High and low temperature resistant projection lens

Abstract

The embodiment of the utility model discloses a high and low temperature resistant projection lens, which comprises a first group lens with positive focal power, a diaphragm, a second group lens with positive focal power, a light splitting device, protective glass and an imaging surface which are coaxially and sequentially arranged, the first group lens comprises a first lens with negative focal power, a second lens with negative focal power and a third lens with positive focal power which are coaxially arranged in sequence; and the second group lens comprises a fourth lens with negative focal power, a fifth lens with negative focal power, a sixth lens with positive focal power and a seventh lens with positive focal power which are coaxially arranged in sequence. By implementing the projection lens provided by the embodiment of the utility model, an ultra-wide working temperature range can be realized, the projection lens is suitable for most extreme use conditions, and repeated lens focusing work is not needed in the temperature range.

Description

Technical Field

[0001] The utility model relates to the technical field of projection lenses, and particularly relates to a high and low temperature resistant projection lens. Background Art

[0002] The projection lens is the core component of a projection device, which is responsible for projecting the light passing through the light modulation device onto the screen to form an image. With the wide application of projection devices in fields such as movies, medical treatment, advertising, industry, and 3D printing, the requirements for its technical indicators are becoming increasingly diverse, including smaller image distortion, clarity, projection area, and projection ratio.

[0003] Due to the differences in temperature conditions in different usage environments, the performance of the projection lens may be limited. Each lens has a specific operating temperature range, and exceeding this range will cause a significant decline in performance. At extreme temperatures, ordinary projection lenses usually cannot work properly; moreover, the operating temperature range of most consumer-grade projection lenses is usually between 0°C and 40°C. Although this can meet general viewing needs, the range is relatively narrow. Beyond this temperature, the internal components of the lens deform due to temperature changes, which in turn affects the refractive index and optical performance of the lens, resulting in changes in the optical system, the position shift of the best imaging plane, and the generation of blurred images. At this time, refocusing is required, but this method of frequent adjustment according to temperature is not practical and lacks practical value.

[0004] Therefore, it is necessary to design a new lens that can achieve an ultra-wide operating temperature range, be applicable to most extreme usage conditions, and does not require repeated lens focusing within the temperature range. Summary of the Utility Model

[0005] The purpose of the utility model is to overcome the defects of the prior art and provide a high and low temperature resistant projection lens.

[0006] To solve the above technical problems, the purpose of the utility model is achieved through the following technical solutions: providing a high and low temperature resistant projection lens, including: a first group of lenses with positive optical power, a diaphragm, a second group of lenses with positive optical power, a beam splitter, a protective glass, and an imaging surface, which are arranged coaxially in sequence;

[0007] The first group of lenses includes a first lens with negative optical power, a second lens with negative optical power, and a third lens with positive optical power, which are arranged coaxially in sequence; the second group of lenses includes a fourth lens with negative optical power, a fifth lens with negative optical power, a sixth lens with positive optical power, and a seventh lens with positive optical power, which are arranged coaxially in sequence.

[0008] A further technical solution of it is: the first lens and the seventh lens are respectively aspherical glass lenses.

[0009] A further technical solution thereof is that: the fourth lens and the fifth lens are respectively glass spherical doublet lenses.

[0010] A further technical solution thereof is that: the aperture range of the diaphragm is from 8 mm to 8.5 mm.

[0011] A further technical solution thereof is that: the ratio of the focal length of the first group of lenses to the focal length of the objective lens system is 1.38.

[0012] A further technical solution thereof is that: the ratio of the focal length of the first lens to the focal length of the first group of lenses is -1.19;

[0013] The ratio of the focal length of the second lens to the focal length of the first group of lenses is 5.02;

[0014] The ratio of the focal length of the third lens to the focal length f1 of the first group of lenses is 1.67.

[0015] A further technical solution thereof is that: the ratio of the focal length of the second group of lenses to the focal length of the objective lens system is 2.22.

[0016] A further technical solution thereof is that: the ratio of the focal length of the fourth lens to the focal length of the second group of lenses is -0.73;

[0017] The ratio of the focal length of the fifth lens to the focal length of the second group of lenses is -2.58;

[0018] The ratio of the focal length of the sixth lens to the focal length of the second group of lenses is 1.36;

[0019] The ratio of the focal length of the seventh lens to the focal length of the second group of lenses is 1.49.

[0020] A further technical solution thereof is that: the gap between the first lens and the second lens is from 5 mm to 8 mm.

[0021] A further technical solution thereof is that: the gap range between the fifth lens and the sixth lens is from 1 mm to 2 mm.

