Wrong coordinate from display to world

I am using vtkCoordinate to convert mouse click pixel to world coordinate,
When I do the convert, I backup the current camera clipping range and change to a clipping range when first click, then do the convert.

var pos = GetInteractor().GetEventPosition();
var camera = renderer.GetActiveCamera();
var clipOld = camera.GetClippingRange();
	if (points.Count == 0)
	   clipRange = camera.GetClippingRange();

	camera.SetClippingRange(clipRange[0], clipRange[1]);
	vtkCoordinate coordinate = vtkCoordinate.New();
	coordinate.SetValue(pos[0], pos[1]);
	return coordinate.GetComputedWorldValue(renderer);
	camera.SetClippingRange(clipOld[0], clipOld[1]);

This works fine in the beginning, but when I zoom in the camera to a certain level, I always get almost the same point, but I think it should have some distance.

[13:58:30 INF] Point:[96.892307717881508, 76.743746693872936, -38.267776752685485]
[13:58:30 INF] Point:[96.883216117087429, 76.7392462461047, -38.311059009029137]

Well, that is the expected behavior unless you move the object in the world.