Reflective condensing interferometer

A reflective condensing interferometer for focusing on a preset focus, comprising:

• a concave mirror set having at least a first concave surface portion and at least a second concave surface portion which are oppositely located on two sides of a central axis and are concave on a surface facing the central axis;
• a convex mirror disposed on the central axis and convex toward the concave mirror set;
• a light splitting element vertically intersecting with the central axis on a side of the convex mirror facing away from the concave mirror set;
• and
• a reflecting element disposed between the light splitting element and the convex mirror;
• wherein
• when incident light is incident toward the convex mirror from a side of the convex mirror facing away from the light splitting element in parallel to the central axis, the incident light is sequentially reflected by the convex mirror and the first concave surface portion or the second concave surface portion toward the preset focus, and when passing through the light splitting element, the incident light is split by the light splitting element into detection light to be transmitted toward the preset focus and reference light to be reflected toward the reflecting element;
• wherein
• if the detection light and the reference light are split at a first position on the light splitting element, the detection light to be subsequently emitted toward and reflected at the preset focus, and the reference light to be subsequently emitted toward and reflected at the reflecting element converge, at a second position on the light splitting element symmetrical to the first position based on the central axis, into emergent light to be emitted away from the preset focus, and are then sequentially reflected by the second concave surface portion or the first concave surface portion and the convex mirror;
• wherein the incident light has first wavelength light and second wavelength light, and the split detection light and reference light pass through a detection light path and a reference light path respectively before convergence, an optical path difference between the detection light path and the reference light path being equal to common multiples of a half wavelength of the first wavelength light and a half wavelength of the second wavelength light.

A reflective condensing interferometer for focusing on a preset focus, comprising:

• a concave mirror set having at least a first concave surface portion and at least a second concave surface portion which are oppositely located on two sides of a central axis and are concave on a surface facing the central axis and the preset focus, wherein the central axis passes through the preset focus, and light is preset to be incident into the reflective condensing interferometer in parallel to the central axis during use of the reflective condensing interferometer;
• a convex mirror disposed between the concave mirror set and the preset focus on the central axis and convex away from the preset focus;
• and
• a light splitting element vertically intersecting with the central axis on a side of convex mirror facing away from the preset focus;
• wherein when incident light is incident toward the convex mirror from a side of the convex mirror facing the light splitting element in parallel to the central axis, the incident light is split by the light splitting element into detection light for transmission and reference light for reflection when passing through the light splitting element, and the detection light is sequentially reflected by the convex mirror and the first concave surface portion or the second concave surface portion to be emitted toward the preset focus and then reflected at the preset focus;
• wherein the incident light has first wavelength light and second wavelength light, and the detection light has a detection light path from leaving the light splitting element to returning to the light splitting element, the detection light path being equal to common multiples of a half wavelength of the first wavelength light and a half wavelength of the second wavelength light.