Problem to be solved: to provide a lens unit having a cover member free from accuracy and capable of efficiently producing at a low cost.Lens unit 10A includesThe shape of the side surface of the cover member 14a from the front end face 29 to the rear end face of the lens side is formed into a regular square columnAt least two corners of each corner of the regular quadrangle abuts against the inner peripheral surface 27 of the accommodation space 17 accommodating the cover member 14A of the holderA gap 34 is formed between each side surface of the cover member 14a and the inner peripheral surface 27 of the holderThe effective area of the light beam is located inside the light receiving area of the regular square column surrounded by the outer peripheral edge of the front end face 29 of the cover member 14a.Diagram【課題】精度の狂いがないカバー部材を備え、廉価に効率よく製造することができるレンズユニットを提供する。【解決手段】レンズユニット１０Ａでは、カバー部材１４ａの前端面２９からレンズ側の後端面に続く側面の形状が正四角柱に形成され、正四角柱の各角の少なくとも２つの角がホルダー１１ａのカバー部材１４ａを収容する収容スペース１７の内周面２７に当接し、カバー部材１４ａの各側面とホルダー１１ａの内周面２７との間に間隙３４が形成され、光線の有効エリアがカバー部材１４ａの前端面２９の外周縁に囲繞された正四角柱の受光エリアの内側に位置している。【選択図】図１
