Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
  • G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
  • G02B26/0875—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more refracting elements
  • G02B26/0883—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more refracting elements the refracting element being a prism
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B13/00—Optical objectives specially designed for the purposes specified below
  • G02B13/0005—Optical objectives specially designed for the purposes specified below having F-Theta characteristic
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
  • G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
  • G02B26/10—Scanning systems
  • G02B26/108—Scanning systems having one or more prisms as scanning elements

Definitions

• the invention relates to a device for deflecting a beam into a plane by means of a deflection prism that is rotatable about an axis and constant deflection and an imaging system associated with the deflection prism, in particular an F- ⁇ (theta) objective.
• Devices of this type are used in scanner systems.
• a beam of rays emanating from a light source is deflected by a rotating deflecting element and imaged as a light spot on a surface to be scanned by means of an imaging system. Due to the rotating deflecting elements, the beam is e.g. deflected into a plane. The surface is scanned line by line.
• the invention has for its object to provide a simple to manufacture deflection prism of the type described with good synchronism.
• the deflecting prism is a square prism according to Wollaston and the axis of rotation is oriented approximately perpendicular to one of the two prism surfaces which form a right angle with one another. It has been shown that with a known Wollaston square prism within a generic device, a surprisingly favorable design of the deflecting element with regard to the distance between the axis of rotation and the center of gravity of the prism, the prism weight and the one determining the input focal length of the downstream imaging system Distance between the axis of rotation and the prism part furthest from this can be achieved. In comparison to a penta prism designed for the smallest dimension, a square prism according to Wollaston has a lower weight.
• the input focal length of the following imaging system is the same as the input focal length required for a Penta prism. It is particularly advantageous, however, that the Wollaston square prism can be positioned so that the mechanical center of gravity of the square prism comes very close to the center of gravity of the incident, parallel light. Since the prism rotates around the center of gravity of the incident, parallel light, there is almost no unbalance in comparison with the penta prism. The synchronism properties are thus considerably improved, particularly at high speed.
• a square prism made of wool. "Ton has two mirrored and two non-mirrored surfaces. The adjoining non-mirrored surfaces form an angle of 90 ° with one another.
• beam guidance would be possible in which a bundle of rays, which is oriented parallel to the axis of rotation, enters the square prism through the first non-mirrored surface, which is approximately perpendicular to the axis of rotation, and then at the surface without mirroring adjacent mirrored surfaces and then reflected on the further mirrored surface, in order to finally emerge from the quadrangular prism via the second non-mirrored surface.
• An optimally small input focal length of the imaging system can, however, be achieved in particular with the preferred embodiment of the invention specified in claim 2.
• the input surface of the square prism is chosen to be larger than the beam bundle intersection surface.
• the two prism surfaces oriented perpendicular to one another in the direction perpendicular to their line of intersection have the width claimed in claim 3.
• Fig. 2 shows a section through a square prism according to Wollaston. Representation of an embodiment
• Deflecting prisms are shown in both figures, which are intended to deflect the incoming beam by 90 °. Neither the imaging systems nor the brackets and bearings of the respective prisms are shown in the two figures.
• the imaging system associated with a prism can be arranged in the beam path before or after the prism.
• a beam for example a laser beam with the diameter d, enters the penta prism through the non-reflecting surface 1. After reflections on the mirrored surfaces 3, the beam of rays emerges from the penta prism through the non-mirrored surface 2. Rays 6, 7, 8 denote rays of this bundle of rays.
• the penta prism rotates about an axis, the position of which corresponds to the position of the beam 7 oriented perpendicular to the surface 1. S characterizes the position of the center of gravity, its distance from the
• Area 2 is denoted by s ⁇ .
• the distance between surface 2 and the cutting edge of surfaces 4 and 5 is denoted by t.
• FIG. 2 shows a quadrangular prism according to Wollaston. It has two non-mirrored surfaces 9, 10, which form a right angle, and two mirrored surfaces 11, 12. The surfaces 10, 11 and the surfaces 9, 12 enclose an angle of 67.5 °.
• a bundle of rays enters the quadrangular prism perpendicularly through surface 9 and becomes on the mirrored surface 11 reflected and subsequently totally reflected on the surfaces 10.9. After reflection on surface 12, the beam emerges from surface 10. The emerging ray bundle is bent by 90 ° with respect to the incoming ray bundle.
• the beam axis 14 is also the axis of rotation of the square prism. The axis of rotation is oriented approximately perpendicular to the prism surface 9, ie the axis of rotation forms a maximum angle of approximately 4 ° with the vertical on the prism surface 9 - depending on the refractive index of the glass.
• the beam 2 shows the ideal case of a non-tilted axis of rotation.
• the incident light rays are parallel to one another and to surface 10. With a the distance between surface 10 and the cutting edge between surfaces 9 and 12 is designated.
• the beam is at a distance x vo from surface 10, e.g. 0.15 d. The distance x is required so that a correct and complete deflection of a beam of rays is maintained even when the prism rotation axis is tilted.
• the radiation deflection caused by the square prism is sensitive to tilting of the prism rotation axis. Even in the case of tilting, the angle between the emerging ray bundle and the incoming ray bundle remains constant, the emerging ray bundle being merely shifted parallel to itself.
• the parallel optical bundles are focused by the following imaging optics, in the exemplary embodiment an F-theta optics of a scanner system.
• the focus of the square prism according to Wollaston is (distance s from surface 10) considerably closer to the axis of rotation of the prism than the center of gravity of the penta prism at its axis of rotation.
• the quadrangular prism therefore has almost no unbalance.
• the synchronism properties are considerably improved in comparison to the Penta prism.
• the distances t and a match, ie in both cases the same input focal length results for the imaging system.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Mechanical Optical Scanning Systems (AREA)
• Optical Elements Other Than Lenses (AREA)
• Mechanical Light Control Or Optical Switches (AREA)
• Facsimile Scanning Arrangements (AREA)
• Fax Reproducing Arrangements (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=6322305

Family Applications (1)

Country Status (5)

Families Citing this family (13)

Family Cites Families (7)

• 1987
  • 1987-03-05 DE DE19873707023 patent/DE3707023A1/de active Granted
  • 1987-12-04 US US07/128,868 patent/US4878720A/en not_active Expired - Fee Related
• 1988
  • 1988-03-05 EP EP88901806A patent/EP0305423A1/de not_active Withdrawn
  • 1988-03-05 JP JP63501975A patent/JPH01502618A/ja active Pending
  • 1988-03-05 WO PCT/DE1988/000122 patent/WO1988006744A1/de not_active Application Discontinuation

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events