A zoom objective lens system for microprojection

Abstract

The present invention provides a zoom objective lens system for micro projection, comprising: a first group of lenses, a diaphragm, a second group of lenses, a galvanometer, a beam splitter, a protective glass and an imaging surface arranged in sequence; the imaging surface is used for emitting light; the galvanometer is used for imaging pixels; the beam splitter is used for splitting the light; the diaphragm is used for controlling the light incident amount of the split light; both the first group of lenses and the second group of lenses are used for correcting aberrations. The present invention improves the imaging quality, enhances the versatility of the objective lens system, reduces the number of lenses, lowers the cost, has small distortion and reasonable tolerances.

Description

Technical Field

[0001] The present invention relates to the technical field of light projection, and particularly to a zoom objective lens system for micro projection. Background Art

[0002] The projection lens is the core component of a projection device. After the light passes through a reflective or transmissive light modulation device, it is then projected onto a projection screen through the projection lens to form an image.

[0003] With the development of technology, projection devices are applied in more and more fields, including home audio and video, projection advertising, industrial inspection, 3D printing, etc. Among them, the demand for installing projectors in hotels is also increasing. However, most current projectors have fixed-focus lenses and cannot meet different hotel application scenarios simultaneously. Taking a 100-inch projection frame as an example, the common projection distance range in hotels is between 2.7m and 3.3m, and a zoom lens with a throw ratio (TR) of 1.2 - 1.5 is correspondingly required. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, the purpose of the present invention is to provide a zoom objective lens system for micro projection. The present invention solves the problem that the fixed-focus lens in the prior art cannot meet the requirements of hotel projection.

[0005] To achieve the above purpose, the present invention provides the following solution:

[0006] A zoom objective lens system for micro projection, comprising:

[0007] A first group of lenses, a diaphragm, a second group of lenses, a galvanometer, a beam splitter, a protective glass, and an imaging surface arranged in sequence;

[0008] The imaging surface is used to emit light; the galvanometer is used for imaging pixels; the beam splitter is used to split the light; the diaphragm is used to control the light input amount of the split light; both the first group of lenses and the second group of lenses are used to correct aberrations;

[0009] The first group of lenses includes: a first lens, a second lens, and a third lens. Both the first lens and the second lens are lenses with negative optical power, and the third lens is a lens with positive optical power;

[0010] The second group of lenses includes: a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens; the fourth lens, the seventh lens, and the eighth lens are all lenses with positive optical power, and the fifth lens and the sixth lens form a doublet lens with negative optical power;

[0011] The first lens, the second lens, the third lens, and the fourth lens are all placed in front of the aperture, and the fifth lens, the sixth lens, the seventh lens, and the eighth lens are all placed behind the aperture.

[0012] Preferably, the material of the second lens is a plastic material.

[0013] Preferably, the first lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the galvanometer, the beam splitter device, and the protective glass are all made of glass.

[0014] Preferably, the ratio of the focal length of the first group of lenses to the focal length of the second group of lenses is -0.898; the ratio of the focal length of the first lens to the focal length of the first group of lenses is 1.238; the ratio of the focal length of the second lens to the focal length of the first group of lenses is 1.461; the ratio of the focal length of the third lens to the focal length of the first group of lenses is -2.623; the ratio of the focal length of the fourth lens to the focal length of the second group of lenses is 1.215; the ratio of the focal length of the doublet lens with negative optical power to the focal length of the second group of lenses is -1.198; the ratio of the focal length of the seventh lens to the focal length of the second group of lenses is 0.906; the ratio of the focal length of the eighth lens to the focal length of the second group of lenses is 1.866.

[0015] Preferably, the MTF value of each field of view of the zoom objective system is greater than 0.5.

[0016] Preferably, the pixel size of the image source of the zoom objective system is 5.4 um, and the corresponding design resolution is 93 line pairs per millimeter.

[0017] Preferably, the system distortion of the zoom objective system is within 0.25%, and the TV distortion amount is within 0.1%.

[0018] Preferably, the lens of the zoom objective system uses a 0.23-inch DMD chip.

