Journal: Neurophotonics

Article Title: MiniFAST: a sensitive and fast miniaturized microscope for in vivo neural recording

doi: 10.1117/1.NPh.13.S2.S23203

Figure Lengend Snippet: MiniFAST system overview. (a) Illustration of the MiniFAST miniaturized microscope imaging module. (b) Diagram of the MiniFAST system. (c) Comparison of miniaturized microscope image sensor resolution versus published frame rates. , , , , – , Numbers in parentheses indicate the sensor pixel size. *Note: CHEndoscope image sensor is 5 MP, but images are binned to 648 × 486 to achieve a 20-Hz frame rate. (d) Images from V3.2 Miniscope (left) and MiniFAST (right) of a USAF 1951 high-resolution test target cropped to show groups 7 through 9. V3.2 Miniscope settings are 10 Hz, 0-dB gain, and 0.18-mW excitation light. MiniFAST settings are 8-Hz, 0-dB gain, and 0.1-mW excitation light. The same set of microscope housing, filters, and optical lenses were used on both microscopes. Inset shown is of the line profile through group 9 elements. (e) PTC (mean signal versus variance) acquired at full 12-bit resolution using an IDS IMX290 evaluation board (U3-3862SE Rev. 1.2). The conversion gain was extracted from the slope of the linear, shot-noise-dominated regime. Measurements were performed at a frame rate of 6 fps using exposure times of 0.02, 0.1, 1, 9, 18, 27, 45, 54, 63, and 72 ms, with an analog gain setting of 22.8 dB and digital gain of 0 dB. The extracted conversion gain was 0.168 e − /ADU (5.95 ADU/ e − ). (f) Per-pixel conversion gain histogram given in ADU/e − for the same operating mode shown in panel (e). Vertical lines indicate the mean and standard deviation of the distribution. (g) Photograph of the IDS IMX290 evaluation board mounted at the output port of the integrating sphere used for the PTC measurements. (h) Photon transfer curves (mean signal versus variance) for the Sony IMX290 sensor measured using the IDS IMX290 evaluation board and the MiniFAST implementation operated in an 8-bit output mode, shown for multiple analog gain settings (up to 30 dB) with no digital gain. Extracted conversion gains for the IDS PTCs were 0 dB: 2.4 e − /ADU, 13.3 dB: 0.52 e − /ADU, 19.3 dB: 0.26 e − /ADU, and 22 dB: 0.17 e − /ADU. For the MiniFAST measurements, changes in illumination level were achieved by varying the frame rate between 60 and 500 fps. (i) SNR as a function of mean signal (ADU) for the gain settings shown in panel (h).

Article Snippet: To compare the imaging performance of the V3.2 Miniscope and MiniFAST, we imaged a USAF 1951 high-resolution test target (Edmund Optics #55622, Barrington, New Jersey, United States) [ ] using the same set of optics, similar frame rates, and gain settings.

Techniques: Microscopy, Imaging, Comparison, Standard Deviation