CN110632741A

CN110632741A - Projection lens

Info

Publication number: CN110632741A
Application number: CN201910901652.5A
Authority: CN
Inventors: 龚敬剑; 程发超; 贺银波; 陆巍
Original assignee: Shenzhen Dianjingchuangshi Technology Co Ltd
Current assignee: Shenzhen Dianjingchuangshi Technology Co Ltd
Priority date: 2019-09-23
Filing date: 2019-09-23
Publication date: 2019-12-31

Abstract

The application discloses projection lens, camera lens includes in proper order from formation of image reduction end to formation of image reduction end: the device comprises a first group of lenses with positive focal length, a diaphragm, a second group of lenses with positive focal length, a jitter device, a light splitting device, protective glass and an imaging surface; the first group of lenses has a focal length of 550< f7<570, the second group of lenses has a focal length of 10< f8< 12; the last lens of the second group of lenses is a glass aspheric surface. According to the projection lens, the dithering device is arranged to participate in imaging, so that the resolution of the projection lens when the device is static is the inherent resolution of the DMD chip, and the other resolution is during dithering.

Description

Projection lens

Technical Field

The application relates to the technical field of projection lenses, in particular to a projection lens.

Background

The projection lens is a core component of the projection device: after passing through the reflective or transmissive light modulation device, the light needs to be projected onto a projection screen through a projection lens for imaging.

As the projection device plays a larger and larger role in life, the application field is also increased. More devices need to be embedded into a miniature projection device, and the requirement on a projection lens is higher and higher, the size is smaller, the structure is more compact, the imaging effect is better, and the projection lens with lower cost becomes the mainstream.

The transmittance of the existing projection lens on the market is generally more than 1.2, the field angle is about 60 degrees, the lens of the existing projection optical machine can only be matched with a fixed resolution, and the size of the projection lens is longer. In order to meet the market demand of high resolution and reduce the difficulty of imaging design of the lens, the F number is mostly more than 2, which causes the reduction of brightness.

Disclosure of Invention

The application provides a projection lens, which participates in imaging by arranging a jitter device, so that the resolution of the projection lens when the device is static is the inherent resolution of a DMD chip, and the other resolution is the other resolution when the device is jittered.

The application provides a projection lens, the lens includes in proper order from formation of image reduction end to formation of image reduction end: the device comprises a first group of lenses with positive focal length, a diaphragm, a second group of lenses with positive focal length, a jitter device, a light splitting device, protective glass and an imaging surface; the first group of lenses has a focal length of 550< f7<570, the second group of lenses has a focal length of 10< f8< 12; the last lens of the second group of lenses is a glass aspheric surface.

Preferably, the first group of lenses comprises a first lens, a second lens and a third lens in sequence.

Preferably, the first lens is a concave-convex plastic aspheric lens with a negative focal length; the second lens is a biconcave glass lens with a negative focal length; the third lens is a biconvex glass lens with a positive focal length.

Preferably, both surfaces of the first lens are aspheric; both surfaces of the second lens are spherical surfaces; and the two surfaces of the third lens are spherical surfaces.

Preferably, the focal length of the first lens is-12.59 < f1< -10.59; the focal length of the second lens is-23.85 < f2< -21.82; the third lens has a focal length of 10.25< f3< 12.25.

Preferably, the second group of lenses comprises a fourth lens, a fifth lens and a sixth lens in sequence.

Preferably, the fourth lens is a biconcave glass lens with a negative focal length; the fifth lens is a biconvex glass lens with a positive focal length; the sixth lens is a biconvex glass lens with a negative focal length.

Preferably, both surfaces of the fourth lens are spherical; both surfaces of the fifth lens are spherical surfaces; and the two surfaces of the sixth lens are spherical surfaces.

Preferably, the focal length of the fourth lens is-13.58 < f4< -11.58; the focal length of the fifth lens is 14.25< f5< -11.58; the sixth lens has a focal length of 11.35< f6< 12.35.