[0022] The beneficial effects of the present utility model compared with the prior art are as follows: by providing a first group of lenses with positive optical power, a diaphragm, a second group of lenses with positive optical power, a beam splitter, a protective glass, and an imaging surface, the first group of lenses is composed of three lenses, the second group of lenses is composed of four lenses, aspherical glass lenses and spherical doublet lenses are used, and precise focal length ratios and gap ranges are set, so that the present utility model realizes an ultra-wide operating temperature range, is applicable to most extreme use conditions, and does not require repeated lens focusing work within the temperature range.

[0023] The present utility model will be further described below in conjunction with the accompanying drawings and specific embodiments. Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the accompanying drawings required for the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0025] Figure 1 Structural schematic diagram of a high and low temperature resistant projection lens provided by an embodiment of the present utility model;

[0026] Figure 2 Spatial frequency MTF diagram of a high and low temperature resistant projection lens provided by an embodiment of the present utility model at -40°C;

[0027] Figure 3 Spatial frequency MTF diagram of a high and low temperature resistant projection lens provided by an embodiment of the present utility model at 20°C;

[0028] Figure 4 Spatial frequency MTF diagram of a high and low temperature resistant projection lens provided by an embodiment of the present utility model at 150°C;

[0029] Figure 5 Field curvature evaluation diagram of a high and low temperature resistant projection lens provided by an embodiment of the present utility model;

[0030] Figure 6 Distortion evaluation diagram of a high and low temperature resistant projection lens provided by an embodiment of the present utility model;

[0031] Figure 7 Relative illumination diagram of a high and low temperature resistant projection lens provided by an embodiment of the present utility model;

[0032] Explanation of the markings in the figure:

[0033] 1. First group lens 1; 2. Diaphragm 2; 3. Second group lens 3; 4. Galvo 4; 5. Beam splitter prism; 6. Protective glass 6; 7. Imaging surface 7; G1. First lens; G2. Second lens; G3. Third lens; G4. Fourth lens; G5. Fifth lens; G6. Sixth lens; G7. Seventh lens. Detailed Embodiments

[0034] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are part of the embodiments of the present utility model, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.

[0035] It should be understood that when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, wholes, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or their combinations.

[0036] It should also be understood that the terms used in this specification of the present utility model are only for the purpose of describing specific embodiments and are not intended to limit the present utility model. As used in this specification of the present utility model and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" are intended to include the plural forms.

[0037] It should be further understood that the term "and / or" used in this specification of the present utility model and the appended claims refers to any combination and all possible combinations of one or more of the related listed items, and includes these combinations.

[0038] In the prior art, the temperature differences caused by different application environments limit the performance of projection lenses. Exceeding their applicable operating temperature range will result in a significant decline. Under extreme high or low temperature conditions, ordinary projection lenses usually cannot work properly.

[0039] Therefore, the embodiments of the present utility model propose a high and low temperature resistant projection lens, which controls the lens operating temperature range between -50°C and 150°C, achieving the requirements of an ultra-wide operating temperature range. Within the temperature range, there is no need to repeatedly focus the lens. It is applicable to most extreme use conditions and has a series of advantages such as high imaging quality, small temperature influence, small distortion, reasonable tolerances, and low cost, and has high practical application value.

[0040] To better understand the above technical solutions, the above technical solutions will be described in detail below in conjunction with the accompanying drawings of the specification and specific implementation manners.

[0041] Please refer to Figure 1 , Figure 1Schematic diagram of the structure of a high and low temperature resistant projection lens provided by an embodiment of the present utility model; A high and low temperature resistant projection lens, characterized in that it includes: a first group of lenses 1 with positive optical power, a diaphragm 2, a second group of lenses 3 with positive optical power, a beam splitting device, a protective glass 6, and an imaging surface 7, which are arranged coaxially in sequence;

[0042] The first group of lenses 1 is located in front of the diaphragm 2. The first group of lenses 1 includes a first lens G1 with negative optical power, a second lens G2 with negative optical power, and a third lens G3 with positive optical power, which are arranged coaxially in sequence; The second group of lenses 3 is located behind the diaphragm 2. The second group of lenses 3 includes a fourth lens G4 with negative optical power, a fifth lens G5 with negative optical power, a sixth lens G6 with positive optical power, and a seventh lens G7 with positive optical power, which are arranged coaxially in sequence.

