Lens Barrel Research Articles

A portable S-DIMM developed for preliminary measurement of seeing for Solar Site Survey: Theory and one case study

Imaging quality is highly important for astronomical observations. The imaging quality of a telescope depends not only on the capabilities of the telescope itself but also on its location. When distant stars pass the atmosphere, due to the presence of atmospheric turbulence, the imaging quality becomes degraded. The atmospheric coherence length is the most commonly used parameter to evaluate the influence of the local atmospheric turbulence on telescopes. It is used to describe the degree of atmospheric attenuation of image quality. For the preliminary estimation of atmospheric daytime seeing from a lot of candidate sites, we have developed a portable S-DIMM (PS-DIMM),which is mainly composed of a light-duty tracking mount, a 9 cm aperture lens barrel and a Canon 60D SLR camera. With the PS-DIMM the daytime seeing of a site can be well estimated by measuring the relative displacement variance of the edge positions at both ends of the Sun’s diameter. The principle of PS-DIMM is introduced in this paper. The simultaneous seeing measurements by it and the traditional S-DIMM were carried out at the Fuxian Lake Solar Station, showing a very well correlated between them but with an offset of 2.6 cm. In contrast to the traditional S-DIMM, PS-DIMM offers the advantages of reduced weight and enhanced portability. The utilization of PS-DIMM has played an important role in the early stages of the site survey for the next-generation solar telescopes.

Analytical method for calculating internal stray radiation from an IR spectrometer based on the view factor.

Optomechanical components such as the lens barrels and frames of IR spectrometers produce strong internal stray radiation, which reduces the instrument's SNR and dynamic range. An IR internal stray radiation calculation method based on an analytical model of the view factor is proposed. The mathematical model of the view factor calculation method of typical optomechanical components is established. For any IR optical systems, the internal stray radiation can be quickly and accurately calculated by adjusting the coordinate systems in the calculation method. Based on the proposed method, the internal stray radiation of a double-pass long-wave IR spectrometer was calculated. The calculation results are consistent with the simulation results. The RMS value of the relative error between the calculated value and the simulated value is around 11%. To verify the proposed method, an experiment was conducted to test the internal stray radiation of the long-wave IR spectrometer. The internal stray radiation test results agree with the calculated and simulated results, and the relative error between the test results and the calculation results is within 9%.

Optomechanical design and analysis of lens assembly for space application

This study illustrates how commercial off-the-shelf optics may be employed in space exploration cameras. The most frequent loads on optical systems are self-weight, which is caused by gravitational orientations, vibration, and temperature ranges, which is caused by exposure to quickly changing temperatures ranging from extremely cold to very hot and during launch. This study describes the modulation transfer function (MTF) performance of the selected lens assembly, followed by a top-down method to disassemble the optical parts of the commercial lens housing. The lens enclosure was designed and modelled by retaining the interelement lengths determined from physical measurement. The performance of the lens barrel and optical elements have also been validated in ANSYS using a quasi-static loading and thermoelastic condition. As a post-performance assessment owing to stress and vibrations during satellite launch, a tilt-separation simulation was conducted. As a result of this research, it has been demonstrated that optomechanical design of commercial lens assembly is feasible for use in space application camera systems.

Experimental study on temperature uniformity and heat transfer performance of nitrogen loop heat pipe with large area and multi-heat source

• A large area loop heat pipe with multiple heat sources is designed. • The temperature uniformity and heat transfer performance are tested. • The heat pipe starts up and operates smoothly in anti-gravity. With the development of space technology, the requirements of thermal control on spacecraft are increasing. In space missions, due to the improvement of the detection accuracy, the diameter of deep space telescope is becoming larger and larger. These detection instruments need efficient and reliable thermal management. Thus, the application of the large-scale cryogenic cooling technology, which can provide heat dissipation for the continuous and long life of the detector, has become a difficult problem. In the present study, a large-area cryogenic loop heat pipe is designed for the optical telescope. It is a good combination of multi heat source and large-area cryogenic loop heat pipe. The main evaporator is cylindrical due to fit the lens barrel. The heat exchange area can reach 1 m 2 , and the average temperature performance is less than 5 K. The condenser adopts the form of parallel pipeline to further reduce the system resistance and ensure the smooth operation of loop heat pipe. Its operation stability and temperature uniformity of the main evaporator under different total loads are experimentally studied and analyzed. It is proved that the loop heat pipe is feasible for large area multi-heat source cryogenic loop heat pipe in engineering. It can also start up and run normally under anti-gravity conditions. The experimental results show that the large area multi-source heat collection cryogenic loop heat pipe can be started and run normally in the temperature range of 80–120 K.

