WO2016190625A1 - Wide-field-of-view athermalization infrared lens module - Google Patents

Abstract

The present invention relates to a wide-field-of-view athermalization infrared lens module in which an infrared optical system of a thermal imaging device stably maintains a focal length in a wide temperature range through a combination of germanium and chalcogenide lenses. The lens module comprises: a lens system consisting of a first lens, a second lens, a third lens and a fourth lens; and an aperture disposed between the second lens and the third lens, wherein the first lens is provided with a convex surface (R1) having a positive refractive force on an object side, and with a concave surface (R2) having a negative refractive force on an upper side thereof, and is formed with a negative magnification as a whole; the second lens is provided, while disposed in the rear side of the first lens, with a convex surface (R3) having a positive refractive force on an object side, and with a concave surface (R4) having a negative refractive force on an upper side thereof, and is formed with a positive magnification as a whole; the third lens is provided, while disposed in the rear side of the second lens, with a concave surface (R5) having a negative refractive force on an object side, and with a concave surface (R6) having a negative refractive force on an upper side thereof, and is formed with a positive magnification as a whole; the fourth lens is provided, while disposed in the rear side of the third lens, with a convex surface (R7) having a positive refractive force on an object side, and with a concave surface (R8) having a negative refractive force on an upper side thereof, and is formed with a positive magnification as a whole; and the first lens is made of a germanium material, and the second lens, the third lens and the fourth lens are made of a chalcogenide material.

Description

Wide field deteriorated infrared lens module

The present invention relates to a wide-field non-degradable infrared lens module, and more particularly, to an infrared optical system of a thermal imaging device, a wide-field non-degraded infrared ray in which a focal length is stably maintained over a wide temperature range through a combination of germanium and chalcogenide lenses. It relates to a lens module.

In general, thermal imaging equipment is a device that detects and displays infrared rays emitted by a person or an object, through which the position and dynamics of the person or the object may be grasped at night or in the absence of light.

However, infrared rays have poor transmittance due to the low transmittance of ordinary glass lenses, and thus infrared infrared lenses made of materials such as germanium (Ge), zinc sulfide (ZnS), and zinc selenide (ZnSe) are employed. The refractive index changes with temperature and the dispersibility of the material is relatively small compared to the materials used in the visible region.

In other words, the optical performance of thermal imaging equipment is sensitive to temperature changes, so it is not a big problem when used in a narrow temperature range near room temperature, but non-degradation compensation is required when the driving temperature range is wide. There is an optical method of compensating by a combination of a mechanical method and a functional lens.

<Patent Documents>

(Patent Document 1) KR 10-1214601 B1 2012.12.14.

The problem to be solved by the present invention is to provide a wide-field non-degradable infrared lens module with a small focal length fluctuation in a wide temperature range and aberration is minimized through lens combinations of different materials and surface shapes.

The wide-field non-degradable infrared lens module of the present invention for solving the above problems is a lens system consisting of a first lens, a second lens, a third lens and a fourth lens, and an aperture disposed between the second lens and the third lens. The first lens has a convex surface R1 having a positive refractive power on the object side, and a concave surface R2 having a negative refractive power on the image side, and is formed at a negative magnification as a whole. The second lens has a convex surface R3 having a positive refractive power on an object side in a state disposed behind the first lens, and a concave surface R4 having a negative refractive power on an image side. It is generally formed at a positive magnification, and the third lens has a concave surface R5 having a negative refractive power on an object side in a state disposed behind the second lens, and a concave having a negative refractive power on an image side. Plane R6 is formed, and overall, The fourth lens has a convex surface R7 having a positive refractive power on an object side and a concave surface R8 having a negative refractive power on an image side, while being disposed behind the third lens. The first lens is made of germanium, and the second lens, the third lens, and the fourth lens are made of chalcogenide.

In addition, the wide-field non-degradable infrared lens module of the present invention, the second lens, the third lens and the fourth lens, germanium (Ge)-selenium (Se)-tellurium (Te) -based chalcogenide lens, germanium- An arsenic (As) -selenium-based chalcogenide lens or a germanium-arsenic-selenium-tellurium-based chalcogenide lens is selectively employed.

