CN102879888B - Fixed focus projection lens - Google Patents

Abstract

The invention relates to a fixed-focus projection lens, which comprises a first lens group and a second lens group which are sequentially arranged along an optical axis from an imaging side to an image source side, wherein the first lens group has positive refractive power and comprises a first lens and a second lens which are sequentially arranged; the first lens is made of plastic material and has negative refractive power; the second lens is made of glass material and has positive refractive power; the second lens group has positive refractive power and comprises a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens which are arranged in sequence; the third lens is made of plastic materials and has negative refractive power; the fourth lens is made of glass material and has negative refractive power; the fifth lens is made of glass material, has positive refractive power, and is glued with the fourth lens to form a composite lens with negative refractive power; the sixth lens is made of plastic materials and has positive refractive power; the seventh lens is made of glass material and has negative refractive power.

Description

Fixed Focus Projection Lens

technical field

The present invention relates to a projector, and more specifically refers to a fixed-focus projection lens.

Background technique

In recent years, with the advancement of imaging technology, more and more people use projectors for presentations, video conferences, conferences or watching videos. In order to make the projector more portable and easy to use, the size of the fixed-focus projection lens used to clearly present the image on the screen will also be greatly reduced to meet the needs of miniaturization and light weight that people expect. Furthermore, in addition to miniaturization and light weight, higher optical performance is also required to achieve high-resolution and high-contrast image display. Therefore, miniaturization and high optical performance are two indispensable elements of a fixed-focus projection lens.

However, the known fixed-focus projection lens usually includes more than three sets of mirror groups, and there must be a certain interval between these mirror groups. At the same time, these mirror groups all include a plurality of lenses. There is a certain distance. Therefore, the known fixed-focus projection lens is not only large in size and heavy in weight, but cannot achieve a miniaturized and lightweight design, and because there are many internal mirror groups and lenses, it takes a long time to assemble and assemble. And the cost of materials consumed is not easy to reduce. Based on the above, it can be seen that the known fixed-focus projection lens is still not perfect and needs to be improved.

Contents of the invention

The technical problem to be solved by the present invention is to provide a fixed-focus projection lens consisting of two sets of mirror groups, which is not only small in size, but also has high Optical performance.

The technical solution adopted by the present invention to solve the technical problem is to provide a fixed-focus projection lens, which includes a first mirror group and a second mirror group arranged in sequence along the optical axis from the imaging side to the image source side, wherein , the first lens group has positive refractive power, and includes a first lens and a second lens arranged in sequence from the imaging side to the image source side; the first lens is made of plastic material and has negative refractive power; the The second lens is made of glass material and has positive refractive power; the second lens group has positive refractive power and includes a third lens, a fourth lens, and a fifth lens arranged in sequence from the imaging side to the image source side , the sixth lens and the seventh lens; the third lens is made of plastic material and has negative refractive power; the fourth lens is made of glass material and has negative refractive power; the fifth lens is made of glass material and has negative refractive power; It has positive refractive power, and the fifth lens is cemented with the fourth lens to form a composite lens with negative refractive power; the sixth lens is made of plastic material and has positive refractive power; the seventh lens is made of glass material and has Negative refractive power.

Therefore, the fixed-focus projection lens achieves miniaturization and high optical performance by utilizing the above-mentioned lens design.

Description of drawings

Fig. 1 is the lens arrangement diagram of the first preferred embodiment of the present invention;

Fig. 2A is the field curvature diagram of the first preferred embodiment of the present invention;

Fig. 2B is a distortion diagram of the first preferred embodiment of the present invention;

Figure 2C is a longitudinal color difference diagram of the first preferred embodiment of the present invention;

FIG. 2D is an optical fan diagram of the first preferred embodiment of the present invention;

FIG. 2E is a spatial frequency modulation transfer function diagram of the first preferred embodiment of the present invention;

Fig. 3 is the lens arrangement diagram of the second preferred embodiment of the present invention;

FIG. 4A is a field curvature diagram of the second preferred embodiment of the present invention;

Fig. 4B is a distortion diagram of the second preferred embodiment of the present invention;

Figure 4C is a longitudinal color difference diagram of the second preferred embodiment of the present invention;

FIG. 4D is an optical fan diagram of the second preferred embodiment of the present invention;

FIG. 4E is a diagram of the spatial frequency modulation transfer function of the second preferred embodiment of the present invention.

Detailed ways

In order to illustrate the present invention more clearly, preferred embodiments are given and described in detail with accompanying drawings as follows.

