KR100838662B1 - Optical system for thermal sensing device of ultra compact using aspherical - Google Patents

Abstract

The present invention relates to an optical system for an ultra-small thermal sensor using an aspherical surface, in the optical system for a thermal sensor for detecting or detecting heat through the transmission of thermal infrared rays, to form a convex surface having a positive refractive power on the object side A first lens forming an aspherical concave surface having negative refractive power on the image side and having a positive magnification of the whole; A second lens disposed behind the first lens and having a concave surface having an aspherical surface having negative refractive power on an object side, a convex surface having a positive refractive power on an image side, and having a positive magnification as a whole; A lens; Disclosed is a technical configuration including an aperture disposed between the first lens and the second lens, in close proximity to the first lens, and including an aperture for selectively converging light incident from the first lens.

According to the present invention, by arranging in the aspherical surface of the first lens and the second lens, but arranged in the normal direction in which thermal infrared rays are incident, and using the high refractive physical property, the thermal infrared transmittance can be greatly improved and thermal infrared transmittance can be greatly improved. Not only can the accuracy of the detection be expected, it also has a useful effect that leads to the improvement of the image quality and the increase of the brightness. It has the optical performance of 17.2mm of optical length, F / 1.0 of aspect ratio and 40.6 degrees of viewing angle.

Description

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

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

2 (a) and 2 (b) are diagrams for explaining a sag of an aspherical lens of the optical system for an ultra-small thermal sensor according to the present invention.

Figure 3 is a thermal infrared trace analysis of the optical system for the ultra-small heat detection apparatus according to the present invention.

4 to 8 is an analysis graph showing the optical characteristics of the optical system for the ultra-small thermal sensor 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,

Figure 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: aperture 140: cover glass

150: thermal sensor

The present invention relates to an optical system for an ultra-small heat detection device that can be used very widely, such as for vehicles, surveillance cameras, or defense through thermal infrared detection, and more particularly, by using an aspherical surface and improving the shape and arrangement of the lens. Aspheric surface is designed to realize the improved performance, but to provide more stable optical performance, better thermal detection accuracy, higher image quality and higher brightness, and to pursue the miniaturization of the device. It relates to an optical system for an ultra-small heat sensing device used.

In general, the optical system is a component of a very important device that functions to characterize the performance of the device and the device to which it is applied.

This optical system is composed of a single normal lens, but recently, as the development of functional lenses for eliminating or compensating aberration generated in the lens itself due to the development of technology, a complex lens optical system that appropriately combines many of them is developed. Many have been 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 by detecting infrared heat through infrared transmission, it is possible to detect / detect heat of a human body or an object. In the field of thermal sensing devices, attempts have been made to incorporate complex lens optical systems to improve the functionality thereof. Examples of such thermal sensing apparatuses include surveillance cameras, non-contact thermometers, and infrared detectors.

By the way, the optical system for a thermal sensing device according to the prior art has a large number of lenses, or the shape of the lens is mainly limited to the spherical optical system, so that there are many limited factors such as miniaturization of the optical system as well as improvement in image quality and camera brightness.

In order to solve these problems, the present applicant has proposed a technique of applying a high refractive lens and reducing the number of lenses in Patent Application No. 10-2005-86526.

However, when manufacturing the lens of the thermal sensor optical system, there is still a problem that the manufacturing method by the polishing method (Polishing Methode), and the material of the thermal sensor lens for high refractive properties containing a large amount of heavy metals such as zinc or sulfur. As a result, the manufacturing time of the optical system is long or there is a problem in that there is a work environment in which exposure of heavy metals is inevitable.

In addition, in recent years, high refractive index special lenses have been applied to improve the functionality of the optical system. However, since the material cost of the lens for high refractive index is high and the processing by polishing is performed, the manufacturing cost of the optical system is high and the use range is extremely high. There is a high possibility of being limited and mass production is impossible.

The object of the present invention is to use the aspherical surface and to improve the shape and arrangement of the lens to realize the improvement of optical performance, but to achieve a more stable optical performance than the conventional as well as the accuracy of thermal detection and to improve the image quality And to provide an optical system for an ultra-small thermal sensing device using an aspherical surface to enable the increase in brightness and to reduce the optical field to pursue the miniaturization of the device.

In addition, the present invention in the construction of the optical system to eliminate the lens production method by the conventional polishing process by applying a molded lens to create an environment-friendly working environment to avoid the exposure of heavy metals and a large amount of optical system required by the market The present invention provides an optical system for an ultra-small thermal sensing device using aspherical surface that can expect additional benefits such as production and cost saving effect.

The present invention for achieving the above object in the optical system for detecting or detecting heat through the transmission of thermal infrared rays, forming a convex surface having a positive refractive power on the object side and negative refractive power on the upper side A first lens forming a concave surface having an aspherical surface having a total power of positive [(+) Power]; A second lens disposed behind the first lens and having a concave surface having an aspherical surface having negative refractive power on an object side, a convex surface having a positive refractive power on an image side, and having a positive magnification as a whole; A lens; The diaphragm may be disposed between the first lens and the second lens, and arranged closely to the first lens, and include an aperture to selectively converge light incident from the first lens.

