A projection optical system

Abstract

This application relates to a projection optical system, comprising a lens barrel and a color combining prism assembly arranged sequentially along the optical axis from the imaging side to the image source side. The lens barrel contains a first lens, a second lens, a third lens, and a fourth lens. A spacer element is provided between adjacent lenses in the lens barrel. The color combining prism assembly includes a color combining prism and red, green, and blue light-emitting chips. The green light-emitting chip is arranged perpendicular to the optical axis, and the red and blue light-emitting chips are arranged parallel to the optical axis. The diagonal surfaces of the color combining prism are respectively provided with blue and red bandpass filters. The projection optical system satisfies: 1.05 < d3s / |R6| < 3.05; 1.43 ≤ EP23 / CT3 ≤ 2.70.

Description

Technical Field

[0001] This invention relates to the field of projection optical system technology, and in particular to a projection optical system. Background Technology

[0002] With the development of AR glasses, consumers have increasingly higher demands for the image quality projected by the devices. To provide consumers with a better experience, perfectly integrate real and virtual scenes, achieve real-time interaction, and enrich the color experience, an RGB three-color light projection optical system is needed to perceive and project the required image information. In an RGB three-color light projection system, the changes in lens focal length at three different wavelengths need to be considered, which undoubtedly increases the difficulty of the projection system design. Specifically, in a four-element projection optical system, there is a problem of high eccentricity and tilt sensitivity during the shaping of the third lens, affecting the imaging quality of the optical system. Summary of the Invention

[0003] This application provides a projection optical system, including a lens barrel and a color-combining prism assembly arranged sequentially along the optical axis from the imaging side to the image source side; the lens barrel includes: a first lens with positive optical power, the imaging side being convex and the image source side being convex; a second lens with positive or negative optical power, the image source side being concave; a third lens with negative optical power; a fourth lens with positive or negative optical power, the image source side being convex; a first spacer element is disposed between the first lens and the second lens, and the first spacer element abuts against the image source side of the first lens; a second spacer element is disposed between the second lens and the third lens, and the second spacer element abuts against the image source side of the second lens; a third spacer element is disposed between the third lens and the fourth lens, and the third spacer element abuts against the image source side of the third lens; the color-combining prism assembly includes a color-combining prism, The system comprises a red light-emitting chip, a green light-emitting chip, and a blue light-emitting chip; the two diagonal faces of the color-combining prism are respectively provided with a blue light bandpass filter and a red light bandpass filter; the green light-emitting chip is arranged perpendicular to the optical axis, and the red light-emitting chip and the blue light-emitting chip are arranged parallel to the optical axis, so that the light emitted by the red light-emitting chip and the blue light-emitting chip can be reflected by the blue light bandpass filter and the red light bandpass filter respectively and then directed to the image source side of the fourth lens; the projection optical system satisfies: 1.05 < d3s / |R6| < 3.05; 1.43 ≤ EP23 / CT3 ≤ 2.70; where d3s is the inner diameter of the imaging side of the third spacer element, R6 is the radius of curvature of the image source side of the third lens, EP23 is the distance from the image source side of the second spacer element to the imaging side of the third spacer element along the optical axis, and CT3 is the center thickness of the third lens on the optical axis.

[0004] In some embodiments of this application, the light emitted by the green light-emitting chip has a wavelength range of 509nm to 545nm, the light emitted by the red light-emitting chip has a wavelength range of 615nm to 655nm, and the light emitted by the blue light-emitting chip has a wavelength range of 450nm to 470nm.

[0005] In some embodiments of this application, the green light-emitting chip emits light at a first wavelength of 527 nm, the red light-emitting chip emits light at a second wavelength of 635 nm, and the blue light-emitting chip emits light at a third wavelength of 460 nm.

[0006] In some embodiments of this application, the projection optical system satisfies: 1.00≤|f2R-f2B| / EP12≤3.48; where f2R is the focal length of the second lens of the projection optical system at the second wavelength, f2B is the focal length of the second lens of the projection optical system at the third wavelength, and EP12 is the distance along the optical axis from the image source side of the first spacer element to the imaging side of the second spacer element.

[0007] In some embodiments of this application, the projection optical system satisfies: 1.78≤(D3m-d3m) / |f4R-f4B|≤8.43; where D3m is the outer diameter of the image source side of the third spacer element, d3m is the inner diameter of the image source side of the third spacer element, f4R is the focal length of the fourth lens of the projection optical system at the second wavelength, and f4B is the focal length of the fourth lens of the projection optical system at the third wavelength.

[0008] In some embodiments of this application, the projection optical system satisfies: 3.55≤d1s / CT1≤6.11; where d1s is the inner diameter of the imaging side of the first spacer element, and CT1 is the center thickness of the first lens on the optical axis.

[0009] In some embodiments of this application, the projection optical system satisfies: 2.17≤f1G / EP01≤6.33; where f1G is the focal length of the first lens of the projection optical system at the first wavelength, and EP01 is the distance along the optical axis from the imaging side of the lens barrel to the imaging side of the first spacer element.

[0010] In some embodiments of this application, the projection optical system satisfies: 0.30 < CP1 / CT2 < 1.65; where CP1 is the maximum thickness of the first spacer element along the optical axis, and CT2 is the center thickness of the second lens along the optical axis.

[0011] In some embodiments of this application, the projection optical system satisfies: -1.96≤f3G / d2m≤-0.80; where f3G is the focal length of the third lens of the projection optical system at the first wavelength, and d2m is the inner diameter of the image source side of the second spacer element.

[0012] In some embodiments of this application, the projection optical system satisfies: 1.23≤D2m / |R5|≤2.80; where D2m is the outer diameter of the image source side of the second spacer element, and R5 is the radius of curvature of the imaging side of the third lens.

[0013] In some embodiments of this application, the projection optical system satisfies: 3.95≤d0m / CT4≤10.39; where d0m is the inner diameter of the image source side of the lens barrel, and CT4 is the center thickness of the fourth lens on the optical axis.

[0014] In some embodiments of this application, the projection optical system satisfies: 0.64≤R1 / d0s≤1.85; where R1 is the radius of curvature of the imaging side of the first lens, and d0s is the inner diameter of the imaging side of the lens barrel.

[0015] In some embodiments of this application, the projection optical system satisfies: 4.65 < D3s / T34 < 7.20; where D3s is the outer diameter of the imaging side of the third spacer element, and T34 is the air gap between the third lens and the fourth lens on the optical axis.

[0016] In some embodiments of this application, the projection optical system satisfies: 1.82≤(CP1+CP2+CP3) / T23≤4.81; where CP1 is the maximum thickness of the first spacer element along the optical axis, CP2 is the maximum thickness of the second spacer element along the optical axis, CP3 is the maximum thickness of the third spacer element along the optical axis, and T23 is the air gap between the second lens and the third lens on the optical axis.

[0017] In some embodiments of this application, the projection optical system satisfies: 3.10≤L / (D0s-D0m)≤3.61; where L is the maximum height of the lens barrel, D0s is the outer diameter of the imaging side of the lens barrel, and D0m is the outer diameter of the image source side of the lens barrel.