[0019] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0020] The present invention provides a zoom objective system for micro-projection, including: a first group of lenses, an aperture, a second group of lenses, a galvanometer, a beam splitter device, a protective glass, and an imaging surface arranged in sequence. By setting the lens materials and quantities of the first group of lenses and the second group of lenses, the present invention improves the imaging quality, enhances the versatility of the objective system, reduces the number of lenses, lowers the cost, has small distortion, and reasonable tolerances. Description of the Drawings

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0022] Figure 1 Structural diagram of a zoom objective lens system for micro projection provided by an embodiment of the present invention;

[0023] Figure 2 Schematic diagram of the zoom objective lens system provided by an embodiment of the present invention, where Figure 2 (a) Schematic diagram of the objective lens system at the TR1.2 zoom position, Figure 2 (b) Schematic diagram of the objective lens system at the TR1.3 zoom position, Figure 2 (c) Schematic diagram of the objective lens system at the TR1.4 zoom position, Figure 2 (d) Schematic diagram of the objective lens system at the TR1.5 zoom position;

[0024] Figure 3 Spatial frequency MTF diagram at the zoom position provided by an embodiment of the present invention, where Figure 3 (a) Spatial frequency MTF diagram at the TR1.2 zoom position, Figure 3 (b) Spatial frequency MTF diagram at the TR1.3 zoom position, Figure 3 (c) Spatial frequency MTF diagram at the TR1.4 zoom position, Figure 3 (d) Spatial frequency MTF diagram at the TR1.5 zoom position;

[0025] Figure 4 Vertical chromatic aberration diagram provided by an embodiment of the present invention;

[0026] Figure 5 Field curvature evaluation diagram provided by an embodiment of the present invention;

[0027] Figure 6 Distortion evaluation diagram provided by an embodiment of the present invention.

[0028] Explanation of reference numerals:

[0029] 1 - First group of lenses, 2 - Second group of lenses, 3 - Diaphragm, 4 - Galvanometer, 5 - Beam splitter, 6 - Protective glass, 7 - Imaging plane, G1 - First lens, P2 - Second lens, G3 - Third lens, G4 - Fourth lens, G5 - Fifth lens, G6 - Sixth lens, G7 - Seventh lens, GM8 - Eighth lens. Detailed implementation manners

[0030] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0031] The object of the present invention is to provide a zoom objective lens system for microprojection. The present invention solves the problems of large limitations and small versatility of fixed-focus lenses in the prior art.

[0032] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0033] As Figure 1 shown, the present invention provides a zoom objective lens system for microprojection, including:

[0034] The first group lens 1, aperture 3, second group lens 2, galvanometer 4, beam splitter 5, protective glass 6, and imaging surface 7 arranged in sequence;

[0035] The imaging surface 7 is used to emit light; the galvanometer 4 is used for imaging pixels; the beam splitter 5 is used to split the light; the aperture 3 is used to control the light incident amount of the split light; both the first group lens 1 and the second group lens 2 are used to correct aberrations;

[0036] The first group lens 1 includes: the first lens G1, the second lens P2, and the third lens G3. Both the first lens G1 and the second lens P2 are lenses with negative optical power, and the third lens G3 is a lens with positive optical power; the first lens G1 is the first lens of the first group lens 1, the second lens P2 is the second lens of the first group lens 1, and the third lens G3 is the third lens of the first group lens 1.

[0037] The second group lens 2 includes: the fourth lens G4, the fifth lens G5, the sixth lens G6, the seventh lens G7, and the eighth lens GM8; the fourth lens G4, the seventh lens G7, and the eighth lens GM8 are all lenses with positive optical power, and the fifth lens G5 and the sixth lens G6 form a doublet lens with negative optical power; the fourth lens G4 is the first lens of the second group lens 2, the fifth lens G5 is the second lens of the second group lens 2, and so on.

[0038] The first lens G1, the second lens P2, the third lens G3, and the fourth lens G4 are all placed in front of the aperture 3, and the fifth lens G5, the sixth lens G6, the seventh lens G7, and the eighth lens GM8 are all placed behind the aperture 3. The first group of lenses 1 is located in front of the aperture 3. The first lens of the first group is a lens with negative focal power, the second lens is a lens with negative focal power, and the third lens is a lens with positive focal power. The front surface of the second lens P2, the rear surface of the second lens P2, the front surface of the GM8 lens, and the rear surface of the GM8 lens are all aspherical surfaces.

