System and method for optical alignment and calibration of an infrared camera lens

Abstract

1. A system for optical alignment and calibration of an infrared camera lens, comprising: a lens support mechanism configured to adjust a position of the infrared camera lens relative to a camera body; at least one collimator configured to output infrared light, the at least one collimator positioned such that the output infrared light is focused through the infrared camera lens onto an infrared sensor within the camera body; and at least one curing catalyst configured to cure an adhesive disposed on the infrared camera lens once an ideal lens position is determined.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Patent Application No. 16 / 699,894, filed December 2, 2019, the contents of each of which are incorporated herein by reference.

[0002] The present disclosure relates generally to camera lens calibration, and more particularly to the initial alignment and calibration of an infrared camera lens. [Background technology]

[0003] In recent years, dramatic improvements in sensor-based technology have enabled new applications for sensors. Cameras, in particular, have become widely used in a variety of applications, including advanced driver assistance systems (ADAS) and autonomous vehicle systems. One type of camera that can be used in these applications is the thermal infrared camera. The infrared spectrum lies outside the visible light range and consists of the near-infrared section (NIR) with wavelengths between 0.75 and 1 micrometer (μm), the short-wave infrared section (SWIR) with wavelengths between 1 and 3 μm, the mid-wave infrared section (MWIR) with wavelengths between 3 and 5 μm, and the long-wave infrared section (LWIR) with wavelengths between 8 and 14 μm. Many thermal infrared (IR) cameras operate within the LWIR section, detecting infrared energy directed through the camera's lens to an IR sensor. These IR cameras can be used in a variety of imaging applications, including, but not limited to, passive motion detection, night vision, thermal mapping, healthcare, building inspection, surveillance, and ADAS. DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0004] During the manufacture of an infrared camera, the lens must be attached to the camera body—the element of the camera that houses the infrared image sensor. This attachment must be performed to strict standards, since the lens must not only be positioned at an ideal distance from the sensor, but also in an ideal plane. Any slight shift or distortion in positioning will result in a subpar or out-of-focus image. Therefore, the lens must be fixed to the camera body with optimal positioning along six degrees of freedom. Manually attaching lenses in such a precise manner is not only ineffective, but difficult to replicate on a consistent basis, let alone achieve in an efficient manner. Furthermore, even if a robotic arm is used to perform the attachment and ensure the same motion is repeated from camera to camera, each lens and sensor may vary slightly, requiring a unique, individualized attachment for each sensor and lens pair—a challenging task for a typical robot.

[0005] Therefore, it would be advantageous to provide a solution that overcomes the above-mentioned challenges. [Means for solving the problem]

[0006] A summary of some example embodiments of the present disclosure follows. This summary is provided for the reader's convenience to provide a basic understanding of such embodiments, but does not completely define the breadth of the disclosure. This summary is not an extensive overview of all contemplated embodiments, and is not intended to identify key or critical elements of all embodiments or delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more embodiments in a simplified form as a prelude to the more detailed description that is presented later. For convenience, the term "specific embodiment" may be used herein to refer to a single embodiment or to multiple embodiments of the present disclosure.

[0007] Certain embodiments disclosed herein include a system for optical alignment and calibration of an infrared camera lens, including a lens support mechanism configured to adjust the position of the infrared camera lens relative to a camera body; at least one collimator configured to output infrared light, the at least one collimator positioned such that the output infrared light is focused through the infrared camera lens onto an infrared sensor within the camera body; and at least one curing catalyst configured to cure an adhesive disposed on the infrared camera lens once an ideal lens position is determined.

[0008] Certain embodiments disclosed herein also include a method for optical alignment and calibration of an infrared camera lens, comprising applying an adhesive to an infrared camera lens, the adhesive configured to be cured by a curing catalyst; positioning the lens on a camera body using an adjustable arm; determining an ideal lens position based on at least a calibration target and an associated modulation transfer function (MTF) chart; adjusting the position of the infrared camera lens based on the determined ideal lens position; and curing the adhesive with the curing catalyst and fixing the infrared camera lens in place. [Brief explanation of the drawings]

[0009] The subject matter disclosed herein is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. These and other objects, features, and advantages of the disclosed embodiments will become apparent from the following detailed description taken in conjunction with the accompanying drawings.