[0018] In summary, under the condition that 1.05 < d3s / |R6| < 3.05, the projection optical system suffers from high eccentricity and tilt sensitivity during third lens formation, affecting the imaging quality of the optical system. Therefore, this application reduces the eccentricity and tilt sensitivity of the third lens during formation by constraining 1.43 ≤ EP23 / CT3 ≤ 2.70, thereby improving the imaging quality. When the lower limit of the condition is exceeded, the light rays in the edge field of view of the third lens become steeper, increasing the eccentricity and tilt sensitivity during formation, resulting in a lower MTF peak value for the entire field of view and poorer imaging quality. When the upper limit of the condition is exceeded, the light rays in the center field of view of the third lens become steeper, also increasing the eccentricity and tilt sensitivity during formation, leading to defocus curve divergence, more positive field curvature, and a lower MTF peak value for most fields of view, resulting in poorer imaging quality. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the parameters of a projection optical system according to one embodiment of this application;

[0020] Figure 2 This is a schematic diagram of the structure of a projection optical system according to one embodiment of this application;

[0021] Figure 3 yes Figure 2 A schematic diagram of the optical structure of the color combining prism assembly in the projection optics system shown.

[0022] Figure 4 This is a schematic diagram of the projection optical system according to Embodiment 1 of this application;

[0023] Figure 5 This is a schematic diagram of the projection optical system according to Embodiment 2 of this application;

[0024] Figure 6 This is a schematic diagram of the projection optical system according to Embodiment 3 of this application;

[0025] Figure 7A A schematic diagram of the astigmatism curves of the projection optical system according to Embodiment 1, Embodiment 2 and Embodiment 3 of this application at the first wavelength is shown.

[0026] Figure 7B A schematic diagram of the distortion curves of the projection optical system according to Embodiment 1, Embodiment 2 and Embodiment 3 of this application at the first wavelength is shown.

[0027] Figure 8A A schematic diagram of the astigmatism curves of the projection optical system according to Embodiment 1, Embodiment 2 and Embodiment 3 of this application at the second wavelength is shown.

[0028] Figure 8BA schematic diagram of the distortion curves of the projection optical system according to Embodiment 1, Embodiment 2 and Embodiment 3 of this application at the second wavelength is shown.

[0029] Figure 9A A schematic diagram of the astigmatism curves of the projection optical system according to Embodiment 1, Embodiment 2 and Embodiment 3 of this application at a third wavelength is shown.

[0030] Figure 9B A schematic diagram of the distortion curves of the projection optical system according to Embodiment 1, Embodiment 2 and Embodiment 3 of this application at a third wavelength is shown.

[0031] Figure 10 This is a schematic diagram of the projection optical system according to Embodiment 4 of this application;

[0032] Figure 11 This is a schematic diagram of the projection optical system according to Embodiment 5 of this application;

[0033] Figure 12 This is a schematic diagram of the projection optical system according to Embodiment Six of this application;

[0034] Figure 13A A schematic diagram of the astigmatism curves of the projection optical system according to Embodiments 4, 5 and 6 of this application at the first wavelength is shown.

[0035] Figure 13B A schematic diagram of the distortion curves of the projection optical system according to Embodiments 4, 5 and 6 of this application at the first wavelength is shown.

[0036] Figure 14A A schematic diagram of the astigmatism curves of the projection optical system according to Embodiments 4, 5 and 6 of this application at the second wavelength is shown.

[0037] Figure 14B A schematic diagram of the distortion curves of the projection optical system according to Embodiments 4, 5 and 6 of this application at the second wavelength is shown.

[0038] Figure 15A A schematic diagram of the astigmatism curves of the projection optical systems of Embodiments 4, 5 and 6 of this application at a third wavelength is shown.

[0039] Figure 15B A schematic diagram of the distortion curves of the projection optical system according to Embodiments 4, 5 and 6 of this application at a third wavelength is shown.

[0040] Figure 16 This is a schematic diagram of the projection optical system according to Embodiment Seven of this application;

[0041] Figure 17 This is a schematic diagram of the projection optical system according to Embodiment 8 of this application;

[0042] Figure 18 This is a schematic diagram of the projection optical system according to Embodiment Nine of this application;

[0043] Figure 19A A schematic diagram of the astigmatism curves of the projection optical system according to Embodiments 7, 8 and 9 of this application at the first wavelength is shown.

[0044] Figure 19B A schematic diagram of the distortion curves of the projection optical system according to Embodiments 7, 8 and 9 of this application at the first wavelength is shown.

[0045] Figure 20A A schematic diagram of the astigmatism curves of the projection optical system according to Embodiments 7, 8 and 9 of this application at the second wavelength is shown.

[0046] Figure 20B A schematic diagram of the distortion curves of the projection optical system according to Embodiments 7, 8 and 9 of this application at the second wavelength is shown.

[0047] Figure 21A A schematic diagram of the astigmatism curves of the projection optical systems of Embodiments 7, 8, and 9 according to this application at a third wavelength is shown.

[0048] Figure 21B A schematic diagram of the distortion curves of the projection optical system according to Embodiments 7, 8 and 9 of this application at a third wavelength is shown.

[0049] Figure 22 The MTF defocus curves of the projection optical system are shown when d3s / |R6|=2.2 and EP23 / CT3=2.39.

[0050] Figure 23 The MTF defocus curves of the projection optics system are shown when d3s / |R6|=2.2 and EP23 / CT3=1.20.

[0051] Figure 24 The MTF defocus curves of the projection optical system are shown when d3s / |R6|=2.2 and EP23 / CT3=3.00. Detailed Implementation

[0052] To better understand this application, various aspects of this application will be described in more detail with reference to the accompanying drawings. It should be understood that these detailed descriptions are merely illustrative of exemplary embodiments of this application and are not intended to limit the scope of this application in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0053] It should be noted that in this specification, the terms "first," "second," "third," etc., are used only to distinguish one feature from another and do not imply any limitation on the features. Therefore, without departing from the teachings of this application, the first lens discussed below may also be referred to as the second lens or the third lens.

[0054] In the accompanying drawings, the thickness, size, and shape of the lenses have been slightly exaggerated for ease of illustration. Specifically, the shapes of the spherical or aspherical surfaces shown in the drawings are illustrated by way of example. That is, the shapes of the spherical or aspherical surfaces are not limited to those shown in the drawings. The drawings are for illustrative purposes only and are not strictly to scale.

[0055] In this paper, the paraxial region refers to the area near the optical axis. If the lens surface is convex and its location is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and its location is not defined, it means that the lens surface is concave at least in the paraxial region. The surface shape in the paraxial region can be determined based on the sign of the R value (R refers to the radius of curvature of the paraxial region). Taking the imaging side as an example, when the R value is positive, it is determined to be convex, and when the R value is negative, it is determined to be concave; taking the image source side as an example, when the R value is positive, it is determined to be concave, and when the R value is negative, it is determined to be convex.

[0056] It should also be understood that the terms "comprising," "including," "having," "containing," and / or "comprising," when used in this specification, indicate the presence of the stated features, elements, and / or components, but do not exclude the presence or addition of one or more other features, elements, components, and / or combinations thereof. Furthermore, when expressions such as "at least one of..." appear after a list of listed features, they modify the entire list of features, not individual elements in the list. Additionally, when describing embodiments of this application, the word "may" is used to mean "one or more embodiments of this application." And the term "exemplary" is intended to refer to an example or illustration.

[0057] Unless otherwise specified, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms (e.g., those defined in common dictionaries) shall be interpreted as having a meaning consistent with their meaning in the context of the relevant art and shall not be interpreted in an idealized or overly formalized sense, unless expressly so specified herein.

