Projection lens, focusing method and device of projection lens, and projector

Abstract

The invention discloses a projection lens, a focusing method and device for the projection lens, and a projector, and belongs to the field of projection. The projection lens comprises: a first lens group, a second lens group, a third lens group, a first lens barrel, a second lens barrel, and a third lens barrel; wherein the first lens barrel, the second lens barrel, and the third lens barrel are arranged in sequence along the light exit direction of the light valve of the projector where the projection lens is located, the first lens group is located in the first lens barrel, the second lens group is located in the second lens barrel, and the third lens group is located in the third lens barrel, and the first lens group, the second lens group, and the third lens group share a common optical axis; the second lens group comprises n lenses, 1≤n≤2, and the n lenses are all configured to be connected to a driving assembly in the projector where the lens is located, and move along the optical axis of the second lens group under the control of the driving assembly to change the image distance of the projection lens. The invention can simplify the focusing process of the projection lens. The invention is used for focusing of the projection lens.

Description

Technical Field

[0001] The present invention relates to the field of projection, and in particular to a projection lens, a focusing method and device of the projection lens, and a projector. Background Art

[0002] Laser display projection technology is a new type of display projection technology on the market. Laser projectors that currently use this technology can achieve the function of automatic focusing, and laser projectors that can achieve the automatic focusing function are also called automatic focusing projectors. Among them, focusing refers to adjusting the position of the projector's focal point to adjust the projector's image distance.

[0003] The focus projector includes a driving component and a projection lens, wherein the projection lens includes a focusing lens group for focusing. When the projection lens projects onto a screen and the distance between the projection lens and the screen changes, the driving component can control each focusing lens in the focusing lens group to move along the optical axis of the focusing lens group according to a pre-configured correspondence between the distance and the image distance.

[0004] However, the number of lenses in the focusing lens group of the current focus projector is relatively large, usually more than six, and a non-focusing lens is usually arranged between two focusing lenses of the focusing lens group. This results in a large number of lenses that need to be controlled by the driving component during the focusing process, and the movement of the focusing lenses arranged at intervals needs to be controlled, which makes the focusing process more complicated. Summary of the invention

[0005] The present invention provides a projection lens, a focusing method and device for the projection lens, and a projector, which can simplify the focusing process of the projection lens. The technical solution is as follows:

[0006] In a first aspect, a projection lens is provided, the projection lens comprising: a first lens group, a second lens group, a third lens group, a first lens barrel, a second lens barrel and a third lens barrel;

[0007] Wherein, the first lens barrel, the second lens barrel and the third lens barrel are arranged in sequence along the light emitting direction of the light valve of the projector where the projection lens is located, the first lens group is located in the first lens barrel, the second lens group is located in the second lens barrel, the third lens group is located in the third lens barrel, and the first lens group, the second lens group and the third lens group share a common optical axis;

[0008] The second lens group includes n lenses, 1≤n≤2, and the n lenses are configured to be connected to a driving component in the projector where they are located, and move along the optical axis of the second lens group under the control of the driving component to change the image distance of the projection lens.

[0009] In a second aspect, a focusing method of a projection lens is provided, which is applied to a driving component in a projector, wherein the projection lens is any projection lens described in the first aspect, and the driving component is connected to n lenses in the second lens group, and the method comprises:

[0010] The n lenses are controlled to move along the optical axis of the second lens group to change the image distance of the projection lens.

[0011] In a third aspect, a focusing device for a projection lens is provided, wherein the focusing device for a projection lens comprises modules for executing any one of the focusing methods for a projection lens described in the second aspect.

[0012] In a fourth aspect, a focusing device for a projection lens is provided, comprising: a processor; and a memory for storing executable instructions of the processor;

[0013] Wherein, when the processor runs the executable instructions, it can implement any focusing method of the projection lens described in the second aspect.

[0014] In a fifth aspect, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores instructions;

[0015] When the instruction is executed on the processing component, the processing component executes the focusing method of the projection lens described in any one of the second aspects.

[0016] In a sixth aspect, a projector is provided, the projector comprising: a drive assembly, a light valve, and any projection lens according to the first aspect;

[0017] The light valve, the first mirror group, the second mirror group and the third mirror group are arranged in sequence;

[0018] The driving assembly is connected to each lens in the second lens group and is configured to control each lens to move along the optical axis of the second lens group.

[0019] The technical solution provided by the present invention may include the following beneficial effects:

[0020] In the projection lens, the focusing method and device of the projection lens, and the projector provided by the present invention, the second lens group located in the second lens barrel of the projection lens includes at most two lenses, and each lens in the second lens group can be moved along the optical axis of the second lens group under the control of the driving component to change the image distance of the projection lens. This reduces the number of lenses that the driving component needs to control, and does not require the driving component to control the movement of the lenses arranged at intervals to change the image distance of the projection lens, thereby simplifying the focusing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0022] Figure 1 A schematic diagram of an application environment of a projector provided by an embodiment of the present invention;

[0023] Figure 2 A schematic diagram of the structure of a projection lens provided by an embodiment of the present invention;

[0024] Figure 3 A schematic diagram of an imaging contrast simulation interface of a projection lens provided by an embodiment of the present invention when the screen size is 100 inches;

[0025] Figure 4 An image comprehensive error diagram of a projection lens provided by an embodiment of the present invention on a sagittal light fan when the screen size is 100 inches;

[0026] Figure 5 An image comprehensive error diagram of a projection lens provided by an embodiment of the present invention on a sagittal light fan when the screen size is 100 inches;

[0027] Figure 6 An image comprehensive error diagram of a projection lens provided by an embodiment of the present invention on a sagittal light fan when the screen size is 100 inches;

[0028] Figure 7 An image comprehensive error diagram of a projection lens provided by an embodiment of the present invention on a sagittal light fan when the screen size is 100 inches;

