Advanced Technical Specs of Persee and Astra Sensors

Technical Support & Q&A Advanced
1

Hello, we find the Persee and Astra Cameras look extremely promising!

We have got some questions however about technical specifications that we haven’t found anywhere on the web sites but which would be very good to know. These would really help us evaluate the sensor.

  • Accuracy at different ranges:
    The tech specs quote accuracy of up to 5mm at a 2m range. Can you provide a graph showing the accuracy of the sensor at different ranges (i.e. 1m, 2m, 3m, …, 8m)?
    Also we’d like to confirm whether the quoted values are indeed accuracy and not precision values (common pitfall with other sensor manufacturers).

  • Calibration: Do the Persee and Astra-Sensors come pre-calibrated? Is there an API to query focal lengths, optical centers and lens distortion parameters from the sensor?

  • Measurement Stability (environmental factors): How does temperature and other environmental factors (humidity, etc…) affect the measurement accuracy? Does the sensor perform any form of temperature distortion compensation?

  • Measurement Stability (other): Will the measurements be stable over time (i.e. does the sensor accuracy degrade over time)? Does the sensor need a “warmup period” to deliver maximum accuracy?

  • Surfaces: Any surfaces that can’t be captured (I assume reflective surfaces would be a problem)? Can black surfaces be captured?

  • Can the sensor withstand mild shocks and bumps without losing accuracy?

  • Are the color and depth images registered (i.e. a pixel position in color and depth corresponds to the same physical point) and synchronized (i.e. depth and color have been taken at the same point in time) on the sensor?

  • Daylight capabilities: How sensitive are the Astra and Persee sensors to daylight? Can I capture outdoors when the sun is not shining (dawn/dusk, cloudy)?

  • Working principle: Are the Astra / Persee cameras based on Structured Light or “Assisted Stereo” working principles?

  • Weight: How much do the Astra and Persee Cameras weigh?

  • Eye safety: Are the sensors eye safe (I assume yes but just double-checking)? Which Laser class?

  • Is there any taxation of the host processor during frame capture (i.e. for frame decoding, conversion, etc…)?

  • What are the power requirements for the Persee and Astra sensors? Can the Persee or Astra sensor be powered over USB? If not, are there battery options?

  • Can a Persee or Astra sensor be connected to a mobile device through a USB OTG adapter?

  • Will Persee and Astra sensors have fill OpenNI2 support (i.e. we can use the sensor wherever we can get OpenNI2 to run)?

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2

Good questions @Rafael! I like to add:

  • Interaction: What’s the expect change in performance if multiple cameras (Astras) view the same scene? That is, what happens if FOVs of multiple projectors overlap?
3

Did you ever get answers to these questions, @Rafael? I’d especially like to know about accuracy at different ranges and daylight capabilities. I’d also like to add:

  • Embedded support: Is the SDK available on Linux for ARM processors? If not, will it be available in the future?
4

Yes, David from Orbbec got back to me via email.

@David: Would it be ok if I post your answers into this thread?

Rafael

5

Sorry for the late reply @Rafael,

I am not in charge of posting on the forum. I think some one within our team will post the answer in an official form very soon. Probably @Gordon

But please feel free to share my answers with your friends and @mono . If you need any answer, please feel fee free to shoot us an email: info@orbbec3d.com

Best wishes,

6

Hello,
can anyone post the answers to the interesting questions?
Thx

7

Ya Please post the answers here. I too would like to know the same.

Thanks,
Sasank

8

Hello guys, add me on Linkin and see my latest post, you will get all answer. Linkedin Profile: Orbbec 3D David Chen

9

Hi all,

with David’s permission here are the answers that I received:

==============

Accuracy
Currently, we get 3rd party measurement result showing that the accuracy at about 1m is +/-1-3mm; The accuracy at about 3m is +/-12.7mm.
We don’t have other 3rd party evaluation data on 4, 5, 6, 7 and 8m. As a developer, I would say our optimized maximum range is about 6m. No, they are not precision values. Measurements have performed by comparing the measured data to reference objects with known shape.

Calibration:
Do the Persee and Astra-Sensors come pre-calibrated? Is there an API to
query focal lengths, optical centers and lens distortion
parameters from the sensor?