[0058] It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other. The following embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of this application. It should be pointed out that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0059] Please see Figures 1 to 3 ,like Figure 1 and Figure 2 As shown, the projection optical system provided in this application includes a lens barrel P0 and a color combining prism assembly arranged sequentially from the imaging side to the image source side along the optical axis.

[0060] like Figure 2 As shown, the lens barrel P0 includes: a first lens E1 with positive optical power, whose imaging side and image source side are both convex; a second lens E2 with positive or negative optical power, whose image source side is concave; a third lens E3 with negative optical power; and a fourth lens E4 with positive or negative optical power, whose image source side is convex. A first spacer element P1 is disposed between the first lens E1 and the second lens E2, and the first spacer element P1 abuts against the image source side of the first lens E1. A second spacer element P2 is disposed between the second lens E2 and the third lens E3, and the second spacer element P2 abuts against the image source side of the second lens E2. A third spacer element P3 is disposed between the third lens E3 and the fourth lens E4, and the third spacer element P3 abuts against the image source side of the third lens E3.

[0061] like Figure 3As shown, the color-combining prism assembly includes a color-combining prism E5, a red light-emitting chip, a green light-emitting chip, and a blue light-emitting chip. The two diagonal surfaces of the color-combining prism E5 are respectively provided with a blue light bandpass filter Bf and a red light bandpass filter Rf. In the color-combining prism E5, the blue light bandpass filter Bf reflects red light incident on it and transmits blue and green light. The red light bandpass filter Rf reflects blue light incident on it and transmits red and green light. The green light-emitting chip is arranged perpendicular to the optical axis and located on the image source side of the color-combining prism E5. The red and blue light-emitting chips are arranged parallel to the optical axis, so that the light emitted by the red and blue light-emitting chips, after being reflected by the blue and red light bandpass filters Bf and Rf respectively, can be directed towards the image source side of the fourth lens E4.

[0062] The projection optical system satisfies: 1.05 < d3s / |R6| < 3.05; 1.43 ≤ EP23 / CT3 ≤ 2.70; where d3s is the inner diameter of the imaging side of the third spacer element P3, R6 is the radius of curvature of the image source side of the third lens E3, EP23 is the distance along the optical axis from the image source side of the second spacer element P2 to the imaging side of the third spacer element P3, and CT3 is the center thickness of the third lens E3 on the optical axis.

[0063] In summary, under the condition that 1.05 < d3s / |R6| < 3.05, the projection optical system suffers from high eccentricity and tilt sensitivity during the shaping of the third lens E3, which affects the imaging quality of the optical system. Therefore, this application reduces the eccentricity and tilt sensitivity of the third lens E3 during shaping by constraining 1.43 ≤ EP23 / CT3 ≤ 2.70, thereby improving the imaging quality.

[0064] Figure 22 The MTF defocus curves of the projection optical system are shown when d3s / |R6|=2.2 and EP23 / CT3=2.39. As can be seen from the figure, the peak MTF of the projection optical system is high in all fields of view, and the MTF defocus curves of different fields of view converge to the same value. This indicates that the optical performance of the projection optical system is good when the constraints 1.05<d3s / |R6|<3.05 and 1.43≤EP23 / CT3≤2.70 are met.

[0065] Figure 23The MTF defocus curves of the projection optical system are shown when d3s / |R6|=2.2 and EP23 / CT3=1.2. As can be seen from the figure, the peak MTF of the projection optical system is low in all fields of view, and the MTF defocus curves of different fields of view show a certain divergence. This indicates that when the projection optical system exceeds the lower limit of 1.05<d3s / |R6|<3.05; 1.43≤EP23 / CT3≤2.70, the light rays in the edge field of view of the third lens E3 become steeper, and the eccentricity and tilt sensitivity during shaping increase, resulting in poor image quality of the projection optical system.

[0066] Figure 24 The MTF defocus curves of the projection optical system are shown when d3s / |R6|=2.2 and EP23 / CT3=3.0. As can be seen from the figure, the MTF peak value is low in some fields of view of the projection optical system, and the MTF defocus curves in different fields of view show obvious divergence. This indicates that when the projection optical system exceeds the upper limit of 1.05<d3s / |R6|<3.05; 1.43≤EP23 / CT3≤2.70, the light rays in the central field of view of the third lens E3 become steeper, and the sensitivity to eccentricity and tilt during shaping also increases, resulting in the divergence of the defocus curve, the low MTF peak value in some fields of view, and the poor imaging quality of the projection optical system.

[0067] According to some embodiments of this application, the green light-emitting chip emits light in the wavelength range of 509nm~545nm, the red light-emitting chip emits light in the wavelength range of 615nm~655nm, and the blue light-emitting chip emits light in the wavelength range of 450nm~470nm. In one embodiment, the first wavelength of the light emitted by the green light-emitting chip is 527nm, the second wavelength of the light emitted by the red light-emitting chip is 635nm, and the third wavelength of the light emitted by the blue light-emitting chip is 460nm. In this way, by controlling the three different colored light sources to emit their respective required light wavelengths within a certain range, the three light waves are refracted through a prism group and passed through a lens to achieve a high-quality color image, making the projected image richer and clearer, thereby improving the user's visual experience.

[0068] According to some embodiments of this application, the projection optical system satisfies: 1.00 ≤ |f2R - f2B| / EP12 ≤ 3.48; where f2R is the focal length of the second lens E2 of the projection optical system at the second wavelength, f2B is the focal length of the second lens E2 of the projection optical system at the third wavelength, and EP12 is the distance along the optical axis from the image source side of the first spacer element P1 to the imaging side of the second spacer element P2. In this way, by controlling this condition within a certain range, the trajectory of light within the lens can be better controlled. Simultaneously, while ensuring better overall lens structure shaping, invalid light paths outside the aspherical edge are prevented from entering the optical system, reducing stray light generation and improving image quality.

[0069] According to some embodiments of this application, the projection optical system satisfies: 1.78 ≤ (D3m - d3m) / |f4R - f4B| ≤ 8.43; where D3m is the outer diameter of the image source side of the third spacer element P3, d3m is the inner diameter of the image source side of the third spacer element P3, f4R is the focal length of the fourth lens E4 of the projection optical system at the second wavelength, and f4B is the focal length of the fourth lens E4 of the projection optical system at the third wavelength. In this way, by controlling this conditional expression within a certain range, the surface profile of light rays at the edge of the effective diameter of the fourth lens E4 is controlled within a reasonable range. Furthermore, by controlling the inner and outer diameters of the third spacer element P3, the third spacer element P3 blocks excess light rays outside the effective diameter of the fourth lens E4, thereby reducing stray light generation and improving the overall image quality of the lens.

[0070] According to some embodiments of this application, the projection optical system satisfies: 3.55 ≤ d1s / CT1 ≤ 6.11; where d1s is the inner diameter of the imaging side of the first spacer element P1, and CT1 is the center thickness of the first lens E1 on the optical axis. In this way, by controlling the ratio of the inner diameter of the imaging side of the first spacer element P1 to the center thickness of the first lens E1 on the optical axis within a certain range, the mating length of the bearing surfaces of the first spacer element P1 and the first lens E1 can be kept within a reasonable range, avoiding the first lens E1 from tilting due to an excessively large or small bearing surface, thus improving the structural stability of the lens.

