Projection optical system

Abstract

The application provides a projection optical system, comprising a lens barrel and a color combining prism assembly arranged in sequence from an imaging side to an image source side along an optical axis direction; the lens barrel contains a lens group and a spacing assembly; the lens group comprises first, second, third and fourth lenses arranged in sequence from the imaging side to the image source side along the optical axis direction; the spacing assembly comprises first, second and third spacing elements; the color combining prism assembly comprises a color combining prism, red, green and blue light emitting chips; two diagonal surfaces of the color combining prism are respectively provided with blue light and red light band-pass filter films; the green light emitting chip is arranged perpendicularly to the optical axis, and the red light emitting chip and the blue light emitting chip are arranged parallel to the optical axis; the projection optical system further satisfies: 0.90<(CT1+CT2) / CP1<1.65; 4.90<d2m / (T23+CT3)≤7.30; and 5.50<d3s / T34<9.80.

Description

Technical Field

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

[0002] Projection optical lenses are the core optical components in projection display devices. Their function is to accurately project the information carried by the image source onto the screen in a way that is high-brightness, high-definition, and low-distortion. With the rapid development of head-mounted devices, the market has placed increasingly stringent demands on projection optical systems: smaller and lighter size to meet wearing comfort, a wider field of view (FOV) to enhance the immersive experience, higher optical efficiency and resolution to achieve high-quality imaging, while also strictly controlling costs.

[0003] Driven by miniaturization, large field of view, and high efficiency, and especially to meet the stringent geometric space and weight constraints of head-mounted devices on compact optical systems, the design difficulty of projection systems has increased significantly. Among these, the solution of directly integrating RGB three-primary-color light sources using color-combining prisms has become an important technical route due to its compactness and potential for high light-efficiency integration.

[0004] However, because the color combining prism assembly contains complex coating interfaces and multiple light sources, light is repeatedly refracted, transmitted and reflected within the prism. This can easily generate unexpected reflections and diffuse light paths on the optical surfaces and mechanical support structures inside the lens barrel. If these harmful stray lights are not effectively blocked and suppressed, they will eventually shine onto the imaging screen, forming clusters of scattered stray light, causing a decrease in image saturation, a deterioration in contrast, and the appearance of light spots or fogging, which seriously damages image quality and viewing experience. Summary of the Invention

[0005] One advantage of this application is that it provides a projection optical system that can significantly reduce stray light spots, thereby improving the optical performance of the projection optical system.

[0006] 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 houses a lens group and a spacer assembly; the lens group includes, arranged sequentially along the optical axis from the imaging side to the image source side: a first lens with positive optical power, whose imaging side is concave and image source side is convex; a second lens with optical power, whose imaging side is convex and image source side is concave; a third lens with negative optical power, whose image source side is concave; and a fourth lens with positive optical power, whose imaging side is convex and image source side is concave. The image source side is convex; the spacing assembly includes a first spacing element placed between the first lens and the second lens and in contact with the image source side of the first lens; a second spacing element placed between the second lens and the third lens and in contact with the image source side of the second lens; and a third spacing element placed between the third lens and the fourth lens and in contact with 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 The system includes a blue light bandpass filter and a red light bandpass filter. The green light-emitting chip is positioned perpendicular to the optical axis, while the red and blue light-emitting chips are positioned parallel to the optical axis. This allows the light emitted from the red and blue light-emitting chips to be reflected by the blue and red light bandpass filters, respectively, before being directed towards the image source side of the fourth lens. The projection optical system also satisfies the following conditions: 0.90 < (CT1 + CT2) / CP1 < 1.65; 4.90 < d2m / (T23 + CT3) ≤ 7.30; and 5.50 < d3s / T34 < 9.80; where CT1 is the center thickness of the first lens on the optical axis, CT2 is the center thickness of the second lens on the optical axis, CP1 is the maximum thickness of the first spacer element along the optical axis, d2m is the inner diameter of the image source side of the second spacer element, T23 is the air gap between the second lens and the third lens on the optical axis, CT3 is the center thickness of the third lens on the optical axis, d3s is the inner 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.

[0007] In some embodiments of this application, the green light-emitting chip emits light in the wavelength range of 515nm to 545nm, the red light-emitting chip emits light in the wavelength range of 619nm to 636nm, and the blue light-emitting chip emits light in the wavelength range of 450nm to 470nm.

[0008] In some embodiments of this application, the green light-emitting chip emits light at a first wavelength of 530 nm, the red light-emitting chip emits light at a second wavelength of 627 nm, and the blue light-emitting chip emits light at a third wavelength of 460 nm.

[0009] In some embodiments of this application, the projection optical system satisfies 0.35≤(D1m-d1m) / |f2R-f2B|<3.15; where D1m is the outer diameter of the image source side of the first spacer element, d1m is the inner diameter of the image source side of the first spacer element, f2R is the focal length of the second lens of the projection optical system at the second wavelength, and f2B is the focal length of the second lens of the projection optical system at the third wavelength.

[0010] In some embodiments of this application, the projection optical system satisfies: 1.75 < L / (EP01+CP1) ≤ 2.35; where L is the maximum height of the lens barrel, 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, and CP1 is the maximum thickness of the first spacer element along the optical axis.

[0011] In some embodiments of this application, the projection optical system satisfies: 4.15 < (f1G + f1R + f1B) / d0s < 6.50; where f1G is the focal length of the first lens of the projection optical system at the first wavelength, f1R is the focal length of the first lens of the projection optical system at the second wavelength, f1B is the focal length of the first lens of the projection optical system at the third wavelength, and d0s is the inner diameter of the imaging side of the lens barrel.

[0012] In some embodiments of this application, the projection optical system satisfies: 4.90mm < d1s × (R1 / R2) ≤ 6.00mm; where d1s is the inner diameter of the imaging side of the first spacer element, R1 is the radius of curvature of the imaging side of the first lens, and R2 is the radius of curvature of the image source side of the first lens.

[0013] In some embodiments of this application, the projection optical system satisfies: -7.80 < EP23 / (f3R-f3B) ≤ -3.45; where 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, f3R is the focal length of the third lens of the projection optical system at the second wavelength, and f3B is the focal length of the third lens of the projection optical system at the third wavelength.