In the wide-field non-deteriorated infrared lens module of the present invention, the first lens has an object-side convex surface R1 having a spherical surface, and the image-side concave surface R2 of the first lens except the convex surface R1. And both surfaces (R3 ~ R8) of the remaining lens is characterized in that made of aspherical surface.

In addition, the wide-field undeteriorated infrared lens module of the present invention is characterized by satisfying the condition 1 below.

[Condition 1]

Zo1> 0 [Spherical lens of the first lens (R1)]

Za2> 0 [Aspherical surface (R2) of first lens]

Za3> 0 [Aspherical surface (R3) of second lens]

Za5 <0 [Aspherical surface (R5) of third lens]

Za6 <0 [Aspherical surface (R6) of third lens]

Za8 <0 [Aspherical surface (R8) of fourth lens]

In addition, the wide field undeteriorated infrared lens module of the present invention is characterized in that the F number is in the range of 1.0 to 1.5.

According to the wide-field non-degradable infrared lens module of the present invention, the change of focal length is minimized in a wide temperature range through the first lens made of germanium and the second lens, third lens, and fourth lens made of chalcogenide material. In addition, since aberration such as chromatic aberration is minimized through the combination of the shape and refractive power of each lens, the utility of the present invention and the ease of use of the equipment employing the same may be increased.

1 is a schematic view showing a lens array state of the wide field undeteriorated infrared lens module according to the present invention.

2 is a view showing a temperature-specific MTF curve for one embodiment of a wide field undeteriorated infrared lens module according to the present invention.

3 is a diagram illustrating a ray aberration of an embodiment of a wide field undeteriorated infrared lens module according to the present invention;

Figure 4 shows a spot diagram of an embodiment of a wide field undeteriorated infrared lens module according to the present invention.

FIG. 5 is a diagram illustrating distortion aberration for one embodiment of a wide-field undeteriorated infrared lens module according to the present invention. FIG.

6 is a view showing an MTF curve for an embodiment of a wide field undeteriorated infrared lens module according to the present invention.

7 is a view showing a condensing state of a wide-field undeteriorated infrared lens module according to the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic view showing a lens arrangement of the wide field undeteriorated infrared lens module according to the present invention. Referring to FIG. 1, an infrared lens module of the present invention includes a lens system including a first lens 10, a second lens 20, a third lens 30, and a fourth lens 40, and the second lens 20. ) And the aperture 50 disposed between the third lens 30.

The first lens 10 has a convex surface R1 having a positive refractive power on an object side, a concave surface R2 having a negative refractive power on an image side, and is generally formed at a negative magnification.

In addition, the first lens 10 preferably has a high refractive index so as to adjust the light of thermal infrared rays, and is resistant to impact due to the characteristics exposed to the external environment, and employs a germanium lens without heavy metal exposure during processing. It is desirable to.

The second lens 20 has a convex surface R3 having a positive refractive power on an object side in a state disposed behind the first lens 10, and a concave surface R4 having a negative refractive power on an image side. ) Is formed and is formed at a positive magnification as a whole.

The third lens 30 has a concave surface R5 having negative refractive power on an object side in a state disposed behind the second lens 20, and a concave surface R6 having negative refractive power on an image side. ) Is formed and is formed at a positive magnification as a whole.

The fourth lens 40 has a convex surface R7 having a positive refractive power on an object side in a state disposed behind the third lens 30, and a concave surface R8 having a negative refractive power on an image side. ) Is formed and is formed at a positive magnification as a whole.

The second lens 20, the third lens 30, and the fourth lens 40 employ a chalcogenide lens in which chalcogen, germanium, and the like are combined. The chalcogenide is also used as a high refractive lens. Infrared light can be adjusted, in particular, low cost and excellent processability, there is an advantage that can lower the manufacturing cost of the thermal imaging equipment employing the lens module of the present invention.

Specifically, the second lens 20, the third lens 30, and the fourth lens 40 are germanium (Ge) -selenium (Se) -telelium (Te) -based chalcogenide lens, germanium-arsenic ( As) -selenium-based chalcogenide lenses or germanium-arsenic-selenium-tellurium-based chalcogenide lenses may optionally be employed.

The diaphragm 50 is disposed between the second lens 20 and the third lens 30, but is disposed close to the third lens 30, the light incident from the second lens 20 It functions to selectively converge.