[0071] According to some embodiments of this application, the projection optical system satisfies: 2.17 ≤ f1G / EP01 ≤ 6.33; where f1G is the focal length of the first lens E1 at the first wavelength, and EP01 is the distance along the optical axis from the imaging side of the lens barrel P0 to the imaging side of the first spacer element P1. In this way, by controlling this condition within a certain range, on the one hand, the surface shape of the first lens E1 is controlled within a reasonable curvature range, improving manufacturing feasibility and avoiding ghosting problems; on the other hand, the center position of the imaging side of the first lens E1 does not protrude from the end face of the lens barrel P0, avoiding scratches on the lens during assembly, inspection, and transportation.

[0072] According to some embodiments of this application, the projection optical system satisfies: 0.30 < CP1 / CT2 < 1.65; where CP1 is the maximum thickness of the first spacer element P1 along the optical axis, and CT2 is the center thickness of the second lens E2 along the optical axis. In this way, by controlling this condition within a certain range, while ensuring the additivity of the second lens E2, the ghosting produced by the second lens E2 can be effectively improved, which is beneficial to improving the overall image quality of the lens.

[0073] According to some embodiments of this application, the projection optical system satisfies: -1.96 ≤ f3G / d2m ≤ -0.80; where f3G is the focal length of the third lens E3 of the projection optical system at the first wavelength, and d2m is the inner diameter of the image source side of the second spacer element P2. In this way, by controlling this condition within a certain range, the second spacer element P2 can effectively block stray light, improving image quality.

[0074] According to some embodiments of this application, the projection optical system satisfies: 3.95 ≤ d0m / CT4 ≤ 10.39; where d0m is the inner diameter of the image source side of the lens barrel P0, and CT4 is the center thickness of the fourth lens E4 on the optical axis. In this way, by controlling this condition within a certain range, on the one hand, the fourth lens E4 can be supported on the lens barrel P0 with sufficient length; on the other hand, all effective light rays entering through the prism can enter the lens optical system, while blocking light rays outside the effective light path, thereby improving image quality.

[0075] According to some embodiments of this application, the projection optical system satisfies: 0.64 ≤ R1 / d0s ≤ 1.85; where R1 is the radius of curvature of the imaging side of the first lens E1, and d0s is the inner diameter of the imaging side of the lens barrel P0. By controlling this condition within a certain range, the effective imaging light path projected by the entire optical system is not obstructed while ensuring the thickness of the front section of the lens barrel P0, thus maintaining a complete projected image plane and avoiding the risk of vignetting.

[0076] According to some embodiments of this application, the projection optical system satisfies: 4.65 < D3s / T34 < 7.20; where D3s is the outer diameter of the imaging side of the third spacer element P3, and T34 is the air gap between the third lens E3 and the fourth lens E4 on the optical axis. In this way, by controlling this conditional expression within a certain range, the distortion contribution of each field of view of the system is controlled within a reasonable range. Combined with adjusting the size of the air gap between the third lens E3 and the fourth lens E4, the thickness of the third spacer element P3 is also kept within the optimal processing range, reducing the thickness tolerance during the processing of the third spacer element P3 and improving the structural accuracy of the optical system.

[0077] According to some embodiments of this application, the projection optical system satisfies: 1.82 ≤ (CP1 + CP2 + CP3) / T23 ≤ 4.81; where CP1 is the maximum thickness of the first spacer element P1 along the optical axis, CP2 is the maximum thickness of the second spacer element P2 along the optical axis, CP3 is the maximum thickness of the third spacer element P3 along the optical axis, and T23 is the air gap between the second lens E2 and the third lens E3 on the optical axis. In this way, by controlling this condition within a certain range, on the one hand, the thickness of each spacer element is kept within a reasonable range, ensuring its fabrication feasibility; on the other hand, the ghosting caused by the air gap between the second lens E2 and the third lens E3 is reduced, while the overall structure becomes more compact and stable.

[0078] According to some embodiments of this application, the projection optical system satisfies: 3.10 ≤ L / (D0s-D0m) ≤ 3.61; where L is the maximum height of the lens barrel P0, D0s is the outer diameter of the imaging side of the lens barrel P0, and D0m is the outer diameter of the image source side of the lens barrel P0. In this way, by controlling this condition within a certain range, the overall size of the lens is kept within the design range, achieving miniaturization while also making the wall thickness of the lens barrel P0 more uniform and reasonable, improving molding quality and mass production yield.

[0079] According to another aspect of this application, a projection optical system is provided, including a lens barrel P0 and a color combining prism assembly arranged sequentially along the optical axis from the imaging side to the image source side; the lens barrel P0 includes: a first lens E1 with positive optical power, the imaging side being convex and the image source side being convex; a second lens E2 with positive or negative optical power, the image source side being concave; a third lens E3 with negative optical power; and a fourth lens E4 with positive or negative optical power, the image source side being convex; a first spacer element P1 is disposed between the first lens E1 and the second lens E2, and the first spacer element P1 abuts against the image source side of the first lens E1; a second spacer element P2 is disposed between the second lens E2 and the third lens E3, and the second spacer element P2 abuts against the image source side of the second lens E2; and a third spacer element P3 is disposed between the third lens E3 and the fourth lens E4, and the third spacer element P3 abuts against the third lens. The image source side of E3; the color combining prism assembly includes a color combining prism E5, a red light-emitting chip, a green light-emitting chip, and a blue light-emitting chip; the two diagonal surfaces of the color combining prism E5 are respectively provided with a blue light bandpass filter Bf and a red light bandpass filter Rf; the green light-emitting chip is arranged perpendicular to the optical axis, and the red light-emitting chip and the blue light-emitting chip are arranged parallel to the optical axis, so that the light emitted by the red light-emitting chip and the blue light-emitting chip passes through the blue light bandpass filter Bf and the red light bandpass filter Rf respectively. After being reflected by the red light bandpass filter Rf, the light can be directed toward the image source side of the fourth lens E4; the projection optical system satisfies: 1.05 < d3s / |R6| < 3.05; 1.23 ≤ D2m / |R5| ≤ 2.80; where d3s is the inner diameter of the imaging side of the third spacer element P3, R6 is the radius of curvature of the image source side of the third lens E3, D2m is the outer diameter of the image source side of the second spacer element P2, and R5 is the radius of curvature of the imaging side of the third lens E3.

[0080] In summary, by constraining the curvature radii of the imaging side and the image source side of the third lens E3 using the conditions 1.05<d3s / |R6|<3.05 and 1.23≤D2m / |R5|≤2.80, the surface shape and overall thickness of the third lens E3 can be made more uniform. While ensuring the outer diameter of the third lens E3, the outer diameter of the rear end of the lens barrel P0 is also controlled within the design range, which is beneficial to lens miniaturization.

[0081] It should be noted that those skilled in the art should understand that, without departing from the technical solutions claimed in this application, the number of spacers constituting the projection optical system can be changed to obtain the various results and advantages described in this specification, and this application does not specifically limit this. For example, the optical imaging lens may also include a number of spacers other than those described in the above embodiments, as needed.

[0082] The following describes in more detail, with reference to the accompanying drawings, some specific, but not limiting, embodiments of the above-described embodiments of this application. For ease of description, in the following embodiments, STO represents the surface of the aperture stop, S1 represents the imaging side of the first lens E1, S2 represents the image source side of the first lens E1, S3 represents the imaging side of the second lens E2, S4 represents the image source side of the second lens E2, S5 represents the imaging side of the third lens E3, S6 represents the image source side of the third lens E3, S7 represents the imaging side of the fourth lens E4, S8 represents the image source side of the fourth lens E4; S9 represents the imaging side of the color combining prism E5; S10 represents the image source side of the color combining prism E5; and S11 represents the image source surface of the green light-emitting chip.

