Kako bi nadgledao okolinu i kretao se u stvarnom svijetu, robot bi trebao biti u mogućnosti da dobije slike i mjerenja okoliša u različitim uvjetima pozadinskog osvjetljenja. Posljednjih godina, istraživači i inženjeri širom svijeta rade na razvoju sve naprednijih senzora za integraciju u robote, sisteme za nadzor ili druge uređaje koji mogu osjetiti njihovu okolinu.
Prema Memes Consultingu, istraživači sa Politehničkog univerziteta u Hong Kongu, Univerziteta u Pekingu, Univerziteta Yonsei i Univerziteta Fudan nedavno su razvili novi tip bioničkog senzora vida koji koristi mehanizam koji umjetno simulira funkciju mrežnice i može se koristiti u različitim podacima. pod svetlosnim uslovima. Ovaj bionički senzor za vid baziran je na fototranzistorima napravljenim od molibden disulfida.
Fotografija niza biomimetičkih senzora vida (lijevo); shematska struktura jedinice senzora vida i slika optičkog mikroskopa (desno)
"Our research team started work on optoelectronic memory five years ago," said Yang Chai, one of the researchers who developed the vision sensor. "This emerging device can output light-dependent and history-dependent signals, enabling image integration. , Weak signal accumulation, spectral analysis and other complex image processing functions, the multi-functional integration of sensing, data storage and data processing into one device."
Godine 2018, Yang Chai i njegove kolege objavili su prvi rad o optoelektronskoj memoriji, u kojem su predstavili rezistivni prekidački memorijski uređaj koji može obavljati senzorske i logičke operacije. Godinu dana kasnije, tim je predstavio novi tip fotootporne memorije sa slučajnim pristupom sa tri različite funkcije. Konkretno, novi uređaj može osjetiti okolinu, pohraniti informacije u memoriju i izvoditi neuromorfne operacije vizualne preprocesiranja.
"We studied the concepts of near-sensor and in-sensor computing paradigms in 2020 and published our views in the field." Yang Chai continued, "This new research on biomimetic vision sensors builds on our On top of all previous efforts."
The intensity of ambient natural light varies widely, with a total range of 280 dB. When the human retina senses external light signals, it adjusts the light sensitivity of its photoreceptors (i.e., rods and cones) according to the strength of the signal. This ultimately enables the human eye to gradually adapt to varying levels of lighting, allowing it to see clearly in both dark and bright environments, an ability known as "visual adaptation."
"For example, when you enter a dark cinema from a bright hall, you can hardly see anything at first, but after a while in the cinema, it becomes easier to see things," explains Yang Chai. "This phenomenon is called scotopic adaptation. Conversely, if you go from a dark movie theater to a sunny outdoors, you'll feel very dazzled at first, and it takes a while to get used to seeing what's going on around you. The process The opposite of dark adaptation is called photopic adaptation."
The main goal of Yang Chai and his colleagues' recent work is to build a vision sensor inspired by the structure and function of the human retina. To do this, they first started by studying the human retina and then tried to design perceptual strategies that would allow them to artificially simulate visual adaptations.
Najsavremeniji--- senzori slike zasnovani na CMOS tehnologiji obično imaju ograničen dinamički opseg od 70 dB. Međutim, ovaj dinamički raspon je mnogo uži od raspona osvjetljenja prirodnih scena (280 dB).
"To achieve visual perception over a wide range of light intensities, researchers have explored the use of controlled optical apertures, liquid lenses, adjustable exposure times, and denoising algorithms in post-processing," said Yang Chai. "However, these Methods often require complex hardware and software resources."
Dark and light adaptation of biomimetic vision sensor arrays. (a) Schematic of the dark adaptation test: recognition of low-light images using an 8 x 8 pixel array in a dark environment. (b) Schematic diagram of light adaptation test: recognition of high-illuminance images using an 8 x 8 pixel array in a bright environment. (c) Dark adaptation process to identify the "8" pattern. (d) The photoadaptation process to identify the "8" pattern.
Optoelektronski uređaji sa vidom-prilagodljivim na svjetlost i širokim opsegom osjetila na senzornim terminalima mogli bi imati vrlo vrijedne primjene. Na primjer, oni mogu pomoći u poboljšanju performansi alata za kompjuterski vid, smanjenju složenosti hardvera koji je potreban za izgradnju robota ili drugih senzorskih sistema i poboljšanju tačnosti sistema za prepoznavanje slika.
Iako su drugi istraživački timovi u prošlosti razvili optoelektronske uređaje koji se mogu prilagoditi različitim svjetlosnim uvjetima. Međutim, većina prethodno demonstriranih uređaja može samo oponašati mehanizam adaptacije na svjetlost mrežnice. Do sada se pokazalo da je proces adaptacije na mrak teže simulirati.
"There is still a long way to go to fully replicate the visual adaptation function of the retina," explains Yang Chai. "To achieve this, we designed a phototransistor-based vision sensor using ultra-thin semiconductors that can The degree of dark adaptation and light adaptation in the same device was controlled by applying different gate voltages. In this way, we simulated photoreceptors and horizontal cells in the retina and successfully achieved a sensing range of 199 dB. Vision-adaptive devices in biomimetic sensors."
Umjetna simulacija fotoreceptora i horizontalnih stanica u retini za vizualnu adaptaciju (adaptacija na tamu i adaptaciju na svjetlo)
Biomimetički senzor vida koji su razvili Yang Chai i kolege baziran je na fototranzistorima napravljenim od ultratankog poluprovodničkog materijala poznatog kao molibden disulfid. Fototranzistori koje su koristili imaju višestruka stanja zamke naboja koja mogu uhvatiti ili osloboditi elektrone unutar kanala pri različitim naponima gejta.
Ultimately, these states allow researchers to dynamically tune the conductance of their devices. This, in turn, allowed them to artificially simulate the dark- and light-adaptive mechanisms of the human retina, thereby expanding the range of their sensor's perception of different lighting conditions.
"Our bionic vision sensor has several advantages and features," said Yang Chai. "First, the visual adaptation function is implemented in a single device, which greatly reduces the footprint. Second, multiple functions can be implemented on a single device. , including light sensing, memory, and processing. Finally, dark and light adaptation under different light intensities can be achieved by controlling its gate voltage."
Yang Chai i njegove kolege procijenili su bionički senzor vida u nizu testova i otkrili da on može djelotvorno oponašati funkciju ljudske mrežnice, postižući izvanredne rezultate u adaptaciji na tamu i svjetlost. Nadalje, ima znatno veći perceptivni opseg (199 dB) u odnosu na ranije predložena rješenja.
"Our vision sensor can enrich machine vision functions, reduce hardware complexity, and achieve high image recognition efficiency," said Yang Chai, "All these advantages are available in areas such as autonomous driving, face recognition, and industrial manufacturing in complex lighting environments. great application prospects."
U budućim studijama, istraživači planiraju dodatno poboljšati performanse senzora vida, koristeći ga i za proizvodnju velikih-sistema koji se sastoje od nizova senzora. U idealnom slučaju, oni žele da izgrade ovaj niz senzora na fleksibilnoj ili hemisferičnoj podlozi kako bi omogućili šire vidno polje.
"One area that needs improvement is the adaptation time of our vision sensor, as it is still not enough to support machine vision applications." Yang Chai added, "Our goal is to reduce the adaptation time to the microsecond level. In addition, the vision sensor array scale Further improvements are also needed. Our near-term target for array size is greater than 100 x 100 pixels. Finally, the heterogeneous integration of vision sensors and post-processing units, including silicon-based control circuits, is a very important step toward practical applications."
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