[0010] [Figure 1] FIG. 1 is a schematic diagram of a system for optical alignment and calibration of an infrared camera lens according to one embodiment.

[0011] [Figure 2A]FIG. 2 is a schematic diagram of a calibration target according to one embodiment.

[0012] [Figure 2B] 1 is an exemplary screenshot of multiple calibration targets as viewed through a calibration system.

[0013] [Figure 3] 10 is an exemplary screenshot of multiple modulation transfer function (MTF) charts projected onto an image of a calibration target after calibration is complete.

[0014] [Figure 4] 1 is an example flowchart illustrating a method for mounting and aligning an infrared camera lens according to one embodiment.

[0015] [Figure 5] 1 is an example setup of an infrared lens alignment system and curing light according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] It is important to note that the embodiments disclosed herein are merely examples of the many advantageous uses of the innovative teachings herein. In general, statements made in the specification of this application do not necessarily limit any of the various claimed embodiments. Moreover, some statements may apply to some inventive features but not to other features. In general, unless otherwise specified, singular elements may refer to plural and vice versa without loss of generality. In the drawings, like numerals refer to like parts throughout the several views.

[0017] FIG. 1 is a schematic diagram of a system 100 for optical alignment and calibration of an infrared camera lens 120, according to one embodiment. The system 100 includes one or more collimators 150 positioned directly above a lens 120, such as an infrared lens, to be used for lens calibration. The lens support mechanism of the system 100 includes a robotic arm 140 configured to hold the lens 120 and manipulate its position relative to the camera body 110. In one embodiment, the robotic arm 140 is supported by a hexapod platform 145. In an exemplary embodiment, the platform 145 is configured to move the robotic arm 140 and its attached lens 120 through a predetermined number of degrees of freedom (e.g., six). In a further embodiment, the hexapod platform 145 is a Steward / Stewart platform with a high-resolution kinematic system using three pairs of hydraulic, pneumatic, or electromechanical actuators configured to adjust the x, y, and z axes along with pitch, roll, and yaw. This allows precise adjustments to the positioning of the robotic arm 140 attached to it, and therefore the lens 120. In one embodiment, the hexapod is controlled by software configured to adjust the hexapod according to readings from the collimator 150, or hardware configured to execute such software, as described further below.

[0018] Software shall be construed broadly to mean any type of instructions stored on a machine-readable medium, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Instructions may include code (e.g., code in source code format, binary code format, executable code format, or any other suitable format).

[0019] Collimator 150 is an optical device that includes a well-calibrated objective lens with an illuminated calibration target at its focal plane. The exiting beam (or output beam) is parallel or collimated so that an image of the calibration target is projected at infinity. In one embodiment, there are five collimators 150 positioned above lens 120 and camera body 110 and configured to output a projection of the calibration target. Collimators 150 are positioned so that the output calibration target projection is focused through lens 120 onto an infrared sensor within camera body 110. The angular placement of the collimators is designed to define the full area of ​​the image sensor according to the camera's apparent field of view (FOV). In one embodiment, a shutter mechanism (not shown) is positioned between lens 120 and collimator 150, allowing the shutter to open and close as the position of lens 120 is adjusted, providing an efficient method of calibrating the lens between various positions.

[0020] Each collimator 150 includes three main parts: a blackbody, a target, and a collimating lens system. Components (or portions) of the collimator 150 are located within the collimator structure and are not shown in FIG. 1 . In one embodiment, the blackbody is an electronically controlled device used as a highly stable background radiation source for the target. In one embodiment, it provides a 10-degree difference relative to room temperature. The camera sensor is positioned facing the blackbody so that when the lens 120 is in place, the image generated by the sensor includes the calibration target along with the blackbody background. When in the properly calibrated position, the projection of the calibration target is focused onto the infrared sensor of the camera 110 so that, when the lens 120 is in place, the MTF value is optimized for all calibration targets. The system 100 may include multiple blackbodies positioned within the sensor's FOV to be used as calibration targets for the lenses. Calibration targets are described further below.

