CN106444019A - Stabilized broadband optical system - Google Patents

Abstract

The invention discloses a stabilized broadband optical system comprising a first optical element L1 and a second optical element L2. The first optical element L1 and the second optical element L2 are arranged successively from left to right and are made of same materials. An outer ring region s1 of the front surface of the first optical element L1 is a transmission plane and a central circle region s2 is an inner reflection plane; a rear surface s3 of the first optical element L1 is a transmission plane; an outer ring region s4 of the front surface of the second optical element L2 is a reflection plane and a central circle region s5 is a transmission plane; and a central circle region s6 of the rear surface of the second optical element L2 is a transmission plane. According to the invention, common-caliber imaging at the ultra broad band of 0.7 microns to 14 microns is realized by using an optical material. Moreover, the system has advantages of simple and compact structure, easy installation and adjustment, and high stability.

Description

A stable broadband optical system

technical field

The invention belongs to the technical field of optical devices, and in particular relates to a stable wide-band optical lens.

Background technique

With the continuous improvement of military target camouflage and stealth technology, the traditional single-band optical detection method has been greatly challenged, and it has been difficult to meet the complex needs of military reconnaissance. Because the same target has completely different optical characteristics in different spectral bands, and each band has a special role, for example, LED light sources have high radiation efficiency in the near-infrared band, and short-wave infrared has good glow night vision Function, mid-wave infrared has a strong detection effect on high-temperature objects, and long-wave infrared has a good detection effect on the radiation of surface objects. Therefore, in order to better identify different targets in military applications, dual-band or even multi-band imaging technology become a research hotspot.

In such applications, higher and higher requirements are put forward for optical lenses, as follows:

1. Cover at least two bands, including near-infrared, short-wave infrared, mid-wave infrared and long-wave infrared;

2. Small and light. That is to say, the total length is required, the number of lenses is small, and the back focus is appropriate;

3. High brightness. That is, the number of F# is small;

However, the existing optical lens designs usually only cover two wavelength bands, namely mid-wave infrared and long-wave infrared, and the number of optical lenses and the types of materials are relatively large, and the volume and weight have become bottlenecks restricting further applications.

Contents of the invention

In view of this, the present invention provides a stable wide-band optical system. The present invention realizes common-aperture imaging in the ultra-wide band of 0.7 μm to 14 μm through only one optical material, and has the advantages of simple and compact structure, easy installation and adjustment, and stable Advantages of high sex.

In order to achieve the above purpose, the technical solution of the present invention is: a stable wide-band optical system, including the first optical element L ₁ and the second optical element L ₂ arranged in sequence from left to right, wherein the two materials are the same ; The outer ring area s ₁ of the front surface of the first optical element L ₁ is a transmission surface, and the central circle area s ₂ is an internal reflection surface; the rear surface s ₃ of the first optical element L ₁ is a transmission surface; the second _The outer ring area _s4 of the front surface of the optical element L2 is a reflective surface, and the central circular area _s5 is a transmissive surface; the central circular area _s6 of the rear surface of the _second optical element L2 is a transmissive surface.

Furthermore, after the light is incident from the left side, it passes through the front surface outer ring area s ₁ and the back surface s ₃ of the first optical element L ₁ , and reaches the front surface outer ring area s ₄ of the second optical element L ₂ for reflection. Then it is incident on the back surface s ₃ of the first optical element L ₁ , passes through the transmission and reaches the internal reflection surface s ₂ of the front surface, passes through the back surface s ₃ again after reflection, transmits out of the first optical element L ₁ , and reaches the second optical element L ₂ , the central circular area s ₅ of the front surface of the second optical element L ₂ finally passes through the central circular area s ₆ of the rear surface of the second optical element L 2 to the target surface of the detector for imaging.

Further, the materials used for the first optical element L ₁ and the second optical element L ₂ are zinc selenide.

