An orthographic lens has no perspective. Instead, parallel rays remain parallel to the image and don't converge. An orthographic lens is useful for when you want the 2.5D look or when you're rendering 2D objects that shouldn't have perspective anyway. To use an orthographic lens, you need to set the left, right, top, bottom, near and far boundaries. Your near boundary can actually extend behind the viewer. Not that moving around a world while using a orthographic lens can be disorienting since objects will not get smaller as a factor of distance.
Include "myWindow.ortho(left, right, bottom, top, near, far)" in your script.
Replace myWindow with a window that you've previously added.
Replace left, right, bottom, top, near, and far with values for the left, right, bottom, top, near and far boundaries you want to capture.
Example:
viz.add('carousel.wrl')
window = viz.addWindow()
window.ortho(-1,1,-1,1,-1,1)
Viewpoints & windows command tables