The analytical and laboratory instrument-maker and distributor has taken a 66% stake in the Scottish company.
The Asian corporation also signalled an intention to boost investment and add to the 70-plus workforce, who are based at EI's 12,800 square feet premises in Livingston, West Lothian.
The deal sees physics professor Des Smith, who founded EI as the first spin-out from Heriot-Watt University in 1971, selling his shareholding while investors Hammatsu Photonics and Scottish Enterprise are also exiting.
It is understood Techcomp is looking to buy up the remaining shares – held by a number of small shareholders including former employees – in the coming months and take full control of EI.
According to the most recent annual return document at Companies House, Mr Smith was the largest single shareholder with more than 31,000 of the company's 100,000 ordinary shares suggesting his windfall is likely to be a high six-figure sum.
The 81-year-old is staying on as a Techcomp chief scientific officer.
EI chief executive Alan Faichney, previously a co-founder of Edinburgh-based seismic software company Concept Systems and part of the team which sold it for $36m to American corporation Input/Output, is leaving to pursue other interests.
Mr Faichney has overseen a period of strong growth for the gas sensor, spectrometer and laser-maker during his more than two-and-a-half-years in charge.
In its most recent financial year, EI recorded a rise in turnover from £6.2m to £8.2m. Pre-tax profits rose from £316,452 to £437,708 in the 12 months to March 31, 2012.
The acquisition by Techcomp is expected to open up wider global sales channels for EI.
EI chairman Derek Shepherd said: "Our products provide research institutes worldwide with the most advanced photonic analytical capabilities. EI is now ready to start a new phase of development.
"Techcomp's knowledge and global presence in our high-end analytical markets position them as the perfect partner to help release the full potential of our technologies."
Chris O'Connor, chief executive of Techcomp Europe, said: "We are delighted to have the opportunity of adding Edinburgh Instruments to our portfolio of businesses and to be able to expand our range of technologies and products. EI has a fantastic reputation for innovating and supporting leading-edge research globally, and we are excited about investing in the business and working with the employees to take it to the next level.
"The depth of knowledge and experience within the team at EI is truly impressive."
Techcomp, which is dual listed on the stock exchanges in Singapore and Hong Kong, added: "This acquisition will also allow Techcomp to acquire complimentary technology as well as leverage on the brand equity of Edinburgh Instruments.
"Techcomp has the intention to further acquire the remaining shares of [EI] so that [it] will become a wholly owned subsidiary of the company."
Outside of its Hong Kong headquarters, Techcomp has offices in Macau, India, Singapore, Vietnam, Indonesia and Malaysia, as well as a network of 17 bases across China.