Further, the first optical element L ₁ is a meniscus lens, and the front surface of the second optical element L ₂ is a concave surface.

Further, the optical power 1/f _{1 of the first optical element L 1 is} negative, the optical power 1/f ₂ of the second optical element L ₂ is positive, and f ₁ and f ₂ are respectively the first optical element L ₁ and the focal length of the _second optical element L2.

Further, the optical surfaces s ₁ , s ₂ , s ₃ , s ₄ , s ₅ and s ₆ of L ₁ and L ₂ are all aspheric; wherein the outer ring area s ₁ and the central ring of the first optical element L ₁ are The area s ₂ is a continuous surface, and the two surfaces have the same aspheric function; the outer ring area s ₄ and the central ring area s ₅ of the front surface of the optical element L ₂ are continuous surfaces, and the two surfaces have the same aspheric function.

Further, the ratio of the focal length f of the entire optical system meets the following requirements:

-10<f ₁ /f<-30

10<f ₂ /f<20

0.9<f/D<2.1

Where f is the focal length of the entire optical system, D is the total length of the optical system after air-converted distance, that is, the distance from the surface of L1 to the target surface _of the detector, and f/D is the focal ratio of the entire optical system.

Further, the surface aspheric surfaces of the _first optical element L1 and the _second optical element L2 satisfy the following function:

Among them, z is the axial value starting from the intersection point of each aspheric surface and the optical axis and parallel to the direction of the optical axis, k is the Conic coefficient, c is the reciprocal of the radius of curvature of the mirror center, r is the height of the mirror center; a ₄ , a ₆ , a ₈ , a ₁₀ , and a ₁₂ are aspheric coefficients.

Beneficial effect:

1. The present invention only uses two pieces of optical elements and one type of optical material. After the light enters from the left side, it passes through the outer ring area s ₁ of the front surface of the first optical element L ₁ and the rear surface s ₃ to reach the second optical element L The outer ring area s ₄ of the front surface of ₂ is reflected, and then incident on the back surface s ₃ of the first optical element L ₁ , and then reaches the internal reflection surface s ₂ of the front surface after being reflected, passes through the back surface s ₃ again, and is transmitted out The first optical element L ₁ reaches the central circular area s ₅ of the front surface of the second optical element L ₂ , and finally passes through the central circular area s ₆ of the rear surface of the second optical element L ₂ to the target surface of the detector for imaging; wherein The process of "transmitting to the internal reflection surface s ₂ of the front surface, and passing through the back surface s ₃ after reflection" can produce a special color difference to balance the color difference produced by other surfaces of the whole system, which is corrected by using different materials in the prior art The methods of chromatic aberration are different. In the prior art, the range of the receiving wavelength range of the lens will be greatly limited due to the use of a variety of different materials to correct the chromatic aberration; while the optical structure in the present invention is used to correct the chromatic aberration, a material is used It can realize wide-band optical reception. It has been verified by experiments that it can cover three bands with wavelengths of 0.7-1.6 μm, 3.7-4.8 μm and 8-14 μm, F#1.2 (effective F#1.6), and the telephoto ratio reaches 0.58 optical system .

2. The optical structure in the present invention shortens the total length of the system through multiple refractions and reflections, and corrects various on-axis and off-axis aberrations well, so it has a simple and compact structure, easy installation and adjustment, and high stability advantage.

Description of drawings

Fig. 1 is the structural diagram of the ultra-wide band co-aperture optical system of the present invention;

Fig. 2 is a side view of an aspheric surface;

Fig. 3 is the optical transfer function MTF of the system at 0.7-1.6 μm in the embodiment of the present invention;

Fig. 4 is the optical transfer function MTF of the system at 3.7-4.8 μm in the embodiment of the present invention;

Fig. 5 is the optical transfer function MTF of the system in the range of 8-14 μm in the embodiment of the present invention;

Fig. 6 is the color difference curve of the system at 0.7-1.6 μm in the embodiment of the present invention;

Fig. 7 is the color difference curve of the system at 3.7-4.8 μm in the embodiment of the present invention;

Fig. 8 is the color difference curve of the system at 8-14 μm in the embodiment of the present invention.

detailed description

The present invention will be described in detail below with reference to the accompanying drawings and examples.

