A Thermo Vision Corp. shareholder has issued a complaint against the planned merger of the company and its parent, Thermo Instrument Systems Inc. In early July, Thermo Vision's board of directors voted to sell the company's outstanding common stock held by minority shareholders for $7 a share. That move would enable Thermo Instrument Systems to assume 100 percent ownership of the company. The complaint alleges that stockholders would be "deprived of their investment and the benefits to accrue therefrom, for a grossly inadequate price." It further alleges that the "intrinsic value of the stock of Thermo Vision is materially in excess of $7 per share." Since July 1998, the stock has traded between $2.06 and $6.75. A spokesman for the Waltham, Mass.-based company had no comment on the suit.