KR100704403B1 - Lens optical system for thermal sensing device of compact using aspherical - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens optical system for a micro thermal sensor using an aspherical surface. The present invention provides a concave surface having a negative refractive power on an object side, a convex surface having a positive refractive power on an object side, and a positive power ratio as a whole. A first lens forming a light; A second lens disposed behind the first lens to form a concave surface having an object-side negative refractive power, a convex surface having an image-positive positive refractive power, and overall forming a positive ((+) Power] magnification; A third lens disposed at the rear of the second lens and configured to prevent the protection of the thermal sensor disposed at the front of the image and to prevent foreign substances from entering the sensor; Technical features of the configuration including an aperture fixed / arranged in front of the first lens.

According to the present invention, it is possible not only to greatly improve the thermal infrared transmittance, but also to improve the accuracy of heat detection, to improve the image quality and to increase the brightness, and to realize the miniaturization of the device as well as more stable optical performance. do.

Description

LENS OPTICAL SYSTEM FOR THERMAL SENSING DEVICE OF COMPACT USING ASPHERICAL}

1 is a cross-sectional view showing the arrangement of the lens optical system for the ultra-small thermal sensor according to the present invention.

2 (a) and 2 (b) are cross-sectional views comparing the radius of curvature of the aspherical lens and the reference spherical lens of FIG.

Figure 3 is a thermal infrared tracking analysis of the lens optical system for a small thermal sensor according to the present invention.

4 to 8 are analysis graphs showing optical characteristics of the lens optical system according to the present invention.

Figure 4 is a graph showing the meridional surface curvature and curvature image surface curvature on various optical axes,

5 is a graph of aberration analysis regarding astigmatism,

6 is a graph showing the distortion of the screen in percentage;

7 is a graph illustrating chromatic aberration,

8 is a graph analyzing the optical performance of MTF (Modulation Transfer Functions) meaning the resolution.

Explanation of symbols on the main parts of the drawings

110: first lens 120: second lens

130: third lens 140: aperture

The present invention relates to a lens optical system for an ultra-small thermal sensor using an aspherical surface, and more particularly, it is possible to miniaturize the device and to increase the thermal infrared transmittance to ensure the accuracy of thermal sensing, and to improve image quality and increase brightness. It relates to a lens optical system for an ultra-small heat sensing device using an aspherical surface to be implemented.

In general, lens optics are an important component of a device that functions to characterize the performance of the device and the device being applied.

Although the lens optical system is composed of one lens, recently, the development of functional lenses for removing or compensating aberration generated in the lens itself due to the development of technology has led to the increase in the number of complex lens optical systems that combine appropriately many of them. Is being applied.

In particular, in the field of digital cameras where the priority is to miniaturize devices and improve image quality, such functional lens optical systems are already becoming the mainstream, and heat detection that detects / detects heat of a human body or an object by detecting infrared heat through infrared transmission. In the field of devices, in order to improve its functionality, the combination lens optical system is attempted to be applied, and examples thereof include a surveillance camera, a non-contact thermometer, an infrared detector, and the like.

By the way, the lens optical system for a heat sensing device according to the prior art has a problem that it is difficult to realize the miniaturization of the device until now, and the improvement of transmittance, image quality and increase of brightness are required to improve the functionality suitable for the use of the device. It is true.

An object of the present invention is to enable the miniaturization of the device and to increase the thermal infrared transmittance to ensure the accuracy of the heat detection, and to use the aspherical lens for the ultra-small heat sensing device to realize the improvement of the image quality and the increase of the brightness It is to provide an optical system.

Furthermore, it is to provide an optical system for a micro thermal sensor using an aspherical surface that can exhibit more stable and improved optical performance.

The present invention for achieving the above object to form a concave surface having a negative refractive power of the object side, a convex surface having a positive refractive power of the image side and a first lens to form a magnification of the positive ((+) Power] as a whole Wow; A second lens disposed behind the first lens to form a concave surface having negative refractive power on the object side, a convex surface having positive refractive power on the image side, and forming a positive ((+) Power] power as a whole; ; A third lens disposed at the rear of the second lens and configured to prevent the protection of the thermal sensor disposed at the front of the image and to prevent foreign substances from entering the sensor; Technical features of the configuration including an aperture fixed / arranged in front of the first lens.

The first lens is composed of an aspherical lens having the convex surface of the second surface aspheric, the first lens and the second lens using germanium (Ge) as an optical material, the third lens is zinc sulfide ( ZnS) is used as an optical material.

In addition, the lens optical system satisfies 1.0 ≤ B / f ≤ 2.4 when the focal length is f and the rear focal length is B.

In addition, when the distance from the first lens to the second lens is referred to as the optical length T, and the focal length is f, T / f ≦ 1.1 is satisfied.

Further, when an aspherical surface is formed on the convex surface of the first lens, the sag by the aspherical surface is Xa, and the sag by the reference spherical surface is Xo, Xo-Xa> 0 [the second surface of the aspherical first lens ( R2)].