[0029] Figure 8 An image comprehensive error diagram of a projection lens provided by an embodiment of the present invention on a sagittal light fan when the screen size is 100 inches;

[0030] Fig. 9 An image comprehensive error diagram of a projection lens provided by an embodiment of the present invention on a sagittal light fan when the screen size is 100 inches;

[0031] Fig.10 An image comprehensive error diagram of a projection lens provided by an embodiment of the present invention on a sagittal light fan when the screen size is 100 inches;

[0032] Fig.11 An image comprehensive error diagram of a projection lens provided by an embodiment of the present invention on a sagittal light fan when the screen size is 100 inches;

[0033] Fig.12 An image comprehensive error diagram of a projection lens provided by an embodiment of the present invention on a sagittal light fan when the screen size is 100 inches;

[0034] Fig.13 An image comprehensive error diagram of a projection lens provided by an embodiment of the present invention on a sagittal light fan when the screen size is 100 inches;

[0035] Fig.14 An image comprehensive error diagram of a projection lens provided by an embodiment of the present invention on a meridian light sector when the screen size is 100 inches;

[0036] Fig.15 An image comprehensive error diagram of a projection lens provided by an embodiment of the present invention on a meridian light sector when the screen size is 100 inches;

[0037] Fig.16 An image comprehensive error diagram of a projection lens provided by an embodiment of the present invention on a meridian light sector when the screen size is 100 inches;

[0038] Fig.17 An image comprehensive error diagram of a projection lens provided by an embodiment of the present invention on a meridian light sector when the screen size is 100 inches;

[0039] Fig.18 An image comprehensive error diagram of a projection lens provided by an embodiment of the present invention on a meridian light sector when the screen size is 100 inches;

[0040] Fig.19 An image comprehensive error diagram of a projection lens provided by an embodiment of the present invention on a meridian light sector when the screen size is 100 inches;

[0041] Fig. 20 An image comprehensive error diagram of a projection lens provided by an embodiment of the present invention on a meridian light sector when the screen size is 100 inches;

[0042] Fig.21 An image comprehensive error diagram of a projection lens provided by an embodiment of the present invention on a meridian light sector when the screen size is 100 inches;

[0043] Fig. 22 An image comprehensive error diagram of a projection lens provided by an embodiment of the present invention on a meridian light sector when the screen size is 100 inches;

[0044] Fig.23 An image comprehensive error diagram of a projection lens provided by an embodiment of the present invention on a meridian light sector when the screen size is 100 inches;

[0045] Fig.24A flowchart of a focusing method of a projection lens provided by an embodiment of the present invention;

[0046] Fig.25 A block diagram of a focusing device for a projection lens provided by an embodiment of the present invention;

[0047] Fig.26 A block diagram of another focusing device for a projection lens provided by an embodiment of the present invention;

[0048] Fig. 27 A schematic diagram of the direction of an image beam of a projector provided by an embodiment of the present invention when the screen size is 100 inches;

[0049] Fig.28 A schematic diagram of the principle of an imaging optical path of a projector provided in an embodiment of the present invention.

[0050] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] Figure 1 A schematic diagram of an application environment of a projector provided by an embodiment of the present invention, see Figure 1 The application environment includes a projector 1 and a screen 2. The projector 1 may include: a light valve 10, a total internal reflection (TIR) ​​prism 20, and a projection lens 30 arranged in sequence, wherein the projection lens 30 includes a refraction system S1 and a reflection system S2 arranged in sequence in a direction away from the TIR prism 20.

[0053] The light valve 10 is used to generate an image beam when illuminated. For example, the light valve 10 may be a digital micro mirror device (DMD), and the resolution of the DMD may be 2K resolution (meaning that the pixel value per row of the device reaches or approaches 2000), 3K resolution (meaning that the pixel value per row of the device reaches or approaches 3000), or 4K resolution (meaning that the pixel value per row of the device reaches or approaches 4096).

[0054] The TIR prism 20 is used to reflect the image beam to the refraction system S1 in the projection lens 30 to improve the brightness and contrast of the image beam entering the refraction system S1. For example, the TIR prism 20 can be two total reflection prisms, or 2a total reflection prisms, where a is an integer greater than 1.

[0055] The refraction system S1 is used to refract the image beam entering the refraction system S1 into the reflection system S2. At this time, the image beam is first imaged between the refraction system S1 and the reflection system S2 (ie, the image beam forms a convergence point between the refraction system S1 and the reflection system S2).

[0056] After the first imaging, the reflection system S2 is used to project the image beam output by the refraction system S1 onto the screen 2, so as to display a large-size projection picture on the screen 2. For example, the reflection system S2 can perform distortion aberration correction on the image beam refracted by the refraction system S1, and then project the image beam onto the screen, so as to display a distortion-free projection picture on the screen.

[0057] Alternatively, if Figure 1 As shown, the projector 1 may also include: an image shift lens group 40 disposed between the TIR prism 20 and the projection lens 30. The image shift lens group 40 is used to perform a shift process on the image beam reflected by the TIR prism 20, and then transmit the shifted image beam to the projection lens to improve the resolution of the image finally reflected on the projection screen. By way of example, the image shift lens group 40 may be a plate-shaped transparent device, such as a flat transparent glass. When the image shift lens group 40 is working, the image shift lens group 40 may be driven by a motor or other device to vibrate at a high frequency, thereby achieving the shift of the image beam. By superimposing the image beams corresponding to two consecutive projection images, the projection images are superimposed and the visual persistence effect of the human eye is utilized to enable the human eye to see a clear projection image, thereby improving the projection display resolution.

