KR101127905B1 - An infrared camera applying optical and mechanical athermalization mechanisms - Google Patents

Abstract

PURPOSE: An infrared ray camera is provided to enable an infrared ray camera to automatically compensate imaging performance by an optical and mechanical complex athermalization mechanism. CONSTITUTION: A front lens group assembly(120) includes a plurality of lens. A rear lens group assembly(140) includes a plurality of lens. A non-athermalization corrector(130) is installed between the front lens group assembly and the rear lens group assembly. A fisheye lens assembly(110) is installed to the rear side of the front lens group assembly.

Description

Infrared camera applying optical and mechanical athermalization mechanisms

The present invention relates to an infrared camera to which a photomechanical complex passive passive deterioration mechanism is applied, which can automatically correct (compensate) a deterioration in imaging performance of an infrared camera due to a temperature change without a user's operation. .

More specifically, the present invention, through the optical deterioration mechanism constituting the optical system with a plurality of lenses with a small change (amount) of the refractive index according to the temperature change, it is possible to shift the focal length due to the temperature change (amount) As small as possible, the proper distribution of refractive power minimizes the net shift of the focal length as a whole of the optical system, while dividing a number of these lenses into an appropriate number between the two or more lens assemblies. Through the mechanical deterioration mechanism through the deterioration compensation box, the deterioration of the imaging surface is proportional to the displacement of the imaging surface in an environment in which the position of the imaging surface may be shifted due to the temperature change and the imaging performance of the camera may be degraded. A photonic composite passive type ratio configured to effectively compensate for the degradation of the imaging performance of the infrared camera by contracting or expanding the box in the optical axis direction. Relates to an infrared camera, a screen mechanism applied.

Although the lenses constituting the optical system of the infrared camera vary depending on the material, the refractive index change according to the temperature change is much larger than that of the visible light material. That is, the imaging performance of the infrared camera is greatly affected by the temperature change.

In addition, since an article, such as a barrel, contracts or expands according to temperature, when the temperature changes, the distance between the lens and the article changes due to the difference in thermal expansion degree, resulting in an image plane of the infrared camera (or optical system). The position changes.

In addition, the air density surrounding the infrared optical system also changes with temperature, causing the infrared optical system to defocus or cause aberrations.

For this reason, in the infrared camera in which the photosensitive element is fixed at a fixed position, blurring of the image appears blurry.

As a result, infrared cameras provide high-quality images when used in an appropriate temperature range (for example, room temperature of 15 to 20 ° C), but when they are out of the appropriate temperature range, they provide a low-quality image that appears blurred and blurry. Done.

A thermalization is a way to overcome this problem, that is, the problem that the image quality of an infrared camera (broadly imaging equipment) changes with temperature. Generally, the position of the lens inserted in the barrel of the infrared camera Active and passive deterioration are classified according to whether or not there is a driving device (widely driving mechanism) to control the control.

Active deterioration is performed by adjusting the position of the lens inserted into the barrel by a driving mechanism when the position of the imaging plane of the infrared optical system is changed due to temperature change. Although there is an advantage in that the performance can be optimally maintained, additional driving mechanisms and electronic devices are required to apply such driving mechanisms, and thus, the imaging equipment becomes large and heavy, and the structure is complicated.

In addition, it takes time to adjust the position of the lens by operating this driving mechanism, which makes it difficult to correct in real time.

On the other hand, passive deterioration does not require a driving mechanism to adjust the lens position, so the structure of the imaging equipment is simple and advantageous in miniaturization and light weight. There is a limit to improving the performance of the equipment (or optical system).

Therefore, the present invention is capable of real-time correction of the deterioration of the imaging performance of the infrared camera due to temperature change, and the infrared camera to which the optical mechanical composite passive deterioration mechanism is applied structurally, which does not require a driving mechanism for adjusting the position of each lens. The purpose is to provide.

In other words, according to the present invention, the optical degradation and mechanical degradation can be simultaneously applied, and the optical performance of the imaging performance due to the positional change of the imaging surface due to the temperature change can be achieved without the user's intervention. It is an object of the present invention to provide an infrared camera capable of stably providing high quality images by automatically compensating for degradation in real time.

It is also an object of the present invention to provide a compact / lightweight infrared camera which is easy to maintain and use.

The present invention is configured to solve the above problems, by optimizing the temperature correction function of the infrared camera through the simultaneous application of the optical deterioration mechanism and mechanical deterioration mechanism, when the lens expands or contracts due to temperature change, The optical deterioration mechanism optimizes the material, shape, and placement of the lens so that the refractive power of the lens can be properly distributed, while minimizing blurring at the imaging surface of the infrared camera (or optical system) due to temperature changes. Through the mechanical deterioration mechanism that optimizes the material, shape, and coupling relationship of the mechanism in which the lens is built, the combination and structure of the coefficient of thermal expansion of the mechanism are optimized to automatically compensate for the image residual blurring that is not eliminated by optical deterioration. It is characterized by.