Coaxiality Optimization Analysis of Plastic Injection Molded Barrel of Bilateral Telecentric Lens

Plastic optical components are light in weight, easy to manufacture, and amenable to mass production. However, plastic injection molded parts are liable to shrinkage and warpage as a result of the pressure and temperature variations induced during the molding process. Consequently, controlling the process parameters in such a way as to minimize the geometric deformation of the molded part and improve the performance of the optical component as a result remains an important concern. The present study considered the problem of optimizing the injection molding parameters for the plastic lens barrel of a bilateral telecentric lens (BTL) containing four lens assemblies. The study commenced by using CODE V optical software to design the lens assemblies and determine their optimal positions within the barrel. Taguchi experiments based on Moldex3D simulations were then performed to determine the processing conditions (i.e., maximum injection pressure, maximum packing pressure, melt temperature, mold temperature, and cooling time) which minimize the coaxiality of the plastic barrel. Finally, CODE V and grayscale analyses were performed to confirm the optical performance of the optimized BTL. The Taguchi results show that the coaxiality of the plastic lens barrel is determined mainly by the maximum packing pressure and melt temperature. In addition, the CODE V and grayscale analysis results confirm that the optimized BTL yields a better modulus transfer function, spot diagram performance, and image quality than a BTL produced using the general injection molding parameters.

Stray light analysis by ray tracing simulation for the wide-angle multiband camera OROCHI onboard the Martian Moons eXploration (MMX) spacecraft

• Ray tracing analysis was conducted to reduce stray light of OROCHI onboard the MMX. • OROCHI’s optical system is simulated and its CCD reflectance was measured. • Our techniques are incorporated into the preliminary design of OROCHI. The Martian Moons eXploration (MMX) spacecraft is equipped with two cameras, i.e., the TElescopic Nadir imager for GeOmOrphology (TENGOO) and the Optical Radiometer composed Of CHromatic Imagers (OROCHI), for the scientific observation of the Martian moon Phobos. OROCHI is a wide-angle multiband camera system comprising seven cameras with different bandpass filters and one monochromatic camera in the visible and near-infrared range. Thus, OROCHI can simultaneously obtain multiband images. Previous space observations have revealed that the reflection spectra of Phobos exhibit regional differences, including a red unit and a blue unit with weak redness. Moreover, Phobos shows an absorption band near 650 nm, attributed to the red unit of Phobos. Global observations using OROCHI require the determination of such regional variations with high precision; therefore, we must reduce noise in the optical system design. In this study, to meet this requirement, we focus on stray light reduction. Stray light is a source of noise generated by reflections at surfaces of optical components (e.g., sensors, filters, lenses, and lens barrels). We design simulation models of the OROCHI optical system, measure the reflectance of its charge-coupled device (CCD) image sensor, and conduct stray light analysis via ray tracing. We estimate the ratio of the stray light intensity to the target signal intensity by deriving both the reflected (constituting stray light) and unreflected rays. We show that placing the filter away from the sensor and reducing the reflectances of the filter and lenses effectively reduce stray light. Such approaches are incorporated into the preliminary design of OROCHI.

Taguchi Optimization of Roundness and Concentricity of a Plastic Injection Molded Barrel of a Telecentric Lens.

Plastic is an attractive material for the fabrication of tubular optical instruments due to its light weight, high strength, and ease of processing. However, for plastic components fabricated using the injection molding technique, roundness and concentricity remain an important concern. For example, in the case of a telecentric lens, concentricity errors of the lens barrel result in optical aberrations due to the deviation of the light path, while roundness errors cause radial stress due to the mismatch of the lens geometry during assembly. Accordingly, the present study applies the Taguchi design methodology to determine the optimal injection molding parameters which simultaneously minimize both the overall roundness and the overall concentricity of the optical barrel. The results show that the geometrical errors of the optical barrel are determined mainly by the melt temperature, the packing pressure, and the cooling time. The results also show that the optimal processing parameters reduce the average volume shrinkage rate (from 4.409% to 3.465%) and the average deformations from (0.592 mm to 0.469 mm) of the optical barrel, and the corresponding standard deviation values are reduced from 1.528% to 1.297% and from 0.263 mm to 0.211 mm, respectively. In addition, the overall roundness and overall concentricity of the barrel in the four planes are positively correlated.

