A federal judge yesterday refused to allow television networks to copy video-taped testimony by actress Jodie Foster which may be used as evidence in John W. Hinckley's trial on charges of attempting to assassinate President Reagan.

U.S. District Court Judge Barrington D. Parker said, however, that he will allow the networks to record taped telephone conversations between Foster and Hinckley. Law enforcement officials believe Hinckley was obsessed with Foster and shot Reagan to gain her attention.

Parker's decision came in the midst of jury selection for Hinckley's trial, now in its fourth day. So far, 41 jurors out of a pool of 90 have tentatively qualified for the jury and 20 have been excused from service.

The protracted screening process became further bogged down yesterday when several jurors, already questioned once in private and found to be qualified, asked to meet again with the judge, prosecutors and defense lawyers. Court officials did not disclose the reasons behind the jurors' request.

Some of the lawyers in the case also said yesterday that they want to question some already-qualified jurors again. The private sessions were expected to cover a range of subjects, from the jurors' prior knowledge of the Hinckley case to their personal experiences with mental illness.

Hinckley contends he was legally insane when he shot and wounded Reagan and three others.

In his ruling yesterday involving Foster, Parker said the telephone conversation is "real evidence" of Hinckley's persistent efforts to communicate with Foster, while her video-tape testimony is only a description of events that she knew about.

The courts have said that the public's right to copy judicial records includes evidence such as taped conversation, Parker said. But, Parker said, Foster's taped testimony, necessitated because she was unavailable for Hinckley's trial, must be treated like "live testimony" from any other witness. No court has ever said such testimony could be recorded, Parker ruled.

Even if the video-taped testimony fit within the public's right of access to court records, Parker said Foster's expressed concern about her privacy and safety would outweigh demands for its release for public broadcast. In court papers, Foster's lawyers had cited the indictment in Connecticut of a man who had threatened Foster as well as Reagan.

"This court is not blind to the fact that the prosecution of an individual who allegedly tried to kill the president may possibly incite and provoke others within society, " Parker said.

Meanwhile, Hinckley will be in court this morning for a hearing on his defense lawyers' contention that testimony from government psychiatrists is "tainted" because they know about statements made by Hinckley which the court said were obtained illegally.

The prosecution argues that the information was a very small part of massive evidence that the doctors collected about Hinckley and had little if any effect on the psychiatrists' opinions about Hinckley's state of mind on the day of the shooting.

Hinckley has remained in a basement cell in the courthouse building since mid-morning Wednesday, when Parker moved the jury selection process to a private room.

Hinckley's absence from the courtroom has eased security concerns a bit. The only incident yesterday, for example, involved a woman who tried to get past the courthouse metal detector with a small antique alarm clock tucked in her brassiere.

Building guards and the woman herself were at a loss to figure why the security buzzer kept going off until a guard, using a hand held metal detector, conducted a "body sweep" and came up with the clock.

The woman, who was on her way to bankruptcy court, joked at first that she carried the clock so she wouldn't oversleep on the subway. Then she said she tucked the clock away because it is an antique, sources said.

Guards gave her a claim check for the clock, the woman ran her errand at the court, came back to retrieve it, and left.