scholarly journals Blank-field correction for achieving a uniform white background in brightfield digital photomicrographs

BioTechniques ◽  
2007 ◽  
Vol 42 (6) ◽  
pp. 716-720 ◽  
Author(s):  
Gary D. Marty
Keyword(s):  
White Background ◽  
Blank Field

scholarly journals Experimental Evaluation of Computer Vision and Machine Learning-Based UAV Detection and Ranging

Drones ◽  
2021 ◽  
Vol 5 (2) ◽  
pp. 37
Author(s):  
Bingsheng Wei ◽  
Martin Barczyk
Keyword(s):  
Machine Learning ◽  
Mean Squared Error ◽  
Tracking System ◽  
Ground Truth ◽  
White Background ◽  
Cascade Classifier ◽  
Detection Algorithms ◽  
Squared Error ◽  
Test Conditions ◽  
Video Feed

We consider the problem of vision-based detection and ranging of a target UAV using the video feed from a monocular camera onboard a pursuer UAV. Our previously published work in this area employed a cascade classifier algorithm to locate the target UAV, which was found to perform poorly in complex background scenes. We thus study the replacement of the cascade classifier algorithm with newer machine learning-based object detection algorithms. Five candidate algorithms are implemented and quantitatively tested in terms of their efficiency (measured as frames per second processing rate), accuracy (measured as the root mean squared error between ground truth and detected location), and consistency (measured as mean average precision) in a variety of flight patterns, backgrounds, and test conditions. Assigning relative weights of 20%, 40% and 40% to these three criteria, we find that when flying over a white background, the top three performers are YOLO v2 (76.73 out of 100), Faster RCNN v2 (63.65 out of 100), and Tiny YOLO (59.50 out of 100), while over a realistic background, the top three performers are Faster RCNN v2 (54.35 out of 100, SSD MobileNet v1 (51.68 out of 100) and SSD Inception v2 (50.72 out of 100), leading us to recommend Faster RCNN v2 as the recommended solution. We then provide a roadmap for further work in integrating the object detector into our vision-based UAV tracking system.

Color stimuli perception in presence of light scattering

2006 ◽  
Vol 23 (3-4) ◽  
pp. 597-601 ◽  
Author(s):  
MARIS OZOLINSH ◽  
MICHÉLE COLOMB ◽  
GATIS IKAUNIEKS ◽  
VARIS KARITANS
Keyword(s):  
Visual Acuity ◽  
Light Scattering ◽  
Luminance Contrast ◽  
White Background ◽  
Color Contrast ◽  
Entire Area ◽  
Red Color ◽  
Blue Component ◽  
Different Color ◽  
Landolt C

Perception of different color contrast stimuli was studied in the presence of light scattering: in a fog chamber in Clermont-Ferrand and in laboratory conditions where light scattering of similar levels was obtained, using different light scattering eye occluders. Blue (shortest wavelength) light is scattered in fog to the greatest extent, causing deterioration of vision quality especially for the monochromatic blue stimuli. However, for the color stimuli presented on a white background, visual acuity in fog for blue Landolt-C optotypes was higher than for red and green optotypes on the white background. The luminance of color Landolt-C optotypes presented on a LCD screen was chosen corresponding to the blue, green, and red color contributions in achromatic white stimuli (computer digital R, G, or B values for chromatic stimuli equal to RGB values in the achromatic white background) that results in the greatest luminance contrast for the white–blue stimuli, thus advancing the visual acuity for the white-blue stimuli. Besides such blue stimuli on the white background are displayed with a uniform, spatially unmodulated distribution of the screen blue phosphor emission over the entire area of the screen including the stimulus C optotype area. It follows that scattering, which has the greatest effect on the blue component of screen luminance, has the least effect on the perception of white–blue stimuli.

The Influence of Perceived Colours Over the Reaction Accuracy of Youth Tennis Players

2020 ◽  
Vol 65 (4) ◽  
pp. 91-96
Author(s):  
Cosmin Miha Moca ◽  
Dan Mihai Gherţoiu
Keyword(s):  
Reaction Time ◽  
Motor Response ◽  
External Stimulus ◽  
White Background ◽  
Tennis Players ◽  
Voluntary Response ◽  
Time Period ◽  
Significant Difference

ABSTRACT. Introduction. Reaction is a purposeful voluntary response to an external stimulus. There is certain time period between application of external stimulus and appropriate motor response to the stimulus called the reaction time. Objectives. The aim of this paper was to determine if different colour contrasts affects the reaction time of young tennis players. Materials and Methods. The participants in this study were young tennis players (N = 10), 3 females and 7 males, with the ages between 12 to 13 years old. Results. There was a significant difference in the scores for white background (M=7.5, SD=1.51) and orange background (M=6, SD=0.81) conditions; t(9)=3.30, p = 0.009. Conclusion. Our study managed to show that a different kind of background colour can affect the reaction accuracy in identifying an object of different shape and colour than the background.