[0083] Example 1

[0084] like Figure 2 , Figure 3 and Figure 4 As shown, in this embodiment, the projection optical system includes a lens barrel P0 and a color-combining prism assembly arranged sequentially from the imaging side to the image source side along the optical axis. The lens barrel P0 includes a first lens E1, a second lens E2, a third lens E3, and a fourth lens E4. The color-combining prism assembly includes a color-combining prism E5, a red light-emitting chip, a green light-emitting chip, and a blue light-emitting chip. The two diagonal surfaces of the color-combining prism E5 are respectively provided with a blue light bandpass filter Bf and a red light bandpass filter Rf. The green light-emitting chip is arranged perpendicular to the optical axis, and the red light-emitting chip and the blue light-emitting chip are arranged parallel to the optical axis, so that the light emitted by the red light-emitting chip and the blue light-emitting chip can be reflected by the blue light bandpass filter Bf and the red light bandpass filter Rf, respectively, and then directed towards the image source side of the fourth lens E4.

[0085] In this embodiment, the first lens E1 has positive optical power, and the imaging side and the image source side of the first lens E1 are convex; the second lens E2 has positive optical power, and the imaging side of the second lens E2 is convex and the image source side is concave; the third lens E3 has negative optical power, and the imaging side of the third lens E3 is convex and the image source side is concave; the fourth lens E4 has positive optical power, and the imaging side and the image source side of the fourth lens E4 are convex.

[0086] In this embodiment, the lens barrel P0 further includes: a first spacer element P1 disposed on the image source side of the first lens E1 and abutting against the image source side of the first lens E1; a second spacer element P2 disposed on the image source side of the second lens E2 and abutting against the image source side of the second lens E2; and a third spacer element P3 disposed on the image source side of the third lens E3 and abutting against the image source side of the third lens E3.

[0087] In addition, Table 1 shows the basic optical parameters of the projection optical system of Embodiment 1, where the units of radius of curvature and thickness / distance are millimeters (mm).

[0088] Table 1

[0089]

[0090] In this embodiment, the imaging side and image source side of any one of the first lens E1 to the fourth lens E4 are aspherical surfaces, and the surface shape x of each aspherical lens can be defined using, but is not limited to, the following aspherical formula:

[0091] ;

[0092] Where x is the distance vector from the vertex of the aspherical surface at a height h along the optical axis; c is the paraxial curvature of the aspherical surface, c = 1 / R (i.e., the paraxial curvature c is the reciprocal of the radius of curvature R in Table 1 above); k is the conic coefficient; Ai is the i-th order correction coefficient of the aspherical surface. Tables 2-1 and 2-2 below give the higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A18, and A20 that can be used for the aspherical mirrors S1 to S8 in Example 1.

[0093] Table 2-1

[0094]

[0095] Table 2-2

[0096]

[0097] In this embodiment, the refractive indices of the first lens E1 to the fourth lens E4 and the color combining prism E5 for light of different wavelengths are shown in Table 3 below.

[0098] Table 3

[0099]

[0100] Example 2

[0101] like Figure 2 , Figure 3 and Figure 5As shown, in this embodiment, the projection optical system includes a lens barrel P0 and a color-combining prism assembly arranged sequentially from the imaging side to the image source side along the optical axis. The lens barrel P0 includes a first lens E1, a second lens E2, a third lens E3, and a fourth lens E4. The color-combining prism assembly includes a color-combining prism E5, a red light-emitting chip, a green light-emitting chip, and a blue light-emitting chip. The two diagonal surfaces of the color-combining prism E5 are respectively provided with a blue light bandpass filter Bf and a red light bandpass filter Rf. The green light-emitting chip is arranged perpendicular to the optical axis, and the red and blue light-emitting chips are arranged parallel to the optical axis, so that the light emitted by the red and blue light-emitting chips can be reflected by the blue light bandpass filter Bf and the red light bandpass filter Rf, respectively, and then directed towards the image source side of the fourth lens E4.

[0102] It is worth noting that, compared with Embodiment 1 above, the projection optical system of Embodiment 2 has the same optical parameters. That is, the basic optical parameter table of the projection optical system of Embodiment 2 is the same as Table 1, the aspherical coefficient table is the same as Tables 2-1 and 2-2, and the refractive indices of the lens and color-combining prism E5 at different wavelengths are the same as Table 3. However, the projection optical system of Embodiment 2 has different structural parameters from the projection optical system of Embodiment 1 above. That is, the difference between Embodiment 2 and Embodiment 1 above is that the dimensional values ​​of some structural parameters of the lens barrel P0 and the spacer element in the projection optical system are different. The specific structural parameters are shown in Table 11 below.

[0103] Example 3

[0104] like Figure 2 , Figure 3 and Figure 6 As shown, in this embodiment, the projection optical system includes a lens barrel P0 and a color-combining prism assembly arranged sequentially from the imaging side to the image source side along the optical axis. The lens barrel P0 includes a first lens E1, a second lens E2, a third lens E3, and a fourth lens E4. The color-combining prism assembly includes a color-combining prism E5, a red light-emitting chip, a green light-emitting chip, and a blue light-emitting chip. The two diagonal surfaces of the color-combining prism E5 are respectively provided with a blue light bandpass filter Bf and a red light bandpass filter Rf. The green light-emitting chip is arranged perpendicular to the optical axis, and the red and blue light-emitting chips are arranged parallel to the optical axis, so that the light emitted by the red and blue light-emitting chips can be reflected by the blue light bandpass filter Bf and the red light bandpass filter Rf, respectively, and then directed towards the image source side of the fourth lens E4.

[0105] It is worth noting that, compared with Embodiment 1 above, the projection optical system of Embodiment 3 has the same optical parameters. That is, the basic optical parameter table of the projection optical system of Embodiment 3 is the same as Table 1, the aspherical coefficient table is the same as Tables 2-1 and 2-2, and the refractive indices of the lens and the color-combining prism E5 at different wavelengths are the same as Table 3. However, the projection optical system of Embodiment 3 has different structural parameters than the projection optical system of Embodiment 1 above. That is, the difference between Embodiment 3 and Embodiment 1 above is that the dimensional values ​​of some structural parameters of the lens barrel P0 and the spacer element in the projection optical system are different. The specific structural parameters are shown in Table 11 below.

[0106] In summary, the astigmatism curves of the projection optical systems in Embodiments 1, 2, and 3 at the first wavelength are as follows: Figure 7A As shown; the distortion curves of the projection optical system at the first wavelength in Embodiments 1, 2, and 3 are as follows. Figure 7B As shown; the astigmatism curves of the projection optical system at the second wavelength in Embodiments 1, 2, and 3 are as follows. Figure 8A As shown; the distortion curves of the projection optical system at the second wavelength in Embodiments 1, 2, and 3 are as follows. Figure 8B As shown; the astigmatism curves of the projection optical system in Embodiments 1, 2, and 3 at the third wavelength are as follows. Figure 9A As shown; the distortion curves of the projection optical system in Embodiments 1, 2, and 3 at the third wavelength are as follows. Figure 9B As shown. The astigmatism curves above represent the curvature of the meridional image plane and the sagittal image plane, while the distortion curve represents the degree of deformation in the actual image. According to... Figures 7A to 9B It can be seen that the projection optical systems in Embodiment 1, Embodiment 2 and Embodiment 3 can all achieve good imaging quality.

