Integrated modeling and optical jitter analysis of a high resolution space camera

Space cameras play a pivotal role in various fields, such as astronomical exploration. When operating in orbit, these cameras encounter the relative motion between the target and the camera during the exposure, resulting in image motion, which affects the imaging quality. Therefore, it is necessary to compensate for this image motion. This paper investigates the in-orbit image motion compensation (IMC) method for space cameras with a long integration time based on a two-axis pointing platform. Firstly, the mechanical design of the camera is introduced. Secondly, the in-orbit IMC model for the camera is analyzed, and the angular motion needed for compensating for the image motion by the two-axis pointing platform are derived. Factors influencing the compensation accuracy are also analyzed. The effectiveness of the IMC model is verified through simulations. Finally, the in-orbit experimental results indicate that the energy concentration of the target star images obtained exceeded 70%, demonstrating excellent performance in space cameras and effectively enhancing imaging quality using IMC technology.

In response to the practical demands for a wide field of view (FOV), long exit pupil distance, and high image quality in head-mounted displays, an initial structure was built based on the principles of catadioptric lenses in a folded optical path (pancake optics) and the field curvature correction formula. Subsequently, using even-order aspheric surfaces, a VR optical system was developed with a FOV of 2w=110∘, an exit pupil distance of 15 mm, and an exit pupil diameter of 8 mm. Compared to traditional designs, a human eye model was introduced as the image plane to construct a VR-human eye optical system analysis model, allowing for direct analysis of the retinal image quality under different states of the human eye. After that, based on medical statistical data, the impact of different light intensity conditions on the retinal image quality of the VR optical system was explored. Experimental results showed that changes in light intensity affect the pupil diameter, which, in turn, influences the final image quality of the system. To solve the issues, two solutions were proposed: adjusting the screen distance and changing the lens spacing. Both methods significantly improved the imaging quality on the human retina, with an increase of over 30% in the average MTF value. A comparison of these methods was conducted, providing valuable references for future VR optical system designs.

It is often necessary in optical analysis software to trace millions of rays in order to determine flux transfer, color chromaticity, and the distributions of intensity, irradiance, or radiance onto one or more targets. The key question of "have I traced enough rays?" cannot be answered unless the statistical error in the final simulated result is below some measurement criteria; for instance, if you are to determine irradiance uniformity to less than 1%, having a 2% statistical error across the target will wash out what you are trying to analyze. Some optical analysis software packages do not provide error estimation methods, while others use error estimation algorithms having assumptions that are not valid for all cases. This paper describes how subdividing and recombining raytraces provides a robust method for estimating error. We will show that this error estimation technique can be used with most optical analysis packages and we will compare it with algorithms employed currently. Example systems will be analyzed and presented.

For the space solar extreme ultraviolet telescope, the star point test can not be performed in the x-ray band (19.5nm band) as there is not light source of bright enough. In this paper, the point spread function of the optical system is calculated to evaluate the imaging performance of the telescope system. Combined with the actual processing surface error, such as small grinding head processing and magnetorheological processing, the optical design software Zemax and data analysis software Matlab are used to directly calculate the system point spread function of the space solar extreme ultraviolet telescope. Matlab codes are programmed to generate the required surface error grid data. These surface error data is loaded to the specified surface of the telescope system by using the communication technique of DDE (Dynamic Data Exchange), which is used to connect Zemax and Matlab. As the different processing methods will lead to surface error with different size, distribution and spatial frequency, the impact of imaging is also different. Therefore, the characteristics of the surface error of different machining methods are studied. Combining with its position in the optical system and simulation its influence on the image quality, it is of great significance to reasonably choose the processing technology. Additionally, we have also analyzed the relationship between the surface error and the image quality evaluation. In order to ensure the final processing of the mirror to meet the requirements of the image quality, we should choose one or several methods to evaluate the surface error according to the different spatial frequency characteristics of the surface error.