[0058] In the embodiment of the present invention, the projector 1 may be a projector capable of focusing (also called a focus projector), and accordingly, the projection lens 30 includes a focus lens group for focusing. Figure 1 As shown, the projector 1 may further include a driving assembly 50. When the projection lens 30 projects onto the screen and the distance between the projection lens 30 and the screen changes, the driving assembly 50 can control each focusing lens in the focusing lens group to move along the optical axis of the focusing lens group according to the correspondence between the pre-configured distance and the image distance.

[0059] However, in the related art, the number of lenses in the focusing lens group is relatively large, usually more than 6 lenses, and a non-focusing lens is usually arranged between two focusing lenses of the focusing lens group. This results in a large number of lenses that need to be controlled by the driving component during the focusing process, and the movement of the focusing lenses arranged at intervals needs to be controlled, which makes the focusing process more complicated.

[0060] Figure 2 A schematic diagram of a projection lens according to an embodiment of the present invention. The projection lens can be applied to Figure 1 Projector 1 shown. See Figure 2 The projection lens 30 includes: a first lens group 301, a second lens group 302, a third lens group 303, a first lens barrel 3051, a second lens barrel 3052 and a third lens barrel 3053. The first lens barrel 3051, the second lens barrel 3052 and the third lens barrel 3053 are arranged in sequence along the light emitting direction X of the light valve of the projector where the projection lens is located. The first lens group 301 is located in the first lens barrel 3051, the second lens group 302 is located in the second lens barrel 3052, and the third lens group 303 is located in the third lens barrel 3053. The lenses in each lens group can only move in the lens barrel where it is located. The first lens group 301, the second lens group 302 and the third lens group 303 share an optical axis L. The second lens group 302 includes n lenses, 1≤n≤2, Figure 2 The second lens group 302 includes two lenses as an example for description. The n lenses are all configured to be connected to a driving component in the projector where they are located, and move along the optical axis L of the second lens group 302 under the control of the driving component to change the image distance of the projection lens 30. The image distance of the projection lens refers to the distance from the main plane of the projection lens to the screen projected by the projection lens.

[0061] In summary, in the projection lens provided by the embodiment of the present invention, the second lens group located in the second lens barrel includes at most two lenses, and each lens in the second lens group can be moved along the optical axis of the second lens group under the control of the driving component to change the image distance of the projection lens. This reduces the number of lenses that the driving component needs to control, and does not require the driving component to control the movement of the lenses that are spaced apart to change the image distance of the projection lens, thereby simplifying the focusing process.

[0062] It should be noted that: the embodiment of the present invention is described by taking the projection lens including the first lens group, the second lens group and the third lens group as an example. In practice, the projection lens may also include other structures, which is not limited in the embodiment of the present invention.

[0063] Optionally, the second lens group 302 may include two lenses (n=2). Figure 2As shown, the second lens group 302 may include a first spherical lens 3021 with positive optical focal length, and a second spherical lens 3022 with negative optical focal length, which are arranged in sequence along the light output direction of the light valve of the projector where the projection lens is located, wherein the first spherical lens 3021 is close to the first lens group 301, and the second spherical lens 3023 is close to the third lens group 303.

[0064] Generally, when the size of the image projected by the projection lens is adjustable, the vertical distance between the point where the image beam of the projection lens is emitted and the screen (also called the projection distance) also changes, and accordingly, the image projected by the projection lens will also be unclear. In order to make the projection images of various sizes clear, the projection lens needs to be focused. In the embodiment of the present invention, when the projection lens is focused, the first lens group 301 and the third lens group 303 remain stationary, and each lens in the second lens group 302 moves along the optical axis L of the second lens group 302 under the control of the driving assembly to change the image distance of the projection lens 30.

[0065] For example, taking the size of the picture projected by the projection lens as 100 inches as a reference, when the projection distance increases so that the size of the picture becomes smaller relative to 100 inches, during the focusing process, the first spherical lens 3021 and the second spherical lens 3022 move along the optical axis L of the second lens group 302 in a direction away from the first lens group 301. When the projection distance decreases so that the size of the picture becomes larger relative to 100 inches, during the focusing process, the first spherical lens 3021 and the second spherical lens 3022 move along the optical axis L of the second lens group 302 in a direction close to the first lens group 301. The moving distances of the first spherical lens 3021 and the second spherical lens 3022 may be different.

[0066] Optionally, the first lens group 301 may include m lenses, where m is a positive integer, and 6≤m<16. For example, the first lens group 301 may include 6 lenses, or 7 lenses, or 11 lenses.

[0067] When the first lens group 301 includes 11 lenses, the first lens group 301 may include 2 aspherical lenses and 9 spherical lenses. Figure 2As shown, the first lens group 301 includes: a third spherical lens 3011 with positive focal power, a fourth aspherical lens 3012 with positive focal power, a three-cemented spherical lens 3013 with positive focal power (composed of three spherical lenses bonded by glue), a fifth spherical lens 3014 with negative focal power, a sixth spherical lens 3015 with positive focal power, a seventh spherical lens 3016 with negative focal power, an eighth aspherical lens 3017 with positive focal power, and a double-cemented spherical lens 3018 with negative focal power (composed of two spherical lenses bonded by glue), which are arranged in sequence. The third spherical lens 3011 is far away from the second lens group 302, and the double-cemented spherical lens 3018 is close to the second lens group 302.

[0068] Figure 2 The first lens group 301 includes 11 lenses, and when the first lens group 301 includes 6 lenses, the first lens group 301 may include 1 aspherical lens and 5 spherical lenses. For example, the first lens group 301 may include: a three-cemented spherical lens with positive focal length, a third aspherical lens with positive focal length, and a double-cemented spherical lens with negative focal length, arranged in sequence, wherein the three-cemented spherical lens is far away from the second lens group 302, and the double-cemented spherical lens is close to the second lens group 302.

