NEW YORK — Nicole Miller is getting serious about lingerie.

The designer has expanded her three-year-old daywear and sleepwear line with a group of romantic floral print pieces in silk georgette. Describing the new print as “serious,” Miller said this is a deliberate departure from the whimsical conversational prints that have been her trademark — in her dresses and innerwear as well as men’s ties.

“What happens is you get pigeonholed. People always say, ‘Nicole does the funny prints.’ But what they don’t understand is the quality of the artwork involved in my prints.”

The floral print group also has a semi-sheer look that is designed to wear at home or as part of a ready-to-wear or sportswear ensemble.

The group was introduced to retailers this month. The print is a mix of lilies, roses and poppies, and is offered in black on a white ground, or vice versa. The designer said she will introduce a second “serious” floral print in March.

At the same time, Miller’s lingerie business — an in-house effort of Nicole Miller Ltd., of which she is designer and president — is developing into some serious volume.

Miller projected the new groups of “serious” prints will do $1.5 million in their first year. She also expects that her conversational print innerwear will almost double its sales this year to $3 million. While new conversationals are added throughout the year, the collection continues to feature such favorite motifs as theater ticket stubs, vodka bottles and junk foods.

Styles in the new print group include: a camisole; a tank top; a spaghetti strap teddy; a drawstring tank bodysuit; a short robe, and three chemises — a cap-sleeve Empire style, a long chemise and a tank style.

Wholesale prices start at $45 for a camisole and go to $100 for a robe.