[0107] Example 4

[0108] like Figure 2 , Figure 3 and Figure 10As shown, in this embodiment, the projection optical system includes a lens barrel P0 and a color-combining prism assembly arranged sequentially from the imaging side to the image source side along the optical axis. The lens barrel P0 includes a first lens E1, a second lens E2, a third lens E3, and a fourth lens E4. The color-combining prism assembly includes a color-combining prism E5, a red light-emitting chip, a green light-emitting chip, and a blue light-emitting chip. The two diagonal surfaces of the color-combining prism E5 are respectively provided with a blue light bandpass filter Bf and a red light bandpass filter Rf. The green light-emitting chip is arranged perpendicular to the optical axis, and the red and blue light-emitting chips are arranged parallel to the optical axis, so that the light emitted by the red and blue light-emitting chips can be reflected by the blue light bandpass filter Bf and the red light bandpass filter Rf, respectively, and then directed towards the image source side of the fourth lens E4.

[0109] In this embodiment, the first lens E1 has positive optical power, and the imaging side and the image source side of the first lens E1 are convex; the second lens E2 has positive optical power, and the imaging side of the second lens E2 is convex and the image source side is concave; the third lens E3 has negative optical power, and the imaging side of the third lens E3 is convex and the image source side is concave; the fourth lens E4 has positive optical power, and the imaging side and the image source side of the fourth lens E4 are convex.

[0110] In this embodiment, the lens barrel P0 further includes: a first spacer element P1 disposed on the image source side of the first lens E1 and abutting against the image source side of the first lens E1; a second spacer element P2 disposed on the image source side of the second lens E2 and abutting against the image source side of the second lens E2; and a third spacer element P3 disposed on the image source side of the third lens E3 and abutting against the image source side of the third lens E3.

[0111] In addition, Table 4 shows the basic optical parameters of the projection optical system of Embodiment 4, where the units of radius of curvature and thickness / distance are millimeters (mm).

[0112] Table 4

[0113]

[0114] In this embodiment, the imaging side and the image source side of any one of the first lens E1 to the fourth lens E4 are aspherical, and the surface shape x of each aspherical lens can be defined by, but is not limited to, the aspherical formula in Embodiment 1.

[0115] Tables 5-1 and 5-2 below give the higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A18, and A20 that can be used for each aspherical mirror S1 to S8 in Example 4.

[0116] Table 5-1

[0117]

[0118] Table 5-2

[0119]

[0120] In this embodiment, the refractive indices of the first lens E1 to the fourth lens E4 and the color combining prism E5 for light of different wavelengths are shown in Table 6 below.

[0121] Table 6

[0122]

[0123] Example 5

[0124] like Figure 2 , Figure 3 and Figure 11 As shown, in this embodiment, the projection optical system includes a lens barrel P0 and a color-combining prism assembly arranged sequentially from the imaging side to the image source side along the optical axis. The lens barrel P0 includes a first lens E1, a second lens E2, a third lens E3, and a fourth lens E4. The color-combining prism assembly includes a color-combining prism E5, a red light-emitting chip, a green light-emitting chip, and a blue light-emitting chip. The two diagonal surfaces of the color-combining prism E5 are respectively provided with a blue light bandpass filter Bf and a red light bandpass filter Rf. The green light-emitting chip is arranged perpendicular to the optical axis, and the red and blue light-emitting chips are arranged parallel to the optical axis, so that the light emitted by the red and blue light-emitting chips can be reflected by the blue light bandpass filter Bf and the red light bandpass filter Rf, respectively, and then directed towards the image source side of the fourth lens E4.

[0125] It is worth noting that, compared with Embodiment 4 above, the projection optical system of Embodiment 5 has the same optical parameters. That is, the basic optical parameter table of the projection optical system of Embodiment 5 is the same as Table 4, the aspherical coefficient table is the same as Tables 5-1 and 5-2, and the refractive index of the lens and the color-combining prism E5 at different wavelengths is the same as Table 6. However, the projection optical system of Embodiment 5 has different structural parameters from the projection optical system of Embodiment 4 above. That is, the difference between Embodiment 5 and Embodiment 4 above is that the dimensional values ​​of some structural parameters of the lens barrel P0 and the spacer element in the projection optical system are different. The specific structural parameters are shown in Table 11 below.

[0126] Example 6

[0127] like Figure 2 , Figure 3 and Figure 12As shown, in this embodiment, the projection optical system includes a lens barrel P0 and a color-combining prism assembly arranged sequentially from the imaging side to the image source side along the optical axis. The lens barrel P0 includes a first lens E1, a second lens E2, a third lens E3, and a fourth lens E4. The color-combining prism assembly includes a color-combining prism E5, a red light-emitting chip, a green light-emitting chip, and a blue light-emitting chip. The two diagonal surfaces of the color-combining prism E5 are respectively provided with a blue light bandpass filter Bf and a red light bandpass filter Rf. The green light-emitting chip is arranged perpendicular to the optical axis, and the red and blue light-emitting chips are arranged parallel to the optical axis, so that the light emitted by the red and blue light-emitting chips can be reflected by the blue light bandpass filter Bf and the red light bandpass filter Rf, respectively, and then directed towards the image source side of the fourth lens E4.

[0128] It is worth noting that, compared with Embodiment 4 above, the projection optical system of Embodiment 6 has the same optical parameters. That is, the basic optical parameter table of the projection optical system of Embodiment 6 is the same as Table 4, the aspherical coefficient table is the same as Tables 5-1 and 5-2, and the refractive indices of the lens and the color-combining prism E5 at different wavelengths are the same as Table 6. However, the projection optical system of Embodiment 6 has different structural parameters from the projection optical system of Embodiment 4 above. That is, the difference between Embodiment 6 and Embodiment 4 above is that the dimensional values ​​of some structural parameters of the lens barrel P0 and the spacer element in the projection optical system are different. The specific structural parameters are shown in Table 11 below.

[0129] In summary, the astigmatism curves of the projection optical systems in Examples 4, 5, and 6 at the first wavelength are as follows: Figure 13A As shown; the distortion curves of the projection optical system at the first wavelength in Examples 4, 5, and 6 are as follows. Figure 13B As shown; the astigmatism curves of the projection optical system at the second wavelength in Examples 4, 5, and 6 are as follows. Figure 14A As shown; the distortion curves of the projection optical system at the second wavelength in Examples 4, 5, and 6 are as follows. Figure 14B As shown; the astigmatism curves of the projection optical system in Examples 4, 5, and 6 at the third wavelength are as follows. Figure 15A As shown; the distortion curves of the projection optical system in Examples 4, 5, and 6 at the third wavelength are as follows. Figure 15B As shown. The astigmatism curves above represent the curvature of the meridional image plane and the sagittal image plane, while the distortion curve represents the degree of deformation in the actual image. According to... Figures 13A to 15B It can be seen that the projection optical systems in Embodiments 4, 5 and 6 can all achieve good imaging quality.

