Medium wave infrared lens

Abstract

The utility model relates to a medium wave infrared lens comprising a lens barrel, and a front fixing group with positive focal power, a zooming group with negative focal power, a compensation group with positive focal power, a focusing group with negative focal power and a rear fixing group are arranged in the lens barrel from left to right in sequence along the light incidence direction. And the rear fixed group consists of a first lens with positive focal power, a second lens with negative focal power and a third lens with positive focal power. The utility model has the advantages of reasonable design, simple and compact structure, light weight, long detection distance, low distortion, vibration resistance and impact resistance.

Description

Technical Field

[0001] The utility model relates to a mid-wave infrared lens. Background Art

[0002] With the rapid development of science and technology and the continuous development and increasing maturity of refrigeration detector technology, due to many excellent characteristics of mid-wave refrigerated infrared optical systems, such as good penetration, the ability to adapt to complex environments; high transmission efficiency, capable of efficiently collecting and transmitting mid-wave infrared radiation; high precision, etc., they have been widely used in both military and civilian fields. In recent years, with the long-term development of mid-wave refrigerated infrared optical technology and the continuous expansion of its application scope, the demand for mid-wave refrigerated infrared continuous zoom optical systems has been increasing. The mid-wave refrigerated infrared continuous zoom optical system can continuously change the system focal length within a certain range. While changing the field of view, the image plane can remain stable and clear without image plane drift. The current mid-wave refrigerated infrared continuous zoom lenses, although having the function of continuous zoom, have complex structures, heavy weights, and large volumes. Content of the Utility Model

[0003] In view of the deficiencies of the prior art, the utility model improves the above problems and provides a mid-wave infrared lens.

[0004] The utility model is composed of a lens barrel. Inside the lens barrel, a front fixed group with positive optical power, a zoom group with negative optical power, a compensation group with positive optical power, a focusing group with negative optical power, and a rear fixed group are sequentially arranged from left to right along the light incident direction. The rear fixed group is composed of a first lens with positive optical power, a second lens with negative optical power, and a third lens with positive optical power.

[0005] Furthermore, the air gap between the front fixed group and the zoom group is 18.01 mm, the air gap between the zoom group and the compensation group is 6.81 mm, the air gap between the compensation group and the focusing group is 4.53 mm, the air gap between the focusing group and the first lens of the rear fixed group is 10.47 mm, the air gap between the first lens and the second lens is 0.95 mm, and the air gap between the second lens and the third lens is 0.2 mm.

[0006] Furthermore, the lens barrel includes a main lens barrel, a focusing lens barrel, and a rear lens barrel. The front fixed group is installed inside the front section of the main lens barrel. Inside the middle section of the main lens barrel, a zoom slide for installing the zoom group is provided. Inside the rear section of the main lens barrel, a compensation slide for installing the compensation group is provided. The focusing group is installed inside the focusing lens barrel, and the rear fixed group is installed inside the rear lens barrel. An electric zoom mechanism is provided outside the main lens barrel, and an electric focusing mechanism is provided outside the focusing lens barrel.

[0007] Further, the electric zoom mechanism includes a zoom motor bracket mounted outside the main lens barrel. A zoom motor is mounted on the zoom motor bracket. A zoom motor gear is provided on the output shaft of the zoom motor. A zoom cam meshing with the zoom motor gear is provided outside the main lens barrel. A potentiometer is provided beside the zoom motor. The potentiometer gear of the potentiometer is precisely meshed with the motor gear. A micro switch for limiting the stroke is also provided on the main lens barrel. The zoom cam is fastened by a zoom retaining ring. A zoom groove and a compensation groove are provided on the zoom cam. Cam guide pins are provided in both the zoom groove and the compensation groove. The cam guide pin in the zoom groove is in sliding fit with the zoom groove and is connected to the zoom slide. The cam guide pin in the compensation groove is in sliding fit with the compensation groove and is in sliding fit with the compensation slide.

[0008] Further, the electric focusing mechanism includes a focusing motor bracket mounted on the focusing lens barrel. A focusing motor is mounted on the focusing motor bracket. A focusing motor gear is mounted on the main shaft of the focusing motor. The focusing motor gear meshes with a focusing ring provided on the outer periphery of the focusing lens barrel to drive the focusing ring to rotate. A focusing potentiometer is provided beside the focusing motor. The focusing potentiometer gear of the focusing potentiometer meshes with the focusing motor gear. Micro switches for limiting the stroke are also provided on both sides of the focusing motor bracket.

[0009] Further, a shutter for background correction is provided at the rear end of the rear lens barrel. The shutter is driven by a motor mounted outside the rear lens barrel. A stop pin for limiting the shutter is also mounted outside the rear lens barrel.

