along the optical axis I, and so on.

[0027] In this embodiment, surfaces S1 and S2 of the first lens L1 and surfaces S12 and S13 of the seventh lens L7 are aspherical, while the surfaces of the remaining lenses (second lens L2 to sixth lens L6) are spherical. The formula (1) for aspherical surfaces is as follows:

[0028] Formula (1):

[0029]

[0030] In formula (1) above, x is the offset (sag) in the optical axis direction, c' is the reciprocal of the radius of the oscillating sphere, which is the reciprocal of the radius of curvature near the optical axis I, K is the quadratic coefficient, and y is the aspheric height, which is the height from the center of the lens to the edge of the lens. AG represents the aspheric coefficients of each order of the aspheric polynomial. Table 2 lists the parameter values ​​of surfaces S1 and S2 of the first lens L1 and surfaces S12 and S13 of the seventh lens L7, where the second-order aspheric coefficient A' is 0.

[0031] Table 2

[0032]

[0033]

[0034] In this embodiment, the fixed-focus projection lens module 100 also includes a physical stop (ST). For example... Figure 2 As shown, the aperture stop ST is located on the optical axis I between the third lens L3 and the fourth lens L4.

[0035] In this embodiment, as Figure 2As shown, the light-transmitting element 20 is the first optical element without refractive power located along the optical axis I after the seventh lens L7, from the screen side A1 to the display side A2. The light-transmitting element 20 of the fixed-focus projection lens module 100 can be a flat glass actuator 110. The flat glass actuator 110 oscillates back and forth at a fixed position along a direction perpendicular to the optical axis I to change the transmission path of the image beam IB. Because the transmission path of the image beam IB is changed by the flat glass actuator 110, the user can see the superposition of images of the image beam IB at different positions on the screen 1000 within a short period of time, thus achieving an improved resolution of the projected image on the screen 1000.

[0036] In this embodiment, the fixed-focus projection lens module 100 also includes a prism 120 and a cover glass 130 sequentially along the optical axis I from the screen side A1 to the display side A2. The prism 120 and the cover glass 130 are located on the optical axis I between the seventh lens L7 and the light valve 10, and between the light-transmitting element 20 and the light valve 10.

[0037] In this embodiment, the fixed-focus projection lens module 100 is a telecentric projection lens module, and the aperture of the fixed-focus projection lens module 100 is less than or equal to 1.6.

[0038] In this embodiment, the fixed-focus projection lens module 100 satisfies: 1 < |OAL / BFL| < 2.1. Here, OAL is the distance on the optical axis I from the screen side of the first lens L1 to the display side of the seventh lens L7, that is, the distance on the optical axis I from the surface S1 of the first lens L1 facing the screen side A1 to the surface S13 of the seventh lens L7 facing the display side A2. And BFL is the distance on the optical axis I from the screen side of the light-transmitting element 20 to the display surface S20 of the light valve 10, that is, the distance on the optical axis I from the surface S14 of the light-transmitting element 20 facing the screen side A1 to the display surface S20 of the light valve 10. Furthermore, the fixed-focus projection lens module 100 can focus by changing the distance D, where distance D is the distance on the optical axis I from the surface S13 of the seventh lens L7 facing the display side A2 to the surface S14 of the light-transmitting element 20 facing the screen side A1. In other words, the distance D between surfaces S13 and S14 is variable. Moreover, thanks to the above design, when the distance between the screen side A1 and the display side A2 changes, the fixed-focus projection lens module 100 of this embodiment can effectively control the size and clarity of the projected image by changing the distance D.

[0039] Figure 3 for Figure 2 The modulation transfer function diagram of the fixed-focus projection lens module. Please refer to... Figure 3 ,exist Figure 3In the graph, the spatial frequency is 93.0000 cycles / mm, and it represents the modulation transfer function (MTF) of the fixed-focus projection lens module 100 at different image heights. The horizontal axis represents the focus shift, the vertical axis represents the modulus of the optical transfer function, T represents the curve in the tangential direction, S represents the curve in the sagittal direction, and the value next to "TS" represents the image height. Figure 3 It can be verified that the optical transfer function curve displayed by the fixed-focus projection lens module 100 in this embodiment is within the standard range, thus exhibiting good optical imaging quality.