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings and diagrams.

1 is a view showing the arrangement of the lens optical system for the ultra-small thermal sensor according to the present invention.

As shown in FIG. 1, the microlens lens optical system using the aspherical surface according to the present invention includes a first lens 110 to a third lens 130 and an aperture 140 between an object side and an image side on which an image of the object is formed. An optical system comprising: a first concave surface R1 having negative refractive power on an object side, a convex surface R2 having positive refractive power on an object side, and a first magnification of positive ((+) Power] as a whole; A lens 110 and a concave surface R3 disposed at the rear of the first lens 110 to form a concave surface R3 having negative refractive power on the object side and a convex surface R4 having a positive refractive power on the image side are formed. The second lens 120 forming a magnification of (+) Power, the protection of the thermal sensor 1 disposed behind the second lens 120 and disposed in front of the image, and the foreign matter toward the sensor 1 side. Cooking that is fixed / arranged in front of the third lens 130 and the first lens 110 to prevent the inflow, etc. Dog 140.

The first lens 110 is composed of an aspherical lens having aspherical a second surface, which is a convex surface R2.

The first lens 110 and the second lens 120 induces the refraction of the infrared rays, that is, to be able to perform the accurate detection of the infrared heat by refracting the incident infrared rays to the center and the periphery. It is preferable to use germanium (Ge) having an optical material.

The third lens 130 is composed of a glass lens having a planar shape having both surfaces R5 and R6 in a planar shape, and an optical material of zinc sulfide (ZnS) to increase infrared transmittance to the thermal sensor 1. It is preferable to use.

Here, the first lens 110 functions to adjust the magnification as a whole, and to correct spherical aberration by forming an aspherical surface of the second surface R2.

The second lens 120 has a main function of correcting distortion, and serves to adjust infrared rays incident to the heat sensor 1.

The third lens 130 serves as a cover glass to protect the heat sensor 1.

As described above, the lens optical system for the ultra-small heat sensing device using the aspherical surface according to the present invention is configured to implement the improvement of the transmittance and the brightness by arranging the lenses in the normal direction in which thermal infrared rays are incident. Is designed.

[Condition 1]

1.0 ≤ B / f ≤ 2.4

Here, the focal length of the lens system of the first lens 110 and the second lens 120 is f, and the rear focal length from the fourth surface R4 of the second lens 120 to the focal point ( The back focal length is called B.

[Condition 2]

T / f ≤ 1.1

Here, the distance from the center of the object side of the first first lens 110 to the image center of the second second lens 120 is referred to as the optical length T and the focal length is f.

[Condition 3]

Xo-Xa> 0 [second surface R2 of the aspherical first lens]

Here, the height at the optical axis is Y on the plane where the curvature on the optical axis of the reference spherical surface is C (= 1 / R), and the absolute value of the reference spherical sag is Xo, and the reference aspherical sag ( The absolute value of Sag) is called Xa.

Next will be described the operation of the lens optical system according to the present invention implemented to satisfy the above conditions (conditions 1 to 3).

FIG. 2 is a diagram showing Sag Xa in the aspherical surface and Sag Xo in the spherical surface when the height of the optical is Y in the plane where the curvature on the optical axis of the reference sphere is C (= 1 / R). Sag Xo in the spherical lens and sag Xa in the aspherical lens may be represented by Equations 1 and 2 below.

[Equation 1]

[Equation 2]

Where C is the curvature (C = 1 / R; R is the radius of the lens), Y is the height, K is the conic constant, and AD, AE, AF, and AG represent aspherical coefficients, respectively.

When the lens optical system is configured to satisfy the above conditions 1 and 2 through the above equation, the optical field T is 24.1 mm, the aperture ratio f / dl is F / 1.5, and the angle of view is 47.08 degrees. do.

In addition, Table 1 shows the data values of the optical system according to the present invention, and shows the curvature radius, the center interval, the refractive index, and the dispersion rate of the lens.

                             Intensity of light (FNO) 1: 1.5 Focal length (f) 24.05 View angle (W) 47.08 Lens surface Radius of curvature (r) Thickness and spacing (d) Refractive index (Nd) Dispersion Rate (Vd) Remarks iris ∞ 0.640 1.0000 First side (R1) -63.60 6.000 4.0028 779.56 Ge 2nd side (R2) -57.42 11.22 1.0000 Aspheric surface Page 3 (R3) -57.00 9.000 4.0028 779.56 Ge Fourth side (R4) -38.16 20.05 1.0000 Page 5 (R5) ∞ 3.000 2.1922 16.986 ZnS Page 6 (R6) ∞ 4.000 1.0000 Image plane ∞ _ _ sensor

Here, K = 0.0, AD = 4.191521511e-06, AE = 1.010649504e-07, AF = -1.244402491e-09, AG = 6.116048791e-12 on the second surface R2.