More specifically, the infrared camera to which the photodynamic composite passive deterioration mechanism is applied is an infrared camera having an optical module in which a plurality of lenses are arranged in the barrel and a fisheye lens assembly is mounted on the front side of the barrel. The optical module is interposed between the front lens group assembly in which some of the plurality of lenses are embedded, the rear lens group assembly in which the other of the plurality of lenses is embedded, and the front lens group assembly and the rear lens group assembly. The non-degradable complementary box , the fisheye lens assembly mounted on the front side of the front lens group assembly, and the mutually assembled front lens group assembly, the non-degraded box and the rear lens group assembly are inserted into the front lens group assembly or the rear lens group assembly. Characterized in that configured to include any one of the outer barrel is fixed.

Among the above components, the front lens group assembly is manufactured in a configuration in which a spherical lens, an aspherical lens, a cylinder lens, and an aspherical lens are arranged in this order in the front inner barrel of Invar 36. The rear lens group assembly includes: A toric lens, two spherical lenses, and an aspherical lens are manufactured in this order in the rear inner barrel of Inva 36.

The non-degradation reward box is made of a material having a larger coefficient of thermal expansion than Invar 36, and includes, for example, Teflon (brand name: T-1105-T) containing 25% (based on content) of glass fiber.

The front lens group assembly and the rear lens group assembly may each further include a retainer for preventing separation of the lens and a spacer for maintaining the distance between the lenses.

The cylinder lens and the toric lens are preferably provided in a form fitted to a cylindrical lens holder.

The outer barrel is preferably composed of Invar 36 material.

The fisheye lens assembly is composed of a spherical lens in the form of a fisheye and a pipe-type coupler made of Invar 36, in which a spherical lens is coupled to the front side and the front lens group assembly is mounted to the rear side.

According to the present invention, since the deterioration of the imaging performance inevitably caused in proportion to the temperature difference between the optimum temperature and the operating temperature is automatically corrected by the photodynamic complex passive deterioration mechanism without user intervention, the imaging performance deterioration due to the temperature change is reduced. It can reliably provide high-quality images for infrared cameras (widely infrared equipment) that must be calibrated in real time to enable immediate response.

In addition, according to the present invention, since the distance between the lenses is adjusted by the thermal expansion / thermal contraction according to the temperature, there is no need to provide a separate driving device for artificially adjusting the distance between the lenses, such as active deterioration, The camera can be made smaller and lighter.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view showing an example of an optical deterioration mechanism of an infrared camera to which a photomechanical complex passive deterioration mechanism according to the present invention is applied.
Figure 2 is an overall configuration diagram shown to explain an example of the mechanical deterioration mechanism of the infrared camera to which the optical mechanical composite passive deterioration mechanism of the present invention is applied.
FIG. 3 is an exploded view showing the coupling structure of each part of the optical mechanical passive passive deterioration mechanism shown in FIG.
4 is a graph comparing optical performance (image improvement) before and after deterioration correction at a temperature of 50 ° C. of an infrared camera to which a photomechanical complex passive deterioration mechanism according to the present invention is applied.
5 is a graph comparing optical performance before and after deterioration correction at a temperature of 40 ° C. of an infrared camera to which an optical mechanical complex passive deterioration mechanism according to the present invention is applied.
Figure 6 is a graph comparing the optical performance before and after deterioration correction at a temperature of 30 ℃ of the infrared camera to which the optical mechanical composite passive deterioration mechanism according to the present invention.
7 is a graph comparing optical performance before and after deterioration correction at a temperature of 20 ° C. of an infrared camera to which a photomechanical complex passive deterioration mechanism according to the present invention is applied.
8 is a graph comparing optical performance before and after deterioration correction at a temperature of 10 ° C. of an infrared camera to which a photomechanical complex passive deterioration mechanism according to the present invention is applied.
9 is a graph comparing optical performance before and after deterioration correction at a temperature of 0 ° C. of an infrared camera to which a photomechanical complex passive deterioration mechanism according to the present invention is applied.
10 is a graph comparing optical performance before and after deterioration correction at a temperature of −10 ° C. of an infrared camera to which a photomechanical complex passive deterioration mechanism according to the present invention is applied.

Hereinafter, the configuration and operation effects of the infrared camera to which the photomechanical complex passive deterioration mechanism according to the present invention is applied will be described in detail with reference to the accompanying drawings.

As mentioned above, the present invention aims to stably provide an image having excellent optical performance by applying a complex passive deterioration mechanism to an infrared camera, without degrading the imaging performance according to the operating temperature. The objective is to make it possible to achieve light weight effectively.