Please refer to FIG. 1 , which is a lens configuration diagram of a fixed-focus projection lens 1 according to a first preferred embodiment of the present invention. The mirror group G1 and the second mirror group G2. In addition, an internal total reflection prism TP (Total internal reflection Prism) and a glass cover CG (Cover Glass) are arranged sequentially between the second mirror group G2 and the image source side. Let me repeat. in:

The first lens group G1 has positive refractive power, and includes a first lens L1 and a second lens L2 arranged in sequence from the imaging side to the image source side. The first lens L1 is made of plastic material. The first lens L1 is a crescent lens with negative refractive power. The convex surface R1 faces the imaging side, and both the convex surface R1 and the concave surface R2 are aspheric surfaces. The second lens L2 is made of glass material. The second lens L2 is a crescent lens with positive refractive power, and its convex surface R3 faces the imaging side.

The second lens group G2 has positive refractive power and includes a third lens L3 , a fourth lens L4 , a fifth lens L5 , a sixth lens L6 and a seventh lens L7 arranged in sequence from the imaging side to the image source side. The third lens L3 is made of plastic material. The third lens L3 is a crescent lens with negative refractive power, its convex surface R5 faces the imaging side, and its convex surface R5 and concave surface R6 are both aspherical surfaces. In addition, the aperture ST of the fixed-focus projection lens 1 is located on the convex surface R5 of the third lens L3. The fourth lens L4 is made of glass material. The fourth lens L4 is a biconcave lens with negative refractive power. The fifth lens L5 is made of glass material. The fifth lens L5 is a biconvex lens with positive refractive power, and the fifth lens L5 is cemented with the fourth lens L4 to form a composite lens L45 with negative refractive power. The sixth lens L6 is made of plastic material. The sixth lens L6 is a biconvex lens with positive refractive power, and its two convex surfaces R10 and R11 are both aspheric surfaces. The seventh lens L7 is made of glass material. The seventh lens L7 is a biconvex lens with positive refractive power.

In addition, in order to effectively reduce the total length and volume of the fixed-focus projection lens 1 and correct aberrations to achieve better imaging quality, the fixed-focus projection lens 1 satisfies the following conditions:

(1) 1.75＜|F1/F|＜1.83

(2) 0.80＜|F2/F|＜0.82

(3) 1.95＜|FL1/F|＜2.33

(4) 0.57＜|v4/v5|＜0.61

(5) 8.50＜|ex/lt|＜17.0

(6) Nd _L2 > 1.80

Wherein, F is the focal length of the fixed-focus projection lens 1; F1 is the focal length of the first lens group G1; F2 is the focal length of the second lens group G2; FL1 is the focal length of the first lens L1; v4 is the fourth The dispersion coefficient of the lens L4; v5 is the dispersion coefficient of the fifth lens L5; ex is the exit pupil position (exit pupil position) of the fixed-focus projection lens 1; lt is the length of the fixed-focus projection lens 1; Nd _L2 is the The refractive index of the second lens L2.

In order to achieve the above-mentioned purpose and effectively improve the optical performance of the fixed-focus projection lens 1, the focal length F (Focus Length), the numerical aperture FNO (F-number), and the number of each lens surface of the fixed-focus projection lens 1 of the first embodiment of the present invention The radius of curvature where the optical axis Z passes, the distance between each lens, the refractive index Nd (refractive index) of each lens and the Abbe number Vd (Abbe number) of each lens are shown in Table 1:

Table I

In each lens of the present embodiment, the surface concavity D of these aspheric surfaces R1, R2, R5, R6, R10 and R11 is obtained by the following formula:

$\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; C</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 12</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 14</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 14</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 16</span>}}$

D: Concavity of the aspheric surface;

C: the reciprocal of the radius of curvature;

H: Aperture radius of the surface;

K: conical coefficient;

E4～E16: Each order coefficient of the hole radius H on the surface.

In this embodiment, the conic coefficient K (conic constant) of each aspheric surface and the coefficients E4 to E16 of each order of the surface aperture radius H are shown in Table 2:

Table II

With the configuration of the above-mentioned lenses and apertures, the fixed-focus projection lens 1 of this embodiment can not only effectively reduce the size to meet the needs of lightweight imaging devices, but also meet the requirements in terms of imaging quality, which can be seen from FIG. 2A to FIG. 2E sees.

Shown in Fig. 2A, is the field curvature (Field Curvature) figure of the fixed-focus projection lens 1 of the present embodiment; Shown in Fig. 2B, is the distortion (Distortion) figure of the fixed-focus projection lens 1 of the present embodiment; Fig. 2C Shown is the longitudinal chromatic aberration (Longitudinal) diagram of the fixed-focus projection lens 1 of the present embodiment; shown in FIG. 2D is the light fan (Ray Fan) diagram of the fixed-focus projection lens 1 of the present embodiment; FIG. 2E Shown is the spatial frequency modulation transfer function diagram (Spatial Frequency MTF) of the fixed-focus projection lens 1 of the present embodiment.