[0043] Specifically, the light source lens group emits light and makes the light rays parallel. The diaphragm 2 is used to adjust the amount of light emitted by the light source lens group. The first group of lenses 1 adjusts the field angle of projection and the field curvature balance of the system, while the second group of lenses 3 is used to balance the aberration and chromatic aberration of the system. The projection lens of this embodiment is paired with a 0.3-inch DMD chip, with an off-axis ratio of 0%. It can clearly image and work within the temperature range of -50°C to 150°C. This lens has advantages such as low distortion of less than 0.55%, good imaging quality, large field of view, and is easy to manufacture and assemble. Particularly, this lens has an ultra-wide operating temperature range and is suitable for most extreme usage conditions.

[0044] In one embodiment, the first lens G1 and the seventh lens G7 are respectively aspherical glass lenses.

[0045] In one embodiment, the fourth lens G4 and the fifth lens G5 are respectively glass spherical doublet lenses. A doublet lens is placed behind the STO diaphragm 2. The combination of its low refractive index and high Abbe number and high refractive index and low Abbe number materials effectively reduces the secondary spectrum of the system; The fourth lens G4 is made of a material with high refractive index and low Abbe number and a material with low refractive index and high Abbe number (1.80 < n4 < 2.0, 30 < v4 < 35), and the fifth lens G5 is made of a material with low refractive index and high Abbe number (1.45 < n5 < 1.55, 65 < v5 < 80), where nd is the refractive index of the d-th lens, vd is the Abbe constant of the d-th lens, and d is a positive integer greater than 0.

[0046] In one embodiment, the first lens G1, the second lens G2, the third lens G3, the fourth lens G4, the fifth lens G5, the sixth lens G6, and the seventh lens G7 are respectively lenses made of glass materials.

[0047] In one embodiment, the aperture range of the diaphragm 2 is 8 mm to 8.5 mm; The relative aperture F number reaches 1.5, the aperture of the entire objective lens system is large, and the light input is large.

[0048] In one embodiment, the sixth lens G6 and the seventh lens G7 have positive optical powers. While correcting aberrations, it ensures that the incident angles of the chief rays in each field of view are exactly matched with the emission cone angle and angular vector of the image source, thereby improving the image quality and efficiency of the entire imaging system. The CRA range is within ±2.5°. CRA refers to the angle between the chief ray and the image plane.

[0049] In one embodiment, the beam splitting device includes a galvanometer 4 and a beam splitting prism 5 arranged coaxially and sequentially.

[0050] In this embodiment, the specific parameter table of the objective lens system formed by the high and low temperature resistant projection lens is shown in Tables 1 and 2.

[0051] Table 1. Specific Parameter Table of the Objective Lens System

[0052]

[0053]

[0054] Table 2. Specific Parameter Table of the Objective Lens System

[0055]

[0056] In one embodiment, the ratio of the focal length of the first group of lenses 1 to the focal length of the objective lens system is 1.38.

[0057] In one embodiment, the ratio of the focal length of the first lens G1 to the focal length of the first group of lenses 1 is -1.19;

[0058] The ratio of the focal length of the second lens G2 to the focal length of the first group of lenses 1 is 5.02;

[0059] The ratio of the focal length of the third lens G3 to the focal length f1 of the first group of lenses 1 is 1.67.

[0060] In one embodiment, the ratio of the focal length of the second group of lenses 3 to the focal length of the objective lens system is 2.22.

[0061] In one embodiment, the ratio of the focal length of the fourth lens G4 to the focal length of the second group of lenses 3 is -0.73;

[0062] The ratio of the focal length of the fifth lens G5 to the focal length of the second group of lenses 3 is -2.58;

[0063] The ratio of the focal length of the sixth lens G6 to the focal length of the second group of lenses 3 is 1.36;

[0064] The ratio of the focal length of the seventh lens G7 to the focal length of the second group of lenses 3 is 1.49.

[0065] In one embodiment, the gap between the above-mentioned first lens G1 and second lens G2 is 5 mm to 8 mm.

[0066] In one embodiment, the gap range between the above-mentioned fifth lens G5 and sixth lens G6 is 1 mm to 2 mm.

[0067] Please refer to Figures 2 to 4 , in this embodiment, the pixel size of the 0.3-inch DMD image source is 5.4 um, and the corresponding design resolution is 93 line pairs per millimeter. Generally, the MTF value of each field of view of the projection lens is required to reach above 0.3 in the design. As Figure 2 shown, at -40 °C, the MTF value is above 0.5; as Figure 3 shown, at 20 °C, the MTF value is above 0.5; as Figure 3 shown, at 150 °C, the MTF value is above 0.5; thus, it can be seen that at -40 °C, 20 °C, and 150 °C, the MTF values of each field of view are all above 0.5; the MTF index is the most accurate and scientific evaluation standard for lenses at present. 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.