[0069] When the first lens group 301 includes 7 lenses, the first lens group 301 may include 2 aspherical lenses and 5 spherical lenses. For example, the first lens group 301 may include: a third aspherical lens with positive focal length, a three-cemented spherical lens with positive focal length, a fourth aspherical lens with positive focal length, and a double-cemented spherical lens with negative focal length, which are arranged in sequence, wherein the third aspherical lens is far away from the second lens group 302, and the double-cemented spherical lens is close to the second lens group 302.

[0070] like Figure 2 As shown, the above-mentioned three-cemented spherical lens 3013 may include: a ninth spherical lens a1 with positive focal power, a tenth spherical lens a3 with negative focal power, and an eleventh spherical lens a4 with positive focal power, which are sequentially arranged in a direction close to the second lens group 302. The double-cemented spherical lens 3018 may include: a twelfth spherical lens a4 with negative focal power, and a thirteenth spherical lens a5 with positive focal power, which are sequentially arranged in a direction close to the second lens group 302.

[0071] The triplet spherical lens 3013 and the doublet spherical lens 3018 are mainly used to correct the chromatic aberration (including axial chromatic aberration and lateral chromatic aberration) of the projection lens, and at the same time have a certain ability to correct the monochromatic aberration (such as spherical aberration, coma, astigmatism, field curvature or distortion) of the projection lens. Among them, the image light beam sequentially passes through the triplet spherical lens 3013 and the doublet spherical lens 3018. After the triplet spherical lens 3013 corrects the chromatic aberration of the projection lens, the doublet spherical lens 3018 further precisely corrects the remaining chromatic aberration of the projection lens. Among them, the focal power of the twelfth spherical lens a4 included in the doublet spherical lens 3018 is negative, and the focal power of the thirteenth spherical lens a5 is positive, so that the positive chromatic aberration generated by the image light beam passing through the twelfth spherical lens a4 and the negative chromatic aberration generated by passing through the thirteenth spherical lens a5 cancel each other out, thereby correcting the chromatic aberration of the image light beam to 0. It should be noted that the positions of the triplet spherical lens 3013 and the doublet spherical lens 3018 in the projection lens can be interchanged, and the embodiments of the present invention do not limit this.

[0072] Optionally, the third lens group 303 may include n lenses, where n is a positive integer and 2 < n < 5. For example, the third lens group 303 may include 3 lenses. In this case, the third lens group 303 may include 1 aspherical lens and 2 spherical lenses. For example, as Figure 2 shown, the third lens group 303 may include: the fourteenth spherical lens 3031 with positive focal power, the fifteenth spherical lens 3032 with negative focal power, and the sixteenth aspherical lens 3033 with negative focal power arranged in sequence. Among them, the fourteenth spherical lens 3031 is close to the second lens group 302, and the sixteenth aspherical lens 3033 is far from the second lens group 302.

[0073] Generally, the lenses of the projection lens can usually be made of glass materials. However, the price of glass materials is relatively high, and when making aspherical lenses with glass materials, the processing technology is relatively complex. Since the sixteenth aspherical lens 3033 is far from the light valve and has a large aperture, it is more consumable. Therefore, the material of the sixteenth aspherical lens 3033 can be plastic, such as 480R (a type of plastic). The price of plastic materials is relatively low, and when making aspherical lenses with plastic materials, the processing technology is relatively simple. For example, an aspherical lens can be made of plastic materials by means of molding.

[0074] The projection lens provided by the embodiment of the present invention includes a total of three aspheric lenses, which are respectively: a fourth aspheric lens 3012, an eighth aspheric lens 3017, and a sixteenth aspheric lens 3033. Since the regular shapes of symmetrical aspheric lenses are easy to process and manufacture, especially rotationally symmetrical aspheric lenses, they are easier to process and manufacture. Therefore, when the three aspheric lenses in the projection lens are all rotationally symmetrical structures, the processing process of the projection lens can be simplified and the processing cost can be reduced.

[0075] The three aspherical lenses are mainly used to correct the aberration of the projection lens. For example, the fourth aspherical lens 3012 can be used to correct the coma, astigmatism and field curvature of the projection lens. The eighth aspherical lens 3017 can be used to correct the spherical aberration and field curvature of the projection lens. The sixteenth aspherical lens 3033 can be used to correct the astigmatism, field curvature and distortion of the projection lens. Among them, distortion will affect the shape of the picture projected by the projection lens, and coma, astigmatism, field curvature and spherical aberration will affect the clarity of the picture projected by the projection lens. The three aspherical lenses can correct coma, astigmatism, field curvature, spherical aberration and distortion, thereby improving the display effect of the picture projected by the projection lens.

[0076] Optionally, the projection lens may further include: an aperture stop ( Figure 2 (not shown in the figure), the aperture stop is located between any two lenses in the first lens group 301. For example, the aperture stop is located between the fifth spherical lens 3014 and the sixth spherical lens 3015 in the first lens group. The aperture stop is used to limit the incident transmission pupil diameter to control the correction of the aberration of the projection lens by other structures in the projection lens.

[0077] It should be noted that, since the aperture stop is mainly used to limit the incident transmission pupil diameter, the energy density distribution around it is relatively high, and the temperature near the aperture stop is relatively high. Therefore, in order to reduce the influence of the temperature near the aperture stop on the lens, the lens near the aperture stop (such as the fifth spherical lens 3014 and the sixth spherical lens 3015) needs to be made of a material with a relatively small expansion coefficient. For example, the lens can be made of glass materials with models L-TIM28, L-AM69HE and L-LALB. The material with a relatively small expansion coefficient can reduce the change in the lens surface shape (i.e., R value, i.e., the radius of curvature of the lens) caused by the temperature change of the lens material, thereby reducing the influence of temperature drift on the projection lens.

