TWI848424B - Thermal imaging lens - Google Patents

Abstract

A thermal imaging lens including a lens holder, a thermal sensing element, a lens barrel and at least one lens element is provided. The thermal sensing element is disposed on the lens holder. The lens barrel is movably disposed on the lens holder. The at least one lens element is disposed in the lens barrel. Wherein, the material of the lens holder and the lens barrel includes metal or polymer. The material of the at least one lens element includes polymer or heat-transmitting glass. The thermal sensing element is formed by an integrated process, and the lens barrel changes the full field of view of the thermal imaging lens by adjusting the distance between the at least one lens and the sensing element.

Description

Thermal imaging lens

The present invention relates to a sensing device, and in particular to a thermal imaging lens.

Common temperature sensors include thermocouples (TC), thermistors, resistance temperature detectors (RTDs) or infrared thermopile sensors (TP). Among them, a thermocouple is composed of a pair of junctions made of two different metals. A resistance temperature detector is a temperature sensor with resistance, which changes its resistance value when the temperature changes. Infrared thermopile sensors use chip-level packaging. This non-contact sensor uses a thermopile to absorb infrared energy emitted from the object being measured, and then uses the corresponding change in the thermopile voltage to determine the temperature of the object.

With the advancement of production technology, new semiconductor thermal chips such as Temperature Complementary Metal-Oxide-Semiconductor (TMOS) have also been introduced. These thermal sensors often require additional lens sets to cope with various viewing angles or object distances, and the alignment of the optical axis and the sensor chip is important. Especially when multiple sensing chips are required for the application, effective optical axis alignment requires additional adjustment. However, most existing thermal imaging lens modules are fixed-focus lenses, and traditional thermal sensing module infrared sensing lenses are mostly telephoto and multi-zone field of view composite lenses. The optical system of this multi-zone field of view is large and has many blind spots.

The present invention provides a thermal imaging lens with a relatively small size and switchable full field of view angle.

The present invention provides a thermal imaging lens, including a lens base, a thermal sensing element, a lens barrel and at least one lens. The thermal sensing element is disposed on the lens base. The lens barrel is movably disposed on the lens base. At least one lens is disposed on the lens barrel. The lens base and the lens barrel are made of metal or polymer material. The material of at least one lens is made of polymer material or heat-transmitting glass. The thermal sensing element is formed by an integrated process, and the lens barrel changes the full field of view of the thermal imaging lens by adjusting the distance between at least one lens and the sensing element.

In one embodiment of the present invention, the transmittance of the at least one lens is greater than 20% for light with a wavelength greater than or equal to 7 microns and less than or equal to 14 microns.

In one embodiment of the present invention, the absorption rate of the above-mentioned part of the lens base and/or part of the lens barrel to infrared rays is greater than 80%.

In one embodiment of the present invention, the minimum thickness of the optically effective area of the at least one lens is less than or equal to 0.8 mm.

In one embodiment of the present invention, the thermal sensing element is a temperature sensing semiconductor metal oxide sensor.

In one embodiment of the present invention, the thermal imaging lens satisfies the following equation: 4≦R≦1, where R is the ratio of the maximum full field of view angle to the minimum full field of view angle of the thermal imaging lens.

In one embodiment of the present invention, the full field of view of the thermal imaging lens satisfies the following equation: FOV=aS ² +bS+c, -2 mm≦S≦2 mm, where FOV is the full field of view of the thermal imaging lens, S is the displacement of the thermal imaging lens, and a, b and c are constants.

In one embodiment of the present invention, the above-mentioned thermal imaging lens meets the following conditions: 6.306 < a < 10.8 and -30.95 < b < -25.88.

In one embodiment of the present invention, the full field of view of the thermal imaging lens satisfies the following equation: FOV = dL ² +eL+f, 0.5 mm≦L≦4 mm, where FOV is the full field of view of the thermal imaging lens, L is the BFL of the thermal imaging lens, and d, e, and f are constants.

In one embodiment of the present invention, the above-mentioned thermal imaging lens meets the following conditions: 6.306 < d < 10.8 and -68.94 < e < -49.28.

