Police officers found thousands of sick images of children on a laptop computer belonging to a registered sex offender, a court heard.
They carried out a routine check on the Sheffield home of Robert Nixon, aged 33, who was already subject to a Sexual Offences Prevention Order.
More than a quarter of a million images were found on his laptop and police examined over 4,000 of them said prosecutor Ian West at Sheffield Crown Court.
The court heard Nixon, of Lupton Walk, Lowedges, was jailed for 26 months in 2008 for downloading and possessing indecent images and sexually assaulting a nine-year-old girl.
He admitted six new specimen charges of making indecent images.
Andrew Swaby, defending, said he fully co-operated with police and had not re-offended since his arrest.
Recorder Bernard Gateshill jailed Nixon for three years and told him to sign the Sex Offenders Register for life.