[0010] Further, a camera bracket is provided behind the rear lens barrel. The camera bracket is connected to the rear lens barrel through a bottom plate. An auxiliary support frame is also provided between the rear lens barrel and the camera bracket.

[0011] Compared with the prior art, the present utility model has the following beneficial effects: The structure of the device is designed simply, compactly, with light weight, long detection distance, low distortion, and resistance to vibration and impact. Description of the Drawings

[0012] Figure 1 is a schematic diagram of the optical system of the embodiment of the present utility model;

[0013] Figure 2 is a short - focal - length distortion diagram of the embodiment of the present utility model;

[0014] Figure 3 is a short - focal - length MTF diagram of the embodiment of the present utility model;

[0015] Figure 4 is a long - focal - length distortion diagram of the embodiment of the present utility model;

[0016] Figure 5 is a long - focal - length MTF diagram of the embodiment of the present utility model;

[0017] Figure 6 is a cross-sectional view of the lens according to an embodiment of the present utility model;

[0018] Figure 7 is a schematic diagram of the lens structure according to an embodiment of the present utility model Figure 1 ;

[0019] Figure 8 is a schematic diagram of the lens structure according to an embodiment of the present utility model Figure 2 . Specific embodiments

[0020] The present utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] Embodiment 1: As Figures 1 - 8 shown, the present utility model provides a mid-wave infrared lens, which includes a lens barrel. Inside the lens barrel, a front fixed group A with positive optical power, a variable magnification group B with negative optical power, a compensation group C with positive optical power, a focusing group D with negative optical power, and a rear fixed group are sequentially arranged from left to right along the light incident direction. The rear fixed group is composed of a first lens E with positive optical power, a second lens F with negative optical power, and a third lens G with positive optical power.

[0022] In the embodiment of the present utility model, the air gap between the front fixed group and the variable magnification group is 18.01 mm, the air gap between the variable magnification group and the compensation group is 6.81 mm, the air gap between the compensation group and the focusing group is 4.53 mm, the air gap between the focusing group and the first lens of the rear fixed group is 10.47 mm, the air gap between the first lens and the second lens is 0.95 mm, and the air gap between the second lens and the third lens is 0.2 mm.

[0023] The above-mentioned front fixed group includes a front lens, the above-mentioned variable magnification group includes a variable magnification lens, the above-mentioned compensation group includes a compensation lens, and the above-mentioned focusing group includes a focusing lens.

[0024] In the embodiment of the present utility model, the optical system composed of the above lenses can achieve the following technical indicators:

[0025] (1) Working wavelength range: 7.7 μm - 9.3 μm;

[0026] (2) Adapted detector: Long-wave infrared cooled type 640×512, 15um;

[0027] (3) F number: ≥2.0.

[0028] The specific design parameters of the optical system in the embodiment of the present utility model are shown in Table 1 below:

[0029]

[0030] Table 1

[0031] In Table 1 above, S1 and S2 respectively represent two surfaces of the front fixed group, S3 and S4 respectively represent two surfaces of the varifocal group, S5 and S6 respectively represent the mirror surfaces of the compensation group, S7 and S8 respectively represent the mirror surfaces of the focusing group, and S13, 17, S18, S19, S20, S21 respectively represent two surfaces of the first, second, and third lenses of the rear fixed group in sequence.

[0032] In the embodiment of the present utility model, Table 2 below shows the aspherical related data.

[0033]

[0034] Table 2

[0035] The expression of the aspherical surface is:

[0036]

[0037] Among them, Z represents the position in the optical axis direction, r represents the height in the direction perpendicular to the optical axis, c represents the radius of curvature, k represents the conic coefficient, represents the aspherical coefficient. In the aspherical data, E-n represents " ", for example, 4.525E-005 represents .

[0038] Embodiment 2: On the basis of Embodiment 1, in the embodiment of the present utility model, the lens barrel includes a main lens barrel 1, a focusing lens barrel 4, and a rear lens barrel 6. The front fixed group is installed inside the front section of the main lens barrel. A varifocal slide 2 for installing the varifocal group is arranged inside the middle section of the main lens barrel. A compensation slide 3 for installing the compensation group is arranged inside the rear section of the main lens barrel. The focusing group is installed inside the focusing lens barrel, and the rear fixed group is installed inside the rear lens barrel. An electric zoom mechanism is arranged outside the main lens barrel, and an electric focusing mechanism is arranged outside the focusing lens barrel.

[0039] The focusing lens barrel is locked to the rear end of the main lens barrel by screws. A focusing lens seat 5 for placing the focusing lens is arranged on the inner circle of the focusing lens barrel. A focusing ring with a stroke guiding function is arranged on the outer circumference of the focusing lens barrel. The three are fixedly connected by a focusing guide pin 17; the rear lens barrel is screwed to the rear end of the focusing lens barrel.