In one embodiment of the present invention, the above-mentioned thermal sensing element includes a planar protective film and a sensing chip. The planar protective film is disposed on the sensing chip and has a vacuum gap between the planar protective film and the sensing chip.

In one embodiment of the present invention, the thermal imaging lens satisfies the following condition: EFL>TTL, wherein EFL is the equal correction focal length of the thermal imaging lens, and TTL is the length from at least one lens to the thermal sensing element.

In one embodiment of the present invention, the thermal imaging lens satisfies the following condition: EFL>BFL, wherein EFL is the equal correction focal length of the thermal imaging lens, and BFL is the back focal length of at least one lens.

Based on the above, in the thermal imaging lens of the present invention, the thermal imaging lens includes a lens holder, a thermal sensing element disposed on the lens holder, a lens barrel movably disposed on the lens holder, and at least one lens disposed on the lens barrel. The thermal sensing element is formed by an integrated process, and the lens barrel changes the full field of view of the thermal imaging lens by adjusting the distance between the at least one lens and the thermal sensing element. In this way, a smaller volume can be achieved, and different full field of view angles can be obtained by switching.

In order to make the above features and advantages of the present invention more clearly understood, embodiments are specifically cited below and described in detail with reference to the accompanying drawings.

FIG. 1A to FIG. 1C are cross-sectional schematic diagrams of a thermal imaging lens switching different full-view angles according to an embodiment of the present invention. Please refer to FIG. 1A to FIG. 1C. This embodiment provides a thermal imaging lens 100, including a lens holder 110, a thermal sensing element 120, a lens barrel 130, and at least one lens 140. The thermal imaging lens 100 is used to sense infrared rays, or to capture infrared rays to obtain thermal imaging. In addition, the thermal imaging lens 100 of this embodiment is a zoom lens module, which can change different full-view angles F by switching, and then be applied in different environments.

FIG2 is a full field of view distribution curve of the thermal imaging lens of FIG1A. Please refer to FIG2. It should be noted that the full field of view of the present invention refers to the angle range covered by the relative signal intensity greater than or equal to 0.5, as shown in FIG2.

Please continue to refer to FIG. 1A to FIG. 1C. The thermal sensing element 120 is disposed on the lens holder 110, and the thermal sensing element 120 is formed by an integrated process. In this embodiment, the thermal sensing element 120 is a temperature-sensitive semiconductor metal oxide sensor (Temperature Complementary Metal Oxide Semiconductor, TMOS). In addition, in this embodiment, the thermal sensing element 120 includes a flat protective sheet and a sensing chip (not shown), wherein the flat protective sheet is disposed on the sensing chip, and there is a vacuum gap between the flat protective sheet and the sensing chip. Therefore, the thermal sensing quality can be further improved.

Furthermore, in some embodiments, the thermal sensing element 120 may include a sensing unit, a calibration unit, and a thermal insulation structure, wherein the sensing unit is the temperature-sensing semiconductor metal oxide mentioned above, and the type and quantity of the calibration unit are the same as the sensing unit. The only difference is that the thermal insulation structure covers the calibration unit to isolate the external heat source (or infrared rays). The thermal insulation structure is, for example, metal, but the present invention does not limit its type. Therefore, when sensing is performed, the sensing unit can be calibrated by comparing the background information sensed by the calibration unit, and the infrared light signal intensity of a specific band can be obtained, thereby improving the sensing quality of the thermal sensing element 120. However, the present invention is not limited to this.

At least one lens 140 is disposed on the barrel 130, wherein the material of the at least one lens 140 includes a polymer material or a heat-transmitting glass. For example, in this embodiment, the number of the lens 140 is one, but the present invention is not limited thereto, and the transmittance of the lens 140 to light having a wavelength of greater than or equal to 7 microns and less than or equal to 14 microns is greater than 20%. In addition, in this embodiment, the minimum thickness of the optical effective area of the lens 140 is less than or equal to 0.8 mm, but the present invention is not limited thereto.