[0039] Specifically, the material of the second lens P2 is a plastic material.

[0040] Specifically, the first lens G1, the third lens G3, the fourth lens G4, the fifth lens G5, the sixth lens G6, the seventh lens G7, the eighth lens GM8, the galvanometer 4, the beam splitter 5, and the protective glass 6 are all made of glass.

[0041] Specifically, the ratio of the focal length of the first group of lenses 1 to the focal length of the second group of lenses 2 is -0.898; the ratio of the focal length of the first lens G1 to the focal length of the first group of lenses 1 is 1.238; the ratio of the focal length of the second lens P2 to the focal length of the first group of lenses 1 is 1.461; the ratio of the focal length of the third lens G3 to the focal length of the first group of lenses 1 is -2.623; the ratio of the focal length of the fourth lens G4 to the focal length of the second group of lenses 2 is 1.215; the ratio of the focal length of the doublet lens with negative focal power to the focal length of the second group of lenses 2 is -1.198; the ratio of the focal length of the seventh lens G7 to the focal length of the second group of lenses 2 is 0.906; the ratio of the focal length of the eighth lens GM8 to the focal length of the second group of lenses 2 is 1.866. Table 1 is the specific parameter table of the objective lens system, and Table 1 is shown as follows:

[0042] Table 1 Specific Parameter Table of the Objective Lens System

[0043]

[0044]

[0045] Table 2 is the zoom parameter table, and Table 3 is the coefficient table of each order of the aspherical lenses P2 and GM8. Among them, S0 is the projection distance, S6 is the zoom position, and S16 is the focusing position. Table 2 and Table 3 are shown as follows:

[0046] Table 2 Zoom Parameter Table

[0047]

[0048] Table 3 shows the coefficient tables of each order for the aspherical lens P2 and GM8.

[0049]

[0050] The projection lens obtained according to the specific parameters of each of the above lenses, where C is the curvature, K is the conic coefficient, and A4 to A16 are the high-order aspherical coefficients, such as Figure 2 the zoom objective lens system Figure 2 (a) is a schematic diagram of the zoom position system of the objective lens system TR1.2 Figure 2 (b) is a schematic diagram of the zoom position system of the objective lens system TR1.3 Figure 2 (c) is a schematic diagram of the zoom position system of the objective lens system TR1.4 Figure 2 (d) is a schematic diagram of the zoom position system of the objective lens system TR1.5.

[0051] Furthermore, the MTF value of each field of view of the zoom objective lens system is greater than 0.5.

[0052] Specifically, the MTF (English name: Modulation Transfer Function) index is currently the most accurate and scientific evaluation standard for lenses. The ordinate is the contrast, and the closer it is to 1, the better the lens imaging. The abscissa represents the resolution, with the unit of line pairs per millimeter. The pixel size of the image source adopted in the embodiments of the present application is 5.4um, and the corresponding design resolution is 93 line pairs per millimeter. Generally, the projection lens requires that the MTF value of each field of view reaches above 0.3 at the design resolution, and in the embodiments of the present application, the MTF value of each field of view at each zoom position is above 0.5, as Figure 3 shown, where Figure 3 (a) is the spatial frequency MTF diagram at the TR1.2 zoom position Figure 3 (b) is the spatial frequency MTF diagram at the TR1.3 zoom position Figure 3 (c) is the spatial frequency MTF diagram at the TR1.4 zoom position Figure 3 (d) is the spatial frequency MTF diagram at the TR1.5 zoom position.

[0053] Specifically, Figure 4 is the lateral chromatic aberration diagram of the lens. The ordinate is the image height field value size, and the abscissa is the numerical value size, with the unit of micrometers. In the figure, based on the main wavelength, the chromatic aberration values of each field of view between blue light, red light and green light (main wavelength) are respectively plotted. Generally, the projection lens requires that the chromatic aberration value is within the size of one image source pixel. In the embodiments of the present application, the axial chromatic aberration is controlled within 3.3um, which is less than 0.65 pixel sizes (pixel size 5.4um).