scholarly journals Effects of Line Spacing on Reading Performance of Normally Sighted and Simulated Visually-Impaired Subjects: A Pilot Study Using Arabic Words

2017 ◽  
Vol 9 (8) ◽  
pp. 84
Author(s):  
Abdullah Z. Alotaibi
Keyword(s):  
Visually Impaired ◽  
Low Vision ◽  
Reading Rate ◽  
Reading Performance ◽  
White Background ◽  
Significant Difference ◽  
Line Spacing ◽  
The Difference ◽  
Letter Size ◽  
Visually Impaired Persons

The study aims to evaluate the role of line spacing during reading in normal and visually-impaired persons. A total of 225 normally-sighted participants with mean age of 23.7 years were asked to read Arabic sentences in a randomized order. Each Arabic sentence contains 7 lines with and without simulated cataract. The words were printed with black letters on white background to enhance contrast and fonts were in Times New Roman and of N12 letter size. The reading pages were placed on reading stand situated 25 cm away from the subject’s eyes. The simulated cataract was created by using a Bernell Cling Patch Occluder. This reduced the visual acuity of all subjects to 20/60. Each line of the text was separated by different line spacing namely: single space, 1.5, 2.0, 2.5, 3.0 and 4.0 which represents, 0.5 cm, 0.8 cm, 1.1 cm, 1.4 cm, 1.7 cm and 2.0 cm, respectively. The sheets were presented randomly and participants’ voices were recorded as they read under a controlled time. The tape was analysed later and reading rate was calculated. There was a significant difference (p<0.0001) in reading rates between the normal sighted persons and the visually impaired persons for all line spacing. Modifying the spacing between lines in prints had a significant impact (p<0.0001) on the reading rate of the visually impaired but not in normally-sighted persons (p˃0.05). Intermediate line spacing (2 and 2.5) increased the reading rate of the visually impaired persons significantly more (p<0.001) than other line spacing, but smaller or larger line spacing slowed their reading rate, significantly (p<0.001). The visually-impaired persons reported that they felt the difference in reading prints with larger line spacing as compared with normal sighted participants who did not. It is beneficial to adequately modify the line spacing in prints commonly read by low vision persons. For Arab subjects the optimum line spacing to significantly improve reading in the visually impaired should range from 0.8 to 1.1 cm. This finding may be a useful for publishers of Arab prints targeting the visually impaired persons. Thus, the implication of the study in the field of health is that by establishing the least common line spacing visualized optimally among normal and simulated visually impaired persons would be fixed as default line spacing for Arab printing to achieve better reading performance.

Traffic Signal Color Recognition Is a Problem for Both Protan and Deutan Color-Vision Deficients

2003 ◽  
Vol 45 (3) ◽  
pp. 495-503 ◽  
Author(s):  
David A. Atchison ◽  
Carol A. Pedersen ◽  
Stephen J. Dain ◽  
Joanne M. Wood
Keyword(s):  
Color Vision ◽  
Response Times ◽  
Reaction Times ◽  
Error Rates ◽  
Traffic Signal ◽  
White Background ◽  
Signal Design ◽  
Traffic Light ◽  
Light Signals ◽  
Signal Color

We investigated the effect of color-vision deficiency on reaction times and accuracy of identification of traffic light signals. Participants were 20 color-normal and 49 color-deficient males, the latter divided into subgroups of different severity and type. Participants performed a tracking task. At random intervals, stimuli simulating standard traffic light signals were presented against a white background at 5° to right or left. Participants identified stimulus color (red/yellow/green) by pressing an appropriate response button. Mean response times for color normals were 525, 410, and 450 ms for red, yellow, and green lights, respectively. For color deficients, response times to red lights increased with increase in severity of color deficiency, with deutans performing worse than protans of similar severity: response times of deuteranopes and protanopes were 53% and 35% longer than those of color normals. A similar pattern occurred for yellow lights, with deuteranopes and protanopes having increased response times of 85% and 53%, respectively. For green lights, response times of all groups were similar. Error rates showed patterns similar to those of response times. Contrary to previous studies, deutans performed much worse than protans of similar severity. Actual or potential applications of this research include traffic signal design and driver licensing.

scholarly journals Pengolahan Citra Digital untuk Keyboard Virtual Sebagai Antarmuka pada Aplikasi Berbasis Web

2015 ◽  
Vol 5 (2) ◽  
pp. 111
Author(s):  
Raksaka Indra Alhaqq ◽  
Agus Harjoko
Keyword(s):  
Image Processing ◽  
Web Application ◽  
Index Finger ◽  
Processing Technology ◽  
White Background ◽  
Cascade Classifier ◽  
Virtual Keyboard ◽  
Image Processing Technology ◽  
Optimal Distance ◽  
Haar Cascade