In this case, the first lens and the second lens are preferably composed of a chalcogenide lens having a high refractive index and a good thermal infrared transmittance, and in particular, germanium (Ge) -selenium (Se) -tellurium (Te). ) Chalcogenide Lens or Germanium (Ge) -arsenic (As) -Selenium (Se) Chalcogenide Lens or Germanium (Ge) -arsenic (As) -Selenium (Se) -Telium (Te) Chalcogen It is composed of any one selected from the cargo lens.

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 a small thermal sensor according to the present invention.

As shown in FIG. 1, the optical system for an ultra-small heat sensing device using an aspherical surface according to the present invention uses an aspherical surface and arranges lenses in a normal direction in which thermal infrared rays are incident to improve transmittance and increase brightness. A lens system formed of two aspherical lenses 110 and 120 between an object side and an image side where the image is formed, an aperture 130, a cover glass 140, and a thermal sensor 150 are provided. Consists of the configuration.

The lens system forms a convex surface R1 having positive refractive power on an object side, and a concave surface R2 having negative refractive power on an image side, and includes a first lens having a positive ((+) Power] power as a whole. And a concave surface R3 disposed on the rear side of the first lens 110 and having a negative refractive power on the object side, and a convex surface R4 having a positive refractive power on the image side. And a second lens 120 having a magnification of (+) Power.

At this time, the first lens 110 is composed of an aspherical lens having a concave second surface (R2) as an aspherical surface, the second lens 120 is a concave surface having a third surface (R3) as an aspherical surface. It consists of aspherical lens.

The first lens 110 and the second lens 120 is preferably composed of a special lens having a high refractive index so as to adjust the light of the thermal infrared rays, in particular a physical property that can be produced by molding while exhibiting a high refractive index It is desirable to have a low-cost chalcogenide lens that has not only heavy metal exposure but also heavy metal exposure.

More specifically, the first lens 110 and the second lens 120 are germanium (Ge) -selenium (Se) -telelium (Te) -based chalcogenide lens, germanium-arsenic (As) -selenium-based knife Cogenide lens, germanium-arsenic- selenium- tellurium-based chalcogenide lens, and the like can be composed of any one, Umicore's molded optical lens of GASIR lens may be used. Here, it will be apparent that the present invention is not particularly limited to the above examples, and that various applications of the lens exhibiting the above-described characteristics can be performed.

In addition, each of the first lens 110 and the second lens 120 may be selected from a lens made of germanium (Ge) material, a lens made of silicon (Si) material, and a lens made of gallium arsenide (GaAs). Can also be used.

In this case, the first lens 110 and the second lens 120 is formed aspherical surface to face each other with the improvement of the shape of the lens to correct the spherical aberration and distortion (distortion) and at the same time the overall magnification of the optical system It is designed to adjust the function while improving the image quality and increase the brightness, and to accurately detect infrared heat by arranging in consideration of the refractive index and transmittance of infrared light for thermal sensing.

The second lens 120 also functions to adjust infrared rays incident to the heat sensor 150.

The diaphragm 130 is disposed between the first lens 110 and the second lens 120, but closely arranged close to the first lens 110, the light incident from the first lens 110 To selectively converge.

The cover glass 140 is formed of a glass lens having a planar structure having both surfaces R5 and R6 disposed on the rear side of the second lens 120, and is arranged close to the second lens 120. To protect the heat sensor 150 disposed in front of the upper side and to prevent foreign matters from entering the sensor side.

The optical system for the ultra-small heat sensing device using the aspherical surface according to the present invention having such a configuration was configured to satisfy the overall magnification and mass productivity by appropriately distributing and arranging the lens and selecting a productive material. It was designed to show optical performance of aperture ratio F / 1.0 and field of view (40.6 degrees), and it was designed to satisfy the following conditions.

[Condition 1]

0.55 ≤ B / f ≤ 1.64

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

[Condition 2]

T / f ≤ 1.9

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

[Condition 3]

Xo1-Xa1 <0 [Aspherical Surface R2 of First Lens]

Xo2-Xa2 <0 [Aspherical Surface (R3) of Second 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.

Referring to the operation of the optical system for a micro thermal sensor according to the present invention as described above is as follows.

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.

Table 1 below shows the results of analyzing the radius of curvature, the center interval, the refractive index, the dispersion ratio, etc. of the optical system according to the embodiment of the present invention configured by the above-described configuration and conditions.

Table 1 Data of the optical system for heat sensing apparatus according to the embodiment of the present invention

                             Light amount (FNO): 1 Focal length (f): 9.46 View angle (W): 40.6 degrees Lens surface Radius of curvature (r) Thickness and spacing (d) Refractive index (Nd) Dispersion Rate (Vd) Remarks First side (R1) 9.6180 3.22 2.492 90.42 2nd side (R2) 12.768 0.636 One - Aspheric surface iris - 2.1 One - Page 3 (R3) -26.684 4.76 2.492 90.42 Aspheric surface Fourth side (R4) -10.920 4.193 One -

Here, K = 0.0, AD = 7.97331e-05, AE = 7.96154e-08 of the second surface R2, which is an aspherical structure,

K = 0.0, AD = −5.14594e-04, AE = −5.91326e-06 on the third surface R3.

