David McConaghie was accused of recording a woman in the toilets at MP David Simpson's constituency office.
A court viewed footage showing what appeared to be McConaghie placing the device in a bowl of potpourri.
McConaghie, from Cottage Hill, Dollingstown, denied making recordings for his sexual gratification.
The court heard he had made them over a period of several weeks in August and September 2012.
When the camera was discovered, Mr Simpson immediately reported it to police, and McConaghie resigned his position.
McConaghie will be sentenced in five weeks' time.
In a statement, Mr Simpson said he welcomed the decision by the judge.
"This has been an extremely difficult time for my staff, but particularly for the victims," he added.
Mr Simpson paid tribute to the bravery of his staff in giving evidence and withstanding "a harsh, invasive cross-examination".

More than 500 complaints have been made to the Environment Agency about the site in Cormongers Lane, Redhill.
It said it was monitoring gas emissions and would consider formal action against operator Biffa if it was found to be breaching its permit.
Biffa said if did not believe levels of hydrogen sulphide detected posed a threat to human health.
Residents have been complaining about the smell from the site, described as like rotten eggs or sewage, for several weeks.
Green Party councillor Sarah Finch said it reached its worst levels earlier in the week.
"It smells like normal household gas, sometimes with a tinge of sewage smell," she added.
"It is a very unpleasant smell which catches in your throat and can make you gag."
Paul Bennett, from the Environment Agency, said officers were at the site at least once a day to collect data.
The information will be sent to Public Health England to assess whether it poses a risk.
"If Biffa don't keep the gas within the site and we find that they are breaching their environmental permit, then we are going to consider formal action against the company," he said.
Biffa said it had installed a flarestack as a temporary measure, which would burn off the excess gas.
It said a blue or yellow flame may be visible at night.
"This action is being taken with the knowledge of the Environment Agency and is a tried and tested method to increase gas extraction capacity," it said.
"Biffa has undertaken monitoring of the odours and provided the results to the Environment Agency.
"Biffa's interpretation of these results is that the levels of hydrogen sulphide detected do not pose a threat to human health."

The woman, known as the Lady of Cao, belonged to the Moche culture in northern Peru and died 1,700 years ago.
Her preserved remains were found in 2006 at a mud-brick ruined pyramid known Huaca Cao Viejo, near Trujillo.
Scientists were able to replicate her face after analysing her skull structure and remains.
The Lady of Cao was buried with a crown, and gold and copper items.
The grave also contained a number of weapons, including two massive war clubs and 23 spear throwers.
A modern autopsy revealed she had been in her 20s when she died, probably of childbirth or pregnancy complications.
Her feet, legs and face were tattooed with magic symbols of serpents and spiders.
The richness of her burial site suggests she might have been a priestess or even a political ruler.
The discovery challenged the belief that only men held high positions in ancient Moche society.
Peru's minister of Culture, Salvador del Solar, said the reconstruction had revealed an oval face with high cheekbones, which many Peruvians shared and would recognise.
"We are privileged to announce this strange combination of the future and the past: technology has allowed us to see the face of a political and religious leader from a culture from the past."
Oval face and high cheekbones - a close-up of the replicated face

It was decided that the surface at the Silverlake Stadium was unsafe during an 08:45 GMT inspection on Tuesday.
Eastleigh must now wait until Saturday's visit of struggling Woking as they look to record their first league win of 2017.
They are 12th in the National League table, eight points adrift of the play-off places and two behind Macclesfield.
A former church minister and DUP adviser accused of secretly filming a colleague for sexual gratification has been found guilty of the offence.
[NEXT_CONCEPT]
The operator of a Surrey landfill tip could face legal action over a smell of rotten eggs coming from the site.
[NEXT_CONCEPT]
Scientists in Peru have managed to reconstruct the face of a powerful ancient female leader using 3D printing.
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Tuesday's National League game between Eastleigh and Macclesfield has been postponed because of a frozen pitch.