Small focus-segment-divided relay lens and projection imaging system

Abstract

The invention relates to the technical field of optical lenses, and discloses a small focal-segment-divided relay lens and a projection imaging system. Wherein N is a natural number which is not 0; at least one lens is an aspheric lens, at least one lens is a high-refractive-index glass lens, and a second equivalent focal length of the relay lens is determined according to a first equivalent focal length of the prime lens; if the first equivalent focal length is greater than a third equivalent focal length, N is less than or equal to a preset value; if the first equivalent focal length is smaller than the third equivalent focal length, N is larger than a preset value. The invention has the advantages that on the basis of the fixed projection ratio of the prime lens, different relay lenses are replaced, so that different projection focal lengths and projection picture sizes are realized, and the use scene of the lens is expanded; therefore, clear picture analysis is ensured, and high-resolution projection imaging quality is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of optical lenses, and in particular to a small focal segment relay lens and a projection imaging system. Background Art

[0002] In photography practice, users often need to adjust the focal length according to the scene requirements: in order to capture a wide landscape, reducing the focal length can include more scenery, giving the picture a rich spatial layering and perspective effect; facing close-up objects, short-focus lenses can effectively reduce the deformation of objects caused by perspective effects, ensuring that the people or objects in the picture maintain a natural proportion; and when shooting distant objects or sports events, telephoto lenses can accurately magnify the subject, making it dominate the picture. These diverse needs have led to the birth of zoom lenses, which provide photographers with great flexibility.

[0003] However, existing zoom lenses have operational challenges, and focal length adjustment often requires certain skills and experience. For photography novices, it may be difficult to accurately control the change of focal length, which in turn affects the final shooting quality. In addition, zoom lenses are usually expensive and have relatively high maintenance costs, which undoubtedly increases the financial pressure and learning costs of users.

[0004] Relay lenses are often used in imaging detection, where a close object is transformed into a smaller virtual image at a farther distance. The virtual image is the mirror image of the actual detection target. Similarly, the corresponding design of relay lenses in the field of photography can be used to extend or reduce the focal length of the lens, achieving flexible adjustment of the focal length.

[0005] Most existing relay lenses are fixed on fixed-focus lenses, so they have a fixed focal length and cannot be adjusted according to shooting needs. When the focal length needs to be changed to adapt to different shooting scenes, users can only replace the lens as a whole, which not only increases the complexity and time cost of shooting, but also increases the overall investment cost. In addition, in order to meet diverse shooting needs, users often need to carry multiple lenses, which not only increases the trouble and weight of carrying, but also brings many inconveniences, especially for users who need to go out frequently to shoot.

[0006] Therefore, there is an urgent need to invent a small focal segment relay lens and a projection imaging system to solve the above problems. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a small focal-segment relay lens and a projection imaging system. The scheme of the present invention can achieve different projection focal lengths and projection picture sizes by replacing different relay lenses on the basis of the fixed projection ratio of the fixed-focus lens, thereby expanding the use scenarios of the lens; ensuring clear picture resolution and achieving high-resolution projection imaging quality.

[0008] The present invention provides a small focal segment relay lens, which is used to change the first equivalent focal length of a fixed-focus lens to a third equivalent focal length, comprising: N lenses arranged coaxially; wherein N is a natural number not equal to 0; at least one lens is an aspherical lens, at least one lens is a high refractive index glass lens, and the second equivalent focal length of the relay lens is determined according to the first equivalent focal length and the third equivalent focal length of the fixed-focus lens; If the first equivalent focal length is greater than the third equivalent focal length, then N is less than or equal to a preset value; If the first equivalent focal length is smaller than the third equivalent focal length, N is greater than a preset value.

[0009] Further, determining the second equivalent focal length of the relay lens according to the first equivalent focal length and the third equivalent focal length of the fixed-focus lens includes: calculating the second equivalent focal length by the following formula: , Among them, F1 is the first equivalent focal length, F2 is the second equivalent focal length, and F3 is the third equivalent focal length. is the transformation constant of the relay lens and satisfies the following range: .

[0010] Furthermore, 8.25mm<|F1|<16mm, 5.1mm<|F3|<21mm.

[0011] Furthermore, the refractive index of the high-refractive-index glass lens is greater than or equal to 1.7.

[0012] Furthermore, the range of N is 2-5, and the range of the preset value is 3-4.

[0013] Furthermore, the minimum axial distance between the side of the lens of the relay lens close to the fixed-focus lens and the side of the lens of the fixed-focus lens close to the relay lens is D, and 0.3 mm <D<15mm。

[0014] In a second aspect, the present application provides a small focal segment projection imaging system, comprising: a fixed-focus lens having a first equivalent focal length; the relay lens described in the first aspect; and an offset mirror, a TIR prism and a light valve sequentially arranged on the eyepiece side of the fixed-focus lens.