In 1983, Rocketdyne Division of Rockwell International constructed the OASIS code in support of the Air Force to meet increasing needs for diffractive optical system analysis. The OASIS code (Optical Analysis Software for Interactive Systems) was developed to meet these needs in the context of new supercomputer environments. From its inception, the code was anticipated to be a highly interactive analysis tool featuring the basic required physics, plus generality and flexibility. A valuable teaching tool, the code is command line driven and offers complete documentation.

When a high-resolution satellite is imaging on orbit, the relative motion between the sensory optical elements inside the camera may be caused by micro-vibration, which results in degraded images. In order to study the effect of micro-vibration on high resolution satellite imaging, a micro-vibration analysis method of space camera based on target image is proposed in this paper. Firstly, the different factors of micro-vibration which will affect the image quality in different degrees are introduced. Then, the method which can realize the direct measurement of image motion in the image is proposed. The method can analyze the impact of micro-vibration on the space camera directly and get the accuracy number of the image motion, which can provide the basis for the influence analysis of the satellite image quality and the final correction. Finally, we take a factual space camera for example to calculate and analyze the test data by using this model on the condition of the satellite. We get the image motion set by the micro-vibration on focal plane and accomplish the influence analysis method of micro-vibration on high resolution satellite imaging. It is concluded that the proposed method is reasonable and practical. The method proposed by this paper can be referred to for improved design and vibration suppression.

In order to improve the safety and reliability and maintain the stability of imaging quality when a space camera with a cargo spaceship is launched, a protection system for the space camera is designed. Firstly, according to the mechanical properties of the space camera, a working principle of the protection system is elaborated, and a model of the system is proposed. Secondly, a protective cover and a vibration isolation block are designed on the basis of shape, size, and requirements of the space camera. Thirdly, based on the finite element mesh, static and sinusoidal vibration simulation calculations of the space camera and its protection system are carried out. Finally, the protection system is validated after mechanical experiment. The results reveal that the three directional fundamental frequencies of space camera are 43.39 Hz, 26.74 Hz, and 22.83 Hz, respectively, and the maximum response of sinusoidal vibration acceleration is 17.02 g, which is amplified by 3.4 times. The image quality of the space camera lens is consistent before and after the test, which satisfies the requirement of the cargo ship.

A comprehensive 4DCT QA program that includes the assessment of spatial integrity and image quality of 4D phantom scans can be resource-intensive, especially because the analysis burden scales with the number of motion traces used for QA. This work presents a streamlined and scalable workflow, enabled by the use of a widely available phantom and an automated analysis tool. For 4DCT imaging QA, the Catphan was placed on the QUASAR motion platform, driven with sinusoidal motion traces of various amplitudes and frequencies. The acquired image sets were automatically analyzed using a newly designed 4DCT analysis module in TotalQA. The metrics of interest for 4DCT QA were analyzed for image sets of all motion bins and compared to the stationary reference image set. Three broad categories of imaging tests for 4DCT QA were defined: spatial integrity, HU constancy, and image quality. The sensitometry plugs in the Catphan were used as motion surrogates for evaluating spatial integrity, including the dimensions of the plugs and the observed motion amplitude in the scans. HU values of the sensitometry plugs in different phases were evaluated for consistency. For image quality, spatial resolution, low contrast resolution, and image noise were evaluated. Compared to the stationary reference CT, spatial integrity was within ±1mm and the HU values were within two HU in the 4DCT for all phases. The spatial resolution was consistent while slightly higher noise was observed in the 4DCT images. The automated analysis in TotalQA was completed in approximately 20min per motion trace, improving efficiency by more than 80% compared to the manual workflow. A streamlined 4DCT imaging QA workflow with automated analysis offers a robust assessment of imaging quality and motion accuracy in 4DCT scans, enabling an efficient and consistent QA process in large healthcare networks.