This object is achieved by, for example, the optical deterioration mechanism shown in FIG. 1 and the mechanical deterioration mechanism shown in FIGS. 2 and 3. Among these, the characteristics of the optical deterioration mechanism will be described first. .

Characteristic of optical deterioration mechanism

In general, the movement of an imaging plane (or focal plane) due to temperature change in an optical system composed of a plurality of lenses is expressed by Equation 1 below.

Where df represents a focal length shift according to temperature change, f represents a focal length, n represents a refractive index, ( dn / dt ) represents a change in refractive index according to a change in temperature, and Δ t represents a change in temperature.

In Equation 1, it can be seen that when the refractive index n changes, the focal length shift amount df changes. In addition, the direction of the focal length shift amount df is determined according to the focal length f of the lens , that is, whether the lens has a positive or negative refractive power.

Therefore, when the optical system is configured using a lens made of a material having a small refractive index change ( dn / dt ) due to temperature change, the cumulative value (Σ df ) of the focal length shift amount accumulated in the entire optical system can be minimized.

The optical deterioration mechanism in the present invention has a blur on the image surface according to temperature through optimized material selection and refractive power distribution of the lenses constituting the optical system so that the cumulative value of the focal length shift amount is minimized. To configure the infrared optics in such a way that the ring can be minimized.

1, the optical system formed to implement the optical deterioration mechanism of the present invention is composed of, for example, nine lenses, the amount of refractive index change when the material, focal length, temperature of these lenses changes by 1 ° C. This is shown in Table 1.

In FIG. 1 and Table 1, among the nine lenses, six lenses were made of zinc sulfide (ZnS) or zinc selenide (ZnSe) having a small refractive index change according to temperature change, and the remaining three lenses. In order to distribute the refractive power and to secure the focal length of the optical system, silicon was used as the material.

More specifically, a fisheye spherical lens 1 providing a wide field of view is disposed at the forefront of the optical system, followed by a spherical lens 2, an aspherical lens 3, and a cylinder. The lens 4, the aspherical lens 5, the toric lens 6, the spherical lenses 7 and 8 and the aspherical lens 9 are sequentially arranged.

At the end of the optical system, an aperture stop 10 is arranged, followed by an image sensor (not shown) of the infrared camera.

The arrangement of the lens as described above is disclosed in detail, for example, in Patent Application No. 10-2011-0114650, which is the applicant's prior application, and the contents disclosed in the application are incorporated herein by reference.

Characteristics of mechanical deterioration mechanism

Based on FIG.2 and FIG.3, the mechanical deterioration mechanism which is one theme in this invention is demonstrated.

The optical module 100 shown in these drawings is an optical module to which both an optical deterioration mechanism and a mechanical deterioration mechanism according to the present invention are applied, and a plurality of lenses 1 to 9 and a non-degradation compensation box made of Teflon material ( Except for 130, all components are made of Invar 36.

The optical module 100 is composed of a fisheye lens assembly 100, a front lens group assembly 120, a non-degradation box 130, a rear lens group assembly 140 and an outer barrel 150, these components Are used to be mounted on the front surface of the main body of an infrared camera (not shown) in an assembled state.

The fisheye lens assembly 110 includes a fisheye-shaped spherical lens 1 that provides a wide field of view, and a spherical lens 1 coupled to the front side and the front lens group assembly 120. Is composed of a pipe-type coupler 111 made of Invar 36 is mounted on the rear side.

A screw thread is formed on the rear inner surface of the coupler 111 so that the front side of the front lens group assembly 120 to be described later may be fastened by a screwing method.

The front lens group assembly 120 includes a front side inner barrel 121 made of Invar 36, four lenses 2-5 disposed in the front inner barrel 121, and these lenses 2-5 are separated. It is composed of a ring-shaped retainer 122 fitted to the inner front end of the front inner barrel 121 and a spacer 123 sandwiched between the lenses 2 and 3 to maintain the distance between the lenses. .

The four lenses 2 to 5 are arranged in order from the front in order of the spherical lens 2, the aspherical lens 3, the cylinder lens 4, and the aspherical lens 5 in this order. In addition, the cylinder lens 4 is provided in a form fitted to the cylindrical lens holder 124.

The rear lens group assembly 140 includes a rear inner barrel 141 made of Invar 36, four lenses 6 to 9 disposed in the rear inner barrel 141, and a front side of the rear inner barrel 141. And a retainer 142 sandwiched between them and a spacer 144 sandwiched between the lenses.

The four lenses 6 to 9 have the toric lens 6, the two spherical lenses 7 and 8, and the aspherical lens 9 from the front, with the longitudinal direction of the rear inner barrel 141 in the front-rear direction. It is arranged. The toric lens 6 and the spherical lens 8 are provided in a form fitted to the cylindrical lens holder 143,145.