The lens barrel 130 is movably disposed on the lens base 110, and the lens barrel 130 changes the full field angle F of the thermal imaging lens 100 by adjusting the distance between the lens 140 and the thermal sensing element 120. The material of the lens base 110 and the lens barrel 130 includes metal or polymer material. In this embodiment, the material of the lens base 110 and/or a part of the lens barrel 130 is an infrared absorbing material, for example, a material with an infrared absorption rate greater than 80% is selected, but the present invention is not limited thereto. In detail, in this embodiment, the lens base 110 is a surrounding wall structure, surrounding an internal space, for accommodating the thermal sensing element 120. The lens barrel 130 is embedded in the inner side of the surrounding wall structure, and can be moved along the optical axis on the lens base 110 to change its position through structural design. For example, in this embodiment, the inner side of the surrounding wall of the lens base 110 and the outer side of the lens barrel 130 have mutually matching thread structures A, so the user can assemble and adjust the position by rotating the lens barrel 130.

FIG3 is a graph showing the performance of the thermal imaging lens of FIG1A when switching the full field of view. Please refer to FIG3. For another example, in this embodiment, when the lens barrel 130 is rotated to adjust the distance D from the lens 140 to the thermal sensing element 120 to 1.82 mm, the full field of view F of the thermal imaging lens 100 is 25 degrees, as shown in FIG1A. If the lens barrel 130 is rotated to adjust the distance D from the lens 140 to the thermal sensing element 120 to 1.57 mm, the full field of view F of the thermal imaging lens 100 can be increased to 45 degrees, as shown in FIG1B. If the lens barrel 130 is rotated to adjust the distance D between the lens 140 and the thermal sensing element 120 to 1.32 mm, the full field of view F of the thermal imaging lens 100 can be increased to 60 degrees, as shown in FIG1C . In this way, the lens barrel 130 can obtain different full field of view angles F by adjusting the distance D between the lens 140 and the thermal sensing element 120 , as shown in FIG3 .

FIG4 is a schematic diagram of the working principle of the thermal imaging lens of FIG1A. Please refer to FIG2. The above paragraphs further illustrate that the present embodiment utilizes the different positions between the lens 140 and the focal point (for example, the equivalent focal length F1> the back focal length F2), so that the focal point of each viewing angle is large enough and effectively covers the sensing area of the thermal sensing element 120. Therefore, when the displacement is a positive value and the effective light-collecting area is still within the sensing area size of the original thermal sensing element 120, the equivalent full field of view F will become smaller. When the displacement is a negative value and the effective light-collecting area is still within the sensing area size of the original thermal sensing element 120, the equivalent full field of view F will become larger. In this way, adjusting the center point C of the mark can achieve different full field of view F results.

In the present embodiment, the thermal imaging lens 100 satisfies the following equation: 4≦R≦1, where R is the ratio of the maximum full field angle F to the minimum full field angle F of the thermal imaging lens 100. In the present embodiment, the thermal imaging lens 100 satisfies the following equation: EFL>TTL, where EFL is the equal correction focal length F1 of the thermal imaging lens 100, and TTL is the distance D from at least one lens 140 to the thermal sensing element 120. In addition, in the present embodiment, the thermal imaging lens 100 also satisfies the following equation: EFL>BFL, where BFL is the back focal length F2 of at least one lens 140. Furthermore, in the present embodiment, the full field of view F of the thermal imaging lens 100 may satisfy the following formula: FOV=aS ² +bS+c, -2 mm≦S≦2 mm, where FOV is the full field of view F of the thermal imaging lens 100, S is the displacement of the thermal imaging lens 100, and a, b, and c are constants. In a preferred embodiment, 6.306 < a < 10.8 and -30.95 < b < -25.88. In addition, in the present embodiment, the full field of view F of the thermal imaging lens 100 may also satisfy the following formula: FOV=dL ² +eL+f, 0.5 mm≦L≦4 mm, where L is the back focal length F2 of the thermal imaging lens 100, and d, e, and f are constants. In a preferred embodiment, the thermal imaging lens 100 meets the following conditions: 6.306 < d < 10.8 and -68.94 < e < -49.28. By means of the above-mentioned various conditions, the thermal imaging lens 100 can have better optical quality and thermal sensing/imaging quality. However, the present invention is not limited thereto.

