On Friday, I took images for different power outputs of LED. I calculated the calibration factor as explained in my previous elog (plots attached).
| Vcc (V) |
Photodiode
reading(V) |
Power incident on photodiode (W)
|
Power incident on GigE (W) |
|
Uncertainity in
slope (counts/𝝁s) |
CF (W-sec/counts) |
| 16 |
0.784 |
2.31E-06 |
3.89E-07 |
180.4029 |
1.02882 |
2.16E-15 |
| 18 |
0.854 |
2.51E-06 |
4.24E-07 |
207.7314 |
0.7656 |
2.04E-15 |
| 20 |
0.92 |
2.71E-06 |
4.57E-07 |
209.8902 |
1.358 |
2.18E-15 |
| 22 |
0.969 |
2.85E-06 |
4.81E-07 |
222.3862 |
1.456 |
2.16E-15 |
| 25 |
1.026 |
3.02E-06 |
5.09E-07 |
235.2349 |
1.53118 |
2.17E-15 |
| |
Average |
2.14E-15 |
To estimate the uncertainity, I assumed an error of at most 20mV (due to stray lights or difference in orientation of GigE and photodiode) for the photodiode reading. Using the uncertainity in slope from the linear fit, I expect an uncertainity of maximum 4%. Note: I haven't accounted for the error in the responsivity value of the photodiode.
| GigE area |
10.36 sq.mm |
| PDA area |
61.364 sq.mm |
| Responsivity |
0.34 A/W |
| Transimpedance gain (at gain = 20dB) |
10^6 V/W +/- 0.1% |
| Pixel format used |
Mono 8 bit |
Johannes had reported CF as 0.0858E-15 W-sec/counts for 12 bit images, with measured a laser source. This value and the one I got are off by a factor of 25. Difference in the pixel formats and effect of coherence of the light used might be the possible reasons. |