The present invention is a focal length f, rear focal length B of the entire lens system by the resolution measurement, the effective diameter (dl: mm), the angle of view measurement, the spherometer (SPHEROMETER) measured by the PROFELE PROJECTOR 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 the same conditions 1, 2, and 3 are satisfied.

Namely, [condition 1] 0.55 ≦ B / f ≦ 1.64; [Condition 2] T / f ≦ 1.9; [Condition 3] Xo1-Xa1 <0 [aspherical surface R2 of the first lens] and Xo2-Xa2 <0 [aspherical surface R3 of the second lens] are satisfied.

As described above, the optical system for the ultra-small heat sensing device using the aspherical surface according to the present invention exhibits optical performance of 17.2 mm optical field length, F / 1.0 of an aspect ratio, and 40.6 degrees of viewing angle, and increases brightness by improving transmittance of thermal infrared rays. And not only have the characteristics to improve the image quality, but also enables ultra compact of the device (Ultra compact).

On the other hand, Figure 3 shows a thermal infrared trace analysis diagram of the optical system for the ultra-small thermal sensor according to the present invention, Figures 4 to 8 is an analysis graph showing the optical characteristics of the optical system for the micro-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 the degree (distortion aberration), Figure 7 shows the chromatic aberration, Figure 8 is an analysis of the optical performance of MTF (Modulation Transfer Functions), which means the resolution.

As shown in FIGS. 3 to 8, in the optical system for the heat detection apparatus using the aspherical surface according to the present invention, the values of the images are shown adjacent to the central axis in almost all fields, thereby correcting spherical aberration, meridian aberration, and chromatic aberration. Not only shows good quality, but also satisfies MTF (optical required performance / resolution).

Accordingly, the present invention provides a structure in which the lenses are arranged in the normal direction in which thermal infrared rays are incident, the concave surface of the first lens and the concave surface of the second lens are aspherical surfaces, and the special lens having the high refractive property characteristics is arranged in the center. In addition, the brightness of the surroundings can be further improved, and the image quality will be improved and the effect of miniaturization will be realized.

As described above, the optical system for the ultra-small thermal sensor using the aspherical surface according to the present invention is arranged in the aspherical surface of the first lens and the second lens, including the cover glass for protecting the thermal sensor, but the normal infrared ray direction is incident. By using the high refractive index and high refractive properties, it is possible to not only improve the optical performance, but also greatly improve the thermal infrared transmittance, expect the accuracy of thermal detection, and also have the useful effect of improving the image quality and increasing the brightness. It has optical performance of 17.2mm of optical length, F / 1.0 of aperture ratio and 40.6 degrees of clock angle.

In addition, since the optical field is reduced in comparison with the conventional optical system, it is possible to miniaturize the device, widen the application range, and provide an inexpensive optical system.

Furthermore, according to the configuration of the optical system, it is possible to establish an environment-friendly working environment that avoids exposure to heavy metals by excluding the use of heavy metal materials and the configuration of the lens that is mainly molded, rather than the lens production method by conventional polishing processing. The molding of aspherical surfaces and lenses having high refractive characteristics provides usefulness that can expect additional benefits such as mass production and cost reduction effect of the optical system required by the market.

Claims (7)

In a configuration in which the first lens, the aperture and the second lens are sequentially arranged from the object side to the image direction, in the optical system for a heat sensing device using an aspherical surface for detecting or detecting heat through the transmission of thermal infrared rays, A first lens comprising a chalcogenide lens, the convex surface having positive refractive power on the object side and the aspherical concave surface having negative refractive power on the image side, the first lens having a positive refractive power as a whole; It is composed of a chalcogenide lens, and a second lens having a positive refractive power is formed on the object side to form a concave surface having a negative refractive power and a convex surface having a positive refractive power on the image side. ; An optical system for an ultra-small heat sensing device using an aspherical surface, which satisfies the following conditional expressions (1), (2) and (3). (1) 0.55 ≤ B / f ≤ 1.6 (2) T / f ≤ 1.9 (3) Xo1-Xa1 <0 [Aspherical Surface R2 of First Lens]     Xo2-Xa2 <0 [Aspherical Surface (R3) of Second Lens] Here, f denotes the focal length of the entire lens system, B denotes the rear focal length, T denotes the optical field length from the object side lens surface of the first lens to the image lens surface of the second lens, and Xa1 denotes the first lens. Sag by the aspherical surface, Xo1 represents Sag by the reference sphere, Xa2 represents Sag by the aspherical surface of the second lens, and Xo2 represents Sag by the reference sphere. delete delete delete delete delete delete

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