     This invention is a focal length f of the entire lens system, a rear focal length B, the first of the lens system by the resolution measurement, the effective diameter (dl: mm), the angle of view measurement, the spherometer (SPHEROMETER) measured by the projection measuring instrument (RROFELE PROJECTOR) As a result of analyzing the distance T from the first first lens 110 to the second second lens 120, sag Xo by spherical surface, and sag Xa by aspherical surface, the lens shape and lens arrangement of the optical system are as described above. It can be seen that conditions 1, 2, and 3 are satisfied.

That is, [condition 1] 1.0 ≦ B / f ≦ 2.4; [Condition 2] T / f ≦ 1.1; [Condition 3] Xo-Xa> 0 is satisfied.

Therefore, the lens optical system for the ultra-small heat sensing device using the aspherical surface according to the present invention exhibits optical performance of 24.1mm optical field length, F / 1.5 of aperture ratio, 47.08 degree of viewing angle, and increases brightness and image quality by improving transmittance of thermal infrared rays. It not only has the properties to improve the performance, but also enables the super compact of the device.

On the other hand, Figure 3 is a thermal infrared trace analysis of the micro-lens thermal sensor optical system according to the present invention, Figures 4 to 8 is an analysis graph showing the optical characteristics of the lens optical system for a small thermal sensor according to the present invention.

Here, FIG. 4 illustrates aberration characteristics, and the meridian image curvature and the curvature image curvature are shown on the optical axis of 0.50, 0.71, and 1.00, FIG. 5 is an aberration analysis regarding astigmatism, and FIG. It is about accuracy (distortion aberration), Figure 7 shows the chromatic aberration (solid line) and percent distortion (dotted line), Figure 8 is an analysis of the optical performance of MTF (Modulation Transfer Functions) means the resolution.

As shown in FIG. 3 to FIG. 8, the lens optical system according to the present invention shows that the values of images in almost all fields are adjacent to the central axis, indicating that the spherical aberration, the meridian aberration, and the chromatic aberration are corrected. Of course, MTF (Optical Requirements / Resolution) is satisfied.

Therefore, through the structure in which the lens is arranged in the direction of the normal infrared ray incident and the convex surface aspherical surface, it is possible to further improve the brightness of not only the center but also the surroundings, and a very effective design for improving the image quality and miniaturization is achieved. You can lose.

As described above, according to the lens optical system for the ultra-small heat sensing device using the aspherical surface according to the present invention, the optical performance of the optical field length 24.1mm, aperture ratio F / 1.5, 47.08 degrees clock angle.

The present invention provides an optical system for arranging first to third lenses including cover glass for protecting a thermal sensor, and arranging in a normal direction in which thermal infrared rays are incident, and forming an aspherical surface on the convex surface of the first lens. In addition, the thermal infrared transmittance can be greatly improved, and the accuracy of heat detection can be ensured, and it has a useful effect of leading to the improvement of image quality and the increase of brightness.

Furthermore, it is possible to miniaturize the device and to exhibit more stable and improved optical performance.

Claims (7)

A first lens forming a concave surface having an object-side negative refractive power, a convex surface having an image positive refractive power, and forming a magnification of positive [(+) Power] as a whole; A second lens disposed behind the first lens to form a concave surface having an object-side negative refractive power, a convex surface having an image-positive positive refractive power, and overall forming a positive ((+) Power] magnification; A third lens disposed at the rear of the second lens and configured to prevent the protection of the thermal sensor disposed at the front of the image and to prevent foreign substances from entering the sensor; A lens optical system for a miniature heat sensing device using an aspherical surface, characterized in that it comprises a stop that is fixed / arranged in front of the first lens. The method of claim 1, The first lens is a lens optical system for a small thermal sensor using an aspherical surface, characterized in that the aspherical lens having a convex surface of the second surface aspheric. The method of claim 1, The first lens and the second lens is a lens optical system for a micro thermal sensor using aspherical surface, characterized in that for the accurate detection of infrared heat using germanium (Ge) as an optical material. The method of claim 1, The third lens is composed of a glass lens having a planar configuration having a double-sided planar shape, and is made of an aspherical surface using zinc sulfide (ZnS) as an optical material to increase infrared transmittance to a thermal sensor. Lens optics for thermal sensors. The method of claim 1, If the focal length is f and the rear focal length is B, 1.0 ≤ B / f ≤ 2.4 Lens optical system for an ultra-small thermal sensor using an aspherical surface, characterized in that to satisfy the. The method of claim 1, When the distance from the first lens to the second lens is called the optical length T and the focal length is f, T / f ≤ 1.1 Lens optical system for an ultra-small thermal sensor using an aspherical surface, characterized in that to satisfy the. The method of claim 1, If an aspherical surface is formed on the convex surface of the first lens, the sag by the aspherical surface is Xa, and the sag by the reference spherical surface is Xo, Xo-Xa> 0 [second surface R2 of the aspherical first lens] Lens optical system for an ultra-small thermal sensor using an aspherical surface, characterized in that to satisfy the.

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