JPH10293024A - Electronic level - Google Patents

Abstract

PROBLEM TO BE SOLVED: To expand a range where the quantity-of-light ratio of an image sensor is constant without making darker a visual field with naked eyes by providing a filter layer for transmitting visible rays and shielding infrared rays annularly at the tip side from a beam splitter. SOLUTION: A beam splitter 14 transmits visible rays included in light being applied to an objective lens 11 toward the side of an eye piece lens part 15. In this case, infrared rays are branched to a CCD image sensor 2 without being transmitted. The CCD image sensor 2 reacts with infrared rays and converts an image according to received infrared rays to the image signal of an electrical signal. In this case, an annular filter layer with a light axis as a center is formed, at least, at one of a front surface 11a and a rear surface 11b of the objective lens 11. Then, with a wavelength of 700 nm as a boundary, visible rays with a short wavelength are transmitted and infrared rays with a long wavelength are shielded by adjusting the thickness of the filter layer, thus expanding a range where the distribution of the quantity of light of infrared rays is uniform on the CCD image sensor 2 without making darker a visual field with naked eyes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic level for receiving, by an image sensor, light split by a beam splitter provided in a telescope.

[0002]

2. Description of the Related Art As a conventional device of this type, for example, Japanese Patent Application Laid-Open No. 6-241789 discloses a system in which a beam splitter is arranged in the optical path from an objective lens of a telescope for collimating a staff to an eyepiece. There is known an automatic level in which a part of the light incident on an image sensor is branched to an image sensor to form an image, and a position of a collimation point on a staff is automatically read. A CCD image sensor is widely used as the image sensor. The CCD image sensor receives visible light and converts it into an image signal which is an electric signal. However, the CCD image sensor has a characteristic of converting an infrared ray which cannot be sensed by a human into an image signal. Therefore, as the beam splitter, a beam splitter that transmits visible light to the eyepiece lens side and splits infrared light to the CCD image sensor side is used. I am trying to become.

[0003]

In the above-mentioned conventional telescope, so-called "vignetting" such as vignetting occurs, and when the branched infrared rays reach the image sensor, the amount of light at the center of the image sensor is reduced. The amount of light in the peripheral part surrounding the part is reduced. When an image sensor recognizes a wide field of view, the ratio of the amount of light at the peripheral portion to the amount of light at the center of the image sensor (hereinafter, referred to as a light amount ratio) becomes small. Then, if the image processing standard is adjusted to the light amount in the central part, the image in the peripheral part is too dark to perform image processing. Conversely, if it is adjusted to the light amount in the peripheral part, the central part is overexposed, Cannot process.

In such a case, it is conceivable to replace all the optical systems disposed behind the objective lens with those having a large diameter, but there is a problem that the weight of the electronic level itself increases. In addition, by reducing the effective diameter of the collimation range, it is possible to reduce "blur", but since the amount of visible light guided to the eyepiece is also reduced similarly to infrared, the collimation image with the naked eye is darkened. Failure occurs.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an electronic level in which the light amount ratio on an image sensor is constant without darkening the visual field with the naked eye.

[0006]

In order to solve the above problems, the present invention provides an objective lens, a focusing lens, a compensator, a beam splitter that transmits visible light and splits infrared light, in order from the tip side. At the electronic level equipped with a telescope in which eyepieces are arranged and an image sensor that receives the infrared rays split by the beam splitter and converts them into image signals, transmits visible light to the tip side of the beam splitter and blocks infrared rays The filter layer is provided annularly around the optical axis of the telescope.

[0007] By providing the above-mentioned filter layer, the effective diameter of infrared rays is reduced, so that the influence of "gazing" on infrared rays reaching the image sensor is reduced. Then, the range of the light amount equal to the light amount of the central portion on the image sensor expands to the peripheral portion. Since the light amount ratio is constant when the light amounts are the same, the range in which the light amount ratio is constant is wider than when the filter layer is not provided. On the other hand, since the filter layer transmits visible light without blocking it, the brightness of the visual field with the naked eye is as bright as that without the filter layer.

When the present invention is applied to an existing telescope, for example, a filter in which a filter layer is formed in a ring shape on the surface of a transparent glass plate or the like is formed, and the filter is attached to the distal end side of the beam splitter. Good.