A stable broadband optical system, as shown in Figure 1, includes a first optical element L ₁ and a second optical element L ₂ arranged in sequence from left to right; the outer surface of the front surface of the first optical element L ₁ The ring area s ₁ is a transmission surface, the central circular area s ₂ is an internal reflection surface; the rear surface s ₃ of the first optical element L ₁ is a transmission surface; the outer ring area s ₄ of the front surface of the second optical element L ₂ is a reflection surface The central circle area s ₅ is the transmission surface; the central circle area s ₆ of the rear surface of the second optical element L ₂ is the transmission surface.

In the present invention, after the light is incident from the left side, it passes through the outer ring region s ₁ of the front surface of the first optical element L ₁ , exits through s ₃ and arrives at the outer ring region s ₄ of the second optical element L ₂ , where it is reflected. Then it is incident on the back surface s ₃ of the first optical element L ₁ , passes through the transmission and reaches the internal reflection surface s ₂ of the front surface, passes through the back surface s ₃ again after reflection, transmits out of the first optical element L ₁ , and reaches the second optical element L ₂ , the central circular area s ₅ of the front surface of the second optical element L ₂ finally passes through the central circular area s ₆ of the rear surface of the second optical element L 2 to the target surface of the detector for imaging. Among them, the process of "transmitting to the internal reflection surface s ₂ of the front surface, and passing through the rear surface s ₃ after reflection" can produce a special color difference to balance the color difference produced by other surfaces of the whole system, which is different from the existing technology through the use of different materials. The methods for correcting chromatic aberration are different. In the prior art, the range of receiving wavelength bands of the lens will be greatly limited due to the use of a variety of different materials to correct chromatic aberration; while the optical structure in the present invention is used to correct chromatic aberration. The material can realize wide-band optical reception.

In the present invention, the materials used for the first optical element L ₁ and the second optical element L ₂ are zinc selenide.

In the present invention, the first optical element L1 is _a meniscus lens, and the front surface of the _second optical element L2 is a concave surface.

In the present invention, the optical power 1/f _{1 of the first optical element L 1 is} negative, the optical power 1/f ₂ of the second optical element L ₂ is positive, and f ₁ and f ₂ are respectively the first optical element L ₁ and the focal length of the second optical element L ₂ .

In the present invention, the optical surfaces s ₁ , s ₂ , s ₃ , s ₄ , s ₅ and s ₆ of L ₁ and L ₂ are all aspheric surfaces, and the side view of the aspheric surfaces is shown in Figure 2; wherein the first optical element L ₁ The outer ring area s ₁ and the central ring area s ₂ of the front surface are continuous surfaces, and the two surfaces have the same aspheric function; the outer ring area s ₄ and the central ring area s ₅ of the optical element L ₂ are continuous surfaces, Both surfaces have the same aspheric function.

In the present invention, the ratio of the focal length f of the entire optical system meets the following requirements:

-10<f ₁ /f<-30

10<f ₂ /f<20

0.9<f/D<2.1

Where f is the focal length of the entire optical system, D is the total length of the optical system after air-converted distance, and f/D is the focal ratio of the entire optical system.

In the present invention, the surface aspheric surfaces of the _first optical element L1 and the _second optical element L2 satisfy the following function:

Among them, z is the axial value starting from the intersection point of each aspheric surface and the optical axis and parallel to the direction of the optical axis, k is the Conic coefficient, c is the reciprocal of the radius of curvature of the mirror center, r is the height of the mirror center; a ₄ , a ₆ , a ₈ , a ₁₀ , and a ₁₂ are aspheric coefficients.