We are developing a method to objectively quantify image quality and applying it to the optimization of fast magnetic resonance imaging methods. In MRI, to capture the details of a dynamic process, it is critical to have both high temporal and spatial resolution. However, there is typically a trade-off between the two, making the sequence engineer choose to optimize imaging speed or spatial resolution. In response to this problem, a number of different fast MRI techniques have been proposed. To evaluate different fast MRI techniques quantitatively, we use a perceptual difference model (PDM) that incorporates various components of the human visual system. The PDM was validated using subjective image quality ratings by naive observers and task-based measures as defined by radiologists. Using the PDM, we investigated the effects of various imaging parameters on image quality and quantified the degradation due to novel imaging techniques including keyhole, keyhole Dixon fat suppression, and spiral imaging. Results have provided significant information about imaging time versus quality tradeoffs aiding the MR sequence engineer. The PDM has been shown to be an objective tool for measuring image quality and can be used to determine the optimal methodology for various imaging applications.

PurposeTo assess the impact of prostate MRI image quality by means of the Prostate Imaging Quality (PI-QUAL) score, on the identification of extraprostatic extension of disease (EPE), predicted using the EPE Grade Score, Likert Scale Score (LSS) and a clinical nomogram (MSKCCn). MethodsWe retrospectively included 105 patients with multiparametric prostate MRI prior to prostatectomy. Two radiologists evaluated image quality using PI-QUAL (≥4 was considered high quality) in consensus. All cases were also scored using the EPE Grade, the LSS, and the MSKCCn (dichotomized). Inter-rater reproducibility for each score was also assessed. Accuracy was calculated for the entire population and by image quality, considering two thresholds for EPE Grade (≥2 and = 3) and LSS (≥3 and ≥ 4) and using McNemar’s test for comparison. ResultsOverall, 66 scans achieved high quality. The accuracy of EPE Grade ranged from 0.695 to 0.743, while LSS achieved values between 0.705 and 0.733. Overall sensitivity for the radiological scores (range = 0.235–0.529) was low irrespective of the PI-QUAL score, while specificity was higher (0.775–0.986). The MSKCCn achieved an AUC of 0.76, outperforming EPE Grade (=3 threshold) in studies with suboptimal image quality (0.821 vs 0.564, p = 0.016). EPE Grade (=3 threshold) accuracy was also better in high image quality studies (0.849 vs 0.564, p = 0.001). Reproducibility was good to excellent overall (95 % Confidence Interval range = 0.782–0.924). ConclusionAssessing image quality by means of PI-QUAL is helpful in the evaluation of EPE, as a scan of low quality makes its performance drop compared to clinical staging tools.

The American College of Radiology's (ACR) Nuclear Medicine and PET Accreditation Programs evaluate qualifications of personnel, equipment, image quality, and quality control measures. It is believed that these are primary factors that impact the quality of patient imaging. The ACR accreditation allows facilities to critique and improve their practices as part of their preparation for the accreditation evaluation process. The goals of the ACR Nuclear Medicine and PET Accreditation Programs are improvement in the quality of imaging, provision of educational information by raising awareness of imaging issues, and the recognition of imaging facilities which meet program objectives. This presentation will outline the program requirements, highlighting some of the common pitfalls that may cause deficiencies in both the clinical and phantom submissions.This presentation will provide participants with:1. General information describing the ACR Accreditation Programs2. Information about the Diagnostic Modality Accreditation Programs3. Specific information about the ACR Nuclear Medicine and PET Accreditation Program, to include the application process, clinical images submission and quality control requirements.