Yes, they are pre-calibrated. We have focal lengths value. But don’t not have the intrinsics (distortion/physical optical center) parameter of individual CMOS sensor.

Measurement Stability (environmental factors):
How does temperature and other environmental factors (humidity, etc…) affect the measurement accuracy? Does the sensor perform any form of temperature distortion compensation?

Yes, we have temp. distortion compensation. The sensor should be OK with 50 degrees C without any extra cooling. Regarding the humidity. Our sensor passed the test 80% humidity, but I would suggest you to use it under room humidity around 60% maximum.

Measurement Stability (other):
Will the measurements be stable over time (i.e. does the sensor accuracy degrade over time)? Does the sensor need a “warmup period” to deliver maximum accuracy?

Our sensors do pass aging/durability tests in the lab. As a researcher, I would say degrade will happen eventually. But as a consumer level product, our sensor should be a great choice. Yes, it does have a warm up period for several seconds. Shorter than the PrimeSense ones.

Surfaces:
Any surfaces that can’t be captured (I assume reflective surfaces would be a problem)? Can black surfaces be captured?

They don’t work on transparent, high reflective and absorptive surfaces. It has much better performance on dark surfaces than Realsense. The following file should give you some general idea.

In addition, we allow you to adjust the gain of the IR camera to make the data better on dark surfaces.

Can the sensor withstand mild shocks and bumps without losing accuracy?
Vibration, falling tests are included in our QC procedure. Should be able to send you a brief report shortly.

Are the color and depth images registered (i.e. a pixel position in color and depth corresponds to the same physical point) and synchronized (i.e. depth and color have been taken at the same point in time) on the sensor?

Yes, they are registered. But we don’t support hardware sync. When running at 30 FPS, the desynchronization effect appears to be subtle.

Daylight capabilities:
How sensitive are the Astra and Persee sensors to daylight? Can I capture outdoors when the sun is not shining (dawn/dusk, cloudy)?

They don’t work under direct sunlight. But for dawn/dusk/cloudy, they work fine.

Working principle:
Are the Astra / Persee cameras based on Structured Light or “Assisted Stereo” working principles?

Structure light.

Weight:
How much do the Astra and Persee Cameras weigh?

Astra = 0.7lb; Persee…forget the value, will post it online shortly.

Eye safety:
Are the sensors eye safe (I assume yes but just double-checking)? Which Laser class?

Class 1 certified.

Is there any taxation of the host processor during frame capture (i.e. for frame decoding, conversion, etc…)

No. But you can choose to apply some low resource cost filtering/smoothing in the driver level.

What are the power requirements for the Persee and Astra sensors? Can the Persee or Astra sensor be powered over USB? If not, are there battery options?

Astra only need USB 2.0 as power. Persee is using 5V3A DC (Adapter included). We are planning to release battery package for Persee, but I don’t have a date yet.

Can a Persee or Astra sensor be connected to a mobile device through a USB OTG adapter?

Yes. Persee has a micro USB 2.0 with OTG enabled on it. Astra doesn’t have embedded processor and can be connected to any mobile device using USB 2.0.

Will Persee and Astra sensors have fill OpenNI2 support (i.e. we can use the sensor wherever we can get OpenNI2 to run)?

Astra will have full OpenNI 2 support. Since Persee is using an UVC RGB camera, you can only access depth through OpenNI 2.

Since there is a computer built in, is it coming with an OS? Will it run Android or Linux?

Yes, Persee comes with Ubuntu 14 and Android 4.4. Dual system, one click switch. Persee has 16GB embedded eMMC for the OS thus you don’t need to buy one.

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10

Has anyone found out how to retrieve this value via the API?

11

This works for me:

std::unique_ptrastra::StreamSet m_sensor = std::unique_ptrastra::StreamSet(new astra::StreamSet(astra::StreamSet(“device/default”)));
std::unique_ptrastra::StreamReader m_reader = std::unique_ptrastra::StreamReader(new astra::StreamReader(m_sensor->create_reader()));
float m_depth_hFOV = m_reader->streamastra::DepthStream().horizontalFieldOfView();
float m_depth_vFOV = m_reader->streamastra::DepthStream().verticalFieldOfView();

Note that the field of views seem to be in radians, not degrees.

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