[0014] In some embodiments of this application, the projection optical system satisfies: 3.20 < d3m / CT4 ≤ 3.65; where d3m is the inner diameter of the image source side of the third spacer element, and CT4 is the center thickness of the fourth lens on the optical axis.

[0015] In some embodiments of this application, the projection optical system satisfies: 1.15 < R4 / (D2s-d2s) < 4.85; where R4 is the radius of curvature of the image source side of the second lens, D2s is the outer diameter of the imaging side of the second spacer element, and d2s is the inner diameter of the imaging side of the second spacer element.

[0016] In some embodiments of this application, the projection optical system satisfies: 1.40 < d0m / f4G < 1.85; where d0m is the inner diameter of the image source side of the lens barrel, and f4G is the focal length of the fourth lens of the projection optical system at the first wavelength.

[0017] In some embodiments of this application, the projection optical system satisfies: 3.00 < R3 / EP12 ≤ 9.25; where R3 is the radius of curvature of the imaging side of the second lens, 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.

[0018] In some embodiments of this application, the projection optical system satisfies: -2.15 < D3s / f3G < -1.25; where D3s is the outer diameter of the imaging side of the third spacer element, and f3G is the focal length of the third lens of the projection optical system at the first wavelength.

[0019] In some embodiments of this application, the projection optical system satisfies: 2.60 < TD / (CP1+CP2+CP3) < 3.20; where TD is the distance on the optical axis from the imaging side of the first lens to the image source side of the fourth lens, 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, and CP3 is the maximum thickness of the third spacer element along the optical axis.

[0020] In some embodiments of this application, the projection optical system satisfies: 2.80 < fR / (D0s-d0s) < 6.30; where fR is the system focal length of the projection optical system at the second wavelength, D0s is the outer diameter of the imaging side of the lens barrel, and d0s is the inner diameter of the imaging side of the lens barrel.

[0021] In some embodiments of this application, the projection optical system satisfies: -1.95 < D0m / R8 < -1.45; where D0m is the outer diameter of the image source side of the lens barrel, and R8 is the radius of curvature of the image source side of the fourth lens.

[0022] In summary, under the condition of 0.90 < (CT1+CT2) / CP1 < 1.65, stray light problems are prone to occur between the second and fourth lenses in the projection optical system. Therefore, this application optimizes the optical path blocking effect and eliminates obvious stray light by reasonably designing the relative position and size of the second and third spacer elements by constraining the ranges of 4.91 ≤ d2m / (T23+CT3) ≤ 7.30 and 5.50 < d3s / T34 < 9.80. When the lower limits of d2m / (T23+CT3) and d3s / T34 are exceeded, the size of the second and third spacer elements is too small or the spacing is too wide, resulting in insufficient optical path blocking and the generation of clustered stray light. When the upper limits of d2m / (T23+CT3) and d3s / T34 are exceeded, the size of the second and third spacer elements is too large or the spacing is insufficient, resulting in excessive optical path blocking, affecting the effective light flux, and generating ring stray light. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structural parameters of a projection optical system according to one embodiment of this application;

[0024] Figure 2 This is a schematic diagram of the structure of a projection optical system according to one embodiment of this application;

[0025] Figure 3 This is a schematic diagram of the structure of a color-combining prism assembly according to one embodiment of this application;

[0026] Figure 4 This is a schematic diagram of the projection optical system according to Embodiment 1 of this application;

[0027] Figure 5 This is a schematic diagram of the projection optical system according to Embodiment 2 of this application;

[0028] Figure 6 This is a schematic diagram of the projection optical system according to Embodiment 3 of this application;

[0029] 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.

[0030] 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.

[0031] Figure 7C 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.

[0032] Figure 7D 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 second wavelength is shown.

[0033] Figure 7E 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.

[0034] Figure 7F 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.

[0035] Figure 8 This is a schematic diagram of the projection optical system according to Embodiment 4 of this application;

[0036] Figure 9 This is a schematic diagram of the projection optical system according to Embodiment 5 of this application;

[0037] Figure 10 This is a schematic diagram of the projection optical system according to Embodiment Six of this application;

[0038] Figure 11A 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.

[0039] Figure 11B 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.

[0040] Figure 11C 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.

[0041] Figure 11D 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.

[0042] Figure 11E A schematic diagram of the astigmatism curves of the projection optical systems of Embodiments 4, 5, and 6 according to this application at a third wavelength is shown.

[0043] Figure 11F 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.

[0044] Figure 12 This is a schematic diagram of the projection optical system according to Embodiment Seven of this application;

[0045] Figure 13 This is a schematic diagram of the projection optical system according to Embodiment 8 of this application;

[0046] Figure 14 This is a schematic diagram of the projection optical system according to Embodiment Nine of this application;

[0047] Figure 15A 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.

[0048] Figure 15B A schematic diagram of the distortion curves of the projection optical system according to Embodiment 7, Embodiment 8 and Embodiment 9 of this application at the first wavelength is shown.

[0049] Figure 15C A schematic diagram of the astigmatism curves of the projection optical system according to Embodiment 7, Embodiment 8 and Embodiment 9 of this application at the second wavelength is shown.

[0050] Figure 15D A schematic diagram of the distortion curves of the projection optical system according to Embodiment 7, Embodiment 8 and Embodiment 9 of this application at the second wavelength is shown.

[0051] Figure 15E A schematic diagram of the astigmatism curves of the projection optical system according to Embodiment 7, Embodiment 8 and Embodiment 9 of this application at a third wavelength is shown.

[0052] Figure 15F A schematic diagram of the distortion curves of the projection optical system according to Embodiment 7, Embodiment 8 and Embodiment 9 of this application at a third wavelength is shown.

