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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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With a set of base assumptions, the produced depth of field is 16.9 cm, corresponding to a far and near limit at 1.74 m and 1.57 m respectively, assuming that the focus is set for a distance of 1.65 m. This is based on a pixel size of 3.76um 76 um in a full frame sensor setup at 61 megapixel, a 55mm lens, an aperture of F13 and a distance from the camera to the plant of 1.65 meter. As the aperture is physically decreased, the depth of field in increase, at the cost of decreased optical resolution due to diffraction. F13, is what I, Søren, would characterize as the sweet-spot between depth of field and a negligible loss of optical resolution due to diffraction. Sources for depth of field and diffraction calculations. With this in mind, if the lens is not auto-focusing, the camera should to be controlled in the z-axis with a resolution of 3-5 cm.
Flash consideration to keep in mind
The flash should be dominant relative to natural sunlight. As sunlight can reach an intensity of 98.000 lux, the flash should ideally fire with at least twice the intensity.
The alienbees ABR800 has an output of 14000 lumenseconds with a flash duration (t.5) of 1/2000, meaning that 3/4 of the light has been fired after 1/2000 seconds. Based on this, the ABR800 has a light output of 21,000,000 lumen. Assuming a light spread of 10 m2, that results in 2,100,000 lux, or 21 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 2,800,000 lumen and 280,000 lux, or three times the sun intensity.
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 280,000 lux, or three times the sun intensity.
Image Quality Requirements
Id | Requirement name | Description | Category | Allowable Limits | Status | Solution | |||||||||||||
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Internet connection | Good to have | ||||||||||||||||||
1.1 | Image quality | Image noise must be kept to a minimum by using to the camera’s base ISO while still have an acceptable exposure histogram | Image Quality | ISO=BASE (100 for Sony full frame sensors) | |||||||||||||||
1.2 | Relative Image Resolution | Should The camera should provide a soil-level Ground Sample Distance (GSD) of minimum 8 pixels per mm. | Image Quality | 7-9 pixels per mm (emergence)Minimum resolution | |||||||||||||||
1.3 | MP | Image Quality | |||||||||||||||||
1.4 | Sensor size | Full frame | Image Quality | ||||||||||||||||
1.6 | Sensor type | CMOS | Image Quality | ||||||||||||||||
1.7 | Pixel size | Image QualityCircle of confusion | |||||||||||||||||
1.8 | File type | Shall output RAW and JPG files | Image Quality | IQ 3.1 | File architecture | Shall create a folder per data collection day and save files in such folder | |||||||||||||
IQ.2.0 | Plant size | Shall support plant sizes with a height ranging from 0 cm to 40 cm above the pot soil | IQ.2.1 | Plant size | Shall reliably support plant sizes with a planar radius of 30 cm at soil level, centered at each pot. | IQ.3.0 | Automation | Shall minimize day to day adjustments. These include aperture control during image collection, and preprocessing and white balancing in post | IQ.4.0 | Visual feedback | Should provide visual feedback to the user for manual inspection of errors during data collection | User Interaction | Auto focusSpecies ID | Shall provide species ID for each pot in X, Y position | Metadata | ||||
Weather info | Shall have accurate local weather data information for each run | Metadata | Captured from on site weather station | ||||||||||||||||
Light information | Shall provide incident light information per image | Metadata | Sensor positioned near camera | ||||||||||||||||
Camera position | Shall provide camera position and orientation | Metadata | +/- 1 cm +/- 1o | ||||||||||||||||
Image throughput | Shall be able to capture images of 500 pots in less than 4 hours (500 images) | Speed and Throughput | |||||||||||||||||
Data transfer speed | Shall be such that does not jeopardize the minimum required image throughput. | Speed and Throughput | Species ID | Shall provide species ID for each pot in X, Y position | Metadata | Weather info | Shall have accurate local weather data information for each run | Metadata | Captured from on site weather station | Light information | Shall provide incident light information per image | Metadata | Sensor positioned near camera | ||||||
IQ.4.0 | Visual feedback | Should provide visual feedback to the user for manual inspection of errors during data collection | User Interaction | ||||||||||||||||
Shall allow the user to enter metadata | User Interaction | ||||||||||||||||||
Shall allow the user to share data | User Interaction | ||||||||||||||||||
Shall allow the user to control User Interaction | User Interaction | ||||||||||||||||||
Shall allow the user to change camera settings | User Interaction | ||||||||||||||||||
Shall allow the user to trigger camera independently | User Interaction | Camera position | Shall provide camera position and orientation | Metadata | +/- 1 cm +/- 1o | Internet connection | Good to have | Images shall overlap | |||||||||||
1.3 | Flash | The flash should be dominant relative to natural sunlight. As sunlight can reach an intensity of 98.000 lux, the flash should ideally fire with twice the intensity. | |||||||||||||||||
Circle of confusion | |||||||||||||||||||
IQ 3.1 | File architecture | Shall create a folder per data collection day and save files in such folder | Data | ||||||||||||||||
IQ.2.0 | Plant size | Shall support plant sizes with a height ranging from 0 cm to 40 cm above the pot soil | Data | ||||||||||||||||
IQ.2.1 | Plant size | Shall reliably support plant sizes with a planar radius of 30 cm at soil level, centered at each pot. | Data | ||||||||||||||||
IQ.3.0 | Automation | Shall minimize day to day adjustments. These include aperture control during image collection, and preprocessing and white balancing in post | Automation | ||||||||||||||||
Auto focus | |||||||||||||||||||
Images shall overlap | Data | 65% |
Emergent design properties
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