[0021] In one embodiment, one or more ultraviolet (UV) light sources 170 are positioned around the lens 120 and camera body 110. An adhesive can be used to secure the lens 120 to the camera body 110, where the adhesive only hardens when exposed to UV light. Thus, the position of the lens 120 can be freely adjusted, as described below, until the ideal position is determined, at which point the UV light source 170 is used to harden the adhesive and secure the lens in place. In further embodiments, an alternative curing mechanism, such as visible light curing, temperature-based curing, or chemical curing, is used instead of a UV-based curing mechanism.

[0022] 2A is a schematic diagram of a calibration target 200 according to one embodiment. The target may include a black body designed to provide a temperature difference as a measure of thermal radiation and may reveal portions of the black body arranged in a certain (or specific) pattern that can be recorded by a detector and analyzed by image processing software. In one embodiment, an exemplary pattern includes a calibration target 200 having a circular shape and portions of the circular shape exposed to expose the black body. For example, a wedge 210 is shown having a particular angle, e.g., a 104 degree angle (90 degrees of a quarter circle, with an additional 7 degrees 220 extending outward from each axis of the wedge). In one embodiment, the size of the wedge 210, e.g., the wedge angle, is adjustable, which allows control over the appearance of the pattern and supports a variety of different patterns to support the needs of various applications. The straight edges, set angle, and curved perimeter of the wedge shape provide different useful reference points to aid in determining sharp focus and calibration of the lens. Placing five calibration targets 200 in a defined portion of the lens's FOV allows for greater optimization of the lens's position.

[0023] 2B is an exemplary screenshot of multiple calibration targets 200 as viewed through a calibration system. The calibration targets 200 are positioned to maximize coverage of the image sensor's FOV. In one embodiment, five calibration targets 200 are used, with one target positioned at each corner and one target positioned in the center of the frame. The calibration targets 200 are viewed through a collimator, such as collimator 150 of FIG. 1. That is, each of the five collimators can include one calibration target 200, positioned to fill the image sensor's FOV.

[0024] FIG. 3 is an example screenshot of a multiple modulation transfer function (MTF) chart 300 projected onto an image of a calibration target. MTF is a tool used to measure the imaging quality, including contrast and resolution, of an optical device. An MTF graph displays contrast as a function of spatial frequency. In one embodiment, the center (or middle) of the image sensor exhibits a higher MTF compared to the ends of the sensor. In the disclosed embodiment, each section (or portion) of the frame containing the calibration target 200 is provided with an MTF chart 300. The positioning of the lens is adjusted until each MTF chart 300 is optimized, for example, by controlling the hexapod 145 and robot 140 holding the lens 120 of FIG. 1 . In one embodiment, software is used to analyze the local MTF response within a test image from the target to provide feedback for controlling the hexapod 145 to adjust the position of the lens 120.

[0025] The calibration process includes a convergence routine that uses data from the MTF chart 300 as a metric in determining the optimum position for the lens. In one embodiment, the convergence routine considers measurements from five targets: one in the center of the image and one in each of the four corners. In the illustrated example, the convergence routine determines the optimum position for 50 spatial frequencies where the received MTF value is approximately 0.2 for each MTF chart 300.

[0026] In one embodiment, the exact lens positioning 310 (eg, measured in millimeters and degrees from a reference point) is determined and saved for future reference.

[0027] FIG. 4 is an example flowchart 400 illustrating a method for mounting and aligning an infrared camera lens according to one embodiment.

[0028] At S410, an adhesive is applied to a lens configured for an infrared camera. The adhesive is formulated to harden (or set) upon exposure to a curing catalyst, such as ultraviolet (UV) light, a temperature change, a chemical reaction, etc. In one embodiment, the lens is handled by a robotic arm so that the adhesive is applied around the periphery of the lens.

[0029] In S420, the lens is placed over the camera body with the adhesive applied while still being held, for example, by a robotic arm, so that the positioning of the lens can still be adjusted by the robotic arm or a hexapod attached thereto while the adhesive has not yet cured.