[0040] In the embodiment of the present utility model, the electric zoom mechanism includes a zoom motor bracket 7 installed outside the main lens barrel. A zoom motor 8 is installed on the zoom motor bracket. A zoom motor gear 9 is provided on the output shaft of the zoom motor. A zoom cam 10 meshing with the zoom motor gear is arranged outside the main lens barrel. A potentiometer 11 is arranged beside the zoom motor for zoom stroke positioning. A potentiometer gear 12 of the potentiometer is precisely meshed with the motor gear. A micro switch 13 for limiting the stroke is also provided on the main lens barrel.

[0041] The zoom cam is fastened by a zoom retaining ring 14. A zoom groove and a compensation groove are provided on the zoom cam. Cam guide pins 15 are arranged in both the zoom groove and the compensation groove. The cam guide pins are arranged at the front and rear ends of the zoom cam. The cam guide pin at the front end is in sliding fit with the zoom groove and is connected to the zoom slide frame. The cam guide pin at the rear end is in sliding fit with the compensation groove and is in sliding fit with the compensation slide frame.

[0042] Due to the overall structure of the lens being relatively small and compact, the cooperation length between the zoom and compensation slide frames and the main lens barrel is short. To ensure the optical axis offset, different from the single-group zoom groove and compensation groove in the usual design, two groups of cooperation grooves are respectively set for the zoom and compensation groups in this design to eliminate the influence caused by the insufficient cooperation length of the slide frame.

[0043] In the embodiment of the present utility model, the electric focusing mechanism includes a focusing motor bracket 18 installed on the focusing lens barrel. A focusing motor 19 is installed on the focusing motor bracket. A focusing motor gear 20 is installed on the main shaft of the focusing motor. The focusing motor gear meshes with a focusing ring 16 arranged on the outer periphery of the focusing lens barrel to drive the focusing ring to rotate. A focusing potentiometer 22 is arranged beside the focusing motor. A focusing potentiometer gear 21 of the focusing potentiometer meshes with the focusing motor gear. Micro switches 13 for limiting the stroke are also arranged on both sides of the focusing motor bracket.

[0044] The lens has a pulling defocus function. To ensure the utilization rate of the potentiometer within the effective focusing range, the guide groove of the focusing ring is divided into two ends with different slopes. The slope of the effective focusing range is small and the rotation range is large. The slope of the pulling defocus section is large and the rotation angle is small.

[0045] In the embodiment of the present utility model, a shutter 23 for background correction is arranged at the rear end of the rear lens barrel. The shutter is driven by a motor 24 installed outside the rear lens barrel. A stop pin 25 for limiting the shutter is also installed outside the rear lens barrel.

[0046] In the embodiment of the present utility model, a camera bracket 27 is arranged behind the rear lens barrel. The camera bracket is connected to the rear lens barrel through a bottom plate 26. An auxiliary support frame 28 is also arranged between the rear lens barrel and the camera bracket.

[0047] Holes for connecting to the base plate are provided at the bottom of the main lens barrel and the rear lens barrel, and the whole is fixedly connected to the camera mount with a detector through the base plate. Triangular stiffeners are provided on the base plate to eliminate the influence caused by too long a cantilever.

[0048] In the embodiment of the present utility model, to achieve light weight, the base plate, the camera mount, and the auxiliary support frame are all made of carbon fiber material. Compared with aluminum alloy, carbon fiber has higher strength and lighter weight. From the perspective of the compressive strength of the material, the data of carbon fiber is 200 (GNm^-2), and the data of aluminum alloy is between 69 and 79. The weight of carbon fiber is about 2 / 3 of that of aluminum alloy. Using carbon fiber material for the support structure can greatly reduce the overall weight of the lens without affecting the lens performance.

[0049] The optical structure composed of the above lens groups reaches the following optical indicators: relative aperture F: 2.0; resolution: can be adapted to a 640*512 15μm mid-wave cooled detector camera; applicable spectral line range: 7.7μm - 9.3μm.

[0050] In the embodiment of the present utility model, optical glass materials with high refractive index and low dispersion are selected. Through design and optimization, various aberrations of the optical lens are corrected, enabling the lens to achieve advantages such as high resolution, large relative aperture, and low distortion; the distortion is small, less than 3%, and there is better control of the distortion compared to the old structure; in the optical design, through the optimized design of the cam curve, the optical axis drift during the zooming process is effectively controlled, and the imaging quality is excellent within the full focal length range.

[0051] For any of the technical solutions disclosed in the above present utility model, unless otherwise stated, if it discloses a numerical range, then the disclosed numerical range is the preferred numerical range. Any person skilled in the art should understand that the preferred numerical range is only the numerical values with obvious technical effects or representativeness among many implementable numerical values. Since there are too many numerical values to enumerate, the present utility model only discloses some numerical values to illustrate the technical solutions of the present utility model, and the above-listed numerical values should not constitute a limitation to the protection scope of the present invention.