Hereinafter, the design of the lens module according to the present invention will be described in detail.

The object-side convex surface R1 of the first lens 10 has a spherical surface, and the image-side concave surface R2 of the first lens 10 except for the object-side convex surface R1 and both surfaces of the residual lens ( R3 to R8) are all composed of aspherical surfaces.

In addition, if the F-number (effective focal length / incident pupil size) is less than 1.0, the diameters of the lenses 10, 20, 30, and 40 become large, so that the correction of aberration is difficult. The apertures of 20, 30, and 40 become smaller, so that the correction of the number becomes easier, but it becomes difficult to collect the light required by the sensor. Therefore, the lens module of the present invention is designed so that the number of F is in the range 1.0 ~ 1.5.

Meanwhile, the spherical surface R1 of the first lens has a sag Zo value calculated by Equation 1 below, and the other lens aspherical surfaces R2 through R8 have the sag Za value calculated by Equation 2 below. The design is made to satisfy condition 1.

[Condition 1]

Zo1> 0 [Spherical lens of the first lens (R1)]

Za2> 0 [Aspherical surface (R2) of first lens]

Za3> 0 [Aspherical surface (R3) of second lens]

Za5 <0 [Aspherical surface (R5) of third lens]

Za6 <0 [Aspherical surface (R6) of third lens]

Za8 <0 [Aspherical surface (R8) of fourth lens]

[Equation 1]

[Equation 2]

Here, C denotes a curvature (C = 1 / R, R denotes a radius of curvature of the lens), Y denotes a lens height, and A, B, C ', and D denote aspherical coefficients determined according to lens materials.

In addition, Table 1 below is the basic data of the lens module satisfying the condition 1, the optical field (OAL): 53 mm, the aperture ratio (FNO): F / 1.3, the focal length (f): 5.44 mm, the horizontal angle of view ( w): 90 °, the refractive index (Nd) and the second lens 20, the third lens 30, the fourth lens 40 for the germanium lens manufactured by Success Infrared of China as the first lens 10 As the chalcogenide lens, the refractive index (Nd) of the IG6 lens developed by Vitron of Germany is adopted.

In addition, Table 2 is a coefficient value of the aspherical surface of the lens module of Table 1.

Lens surface	Bending Radius (R)	Thickness, thickness (d)	Refractive index (Nd)	Remarks
First side (R1)	45.777	3.50	4.003073	Spherical
2nd side (R2)	20.185	14.77	-	Aspheric surface
Page 3 (R3)	23.948	8.69	2.778100	Aspheric surface
Fourth side (R4)	83.720	7.48	-	Aspheric surface
iris	-	1.94	-	-
Page 5 (R5)	-11.669	5.09	2.778100	Aspheric surface
Page 6 (R6)	-11.657	2.53	-	Aspheric surface
Page 7 (R7)	82.448	9.00	2.778100	Aspheric surface
8th page (R8)	-33.273	5.00	-	Aspheric surface

Lens surface	A	B	C '	D
2nd side (R2)	-0.293058E-04	0.424897E-07	-0.123090E-09	-
Page 3 (R3)	-0.211321E-04	-0.367776E-08	-0.122402E-09	-
Fourth side (R4)	-0.159484E-04	-0.376906E-07	0.446695E-10	-
Page 5 (R5)	-0.272702E-03	0.437197E-05	-0.248986E-07	-
Page 6 (R6)	0.114156E-03	-0.105147E-06	0.842029E-08	-
Page 7 (R7)	0.204030E-03	-0.177893E-05	0.100941E-07	-0.340879E-10
8th page (R8)	0.122776E-03	-0.851284E-07	-0.669398E-08	0.231370E-10

2 to 7 is an analysis graph showing the optical characteristics for the lens module consisting of the values of Table 1 and Table 2.

Specifically, FIG. 2 shows the MTF curve for each temperature calculated by infinitely the object distance. As shown in FIG. 2, when the limit frequency is 29mm / cycles at -32 degrees and +43 degrees, the MTF value is about 0.32. This value is equivalent to 80% or more of 0.4, which is an MTF value satisfying the specification, and indicates that an image having a good resolution can be obtained in a wide temperature range.