[0078] It should be noted that the projection lens provided in the embodiment of the present invention comprises a refractive system and a reflective system arranged in sequence, and the refractive system comprises the first lens group 301, the second lens group 302 and the third lens group 303. Figure 2As shown, the reflection system includes an aspheric reflector 304 with positive optical power. The aspheric reflector 304 is adjacent to the third mirror group 303 and is used to reflect the image light beam refracted by the third mirror group 303 onto the screen for display by the screen.

[0079] In a projection lens, the focal length of each lens will directly affect astigmatism, field curvature, distortion, axial chromatic aberration and vertical chromatic aberration, so different combinations of positive and negative focal lengths will play a certain role in aberration correction. In the projection lens provided by an embodiment of the present invention, when the first lens group 301 includes 11 lenses, the focal lengths of the first lens group 301 are respectively positive, positive, positive, negative, positive, negative, positive, negative, positive, negative, positive; when the second lens group 303 includes two lenses, the focal lengths of the second lens group 302 are respectively positive and negative; when the third lens group 303 includes three lenses, the focal lengths of the third lens group 303 are respectively positive, negative, negative. Among them, the total focal length of the refractive system is positive, and the total focal length of the reflective system is also positive. This ensures that the lens of the projection lens achieves the best effect in aberration correction.

[0080] Optionally, the projection lens provided in the embodiment of the present invention can meet at least one of the following conditions: Condition 1: The ratio of the effective focal length of the first lens group 301 to the effective focal length of the projection lens is a, 2≤a≤12. Condition 2: The ratio of the effective focal length of the second lens group to the effective focal length of the projection lens is b, 20≤b≤35. Condition 3: The ratio of the effective focal length of the third lens group to the effective focal length of the projection lens is c, 25≤c≤35. The effective focal length of the projection lens is the distance from the rear main image plane to the paraxial image plane of the projection lens. The effective focal length of each lens group is: the distance from the rear main image plane to the paraxial image plane of the lens group. When the projection lens meets at least one of the conditions, the display effect of the picture projected by the projection lens on the screen is better.

[0081] Optionally, the effective focal length of the projection lens can be d, and 2.34 millimeters (mm) ≤ d ≤ 2.370 millimeters. For example, the effective focal length of the projection lens can be 2.34 mm, and the projection lens is an ultra-short-throw projection lens. Alternatively, the size of the screen projected by the projection lens can be 90 inches to 120 inches, and accordingly, the projection ratio of the projection lens can be e, and 0.23 ≤ e ≤ 0.24. For example, the projection ratio of the projection lens can be 0.24. The projection ratio of the projection lens is the ratio of the projection distance to the width of the projected screen, that is, the projection distance / screen width. The projection ratio reflects the ultra-short-throw characteristics of the lens. Compared with traditional non-ultra-short-throw projectors, the ultra-short-throw projection lens has a smaller projection ratio (less than 1), so the projection lens can be placed very close to the projection screen, saving a lot of space and avoiding the obstruction of the image beam when it is necessary to be close to the projection screen.

[0082] It should be noted that in the related art, due to the large number of focusing lenses for focusing and the possible presence of non-focusing lenses between two focusing lenses, multiple focusing lenses are usually located at different positions in the projection lens. This results in a large aberration that needs to be corrected by the focusing lenses, thus easily affecting the projection effect of the projection lens during the focusing process. In the embodiments of the present invention, the maximum number of focusing lenses for focusing is 2, and all the focusing lenses are arranged in the middle position of the projection lens (i.e., arranged in the second lens barrel). Since the image beam first passes through the first lens group 301 and then through the second lens group 302, most of the aberration of the projection lens is corrected by the first lens group 301. This makes the aberration that needs to be corrected by the second lens group 302 smaller, and further makes the influence on the imaging effect of the projection lens smaller during the focusing process of the projection lens. It can achieve 4K high-resolution imaging under a 90-inch to 120-inch screen only by moving two lenses.

[0083] The resolution of the projection lens provided by the embodiments of the present invention can usually be 93 line pairs per millimeter (lp / mm) (i.e., the resolution required for 4K), so the projection lens can resolve images with 4K resolution, enabling the projection screen to present a clearer image and improving the user experience. The total length of the refraction system of the projection lens is L1 (i.e., the distance from the edge surface of the third spherical lens 3011 close to the light valve to the edge surface of the sixteenth aspherical lens 3033 close to the reflection system), and the distance between the refraction system and the reflection system is L2, where 1.37 < L1 / L2 < 1.57. Since the thickness of the lenses in the reflection system can be ignored, L2 can be the value obtained by subtracting L1 from the total length of the projection lens. Figure 2 Since the number of lenses used for focusing is reduced, the number of lenses used in the projection lens provided by the embodiments of the present invention is 16, making the length range of the projection lens between 177 mm and 185 mm. For example, the length of the projection lens can be 177 mm. In the related art, the number of lenses in a focusable projection lens is about 20, and its length is at least 210 mm. It can be seen that the maximum projection length of the focusable projection lens provided by the embodiments of the present invention is also smaller than that of the focusable projection lens in the related art. And the maximum aperture of the lenses in this projection lens is 50 mm, while the maximum aperture of the lenses in the projection lens in the related art is 60 mm, so its maximum aperture is also smaller than that of the projection lens in the related art. Therefore, the overall volume of the focusable projection lens provided by the embodiments of the present invention is smaller.