[0052] Meanwhile, for the above present utility model, if it discloses or involves components or structural parts that are fixedly connected to each other, then, unless otherwise stated, the fixed connection can be understood as: a detachable fixed connection (such as using bolts or screws for connection), or it can also be understood as: a non-detachable fixed connection (such as riveting, welding). Of course, the mutually fixed connection can also be replaced by an integral structure (such as manufactured by integral forming using casting technology) (except when it is obviously impossible to adopt the integral forming process).

[0053] If terms such as "first" and "second" are used in this text to define components, those skilled in the art should be aware that the use of "first" and "second" is merely for the convenience of distinguishing components in description. Without additional statements, these terms have no special meaning.

[0054] In addition, for any technical solution disclosed in the present utility model, the terms used to represent positional relationships or shapes, unless otherwise stated, include states or shapes that are approximate, similar, or close to them.

[0055] Any component provided by the present utility model can either be assembled from multiple separate components or be a single component manufactured by an integral forming process.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present utility model and are not intended to limit them; although the present utility model has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that it is still possible to modify the specific implementation manners of the present utility model or perform equivalent replacements for some technical features; without departing from the spirit of the technical solutions of the present utility model, they should all be covered within the scope of the technical solutions claimed by the present utility model.

Claims

1. A medium-wave infrared lens, characterized in that: The lens barrel comprises a front fixed group with positive optical power, a variable power group with negative optical power, a compensation group with positive optical power, a focusing group with negative optical power and a rear fixed group, wherein the rear fixed group is composed of a first lens with positive optical power, a second lens with negative optical power and a third lens with positive optical power.

2. A medium-wave infrared lens according to claim 1, characterized in that: The air space between the front fixed group and the zoom group is 18.01 mm, the air space between the zoom group and the compensation group is 6.81 mm, the air space between the compensation group and the focusing group is 4.53 mm, the air space between the focusing group and the first lens of the rear fixed group is 10.47 mm, the air space between the first lens and the second lens is 0.95 mm, and the air space between the second lens and the third lens is 0.2 mm.

3. The medium-wave infrared lens according to claim 1, characterized in that: The lens barrel includes a main lens barrel, a focusing lens barrel and a rear lens barrel. The front fixed group is installed inside the front section of the main lens barrel, a zoom slide for installing a zoom group is provided inside the middle section of the main lens barrel, a compensation slide for installing a compensation group is provided inside the rear section of the main lens barrel, the focusing group is installed inside the focusing lens barrel, the rear fixed group is installed inside the rear lens barrel, an electric zoom mechanism is provided outside the main lens barrel, and an electric focusing mechanism is provided outside the focusing lens barrel.

4. The medium-wave infrared lens according to claim 3, characterized in that: The electric zoom mechanism includes a zoom motor frame installed outside the main lens barrel, a zoom motor is installed on the zoom motor frame, the output shaft of the zoom motor is provided with a zoom motor gear, a zoom cam meshing with the zoom motor gear is provided outside the main lens barrel, a potentiometer is provided next to the zoom motor, the potentiometer gear of the potentiometer is precisely meshed with the motor gear, and a micro switch for limiting the stroke is also provided on the main lens barrel; the zoom cam is fastened with a zoom pressure ring, a zoom groove and a compensation groove are provided on the zoom cam, cam guide pins are provided in the zoom groove and the compensation groove, the cam guide pin located in the zoom groove is slidably matched with the zoom groove and is connected to the zoom slide, and the cam guide pin located in the compensation groove is slidably matched with the compensation groove and is slidably matched with the compensation slide.

5. The medium-wave infrared lens according to claim 3, characterized in that: The electric focusing mechanism includes a focusing motor frame installed on the focusing barrel, a focusing motor is installed on the focusing motor frame, a focusing motor gear is installed on the main shaft of the focusing motor, the focusing motor gear is meshed with a focusing ring arranged on the outer periphery of the focusing barrel to drive the focusing ring to rotate, a focusing potentiometer is arranged next to the focusing motor, the focusing potentiometer gear of the focusing potentiometer is meshed with the focusing motor gear, and micro switches for limiting the stroke are also arranged on both sides of the focusing motor frame.

6. The medium-wave infrared lens according to claim 3, characterized in that: A baffle for background correction is arranged at the rear end of the rear lens barrel, and the baffle is driven by a motor installed outside the rear lens barrel. A baffle nail for limiting the baffle is also installed outside the rear lens barrel.

7. The medium-wave infrared lens according to claim 3, characterized in that: A camera frame is arranged behind the rear lens barrel, the camera frame and the rear lens barrel are connected via a bottom plate, and an auxiliary support frame is also arranged between the rear lens barrel and the camera frame.

Images