[0053] Figure 16A A schematic diagram of stray light spots of the projection optical system is shown when (CT1+CT2) / CP1=1.24, d2m / (T23+CT3)=4.55 and d3s / T34=5.12;

[0054] Figure 16B A schematic diagram of stray light spots of the projection optical system is shown when (CT1+CT2) / CP1=1.24, d2m / (T23+CT3)=6.10 and d3s / T34=7.34;

[0055] Figure 16CA schematic diagram of stray light spots is shown for the projection optical system when (CT1+CT2) / CP1=1.24, d2m / (T23+CT3)=7.60 and d3s / T34=10.15. Detailed Implementation

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] like Figure 1 , Figure 2 as well as Figure 3 As shown, this application proposes a projection optical system, which includes 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 houses a lens group and a spacer assembly; the lens group includes, arranged sequentially along the optical axis from the imaging side to the image source side: a first lens with positive optical power, whose imaging side is concave and image source side is convex; a second lens with positive or negative optical power, whose imaging side is convex and image source side is concave; a third lens with negative optical power, whose image source side is concave; and a fourth lens with positive optical power, whose imaging side is convex and image source side is convex; the spacer assembly includes a first lens placed between the first lens and the second lens and in contact with the image source side of the first lens. A spacer element; a second spacer element placed between the second lens and the third lens and in contact with the image source side of the second lens; a third spacer element placed between the third lens and the fourth lens and in contact with 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.

[0064] Specifically, the projection optical system also satisfies: 0.90 < (CT1 + CT2) / CP1 < 1.65; 4.90 < d2m / (T23 + CT3) ≤ 7.30 and 5.50 < d3s / T34 < 9.80;

[0065] Wherein, CT1 is the center thickness of the first lens on the optical axis, CT2 is the center thickness of the second lens on the optical axis, CP1 is the maximum thickness of the first spacer element along the optical axis, d2m is the inner diameter of the image source side of the second spacer element, T23 is the air gap between the second lens and the third lens on the optical axis, CT3 is the center thickness of the third lens on the optical axis, d3s is the inner 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.

[0066] In projection optics systems, stray light is prone to occur between the second and fourth lenses under the condition that 0.90 < (CT1 + CT2) / CP1 < 1.65. Therefore, this application optimizes the optical path blocking effect and eliminates significant stray light by reasonably designing the relative positions and sizes of the second and third spacer elements within the constraints of 4.91 ≤ d2m / (T23 + CT3) ≤ 7.30 and 5.50 < d3s / T34 < 9.80. When the lower limits of d2m / (T23 + CT3) and d3s / T34 are exceeded, the second and third spacer elements are too small or the spacing is too wide, resulting in insufficient optical path blocking and the generation of clustered stray light. When the upper limits of d2m / (T23 + CT3) and d3s / T34 are exceeded, the second and third spacer elements are too large or the spacing is insufficient, resulting in excessive optical path blocking, affecting the effective luminous flux, and generating ring-shaped stray light.

[0067] For example, Figure 16A A schematic diagram of stray light spots of the projection optical system is shown when (CT1+CT2) / CP1=1.24, d2m / (T23+CT3)=4.55 and d3s / T34=5.12; Figure 16B A schematic diagram of stray light spots of the projection optical system is shown when (CT1+CT2) / CP1=1.24, d2m / (T23+CT3)=6.10 and d3s / T34=7.34; Figure 16C A schematic diagram of stray light spots is shown for the projection optical system when (CT1+CT2) / CP1=1.24, d2m / (T23+CT3)=7.60 and d3s / T34=10.15.

[0068] As can be easily seen from the diagram: Figure 16AAs shown, when the relation (CT1+CT2) / CP1 is greater than 0.9 and less than 1.65, the relation d2m / (T23+CT3) is less than 4.90, and the relation d3s / T34 is less than 5.50, the second and third spacer elements are too small or the spacing is too wide, resulting in insufficient optical path blocking and thus generating clustered stray light.

[0069] like Figure 16B As shown, when the relation (CT1+CT2) / CP1 is greater than 0.9 and less than 1.65, the relation d2m / (T23+CT3) is greater than 4.90 and less than or equal to 7.30, and the relation d3s / T34 is greater than 5.50 and less than 9.80, the optical path blocking effect is good and no obvious stray light is generated.

[0070] like Figure 16C As shown, when the relation (CT1+CT2) / CP1 is greater than 0.9 and less than 1.65, the relation d2m / (T23+CT3) is greater than 7.30, and the relation d3s / T34 is greater than 9.80, the size of the second and third spacers is too large or the spacing is insufficient, which causes the optical path to be excessively blocked, affecting the effective light flux and thus generating ring stray light.

[0071] According to some embodiments of this application, the green light-emitting chip emits light in the wavelength range of 515nm to 545nm, the red light-emitting chip emits light in the wavelength range of 619nm to 636nm, and the blue light-emitting chip emits light in the wavelength range of 450nm to 470nm. Preferably, the first wavelength of the light emitted by the green light-emitting chip is 530nm, the second wavelength of the light emitted by the red light-emitting chip is 627nm, and the third wavelength of the light emitted by the blue light-emitting chip is 460nm.

[0072] In this way, by precisely selecting the wavelengths, it is possible to solve the problems of insufficient color reproduction, low energy efficiency, and poor process compatibility in traditional projection optical systems, which are caused by unreasonable spectral distribution or imbalanced energy ratios in the combination of red, green, and blue light wavelengths. Specifically, green light at a wavelength of 530nm avoids the trough of human eye sensitivity, thus improving light efficiency; red light at a wavelength of 627nm reduces energy loss; and shifting the peak of blue light to 460nm reduces the proportion of harmful blue light (energy percentage reduction of 15%).

[0073] According to some embodiments of this application, the projection optical system satisfies: 0.35≤(D1m-d1m) / |f2R-f2B|<3.15; where D1m is the outer diameter of the image source side of the first spacer element, d1m is the inner diameter of the image source side of the first spacer element, f2R is the focal length of the second lens of the projection optical system at the second wavelength, and f2B is the focal length of the second lens of the projection optical system at the third wavelength.

[0074] In this way, by reasonably controlling the range of this conditional formula, the optical path can be stabilized and the chromatic aberration can be controlled. Specifically, when the ratio is less than the lower limit, the structural strength of the spacer element is insufficient and it is easily affected by thermal deformation, which affects the alignment of the optical axis; while when the ratio is greater than the upper limit, it will cause the difference in divergence angle of light of different wavelengths to increase after passing through the second lens, resulting in significant axial chromatic aberration.

[0075] According to some embodiments of this application, the projection optical system satisfies: 1.75 < L / (EP01+CP1) ≤ 2.35; where L is the maximum height of the lens barrel, 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, and CP1 is the maximum thickness of the first spacer element along the optical axis.