[0068] Please refer to Figure 5 and Figure 6 , the ordinate represents the field 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 amount of distortion. Distortion is a very important index of the projection lens; the distortion of the objective lens system in this embodiment is within 0.55%, achieving ultra-low distortion.

[0069] Please refer to Figure 7 , the edge illumination of the high and low temperature resistant projection lens in this embodiment reaches 83%, making the uniformity of the projection effect of the system imaging surface 7 very good. The relative illumination refers to the ratio of the illuminance at different coordinate points on the image plane to the illuminance at the center point. The ordinate represents the normalized illuminance value, and the abscissa represents the field angle of the lens. Under the same conditions, the smoother the relative illumination curve of each field of view, the more uniform the illuminance within the projection frame. The closer the relative illumination value of each field of view is to 1, the higher the final projection brightness. Generally, for consumer projection lenses, a relative illumination greater than 0.6 can well meet the usage requirements of people.

[0070] In one embodiment, the projection lens has a large aperture, with a relative aperture F# reaching 1.75 and a large total luminous flux. The optical distortion of the projection lens is less than 0.55%, achieving an ultra-low distortion effect. The first lens G1 is made of optical glass with a refractive index of 1.49. The use of a meniscus lens with a high refractive index can effectively reduce the beam height, which is of great significance for correcting distortion and reducing the aperture of subsequent lenses. The projection lens uses a 0.3-inch image source. The relative illumination of the projection lens is greater than 0.8, which is beneficial to improving the uniformity of the optical engine. The projection lens uses a light source with a wavelength of 459 - 618 nm. The selected lens materials have a high transmittance for light with a wavelength of 459 - 618 nm. All lenses are glass spherical lenses, which are easy to process, have low costs, and are less affected by temperature changes, effectively avoiding the serious problem of focus shift caused by the easy heat absorption of plastic aspherical lenses and having good resistance to temperature effects. The working distance of the projection lens is in the range of 1 - 2 meters.

[0071] In this embodiment, the relative illumination of the projection lens in the full field of view is higher than 0.8%, and the MTF in the full field of view is higher than 0.5 within the temperature range of -50°C to 150°C, with excellent imaging quality. The distortion can reach within 0.%, with excellent distortion correction. The spot radius of the point spread function (<4um) is smaller than the pixel size (5.4um), which has obvious advantages for applications such as projection display that focus on spot size and energy concentration.

[0072] The selected lens materials of the projection lens in this embodiment have a high transmittance for light with a wavelength of 459 - 618 nm, all exceeding 95% / 10mm. The overall imaging system has relatively little energy absorption. First, it can improve the overall brightness. Second, it can reduce the system heat generation, reduce the power and size of the heat dissipation device, and contribute to the stability of projection imaging.

[0073] The designed wavelengths of the projection lens in this embodiment are 459 nm, 536 nm, and 618 nm, which cover the wavelength fluctuations of actual visible light sources, making the lens design more in line with the actual situation.

[0074] The projection lens in this embodiment has a large aperture, with a relative aperture F# reaching 1.75. The larger the aperture, the greater the light input, the corresponding higher the brightness, and the higher the light efficiency.

[0075] The glass thickness of each lens of the projection lens in this embodiment does not exceed 7.3 mm. The overall system length dimension is small, controlled within 60 mm.

[0076] In one embodiment, the ratio of the combined focal length of the first group of lenses 1 to the combined focal length of the second group of lenses 3 is close to 0.6, and the length of the two lens groups is 45 mm.

[0077] In one embodiment, the projection lens satisfies the following conditional formula:

[0078] 12 < TL / IH < 20; where TL represents the overall optical length of the optical lens, and IH represents the actual semi-image height of the optical lens.

[0079] When 12 < TL / IH < 20, the relationship between the overall length of the lens and the resolution ability can be reasonably balanced. When the value of TL / IH exceeds the upper limit, the overall length of the lens is too large, or if the overall length is shortened, the image height will be insufficient; when the value of TL / IH 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 drops significantly.

[0080] In one embodiment, the projection lens satisfies the following conditional formula:

[0081] 2mm < IH / tanθ < 3mm; where IH represents the actual semi-image height of the optical lens, and θ represents the semi-field angle of the optical lens.

[0082] When the conditional formula 2mm < IH / tanθ < 3mm 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.

