JPS6324457Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an optical element in which an interference filter is formed in an optical fiber for blocking background light from received modulated light of a light wave distance measuring device.

Conventionally, a transmitting optical system having a light emitting element, a reflector,
In a light wave distance measuring device that consists of a receiving optical system including a light emitting element and a light receiving element, and measures distance by phase shift of the received modulated light, an optical fiber is used to connect the light emitting element and the light receiving element to their respective transmitting and receiving optical systems. known to be used. This optical fiber is useful for installing the light-emitting element and the light-receiving element in the most structurally or electrically advantageous location, and is also useful for mixing and homogenizing the phase unevenness of the oscillation modulated light in the transmitting optical system. There is. In addition, a measure is taken to prevent reflection loss from the end surfaces of the optical fiber by adhering glass anti-reflection plates to both end surfaces of the optical fiber.

In addition to the modulated optical signal from the transmitting optical system, the light received by the light-receiving element in the above-mentioned light wave ranging device includes broadband natural light, so-called background light, and this background light is superimposed as a bias component of the modulated optical signal. This causes disturbance to the signal light and impedes distance measurement accuracy. For this reason, a conventional method has been adopted in which an interference filter is installed on the receiving optical path to transmit light within the wavelength band of the light emitting element and to block other wavelength bands. This interference filter for blocking background light has a structure in which a glass plate on which a dielectric multilayer film is vapor-deposited and a colored glass plate that blocks transmission bands other than the used orders are bonded with the film surface inside. A conventionally known method is to install a plate on the optical path in front or behind the optical fiber.

As mentioned above, in addition to the optical fiber with an anti-reflection plate glued to it, the optical configuration of a rangefinder that includes a separate interference filter has many optical components, and the space for both the transmitting and receiving optical systems is extremely limited. These optical members had to be arranged at the same time, making it difficult to adjust the optical axis, and furthermore, there was a reflection loss at the outer surface of the interference filter.

Therefore, in the present invention, there are fewer optical members,
The optical configuration is simple and occupies less space.
An optical element of a light wave distance measuring device that has no reflection loss and can easily adjust the optical axis, that is, an interference filter is constructed by bonding a glass plate coated with an interference film on each end face of an optical fiber and a colored glass plate to prevent reflection. The purpose is to provide an optical element that has the effect of blocking background light and also has an optical fiber function.

Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings. The received modulated light 1 that has been emitted from the light emitting element and reflected by a reflector (none of which is shown) is incident on the objective lens 3 and then focused on the center point F ₁ of the input end of the optical fiber 4 . The emitted light (received modulated light) from point F2 at the output end of the optical fiber ₄ is incident on the light receiving surface of the light receiving element 6 through the relay lens 5, and distance measurement is performed by the phase shift of the received modulated light. Note that the center point of the input end of the optical fiber 4
F ₁ must be on the optical axis 2 of the objective lens 3, but the point F ₂ at the output end of the optical fiber 4 does not necessarily have to be on the optical axis 2 as shown in the figure, but can be eccentrically or deflected as desired. There is no problem even if this point is met.
In other words, since the optical fiber 4 has flexibility, it has a function of aligning the received modulated light from its emitting end with the center position of the light receiving element 6.

A glass plate 7 on which an interference film 9 is deposited is adhered to the input end face of the optical fiber 4, and a colored glass plate 10 for color correction is adhered to the output end face, respectively.
Both glass plates 7 and 10 constitute an interference filter for blocking background light. It is well known that if the refractive index of the glass plates 7, 10 and the adhesive are selected to be approximately the same as the refractive index of the optical fiber 4, it will be effective to prevent reflection. For completeness, an anti-reflection coating 8 can be deposited on the outer surfaces of both said glass plates 7,10. If the interference film 9 has excellent environmental resistance and does not require protection from the surrounding atmosphere, the interference film 9 can be attached to the surface of the glass plate 7. In this case, the antireflection film 8 becomes unnecessary, and costs can be reduced. Furthermore, if a colored glass plate with an interference film deposited thereon is bonded to the input end face of the optical fiber 4, it goes without saying that a normal transparent glass plate may be bonded to the output end face.

As explained above, the optical element in which an interference filter is configured on an optical fiber according to the present invention has fewer optical members than conventional devices and can be easily installed even in a small space. It was possible to combine the effects of light blocking and anti-reflection.

Furthermore, optical elements such as the present invention can be used for optical information processing using light emitting diodes, laser diodes, etc.
It can be expected to have a wide range of applications as an optical element for optical measurement, optical communication, etc.

[Brief explanation of the drawing]

The figure shows an embodiment of the present invention. 3: objective lens, 4: optical fiber, 5: relay lens, 6: light receiving element, 7: glass plate with interference film deposited, 9: interference film, 10: colored glass plate.

Claims (1)

[Scope of utility model registration request] In a light wave ranging device that is composed of a transmitting optical system having a light emitting element, a receiving optical system including a reflector and a light receiving element, and measures a distance by a phase shift of received modulated light,
A glass plate is adhered to each end surface of an optical fiber provided on the optical path from the light emitting element to the light receiving element,
In addition, the glass plate on the incident side is a glass plate on which an interference film is deposited, and one of the two glass plates is a colored glass plate,
An optical element for a light wave ranging device, characterized in that both glass plates constitute an interference filter that blocks background light from received modulated light.