After losing its crown in portable music players and television, Sony is now joining Apple and Google in targeting the hottest new battleground: automobiles.

Sony recently invested about 100 million yen ($842,000) to buy a stake of roughly 2 percent in ZMP, a Japanese startup making robot cars. The two firms ultimately hope to develop self-driving car technologies by combining Sony's expertise in image sensors with ZMP's robotics knowhow, according to people familiar with the deal.

Sony's move comes as tech is changing the game - and players - in the automotive industry, creating driverless cars and sparking a rush of interest from Silicon Valley. Apple is recruiting experts in automotive technology and vehicle design to work at a new top-secret research lab, according to people familiar with the company.

Despite its troubles in TVs and smartphones, image sensors - the eyes of a camera - remain one of the few areas where Sony maintains the top market share.

Now, the Japanese electronics and entertainment group hopes to replicate the success of its sensors in smartphones with cars.

Smartphones is a much bigger market with annual global sales exceeding 1bn units, while global vehicles sales are only expected to exceed 100 million units in a few years.

But analysts say a vehicle could be installed with as many as 10 cameras when the age of self-driving cars arrive, and these cameras are likely to be four to five times more costly than a smartphone camera. IHS consultancy estimates that shipments of automotive cameras will increase more than threefold to 102 million units by 2020.

In an interview, Shigeo Ohba, general manager of Sony's image sensor business, said he expects demand for automotive image sensors will expand significantly from 2017 and continue through 2030.

"We have to be No 1 in automotive sensors" by the time self-driving cars are expected to hit the roads in early to mid-2020s, Mr Ohba said.