Design of a passive optical athermalization of dual-band IR seeker for precision-guided systems

The optical design of a seeker, operating in two bands of infrared (MWIR-LWIR), is performed. The dual-band design has been developed on Zemax OpticStudio. Considering the optical parameters of commercially available dual-band IR detectors, the design of the IR imaging seeker is completed for the operation within the wavelength range of 3–10 µm. The temperature dependence of the optical design is also examined for four different lens barrel materials, for the large temperature interval ranging from −40°C to 80°C. The defocusing effect caused by using different lens barrel is fixed by the passive-optical-athermalization technique. The field of view of the optical system is found to be 16°. The modulation transfer function (MTF) value of each field is higher than 0.50 when the spatial frequency takes a value of 20.8 lp/mm. The results are analyzed and discussed in terms of spot diagram, MTF.

Experimental Study and Application Prospect Analysis of Truss Heat Pipes for Space Optical Cameras

To meet the application requirements of space optical cameras, the concept of a truss heat pipe is proposed in this paper. This truss heat pipe is composed of multiple (two or more) heat pipe shells with inner capillary wicks connected to each other by special joints with additional inner capillary wicks. It can be assembled into a variety of truss structures according to the layout requirements of the structure. Truss heat pipes can be used as the supporting structure of space optical cameras and can simultaneously efficiently transfer heat and maintain an even temperature, conserving the thermal control resources of space optical cameras. The function and performance of truss heat pipes were verified through tests of a single T-joint prototype and a multi T-joint prototype. Two truss heat pipes were then applied to the thermal management of a space optical camera. The thermal vacuum test results show that as the supporting structure of the front lens barrel heat shields, the two truss heat pipes can transfer heat from the space optical camera heat source to the front lens barrel heat shield both efficiently and evenly. This indicates that truss heat pipes can meet the requirements of the structure-thermal integrated design and thermal management of space optical cameras. As a new thermal control technology and product, truss heat pipes have the potential for broad applications in many aerospace fields in the future.

Discussion of temperature, TV distortion, and lateral color of a 4-megapixel DLP projector lens

This paper explores lens design through thermal analysis and correction of 4-megapixel DLP projector lenses at temperatures ranging from 10°C to 80°C, and analyzes and discusses the TV distortion and lateral color with a focal length of 24 mm, F/# of 1.71, projection distance of 7.2 m, and projection screen size of 200 inches. Appropriate lens materials are selected and changes are made to the lens barrel materials to achieve athermalization. At temperatures from 10°C to 80°C, the image quality of lens is as follows: MTF (93 lp/mm) is greater than 0.554, lateral color is less than 1.39 µm, optical distortion is less than 0.147%, TV distortion is less than 0.079%, and relative illumination less than 92.52%.

A Smartphone-Based Whole-Cell Array Sensor for Detection of Antibiotics in Milk.

We present an integral smartphone-based whole-cell biosensor, LumiCellSense (LCS), which incorporates a 16-well biochip with an oxygen permeable coating, harboring bioluminescent Escherichia coli bioreporter cells, a macro lens, a lens barrel, a metal heater tray, and a temperature controller, enclosed in a light-impermeable case. The luminescence emitted by the bioreporter cells in response to the presence of the target chemicals is imaged by the phone’s camera, and a dedicated phone-embedded application, LCS_Logger, is employed to calculate photon emission intensity and plot it in real time on the device’s screen. An alert is automatically given when light intensity increases above the baseline, indicating the presence of the target. We demonstrate the efficacy of this system by the detection of residues of an antibiotic, ciprofloxacin (CIP), in whole milk, with a detection threshold of 7.2 ng/mL. This value is below the allowed maximum as defined by European Union regulations.

Optical design of a 2× zoom lens for miniature imaging systems

The optical design of a compact 2 × zoom lens in a lens barrel for miniature cameras is reported. The magnification in the optical system is achieved by means of changing positions of lens elements inside the lens barrel. Six lens elements are employed in the optical system, where up to four elements are actuated. Maximum travel distances for the moving parts are determined as 1.67 mm to reach a magnification of 2.06 × , and the total track length for the telephoto zoom lens state is 9.16 mm at its most extended configuration. Manufacturability of the proposed system is also discussed using a tolerance analysis. The designed optical system is suitable for use with image sensors up to 13 MP, and it can be employed in an endoscopic camera, where the optical zoom and compact design are beneficial. It is also suitable for smartphone cameras with further enhancements and integration of voice-coil-motors and/or MEMS actuators.