When the filter layer can be formed on at least one surface of the objective lens and the focusing lens, it is not necessary to newly add the filter. Note that a CCD image sensor may be used as the image sensor.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, reference numeral 1 denotes an optical system provided in an electronic level telescope, and an objective lens 11, a focusing lens 12, a compensator 13 and a , Beam splitter 14 and eyepiece 1
5 are arranged. The beam splitter 14 transmits visible light included in the light incident on the objective lens 11 to the eyepiece unit 15 side, but transmits infrared light to the eyepiece unit 15.
The light is not transmitted to the side and branches to the CCD image sensor 2. The CCD image sensor 2 reacts not only to visible light but also to infrared light, and converts an image of the received infrared light into an image signal which is an electric signal. Therefore, even if only the infrared rays are branched from the CCD image sensor 2 by the beam splitter 14, there is no problem in outputting the image signal from the CCD image sensor 2. Here, in the present invention, an annular filter layer IF is formed on at least one of the front surface 11a and the rear surface 11b of the objective lens 11, as shown in FIG. The filter layer IF is formed by depositing Al ₂ O ₃ as a first layer on the surface of the objective lens 11, depositing SiO ₂ on a second layer thereon and an even-numbered layer thereon, and a third layer and thereafter. A mixture of ZrO ₂ and TiO ₂ (trade name: Optron OH5) is applied to the odd-numbered layers. Then, the film thickness of the filter layer IF is appropriately adjusted so that the wavelength is 700 n.
At the boundary of m, visible light having a wavelength shorter than 700 nm is transmitted, but infrared light having a wavelength longer than 700 nm is shielded. Therefore, in FIG. 2, visible light is incident from the entire surface of the objective lens 11, but infrared light is incident only from the non-coating portion NF surrounded by the filter layer IF.

As shown in FIG. 3, on the surface of the CCD image sensor 2, the infrared light intensity distribution L2 when no filter layer is provided has a flat light intensity distribution D2.
However, in the light amount distribution L1 in the case where the filter layer is provided, the light amount distribution expands to a flat range D1. Note that C in FIG.
Indicates the center of the CCD image sensor 2. Incidentally, the filter layer IF is not limited to being formed on the objective lens 11, but may be formed on at least one of the front surface 12a and the rear surface 12b of the focusing lens 12.

As described above, the objective lens 11 and the focusing lens 1
Although a filter layer may be formed directly on the existing telescope, when a filter layer is added to an existing telescope, for example, a filter 3 having an annular filter layer similar to the filter layer IF formed on a transparent plate such as a glass plate is used. May be arranged in front of the beam splitter 14 as shown in FIG. In FIG. 4, the filter 3 is disposed between the compensator 13 and the focusing lens 12. However, if the filter 3 is located ahead of the beam splitter 14, such as between the objective lens 11 and the focusing lens 12 or in front of the objective lens 11, It should just be placed in a place.

[0013]

As is clear from the above description, the present invention provides a method for collimating a staff or the like at an electronic level without reducing the distribution of the amount of infrared light on the CCD image sensor without darkening the visual field with the naked eye. A wide uniform range can be secured.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an electronic level to which the present invention is applied;

FIG. 2 is a diagram showing a shape of a filter layer.

FIG. 3 is a diagram showing a light intensity distribution of infrared rays on a CCD image sensor.

FIG. 4 is a diagram showing a configuration of another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical system (of a telescope) 2 CCD image sensor 3 Filter 11 Objective lens 14 Beam splitter

Claims (3)

[Claims] 1. A telescope in which an objective lens, a focusing lens, a compensator, a beam splitter that transmits visible light and splits infrared rays, a telescope in which an eyepiece is arranged, and a beam splitter are arranged in this order from the front end side. At an electronic level having an image sensor that receives infrared light and converts it into an image signal, a filter layer that transmits visible light and blocks infrared light is provided on the tip side from the beam splitter.
An electronic level characterized by being provided in a ring around the optical axis of the telescope. 2. The electronic level according to claim 1, wherein said filter layer is formed on at least one surface of an objective lens and a focusing lens. 3. The electronic level according to claim 1, wherein the image sensor is a CCD image sensor.