According to the technical scheme, the embodiment of the application has the following advantages:

the application provides a miniature projection lens, the camera lens includes in proper order from formation of image reduction end to formation of image reduction end: the device comprises a first group of lenses with positive focal length, a diaphragm, a second group of lenses with positive focal length, a jitter device, a light splitting device, protective glass and an imaging surface; the first group of lenses has a focal length of 550< f7<570, the second group of lenses has a focal length of 10< f8< 12; the last lens of the second group of lenses is a glass aspheric surface.

According to the projection lens, the dithering device is arranged to participate in imaging, so that the resolution of the projection lens when the device is static is the inherent resolution of the DMD chip, and the other resolution is during dithering.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive exercise.

Fig. 1 is an optical structure diagram of a projection lens provided in an embodiment of the present application;

fig. 2 is MTF values of field transfer functions of a projection lens provided in an embodiment of the present application;

fig. 3 is a field curvature and distortion diagram of a projection lens provided in an embodiment of the present application, where Millineters is a field curvature evaluation diagram, and Percent is a distortion evaluation diagram;

fig. 4 is a vertical axis chromatic aberration graph of a projection lens provided in an embodiment of the present application.

Detailed Description

Referring to fig. 1 to 4, fig. 1 is an optical structure diagram of a projection lens provided in an embodiment of the present application; fig. 2 is MTF values of field transfer functions of a projection lens provided in an embodiment of the present application; fig. 3 is a field curvature and distortion diagram of a projection lens provided in an embodiment of the present application, where Millineters is a field curvature evaluation diagram, and Percent is a distortion evaluation diagram; fig. 4 is a vertical axis chromatic aberration graph of a projection lens provided in an embodiment of the present application.

Fig. 1 is an optical structure diagram of a projection lens provided in an embodiment of the present application; the application provides a projection lens, which sequentially comprises from an imaging magnification end to an imaging reduction end: the device comprises a first group lens with a positive focal length, a diaphragm, a second group lens with a positive focal length, a jitter device, a light splitting device, protective glass and an imaging surface; the first group of lenses comprises a first lens and a concave-convex lens with a negative focal length; a second lens having a biconcave lens with a negative focal length; a third lens having a biconvex lens with a positive focal length; a fourth lens having a biconcave lens with a negative focal length; a fifth lens having a biconvex lens with a positive focal length; and a sixth lens having a negative focal length meniscus lens.

Particularly, the last lens of the miniature projection lens is a glass aspheric lens, so that the defect that the lens of the miniature projection lens is out of focus due to heating of the plastic aspheric lens can be effectively overcome. The lens has the characteristics of large projection ratio, easiness in assembly and high imaging quality.

The miniature projection lens adopts a negative lens P1, a negative lens G2, a negative lens G3, a diaphragm aperture, a negative lens G4, a positive lens G5 and a positive lens G6 which are sequentially arranged from the amplification end to the reduction:

the first lens P1 is a concave-convex lens made of plastic material and having negative focal power, the concave surface faces the aperture direction of the diaphragm, and the two surfaces S1 and S2 are aspheric surfaces; the focal length of the first lens satisfies-12.59 < f1- < -10.59, and the refractive index satisfies Nd 1-1.531.

The second lens G2 is a biconcave lens with negative focal power and made of glass material, and the two surfaces S3 and S4 are spherical surfaces, and the lens surface with smaller curvature radius faces to the aperture direction of the diaphragm; the focal length of the second lens satisfies-23.85 < f2< -21.82, and the refractive index satisfies Nd 2-1.595.

The third lens G3 is a biconvex lens with positive focal power made of glass material, and the two surfaces S5 and S6 have the same curvature radius of the spherical surface; the focal length of the third lens satisfies 10.25< f3<12.25, and the refractive index satisfies Nd 3-1.904.