In summary, in the thermal imaging lens of the present invention, the thermal imaging lens includes a lens holder, a thermal sensing element disposed on the lens holder, a lens barrel movably disposed on the lens holder, and at least one lens disposed on the lens barrel. The thermal sensing element is formed by an integrated process, and the lens barrel changes the full field of view of the thermal imaging lens by adjusting the distance between the at least one lens and the thermal sensing element. In this way, a smaller volume can be achieved, and different full field of view angles can be obtained by switching.

Although the present invention has been disclosed as above by the embodiments, they are not intended to limit the present invention. Any person with ordinary knowledge in the relevant technical field can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be defined by the scope of the attached patent application.

100: Electronic device 110: Lens mount 120: Thermal sensor 130: Lens barrel 140: Lens A: Thread structure C: Center point D: Distance F: Full field of view F1: Equi-calibration focal length F2: Back focal length

Figures 1A to 1C are cross-sectional schematic diagrams of a thermal imaging lens switching different full-view angles according to an embodiment of the present invention. Figure 2 is a full-view angle distribution curve diagram of the thermal imaging lens of Figure 1A. Figure 3 is a performance curve diagram of the thermal imaging lens of Figure 1A switching full-view angle. Figure 4 is a schematic diagram of the working principle of the thermal imaging lens of Figure 1A.

100: Electronic device 110: Lens mount 120: Thermal sensing element 130: Lens barrel 140: Lens A: Thread structure D: Distance F: Full field of view

Claims (11)

A thermal imaging lens comprises: a lens base; a thermal sensing element disposed on the lens base; a lens barrel movably disposed on the lens base; and at least one lens disposed on the lens barrel, wherein the lens base and the lens barrel are made of metal or polymer material, the at least one lens is made of polymer material or heat-transmitting glass, the thermal sensing element is formed by an integrated process, and the lens barrel changes the full field of view of the thermal imaging lens by adjusting the distance between the at least one lens and the thermal sensing element, the at least one lens has a light transmittance greater than 20% for wavelengths greater than or equal to 7 microns and less than or equal to 14 microns, and the minimum thickness of the optical effective area of the at least one lens is less than or equal to 0.8 mm. The thermal imaging lens as described in claim 1, wherein the absorption of infrared rays by part of the lens base and/or part of the lens barrel is greater than 80%. A thermal imaging lens as described in claim 1, wherein the thermal sensing element is a temperature-sensing semiconductor metal oxide sensor. A thermal imaging lens as described in claim 1, wherein the thermal imaging lens satisfies the following equation: 4≦R≦1, wherein R is the ratio of the maximum full field of view angle to the minimum full field of view angle of the thermal imaging lens. A thermal imaging lens as described in claim 1, wherein the full field of view of the thermal imaging lens satisfies the following equation: FOV=aS ² +bS+c, -2mm≦S≦2 mm, wherein FOV is the full field of view of the thermal imaging lens, S is the displacement of the thermal imaging lens, and a, b and c are constants. A thermal imaging lens as described in claim 5, wherein the thermal imaging lens meets the following conditions: 6.306<a<10.8 and -30.95<b<-25.88. A thermal imaging lens as described in claim 1, wherein the full field of view of the thermal imaging lens satisfies the following equation: FOV=dL ² +eL+f, 0.5mm≦L≦4mm, wherein FOV is the full field of view of the thermal imaging lens, L is the BFL of the thermal imaging lens, and d, e, and f are constants. A thermal imaging lens as described in claim 7, wherein the thermal imaging lens meets the following conditions: 6.306<d<10.8 and -68.94<e<-49.28. The thermal imaging lens as described in claim 1, wherein the thermal sensing element includes a planar protective film and a sensing chip, the planar protective film is disposed on the sensing chip and has a vacuum gap between the planar protective film and the sensing chip. A thermal imaging lens as described in claim 1, wherein the thermal imaging lens satisfies the following conditions: EFL>TTL, wherein EFL is the equal correction focal length of the thermal imaging lens, and TTL is the distance from the at least one lens to the thermal sensing element. A thermal imaging lens as described in claim 1, wherein the thermal imaging lens satisfies the following formula: EFL>BFL, wherein EFL is the equal correction focal length of the thermal imaging lens, and BFL is the back focal length of the at least one lens.

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