FIG. 3 shows ray aberrations calculated from infinite object distances, showing meridians and curves on the optical axis at 40.00 ° and 54.09 °.

4 is a spot diagram calculated by infinite object distance, which shows various aberrations, dividing the incident pupil into hundreds or thousands of meshes to track rays, and at each point on the object. The ray is traced with a mesh of, indicating the position of each ray as a spot on the top surface. In FIG. 4, the center three circles each represent a spot diagram for a field, and the more the points are dispersed from the center, the larger the aberration.

5 shows distortion aberrations calculated by infinite object distances, and shows the degree of curvature of the screen.

6 shows a Modulation Transfer Functions (MTF) curve having a resolution calculated at an infinite object distance. The MTF value is calculated to be 0.411 when the detector pixel size is 17 μm and the limit frequency is 29 mm / cycles. The value is considered to be good resolution.

As shown in Figs. 3 to 6, the lens module of the present invention shows the values of the images adjacent to the central axis in almost all fields, so that the corrected states of spherical aberration, meridian aberration and chromatic aberration are good, and appropriate resolution is achieved. It has a presence.

In addition, Figure 7 is a view showing a condensing state of the wide-field non-deteriorated infrared lens module according to the present invention, the lens module of the present invention is a double gauss lens in the form of an advantageous lens to minimize wide-angle, astigmatism, image curvature and distortion aberration It is provided in a modified form. Here, reference numerals a and b denote an imaging sensor and a sensor protection window, respectively.

Although the preferred embodiment of the present invention has been described above, the scope of the present invention is not limited thereto, and it should be understood that the scope of the present invention extends to the range that is substantially equivalent to the embodiment of the present invention. Various modifications can be made by those skilled in the art without departing from the spirit of the invention.

Claims (5)

1. A lens system including a first lens, a second lens, a third lens, and a fourth lens, and an aperture disposed between the second lens and the third lens,

   The first lens has a convex surface R1 having a positive refractive power on the object side, a concave surface R2 having a negative refractive power on the image side, and is formed at a negative magnification as a whole.

   In the state where the second lens is disposed behind the first lens, a convex surface R3 having a positive refractive power is formed on an object side, and a concave surface R4 having a negative refractive power is formed on an image side. Is formed at a positive magnification,

   In the third lens, the concave surface R5 having negative refractive power is formed on the object side and the concave surface R6 having negative refractive power is formed on the object side while being disposed behind the second lens. Is formed at a positive magnification,

   In the fourth lens, a convex surface R7 having a positive refractive power is formed on an object side in a state disposed behind the third lens, and a concave surface R8 having a negative refractive power is formed on an image side. Is formed at a positive magnification,

   The first lens is made of germanium material, the second lens, the third lens and the fourth lens is a wide-field non-deteriorated infrared lens module, characterized in that made of chalcogenide material.
2. The method of claim 1,

   The second lens, the third lens, and the fourth lens may include a germanium (Ge) -selenium (Se) -telelium (Te) -based chalcogenide lens, a germanium-arsenic (As) -selenium-based chalcogenide lens, or germanium. -Wide field non-degradable infrared lens module, characterized in that the arsenic- selenium- tellurium-based chalcogenide lens is selectively employed.
3. The method of claim 1,

   The first lens has an object-side convex surface R1 having a spherical surface, and the image-side concave surface R2 of the first lens except the convex surface R1 and both surfaces R3 to R8 of the remaining lens are aspherical. Wide field deteriorated infrared lens module, characterized in that made.
4. The method of claim 3, wherein

   Wide field undeteriorated infrared lens module, characterized in that to satisfy the following condition 1.

   [Condition 1]

   Zo1> 0 [Spherical surface of the first lens (R1)]

   Za2> 0 [Aspherical surface (R2) of first lens]

   Za3> 0 [Aspherical surface (R3) of second lens]

   Za5 <0 [Aspherical surface (R5) of third lens]

   Za6 <0 [Aspherical surface (R6) of third lens]

   Za8 <0 [Aspherical surface (R8) of fourth lens]

   Here, Zo represents the sag value of the spherical surface and Za represents the sag value of the aspherical surface.
5. The method of claim 4, wherein

   A wide field of view deteriorated infrared lens module, characterized in that the number of F is in the range of 1.0 to 1.5.

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