[0054] Furthermore, the pixel size of the image source of the zoom objective lens system is 5.4um, and the corresponding design resolution is 93 line pairs per millimeter.

[0055] Further, the system distortion of the zoom objective lens system is within 0.25%, and the TV distortion amount is within 0.1%. Figure 5 is the field curvature evaluation diagram, Figure 6 is the distortion evaluation diagram. The ordinate represents the field of view angle of the lens. The abscissa of the field curvature diagram represents the magnitude of the field curvature value, and the abscissa of the distortion diagram represents the distortion amount. Distortion is a very important index of the projection lens, generally required to be controlled within 3%, while the TV distortion is required to be controlled within 1%; the distortion shape of the embodiment of the present application can make the system TV distortion very small, the system distortion is within 0.25%, and the TV distortion amount is within 0.1%, and the TV distortion of the system is very excellent.

[0056] Specifically, the lens of the zoom objective lens system uses a 0.23-inch DMD chip, the focal length variation range is 6.36 mm to 7.76 mm, and the corresponding projection ratio (TR) is 1.2 to 1.5; the working F.NO of the lens is less than 1.7 within the zoom range; the fifth lens G5 and the sixth lens G6 of the lens are combined into a doublet lens, effectively eliminating the chromatic aberration of the system; the plastic aspheric lens is located at the position of the second lens P2, which can avoid problems such as easy scratching and easy aging caused by the plastic lens being on the outermost side.

[0057] In an embodiment, the optical lens satisfies the following conditional formula:

[0058] 1.6 < f / IH < 2(1)

[0059] wherein, f represents the effective focal length of the optical lens, and IH represents the actual semi-image height of the optical lens.

[0060] When the conditional formula (1) is satisfied, it is possible to achieve a change in the projection ratio (TR) in the range of 1.2 to 1.5 within the zoom range of the lens.

[0061] In an embodiment, the optical lens satisfies the following conditional formula:

[0062] 27 < TL*f / IH2 < 31(2)

[0063] wherein, TL represents the overall optical length of the optical lens, f represents the effective focal length of the optical lens, and IH represents the actual semi-image height of the optical lens.

[0064] When the conditional formula (2) is satisfied, the relationship between the overall length of the lens and the resolution ability can be reasonably balanced. When the value of TL*f / IH2 exceeds the upper limit, the overall length of the lens is too large, or in other words, if the overall length is shortened, the image height will be insufficient; when the value of TL*f / IH2 exceeds the lower limit, due to the excessive optical power of each lens, it is difficult to correct the lens aberration, and the resolution ability is significantly reduced.

[0065] In an embodiment, the optical lens satisfies the following conditional formula:

[0066] 3.88mm < f * tanθ < 3.92mm (3)

[0067] Wherein, f represents the effective focal length of the optical lens, and θ represents the half field of view angle of the optical lens.

[0068] When the conditional formula (3) is satisfied, the distortion of the optical lens can be reasonably limited, and the difficulty of distortion correction can be reduced. When the value of IH / tanθ exceeds the lower limit, the distortion of the lens will increase in the negative direction; when the value of IH / tanθ exceeds the upper limit, the distortion of the lens will increase in the positive direction.

[0069] In an embodiment, the optical lens satisfies the following conditional formula:

[0070] 0.4 < ET2 / CT2 < 2.5 (4)

[0071] 0.4 < ET8 / CT8 < 2.5 (5)

[0072] Wherein, CT1 represents the central thickness of the first lens G1, ET1 represents the edge thickness of the first lens G1, CT8 represents the central thickness of the eighth lens GM8, and ET8 represents the edge thickness of the eighth lens GM8.

[0073] When the conditional formulas (4) and (5) are satisfied, the shapes of the two aspherical lenses, namely the first lens G1 and the seventh lens G7, can be reasonably restricted, and the processing and forming difficulty of the lenses can be reduced;

[0074] In an embodiment, the optical lens satisfies the following conditional formula:

[0075] CRA < 2° (6)

[0076] Wherein, CRA represents the principal ray incident angle of the optical lens on the imaging surface 7.