[0076] By reasonably controlling this conditional range, structural stability can be improved, which is beneficial for correcting chromatic aberration and enhancing the performance of optical lenses. Specifically, when the ratio is less than the lower limit, the lens barrel height is insufficient, and the projection optical system is prone to optical axis misalignment due to mechanical vibration or thermal deformation; when the ratio is greater than the lower limit, the optical path spacing is too small, resulting in a decrease in chromatic aberration correction capability.

[0077] According to some embodiments of this application, the projection optical system satisfies: 4.15 < (f1G + f1R + f1B) / d0s < 6.50; where f1G is the focal length of the first lens of the projection optical system at the first wavelength, f1R is the focal length of the first lens of the projection optical system at the second wavelength, f1B is the focal length of the first lens of the projection optical system at the third wavelength, and d0s is the inner diameter of the imaging side of the lens barrel.

[0078] In this way, by reasonably controlling the range of this conditional formula, chromatic aberration can be corrected and the compactness of the structure can be improved, achieving miniaturization. Specifically, when the ratio is less than the lower limit, the first lens has insufficient focusing ability for the three colors of light, and the axial chromatic aberration is significant; while when the ratio exceeds the upper limit, the inner diameter of the lens barrel is too small, the optical path layout is limited, the system volume increases, and the light rays at the edge of the optical path are easily scattered due to the small inner diameter of the lens barrel, thus leading to a decrease in contrast.

[0079] According to some embodiments of this application, the projection optical system satisfies: 4.90mm < d1s × (R1 / R2) ≤ 6.00mm; where d1s is the inner diameter of the imaging side of the first spacer element, R1 is the radius of curvature of the imaging side of the first lens, and R2 is the radius of curvature of the image source side of the first lens.

[0080] In this way, by reasonably controlling the range of this condition, the stability of the optical path and the light combining efficiency can be improved. Specifically, when the ratio is less than the lower limit, the inner diameter of the first spacer element is too small, the light-passing aperture of the optical path is limited, and the optical axis is easily offset due to thermal deformation; while when the ratio exceeds the upper limit, the curvature ratio of the lens is unbalanced, the axial chromatic aberration is significant, and the light combining efficiency of the three colors of light is easily affected.

[0081] According to some embodiments of this application, the projection optical system satisfies: -7.80 < EP23 / (f3R-f3B) ≤ -3.45; where 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, f3R is the focal length of the third lens of the projection optical system at the second wavelength, and f3B is the focal length of the third lens of the projection optical system at the third wavelength.

[0082] In this way, by reasonably controlling this conditional range, axial chromatic aberration can be improved, thereby enhancing image quality and light combining efficiency. Specifically, when the ratio exceeds the above range, the third lens's focusing ability for red light (627nm) and blue light (460nm) is insufficient, resulting in significant axial chromatic aberration.

[0083] According to some embodiments of this application, the projection optical system satisfies: 3.20 < d3m / CT4 ≤ 3.65; where d3m is the inner diameter of the image source side of the third spacer element, and CT4 is the center thickness of the fourth lens on the optical axis.

[0084] In this way, by reasonably controlling the range of this condition, the refractive index distribution of the optical path can be balanced, edge distortion can be reduced, and the consistency of sharpness between the center and the edge of the projected image can be ensured.

[0085] According to some embodiments of this application, the projection optical system satisfies: 1.15 < R4 / (D2s-d2s) < 4.85; where R4 is the radius of curvature of the image source side of the second lens, D2s is the outer diameter of the imaging side of the second spacer element, and d2s is the inner diameter of the imaging side of the second spacer element.

[0086] In this way, by reasonably controlling the range of this condition, the refraction angle of the optical path can be effectively adjusted, aberrations (such as spherical aberration and coma) can be reduced, thereby improving the image clarity.

[0087] According to some embodiments of this application, the projection optical system satisfies: 1.40 < d0m / f4G < 1.85; where d0m is the inner diameter of the image source side of the lens barrel, and f4G is the focal length of the fourth lens of the projection optical system at the first wavelength.

[0088] By properly controlling this conditional range, a sufficient entrance pupil diameter can be ensured, improving light energy utilization and thus enhancing projection brightness.

[0089] According to some embodiments of this application, the projection optical system satisfies: 3.00 < R3 / EP12 ≤ 9.25; where R3 is the radius of curvature of the imaging side of the second lens, 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.

[0090] In this way, by reasonably controlling the range of this conditional expression, the spherical aberration, coma, and field curvature of the lens group can be effectively balanced, thereby suppressing dispersion and improving the performance of the modulation transfer function to enhance the sharpness of the imaging edges.

[0091] According to some embodiments of this application, the projection optical system satisfies: -2.15 < D3s / f3G < -1.25; where D3s is the outer diameter of the imaging side of the third spacer element, and f3G is the focal length of the third lens of the projection optical system at the first wavelength.

[0092] In this way, by reasonably controlling the range of this condition, the field curvature and distortion of the third lens can be effectively compensated, the edge imaging sharpness can be improved, and the total optical length can be reduced to meet the miniaturization requirements of projection equipment.

[0093] According to some embodiments of this application, the projection optical system satisfies: 2.60 < TD / (CP1+CP2+CP3) < 3.20; where TD is the distance on the optical axis from the imaging side of the first lens to the image source side of the fourth lens, 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, and CP3 is the maximum thickness of the third spacer element along the optical axis.

[0094] By properly controlling this conditional range, optical axis shift caused by temperature changes or mechanical vibrations can be reduced, thereby improving the stability of the projected image.

[0095] According to some embodiments of this application, the projection optical system satisfies: 2.80 < fR / (D0s-d0s) < 6.30; where fR is the system focal length of the projection optical system at the second wavelength, D0s is the outer diameter of the imaging side of the lens barrel, and d0s is the inner diameter of the imaging side of the lens barrel.

[0096] In this way, by reasonably controlling the range of this condition, the spherical aberration and coma of the lens group can be effectively balanced, and the sharpness of the imaging edge can be improved; at the same time, the influence of temperature changes on optical axis offset can be reduced, and the assembly tolerance can be improved by combining with aspherical lenses.

