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Assumptions
The Image Aquisition System will be a payload on the BenchBot, and can rely on the BenchBot meeting its stated requirements.
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Our current Godox AR400 ring flash has an output of approximately 8500 lumenseconds with an unknown flash duration. However, assuming that the same numbers apply, we have: 1,270,000 lux, or 13 times the maximum sunlight intensity for a short interval. If limited to a shutter speed of 1/200 due to a rolling shutter sensor, that number is down to 1,700,000 lumen and 170,000 lux, or 1.7 times the sun intensity.
As Chris has pointed out in the comments, the above revolve around the need for an artificial dominant light source. Another consideration is that of depth of field. The current system, when running the AR400 at full power, allows for an aperture at F11, with ISO=100 and shutter speed=1/200 sec. If, for the sake of increased depth of field, we would like to increase the F-number from F11 to F16, that will increase the flash output requirements by a factor of 2, given that we remain at base ISO.
Another way to increase the applied light onto the plants is by changing the flash distance. As it is setup today, the flash is 1.65 meters above the potting area to provide a close to even illumination of the plants within the allowable plant heights. As a flash distance is decreased, more light will be applied to the potted plants, but the light distribution from the top of the plant to lower parts will worsen. Another way to increase the applied light, while maintaining the light distribution, is by focusing the emitted light from the flash either using a reflector or a different light source.
Requirements Table
Id | Requirement name | Description | Category | Allowable Limits | Status | Justification |
|---|---|---|---|---|---|---|
A.1 | Automation | Shall minimize day to day adjustments during data acquisition and postprocessing. | Automation | |||
A.2 | Color checker | Shall tag the color checker image | Automation | |||
D.1 | Plant size | Shall reliably support plant sizes with a planar radius of 30 cm at soil level, centered at each pot. | Data | |||
D.2 | Could support multiple sensors simultaneously | Data | ||||
D.3 | Images shall overlap | Data | 65% | |||
D.4 | File type | Shall output RAW and JPG files | Data | |||
D.5 | File architecture | Shall create a folder per data collection day and save files in such folder | Data | |||
D.6 | Plant size | Shall support plant sizes with a height ranging from 0 cm to 40 cm above the pot soil | Data | |||
G.1 | Internet connection | Good to have | ||||
IQ.1 | Flash (Roller shutter) Intensity | Image Quality | Minimum 200,000 lux | |||
IQ.2 | Flash (Roller shutter) Duration | Image Quality | Minimum of 1/200 sec | |||
IQ.3 | Flash (Global shutter) Intensity | Image Quality | Minimum 1.2M lux | |||
IQ.4 | Flash (Global shutter) Duration | Image Quality | Minimum 1/5000 sec | |||
IQ.5 | Auto focus | Camera shall have auto focus | Image Quality | TRUE/FALSE | ||
IQ.6 | Automatic manual focus | If auto focus FALSE then this one is needed | Image Quality | z positional accuracy of 3 cm | ||
IQ.7 | ISO | The camera shall be configured to avoid analog amplification of pixel values to avoid ISO noise. | Image Quality | ISO=BASE (100 for Sony full frame sensors) Analog amplification of 0dB on pixel readings on non-consumer cameras | Image noise must be kept to a minimum by using the camera’s base ISO while still have an acceptable exposure histogram | |
IQ.8 | Relative Image Resolution | The camera should provide a minimum soil-level Ground Sample Distance (GSD) | Image Quality | 7-9 pixels per mm (emergence) | ||
IQ.9 | Depth of field | Image Quality | Minimum 15 cm | |||
IQ.10 | Color temperature | The color temperature shall be consistent | Image Quality | +/- 200K | ||
IQ.11 | Color rendering index | Image Quality | 90 or greater | |||
M.1 | Species ID | Shall provide species ID for each pot in X, Y position | Metadata | |||
M.2 | Weather info | Shall have accurate local weather data information for each run | Metadata | Captured from on site weather station | ||
M.3 | Light information | Shall provide incident light information per image | Metadata | Sensor positioned near camera | ||
M.4 | Camera position | Shall provide absolute and relative camera position and orientation | Metadata | +/- 1 cm +/- 1o | ||
M.5 | Image metadata | Shall provide ISO and Shutter Speed | Metadata | |||
Shall allow the user to change camera settings | Not a general requirement | |||||
ST.1 | Image throughput | Shall be able to capture images of 500 pots in less than 4 hours (500 images) | Speed and Throughput | |||
ST.2 | Data transfer speed | Shall be such that does not jeopardize the minimum required image throughput. | Speed and Throughput | |||
UI.1 | Visual feedback | Should provide visual feedback to the user for manual inspection of errors during data collection | User Interaction | |||
UI.2 | Shall allow the user to enter metadata | User Interaction | ||||
UI.3 | Shall allow the user to share data | User Interaction | ||||
UI.4 | Shall allow the user to trigger camera independently | User Interaction |
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