[0040] Figure 4 for Figure 2 Lateral chromatic aberration diagram of a fixed-focus projection lens module. Figures 5A to 5C for Figure 2 Field curvature and distortion aberration diagram of a fixed-focus projection lens module. Figures 6A to 6F They are respectively Figure 2 The fixed-focus projection lens module displays the lateral beam fan pattern at different image heights. Figures 4 to 6F In the simulations, wavelengths of 460 nm, 525 nm, and 615 nm were used. Figure 5A In the diagram, multiple curves S represent the scattering curves of light of different wavelengths in the sagittal direction, while... Figure 5B In the diagram, multiple curves T represent the image scattering curves of light of different wavelengths along the meridional direction. Figures 6A to 6F In the diagram, the horizontal axis (Py and Px axes) represents the position of the reference ray in the tangential and sagittal directions after passing through the pupil and being normalized. The vertical axis (ey and ex axes) represents the height difference between the reference ray and the principal ray of the field of view on the image plane. The maximum and minimum scales of the ey and ex axes are both ±20 micrometers, and the maximum and minimum scales of the Py and Px axes are both ±1 micrometer. Figures 4 to 6F The displayed graphics are all within the standard range, which verifies that the fixed-focus projection lens module 100 of this embodiment can exhibit good imaging quality.

[0041] Figure 7 This is a schematic diagram of a fixed-focus projection lens module according to a second embodiment of the present invention. Please refer to... Figure 7 , Figure 7 Fixed-focus projection lens module 100' and Figure 2The fixed-focus projection lens module 100 is generally similar, with the main differences as follows. In this embodiment, the fifth lens L5 and the sixth lens L6 have positive and negative refractive powers, respectively. In addition, both the first lens L1 and the fifth lens L5 are plastic aspherical lenses. The second lens L2 and the third lens L3 form a first cemented doublet C1'. The first cemented doublet C1' has positive refractive power, wherein the second lens L2 and the third lens L3 are both concave-convex lenses with their convex surfaces facing the display side A2. The fifth lens L5 is a concave-convex lens with its convex surface facing the display side A2. The sixth lens L6 and the seventh lens L7 form a second cemented doublet C2'. The second cemented doublet C2' has positive refractive power, wherein the sixth lens L6 is a concave-convex lens with its convex surface facing the screen side A1, and the seventh lens L7 is a biconvex lens.

[0042] Tables 3 and 4 below list data for a preferred embodiment of the fixed-focus projection lens module 100'. However, the data listed below is not intended to limit the invention. Any person skilled in the art, upon referring to this invention, may make appropriate changes to its parameters or settings, which should still be within the scope of this invention.

[0043] In this embodiment, the actual design of each of the aforementioned components can be seen in Table 3 below.

[0044] Table 3

[0045]

[0046]

[0047] In Table 3, the second lens L2 and the third lens L3 are a cemented lens pair. Therefore, the surface S4 of the second lens L2 facing the display side A2 and the surface S4 of the third lens L3 facing the screen side A1 are the same surface. The sixth lens L6 and the seventh lens L7 are a cemented lens pair. Therefore, the surface S11 of the sixth lens L6 facing the display side A2 and the surface S11 of the seventh lens L7 facing the screen side A1 are the same surface. The display surface of the light valve 10 is surface S19'.

[0048] Table 4 lists the parameter values ​​of surfaces S1 and S2 of the first lens L1 and surfaces S8 and S9 of the fifth lens L5, where the second-order aspherical coefficient A' is 0.