[0130] Example 7

[0131] like Figure 2, Figure 3 and Figure 16 As shown, in this embodiment, the projection optical system includes a lens barrel P0 and a color-combining prism assembly arranged sequentially from the imaging side to the image source side along the optical axis. The lens barrel P0 includes a first lens E1, a second lens E2, a third lens E3, and a fourth lens E4. The color-combining prism assembly includes a color-combining prism E5, a red light-emitting chip, a green light-emitting chip, and a blue light-emitting chip. The two diagonal surfaces of the color-combining prism E5 are respectively provided with a blue light bandpass filter Bf and a red light bandpass filter Rf. The green light-emitting chip is perpendicular to the optical axis, and the red and blue light-emitting chips are arranged parallel to the optical axis, so that the light emitted by the red and blue light-emitting chips can be reflected by the blue light bandpass filter Bf and the red light bandpass filter Rf, respectively, and then directed towards the image source side of the fourth lens E4.

[0132] In this embodiment, the first lens E1 has positive optical power, and the imaging side and the image source side of the first lens E1 are convex; the second lens E2 has negative optical power, and the imaging side and the image source side of the second lens E2 are concave; the third lens E3 has negative optical power, and the imaging side of the third lens E3 is concave and the image source side is convex; the fourth lens E4 has negative optical power, and the imaging side of the fourth lens E4 is concave and the image source side is convex.

[0133] In this embodiment, the lens barrel P0 further includes: a first spacer element P1 disposed on the image source side of the first lens E1 and abutting against the image source side of the first lens E1; a second spacer element P2 disposed on the image source side of the second lens E2 and abutting against the image source side of the second lens E2; and a third spacer element P3 disposed on the image source side of the third lens E3 and abutting against the image source side of the third lens E3.

[0134] In addition, Table 7 shows the basic optical parameters of the projection optical system of Embodiment 7, where the units of radius of curvature and thickness / distance are millimeters (mm).

[0135] Table 7

[0136]

[0137] In this embodiment, the imaging side and the image source side of any one of the first lens E1 to the fourth lens E4 are aspherical, and the surface shape x of each aspherical lens can be defined by, but is not limited to, the aspherical formula in Embodiment 1.

[0138] Tables 8-1 and 8-2 below give the higher-order term coefficients A4, A6, A8, A10, A12, A14, A16, A18, and A20 that can be used for each aspherical mirror S1 to S8 in Example 7.

[0139] Table 8-1

[0140]

[0141] Table 8-2

[0142]

[0143] In this embodiment, the refractive indices of the first lens E1 to the fourth lens E4 and the color combining prism E5 for light of different wavelengths are shown in Table 9 below.

[0144] Table 9

[0145]

[0146] Example 8

[0147] like Figure 2 , Figure 3 and Figure 17 As shown, in this embodiment, the projection optical system includes a lens barrel P0 and a color-combining prism assembly arranged sequentially from the imaging side to the image source side along the optical axis. The lens barrel P0 includes a first lens E1, a second lens E2, a third lens E3, and a fourth lens E4. The color-combining prism assembly includes a color-combining prism E5, a red light-emitting chip, a green light-emitting chip, and a blue light-emitting chip. The two diagonal surfaces of the color-combining prism E5 are respectively provided with a blue light bandpass filter Bf and a red light bandpass filter Rf. The green light-emitting chip is arranged perpendicular to the optical axis, and the red and blue light-emitting chips are arranged parallel to the optical axis, so that the light emitted by the red and blue light-emitting chips can be reflected by the blue light bandpass filter Bf and the red light bandpass filter Rf, respectively, and then directed towards the image source side of the fourth lens E4.

[0148] It is worth noting that, compared with Embodiment 7 above, the projection optical system of Embodiment 8 has the same optical parameters. That is, the basic optical parameter table of the projection optical system of Embodiment 8 is the same as Table 7, the aspherical coefficient table is the same as Tables 8-1 and 8-2, and the refractive indices of the lens and the color-combining prism E5 at different wavelengths are the same as Table 9. However, the projection optical system of Embodiment 8 has different structural parameters than the projection optical system of Embodiment 7 above. That is, the difference between Embodiment 8 and Embodiment 7 is that the dimensional values ​​of some structural parameters of the lens barrel P0 and the spacer element in the projection optical system are different. The specific structural parameters are shown in Table 11 below.

[0149] Example 9

[0150] like Figure 2 , Figure 3 and Figure 18As shown, in this embodiment, the projection optical system includes a lens barrel P0 and a color-combining prism assembly arranged sequentially from the imaging side to the image source side along the optical axis. The lens barrel P0 includes a first lens E1, a second lens E2, a third lens E3, and a fourth lens E4. The color-combining prism assembly includes a color-combining prism E5, a red light-emitting chip, a green light-emitting chip, and a blue light-emitting chip. The two diagonal surfaces of the color-combining prism E5 are respectively provided with a blue light bandpass filter Bf and a red light bandpass filter Rf. The green light-emitting chip is arranged perpendicular to the optical axis, and the red and blue light-emitting chips are arranged parallel to the optical axis, so that the light emitted by the red and blue light-emitting chips can be reflected by the blue light bandpass filter Bf and the red light bandpass filter Rf, respectively, and then directed towards the image source side of the fourth lens E4.

[0151] It is worth noting that, compared with Embodiment 7 above, the projection optical system of Embodiment 9 has the same optical parameters. That is, the basic optical parameter table of the projection optical system of Embodiment 9 is the same as Table 7, the aspherical coefficient table is the same as Tables 8-1 and 8-2, and the refractive indices of the lens and the color-combining prism E5 at different wavelengths are the same as Table 9. However, the projection optical system of Embodiment 9 has different structural parameters than the projection optical system of Embodiment 7 above. That is, the difference between Embodiment 9 and Embodiment 7 is that the dimensional values ​​of some structural parameters of the lens barrel P0 and the spacer element in the projection optical system are different. The specific structural parameters are shown in Table 11 below.

[0152] In summary, the astigmatism curves of the projection optical systems in Examples 7, 8, and 9 at the first wavelength are as follows: Figure 19A As shown; the distortion curves of the projection optical system at the first wavelength in Examples 7, 8, and 9 are as follows. Figure 19B As shown; the astigmatism curves of the projection optical system at the second wavelength in Examples 7, 8, and 9 are as follows. Figure 20A As shown; the distortion curves of the projection optical system at the second wavelength in Examples 7, 8, and 9 are as follows. Figure 20B As shown; the astigmatism curves of the projection optical system in Examples 7, 8, and 9 at the third wavelength are as follows. Figure 21A As shown; the distortion curves of the projection optical system in Examples 7, 8, and 9 at the third wavelength are as follows. Figure 21B As shown. The astigmatism curves above represent the curvature of the meridional image plane and the sagittal image plane, while the distortion curve represents the degree of deformation in the actual image. According to... Figures 19A to 21B It can be seen that the projection optical systems in Embodiments 7, 8 and 9 can all achieve good imaging quality.

[0153] In summary, in Embodiments 1 to 9, the focal lengths f1G, f1R, and f1B of the first lens E1 at the first wavelength, the second wavelength, and the third wavelength; the focal lengths f2G, f2R, and f2B of the second lens E2 at the first wavelength, the second wavelength, and the third wavelength; the focal lengths f3G, f3R, and f3B of the third lens E3 at the first wavelength, the second wavelength, and the third wavelength; and the focal lengths f4G, f4R, and f4B of the fourth lens E4 at the first wavelength, the second wavelength, and the third wavelength are shown in Table 10 below.

[0154] Table 10

[0155]

[0156] Furthermore, the structural parameters of the projection optical system in Examples 1 to 9 are shown in Table 11.

