The 53-year-old was apparently 'curious' about his son's sexual exploits, so decided to install a spy camera in the loft above the 21-year-old's bed.
He then proceeded to record his son having sex with his 19-year-old girlfriend - and even linked the video feed to a television in his kitchen, so that he could watch them whilst he was cooking.
The man's crimes were exposed when his younger daughter accidentally switched to a different channel on the TV and found herself staring at live images of her brother's bed.
She told her brother's girlfriend and, together, the pair uncovered the camera and several naked screenshots.
After the camera was discovered, however, the man's 12-year-old daughter then found the courage to reveal that he had been sexually abusing her,
Speaking at Oxford Crown Court, Judge Ian Pringle QC said: “It is an appalling abuse of trust.
“A greater breach of trust is difficult to imagine. You wanted to spy on their sexual activity, curious as to what was going on and you even printed out a picture of your son’s girlfriend naked.
“You say you don’t know why you committed these offences and that it gave you no real sexual gratification.”
The father confessed to eight counts of sexual activity with a child and two of voyeurism.
He was sentenced to four years in prison on Friday.