Example,

As shown in FIG. 1 , the ultra-broadband optical system of the present invention includes a first optical element L ₁ and a second optical element L ₂ . Utilizing the ultra-wide applicable wavelength band of zinc selenide material in 0.55～18μm, through the special chromatic aberration characteristics of the Mankin reflector structure, the chromatic aberration of the system is effectively eliminated, and the chromatic aberration of the system is realized, and the chromatic aberration of 0.7～1.6μm, 3.7～4.8μm, 8～14μm is realized. Band co-aperture imaging optical system. The outer ring area s ₁ of the front surface of the first optical element L ₁ is a transmission surface, and the central circular area s ₂ is an internal reflection surface; the back surface s ₃ of the first optical element L ₁ is a transmission surface; the front surface of the second optical element L ₂ The outer ring area _s4 is a reflective surface, and the central circular area _s5 is a transmissive surface; the central circular area _s6 of the rear surface of the _second optical element L2 is a transmissive surface;

The optical path of this optical system is briefly described as follows:

The light passes through the outer ring region s ₁ of the front surface of the first optical element L ₁ , exits through s ₃ and arrives at the outer ring region s ₄ of the second optical element L ₂ , is reflected, and re-enters the outer ring region of the first optical element L ₁ The rear surface s ₃ , after transmission, reaches the internal reflection surface s ₂ of the front surface, passes through the rear surface s ₃ again after reflection, transmits the first optical element L ₁ , and reaches the central circular area s ₅ of the front surface of the second optical element L ₂ , and finally pass through the central circular area s ₆ of the rear surface of the second optical element L ₂ to be emitted to the target surface of the detector for imaging. After multiple refractions and reflections, the total length of the system is shortened, and various on-axis and off-axis aberrations are well corrected.

The above-mentioned aspherical surface shape satisfies the following function:

Among them, z is the axial value starting from the intersection of each aspheric surface and the optical axis and parallel to the direction of the optical axis, k is the Conic coefficient, c is the reciprocal of the radius of curvature of the mirror center, and r is the height of the mirror center; a ₂ , a ₄ , a ₆ , a ₈ and a ₁₀ are aspherical coefficients

The following is only a preferred example of the present invention, the selected system focal length is 80mm, the focal ratio (F/D) is 1.72, the total system length is 46.5mm, the semi-instantaneous field of view is 5°, and the design results show that it is suitable for the 0.7-1.6μm waveband The optical transfer function is greater than 0.4 at 50lp/mm, the optical transfer function is greater than 0.7 at 17lp/mm for the 3.7-4.8μm band, and the optical transfer function is close to the diffraction limit for the 8-14μm band. The system eliminates chromatic aberration very well, and the image quality is excellent. Compared with Figure 1, a series of better data are selected as shown in Table 1 and Table 2 below.

Table 1

Among them, the data in the fourth column in Table 1 from top to bottom are: the distance between the geometric center of S ₁ and the geometric center of S ₃ ; the distance between the geometric center of S ₃ and the geometric center of S ₄ ; the distance between the geometric center of S ₄ and the geometric center of S ₃ The distance between the geometric centers; the distance between the S ₃ geometric center and the S ₂ geometric center; the distance between the S ₂ geometric center and the S ₅ geometric center; the distance between the S ₅ geometric center and the S ₆ geometric center.

Table 2

The optical elements L ₁ and L ₂ in the above-mentioned preferred embodiment are both made of ZnSe, and both are aspherical.

On the basis of this embodiment, Figure 3 shows the optical transfer function MTF of the system at 0.7-1.6 μm; Figure 4 shows the optical transfer function MTF of the system at 3.7-4.8 μm; Figure 5 shows the system at 8 Optical transfer function MTF of ~14μm; Figure 6 shows the chromatic aberration curve of the system at 0.7-1.6μm; Figure 7 shows the chromatic aberration curve of the system at 3.7-4.8μm; Figure 8 shows the chromatic aberration curve of the system at 8-14μm curve.