[0083] In one embodiment, the projection lens satisfies the following conditional formula:

[0084] 1.4 < Nd1 < 1.8; 75 < Vd1 < 85; where Nd1 represents the refractive index of the first lens, and Vd1 represents the dispersion coefficient of the first lens.

[0085] When 1.4 < Nd1 < 1.8; 75 < Vd1 < 85, the selection of the glass material of the first lens can be reasonably limited, the aberration of other optical lenses can be balanced, and the beam height can be effectively reduced, which has a great effect on correcting distortion and reducing the aperture of subsequent lenses.

[0086] In one embodiment, the projection lens satisfies the following conditional formula:

[0087] CRA < 2.5°; where CRA represents the main ray incident angle of the optical lens on the imaging surface 7.

[0088] When CRA < 2.5°, it can well match image sources such as DMD chips or LEDs to achieve a good projection effect.

[0089] In one embodiment, the curvature radii of the first lens G1 and the sixth lens G6 are arranged as positive, positive, negative, and negative, which can effectively control the gentle transition of light, thereby reducing the tolerance sensitivity of these two lenses, and further improving the actual production yield.

[0090] The projection lens of this embodiment is paired with a 0.3-inch DMD chip, with an off-axis ratio of 0%. It can clearly image and work within the temperature range of -50°C to 150°C. This lens has the advantages of low distortion of less than 0.55%, good imaging quality, large field of view, easy manufacturing and assembly. Particularly, this lens has an ultra-wide operating temperature range and is suitable for most extreme usage conditions.

[0091] The above-mentioned high and low temperature resistant projection lens is configured with a first group of lenses 1 with positive optical power, a diaphragm 2, a second group of lenses 3 with positive optical power, a beam splitter device, a protective glass 6, and an imaging surface 7. The first group of lenses 1 is composed of three lenses, and the second group of lenses 3 is composed of four lenses. Aspherical glass lenses and spherical doublet lenses are used, and precise focal length ratios and gap ranges are set to achieve an ultra-wide operating temperature range, suitable for most extreme usage conditions, and no need to repeatedly focus the lens within the temperature range.

[0092] As mentioned above, the above are only the specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A high and low temperature resistant projection lens, characterized in that, Comprising: A first group of lenses with positive optical power, a diaphragm, a second group of lenses with positive optical power, a beam splitter, a protective glass, and an imaging surface, which are arranged coaxially and in sequence; The first group of lenses includes a first lens with negative optical power, a second lens with negative optical power, and a third lens with positive optical power, which are arranged coaxially and in sequence; the second group of lenses includes a fourth lens with negative optical power, a fifth lens with negative optical power, a sixth lens with positive optical power, and a seventh lens with positive optical power, which are arranged coaxially and in sequence.

2. The high and low temperature resistant projection lens according to claim 1, characterized in that The first lens and the seventh lens are respectively aspherical glass lenses.

3. A high and low temperature resistant projection lens according to claim 1, characterized in that, The fourth lens and the fifth lens are respectively glass spherical doublet lenses.

4. A high and low temperature resistant projection lens according to claim 1, characterized in that, The aperture range of the diaphragm is from 8 mm to 8.5 mm.

5. A high and low temperature resistant projection lens according to claim 1, characterized in that The ratio of the focal length of the first group of lenses to the focal length of the objective system is 1.

38.

6. The high and low temperature resistant projection lens according to claim 5, characterized in that, The ratio of the focal length of the first lens to the focal length of the first group of lenses is -1.19; The ratio of the focal length of the second lens to the focal length of the first group of lenses is 5.02; The ratio of the focal length of the third lens to the focal length f1 of the first group of lenses is 1.

67.

7. The high and low temperature resistant projection lens according to claim 1, characterized in that, The ratio of the focal length of the second group of lenses to the focal length of the objective system is 2.

22.

8. A high and low temperature resistant projection lens according to claim 7, characterized in that, The ratio of the focal length of the fourth lens to the focal length of the second group of lenses is -0.73; The ratio of the focal length of the fifth lens to the focal length of the second group of lenses is -2.58; The ratio of the focal length of the sixth lens to the focal length of the second group of lenses is 1.36; The ratio of the focal length of the seventh lens to the focal length of the second group of lenses is 1.

49.

9. The high and low temperature resistant projection lens according to claim 1, wherein The gap between the first lens and the second lens is from 5 mm to 8 mm.

10. A high and low temperature resistant projection lens according to claim 1, characterized in that, The gap range between the fifth lens and the sixth lens is from 1 mm to 2 mm.

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