A new enhancement method is proposed based on the characteristics of fundus images in this paper. Firstly, top-hat transform is utilized to weaken the background. Secondly, contrast limited adaptive histogram equalization (CLAHE) is performed to improve the uneven illumination. Finally, two-dimensional matched filters are designed to further enhance the contrast between blood vessels and background. The algorithm was tested in DIARETDB0 databases and showed good applicability for both normal and pathological fundus images. A new no-reference image quality assessment method was used to evaluate the enhancement methods objectively. The results demonstrated that the proposed method could effectively weaken the background, increase contrast, enhance details in the fundus images and improve the image quality greatly.
This study was aimed to use the method of modulation transfer function (MTF) to compare image quality among three different Olympus medical rigid cystoscopes in an in vitro model.During the experimental processes, we firstly used three different types of cystoscopes (i.e. OLYMPUS cystourethroscopy with FOV of 12°, OLYMPUS Germany A22003A and OLYMPUS A2013A) to collect raster images at different brightness with industrial camera and computer from the resolution target which is with different spatial frequency, and then we processed the collected images using MALAB software with the optical transfer function MTF to obtain the values of MTF at different brightness and different spatial frequency.We then did data mathematical statistics and compared imaging quality.The statistical data showed that all three MTF values were smaller than 1.MTF values with the spatial frequency gradually increasing would decrease approaching 0 at the same brightness.When the brightness enhanced in the same process at the same spatial frequency, MTF values showed a slowly increasing trend.The three endoscopes' MTF values were completely different. In some cases the MTF values had a large difference, and the maximum difference could reach 0.7. Conclusion can be derived from analysis of experimental data that three Olympus medical rigid cystoscopes have completely different imaging quality abilities. The No.3 endoscope OLYMPUS A2013A has low resolution but high contrast. The No.1 endoscope OLYMPUS cystourethroscopy with FOV of 12°, on the contrary, had high resolution and lower contrast. The No.2 endoscope OLYMPUS Germany A22003A had high contrast and high resolution, and its image quality was the best.
In order to overcome the influence of stray light and impurity on the image of video laryngoscope, we designed an optical structure by using TracePro, a simulation software, to imitate optical path status. Images are captured by CMOS sensor which has the size of 4.5 mm×18 mm and the pixel size is 1.75 μm×1.75 μm. The sensor is placed in the elbow of the laryngoscope, and the elbow has the size of 9 mm×10 mm. As a result, the video laryngoscope could meet the requirements, including wide viewing angle (80°), short focal length (2.8 mm), long working distance (10 cm), and least impurity. In the test, the image was clear and there was no facula or impurity in the condition of required illumination, and thus stray light and image impurity were eliminated and the image quality was improved.