[0015] Furthermore, the relay lens is detachably connected to the objective lens side of the fixed-focus lens.

[0016] The embodiments of the present invention have the following technical effects: The present application calculates the second equivalent focal length of the relay lens according to the first equivalent focal length of the fixed-focus lens and the third equivalent focal length to be adjusted. For each first equivalent focal length, the second equivalent focal length corresponding to different third equivalent focal lengths can be calculated, so that different relay lenses can be designed according to the second equivalent focal length to freely switch the corresponding relay lenses for each required focal length projection; wherein the number of lenses can be determined according to the size of the projection screen to be achieved; for each relay lens, at least one aspherical lens is included to correct aberrations; at least one high-refractive-index glass lens is included to achieve rapid changes in light emitted from the fixed-focus lens; This application can achieve different projection focal lengths and projection screen sizes by replacing different relay lenses on the basis of the fixed projection ratio of the fixed-focus lens, thereby expanding the use scenarios of the lens; ensuring clear image resolution and achieving high-resolution projection imaging quality; In summary, during use, the user only needs to detachably fix the relay lens as an accessory on the fixed-focus lens to realize the focal length segmentation function, solve the problem of cumbersome adjustments during the change of the lens focal length, and achieve the projection image quality of the zoom lens performance at a lower cost and complexity. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 is a schematic diagram of a small focal segment projection imaging system provided by an embodiment of the present invention; Figure 2 is a schematic diagram of an imaging system provided by Embodiment 3 of the present invention; Figure 3 is a diagram of light spots under different field of view conditions on an imaging screen provided by Embodiment 3 of the present invention; Figure 4 : is a schematic diagram of TV distortion provided by Example 3 of the present invention. In the left coordinate system, the horizontal coordinate represents the magnitude of field curvature, in units of mm, and the vertical coordinate represents the normalized image height; in the right coordinate system, the horizontal coordinate represents the magnitude of distortion, in units of %, and the vertical coordinate represents the normalized image height; Figure 5 3 is a curve showing the relationship between the modulus and frequency of the optical transfer function provided in Example 3 of the present invention.

[0019] In the figure, 1, relay lens; 11, first lens; 12, second lens; 2, fixed focus lens; 3, bias mirror; 4, TIR prism; 5, light valve. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0021] First, the following are explained: Since the photosensitive elements of different camera systems are of different sizes, the imaging angle of view will be different even if the lens with the same focal length is used, so the equivalent focal length is introduced. The equivalent focal length is a converted focal length value that converts the imaging angle of view on photosensitive elements of different sizes into the lens focal length corresponding to the same imaging angle of view on other cameras. The equivalent focal length can be used to easily compare the imaging angles of different camera systems at the same focal length.

[0022] The focal length determines the distance of light from the projector to the image, and the projection ratio is the ratio of this distance to the actual projection distance. Therefore, the focal length and the projection ratio are positively correlated. When the projection ratio is changed, the focal length will also change accordingly. Determining the projection ratio determines the focal length. In this application, the focal length is set by setting the projection ratio. Example 1

[0023] The present invention provides a small focal segment relay lens, which is used to change the first equivalent focal length of a fixed-focus lens into a third equivalent focal length, and specifically comprises: N lenses are coaxially arranged; wherein N is a natural number not equal to 0; illustratively, the range of N is 2 to 5, which is a preferred range and is not limited to this range.

[0024] At least one lens is an aspherical lens; the radius of curvature of the aspherical lens gradually increases from the center to the periphery, that is, the surface of the lens gradually becomes flat, which changes the single curvature of the traditional spherical lens and reduces edge distortion, that is, reduces aberrations and provides a wider field of view; and the design of the aspherical lens makes the lens thinner and flatter, which is more conducive to reducing the length of the relay lens and making the optical system more compact as a whole; it should be noted that the more aspherical lenses there are, the more complex the impact on the overall focal length characteristics of the system, and the number of aspherical lenses should be minimized to ensure the overall stability of the system and reduce the complexity of the system.

[0025] At least one lens is a high-refractive-index glass lens; a high-refractive-index lens can bend and focus light more effectively, reduce reflection and scattering of light, and allow more light to be precisely focused on one point, thereby improving the resolution and imaging quality of the optical system; illustratively, the refractive index of the high-refractive-index glass lens is greater than or equal to 1.7, such as 1.8 or 2.05 or 1.92, etc., and is set according to actual conditions. The present application does not limit the positions of the high-refractive-index glass lens and the aspherical lens. Relative to the aspherical lens, the high-refractive-index glass lens is usually located close to the fixed-focus lens end.