[0157] Table 11

[0158]

[0159] The parameters in Table 11 are explained as follows: d1s represents the inner diameter of the imaging side of the first spacer element P1, d2m is the inner diameter of the image source side of the second spacer element P2, D2m is the outer diameter of the image source side of the second spacer element P2, d3s is the inner diameter of the imaging side of the third spacer element P3, d3m is the inner diameter of the image source side of the third spacer element P3, D3s is the outer diameter of the imaging side of the third spacer element P3, D3m is the outer diameter of the image source side of the third spacer element P3, d0s is the inner diameter of the imaging side of the lens barrel P0, d0m is the inner diameter of the image source side of the lens barrel P0, D0s is the outer diameter of the imaging side of the lens barrel P0, D0m is the outer diameter of the imaging side of the lens barrel P0, D0m is the inner diameter of the image source side of the lens barrel P0. EP01 is the outer diameter of the image source side of the lens barrel P0, CP1 is the distance from the imaging side of the lens barrel P0 to the imaging side of the first spacer element P1 along the optical axis, EP12 is the distance from the image source side of the first spacer element P1 to the imaging side of the second spacer element P2 along the optical axis, CP2 is the maximum thickness of the second spacer element P2 along the optical axis, EP23 is the distance from the image source side of the second spacer element P2 to the imaging side of the third spacer element P3 along the optical axis, CP3 is the maximum thickness of the third spacer element P3 along the optical axis, and L is the maximum height of the lens barrel P0.

[0160] In summary, the projection optical systems in Examples 1 to 9 satisfy the relationships shown in Table 12 below.

[0161] Table 12

[0162]

[0163] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0164] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A projection optical system, characterized in that, It includes a lens tube and a color-combining prism assembly arranged sequentially from the imaging side to the image source side along the optical axis; The lens barrel includes: a first lens with positive optical power, the imaging side of which is convex and the image source side of which is convex; a second lens with positive or negative optical power, the image source side of which is concave; a third lens with negative optical power; and a fourth lens with positive or negative optical power, the image source side of which is convex. A first spacer element is provided between the first lens and the second lens, and the first spacer element abuts against the image source side of the first lens; A second spacer element is provided between the second lens and the third lens, and the second spacer element abuts against the image source side of the second lens; A third spacer element is provided between the third lens and the fourth lens, and the third spacer element abuts against the image source side of the third lens; The color-combining prism assembly includes a color-combining prism, a red light-emitting chip, a green light-emitting chip, and a blue light-emitting chip; the two diagonal faces of the color-combining prism are respectively provided with a blue light bandpass filter and a red light bandpass filter; the green light-emitting chip is arranged perpendicular to the optical axis, and the red light-emitting chip and the blue light-emitting chip are arranged parallel to the optical axis, so that the light emitted by the red light-emitting chip and the blue light-emitting chip can be reflected by the blue light bandpass filter and the red light bandpass filter respectively and then directed to the image source side of the fourth lens; The projection optical system satisfies: 1.05 < d3s / |R6| < 3.05; 1.43 ≤ EP23 / CT3 ≤ 2.70; and 4.65 < D3s / T34 < 7.20; where d3s is the inner diameter of the imaging side of the third spacer element, R6 is the radius of curvature of the image source side of the third lens, EP23 is the distance along the optical axis from the image source side of the second spacer element to the imaging side of the third spacer element, CT3 is the center thickness of the third lens on the optical axis, D3s is the outer diameter of the imaging side of the third spacer element, and T34 is the air gap between the third lens and the fourth lens on the optical axis.

2. The projection optical system according to claim 1, characterized in that, The green light-emitting chip emits light in the wavelength range of 509nm to 545nm, the red light-emitting chip emits light in the wavelength range of 615nm to 655nm, and the blue light-emitting chip emits light in the wavelength range of 450nm to 470nm.

3. The projection optical system according to claim 2, characterized in that, The green light-emitting chip emits light at a first wavelength of 527nm, the red light-emitting chip emits light at a second wavelength of 635nm, and the blue light-emitting chip emits light at a third wavelength of 460nm.

4. The projection optical system according to claim 3, characterized in that, The projection optical system satisfies: 1.00≤|f2R-f2B| / EP12≤3.48; where f2R is the focal length of the second lens of the projection optical system at the second wavelength, f2B is the focal length of the second lens of the projection optical system at the third wavelength, and EP12 is the distance along the optical axis from the image source side of the first spacer element to the imaging side of the second spacer element.

5. The projection optical system according to claim 3, characterized in that, The projection optical system satisfies: 1.78≤(D3m-d3m) / |f4R-f4B|≤8.43; where D3m is the outer diameter of the image source side of the third spacer element, d3m is the inner diameter of the image source side of the third spacer element, f4R is the focal length of the fourth lens of the projection optical system at the second wavelength, and f4B is the focal length of the fourth lens of the projection optical system at the third wavelength.

6. The projection optical system according to claim 1, characterized in that, The projection optical system satisfies: 3.55≤d1s / CT1≤6.11; where d1s is the inner diameter of the imaging side of the first spacer element, and CT1 is the center thickness of the first lens on the optical axis.

7. The projection optical system according to claim 3, characterized in that, The projection optical system satisfies: 2.17≤f1G / EP01≤6.33; where f1G is the focal length of the first lens of the projection optical system at the first wavelength, and EP01 is the distance along the optical axis from the imaging side of the lens barrel to the imaging side of the first spacer element.

8. The projection optical system according to claim 1, characterized in that, The projection optical system satisfies: 0.30 < CP1 / CT2 < 1.65; where CP1 is the maximum thickness of the first spacer element along the optical axis, and CT2 is the center thickness of the second lens along the optical axis.

9. The projection optical system according to claim 3, characterized in that, The projection optical system satisfies: -1.96≤f3G / d2m≤-0.80; where f3G is the focal length of the third lens of the projection optical system at the first wavelength, and d2m is the inner diameter of the image source side of the second spacer element.

10. The projection optical system according to claim 1, characterized in that, The projection optical system satisfies: 1.23≤D2m / |R5|≤2.80; where D2m is the outer diameter of the image source side of the second spacer element, and R5 is the radius of curvature of the imaging side of the third lens.

11. The projection optical system according to claim 1, characterized in that, The projection optical system satisfies: 3.95≤d0m / CT4≤10.39; where d0m is the inner diameter of the side of the image source of the lens barrel, and CT4 is the center thickness of the fourth lens on the optical axis.

12. The projection optical system according to claim 1, characterized in that, The projection optical system satisfies: 0.64≤R1 / d0s≤1.85; where R1 is the radius of curvature of the imaging side of the first lens, and d0s is the inner diameter of the imaging side of the lens barrel.

13. The projection optical system according to claim 1, characterized in that, The projection optical system satisfies: 1.82≤(CP1+CP2+CP3) / T23≤4.81; where CP1 is the maximum thickness of the first spacer element along the optical axis, CP2 is the maximum thickness of the second spacer element along the optical axis, CP3 is the maximum thickness of the third spacer element along the optical axis, and T23 is the air gap between the second lens and the third lens on the optical axis.

14. The projection optical system according to claim 1, characterized in that, The projection optical system satisfies: 3.10≤L / (D0s-D0m)≤3.61; where L is the maximum height of the lens barrel, D0s is the outer diameter of the imaging side of the lens barrel, and D0m is the outer diameter of the image source side of the lens barrel.

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