[0077] When the conditional formula (6) is satisfied, the DMD chip can be well matched to achieve a good projection effect.

[0078] The beneficial effects of the present invention are as follows:

[0079] For the zoom projection lens disclosed by the present invention, the projection ratio (TR) can be adjusted between 1.2 and 1.5. Different frame sizes can be adjusted at one projection distance, or the same frame size can be adjusted at different projection distances, greatly enhancing the flexibility and applicability of projection.

[0080] For the zoom projection lens disclosed by the present invention, the total length is small, meeting the requirements of micro projection devices.

[0081] The short-focus projection lens disclosed by the present invention has a relative illuminance higher than 85% in the full field of view, and the MTF in the full field of view is higher than 0.5 within the zoom range, with excellent imaging quality; the distortion can reach within 0.3%, and the TV distortion is within 0.1%, and the distortion correction is very excellent.

[0082] For the zoom projection lens disclosed by the present invention, the lens adopts a combination of glass and plastic, effectively reducing the number of lenses. Only 8 lenses are used, effectively reducing the lens cost and assembly difficulty.

[0083] This zoom lens has only one zoom position, with a simple structure. The zoom system is easy to implement and can effectively reduce the cost of the zoom system. Considering and balancing manufacturing, cost, image quality, projection brightness, etc. comprehensively, it has a series of advantages such as variable zoom, high imaging quality, few lens elements, small distortion, reasonable tolerances, and low cost.

[0084] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. For the same or similar parts among the embodiments, reference can be made to each other.

[0085] Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, based on the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A zoom objective lens system for micro projection, characterized in that, The zoom objective lens system consists of: A first group of lenses, a diaphragm, a second group of lenses, a galvanometer scanner, a beam splitter, a protective glass, and an imaging surface arranged in sequence; The imaging surface is used to emit light; the galvanometer scanner is used for imaging pixels; the beam splitter is used to split the light; the diaphragm is used to control the amount of incident light of the split light; both the first group of lenses and the second group of lenses are used to correct aberrations; The first group of lenses consists of a first lens, a second lens, and a third lens. Both the first lens and the second lens are lenses with negative focal power, and the third lens is a lens with positive focal power; The second group of lenses consists of a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens; the fourth lens, the seventh lens, and the eighth lens are all lenses with positive focal power, and the fifth lens and the sixth lens form a cemented doublet lens with negative focal power; The first lens, the second lens, the third lens, and the fourth lens are all placed in front of the diaphragm, and the fifth lens, the sixth lens, the seventh lens, and the eighth lens are all placed behind the diaphragm; The ratio of the focal length of the first group of lenses to the focal length of the second group of lenses is -0.898; the ratio of the focal length of the first lens to the focal length of the first group of lenses is 1.238; the ratio of the focal length of the second lens to the focal length of the first group of lenses is 1.461; the ratio of the focal length of the third lens to the focal length of the first group of lenses is -2.623; the ratio of the focal length of the fourth lens to the focal length of the second group of lenses is 1.215; the ratio of the focal length of the cemented doublet lens with negative focal power to the focal length of the second group of lenses is -1.198; the ratio of the focal length of the seventh lens to the focal length of the second group of lenses is 0.906; the ratio of the focal length of the eighth lens to the focal length of the second group of lenses is 1.866; The MTF value of each field of view of the zoom objective lens system is greater than 0.

5.

2. The zoom objective lens system for micro projection according to claim 1, characterized in that, The material of the second lens is a plastic material.

3. The zoom objective lens system for micro projection according to claim 1, characterized in that, The first lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the galvanometer scanner, the beam splitter, and the protective glass are all made of glass.

4. A zoom objective lens system for microprojection according to claim 1, characterized in that, The pixel size of the image source of the zoom objective lens system is 5.4um, and the corresponding design resolution is 93 line pairs per millimeter.

5. A zoom objective lens system for microprojection according to claim 1, characterized in that, The system distortion of the zoom objective lens system is within 0.25%, and the TV distortion amount is within 0.1%.

6. The zoom objective lens system for micro projection according to claim 1, wherein The lens of the zoom objective lens system uses a 0.23-inch DMD chip.

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