President Reagan has signed a bill restricting employers' use of lie detectors. The polygraph measure was co-sponsored by Sen. Orrin Hatch, R-Utah, and Sen. Edward M. Kennedy, D-Mass.

Hatch said the bill restricts use of polygraphs to investigations of accidents or thefts in the workplace.It disallows routine use in employment, but permits polygraph investigations of drug use and other security cases.

Hatch praised what he called the teamwork of Labor Secretary Ann McLaughlin and William Wynn, of the United Food and Commercial Workers Union.

"Workers," Hatch said, "will now no longer have to face the humiliation of being hooked up to a machine just to apply for a job."