Dose reduction techniques for computed tomography angiography (CTA) in children with cardiovascular diseases have the potential of reducing risks of radiation-induced cancer. To evaluate effectiveness of these techniques, both radiation dose and image quality must be compared. While clinically practical methods of estimating effective dose are available, there are no generally accepted metrics for the assessment of image quality in CTA. We introduce a measurable and reproducible image quality index, CTA QI. Using this index, along with calculated effective dose, we test the hypothesis that volume scan CTA delivers comparable image quality at substantially reduced radiation dose when compared to helical CTA. CTA QI is a measure of intraluminal contrast variation in three-dimensions, and it is calculated from standardized measurements of means and standard deviations of Hounsfield units in the thoracic descending aorta. From institutional database, 83 studies of CTA for thoracic cardiovascular diseases were retrospectively identified. CTA QI values were independently measured by two radiologists and compared using correlation. CTA QI and DLP-derived effective dose were compared for the following groups: non-cardiac gated wide-detector and helical CTA, ECG-synchronized retrospective wide-detector and helical CTA, ECG-synchronized wide detector retrospective and target technique CTA. Statistical significance was evaluated with the Student-t test. The correlations of CTA QI values between the radiologists were 0.83 and 0.92 for non-gated studies and ECG-synchronized studies respectively. Comparing non-gated volume scan CTA to helical CTA, there was a radiation dose reduction of 69% (P < 0.0001) without a significant change in CTA QI (1.4 ± 1.0 vs. 1.9 ± 1.4, P = 0.13). Comparing retrospective ECG-synchronized wide-detector CTA to helical CTA, there was a radiation dose reduction of 46% (P < 0.0001) with and improvement in CTA QI (1.0 ± 0.8 vs. 3.7 ± 3.4, P < 0.01). Comparing ECG-synchronized wide-detector target CTA to retrospective CTA, there was a radiation dose reduction of 68% (P < 0.0001, but at the cost of a significant reduction in CTA QI (2.0 ± 1.0 vs. 0.8 ± 0.4, P < 0.0044). CTA QI is a simple, reproducible metric of image quality suited for comparing CTA studies. Using this quality index, we establish that CTA performed with wide-detector scan techniques can yield substantially lower radiation dose without compromising diagnostic imaging quality. A wide-detector target technique can further reduce effective dose compared to wide-detector retrospective ECG-synchronization, but with a reduction in image quality.

PurposeTo evaluate and compare the image quality and diagnostic accuracy of Artificial Intelligence-assisted Compressed Sensing (ACS) sequences for lumbar disease, as an acceleration method for MRI combining parallel imaging, half-Fourier, compressed sensing and neural network and routine 2D sequences for lumbar spine.MethodsWe collected data from 82 healthy subjects and 213 patients who used 2D ACS accelerated sequences to examine the lumbar spine while 95 healthy subjects and 234 patients used routine 2D sequences. Acquisitions included axial T2WI, sagittal T2WI, T1WI, and T2-fs sequences. All obtained images of these subjects were analyzed in the light of calculating image quality factors such as signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) for selected regions of interest. The lumbar image quality, artifacts and visibility of lesion structure were assessed by two radiologists independently. Differences between the evaluation values above were tested for statistical significance by the Wilcoxon signed-ranks test. Inter-observer agreements of image quality between two radiologists were measured using Cohen’s kappa correlation coefficient.ResultsThe ACS accelerated sequences not only reduced the scanning time by 18.9%, but also retained basically the same image quality as the routine 2D sequences in both healthy subjects and patients. Artifacts are less produced on ACS accelerated sequences compared with routine 2D sequences (p < 0.05). Apart from this, there were no significant differences in quantitative SNR, CNR measurements and qualitative scores within reviewing radiologists for each group (p > 0.05). Moreover, inter-observer agreement between two radiologists in scoring image quality was substantial consistently for ACS accelerated sequences and routine sequences (kappa = 0.622–0.986).ConclusionCompared with routine 2D sequences, ACS accelerated sequences allow for faster lumbar spine imaging with similar imaging quality and present reliable diagnostic accuracy, which can potentially improve workflow and patient comfort in musculoskeletal examinations.

Forensic oral imaging quality of hand-held dental X-ray devices: Comparison of two image receptors and two devices

The study proposes an optical optimal design system of light guide plate (LGP). The optimization design is conducted in the longitudinal structure of the LGP incidence plane with 3-piece LED light source. Taguchi method is also used in carrying out the design of experiment through the TracePro, optical analysis software, and the experiment data were employedd as the back-propagation neural network (BPNN) training and testing samples, and then created an optical quality predictor of the longitudinal structure; BPNN can predict the impact of incidence plane luminance versus the different constructed parameters. Finally, the optical quality predictor can effectively generate the optimal parameters settings combined with genetic algorithm (GA). The simulation results show that the proposed system improves the non-uniformity problem of the incidence plane but also makes it easier to design the longitudinal structure of the incidence plane.