[0026] Determine the second equivalent focal length of the relay lens according to the first equivalent focal length and the third equivalent focal length of the fixed-focus lens; Specifically, the second equivalent focal length is calculated by the following formula: , Among them, F1 is the first equivalent focal length, F2 is the second equivalent focal length, and F3 is the third equivalent focal length. is the transformation constant of the relay lens; it should be noted that the second equivalent focal length can be simply calculated according to the following formula: ; The above formula calculates a specific value, but in actual production, it is often necessary to comprehensively consider the cost, total length of the optical system, error range and other aspects to design the relay lens, so as to take multiple aspects into consideration at the same time. Therefore, the design formula of this application is derived, and the calculated second equivalent focal length is calculated by the transformation constant Decide, When the following range is met, it can be ensured that the relay lens design at the second equivalent focal length is basically satisfied around the third equivalent focal length.

[0027] .

[0028] It should be noted that it has been verified that within the range of the above transformation constants, the design requirements for the second equivalent focal length can be met; however, the best value for the relay lens design effect still needs to be verified based on experiments, and this application will not elaborate on it.

[0029] In addition, 8.25mm<|F1|<16mm, 5.1mm<|F3|<21mm, which can meet the commonly used equivalent focal length range.

[0030] There are two situations for adjusting the focal length: one is to increase the focal length, and the other is to decrease the focal length. For these two situations, the number of lenses is set differently: (1) If the first equivalent focal length is greater than the third equivalent focal length, then N is less than or equal to a preset value; at this time, the upcoming shooting screen changes from large to small, and at this time, the relay lens requires fewer lenses, and there is no need for too many lenses to correct aberrations, etc. Exemplarily, when the projection ratio of the fixed-focus lens is 1.2, and the required projection ratio is 0.9; then at this time, the corresponding first equivalent focal length is greater than the third equivalent focal length. At this time, if the preset value is 3, then N is less than or equal to 3, and 2 lenses can be set to achieve this.

[0031] (2) If the first equivalent focal length is less than the third equivalent focal length, then N is greater than the preset value; at this time, the upcoming shooting screen changes from small to large, and at this time, the relay lens requires more lenses, and more lenses are needed to correct aberrations, etc.

[0032] Exemplarily, when the projection ratio of the fixed-focus lens is 1.2, and the required projection ratio is 1.5; then at this time, the corresponding first equivalent focal length is less than the third equivalent focal length. At this time, if the preset value is 3, then N is greater than 3, and 5 lenses can be set to achieve this.

[0033] In addition, the minimum axial distance from the side of the relay lens close to the fixed-focus lens to the side of the fixed-focus lens close to the relay lens is D, which should satisfy 0.3mm < D < 15mm, that is Figure 2 the distance between the two red dots, which ensures that the overall optical system meets the characteristics of miniaturization of the relay lens.

[0034] Based on the above technical solutions, the present application can, on the basis of the fixed projection ratio of the fixed-focus lens, by replacing different relay lenses, achieve different projection focal lengths and projection screen sizes, expand the usage scenarios of the lens; ensure clear picture resolution and achieve high-resolution projection imaging quality; During use, the user only needs to detachably fix the relay lens as a accessory on the fixed-focus lens to achieve the focal length segmentation function, solve the problem of cumbersome adjustment during the change of the lens focal length, and achieve the projection image quality of the zoom lens performance with lower cost and complexity. Embodiment 2

[0035] Based on the content of Embodiment 1, the present application provides a small focal length-segmented projection imaging system, see Figure 1 , including: A fixed-focus lens 2 with a first equivalent focal length; The relay lens 1 described in Embodiment 1; the relay lens 1 is located on the objective side of the fixed-focus lens 2; A beam splitter 3, a TIR prism 4, and a light valve 5 are sequentially arranged on the eyepiece side of the fixed-focus lens 2.

[0036] The relay lens 1 is detachably connected to the objective lens side of the fixed-focus lens 2. For example, the relay lens is fixed to the objective lens side of the fixed-focus lens by magnetic attraction and can be removed or installed as needed.

[0037] The fixed-focus lens eyepiece side is provided with a bias mirror 3, a TIR prism 4 and a light valve 5 in sequence. The bias mirror 3 is a polarizing filter, which can reduce the amount of light entering the lens and eliminate stray light; the TIR prism 4 can effectively control the propagation direction of the light, realize the deflection or focusing of the light, thereby providing a uniform light distribution, so that the light maintains a stable brightness during the transmission process; the light valve 5 can be a DMD chip or an LCos chip, etc. The light valve 5 is used to control the passage and blocking of light to achieve precise control of light. The settings of the bias mirror 3, the TIR prism 4 and the light valve 5 are prior art, and this application will not make too many explanations.