[0097] According to some embodiments of this application, the projection optical system satisfies: -1.95 < D0m / R8 < -1.45; where D0m is the outer diameter of the image source side of the lens barrel, and R8 is the radius of curvature of the image source side of the fourth lens.

[0098] By reasonably controlling the range of this condition, the volume redundancy of the system can be effectively reduced, the overall size can be reduced by more than 15%, and the portability of the equipment can be improved.

[0099] 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, as needed, the projection optical system may also include other numbers of spacers than those described in the above embodiments.

[0100] Please combine Figure 2 as well as Figure 3 As shown in the accompanying drawings, some specific, non-limiting embodiments of the above-described embodiments of this application will be described in more detail below. For ease of description, in the following embodiments, 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, S11 represents the image source side of the green light-emitting chip, B represents the blue light-emitting chip of the color combining prism assembly, G represents the green light-emitting chip of the color combining prism assembly, R represents the red light-emitting chip of the color combining prism assembly, Rf represents the red light bandpass filter, and Bf represents the blue light bandpass filter.

[0101] The blue bandpass filter Bf reflects red light incident on it, while blue and green light pass through it; the red bandpass filter Rf reflects blue light incident on it, while red and green light pass through it.

[0102] Example 1

[0103] like Figure 4As 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 contains a lens group and a spacer assembly. The lens group includes a first lens E1, a second lens E2, a third lens E3, and a fourth lens E4 arranged sequentially from the imaging side to the image source side along the optical axis. The spacer assembly includes a first spacer element P1 placed between the first lens E1 and the second lens E2 and in contact with the image source side of the first lens E1; a second spacer element P2 placed between the second lens E2 and the third lens E3 and in contact with the image source side of the second lens E2; and a third spacer element P3 placed between the third lens E3 and the fourth lens E4 and in contact with the image source side of the third lens E3.

[0104] In this embodiment, the first lens E1 has positive optical power, and the imaging side S1 and the image source side S2 of the first lens E1 are concave and convex, respectively; the second lens E2 has positive optical power, and the imaging side S3 and the image source side S4 of the second lens E2 are convex and concave, respectively; the third lens E3 has negative optical power, and the imaging side S5 and the image source side S6 of the third lens E3 are convex and concave, respectively; the fourth lens E4 has positive optical power, and the imaging side S7 and the image source side S8 of the fourth lens E4 are both convex.

[0105] 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).

[0106] Table 1: Basic Optical Parameters of the Projection Optical System in Example 1

[0107]

[0108] Furthermore, Table 2 shows some of the basic optical parameters in Table 1 for different wavelengths, where the wavelength is in nanometers (nm) and the distance D is in millimeters (mm).

[0109] Table 2: Partial optical parameters of the projection optical system of Example 1 at different wavelengths

[0110]

[0111] In this embodiment, the imaging surface and image source surface of any one of the first lens E1 to the fourth lens E4 are aspherical, and the surface shape of each aspherical lens is... The following aspherical formulas can be used for limitation:

[0112] ;

[0113] 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. Table 3 below gives 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.

[0114] Table 3: Aspherical Coefficients of the Projection Optical System in Example 1

[0115]

[0116] Example 2

[0117] like Figure 5 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 contains a lens group and a spacer assembly. The lens group includes a first lens E1, a second lens E2, a third lens E3, and a fourth lens E4 arranged sequentially from the imaging side to the image source side along the optical axis. The spacer assembly includes a first spacer element P1 placed between the first lens E1 and the second lens E2 and in contact with the image source side of the first lens E1; a second spacer element P2 placed between the second lens E2 and the third lens E3 and in contact with the image source side of the second lens E2; and a third spacer element P3 placed between the third lens E3 and the fourth lens E4 and in contact with the image source side of the third lens E3.

[0118] 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 Tables 1 and 2, and the aspherical coefficient table is 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 lies in the fact that the dimensional values ​​of some structural parameters of the lens barrel and the spacer assembly in the projection optical system are different.

[0119] Specifically, the values ​​of various related structural parameters in this embodiment and the above embodiment one are shown in Table 10 below. These structural parameters specifically include: the imaging-side inner diameter d1s of the first spacer element P1; the image source-side inner diameter d1m of the first spacer element P1; the image source-side outer diameter D1m of the first spacer element P1; the imaging-side inner diameter d2s of the second spacer element P2; the image source-side inner diameter d2m of the second spacer element P2; the imaging-side outer diameter D2s of the second spacer element P2; the imaging-side inner diameter d3s of the third spacer element P3; the image source-side inner diameter d3m of the third spacer assembly; the imaging-side outer diameter D3s of the third spacer element P3; the imaging-side inner diameter d0s of the lens barrel P0; the image source-side inner diameter d0m of the lens barrel P0; and the... The outer diameter of the imaging side is D0s; the outer diameter of the image source side of the lens barrel P0 is D0m; the distance EP01 between the imaging side of the lens barrel P0 and the imaging side of the first spacer element P1 along the optical axis; the maximum thickness CP1 of the first spacer element P1 along the optical axis; the distance EP12 between the image source side of the first spacer element P1 and the imaging side of the second spacer element P2 along the optical axis; the maximum thickness CP2 of the second spacer element P2 along the optical axis; the distance EP23 between the image source side of the second spacer element P2 and the imaging side of the third spacer element P3 along the optical axis; the maximum thickness CP3 of the third spacer element P3 along the optical axis; the maximum height L of the lens barrel P0; and the distance TD between the imaging side of the first lens E1 and the image source side of the fourth lens E4 along the optical axis. It is understood that the units of the values ​​of each parameter shown in Table 10 are millimeters (mm), and the schematic diagrams of each parameter in the structural diagram of the projection optical system are as follows: Figure 1 As shown.

[0120] Example 3

[0121] like 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 contains a lens group and a spacer assembly. The lens group includes a first lens E1, a second lens E2, a third lens E3, and a fourth lens E4 arranged sequentially from the imaging side to the image source side along the optical axis. The spacer assembly includes a first spacer element P1 placed between the first lens E1 and the second lens E2 and in contact with the image source side of the first lens E1; a second spacer element P2 placed between the second lens E2 and the third lens E3 and in contact with the image source side of the second lens E2; and a third spacer element P3 placed between the third lens E3 and the fourth lens E4 and in contact with the image source side of the third lens E3.

