Please help me find an embedded camera

Hi all

I am new to this embedded scene and I really need some help. I am trying to assemble a PC104 camera solution that fullfills the following criteria:

- must use as little power as possible

- obviously the cheaper the better :)

- the camera startup time must be very quick

- the time needed for taking a picture must be very quick (fast moving subjects)

- the camera must be able to take pictures in darkness (at night) without a flash

- the pics need to be 640x480 black and white

- once the image is captured, I would like it to eventually end up as a JPEG so that the filesize is minimal. This is because it will be transmitted via a GPRS module.

I might be betraying my ignorance with the above list, but any information would be useful to a newbie such as myself. Thanks in advance for any help.

Regards Adam Wynne

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Adam Wynne
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Without some sort of budget it is difficult to determine. Also it depends on whether you want a still/video camera, how much control over the camera you need, how much of the camera and lighting part of the system you will build.

What is very quick ??? 0.5s, 1ms, 1us??

How much control over the camera you want affects this, as well as your lighting and possibly lens control systems.

Short exposure time in cameras is not a problem, your problem will be lighting and lenses, which also depends on the distance of the object, other ambient lighting and lighting effects (e.g. are you going to have the travel of the sun to contend with).

You do not say if this is triggered by an external device or time interval or by picture content to determine if you need a still camera or video camera, or even camera chips.

So you need an IR extended range CMOS camera, but how are you going to light the object being photographed? Cameras cannot make light happen, YOU will have to flood the area of the object at the right distance with some form of IR source (LOTs of IR LEDs), this will push power consumption up.

How often are you wanting to take images? Are you taking one image or a sequence?

How do you want to capture the image? USB, Firewire, analog grabber another mothod?

How often you are taking images and what you are doing to images are mainly system dependent, JPEG compression is really the domain of your PC104 system. Some cameras do this, but you are unlikely to get fast setup, fast grab, and especially night vision as these are meant for people to take snapshots.

Your choice of compression may not be the best choice as it is a lossy compression, compression choices depend on range of image content you need, range of image noise and resolution you need amongst many other things.

As you say this is using GPRS I can ONLY assume this is an external box so will the camera be part of a weatherproof enclosure or need its own weatherproof (possibly vandal proof) enclosure. The environment will greatly affect what you need and cost.

There are too many unknowns to give a sensible solution primarily as you don't say how much building you are expecting to do.

You would be amazed how much power even the cheap security cameras with night illumination use and you have no control over exposure time etc..

Paul Carpenter          |
    PC Services
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Paul Carpenter

Hi there, me again :)

The camera will be used for still photos only and I don't care what interface is used to get to the camera (firewire/USB etc). The startup time and capture time should be about 100 ms.

I don't mind how much building I have to do regarding assembling the system, but would obviously prefer as little as possible.

If there's one constraint that can be let slip, its cost. So if I can buy a night vision enabled single shot digital camera module, I'd rather do that then build my own.

Thanks again Adam

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So forget USB web cameras and probably firewire as the setup time is NOT determined by the camera but the vagueries of the operating system and everything attached to it. Some can take seconds to load their drivers and get sorted out with USB software.

What is your budget? If less than 100 UKP/USD/EUR don't expect anything more than random capture of an image that will randomly be synced with what you were expecting to take a picture of.

First you have got to get some camera fundamentals sorted IN THIS ORDER

1/ How fast EXACTLY is the object moving 2/ How fast an exposure time is required to get a still from that object without blur. 3/ How FAR away is the object and Field of View required

These determine lenses and how much lighting is required, the further away the object, the amount of light (lux) illuminating the object goes up by at LEAST a SQUARE as lux is an area measurement.

Is the object reflective/absorbent of light? What angle and type of lighting is required?

These will affect how you light the object, and image quality.

Then can you illuminate the object with the SAME amount of lux at NIGHT? If not forget night time capture.

This is true of ALL types of cameras photographic/video/still using film, analog or digital electronics. Putting electronics instead of film does not change the laws of physics relating to optics and the like.

Now you know how much the lighting and lenses is going to cost in money and power consumption, so you now know if the cost and power budget are still possible.

How do I trigger the camera trigger ACCURATELY to the motion of a 'high speed' object? This determines what you have to do for camera latency of trigger and exposure.

THEN and ONLY THEN can you start to look for a camera that can do those characteristics. As you may not be able to put the right lenses or lighting or control exposure time on any old cheap module.

Once you have the camera your choices of capture method can be sorted. Along with how you ACCURATELY trigger the camera to take the picture which if it is high speed object will HAVE to be HARDWARE as software especially via USB will be as accurate as a mythical 'man month'.

Doing it the WRONG way round guarantees the old adage of computers and HiFi

Garbage In Garbage Out

To give some idea two stories for you:-

1/ A certain printing press had continuous paper being monitored at high speed (10m/s and above), so had short exposure time and a lot of light at close distance (0.5m and less), Only a measly little 7KW of light. They had to be careful about stopping the press BEFORE turning off the lights otherwise it was an expensive mistake.

They were printing paper money! (Legally)

2/ UK Highways surface inspection research vehicle to measure cracks in road surface from 2mm upwards, using TDI line scan cameras synchronised to pulses from the wheels at speed up to 50mph (approx 22m/s), had special light pipes in an enclosed and skirted box close to the road. Light level about 3KW and line scans being done at over 11KHz rate.

I doubt you will easily find a cheap camera module to do what you want. You desparately need to check what your front end is doing first not from the back end of PC104 system outwards.

Computer systems are relatively cheap and have various options more than your camera choices are.

If you don't understand your front end issues the rest is a waste of time!

Paul Carpenter          |
    PC Services
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Paul Carpenter

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