As can be seen from the figure above, this embodiment realizes the wavelength coverage of 0.7-1.6μm, 3.7-4.8μm and 8-14μm three bands, F#1.2 (effective F#1.6), and a compact type with a telephoto ratio of 0.58 optical system.

To sum up, the above are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (8)

1. A stable broadband optical system, characterized in that it includes a first optical element L ₁ and a second optical element L ₂ arranged in sequence from left to right, wherein the two materials are the same; the first optical element The outer ring area s ₁ of the front surface of the element L ₁ is a transmission surface, and the central circular area s ₂ is an internal reflection surface; the rear surface s ₃ of the first optical element L ₁ is a transmission surface; the outer surface of the second optical element L ₂ The ring region _s4 is a reflective surface, the central circular region _s5 is a transmissive surface; the central circular region _s6 of the rear surface of the _second optical element L2 is a transmissive surface. 2. A stable wide-band optical system as claimed in claim 1, characterized in that, after the light is incident from the left side, it passes through the front surface outer ring area s ₁ and the rear surface s ₃ of the first optical element L ₁ to exit Arriving at the outer ring area s ₄ of the front surface of the second optical element L ₂ , reflection occurs, and then incident on the back surface s ₃ of the first optical element L ₁ , after transmission reaches the internal reflection surface s ₂ of the front surface, after reflection and re-passing The surface s ₃ transmits the first optical element L ₁ , reaches the central circular area s ₅ of the front surface of the second optical element L ₂ , and finally passes through the central circular area s ₆ of the rear surface of the second optical element L ₂ to the detector Target surface imaging. 3. A stable broadband optical system as claimed in claim 1, characterized in that the materials used for the _first optical element L1 and the _second optical element L2 are zinc selenide. 4. A stable broadband optical system according to claim 1, characterized in that the first optical element L1 is _a meniscus lens, and the front surface of the _second optical element L2 is a concave surface. 5. A kind of stable broadband optical system as claimed in claim 1, 2, 3 or 4, characterized in that: the optical power ₁ /f of the first optical element L ₁ is negative, and the second optical element L The optical power 1/f ₂ of the element L ₂ is positive, and f ₁ and f ₂ are the focal lengths of the first optical element L ₁ and the second optical element L ₂ respectively. 6. A stable broadband optical system as claimed in claim 1, 2, 3 or 4, characterized in that: the optical surfaces s ₁ , s ₂ , s ₃ , s ₄ , s ₅ of L ₁ and L ₂ and _s6 are both aspherical surfaces; the outer ring area _s1 and the central ring area s2 of the _first optical element L1 are continuous surfaces, and the _two surfaces have the same aspheric function _; the outer ring area of the front surface of the optical element L2 The ring area s ₄ and the central ring area s ₅ are continuous surfaces, and the two surfaces have the same aspheric function. 7. A stable broadband optical system as claimed in claim 5, characterized in that: the ratio of the focal length f of the entire optical system meets the following requirements: -10<f ₁ /f<-30 10<f ₂ /f<20 0.9<f/D<2.1 Where f is the focal length of the entire optical system, D is the total length of the optical system after air-converted distance, that is, the distance from the surface of L1 to the target surface _of the detector, and f/D is the focal ratio of the entire optical system. 8. A kind of stable broadband optical system as claimed in claim 6, is characterized in that, the surface aspheric surface of described first optical element L ₁ and second optical element L ₂ satisfies the following function: $\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; cr</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>{\mathrm{<span\; class="notranslate">\; c</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 5</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 12</span>}}$ Among them, z is the axial value starting from the intersection point of each aspheric surface and the optical axis and parallel to the direction of the optical axis, k is the Conic coefficient, c is the reciprocal of the radius of curvature of the mirror center, r is the height of the mirror center; a ₄ , a ₆ , a ₈ , a ₁₀ , and a ₁₂ are aspheric coefficients.