A Dual NIR-Band Lock-In Pixel CMOS Image Sensor With Device Optimizations for Remote Physiological Monitoring

Cao, Changqing; Dutta, Jaydeep; Hakamata, Masashi; Yasutomi, Keita; Kagawa, Keiichiro; Aoyama, Satoshi; Tsumura, Norimichi; Kawahito, Shoji

doi:10.1109/ted.2021.3057035

Cited by 6 publications

(6 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, we suggest that our 8-tap SFDI system can overcome this limitation by employing a low duty ratio short pulse light source, which emits high-power light in a narrow pulse width (e.g., pulse with: a few μs) periodically, whereas it turns off after each illumination and remains off for most of the time, as demonstrated in Ref. 22. In future work, we will focus on investigating the implementation of low duty ratio short pulse light sources and extending the drain time to meet with the sensor’s specification.…”

Section: Discussionmentioning

confidence: 99%

“…This degradation can be attributed to the design and operation of the sensor, as described in Ref. 22 . The sensor in our system is specifically designed to detect short pulse light within consecutive time windows of 500 ns.…”

Section: Discussionmentioning

confidence: 99%

“…1(c). The layout of the subpixel cell is similar to the reported 2-tap pixel 22 . Thus, it can be defined as a “virtual” 8-tap pixel.…”

Section: Methodsmentioning

confidence: 99%

“…The layout of the subpixel cell is similar to the reported 2-tap pixel. 22 Thus, it can be defined as a “virtual” 8-tap pixel. The pixel design complexity is significantly reduced compared with the original 8-tap sensor.…”

Section: Methodsmentioning

confidence: 99%

See 3 more Smart Citations

Motion-resistant three-wavelength spatial frequency domain imaging system with ambient light suppression using an 8-tap CMOS image sensor

Feng,

Cao,

Shimada

et al. 2024

J. Biomed. Opt.

Self Cite

View full text Add to dashboard Cite

We present a motion-resistant three-wavelength spatial frequency domain imaging (SFDI) system with ambient light suppression using an 8-tap complementary metal-oxide semiconductor (CMOS) image sensor (CIS) developed at Shizuoka University. The system addresses limitations in conventional SFDI systems, enabling reliable measurements in challenging imaging scenarios that are closer to real-world conditions.Aim: Our study demonstrates a three-wavelength SFDI system based on an 8-tap CIS. We demonstrate and evaluate the system's capability of mitigating motion artifacts and ambient light bias through tissue phantom reflectance experiments and in vivo volar forearm experiments.Approach: We incorporated the Hilbert transform to reduce the required number of projected patterns per wavelength from three to two per spatial frequency. The 8-tap image sensor has eight charge storage diodes per pixel; therefore, simultaneous image acquisition of eight images based on multi-exposure is possible. Taking advantage of this feature, the sensor simultaneously acquires images for planar illumination, sinusoidal pattern projection at three wavelengths, and ambient light. The ambient light bias is eliminated by subtracting the ambient light image from the others. Motion artifacts are suppressed by reducing the exposure and projection time for each pattern while maintaining sufficient signal levels by repeating the exposure. The system is compared to a conventional SFDI system in tissue phantom experiments and then in vivo measurements of human volar forearms. Results:The 8-tap image sensor-based SFDI system achieved an acquisition rate of 9.4 frame sets per second, with three repeated exposures during each accumulation period. The diffuse reflectance maps of three different tissue phantoms using the conventional SFDI system and the 8-tap image sensor-based SFDI system showed good agreement except for high scattering phantoms. For the in vivo volar forearm measurements, our system successfully measured total hemoglobin concentration, tissue oxygen saturation, and reduced scattering coefficient maps of the subject during motion (16.5 cm/s) and under ambient light (28.9 lx), exhibiting fewer motion artifacts compared with the conventional SFDI.Conclusions: We demonstrated the potential for motion-resistant three-wavelength SFDI system with ambient light suppression using an 8-tap CIS.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

“…1(c). The layout of the subpixel cell is similar to the reported 2-tap pixel 22 . Thus, it can be defined as a “virtual” 8-tap pixel.…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Motion-resistant three-wavelength spatial frequency domain imaging system with ambient light suppression using an 8-tap CMOS image sensor

Feng,

Cao,

Shimada

et al. 2024

J. Biomed. Opt.

Self Cite

View full text Add to dashboard Cite

show abstract

“…For low-noise readout, the demodulator structure shown in Fig. 2(b) and the pixel circuits can be modified for having intermediate storages and true-CDS type of readouts [32].…”

Section: A Principle Of Htof Pixelsmentioning

confidence: 99%

Hybrid Time-of-Flight Image Sensors for Middle-Range Outdoor Applications

Kawahito

Yasutomi

Mars

2022

IEEE Open J. Solid-State Circuits Soc.

Self Cite

View full text Add to dashboard Cite

This paper introduces a new series of time-of-flight (TOF) range image sensors that can be used for outdoor middlerange (10m to 100m) applications by employing a small duty-cycle modulated light pulse with a relatively high optical peak power. This set of TOF sensors is referred to here as a hybrid TOF (hTOF) image sensor. The hTOF image sensor is based on the indirect TOF measurement principle but simultaneously uses the direct TOF concept for coarse measurements. Compared to conventional indirect TOF image sensors for outdoor middlerange applications, the hTOF image sensor has a distinct advantage due to the reduction of capturing ambient light charge. To show the potential of the hTOF image sensor for outdoor middle-range operation, a model of estimating distance precision of hTOF image sensors is built and applied it by using possible sensor specifications to estimate the distance precision of the hTOF range camera in 10m, 20m and 40m measurements under the ambient-light condition of 100klux and its feasibility is discussed. In outdoor 10m-range measurements, the advantage of hTOF image sensors compared to the conventional indirect TOF image sensors is discussed by considering the amount of captured ambient-light charge in pixels.

show abstract