Arrange pineapple on a baking sheet; freeze 2 hours or until firm.
Combine yogurt, sugar, and lemon juice in container of an electric blender; top with cover, and process until blended.
Add pineapple; process until smooth.
Pour mixture into a 13- x 9- x 2-inch baking dish.
Cover and freeze 2 to 3 hours or until firm.
Scoop 1/2 cup yogurt into each individual dessert bowl; top each serving with 1/4 cup raspberries.
Garnish with fresh mint sprigs, if desired.