[0084] Please refer to

[0085] Please refer to Figure 3 , Figure 3This is a schematic diagram of an imaging contrast simulation interface of a projection lens provided by an embodiment of the present invention when the screen size is 100 inches, and is also a distortion analysis diagram of the projector. Figure 3 , the intersection of the horizontal and vertical lines is the pre-imaging position, and the cross (×) is the imaging position of the actual projection lens. The higher the overlap rate between the intersection and the cross, the lower the distortion value of the imaging, and the lower the degree of distortion of the imaging. Assuming that the wavelength of the image beam is 0.5500 microns (μm) and the zoom ratio is 1, Figure 3 As shown, when the projection screen is 100 inches (2214×1245mm 2 ), the maximum distortion value simulated in this simulation interface is -1.032%. Figure 3 It can be seen that the distortion degree of the imaging of the projection lens is relatively low. It should be noted that the embodiment of the present invention only shows the schematic diagram of the imaging contrast simulation interface of the projection lens when the screen size is 100 inches. The schematic diagram of the imaging contrast simulation interface of the projection lens when the screen size is 90 inches and the schematic diagram of the imaging contrast simulation interface when the screen size is 120 inches can both be referred to. Figure 3 , the embodiments of the present invention are not described in detail here.

[0086] Please refer to Figures 4 to 23 , Figures 4 to 13 The image comprehensive error diagram of the normalized sagittal light fan of a projection lens provided by an embodiment of the present invention when the screen size is 100 inches under 10 different fields of view, Figures 14 to 23 The following is a graph of the image comprehensive error on the normalized meridian light fan of a projection lens provided by an embodiment of the present invention when the screen size is 100 inches under 10 different fields of view. Figures 4 to 13 Each picture is used to show the difference between the three wavelengths of light and the main wavelength light (that is, the light passing through the light-emitting point and the center point of the aperture) on the image plane under a field of view when the projection screen is 100 inches. The wavelengths of the three light are 0.45μm, 0.55μm and 0.62μm respectively.

[0087] like Figures 4 to 13 As shown, the sagittal light fan is a beam profile passing through the X-axis of the pupil. In the coordinate system of the image comprehensive error diagram on the sagittal light fan, the horizontal axis PX is used to represent the normalized height of the light on the sagittal light fan entering the pupil, and the range of the normalized height is -1 to 1. The vertical axis EX is used to represent the difference between the height of the light on the image plane and the height of the main light of the current field of view on the image plane when the light passing through the specified pupil in the sagittal light fan is incident on the image plane, and the unit of the height difference is μm. In each figure, in the coordinate axis plane where EX and PX are located, the higher the overlap rate of multiple curves, the smaller the chromatic aberration of the projection lens. When the curve is closer to the PX axis, the smaller the aberration of the projection lens.

[0088] like Figures 14 to 23 As shown, the meridional light fan is a beam profile passing through the Y axis of the pupil. In the coordinate system of the image comprehensive error diagram on the meridional light fan, the horizontal axis PY is used to represent the normalized height of the light on the meridional light fan entering the pupil, and the range of the normalized height is -1 to 1. The vertical axis EY is used to represent the difference between the height of the light passing through the specified pupil in the meridional light fan and the height of the main light of the field of view on the image plane, and the unit of the height difference is μm. In each figure, in the coordinate axis plane where EY and PY are located, the higher the overlap rate of multiple curves, the smaller the chromatic aberration of the projection lens. When the curve is closer to the PY axis, the smaller the aberration of the projection lens.

[0089] It should be noted that the embodiment of the present invention only shows the image comprehensive error diagram of the normalized sagittal light fan of the projection lens under 10 different fields of view when the screen size is 100 inches, and the image comprehensive error diagram of the normalized meridional light fan of the projection lens under 10 different fields of view when the screen size is 100 inches. The image comprehensive error diagram of the sagittal light fan of the projection lens when the screen size is 90 inches, and the image comprehensive error diagram of the sagittal light fan of the projection lens when the screen size is 120 inches are similar to Figures 4 to 13 is similar, so you can refer to Figures 4 to 13 The image comprehensive error diagram of the projection lens on the meridian light sector when the screen size is 90 inches, and the image comprehensive error diagram of the projection lens on the meridian light sector when the screen size is 120 inches are both the same as Figures 14 to 23 is similar, so you can refer to Figures 14 to 23 The embodiments of the present invention are not described in detail here. Figures 4 to 23 It can be seen that when the projection screen is 100 inches, the overlap rate of multiple curves in the image comprehensive error diagram on the sagittal light fan and the image comprehensive error diagram on the meridional light fan under each field of view is relatively high, and they are all close to the PY axis or PX axis. Therefore, the chromatic aberration and aberration of the projection lens are relatively small. Similarly, when the projection screen is 90 inches or 120 inches, the chromatic aberration and aberration of the projection lens are also relatively small.

[0090] In summary, in the projection lens provided by the embodiment of the present invention, the second lens group located in the second lens barrel includes at most two lenses, and each lens in the second lens group can be moved along the optical axis of the second lens group under the control of the driving component to change the image distance of the projection lens. This reduces the number of lenses that the driving component needs to control, and does not require the driving component to control the movement of the lenses arranged at intervals to change the image distance of the projection lens, thereby simplifying the focusing process.

[0091] Furthermore, the refractive system of the projection lens provided by the embodiment of the present invention includes a triplet lens and a doublet lens, and the triplet lens and the doublet lens cooperate with other lenses to enable the projection lens to have high chromatic aberration and aberration correction capabilities at the same time, which can greatly reduce the number of conventional lenses and lens combinations used, so that the projection lens has a high resolution while the number of lenses of the projection lens as a whole is reduced accordingly, effectively shortening the length of the projection lens, which is conducive to realizing a miniaturized projection lens. In addition, for aspheric lenses, plastic materials are easier to process and have a lower price, so the material of the twelfth aspheric lens can be plastic, thereby reducing the processing cost of the projection lens and reducing the processing difficulty of the projection lens.

[0092] The embodiment of the present invention provides a focusing method for a projection lens, which can be applied to a driving component in a projector. The projection lens can be any projection lens provided in the embodiment of the present invention, and the driving component is connected to n lenses in the second lens group of the projection lens. Fig.24 , the method comprising:

[0093] Step 201: Control n lenses to move along the optical axis of the second lens group to change the image distance of the projection lens.