A fourth lens G4, which is a biconcave lens with negative focal power made of glass material, and both surfaces S6 and S7 are spherical surfaces, and the concave surface faces away from the diaphragm aperture; the focal length of the fourth lens satisfies-13.58 < f4< -11.58, and the refractive index satisfies Nd 4-1.834.

A fifth lens G5, made of glass material and having positive focal power and biconvex type, and both surfaces S8 and S9 are spherical surfaces, wherein the relatively flat mirror surface faces the diaphragm aperture; the focal length of the fifth lens satisfies 14.25< f5<16.25, and the refractive index satisfies Nd 5-1.497.

A sixth lens G6, which is a negative power meniscus lens made of glass material, and has two surfaces S10 and S11 both being spherical surfaces and both facing the aperture of the diaphragm; the focal length of the sixth lens satisfies 11.35< f6<12.35, and the refractive index satisfies Nd 6-1.622.

The focal length of the first group of lenses satisfies: 550< f7<570, the second group lens focal length satisfies: 10< f8< 12.

The natural frequency of the embodiment of the application is 540p, two frequencies of 720p and 1080p are generated when the activator device shakes, the principle is that the activator device overturns and shakes, incident light is divided into two after passing through the activator, and due to the fact that the frequency is high, the effect of human eye visual persistence is utilized, and the effect looks like two pixels (only one is generated when the activator device does not shake). According to the frequency and amplitude of the jitter, two resolutions, 720p and 1080p, can be distinguished.

In order to achieve the technical purpose of effectively improving the optical performance of the micro projection lens, specific parameters of the micro projection lens provided by the embodiment of the application are as shown in table one; the parameters include the thickness and spacing of each lens, the refractive index Nd (refractive index) of each lens, the numerical aperture F/NO, the Abbe number Vd (Abbe number), and the radius of curvature R (radius of curvature) of each lens.

Watch 1

Two surfaces are aspheric surfaces, the surfaces S1 and S2 of the aspheric surface lens P1 and the surfaces S10 and S11 of the aspheric surface biconvex lens GM6 can obtain a curve corresponding to the spherical surface by an aspheric surface formula; the aspheric formula is as follows:

wherein: z represents a distance in the optical axis direction of a point on the aspherical surface from the aspherical surface vertex; r represents the distance of a point on the non-surface to the optical axis; c represents the center curvature of the aspherical surface; k represents the conicity; a4, a6, a8, and a10 represent aspheric high-order term coefficients.

The aspheric lens P1 and GM8 have respective order coefficients as shown in Table two.

Watch two

The projection lens is obtained according to the specific parameters of the lenses, as shown in fig. 2 of the optical system. The MTF (English name: Modulation Transfer Function) index is the most accurate and scientific evaluation standard of the current lens. The ordinate is the contrast, the closer to 1, the better the representative lens imaged. The abscissa represents the resolution in units of log per millimeter. The size of the image source pixel adopted by the embodiment of the application is 5.4um, and the corresponding design resolution is 93 line pairs per millimeter. Projection lenses typically require at least mtf values for each field of view to be above 0.3 at the design resolution, whereas mtf values for each field of view in the present embodiment are substantially above 0.5.

In fig. 3, the left image is a field curvature evaluation image, and the right image is a distortion evaluation image. The ordinate represents the angle of the field of view of the lens. The abscissa of the curvature of field graph represents the magnitude of the curvature of field value, and the abscissa of the distortion graph represents the amount of distortion. Distortion is a very important index of a projection lens, and generally needs to be controlled within 3%, and the distortion of the embodiment of the present application is within 1%.

Fig. 4 is a vertical axis chromatic aberration diagram of the lens, the ordinate is the size of the image height field of view value, and the abscissa is the size of the numerical value in unit micrometer. The difference in color for each field of view between blue, red and green light (dominant wavelength) is plotted separately, based on the dominant wavelength. The projection lens generally requires that the color difference value is within one image source pixel size, and the vertical axis chromatic aberration of the embodiment of the application is controlled within 2.8um and less than 0.6 pixel size (pixel size is 5.4 um).