It can be seen from Figure 2A that the maximum field curvature of this embodiment does not exceed 0.06mm and -0.04mm; it can be seen from Figure 2B that the distortion of this embodiment does not exceed 1.2%; it can be seen from Figure 2C that this embodiment The maximum longitudinal chromatic aberration of the example is not more than 0.04mm and -0.02mm; as can be seen from Figure 2D, this embodiment has good resolution no matter in which field of view position; it can be seen from Figure 2E that this embodiment has a /mm, the value of the modulation optical transfer function is still above 40%, which shows that the resolution of the fixed-focus projection lens 1 of this embodiment is in compliance with the standard.

The above is the fixed-focus projection lens 1 of the first preferred embodiment of the present invention; according to the technology of the present invention, the fixed-focus projection lens 2 of the second preferred embodiment of the present invention will be described below with reference to FIG. 3 .

The fixed-focus projection lens 2 includes a first lens group G1 and a second lens group G2 arranged in sequence along the optical axis Z from the imaging side to the image source side. In addition, an internal total reflection prism TP (Total internal reflection Prism) and a glass cover CG (CoverGlass) are also arranged sequentially between the second mirror group G2 and the image source side. in:

The first lens group G1 has positive refractive power, and includes a first lens L1 and a second lens L2 arranged in sequence from the imaging side to the image source side. The first lens L1 is made of plastic material. The first lens L1 is a crescent lens with negative refractive power. The convex surface R1 faces the imaging side, and both the convex surface R1 and the concave surface R2 are aspheric surfaces. The second lens L2 is made of glass material. The second lens L2 is a crescent lens with positive refractive power, and its convex surface R3 faces the imaging side.

The second lens group G2 has positive refractive power and includes a third lens L3 , a fourth lens L4 , a fifth lens L5 , a sixth lens L6 and a seventh lens L7 arranged in sequence from the imaging side to the image source side. The third lens L3 is made of plastic material. The third lens L3 is a crescent lens with negative refractive power, its convex surface R5 faces the imaging side, and its convex surface R5 and concave surface R6 are both aspherical surfaces. In addition, the aperture ST of the fixed-focus projection lens 2 is located on the convex surface R5 of the third lens L3. The fourth lens L4 is made of glass material. The fourth lens L4 is a biconcave lens with negative refractive power. The fifth lens L5 is made of glass material. The fifth lens L5 is a biconvex lens with positive refractive power, and the fifth lens L5 is cemented with the fourth lens L4 to form a composite lens L45 with negative refractive power. The sixth lens L6 is made of plastic material. The sixth lens L6 is a biconvex lens with positive refractive power, and its two convex surfaces R10 and R11 are both aspheric surfaces. The seventh lens L7 is made of glass material. The seventh lens L7 is a biconvex lens with positive refractive power.

Similarly, in order to effectively reduce the total length and volume of the fixed-focus projection lens 2 and correct aberrations to achieve better imaging quality, the fixed-focus projection lens 2 also meets the following conditions:

(1) 1.75＜|F1/F|＜1.83

(2) 0.80＜|F2/F|＜0.82

(3) 1.95＜|FL1/F|＜2.33

(4) 0.57＜|v4/v5|＜0.61

(5) 8.50＜|ex/lt|＜17.0

(6) Nd _L2 > 1.80

Wherein, F is the focal length of the fixed-focus projection lens 2; F1 is the focal length of the first lens group G1; F2 is the focal length of the second lens group G2; FL1 is the focal length of the first lens L1; v4 is the fourth The dispersion coefficient of the lens L4; v5 is the dispersion coefficient of the fifth lens L5; ex is the exit pupil position (exit pupil position) of the fixed-focus projection lens 2; lt is the length of the fixed-focus projection lens 2; Nd _L2 is the The refractive index of the second lens L2.

In order to achieve the above-mentioned purpose and effectively improve the optical performance of the fixed-focus projection lens 2, the focal length F (Focus Length), the numerical aperture FNO (F-number), the surface of each lens of the fixed-focus projection lens 2 of the second embodiment of the present invention The radius of curvature where the optical axis Z passes, the distance between each lens, the refractive index Nd (refractive index) of each lens and the Abbe number Vd (Abbe number) of each lens are shown in Table 3:

Table three

In each lens of the present embodiment, the surface concavity D of these aspheric surfaces R1, R2, R5, R6, R10 and R11 is obtained by the following formula:

$\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; C</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 12</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 14</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 14</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}^{\mathrm{<span\; class="notranslate">\; 16</span>}}$

D: Concavity of the aspheric surface;

C: the reciprocal of the radius of curvature;

H: Aperture radius of the surface;

K: conical coefficient;

E4～E16: Each order coefficient of the hole radius H on the surface.