[0030] In S430, an ideal lens position is determined based on the calibration target images and MTF charts associated with those targets, as described above in FIG. 3. The lens position is adjusted based on feedback from the MTF charts so that the resolution and contrast of the image from the camera in which the lens is located are maximized in all image regions, for example, the four corner regions and the center region with one region assigned to one calibration target. In one embodiment, if all MTF charts associated with each calibration target image cannot be maximized at a single position, the position that uniformly produces the best resolution and contrast among all calibration target images is used.

[0031] In S440, the position of the lens is adjusted based on the determined ideal position.

[0032] At S450, the adhesive is cured, securing the lens in place. In one embodiment, curing is achieved by exposing the adhesive to intense UV light from multiple directions to ensure uniform curing. In further embodiments, curing is achieved by alternative catalysts such as a visible light source, temperature change, or chemical reaction.

[0033] FIG. 5 illustrates an example setup for an infrared lens alignment system and curing light, according to one embodiment. A robotic arm 140 holds the lens 120 above a camera body 110, which includes an infrared image sensor (not shown). Multiple UV light sources 170, such as UV light-emitting diodes (LEDs), can be distributed (or scattered) around the lens 120 to provide an even amount of light. The UV light creates a photochemical process that hardens certain resins that can be used as adhesives for the lens 120. In one embodiment, four high-intensity spot curing LEDs operating at a wavelength of 365 nm are used. In further embodiments, other curing technologies, such as visible light curing, laser, halogen light, or tungsten light, can be used.

[0034] The various embodiments disclosed herein may be implemented as hardware, firmware, software, or any combination thereof. Furthermore, software is preferably implemented as an application program tangibly embodied on a program storage unit or computer-readable medium, consisting of a portion or a specific device and / or combination of devices. The application program may be uploaded to and executed by a machine having any suitable architecture. Preferably, the machine is implemented on a computer platform having hardware such as one or more central processing units, memory, and input / output interfaces. The computer platform may also include an operating system and microinstruction code. Various processes and functions described herein may be part of the microinstruction code, part of the application program, or any combination thereof, and may be executed by a CPU, whether or not such a computer or processor is explicitly described. Furthermore, various other peripheral units, such as additional data storage units and a printing unit, may be connected to the computer platform. Furthermore, a non-transitory computer-readable medium is any computer-readable medium except a transitory, propagating signal.

[0035] As used herein, the phrase "at least one of" can be followed by a list of items, meaning that any of the listed items can be utilized individually, or any combination of two or more of the listed items can be utilized. For example, if a system is described as including "at least one of A, B, and C," the system can include A alone, B alone, C alone, a combination of A and B, a combination of B and C, a combination of A and C, or a combination of A, B, and C.