[0049] Table 4

[0050]

[0051]

[0052] In addition, in this embodiment, the light-transmitting element 20' of the fixed-focus projection lens module 100' is a prism 120. Furthermore, as... Figure 7As shown, the flat glass actuator 110 and the protective glass 130 are located on the optical axis I between the seventh lens L7 and the light valve 10, and between the light-transmitting element 20' and the light valve 10.

[0053] Figure 8 for Figure 7 The modulation transfer function diagram of the fixed-focus projection lens module. Please refer to... Figure 8 ,Depend on Figure 8 It can be verified that the optical transfer function curve displayed by the fixed-focus projection lens module 100' in this embodiment is within the standard range, thus exhibiting good optical imaging quality.

[0054] In summary, in one embodiment of the present invention, the fixed-focus projection lens module is designed as a single-group architecture comprising a first lens to a seventh lens, and conforms to 1 < |OAL / BFL| < 2.1. Compared to traditional fixed-focus lenses with normal projection ratios, the fixed-focus projection lens module architecture of this embodiment is simpler and easier to assemble. Compared to zoom lenses, the fixed-focus projection lens module of this embodiment has a shorter manufacturing time and lower complexity. Furthermore, during focusing, because the lens group in this invention is a single-group architecture and the distance between lenses remains constant, it has a fixed effective focal length, and no additional space is needed between lenses to change the distance. Therefore, the fixed-focus projection lens module of this embodiment conforms to the characteristic of 1 < |OAL / BFL| < 2.1, achieving the requirements of high resolution (93 lp / mm) while also being thin, short, and small.

[0055] In addition, the fixed-focus projection lens module of the embodiments of the present invention can also achieve the following effects and advantages:

[0056] I. The fixed-focus projection lens module of this invention has an aperture of less than or equal to 1.6, which has high light energy utilization efficiency under the same light source intensity.

[0057] Second, designing at least one of the lenses (e.g., the first lens or the fifth lens) that is far from the light source of the projection device as a plastic lens can not only reduce the weight of the fixed-focus projection lens module in the embodiments of the present invention, but also increase the temperature that the fixed-focus projection lens module can withstand.

[0058] Third, by designing the distance D between the lens and the light-transmitting element to be variable, the focusing structure of the fixed-focus projection lens module is simplified, and the cost of the fixed-focus projection lens module in this embodiment of the invention is reduced.

[0059] Fourth, designing the first lens and the seventh or fifth lens as aspherical lenses can effectively reduce aberrations and improve imaging resolution.

[0060] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. Any simple equivalent changes and modifications made in accordance with the claims and specification of the present invention are still within the scope of this patent. Furthermore, no embodiment or claim of the present invention needs to achieve all the objectives, advantages, or features disclosed in the present invention. In addition, the abstract and title of the invention are used only to assist in patent document retrieval and are not intended to limit the scope of the invention. Furthermore, the terms "first," "second," etc., mentioned in this specification or claims are only used to name elements or distinguish different embodiments or scopes, and are not used to limit the upper or lower limit of the number of elements.

[0061] List of reference numerals

[0062] 10: Light valve

[0063] 20, 20': Light-transmitting element

[0064] 100, 100': Fixed-focus projection lens module

[0065] 110: Flat glass actuator

[0066] 120: Prism

[0067] 130: Protective Glass

[0068] 1000: Screen

[0069] A1: Screen side

[0070] A2: Display side

[0071] BFL, D, OAL: Distance

[0072] C1, C1': First cemented doublet lens

[0073] C2': Second cemented doublet lens

[0074] IB: Image Beam

[0075] L1: First lens

[0076] L2: Second lens

[0077] L3: Third lens

[0078] L4: Fourth Lens

[0079] L5: Fifth Lens

[0080] L6: Sixth Lens

[0081] L7: Seventh Lens

[0082] I: optical axis

[0083] S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15, S16, S17, S18, S19: Surface

[0084] S19', S20: Display surface

[0085] ST: Light Barrier.