The principle that the brightness can be improved in the embodiment of the application is as follows: the numerical aperture is D (entrance pupil diameter)/f (focal length), and in the case of keeping the focal length unchanged, the larger the numerical aperture is, which means that the entrance pupil diameter is larger, the entrance pupil represents an optical entrance in the optical system, and the larger the entrance, the larger the light energy that can be received is, and therefore, the higher the brightness is.

Generally speaking, the relative aperture value is less, and the formation of image quality satisfies more easily, but relative aperture value is little, and the light energy that passes through just diminishes, leads to the decline of projection luminance, so this application embodiment, when improving relative aperture value through optical design, can guarantee the formation of image quality again, has not few promotion to luminance.

The lens uses two aspheric lenses, and the capability of correcting aberration of 1 aspheric lens is close to that of several spherical lenses, so compared with the lens using pure spherical lenses, the lens effectively reduces the required number of lenses and shortens the length of the lens.

Because the projection lens needs to bear a large amount of projection light, part of light energy can be converted into heat energy, and the last lens of the lens can gather more light energy, so that the temperature of the lens is increased. The influence of temperature to the plastics material is great, if last piece adopts the plastics aspheric surface, then takes place easily to run burnt problem, consequently this application last piece lens is glass aspheric surface material, can avoid running burnt problem.

The distance from the first lens to the DMD surface is less than 48mm, and under the distance, an excellent imaging effect can be achieved, the numerical aperture is large, and the brightness is improved.

The embodiment of the application is adaptive to display with various resolutions and can be applied to various image source display schemes such as DMD, laser, LCOS, LCD and the like. The 6-lens structure has a larger tolerance range, and the yield of the lens in mass production is improved.

While the micro projection lens provided in the embodiments of the present application has been described in detail, for those skilled in the art, according to the idea of the embodiments of the present application, there are variations in the specific implementation and the application scope, and in summary, the content of the present application should not be construed as a limitation to the present application.

Claims

1. A projection lens is characterized in that the lens sequentially comprises from an imaging magnification end to an imaging reduction end: the device comprises a first group of lenses with positive focal length, a diaphragm, a second group of lenses with positive focal length, a jitter device, a light splitting device, protective glass and an imaging surface; the first group of lenses has a focal length of 550< f7<570, the second group of lenses has a focal length of 10< f8< 12; the last lens of the second group of lenses is a glass aspheric surface.

2. The projection lens as claimed in claim 1, wherein the first group of lenses comprises a first lens, a second lens and a third lens in sequence.

3. The projection lens of claim 2, wherein the first lens is a concave-convex plastic aspheric lens with negative focal length; the second lens is a biconcave glass lens with a negative focal length; the third lens is a biconvex glass lens with a positive focal length.

4. The projection lens of claim 2 wherein both surfaces of the first lens are aspheric; both surfaces of the second lens are spherical surfaces; and the two surfaces of the third lens are spherical surfaces.

5. The projection lens of claim 2 wherein the first lens has a focal length of-12.59 < f1< -10.59; the focal length of the second lens is-23.85 < f2< -21.82; the third lens has a focal length of 10.25< f3< 12.25.

6. The projection lens as claimed in claim 1, wherein the second group of lenses comprises a fourth lens, a fifth lens and a sixth lens in sequence.

7. The projection lens of claim 6, wherein the fourth lens is a biconcave glass lens with a negative focal length; the fifth lens is a biconvex glass lens with a positive focal length; the sixth lens is a biconvex glass lens with a negative focal length.

8. The projection lens of claim 6 wherein both surfaces of the fourth lens are spherical; both surfaces of the fifth lens are spherical surfaces; and the two surfaces of the sixth lens are spherical surfaces.

9. The projection lens of claim 6 wherein the focal length of the fourth lens is-13.58 < f4< -11.58; the focal length of the fifth lens is 14.25< f5< -11.58; the sixth lens has a focal length of 11.35< f6< 12.35.