An early Digital Camera
Some years ago it became evident that photography was going digital. I had the idea that the best way to learn about digital cameras was to make one. So I started designing a camera for my telescope in 1997.
The best sensor I could afford was a monochrome 1/3" Sony CCD (ICX084AL). The resolution is just VGA, megapixels was exotic and expensive at that time. The sensor is cooled by a Peltier element as it was intended for astronomy.
It is all built from scratch. A couple of Sony circuits are used in the CCD clock generating block. They are not taking care of all timing and clocks so there are a lot of logic ICs in the backend as well. On the frontend the analog signal is going through amplification, sample and hold, correlated double sampling and a 12-bit ADC. There's a lot of interesting things going on in this part of a camera and I had to spend a lot of time designing the analog circuits to get it right.
1997 was just at the darn of the USB interface and the fastest link I had to my computer was the parallel port. Fast readout of the sensor to the computer was not possible so the camera has a frame buffer memory.
The best sensor I could afford was a monochrome 1/3" Sony CCD (ICX084AL). The resolution is just VGA, megapixels was exotic and expensive at that time. The sensor is cooled by a Peltier element as it was intended for astronomy.
It is all built from scratch. A couple of Sony circuits are used in the CCD clock generating block. They are not taking care of all timing and clocks so there are a lot of logic ICs in the backend as well. On the frontend the analog signal is going through amplification, sample and hold, correlated double sampling and a 12-bit ADC. There's a lot of interesting things going on in this part of a camera and I had to spend a lot of time designing the analog circuits to get it right.
1997 was just at the darn of the USB interface and the fastest link I had to my computer was the parallel port. Fast readout of the sensor to the computer was not possible so the camera has a frame buffer memory.
I was not aiming for an industrial design prize with this one. It was cumbersome to align and focus the camera because of the slow parallel interface. The solution was to later add an optical viewfinder having a flip mirror.
There are five PCBs packed with electronics. The camera is operated from a PC where the entire image processing also takes place. Today's CMOS sensors do it all plus color processing and JPEG compressing in a single chip just a few square millimeters in size at a cost less than what you pay for a hamburger.
The evolution of digital cameras has moved fast. By the time the camera was ready it was almost outdated. Nevertheless it was a good project as I learned a lot about digital cameras, image sensors and image processing.
The evolution of digital cameras has moved fast. By the time the camera was ready it was almost outdated. Nevertheless it was a good project as I learned a lot about digital cameras, image sensors and image processing.
An early test image from the camera equipped with a Nikkor 28 mm/2.8 lens. There is no digital noise reduction applied. Sorry but I have not saved any data for exposure time etc. Anyway, I don't expect anyone to copy this design today.
The software was written in C++ using Visual Studio and MFC. Images can be saved in bmp- or raw 12-bit format.
Copyright © Mats Wernersson