Claims

1. A fixed-focus projection lens module for projecting an image beam provided by a light valve onto a screen, characterized in that, The fixed-focus projection lens module includes a lens group and a light-transmitting element. The lens group consists of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged sequentially along the optical axis from the screen side to the display side. Each of the first lens to the light-transmitting element has a screen side facing the screen side and allowing the image beam to pass through, and a display side facing the display side and allowing the image beam to pass through, wherein: The first lens, the second lens, the third lens, the fourth lens, and the seventh lens have negative, positive, negative, positive, and positive refractive powers, respectively. The first lens is an aspherical lens and is the lens with refractive power in the lens group that is closest to the screen side. The fixed-focus projection lens module conforms to: 1<|OAL / BFL∣<2.1, Wherein, OAL is the distance on the optical axis from the screen side of the first lens to the display side of the seventh lens, BFL is the distance on the optical axis from the screen side of the light-transmitting element to the display surface of the light valve, and the light-transmitting element is the first optical element without refractive power located on the optical axis after the seventh lens from the screen side to the display side.

2. The fixed-focus projection lens module according to claim 1, characterized in that, The light-transmitting element is a flat glass actuator or a prism.

3. The fixed-focus projection lens module according to claim 1, characterized in that, The fifth lens and the sixth lens have negative and positive refractive powers, respectively.

4. The fixed-focus projection lens module according to claim 1, characterized in that, The fifth lens and the sixth lens form a first cemented doublet lens, the first cemented doublet lens having positive refractive power, wherein the fifth lens is a biconcave lens and the sixth lens is a biconvex lens.

5. The fixed-focus projection lens module according to claim 1, characterized in that, The first lens is a concave-convex lens with its convex surface facing the screen side, the third lens is a biconcave lens, and the fourth lens is a biconvex lens.

6. The fixed-focus projection lens module according to claim 1, characterized in that, The first lens is a plastic lens.

7. The fixed-focus projection lens module according to claim 1, characterized in that, The seventh lens is a glass aspherical lens.

8. The fixed-focus projection lens module according to claim 1, characterized in that, The fifth lens and the sixth lens have positive and negative refractive powers, respectively.

9. The fixed-focus projection lens module according to claim 1, characterized in that, The second lens and the third lens form a first cemented doublet lens, which has positive diopter. Both the second lens and the third lens are concave-convex lenses with their convex surfaces facing the display side.

10. The fixed-focus projection lens module according to claim 1, characterized in that, The sixth lens and the seventh lens form a second cemented doublet lens, the second cemented doublet lens having positive refractive power, wherein the sixth lens is a concave-convex lens with its convex surface facing the screen side, and the seventh lens is a biconvex lens.

11. The fixed-focus projection lens module according to claim 1, characterized in that, The first lens and the fifth lens are plastic aspherical lenses.

12. The fixed-focus projection lens module according to claim 1, characterized in that, When the fixed-focus projection lens module focuses, the fixed-focus projection lens module is used to change the distance D, wherein the distance D is the distance on the optical axis from the display side of the seventh lens to the screen side of the light-transmitting element.

13. The fixed-focus projection lens module according to claim 1, characterized in that, The aperture of the fixed-focus projection lens module is less than or equal to 1.

6.

14. The fixed-focus projection lens module according to claim 1, characterized in that, The fixed-focus projection lens module also includes an aperture stop located on the optical axis between the third lens and the fourth lens.

15. The fixed-focus projection lens module according to claim 1, characterized in that, The fixed-focus projection lens module is a telecentric projection lens module.

16. The fixed-focus projection lens module according to claim 1, characterized in that, The fixed-focus projection lens module also includes a prism located on the optical axis between the seventh lens and the light valve.

17. The fixed-focus projection lens module according to claim 1, characterized in that, The fixed-focus projection lens module also includes a protective glass located on the optical axis between the seventh lens and the light valve.

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