Subsequently, the front lens group assembly 120 and the rear lens group assembly 140 are each screwed to the front and rear ends of the non-degradation box 130 with a Teflon non-deterioration box 130 therebetween. do. If the assembly was correct, the optical axes of the front lens group assembly 120 and the rear lens group assembly 140 coincide.

In this embodiment, the deterioration reward box 130 has a structure in which slits are formed on the surface of the pipe in order to reduce the weight of the optical module 100.

In this way, the integrated front lens group assembly 120, the non-degradation compensation box 130, and the rear lens group assembly 140 are fitted to the outer barrel 150 made of Invar 36, so that only the front lens group assembly 120 is external. Screw is fixed to have a structure that is coupled to the barrel (150).

Therefore, when the non-degradation box 130 having no fastening structure with the outer barrel 150 contracts / expands according to the operating temperature, the rear lens group assembly 140 mounted at the rear end of the non-deterioration box 130 is The infrared camera is moved closer to or farther from the front of the main body of the infrared camera, and as a result, the distance from the image sensor built into the main body of the infrared camera is automatically adjusted to improve the imaging performance of the camera.

Table 2 below shows the Teflon (brand name: T-1105-T) containing 25% (content) of glass fiber in comparison with the thermal expansion coefficient of Invar 36.

Image forming performance comparison experiment

4 to 10 are graphs comparing optical performance before and after deterioration compensation of an infrared camera to which a photomechanical complex passive deterioration mechanism according to the present invention is applied. For comparison of the deterioration performance, a Modulation Transfer Function (MTF) value capable of comprehensively determining the system performance of the infrared camera was used.

This comparative experiment was conducted in an environment capable of varying the temperature by 10 ° C in the range of -10 ° C to 50 ° C. In each figure, (a) shows the modulation transfer function performance before correction, and (b ) Represents the modulation transfer function performance after compensation.

In addition, in the angular graph, the dotted line displayed at the top represents a diffraction limit. The closer to this diffraction limit, the better the optical performance of the infrared camera.

From this point of view, comparing the graphs before and after deterioration correction, it is easy to see that the optical performance of the infrared camera has been greatly improved.

1 ... spherical lens 2 ... spherical lens
3 ... aspherical lens 4 ... cylinder lens
5 ... aspheric lens 6 ... toric lens
7 ... Spherical Lens 8 ... Spherical Lens
9.Aspherical lens 10.Aperture stop
Optical module 110 Fisheye lens assembly
111 ... coupler 120 ... front lens group assembly
121.Front inner barrel 122 ... Retainer
123 ... spacer 124 ... lens holder
130 Deterioration box 140 Rear lens group assembly
141 ... Rear inner barrel 142 ... Retainer
143 ... lens holder 144 ... spacer
145 Lens holder 150 Outer tube

Claims (5)

An infrared camera having an optical module in which a plurality of lenses are arranged in a barrel and a fisheye lens assembly is mounted on the front side of the barrel.
The optical module,
A front lens group assembly in which some of the plurality of lenses are embedded;
A rear lens group assembly in which the rest of the plurality of lenses are embedded;
A non-degradation compensation box interposed between the front lens group assembly and the rear lens group assembly to be integrally fixed;
A fisheye lens assembly mounted at a front side of the front lens group assembly;
An external barrel into which the front lens group assembly, the non-deteriorated box, and the rear lens group assembly are inserted, and fixed to either the front lens group assembly or the rear lens group assembly;
Infrared camera applied to the optical mechanical composite passive deterioration mechanism, characterized in that configured to include. The method of claim 1,
The front lens group assembly,
A spherical lens, an aspherical lens, a cylinder lens, an aspherical lens are arranged in front of the inner barrel of Invar 36 in order from the front,
The rear lens group assembly,
An infrared camera having a photodynamic composite passive deterioration mechanism, comprising: a toric lens, two spherical lenses, and an aspherical lens arranged in order from the front in the rear inner barrel of Inva 36. The method of claim 2,
Non-degradation reward box,
Infrared camera with a photomechanical composite passive deterioration mechanism, characterized in that the thermal expansion coefficient compared to Invar 36. The method of claim 2,
The front lens group assembly and the rear lens group assembly, respectively,
It further includes a retainer for preventing the detachment of the lens, and a spacer for maintaining the distance between the lenses,
The cylindrical lens and the toric lens are provided in a form fitted in a cylindrical lens holder. 5. The method according to any one of claims 1 to 4,
The outer barrel is made of Invar 36 material,
The fisheye lens assembly is composed of a spherical lens in the form of a fisheye and a pipe-type coupler made of Invar 36, in which a spherical lens is coupled to the front side and the front lens group assembly is mounted to the rear side. Infrared camera with mechanism.

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