Lens rim points stitching algorithm based coaxial alignment micro assembly

Optical lens assemblies are used more and more widely, and assembly and alignment processes are key to affecting lens accuracy. Considering that the common way of assembling lenses was manual, the coaxial alignment for intermediate-scale parts was considered to be a good alternative, which could improve the accuracy of assembly effectively. But it was difficult to capture the full edge of the lens in one image because of the limit of the CCD camera field of view. To solve this problem, a rim points stitching algorithm was proposed, and the barrel and lens were imaged by the camera at three different position. After the rim points were extracted from the three images, all the rim points were stitched according to the position of the camera at three locations. The rim points stitched were fitted to two circles by using the least squares method. Finally, according to the adjustment algorithm, the adjustment amount of the lens with respect to the lens barrel was calculated. Experimental results showed that this method could align lenses with the diameter greater than 60mm. The technique has the potential to be applied in automated alignment of lens assemblies.

Alignment turning system for precision lens cells

This research increases the ability and value of a traditional vertical lathe and applies to manufacture a precise lens cell for the optical industry. The optical performance is limited by the residual centration error and position accuracy of conventional assembly methods. Recently, the development of a poker-chip assembly system with high-precision lens barrels has overcome these limitations and provided a solution for ultra-high-performance optical systems. To develop a high-precision lens cell by using poker-chip assembly, an alignment turning system (ATS), is developed based on a vertical lathe and equipped with tactile and optical measurement modules. Inside the ATS, the building-in the vibration/temperature monitoring sensors, which help to self-monitoring and network communication with the intelligent manufacturing techniques, to understand and master the reliability and efficiency of ATS. This system can manufacture precise lens cells, applied for optical metrology, high numerical aperture objective lenses, and lithography projection lenses. This paper describes the design and development of the ATS and its capabilities. The ATS is composed of measurement, alignment, and turning modules. After the ATS completes the measurement, alignment, and turning processes, the centration error of a lens cell, which is 200 mm in diameter, can be controlled to within 10 arcsec. Here, a lens cell with three subcells was assembled through the poker-chip method; each subcell was measured and then it underwent alignment and turning processes. The lens assembly test was performed five times by three technicians, and the average transmission centration error of the assembly lens was 12.45 arcsec. The results demonstrate that the ATS can achieve considerable assembly efficiency for high-precision optical systems.

The Precise Detection Techniques in Optical Lenses Alignment

For the high-precision optical lens alignment, the coaxiality of the mechanical axes of the optical components and the lens barrel cannot guarantee good optical performance. As the centering error’s existence of the optical lens, the optical axis of the lens is supposed to be detected to ensure the centering error in required range. The precise detection techniques of mechanical axis and optical axis of the optical component are put forward. Then, the mechanical axis and optical axis integrated precision detection system (MOADS for short) is proposed. Based on the MOADS, the alignment process of optical lenses is put forward.

Endoscopic characteristics of the early gastroesophageal junctional cancer: an analysis of 53 cases