[0094] Please refer to Figure 2 , the second lens group 302 may include a first spherical lens 3021 and a second spherical lens 3022 arranged in sequence along the light emitting direction of the light valve. Optionally, a distance sensor may be provided at one end of the projector where the projection lens is located and close to the screen, and the distance sensor is used to detect the distance between the projection lens and the screen. Before controlling the n lenses to move along the optical axis of the second lens group, the driving component may first determine the distance change between the projection lens and the screen through the distance sensor, and then control the n lenses to move along the optical axis of the second lens group according to the distance change between the projection lens and the screen. Optionally, the distance sensor may also be provided at other positions of the projection lens, which is not limited in the embodiment of the present invention.

[0095] For example, please refer to Figure 2 When the driving component determines through the distance sensor that the distance between the projection lens and the screen becomes larger, the driving component can control the first spherical lens and the second spherical lens to move along the optical axis of the second lens group in a direction away from the first lens group. When the driving component determines through the distance sensor that the distance between the projection lens and the screen becomes smaller, the driving component can control the first spherical lens and the second spherical lens to move along the optical axis of the second lens group in a direction close to the first lens group.

[0096] In summary, in the focusing method of the projection lens provided by the embodiment of the present invention, the driving component can control all the lenses in the second lens group to move along the optical axis of the second lens group to change the image distance of the projection lens. Since the second lens group located in the second lens barrel includes at most two lenses, the number of lenses that the driving component needs to control is small, and the driving component does not need to control the movement of the lenses arranged at intervals to change the image distance of the projection lens, thereby simplifying the focusing process.

[0097] The above describes the focusing method of the projection lens of the embodiment of the present invention. The following describes the focusing device of the projection lens of the embodiment of the present invention. The focusing device of the projection lens of the embodiment of the present invention can be applied to a driving component. The driving component can be Figure 1 The driving assembly 10 is shown. It should be understood that the focusing device of the projection lens applied to the driving assembly can be the driving assembly in the above method, which has any function of the driving assembly in the above method.

[0098] Fig.25 FIG. 1 is a block diagram of a focusing device for a projection lens provided in an embodiment of the present invention. The focusing device 300 for a projection lens can be applied to Figure 1 The drive assembly in the projector 1 shown. Fig.25 , the device 300 comprises:

[0099] The control module 301 is used to control the n lenses to move along the optical axis of the second lens group to change the image distance of the projection lens.

[0100] Optionally, the control module 301 may include a control submodule and a physical structure (such as a motor), wherein the physical structure is connected to the n lenses, and the physical structure can move under the control of the control submodule to drive the n lenses to move along the optical axis of the second lens group.

[0101] Optionally, the second lens group includes a first spherical lens and a second spherical lens sequentially arranged along the light emitting direction of the light valve, and the control module 301 is used to:

[0102] When the projection lens projects onto the screen and the distance between the projection lens and the screen increases, the first spherical lens and the second spherical lens are controlled to move along the optical axis of the second lens group in a direction away from the first lens group.

[0103] When the projection lens projects onto the screen and the distance between the projection lens and the screen becomes smaller, the first spherical lens and the second spherical lens are controlled to move along the optical axis of the second lens group toward the direction close to the first lens group.

[0104] In summary, in the focusing device of the projection lens provided by the embodiment of the present invention, the control module can control all the lenses in the second lens group to move along the optical axis of the second lens group to change the image distance of the projection lens. Since the second lens group located in the second lens barrel includes at most three lenses, the number of lenses that the control module needs to control is small, and the control module does not need to control the movement of the lenses arranged at intervals to change the image distance of the projection lens, thereby simplifying the focusing process.

[0105] Fig.26 A block diagram of a focusing device for a projection lens provided in an embodiment of the present invention, see Fig.26 The focusing device 400 of the projection lens includes: a processor 401 and a memory 402 for storing executable instructions of the processor 401. When the processor runs the executable instructions, the focusing method of the projection lens provided in the embodiment of the present invention can be implemented.

[0106] The embodiment of the present invention further provides a computer-readable storage medium, in which instructions are stored. When the instructions are executed on a processing component, the processing component executes the focusing method of the projection lens provided by the embodiment of the present invention.

[0107] The embodiment of the present invention provides a projector, which can refer to Figure 1 The projector 1 shown, such as Figure 1 As shown, the projector 1 includes: a light valve 10, a TIR prism 20, a projection lens 30, an image shift lens group 40 and a driving component 50. The projection lens 30 can be any projection lens provided in the embodiments of the present invention. Among them, the projection lens 30 includes a first lens group 301, a second lens group 302 and a third lens group 303. The light valve 10, the TIR prism 20, the first lens group 301, the second lens group 302 and the third lens group 303 are arranged in sequence. The driving component 50 is connected to each lens in the second lens group 302 and is configured to control each lens to move along the optical axis of the second lens group 302. The specific structure of the projector 1 and the function of each structure can refer to the aforementioned Figure 1 The description of the projector 1 shown in the figure will not be repeated in detail in the embodiment of the present invention.

[0108] In the projector 1 provided by the embodiment of the present invention, the total length of the refraction system is L1, the distance between the refraction system and the reflection system is L2, and the distance from the light valve 10 to the first spherical lens of the first lens group 301 is the back working distance of the projection lens 30. Since the back working distance is approximately equal to the back focal length (BFL), the back working distance is usually also referred to as BFL. Among them, 0.3 < BFL / L2 < 0.55, and 0.05 < BFL / (L1 + L2) < 0.25, which can meet the ultra-short focal length characteristics of the projection lens. Optionally, in this projector, the offset of the light valve pixel plane relative to the optical axis satisfies the relational expression: 132% < offset < 150%, and the light valve pixel plane refers to the plane where the light valve reflects the image light beam.