[0122] 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 Tables 1 and 2, and the aspherical coefficient table is 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 lies in the different dimensional values ​​of some structural parameters of the lens barrel and the spacer assembly in the projection optical system. Specifically, the values ​​of each relevant structural parameter in Embodiment 3 are shown in Table 10 below. The specific descriptions of multiple structural parameters are the same as those in Embodiment 2 above, and will not be repeated here.

[0123] The astigmatism curves of the projection optical system at the first wavelength in Examples 1, 2, and 3 are as follows: Figure 7A As shown, it represents the curvature of the meridional image plane and the curvature of the sagittal image plane; 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, it represents the type and magnitude of lens distortion; the astigmatism curves of the projection optical system at the second wavelength in Embodiments 1, 2, and 3 are shown below. Figure 7C As shown; the distortion curves of the projection optical system at the second wavelength in Embodiments 1, 2, and 3 are as follows. Figure 7D As shown; the astigmatism curves of the projection optical system at the third wavelength in Embodiments 1, 2, and 3 are as follows. Figure 7E As shown; the distortion curves of the projection optical system at the third wavelength in Embodiments 1, 2, and 3 are as follows. Figure 7F As shown. According to Figures 7A-7F It can be seen that the projection optical system in Embodiments 1, 2 and 3 can achieve good imaging quality at the first, second and third wavelengths.

[0124] Example 4

[0125] like Figure 8 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 contains a lens group and a spacer assembly. The lens group includes a first lens E1, a second lens E2, a third lens E3, and a fourth lens E4 arranged sequentially from the imaging side to the image source side along the optical axis. The spacer assembly includes a first spacer element P1 placed between the first lens E1 and the second lens E2 and in contact with the image source side of the first lens E1; a second spacer element P2 placed between the second lens E2 and the third lens E3 and in contact with the image source side of the second lens E2; and a third spacer element P3 placed between the third lens E3 and the fourth lens E4 and in contact with the image source side of the third lens E3.

[0126] In this embodiment, the first lens E1 has positive optical power, and the imaging side S1 and the image source side S2 of the first lens E1 are concave and convex, respectively; the second lens E2 has negative optical power, and the imaging side S3 and the image source side S4 of the second lens E2 are convex and concave, respectively; the third lens E3 has negative optical power, and the imaging side S5 and the image source side S6 of the third lens E3 are convex and concave, respectively; the fourth lens E4 has positive optical power, and the imaging side S7 and the image source side S8 of the fourth lens E4 are both convex.

[0127] In addition, Table 4 shows the basic optical parameters of the projection optical system of Embodiment 4, wherein the units of radius of curvature, thickness / distance and effective radius are all millimeters (mm).

[0128] Table 4: Basic optical parameters of the projection optical system in Example 4

[0129]

[0130] Furthermore, Table 5 shows some of the basic optical parameters in Table 4 for different wavelengths, where the wavelength is in nanometers (nm) and the distance D is in millimeters (mm).

[0131] Table 5: Partial optical parameters of the projection optical system in Example 4 at different wavelengths

[0132]

[0133] In this embodiment, the imaging surface and image source surface of any one of the first lens E1 to the fourth lens E4 are aspherical, and the surface shape of each aspherical lens can be defined by the aspherical formula given in Embodiment 1 above. Table 6 below shows 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 Embodiment 4.

[0134] Table 6: Aspherical Coefficients of the Projection Optical System in Example 4

[0135]

[0136] Example 5

[0137] like Figure 9As 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 contains a lens group and a spacer assembly. The lens group includes a first lens E1, a second lens E2, a third lens E3, and a fourth lens E4 arranged sequentially from the imaging side to the image source side along the optical axis. The spacer assembly includes a first spacer element P1 placed between the first lens E1 and the second lens E2 and in contact with the image source side of the first lens E1; a second spacer element P2 placed between the second lens E2 and the third lens E3 and in contact with the image source side of the second lens E2; and a third spacer element P3 placed between the third lens E3 and the fourth lens E4 and in contact with the image source side of the third lens E3.

[0138] 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 Tables 4 and 5, and the aspherical coefficient table is the same as Table 6. However, the projection optical system of Embodiment 5 has different structural parameters than the projection optical system of Embodiment 4 above. That is, the difference between Embodiment 5 and Embodiment 4 above lies in the different dimensional values ​​of some structural parameters of the lens barrel and the spacer assembly in the projection optical system. Specifically, the values ​​of each relevant structural parameter in Embodiment 5 are shown in Table 10 below. The specific descriptions of multiple structural parameters are the same as those in Embodiment 2 above, and will not be repeated here.

[0139] Example 6

[0140] like Figure 10 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 contains a lens group and a spacer assembly. The lens group includes a first lens E1, a second lens E2, a third lens E3, and a fourth lens E4 arranged sequentially from the imaging side to the image source side along the optical axis. The spacer assembly includes a first spacer element P1 placed between the first lens E1 and the second lens E2 and in contact with the image source side of the first lens E1; a second spacer element P2 placed between the second lens E2 and the third lens E3 and in contact with the image source side of the second lens E2; and a third spacer element P3 placed between the third lens E3 and the fourth lens E4 and in contact with the image source side of the third lens E3.

[0141] 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 Tables 4 and 5, and the aspherical coefficient table is the same as Table 6. However, the projection optical system of Embodiment 6 has different structural parameters than the projection optical system of Embodiment 4 above. That is, the difference between Embodiment 6 and Embodiment 4 above lies in the different dimensional values ​​of some structural parameters of the lens barrel and the spacer assembly in the projection optical system. Specifically, the values ​​of each relevant structural parameter in Embodiment 6 are shown in Table 10 below. The specific descriptions of multiple structural parameters are the same as those in Embodiment 2 above, and will not be repeated here.

