How to get the distance from an object to android device using camera2 API

Question

I want to get the distance from an object to android device using android camera2 API. In CaptureCallback, I get the value by result.get(CaptureResult.LENS_FOCUS_DISTANCE) and check LENS_STATE, CONTROL_AF_MODE, CONTROL_AF_STATE at the same time. They are "STATIONARY", CONTINUOUS_PICTURE and PASSIVE_FOCUSED. I think the focus distance should be valid and the distance from an object to android device should be 1/focus_distance. But in fact the calculated value is totally different from the actual distance. What's wrong with it? Is LENS_FOCUS_DISTANCE the correct value for distance estimation? Anyone have idea?

final CameraCaptureSession.CaptureCallback captureCallbackListener = new CameraCaptureSession.CaptureCallback() {
    @Override
    public void onCaptureCompleted(CameraCaptureSession session, CaptureRequest request, TotalCaptureResult result) {
        super.onCaptureCompleted(session, request, result);
        Log.e(TAG, String.format("captureCallbackListener %s-%f", lensStateToString(result.get(CaptureResult.LENS_STATE)), result.get(CaptureResult.LENS_FOCUS_DISTANCE) ));
        Log.e(TAG, String.format("AF mode %s-%s", ctlAfModeToString(result.get(CaptureResult.CONTROL_AF_MODE)), ctlAfStateToString(result.get(CaptureResult.CONTROL_AF_STATE)) ));
    }
};

Possible duplicate of [Is it possible to measure distance to object with camera?](http://stackoverflow.com/questions/4588485/is-it-possible-to-measure-distance-to-object-with-camera) — SaravInfern, Nov 23 '16 at 13:16
To avoid down vote, try to search your queries first and then post the question — Myth, Nov 23 '16 at 13:16

score 4 · Answer 1 · answered Nov 24 '16 at 00:14

Please check the value of CameraCharacteristics.LENS_INFO_FOCUS_DISTANCE_CALIBRATION. If it's UNCALIBRATED or APPROXIMATE, then the value of LENS_FOCUS_DISTANCE will likely not be close to reality.

And even with CALIBRATED, the farther objects are, the more error there will be - to the camera, everything past the hyperfocal distance (a few meters at best) starts being impossible to accurately measure distance to.

How to get the distance from an object to android device using camera2 API

1 Answers1

Linked