[0109] In addition, in the projector provided by the embodiment of the present invention, in order to cooperate with the miniaturization of the projection lens, a small-sized model is correspondingly adopted for the light valve, so that the light aperture of the light emitted from the light valve is reduced, and the light aperture of the projection lens lens can also be reduced, which is beneficial to the miniaturization of the volume of the projection lens.

[0110] Fig. 27 It is a schematic diagram of the image light beam direction of a projector provided by the embodiment of the present invention when the screen size is 100 inches. Refer to Fig. 27 , when the light valve 10 is illuminated, the light valve 10 outputs an image light beam, and the image light beam is reflected to the image offset lens group 40 after passing through the TIR prism 20. Then, it is transmitted to the refraction system S1 of the projection lens 30 through the image offset lens group 40. After passing through the refraction system S1, the image light beam converges to a certain extent and forms the first image. After the first imaging, the image light beam enters the reflection system S2 of the projection lens 30, and the reflection system S2 reflects the image light beam and forms the second image on the screen to display a large-sized image on the screen.

[0111] Fig.28 It is a schematic diagram of the principle of the imaging optical path of a projector provided by the embodiment of the present invention. Refer to Fig.28 , after the image light beam is emitted from the projector 1, it is reflected to the screen 2, and a large-sized image is displayed on the screen 2.

[0112] In summary, in the projector provided by the embodiment of the present invention, the second lens group located in the second lens barrel includes at most three lenses, and the driving component can control each lens in the second lens group to move along the optical axis of the second lens group to change the image distance of the projection lens. This makes the number of lenses that the driving component needs to control less, and makes the driving component not need to control the movement of the lenses arranged at intervals to change the image distance of the projection lens, thereby simplifying the focusing process.

[0113] In the present application, the terms “first”, “second”, “third”, “fourth”, etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance.

[0114] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the present invention are indicated by the claims.

[0115] It should be understood that the present invention is not limited to the exact construction that has been described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A projection lens, characterized in that: The number of lens groups in the projection lens is 3, and the projection lens comprises: a first lens group, a second lens group, a third lens group, a first lens barrel, a second lens barrel and a third lens barrel; Wherein, the first lens barrel, the second lens barrel and the third lens barrel are arranged in sequence along the light emitting direction of the light valve of the projector where the projection lens is located, the first lens group is located in the first lens barrel, the second lens group is located in the second lens barrel, the third lens group is located in the third lens barrel, and the first lens group, the second lens group and the third lens group share a common optical axis; The second lens group includes n lenses, 1≤n≤2, and the n lenses are configured to be connected to a driving component in the projector where they are located, and move along the optical axis of the second lens group under the control of the driving component to change the image distance of the projection lens; The first lens group is composed of a three-cemented spherical lens with positive focal power, a third aspherical lens with positive focal power, and a two-cemented spherical lens with negative focal power, which are arranged in sequence, the three-cemented spherical lens is far away from the second lens group, and the two-cemented spherical lens is close to the second lens group; The second lens group is composed of a first spherical lens with positive focal length and a second spherical lens with negative focal length, which are arranged in sequence along the light emitting direction of the light valve, the first spherical lens is close to the first lens group, and the second spherical lens is close to the third lens group; The third lens group is composed of a fourteenth spherical lens with positive focal length, a fifteenth spherical lens with negative focal length, and a sixteenth aspherical lens with negative focal length, which are arranged in sequence. The fourteenth spherical lens is close to the second lens group, the sixteenth aspherical lens is far away from the second lens group, and the material of the sixteenth aspherical lens is plastic. The ratio of the effective focal length of the first lens group to the effective focal length of the projection lens is a, 2≤a≤12; the ratio of the effective focal length of the second lens group to the effective focal length of the projection lens is b, 20≤b≤35; the ratio of the effective focal length of the third lens group to the effective focal length of the projection lens is c, 25≤c≤35; the effective focal length of the projection lens is d, 2.34 mm≤d≤2.370 mm; The projection ratio of the projection lens is e, 0.23≤e≤0.

24.

2. The projection lens according to claim 1, characterized in that: n＝2。 3. A focusing method for a projection lens, characterized in that: A driving assembly applied to a projector, wherein the projection lens is the projection lens according to any one of claims 1 to 2, the driving assembly is connected to n lenses in the second lens group, and the method comprises: The n lenses are controlled to move along the optical axis of the second lens group to change the image distance of the projection lens.

4. The method according to claim 3, characterized in that The second lens group includes a first spherical lens and a second spherical lens sequentially arranged along the light emitting direction of the light valve, and the controlling the n lenses to move along the optical axis of the second lens group includes: When the projection lens projects onto a screen and the distance between the projection lens and the screen increases, controlling the first spherical lens and the second spherical lens to move along the optical axis of the second lens group in a direction away from the first lens group; When the projection lens projects onto a screen and the distance between the projection lens and the screen becomes smaller, the first spherical lens and the second spherical lens are controlled to move along the optical axis of the second lens group toward a direction close to the first lens group.

5. A focusing device for a projection lens, characterized in that: The focusing device of the projection lens comprises various modules for executing the focusing method of the projection lens according to claim 3 or 4.

6. A focusing device for a projection lens, characterized in that: include: processor; and a memory for storing executable instructions for said processor; Wherein, when the processor runs the executable instructions, it can implement the focusing method of the projection lens described in claim 3 or 4.

7. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores instructions; When the instruction is executed on a processing component, the processing component is caused to execute the focusing method of a projection lens according to claim 3 or 4.

8. A projector, characterized in that: The projector comprises: a driving assembly, a light valve and a projection lens according to any one of claims 1 to 2; The light valve, the first mirror group, the second mirror group and the third mirror group are arranged in sequence; The driving assembly is connected to each lens in the second lens group and is configured to control each lens to move along the optical axis of the second lens group.

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