AbstrakSejak pertama kali komputer ditemukan, keyboard selalu menjadi alat utama yang menjadi penghubung interaksi antara manusia dan komputer. Saat ini banyak komputer yang menerapkan teknologi pengolahan citra untuk menjadikannya perantara interaksi antara komputer dan manusia.Dalam penelitian ini, penulis mencoba untuk menerapkan teknologi pengolahan citra yang digunakan untuk keyboard virtual pada aplikasi web. Digunakan webcam untuk menangkap citra ujung jari telunjuk. Hasil capture citra akan dikirimkan ke server localhost untuk diproses dengan image processing. Untuk mendeteksi ujung jari telunjuk, digunakan metode Haar Cascade Classifier. Proses pendeteksian tersebut menghasilkan koordinat yang akan dikirimkan ke aplikasi web yang selanjutnya dijadikan acuan untuk menentukan posisi tombol pada keyboard virtual. Sehingga keyboard virtual akan menampilan karakter sesuai dengan yang ditunjuk oleh ujung jari telunjuk.Dari hasil pengujian yang dilakukan, jarak optimal ujung jari telunjuk dengan webcam adalah 20 – 35 cm. Derajat kemiringan ujung jari telunjuk untuk dapat terdeteksi antara 0° – 10°. Sistem mampu mengenali ujung jari telunjuk pada ruangan berlatar belakang putih polos dan terdapat sedikit perabot. Waktu respon untuk menampilkan karakter keyboard virtual rata-rata 5,156 detik. Sehingga keyboard virtual pada sistem ini belum mampu dijadikan antarmuka pada aplikasi web, dikarenakan masih sulit digunakan dalam mengarahkan ujung jari telunjuk ke tombol karakter yang diinginkan.Kata kunci—aplikasi web, Haar Cascade Classifier, keyboard virtual, pengolahan citra  AbstractSince the first computer was founded, keyboard is always been a primary tool for interaction between humans and computers. Today, many computers use image processing technology to make interaction between computers and humans.The author try to apply image processing technology that implemented to virtual keyboard on web application. Using a webcam to capture the tip of index finger and the results will be sent to the localhost server for processing with image processing. Using Haar Cascade Classifier method to detect the tip of index finger, it will produce coordinates that sent to the web application and it used as a reference for determining button positions on virtual keyboard. Virtual keyboard characters will display after appointed by the tip of  index finger.From testing results, optimal distance from index finger to webcam is 20 – 35 cm. System can recognize the tip of index finger on white background and room with few furnitures. Average response time for displaying virtual keyboard sentences is 3 minutes and 28.838 seconds. So the virtual keyboard on this system was not able to be used as interface on web application, because it difficult to use in directing the tip of index finger to the character keys.Keywords—web application, Haar Cascade Classifier, virtual keyboard, image processing

Differential effects of diurnal and continuous illumination regimes on melanophores and xanthophores of winter flounder, Pseudopleuronectes americanus

1987 ◽  
Vol 65 (5) ◽  
pp. 1140-1143 ◽  
Author(s):  
D. Burton
Keyword(s):  
Winter Flounder ◽  
Continuous Illumination ◽  
White Background ◽  
Pseudopleuronectes Americanus ◽  
Differential Effects ◽  
Background Adaptation ◽  
Significant Difference ◽  
Pigment Aggregation ◽  
High Degree ◽  
Final Degree

The melanophores and xanthophores of Pseudopleuronectes americanus display different adaptive capacities to a white background under continuous (1 week) illumination compared with an equivalent period under diurnal, alternating light (12 h) and dark (12 h) photoperiods. Under the repeated diurnal photocycles on white, melanosomes partly disperse during dark photoperiods, but there is cumulative melanosome aggregation during successive light photoperiods that is interpreted as a slow physiological summation. Consequently, there is no significant difference in the final degree of aggregation attained on a white background on completion of either illumination protocol. In contrast, xanthosomes attain a high degree of aggregation during white background adaptation under continuous illumination, but do not display slow "summation" of pigment aggregation in response to the diurnal light photoperiods. The differences between melanosome and xanthosome aggregation under these photoperiod regimes are discussed in relation to the previously established types of balance between neural and humoral systems controlling flounder melanophores and xanthophores.

The Black Scuare – from Alle to Malevich

2019 ◽  
Vol 3 (1) ◽  
Author(s):  
Alexander Gyoshev ◽  
Keyword(s):  
Contemporary Art ◽  
Cultural Context ◽  
White Background ◽  
Abstract Painting ◽  
Central Concern ◽  
French Writer ◽  
Adequate Understanding ◽  
Iconic Image ◽  
Dark Figure

The study observes some of the most important details hidden in Kazimir Malevich’s abstract painting “Black Square on a White Background” (1915). Of central concern for the more adequate understanding of this intriguing piece of art is the tracking of its supposed relationship with the work of Alfons Alle – French writer known for his extravagant style and ideas. The differences between Alle’s painting entitled “Negroes Fighting in a Cellar at Night” and Malevich’s composition, both sharing similar themes, are analyzed in their specific historical and cultural context. Finally, there is a hypothesis about “Black Square on a White Background” as a work marked with a psychological projection that unfolds itself through the dark figure of the square, as an iconic image that still has an impact on the contemporary art and may serve as a key to some symbols of the present.

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