Optical: systems and elements – Lens – With variable magnification
Reexamination Certificate
1999-06-21
2001-12-18
Spyrou, Cassandra (Department: 2872)
Optical: systems and elements
Lens
With variable magnification
C359S696000, C359S822000, C359S823000, C359S824000, C359S825000, C359S835000, C356S329000, C356S370000, C356S495000, C250S201900, C250S203700
Reexamination Certificate
active
06331918
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light interception structure for an AF sensor of an automatic focus detection surveying instrument.
2. Description of the Related Art
In a, conventional auto-focus surveying instrument having a collimating telescope, such as a total station, an optical system is composed of a collimating optical system including an objective lens, a focusing lens, a Porro prism, a focusing plate and an eyepiece in this order from the object side, and a beam splitting optical system including a beam splitter provided in the vicinity of the Porro prism to split a light path of a focus detection optical system from a light path of the collimating optical system. In the focusing system, the focus state of a plane which is optically equivalent to a focal plane of the collimating optical system located within the focus detection optical system is detected by a phase difference detection type auto-focus sensor having a pair of CCD sensors to calculate the amount of defocus (defocus amount), so that a focusing lens is moved to a focal position in accordance with the defocus amount to carry out the automatic focusing (AF) operation.
However, in the conventional structure, since the beam splitting system and the Porro prism are located on the optical axis of the collimating optical system, if external light enters the collimating optical system through the eyepiece, the external light reaches the AF sensor due to internal reflections, so that the external light overlaps the light emitted from the objective lens, thus resulting in an incorrect focusing operation.
SUMMARY OF THE INVENTION
The primary object of the present invention is to provide an automatic focus detection surveying instrument in which light incident through the eyepiece is intercepted so as not to reach the AF sensor, so that a precise focusing operation can be carried out.
To achieve the object mentioned above, according to an aspect of the present invention, there is provided a light interception structure for an automatic focus detection surveying instrument including a telescopic optical system having an objective optical system and an ocular optical system, a beam splitting optical element which splits object light transmitted through the objective optical system from the telescopic optical system, and a focus detection device having a light receiving device for receiving the object light split by the beam splitting optical element, wherein one surface of the beam splitting optical element upon which external light entering the telescopic optical system through the ocular optical system is first made incident after the external light passes through or is reflected by a beam splitting surface of the beam splitting optical element is subject to an anti-reflection treatment.
Preferably, the anti-reflection treatment is for light diffusion.
Preferably, the anti-reflection treatment for light diffusion is surface polished.
Preferably, the surface of the beam splitting optical element which is subject to the anti-reflection treatment is coated with an anti-reflection paint.
According to another aspect of the present invention there is provided a light interception structure for an automatic focus detection surveying instrument including a telescopic optical system having an objective optical system and an ocular optical system, a beam splitting optical element which splits object light transmitted through the objective optical system from the telescopic optical system, and a focus detection device having a light receiving device for receiving the object light split by the beam splitting optical element, wherein an inner surface of the automatic focus detection surveying instrument receives emitted external light which is first made incident on and passes through the surface of the beam splitting optical element after passing through a beam splitting surface of the beam splitting optical element which allows the external light to pass through or reflect therefrom.
Preferably, one surface of the beam splitting optical element upon which external light entering the telescopic optical system through the ocular optical system is first made incident after the external light passes through or is reflected by a beam splitting surface of the beam splitting optical element is coated with an anti-reflection layer.
Preferably, the anti-reflection treatment includes an application of a fabric or cloth to the surface.
The anti-reflection treatment can be an application of a molt plane to the surface.
The anti-reflection treatment can be a coating of an anti-reflection paint.
According to another aspect of the present invention, there is provided a light interception structure for an automatic focus detection surveying instrument including a telescopic optical system having an objective optical system and an ocular optical system, a beam splitting optical element which splits object light transmitted through the objective optical system from the telescopic optical system, and a focus detection device having a light receiving device for receiving the object light split by the beam splitting optical element, wherein a reflection surface is provided in a position opposed to a surface upon which external light entering the telescopic optical system through the ocular optical system and emitted from the beam splitting optical element is first made incident after the external light is transmitted through or reflected by the beam splitting surface of the beam splitting optical element so as to reflect the external light emitted from the beam splitting optical element in a direction whereby the light does not reach the beam splitting optical element.
Preferably, the reflection surface is formed on an inner surface of a barrel of the automatic focus detection surveying instrument.
The present disclosure relates to subject matter contained in Japanese Patent Application No.10-176348 (filed on Jun. 23, 1998) which is expressly incorporated herein by reference in its entirety.
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Asahi Kogaku Kogyo Kabushiki Kaisha
Curtis Craig
Greenblum & Bernstein P.L.C.
Spyrou Cassandra
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