Extended depth-of-field camera

By combining a unique lens from its optical technology with image processing technology, Ricoh has developed a camera that greatly extends the depth-of-field.

Depth of field refers to the range of distance over which a subject appears in-focus in a photographic image. An extended depth-of-field camera extends the depth of field without sacrificing resolution or brightness, making it possible to clearly capture a subject without adjusting interval and angle between a subject and a camera. Scenes that used to require multiple cameras or readjusting focus can now be captured at once with a single camera. Because focusing components are unnecessary, our extended depth-of-field camera has excellent stability and reliability. Further, a compact machine vision can be realized, enabling applications in a variety of fields such as factory automation (FA), distribution, security, and personal applications.

Our extended depth-of-field camera comprises a specialized lens and a specialized camera with a built-in image processor. The depth-of-field can be extended with a typical camera by using a smaller aperture, but the image becomes darker. With our camera, the depth-of-field can be extended while maintaining brightness. We are developing a lineup of specialized lenses with various focal lengths (such as 8 mm, 25 mm, and 50 mm). We are also developing different types of specialized cameras with 2 MP and VGA resolutions, for example.

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Usage scenario 1: foreground and background imaging

Whereas capturing subjects in both the foreground and the background previously involved multiple cameras or changing the camera position, it is now possible to keep both the foreground and the background in focus without readjustment. As a result, our cameras can be applied to QR code recognition and object recognition on moving production lines, for example. To capture subjects separated in the field by a range of several tens of centimeters, for example, the combination of a specialized lens with an 8 mm focal length and a specialized VGA camera is suitable.

Figure 1: Usage scenario for capturing subjects at different depths

Imaging result from traditional camera. Front QR code is unreadable.	Imaging result from extended depth-of-fieldcamera. Both front and rear QR codes are readable.
Figure 2: Comparison of images from conventional camera and extended depth-of-field camera

Usage scenario 2: capturing oblique subjects

Whereas capturing oblique subjects previously required multiple cameras or that the camera be refocused, it is now possible to keep an oblique subject entirely in focus without readjustment. As a result, multiple images no longer need to be stitched together after separately capturing near and distant portions of a subject. Instead, information on the entire subject can be captured in a single shot. Potential applications include OCR and substrate inspection.

Figure 3: Usage scenario for capturing an oblique subject

Usage scenario 3: capturing subjects at different heights

Whereas capturing subjects at different heights previously involved multiple cameras or changing the vertical position of the camera, it is now possible to keep multiple subjects at different heights in focus without readjustment. Potential applications include object recognition on moving production lines for products of different heights, and image recognition in cases where printed matter is progressively stacked higher.

Figure 4: Usage scenario for capturing subjects at different heights

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