Objective To investigate the endoscopic characteristics of early gastroesophageal junctional(GEJ) cancer to improve the diagnostic procedure and techniques of endoscopy. Methods Data of 53 cases were retrospectively analyzed which were endoscopically and histologically diagnosed as early GEJ cancer in the gastrointestinal endoscopy center of the Second Affiliated Hospital of Zhengzhou University and No. 152 hospital of The PLA from November 2011 to July 2015. The lesion characteristics, features of white light endoscopy(WLE) and magnifying endoscopy with narrow band imaging(ME-NBI) and the clinicopathological features were analyzed. Results In early GEJ cancer, 67.9%(36/53) were classified as Siewert type 2, and 58.3%(21/36) located in the posterior wall below cardiac region(P=0.028). The main endoscopic type were Type 0-II(94.3%, 50/53), and Type 0-II accounted for 97.2%(35/36) of Siewert type 2 lesions. The lens barrel need to be reversed to view the whole pictures of Type0-II lesions, and positive lens barrel were needed in a small number of lesions. The lesion mucosa showed flushing(90.6%, 48/53), roughness(79.2%, 42/53), erosion(35.8%, 19/53) under the WLE. The submucosal microvessel were irregular or disappeared in 96.7%(29/30), the epithelial microstructure and pit patterns were irregular or disappeared in 90.0%(27/30), and boundaries of 86.7%(26/30) lesions were clear under the ME-NBI. The Barrett esophagus accompanied with Siewert type 1, 2 and 3 accounted for 83.3%(5/6), 11.1%(4/36) and 9.1%(1/11) respectively with significant difference(P=0.011). The ratio of the intestinal metaplasia with Siewert type 1, 2 and 3 lesions were 16.7%(1/6), 75.0%(27/36) and 63.6%(7/11) respectively, and there was significant difference between type 1 and type 2(P=0.011). Conclusion The Siewert type 2 is more common among the early GEJ cancer. Most of the lesions are shown the Type 0-II and located in the posterior wall below cardiac region. The mucosa lesions appear flushing, rough, erosion under WLE. The submucosal microvessel, epithelial microstructure and pit patterns appear irregular or disappeared, and lesions boundaries are clear under ME-NBI. Siewert type 1 tends to be complicated with Barrett esophagus, and Siewert type 2 and 3 tend to be complicated with intestinal metaplasia. Key words: Endoscopy; Esophagogastric junction; Early cancer; Narrow band imaging

A Small Axial-Flux Vernier Machine With Ring-Type Magnets for the Auto-Focusing Lens Drive System

A small axial-flux permanent magnet vernier motor (PMVM) is investigated to satisfy the requirements of high drive torque, low speed, low noise, and low-power consumption for application in the camera auto-focusing lens drive. The proposed axial-flux PMVM is constructed with ring-type magnets in the rotor and has strict dimensional constraints due to its location in the lens barrel. The design approach is an alternative motor design method coupled with the analytical method or the finite-element method. The proposed motor’s electromagnetic performance was verified by means of both methods. Finally, a prototype was built and tested, showing an adequate range of speed while also meeting the noise limits, and consuming less than 2 W of power.

带高增益观测器的高精度镜筒定位系统

By taking a long focal length oblique CCD camera as an object of study, a multiple loop control scheme based on the high gain observer was proposed to improve the position accuracy of auto-collimating auto-focusing lens barrel in a high dynamic state. Firstly, a mathematical model was established according to the open-loop amplitude-frequency characteristic curve of a depression angle control system. The feasibility of control scheme was analyzed by the control theory and the simulation tests were adequately performed. Then the reliability of control scheme was further validated through the practice control system. The experimental results show that the high gain observer can estimate the angle speeds and angle acceleration well. As compared with the double closed loop control method, this proposed control scheme reduces the maximum position control disturbance error by 96.3% and ensures the requirement of lens barrel positioning precision within 0.05. Hence the new control method is valuable in practical engineering applications.

Lens barrel heat transfer: An improvement method

The speedy movement of an aerial camera needs its lens barrel to have good capability of heat transfer to meet the temperature needs of the optics. This paper describes a method, with minor change of the original design, to improve a lens barrel's heat transfer. Compared with the original design, the current method costs less but greatly ameliorates the temperature uniformity. An experiment was designed to obtain the coefficient of thermal contact resistance between titanium alloy and Carbon–Carbon composite material. The coefficient was then used in a finite element thermal model. The thermal behavior was predicted by using an analysis software (IDEAS). After that, an experiment was done in the same condition of the prediction. The max temperature difference between prediction and the experimental results is less than 1 °C.

Thermal optical path difference analysis of the telescope correct lens assembly

Abstract The effect of correct lens thermal optical path difference (OPD) on the optical performance of the Cassegrain telescope system is presented. The correct lens assembly includes several components such as a set of correct lenses, lens mount, spacer, mount barrel, and retainer. The heat transfer from the surrounding environment to the correct lens barrel will cause optical system aberration. The temperature distribution of the baffle is from 20.546°C to 21.485°C. Meanwhile, the off-axis ray’s path of the OPD has taken the lens incidence point and emergence point into consideration. The correct lens temperature distribution is calculated by the lens barrel heat transfer analysis; the thermal distortion and stress are solved by the Finite Element Method (FEM) software. The temperature distribution is weighted to each incidence ray path, and the thermal OPD is calculated. The thermal OPD on the Z direction is transferred to optical aberration by fitting OPD into a rigid body motion and the Zernike polynomial. The aberration results can be used to evaluate the thermal effect on the correct lens assembly in the telescope system.