An open-source digital Optophone
(An open-source text to speech device for visually impaired)

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CEHRI is a project aimed at facilitating the lives of visually impaired individuals by providing an extremely tangible, cheap, repairable, and easy-to-build text-to-speech device.The main goal is to enable visually impaired individuals to access desired texts, particularly their favorite books, without language barriers and without having to spend a significant amount of money. It is designed not only for visually impaired individuals but also for illiterate children and adults.
CEHRI means "to say or read something openly, publicly, and loudly." in Ottoman.


Optophone is one of the oldest known methods of the sonification technique. Sonification can be defined as conveying information through sound other than speech like generating  time-varying chords of tones to identify letters. The Optophone device, was developed with a forward-thinking approach for its time, yet it can be considered limited and primitive by today's standards, using materials that could be deemed primitive even though the device itself is remarkable. It is said that the initial models of the device generate tone for only one word per minute, while later models were capable of generating up to 60 words per minute. We use the term tone because these devices do not actually produce a human voice or anything close to it. One or several tones are assigned to represent each letter. The device recognizes and identifies the letters and plays the corresponding tones. The user understands the word based on these tones that they have previously learned and recognized. In essence, the user learns the language of sound tones in order to comprehend the corresponding words. It wouldn't be wrong to say that they have to learn another language in order to read. It is similar to the way one needs to know Braille in order to understand embossed books used for tactile reading. It is truly challenging, indeed...

Detail view of the optophone(Wikipedia)
Detail view of the optophone

Before starting anything:

Before starting to building anything I began with examining previous examples to bring to life the idea of creating a device that can narrate books. I realized that commercial products and DIY enthusiasts are predominantly focused on digitizing books. In simpler terms, they are striving to create book scanners. On the internet, you can often come across individuals sharing their projects on book archiving through forums. These designs showcase huge and complicated systems that prioritize capturing clear images using fixed lighting and camera setups, lacking portability. However, for the prototype I envisioned to create a portable, lightweight device using minimal and affordable components that users could easily carry with them. Since device won't be engaging in archiving, image quality is not a crucial factor for me. Instead of image clarity, I chose to focus on producing a small-sized device that can be manufactured from simple materials. In this context, it immediately comes to mind that everyone has powerful smartphones with cameras boasting millions of megapixels, serving as practical and accessible image sensors. However, let's imagine a scenario where a person who is blind, visually impaired, or has lost their sight attempts to read a book page using an image sensor like a mobile phone or computer camera. How will they align it? How will they ensure that the camera accurately captures the text? It is extremely challenging, perhaps even impossible. Unless you create a rigid and rectangular frame like scanners, unless you secure the position of the paper, it is nearly impossible to properly and proportionally align the entire page within the camera's frame. Taking these limitations into account, I realized that I needed to design a system where the positions of the camera and book page are always fixed. When examining previous designs of book archiving devices, I observed that a transparent glass is placed in front of the page to prevent the natural curvature of the book page and ensure a flat surface facing the camera. Additionally, a uniform lighting system is employed to provide equal illumination across all corners of the page. In the initial prototype, I utilized an aquarium made of glass with rectangular prism shape to secure the book as the basic structure for the scanning platform.

1st Prototype
1st Prototype

Working video of first prototype:

About the hardware :

It's time for Raspberry Pi to take the stage since we've reached the point of designing a system that can capture photos of the book placed...

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python code

x-python-script - 8.57 kB - 05/24/2023 at 15:38


24.09.2020 v2.skb

HW design file.

skb - 1.22 MB - 05/24/2023 at 15:38


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  • Future improvements:

    rdmyldrmr05/24/2023 at 17:23 0 comments

    • Replace RPi4 with an older version or maybe with an ESP32
      • Since image processing and OCR have duty is handled in the cloud RPi only works for getting the image uploading to the OCR service, receiving the text, uploading the text to tts service, receiving the audio file and finally playing the audio file. All this can run on an older RPi or maybe a ESP32 can handle very well. 
      • This will reduce the cost dramatically.
    • Replace foam structure with wooden.
      • With wooden structure device will be more rigid and easy to carry. For these prototypes all pieces are glued and can be damaged from a fall or a weak crash.
    • Replace official RPi camera with a regular USB webcam.
      • There are plenty of cheaper webcams.
      • This will reduce the cost dramatically.

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