Autofocus Intraoral Cameras – How They Work


Autofocusing Intraoral Cameras

Sometimes, a new product hits the market and while the salesman is gung-ho about its features and capabilities, the consumer is more ho-hum. Generally that’s because the so-called improvements are hard to notice or have almost no impact on the way the product is going to be used. Improvements to autofocusing intraoral cameras manage to step away from the stereotype and have dentists clamoring for the new ones.

In general, improvements to autofocusing technology have improved point and shoot cameras to the point where almost anyone can get professional quality photographs simply by buying the right camera. Worries about lighting and keeping the subject still for the perfect shot are distant memories. Instead, the camera does all the work, with shutter speeds so fast that the only delay in getting the perfect image often comes from the time it takes for the photographer’s brain to register that the image exists and his finger to push the button.

The Improved Technology

The reason it has gotten so much easier for virtually anyone to take great photographs is the continuing improvements in autofocus technology. Basically, for the camera lens to automatically adjust to the shutter speed, lighting and focus needed for a terrific photograph, a series of sensors has to quickly evaluate the circumstances and then adjust the camera settings to the right focus.

These sensors come in two varieties, active and passive. Active sensors send a signal to other part of the camera telling it that it needs more light (like a traditional flash) or that it needs to change the distance to the subject, sort of like spinning the focus on an older manual focus camera.

Passive sensors are contrast sensors within the camera. In the days before digital photograph, this would have been the estimate of the film speed needed to get the image. In modern digital imaging, the passive sensors tell the lens how long the aperture, the opening that lets in light, should stay open. In essence, the less light there is available, the longer the aperture stays open, allowing more light to reach the image being created.

In a fraction of a second, the sensors read all the data about the subject of the photograph and relay it to the camera, generally following these steps:

  1. The camera makes a small change in the focusing distance to see if the image is better.
  2. The sensors read the image and see how much, if any, the focus has improved.
  3. Using the information the sensors provided, the autofocus processor tries again.
  4. The process is repeated until the focus is clear, all taking less time than it does to press a button.

During the earliest days of autofocus cameras, the person taking the image held down the camera’s shutter release button – the button pressed to take a picture – until the autofocusing was done. One the focusing was done, the photographer released the shutter and then pressed it again to take the picture. The delay in this was literally fractions of a second, but there were times, especially if the lighting was poor, that it was a frustrating process, especially if the camera could not establish a clear focus.

The reasons why a camera couldn’t focus were almost always related to one of three things:

  1. there was not enough light,
  2. there was not enough difference, or contrast, between the primary subject and the background
  3. the subject was moving.

When dealing with intraoral cameras, all three of those factors are regularly a problem.

Most mouths have inadequate lighting for pictures and flashes or other camera-based light sources have to be carefully controlled to prevent overexposure. The contrast between teeth, tartar and gums is not always black and white, and patients move, even when they are trying not to. Whether it’s the automatic movement associated with breathing, flinching from the stimulus of having a camera in their mouths, or involuntary muscle spasms, the mouth has a lot of movement happening.

That meant that intraoral autofocus, in its infant stages, had the same problems as those early point-and-shoot cameras; sometimes, the dentist had to fight and fight to try to get the camera to focus only to be disappointed with the result.

The goal of autofocusing cameras has always been to create a camera that focuses as quickly (or quicker) than the human eye, adjusting to the ambient light and narrowing or widening focus depending on the distance to the image. For the most part, it remained a dream, until now.

The newest generation of intraoral cameras features more sensors than ever before and true autofocusing with no need for the technician or dentist to ever push a shutter button. Instead, the newest intraoral cameras are basically aimed at what the dentist wants to see and the camera does the rest. Sensors tell it how much light to emit from its six LEDs and it focuses on the subject in front of it. The dentist or technician can zoom in closer if necessary, but the time spent messing with the focus is done.

So why does a dental practice need something this sophisticated?

Dentists have been trying for generations to explain to patients what they see and what it means. With the new digital autofocusing intraoral cameras, patients can see in real time what the dentist sees. The patient may not understand the nuances of every bump or ridge, but the autofocusing camera makes it possible to see exactly what his dentist is trying to illustrate.

Equally importantly for the dentist, it saves time. Rather than spending minutes being frustrated trying to get the exact tooth image needed to illustrate the problem to the patient, the image is available almost instantly, making it possible for the dentist to handle one issue and move on to the next. As a direct result, the dentist has more time to spend on other areas of the patient’s care or with other patients, helping to improve the financial position of the practice.