[0036] All examples and conditional language recited herein are for educational purposes to aid the reader in understanding the principles of the disclosed embodiments and concepts contributed by the inventors to further the art, and should not be construed as being limited to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the disclosed embodiments, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Furthermore, such equivalents are intended to include both currently known equivalents and equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure. The following is the invention as originally described in the present application. <Claim 1> a lens support mechanism configured to adjust the position of the infrared camera lens relative to the camera body; at least one collimator configured to output infrared light, the at least one collimator positioned such that the output infrared light is focused through the infrared camera lens onto an infrared sensor in the camera body; a curing catalyst configured to cure an adhesive disposed on the infrared camera lens once an ideal lens position has been determined; 1. A system for optical alignment and calibration of an infrared camera lens, comprising: <Claim 2> The lens support mechanism further comprises: a robotic arm configured to manipulate the position of the infrared camera lens; a hexapod platform configured to move the robotic arm with six degrees of freedom; The system of claim 1 , comprising: <Claim 3> 3. The system of claim 2, wherein the hexapod platform is a Stewart platform having three pairs of actuators. <Claim 4> The system of claim 1 , wherein the at least one collimator comprises a blackbody configured as a calibration target for the infrared camera lens. <Claim 5> 5. The system of claim 4, wherein the lens support mechanism is configured to adjust the position of the infrared camera lens based on a modulation transfer function (MTF) chart associated with the calibration target. <Claim 6> The system of claim 1 , wherein the curing catalyst is an ultraviolet (UV) light source. <Claim 7> The system of claim 6 , further comprising a plurality of UV light sources evenly spaced around the camera body. <Claim 8> The system of claim 1 , wherein the curing catalyst comprises at least one of a visible light source, a temperature change, and a curing chemical reaction. <Claim 9> applying an adhesive to an infrared camera lens, the adhesive being configured to be cured by a curing catalyst; placing the infrared camera lens on a camera body using an adjustable arm; determining an ideal lens position based on at least a calibration target and an associated modulation transfer function (MTF) chart; adjusting the position of the infrared camera lens based on the determined ideal lens position; curing the adhesive with the curing catalyst to fix the infrared camera lens in place; 1. A method for optical alignment and calibration of an infrared camera lens, comprising: <Claim 10> The method of claim 9 , wherein determining the ideal lens position is based on optimizing resolution based on the MTF chart. <Claim 11> The method of claim 9 , wherein determining the ideal lens position is based on optimizing contrast based on the MTF chart. <Claim 12> 10. The method of claim 9, wherein the curing catalyst comprises at least one of an ultraviolet light source, a visible light source, a temperature change, and a curing chemical reaction.

Claims

1. a lens support mechanism configured to adjust the position of an infrared camera lens relative to a camera body, the infrared camera lens being attached to the camera body; and at least one collimator configured to output infrared light, the at least one collimator being positioned such that the output infrared light is focused through the infrared camera lens onto an infrared sensor in the camera body, the at least one collimator including at least one blackbody configured as a calibration target for the infrared camera lens; and means for causing curing configured to cure an adhesive disposed on the infrared camera lens once an ideal lens position has been determined. and, Equipped with The system for optical alignment and calibration of an infrared camera lens, wherein the adhesive, when hardened, is adapted to secure the infrared camera lens to the camera body, thereby holding the infrared camera lens in a determined ideal lens position.

2. The lens support mechanism further comprises: a robotic arm configured to manipulate the position of the infrared camera lens; a hexapod platform configured to move the robotic arm with six degrees of freedom; The system of claim 1 , comprising:

3. The system of claim 2 , wherein the hexapod platform is a Stewart platform having three pairs of actuators.

4. The system of claim 1 , wherein the lens support mechanism is configured to adjust the position of the infrared camera lens based on a modulation transfer function (MTF) chart associated with the calibration target.

5. The system of claim 1 , wherein the means for inducing curing is an ultraviolet (UV) light source.

6. The system of claim 5 , further comprising a plurality of UV light sources evenly spaced around the camera body.

7. The system of claim 1 , wherein the means for inducing curing comprises at least one of a visible light source, a temperature change, and a curing chemical reaction.

8. applying an adhesive to an infrared camera lens, the adhesive being configured to be cured using a means for causing curing; placing the infrared camera lens on a camera body using an adjustable arm; determining an ideal lens position using at least one collimator based on at least a calibration target and an associated modulation transfer function (MTF) chart, the at least one collimator configured to output infrared light, the at least one collimator positioned to focus the output infrared light through the infrared camera lens onto an infrared sensor in the camera body, the at least one collimator including at least one blackbody configured as a calibration target for the infrared camera lens; adjusting the position of the infrared camera lens based on the determined ideal lens position; curing the adhesive with a means for inducing said curing, and securing the infrared camera lens to the camera body, thereby holding the infrared camera lens in place, in the determined ideal lens position; 1. A method for optical alignment and calibration of an infrared camera lens, comprising:

9. The method of claim 8 , wherein determining the ideal lens position is based on optimizing resolution based on the MTF chart.

10. The method of claim 8 , wherein determining the ideal lens position is based on optimizing contrast based on the MTF chart.

11. The method of claim 8 , wherein the means for inducing curing comprises at least one of an ultraviolet light source, a visible light source, a temperature change, or a curing chemical reaction.

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