He was born in July 1591 in Bremen, Germany, to where his parents had fled from Belgium to escape religious persecution. He acquired great reputation for his knowledge of the oriental languages. He was also an able lawyer and divine and took his degree of doctor in the latter faculty. He studied the oriental languages under Drusius and Erpenius and after having been professor of theology and Hebrew at Harderwijk for eight years was in 1627 made professor of Hebrew at Leyden on which occasion he delivered an harangue on the dignity and utility of the Hebrew language and it was his constant endeavour to diffuse a knowledge of that language and of the Arabic and Syriac among his countrymen that they might be the better enabled to combat the objections of the Jews to the Christian religion.
In 1639 John Maurice of Nassau, governor of Dutch Brazil appointed him his counsellor. He died in June 1648 very soon after he had begun a course of theology at Leyden. He lived in much intimacy with Lewis de Dieu, Daniel Heinsius and the Buxtorfs who were speaking very highly of him. He offered at one time to superintend the printing of a Talmudical dictionary in Holland and endeavoured to bring the younger Buxtorf to Leyden who had undertaken to defend the vowel points against Louis Cappel. He was also corresponding with the notable archbishop Usher.
L'Empereur's works are: Commentarius ad codicem Babylonicum, seu Tractatus Thalmudicus de mensuris Templi (Leyden, 1630), Versio et Notae ad Paraphrasin Josephi Jachiadae in Danielem (Amsterdam, 1633), Itinerarium D. Benjaminis in Hebrew and Latin (Leyden, 8 volumes), Moysis Kimchi Grammatica Chaldaica (Leyden, 8 volumes), Confutatio Abarbanelis et Alscheichi in caput liii Isaiae (Layden, 8 volumes, 1631, in French 1685), Commentarius in Tractatum Thalmudicum, qui dicitur Porta, de legibus Hebraeorum forensibus in Hebrew and Latin (Layden, 1637) and Commentarius ad Betramum de Republica Hebraeorum (1641, 8 volumes).
- For a biography of Lewis de Dieu, see Alexander Chalmers, The General Biographical Dictionary:, "Lewis de Dieu", Vol. 12, p. 65. Printed for J. Nichols, 1813.
- Peter T. van Rooden, Theology, biblical scholarship, and rabbinical studies in the seventeenth century: Constantijn L'Empereur (1591–1648), professor of Hebrew and theology at Leiden (Vol. 6 of the Studies over de geschiedenis van de Leidse universiteit), ISBN 90-04-09035-5.
- Alexander Chalmers, The General Biographical Dictionary, "Empereur (Constantine)", Vol. 13, pp. 203, 204. Printed for J. Nichols, 1814.
- Talmudis Babylonici codex Middoth sive de mensuris templi, Elzevir, 1630. Also, here  and here 
- D. Isaaci Abrabanielis et R. Mosis Alschechi Commentarius in Esaiae Prophetiam 30, Elzevir, 1631.
- Itinerarium D. Beniaminis (Travels of Rabbi Benjamin, son of Jonah), ex officinâ Elzeviriana, 1633.