[0142] In Examples 4, 5, and 6, the astigmatism of the projection optical system at the first wavelength is as follows: Figure 11A As shown, it represents the curvature of the meridional image plane and the curvature of the sagittal image plane; the distortion curves of the projection optical system at the first wavelength in Examples 4, 5, and 6 are as follows. Figure 11B As shown, it represents the type and size of lens distortion; the astigmatism curves of the projection optical system at the second wavelength in Embodiments 4, 5, and 6 are shown below. Figure 11C As shown; the distortion curves of the projection optical system at the second wavelength in Examples 4, 5, and 6 are as follows. Figure 11D As shown; the astigmatism curves of the projection optical systems in Examples 4, 5, and 6 at the third wavelength are as follows. Figure 11E As shown; the distortion curves of the projection optical system at the third wavelength in Examples 4, 5, and 6 are as follows. Figure 11F As shown. According to Figures 11A-11F It can be seen that the projection optical system in Embodiments 4, 5 and 6 can achieve good imaging quality in the first, second and third wavelengths.

[0143] Example 7

[0144] like Figure 12 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 contains a lens group and a spacer assembly. The lens group includes a first lens E1, a second lens E2, a third lens E3, and a fourth lens E4 arranged sequentially from the imaging side to the image source side along the optical axis. The spacer assembly includes a first spacer element P1 placed between the first lens E1 and the second lens E2 and in contact with the image source side of the first lens E1; a second spacer element P2 placed between the second lens E2 and the third lens E3 and in contact with the image source side of the second lens E2; and a third spacer element P3 placed between the third lens E3 and the fourth lens E4 and in contact with the image source side of the third lens E3.

[0145] In this embodiment, the first lens E1 has positive optical power, and the imaging side S1 and the image source side S2 of the first lens E1 are concave and convex, respectively; the second lens E2 has positive optical power, and the imaging side S3 and the image source side S4 of the second lens E2 are convex and concave, respectively; the third lens E3 has negative optical power, and the imaging side S5 and the image source side S6 of the third lens E3 are both concave; the fourth lens E4 has positive optical power, and the imaging side S7 and the image source side S8 of the fourth lens E4 are both convex.

[0146] In addition, Table 7 shows the basic optical parameters of the projection optical system of Embodiment 7, wherein the units of radius of curvature, thickness / distance and effective radius are all millimeters (mm).

[0147] Table 7: Basic Optical Parameters of the Projection Optical System in Example 7

[0148]

[0149] Furthermore, Table 8 shows some of the basic optical parameters in Table 7 for different wavelengths, where the wavelength is in nanometers (nm) and the distance D is in millimeters (mm).

[0150] Table 8: Partial optical parameters of the projection optical system of Example 7 at different wavelengths

[0151]

[0152] In this embodiment, the imaging surface and image source surface of any one of the first lens E1 to the fourth lens E4 are aspherical, and the surface shape of each aspherical lens can be defined by the aspherical formula given in Embodiment 1 above. Table 9 below gives 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 Embodiment 7.

[0153] Table 9: Aspherical Coefficients of the Projection Optical System in Example 7

[0154]

[0155] Example 8

[0156] like Figure 13As 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 contains a lens group and a spacer assembly. The lens group includes a first lens E1, a second lens E2, a third lens E3, and a fourth lens E4 arranged sequentially from the imaging side to the image source side along the optical axis. The spacer assembly includes a first spacer element P1 placed between the first lens E1 and the second lens E2 and in contact with the image source side of the first lens E1; a second spacer element P2 placed between the second lens E2 and the third lens E3 and in contact with the image source side of the second lens E2; and a third spacer element P3 placed between the third lens E3 and the fourth lens E4 and in contact with the image source side of the third lens E3.

[0157] 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 Tables 7 and 8, and the aspherical coefficient table is 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 and the spacer assembly in the projection optical system are different. Specifically, the values ​​of each relevant structural parameter in Embodiment 8 are shown in Table 10 below. The specific descriptions of multiple structural parameters are the same as those in Embodiment 2 above, and will not be repeated here.

[0158] Example 9

[0159] like Figure 14 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 contains a lens group and a spacer assembly. The lens group includes a first lens E1, a second lens E2, a third lens E3, and a fourth lens E4 arranged sequentially from the imaging side to the image source side along the optical axis. The spacer assembly includes a first spacer element P1 placed between the first lens E1 and the second lens E2 and in contact with the image source side of the first lens E1; a second spacer element P2 placed between the second lens E2 and the third lens E3 and in contact with the image source side of the second lens E2; and a third spacer element P3 placed between the third lens E3 and the fourth lens E4 and in contact with the image source side of the third lens E3.

[0160] 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 Tables 7 and 8, and the aspherical coefficient table is 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 and the spacer assembly in the projection optical system are different. Specifically, the values ​​of each relevant structural parameter in Embodiment 9 are shown in Table 10 below. The specific descriptions of multiple structural parameters are the same as those in Embodiment 2 above, and will not be repeated here.

[0161] The astigmatism curves of the projection optical system at the first wavelength in Examples 7, 8, and 9 are as follows: Figure 15A As shown, it represents the curvature of the meridional image plane and the curvature of the sagittal image plane; the distortion curves of the projection optical system at the first wavelength in Embodiments 7, 8, and 9 are as follows. Figure 15B As shown, it represents the type and size of lens distortion; the astigmatism curves of the projection optical system at the second wavelength in Embodiments 7, 8, and 9 are shown below. Figure 15C As shown; the distortion curves of the projection optical system at the second wavelength in Examples 7, 8, and 9 are as follows. Figure 15D As shown; the astigmatism curves of the projection optical system at the third wavelength in Examples 7, 8, and 9 are as follows. Figure 15E As shown; the distortion curves of the projection optical system at the third wavelength in Examples 7, 8, and 9 are as follows. Figure 15F As shown. According to Figures 15A-15F It can be seen that the projection optical system in Embodiments 7, 8 and 9 can achieve good imaging quality in the first, second and third wavelengths.

[0162] In summary, in Embodiments 1 to 9, the focal lengths f1G, f1R, and f1B of the first lens E1 at the first, second, and third wavelengths, the focal lengths f2G, f2R, and f2B of the second lens E2 at the first, second, and third wavelengths, the focal lengths f3G, f3R, and f3B of the third lens E3 at the first, second, and third wavelengths, the focal lengths f4G, f4R, and f4B of the fourth lens E4 at the first, second, and third wavelengths, the system focal length fR of the projection optical system at the second wavelength, and the distance TD on the optical axis from the imaging side of the first lens to the image source side of the fourth lens are shown in Table 10 below.

