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IntelRealSense / librealsense

Intel® RealSense™ SDK
https://www.intelrealsense.com/
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Is there any Information about Fixed focus range of RGB sensor? #9123

Closed suho0515 closed 3 years ago

suho0515 commented 3 years ago
Required Info
Camera Model { D400 }
Firmware Version 05.12.12.100
Operating System & Version {Win 10
Platform PC
SDK Version { legacy / 2.<?>.<?> }
Language {C/C#/labview/nodejs/opencv/pcl/python/unity }
Segment {Robot }

Issue Description

<Describe your issue / question / feature request / etc..>

Hello sir, I'm using Realsense D435i for Robotics application.

I'll use it to get variety of information in indoor environment.

and sometimes, I should do very delicate task too, like OCR.

for this purpose, I thought that I need to find out the focus range of RGB sensor, but in every datasheet, it only says It is "Fixed Focus" but what range would be great to observe objects.

so my question is " is there any information about fixed focus range of rgb sensor?"

and I tried to calculate appropriate working distance of rgb sensor.

like this

focal length x FOV / sensor size = Working Distance

refferd from https://www.ni.com/ko-kr/support/documentation/supplemental/18/calculating-camera-sensor-resolution-and-lens-focal-length.html

is it right approch?

I hope to hear your anser soon.

regards.

agrunnet commented 3 years ago

Actually it is more about what the hyper focal distance is. I don’t have the exact number in front of me but the image is in focus from roughly 30cm to infinity.

MartyG-RealSense commented 3 years ago

Thanks very much @agrunnet for your advice!

@suho0515 Do you require further assistance with your question, please? Thanks!

suho0515 commented 3 years ago

Thank you @agrunnet :). I wanted more detail, but I guess there is no way to figure it out.

so, I'll close this issue.

Thanks, @MartyG-RealSense too.

MartyG-RealSense commented 3 years ago

You are very welcome @suho0515 - thanks for the update!

agrunnet commented 3 years ago

@suho0515 I will give you more details. The way to calculate the hyper focal distance of an imaging system is H= focal length focal length / (circle of confusion F-number)

The circle of confusion is how many pixels of blur you can tolerate. Let's set it to 2 pixels. Since each pixel is 1.4um, this means 0.0028mm.

For D435 the color imager has focal length of 1.91mm. Finally the F# is also a lens spec. It is 2.

With this the hyperfocal distance is 65cm.

However, the definition of hyper focal distance is that the "image is in focus from HALF hyper focal distance to infinity".

So that means ~33cm to infinity.

suho0515 commented 3 years ago

@suho0515 I will give you more details. The way to calculate the hyper focal distance of an imaging system is H= focal length focal length / (circle of confusion F-number)

The circle of confusion is how many pixels of blur you can tolerate. Let's set it to 2 pixels. Since each pixel is 1.4um, this means 0.0028mm.

For D435 the color imager has focal length of 1.91mm. Finally the F# is also a lens spec. It is 2.

With this the hyperfocal distance is 65cm.

However, the definition of hyper focal distance is that the "image is in focus from HALF hyper focal distance to infinity".

So that means ~33cm to infinity.

sorry for late answer,

and Really appriciate for your details.

It is absolutely helpful, and the answer what I was looking for.

Now the Issue is completely resolved.

Thanks again @agrunnet and @MartyG-RealSense

MartyG-RealSense commented 3 years ago

You are very welcome @suho0515 - it's great to hear that the advice provided by @agrunnet was helpful to you. Thanks for the update!

JZhu1208 commented 3 years ago

Hello @MartyG-RealSense @agrunnet,

I want to know what the focal length of the color imager and F# are for L515. Thank you very much.

MartyG-RealSense commented 3 years ago

Hi @JZhu1208 The table below is taken from the data sheet document for the L515 camera.

image