[0038] For other details, please refer to Example 1 and will not be described in detail here. Example 3

[0039] Based on Example 1, the present application provides a specific embodiment, in which the first equivalent focal length 12.6333 mm is changed to a third equivalent focal length 15.85 mm: See also Figure 2 , N is 2, the first lens 11 is an aspherical lens, the second lens 12 is a high refractive index glass lens, is 3040.08, and the corresponding second equivalent focal length is 14901.6mm. Other parameter settings of the relay lens are shown in Table 1 below.

[0040] Table 1 Parameter settings of the first lens and the second lens

[0041] Among them, 30.523mm is the radius of curvature of the first lens away from the second lens, 54.34mm is the radius of curvature of the first lens close to the second lens; 37.015mm is the radius of curvature of the second lens away from the first lens, 25.056mm is the radius of curvature of the second lens close to the first lens; similarly, the cone coefficient is the taper that characterizes the aspheric surface and is set corresponding to the radius of curvature. 11.284mm is the center thickness of the first lens, 2mm is the center thickness of the second lens, 4.208mm is the value of D, and 12.551mm is the distance between the first lens and the second lens on the optical axis.

[0042] Based on the above settings, relevant experimental verification was carried out: Figure 3 The figure is a schematic diagram of point spot imaging of three typical wavelengths of light under normalized different field of view conditions, where IMA represents the image plane; Figure 3 It shows that under different wavelength conditions, the convergence effect of the light spot is good.

[0043] Figure 4 The left coordinate system shows that the difference between the image quality in the center and the periphery is small during imaging, while the right coordinate system shows that the imaging distortion is small, meeting the requirement of low distortion.

[0044] Figure 5 In the embodiment, the larger the modulus of the optical transfer function is, the stronger the resolution is, and the lens can restore the details and contrast of the object more clearly. In this embodiment, the resolution of the projection lens is greater than 0.55@66lp / mm.

[0045] It should be noted that the terms used in the present invention are only for describing specific embodiments, rather than limiting the scope of the present application. As shown in the present specification, unless the context clearly indicates an exception, the words "one", "a", "a kind of" and / or "the" do not specifically refer to the singular, but may also include the plural. The terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method or device. In the absence of more restrictions, the elements defined by the sentence "include one..." do not exclude the presence of other identical elements in the process, method or device including the elements.

[0046] It should also be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. Unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", etc. should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A small focal-segment relay lens for changing a first equivalent focal length of a fixed-focus lens to a third equivalent focal length, characterized in that: include: N lenses arranged coaxially; wherein N is a natural number not equal to 0; at least one lens is an aspherical lens, at least one lens is a high refractive index glass lens, and the second equivalent focal length of the relay lens is determined according to the first equivalent focal length and the third equivalent focal length of the fixed-focus lens; If the first equivalent focal length is greater than the third equivalent focal length, then N is less than or equal to a preset value; If the first equivalent focal length is smaller than the third equivalent focal length, N is greater than a preset value.

2. The small focal-segment relay lens according to claim 1, characterized in that: Determining the second equivalent focal length of the relay lens according to the first equivalent focal length and the third equivalent focal length of the fixed-focus lens includes: calculating the second equivalent focal length by the following formula: ， Among them, F1 is the first equivalent focal length, F2 is the second equivalent focal length, and F3 is the third equivalent focal length. is the transformation constant of the relay lens and satisfies the following range: 。 3. The small focal segment relay lens according to claim 2, characterized in that: 8.25mm<|F1|<16mm, 5.1mm<|F3|<21mm.

4. The small focal-segment relay lens according to claim 1, characterized in that: The refractive index of the high-refractive-index glass lens is greater than or equal to 1.

7.

5. The small focal-segment relay lens according to claim 1, characterized in that: The range of N is 2-5, and the range of the preset value is 3-4.

6. The small focal-segment relay lens according to claim 1, characterized in that: The minimum axial distance between the side of the lens of the relay lens close to the fixed-focus lens and the side of the lens of the fixed-focus lens close to the relay lens is D, and is 0.3mm <D<15mm。 7. A small focal segment projection imaging system, characterized in that: include: A fixed-focus lens (2) having a first equivalent focal length; The relay lens (1) according to any one of claims 1 to 6; the relay lens (1) is located on the objective lens side of the fixed-focus lens (2); An offset mirror (3), a TIR prism (4) and a light valve (5) are sequentially arranged on the eyepiece side of the fixed-focus lens (2).

8. The small focal segment projection imaging system according to claim 7, characterized in that: The relay lens is detachably connected to the objective lens side of the fixed-focus lens.

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