Oakley Inc. Chairman and President Jim Jannard said he plans to buy as many as 3 million shares of the sunglass maker, adding to the almost 4 million he has bought since 1997. The latest purchase would be valued at about $38.5 million based on Monday's stock price. Jannard, who founded Oakley, owns about 38.6 million shares, or 54.6% of the outstanding stock. Jannard said Oakley's shares are "substantially undervalued" based on its growth prospects. The Foothill Ranch-based company is introducing new glasses and preparing to launch its first line of athletic shoes later this month. The company's shares have risen 17% over the last 12 months, compared with the 20% gain in the Russell 2,000. Oakley's shares slid to a low of $8.31 in January from a high of $27.19 in May 1996 as the company was hurt by a United Parcel Service strike and a slowdown in sales to Sunglass Hut International Inc., its largest customer. Shares in Oakley fell 25 cents to close at $12.81 on the New York Stock Exchange. Jannard forfeited his salary last year after deciding in 1996 to base his pay entirely on the company's performance.