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First published on: 1-9-2011
A Low-Cost Large-Size Document Scanner
Mandar Thite developed a low-cost scanner priced 10 times lower than scanners currently available in the market
Thite decided to experiment with his 7.2-megapixel Canon Powershot A550 digital camera. He found that if he could digitally clip the captured images, it could turn out much cheaper. He developed a simple mechanism using easily available components like a camera, magnetic push-pull solenoid, permanent magnet DC motor and cycle tube along with a time synchronisation technique.
The scanner is created using a retrofit attachment for a digital camera using a magnetic solenoid, motors and a rubberised roller. The apparatus includes a digital camera, a stand to hold it and a mechanism to feed documents to the camera continuously, so that these can be photographed. The digital scanner consumes only 15 watts of power. This innovation was recognised as one of the top five winners of ‘The Next50 Global Innovation Challenge’—an IIT Kanpur initiative.
How it works
In existing digital scanners images are captured by a charge-coupled device (CCD) array. A lamp is used to illuminate the document and the image of the document reaches the array through a series of mirrors, filters and lenses. The exact components vary according to the scanner models but the components are pretty much the same.
In Thite’s digital scanner, a camera is mounted over a platform and a magnetic push-pull solenoid is fixed next to it. With power supply the solenoid gets pushed towards the camera’s click button. The camera clicks a photograph of the document and instead of the lamp the flash provides the light. The image gets stored on its memory card. Though the solenoid and motorissed roller are two separate units, these are synchronised to work together. These have separate controls with suitable 12V DC power supply. The maximum print-size depends on the area the camera can capture.
On the lower platform, the mechanism used is similar to that of a printer. Paper is fed into the machine by using a roller feeding system. The feed mechanism consists of an electrical motor for which power is required. A rubberised roller—in this case a PVC pipe wrapped with a simple cycle wheel’s tube—is placed at the top of the papers. It is controlled by a 12-watt motor which rolls out paper soon after the camera captures the image. The tube rolls out the scanned document from the platform and the next document is ready before the camera.
“In other large-size document scanners there is no provision for sheet-feeding. Here, the papers are fed onto the platform with the roller,” Thite reveals. The next cycle begins as the camera clicks an image of the new document.
For transferring photographs to the computer system, Thite used the camera’s software. After transferring the images to computer, text can be extracted by using an optical character recognition (OCR) software.
Challenges that Thite faced
Time synchronisation between the camera, solenoid and roller is one of the essential elements of this digital scanner. Thite bought timer circuits and integrated a time sequence that matched the process into it. The timers have been set such that there is a three-second gap between the camera-click and the roller movement. This time interval gives the camera enough time to charge its flash.
“I have used three timers—for the camera to click, for the motor that rolls the paper out and for the time interval that stands between the two. At first, the roller moved the paper too fast and the camera was not given enough time to click the image. I tried different time configurations and finally found the required time interval, i.e., three seconds,” Thite explains.
Another area that required improvisation was the camera-click. “I first used a motor for the click mechanism but the speed of the click was low. I then decided to try a magnetic push-pull solenoid and found that it works well,” Thite explains.
The cost factor
Already available large document scanners will cost you at least Rs 200,000. “If you look at my final prototype, I have spent about Rs 3000 on the attachment by using standard parts available in the market and other components. I fitted the attachment to a digital camera that cost around Rs 7000. So the total attachment cost me about Rs 10,000,” Thite reveals. However, he intends to use more advanced components in the final product.
What lies ahead
Thite is working on a saleable model of the scanner that can be used in libraries and by architects. “I am also looking for investors who can take this innovation forward and push it to the market,” Thite concludes.
The author is from EFY Bureau, Bengaluru
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