[0163] Table 10: System Optical Parameters of the Projection Optical System

[0164]

[0165] Furthermore, the structural parameters of the projection optical system in Examples 1 to 9 are shown in Table 11, where the unit of each parameter is millimeters (mm).

[0166] Table 11: Structural Parameters of Projection Optical System

[0167]

[0168] In summary, the projection optical systems in Examples 1 to 9 satisfy the relationships shown in Table 12, as detailed in Table 12.

[0169] Table 12: Relationships satisfied by projection optical systems

[0170]

[0171] 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.

[0172] 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 barrel and a color-combining prism assembly arranged sequentially from the imaging side to the image source side along the optical axis; the lens barrel contains a lens group and a spacer assembly; The lens group includes the following lenses arranged sequentially along the optical axis from the imaging side to the image source side: a first lens with positive optical power, whose imaging side is concave and image source side is convex; a second lens with optical power, whose imaging side is convex and image source side is concave; a third lens with negative optical power, whose image source side is concave; and a fourth lens with positive optical power, whose imaging side is convex and image source side is convex. The spacing assembly includes a first spacing element disposed between the first lens and the second lens and in contact with the image source side of the first lens; a second spacing element disposed between the second lens and the third lens and in contact with the image source side of the second lens; and a third spacing element disposed between the third lens and the fourth lens and in contact with 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 towards the image source side of the fourth lens; the projection optical system also satisfies: 0.90<(CT1+CT2) / CP1<1.65; 4.90<d2m / (T23+CT3)≤7.30; 5.50 < d3s / T34 < 9.80; Wherein, CT1 is the center thickness of the first lens on the optical axis, CT2 is the center thickness of the second lens on the optical axis, CP1 is the maximum thickness of the first spacer element along the optical axis, d2m is the inner diameter of the image source side of the second spacer element, T23 is the air gap between the second lens and the third lens on the optical axis, CT3 is the center thickness of the third lens on the optical axis, d3s is the inner 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 515nm to 545nm, the red light-emitting chip emits light in the wavelength range of 619nm to 636nm, 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 530nm, the red light-emitting chip emits light at a second wavelength of 627nm, 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 0.35≤(D1m-d1m) / |f2R-f2B|<3.15; where D1m is the outer diameter of the image source side of the first spacer element, d1m is the inner diameter of the image source side of the first spacer element, f2R is the focal length of the second lens of the projection optical system at the second wavelength, and f2B is the focal length of the second lens of the projection optical system at the third wavelength.

5. The projection optical system according to claim 1, characterized in that, The projection optical system satisfies: 1.75 < L / (EP01+CP1) ≤ 2.35; where L is the maximum height of the lens barrel, 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, and CP1 is the maximum thickness of the first spacer element along the optical axis.

6. The projection optical system according to claim 3, characterized in that, The projection optical system satisfies: 4.15 < (f1G + f1R + f1B) / d0s < 6.50; where f1G is the focal length of the first lens of the projection optical system at the first wavelength, f1R is the focal length of the first lens of the projection optical system at the second wavelength, f1B is the focal length of the first lens of the projection optical system at the third wavelength, and d0s is the inner diameter of the imaging side of the lens barrel.

7. The projection optical system according to claim 1, characterized in that, The projection optical system satisfies: 4.90mm < d1s × (R1 / R2) ≤ 6.00mm; where d1s is the inner diameter of the imaging side of the first spacer element, R1 is the radius of curvature of the imaging side of the first lens, and R2 is the radius of curvature of the image source side of the first lens.

8. The projection optical system according to claim 3, characterized in that, The projection optical system satisfies: -7.80 < EP23 / (f3R-f3B) ≤ -3.45; where 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, f3R is the focal length of the third lens of the projection optical system at the second wavelength, and f3B is the focal length of the third lens of the projection optical system at the third wavelength.

9. The projection optical system according to claim 1, characterized in that, The projection optical system satisfies: 3.20 < d3m / CT4 ≤ 3.65; where d3m is the inner diameter of the image source side of the third spacer element, and CT4 is the center thickness of the fourth lens on the optical axis.

10. The projection optical system according to claim 1, characterized in that, The projection optical system satisfies: 1.15 < R4 / (D2s-d2s) < 4.85; where R4 is the radius of curvature of the image source side of the second lens, D2s is the outer diameter of the imaging side of the second spacer element, and d2s is the inner diameter of the imaging side of the second spacer element.

11. The projection optical system according to claim 3, characterized in that, The projection optical system satisfies: 1.40 < d0m / f4G < 1.85; where d0m is the inner diameter of the image source side of the lens barrel, and f4G is the focal length of the fourth lens of the projection optical system at the first wavelength.

12. The projection optical system according to claim 1, characterized in that, The projection optical system satisfies: 3.00 < R3 / EP12 ≤ 9.25; where R3 is the radius of curvature of the imaging side of the second lens, 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.

13. The projection optical system according to claim 3, characterized in that, The projection optical system satisfies: -2.15 < D3s / f3G < -1.25; where D3s is the outer diameter of the imaging side of the third spacer element, and f3G is the focal length of the third lens of the projection optical system at the first wavelength.

14. The projection optical system according to claim 1, characterized in that, The projection optical system satisfies: 2.60 < TD / (CP1+CP2+CP3) < 3.20; where TD is the distance on the optical axis from the imaging side of the first lens to the image source side of the fourth lens, 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, and CP3 is the maximum thickness of the third spacer element along the optical axis.

15. The projection optical system according to claim 3, characterized in that, The projection optical system satisfies: 2.80 < fR / (D0s-d0s) < 6.30; where fR is the system focal length of the projection optical system at the second wavelength, D0s is the outer diameter of the imaging side of the lens barrel, and d0s is the inner diameter of the imaging side of the lens barrel.

16. The projection optical system according to claim 1, characterized in that, The projection optical system satisfies: -1.95 < D0m / R8 < -1.45; where D0m is the outer diameter of the image source side of the lens barrel, and R8 is the radius of curvature of the image source side of the fourth lens.

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