A recent article on Slate.com "The Microwave Gets Its First (and Possibly Best) New Feature in Decades", and elsewhere under different titles, described work done by an engineer Mark Rober who put an infrared sensor in the top of a microwave oven and installed the screen in the oven-door claiming that it provides a "heat map" which can be used to control a microwave oven and prevent non-uniform heating, i.e. cold spots, in the microwaved products. Mr. Rober has applied for a patent for his device and is put it on a crowd-funding site.
I have several comments, historical, technological, and commercial:
Historical: this is not a new idea, as anyone involved in the food industry knows. Many large food companies have used this technique mapping hot and cold spots on products such as pizza. Also, years ago I used an IR sensor coupled to a controller circuit to operate prototype microwave oven for the sterilization of dental instruments, thereby preventing overheating of special components. What is new about Mr. Rober's idea is linking it to a mapping screen in the door of the oven so the user can see a temperature map of what's cooking. I'm not sure how meaningful that would be to a consumer who doesn't have a technical background since that sort of map is not easy to interpret. However, I'm sure that computer software can be supplied that would simply indicate when it areas cold and when it's hot instead of showing thermally generated colors. This doesn't mean that Mr. Rober won't obtain a patent for his technology as a means of controlling a microwave oven for a particular reason.
Technological: there is a serious technical flaw in this idea, namely that one can use the surface temperature of an object to determine the interior temperature of that same object. Mr. Rober claims this is true, but I doubt that it is, having for many decades, studied the thermal profiles of foods being heated in microwave ovens. We all know about the difficulty of heating something like a frozen chicken breast in a microwave oven and obtaining a uniform temperature throughout; combine this with a starch such as rice or mashed potatoes, vegetable such as broccoli, a sauce of some kind on the vegetables, the starch or the chicken and perhaps two or three of them, and the problem becomes enormous - something I don't believe can be analyzed by a surface temperature measurement to say when the single or multi-component product is evenly cooked or heated throughout.
Commercial: if we assume that this invention is technically feasible and does what the inventor claims it does, then there is a question of whether or not it can be a commercial reality. As I understand it, this invention would be an add-on to a conventional microwave oven and need to contain, at least in part, an infrared temperature mapping sensor with a wide enough viewing range of you to cover a diameter of at least 8 inches, plus a "screen" showing the temperature distribution on the product, or some analog, and an interface to the control circuit of the microwave oven in order to control the power when the product is supposedly done – maybe even control the output power. Obviously, this could be done manually, but that would mean the consumer would need to stand by the oven and watch the screen, something I doubt can be relied upon. So how much would such a system cost? At this point I have no idea, but let's say components might cost as little as 5 dollars, how much would that impact the selling price of a microwave oven? In the appliance industry the usual markup for an appliance is on the order of 4 to 5 times the manufacturing price, so a 5 dollar addition to the manufacturing price of a microwave oven would result in an increase of approximately 25 dollars in the price retail. How likely is this in the age of ovens that sell as cheaply as $50 and consumers paying on the order of $129 to $149 for countertop ovens (my own assessment)? In the United States where many consumers are bargain hunters so the additional cost may inhibit sales, but may be successful in higher priced over-the-range or built-in ovens. There will always be consumers willing to pay premium prices for products, but that is not the mass-market that accounts for most of the 9 to 10 million ovens sold every year. As I write this, it just dawned on me that I haven’t included the cost of new tooling for incorporating infrared system. It's been my experience that microwave oven manufacturers, most of which are in China today, are reluctant to add even a small fraction of that amount to the component cost of a microwave oven.
So, while I applaud Mr. Rober for his invention and dedication, I question whether this will ultimately result in a significant consumer product.