In this embodiment, the conic coefficient K (conic constant) of each aspheric surface and the coefficients E4 to E16 of each order of the surface aperture radius H are shown in Table 4:

Table four

With the configuration of the above-mentioned lenses and apertures, the fixed-focus projection lens 2 of this embodiment can not only effectively reduce the size to meet the needs of lightweight imaging devices, but also meet the requirements in terms of imaging quality, which can be seen from FIG. 4A to FIG. 4E sees.

Shown in Figure 4A is the field curvature (Field Curvature) figure of the fixed-focus projection lens 2 of the present embodiment; Shown in Figure 4B is the distortion (Distortion) figure of the fixed-focus projection lens 2 of the present embodiment; Figure 4C Shown is the longitudinal chromatic aberration (Longitudinal) diagram of the fixed-focus projection lens 2 of the present embodiment; shown in FIG. 4D is the light fan (Ray Fan) diagram of the fixed-focus projection lens 2 of the present embodiment; FIG. 4E Shown is the spatial frequency modulation transfer function diagram (Spatial Frequency MTF) of the fixed-focus projection lens 2 of the present embodiment.

It can be seen from Figure 4A that the maximum field curvature of this embodiment does not exceed 0.08mm and -0.02mm; it can be seen from Figure 4B that the distortion of this embodiment does not exceed 1.2%; it can be seen from Figure 4C that this embodiment The maximum longitudinal chromatic aberration of the example does not exceed 0.05mm and -0.02mm at most; it can be seen from Figure 4D that this embodiment has good resolution no matter in which field of view position; it can be seen from Figure 4E that this embodiment can /mm, the value of the modulation optical transfer function is still above 30%, which shows that the resolution of the fixed-focus projection lens 2 of this embodiment meets the standard.

Based on the above, it can be seen that the fixed-focus projection lens of the present invention can not only effectively reduce the size but also have high optical performance.

The above description is only a preferred feasible embodiment of the present invention, and any equivalent structure and manufacturing method changes made by applying the specification and claims of the present invention should be included in the patent scope of the present invention.

Claims (11)

1. a fixed focus projection lens, is characterized in that, includes along optical axis and by becoming image side to image source side sequential:

First mirror group, has positive refractive power, and includes by this one-tenth image side to the first eyeglass of this image source side sequential and the second eyeglass; This first eyeglass is made up of plastic material, and has negative refractive power; This second eyeglass is made up of glass material, and has positive refractive power; And

Second mirror group, has positive refractive power, and includes by this one-tenth image side to the 3rd eyeglass of this image source side sequential, the 4th eyeglass, the 5th eyeglass, the 6th eyeglass and the 7th eyeglass; 3rd eyeglass is made up of plastic material, and has negative refractive power; 4th eyeglass is made up of glass material, and has negative refractive power; 5th eyeglass is made up of glass material, and has positive refractive power, and the 5th eyeglass and the 4th eyeglass glue together the compound lens forming and have negative refractive power; 6th eyeglass is made up of plastic material, and has positive refractive power; 7th eyeglass is made up of glass material, and has positive refractive power.

2. fixed focus projection lens as claimed in claim 1, is characterized in that, this first eyeglass at least one side is non-spherical surface.

3. fixed focus projection lens as claimed in claim 1, it is characterized in that, the refractive index of this second eyeglass is greater than 1.80.

4. fixed focus projection lens as claimed in claim 1, is characterized in that, the 3rd eyeglass at least one side is non-spherical surface.

5. fixed focus projection lens as claimed in claim 1, is characterized in that, more include aperture, be positioned at the 3rd eyeglass towards on the face of this one-tenth image side.

6. fixed focus projection lens as claimed in claim 1, is characterized in that, the 6th eyeglass at least one side is non-spherical surface.

7. fixed focus projection lens as claimed in claim 1, is characterized in that, more meet following condition:

1.75<|F1/F|<1.83, wherein, F1 is the focal length of this first mirror group; F is the focal length of this fixed focus projection lens.

8. fixed focus projection lens as claimed in claim 1, is characterized in that, more meet following condition:

0.80<|F2/F|<0.82, wherein, F2 is the focal length of this second mirror group; F is the focal length of this fixed focus projection lens.

9. fixed focus projection lens as claimed in claim 1, is characterized in that, more meet following condition:

1.95<|FL1/F|<2.33, wherein, FL1 is the focal length of this first eyeglass; F is the focal length of this fixed focus projection lens.

10. fixed focus projection lens as claimed in claim 1, is characterized in that, more meet following condition:

0.57<|v4/v5|<0.61, wherein, v4 is the abbe number of the 4th eyeglass; V5 is the abbe number of the 5th eyeglass.

11. fixed focus projection lens as claimed in claim 1, is characterized in that, more meet following condition:

8.50<|ex/lt|<17.0, wherein, ex is the exit pupil position of this fixed focus projection lens; Lt is the length of this fixed focus projection lens.