SALEM — The Police Department is getting a new camera with an eye for license plates.

Officers will soon start using a mobile license-plate reader capable of scanning up to 1,500 license plates per minute in hopes of tracking down offenders ranging from wanted felons to unlicensed drivers to parking ticket scofflaws.

The technology — already in use by the Boston police and tested out by Peabody officers — can scan both moving and parked vehicles as a cruiser patrols a city street. Two infrared cameras on the back of the cruiser can pan back and forth and are capable of capturing an image of the car and the plate and cross-checking it with a database in the trunk of motor vehicle and criminal records.

When the reader gets a hit, it sends a signal to the officer, who can issue a citation or make an arrest.

Police said yesterday the new technology will help them to do their job faster, take more criminals off the street and ultimately make the city safer.

"A police officer can, maybe if he's lucky, put 100 plates into a computer during an eight-hour period," Chief Robert St. Pierre said. "What you're doing is really doubling or tripling the effectiveness of one officer on the street."

Especially at a time of severe budget cuts — the number of Salem officers is down 20 percent — police need to turn to technology like the license-plate reader and citywide surveillance cameras to fight crime, he said.

"This has potential to stop all kinds of crime," St. Pierre said. "We have fewer police officers, so we need to rely on technology to pick up the slack. This couldn't come at a better time for us."

It also raises some concerns.

Chris Ott, a spokesman for the American Civil Liberties Union of Massachusetts, said he didn't find the technology itself objectionable but wondered what will happen to the information after it's collected.

"Is that all being stored somewhere?" Ott said. "If so, for how long, and who has access to it? ... Do we want to have all those databases of where people's cars were at particular times available?"

Randy Chapman, the president of the Massachusetts Association of Criminal Defense Lawyers and a former Essex County prosecutor, said he isn't bothered by the new technology.

He did, however, wonder if the court system could handle the expected increase in the number of defendants summoned to court.

He also wondered whether a savvy divorce attorney could subpoena the records to find out if a client's spouse was in the vicinity of a third-party love interest.

"Internally, regulations will have to be set up for the way the information is used," Chapman said. "But I trust the Police Department to ... use it in a way that would be proper."

Salem police Capt. Brian Gilligan said there is an overwhelming benefit. The city has a 55-page "tow and hold" list of cars whose owners have racked up five or more outstanding parking tickets or have other violations. Rather than force an officer to memorize a seemingly endless list of license plates, the computer can automatically detect the offender's car if it's nearby.

It could also help track down a car being sought during an Amber Alert. Or it could download license plate numbers for high-level sex offenders to determine whether they're hanging around school zones, Gilligan said.

The technology cost just under $22,000 and came from the city's capital budget. However, it's also expected to generate a significant amount of new revenue as more citations are issued.

It will only be installed in one cruiser.

"If you're obeying the laws and you're not wanted for anything, you don't have anything to worry about," St. Pierre said. "I think it's going to make the community a better place."