JPS63315919A - Beam diameter measuring instrument - Google Patents

Abstract

PURPOSE:To obtain a stable focus gain by using a transmitted light quantity varying member which consists of two areas differing in transmissivity and is uniform in reflection factor. CONSTITUTION:The transmitted light quantity varying member 2 consists of the high transmissivity area 21, low transmissivity area 22, and a reflecting film 24 which covers the beam incidence surface of the transmitted light quantity varying member 2 so that the reflection factor to a beam 5 for automatic focusing is constant. Consequently, the quantity of reflected light on the surface of the transmitted light quantity varying member 2 of an automatic focusing laser can be made uniform, so the stable focus gain is obtained and the beam is focused on the surface of the varying member 2 at all times.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a beam diameter measuring device, particularly to a beam diameter measuring device for measuring the beam diameter of an exposure laser of a source disk mastering device. .

[Prior art] A conventional beam diameter measuring device uses a flat plate method transparent substrate and a knife-edge on the beam incidence surface of this transparent base.

A knife member having a transverse area of the original blocking surface formed horizontally and a means for moving the knife member in which the knife member crosses perpendicularly at a constant speed as a beam, and receiving and photoelectrically converting the beam transmitted through the transparent substrate. and photoelectric conversion means.

Next, an example of a conventional beam diameter measuring device will be described in detail with reference to the drawings.

In the beam diameter measuring device shown in FIG. 2, a lens 6 is driven by a known autofocus means using an autofocus beam 5, and a knife section 73 moves the beam 1 focused onto the surface of a knife member 70. 3, the beam l crosses at a constant speed with a moving force AK perpendicular to the original axis.

When the knife part 73 crosses the beam 1 in the upside-down position, a part of the beam 1 is filtered by the shielding part 72, and the intensity of the beam 1 transmitted through the transparent part 71 is reduced by the shielding part 72.
changes as it is blocked. This gradient change is received by the photoelectric conversion means 4 and photoelectrically converted to obtain a transmitted light amount signal a, which is analyzed by a known method to calculate the beam diameter of the beam 1. [Problems to be Solved by the Invention] ] However, the above-mentioned conventional beam diameter measuring device uses a knife member having a base end cross-sectional area made of a metal thin film or the like formed by vapor deposition on a part of a transparent substrate, and both ff1ll of the knife part Since the reflectance differs greatly, when the knife part crosses the beam, the reflected light weight of the autofocus beam fluctuates considerably, and if the focus gain is unstable, it is difficult to focus the beam on the surface of the knife part. The drawback was that the beam diameter at the focal plane could not be accurately measured.

[Means for Solving the Problems] The beam diameter measuring device of the present invention includes a variable amount of transmitted light member consisting of two regions having different transmittances for the beam, and a boundary between the two regions of the member that allows the beam to move at a constant speed. A vertically traversing means for moving the transmitted light amount variable member, and F4:i M pi 1fi.
A photoelectric conversion means that receives the beam transmitted through the semi-transparent variable member and converts it into electric current, so that the reflectance of the beam incident surface of the transmitted light amount variable member is uniform in two regions. Embodiment Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.

In a beam diameter measuring device (not shown in FIG. 1), a lens 6 is driven by a known autofocus means using an autofocus beam 5, and the beam 1 focused on the surface of the variable transmitted light amount member 2 is 23 is moved at a constant speed by the moving means 3 to the force plane A perpendicular to the original axis of the beam 1.
Make it Jyo5.

AiJ's variable transmitted light amount member 2 has a high transmittance region 21, a low transmittance region 22, and a beam incidence surface of the variable transmitted light amount member 2 coated so that the reflection of the mate focus beam 5 is constant. The boundary 23 between the two regions is formed by a straight line having a width sufficiently narrow with respect to the beam diameter of the beam 1 at the focal plane.

Therefore, when the boundary 23 crosses the beam 1,
The beam 1 has a part that passes through the high transmittance area 21 and a part that passes through the low transmittance area 22, and the boundary 23 here plays the role of a so-called knife edge.
By receiving the beam 1 transmitted through the transmitted light quantity variable member 2 by the photoelectric conversion means 4 and photoelectrically converting it, a transmitted light amount signal a can be obtained. Therefore, the beam diameter of beam 1 cannot be calculated using a known method.

Generally speaking, the surface of the variable member 2 (well, it is formed of a reflective coating 24 with a uniform reflectance, and is transparent)'
Since the reflection 'jt, f of the autofocus beam 5 is uniform in the surface member 2 area of the ef&E'T transformation member 2, a stable focus gain can be obtained, and the beam 1 always reflects the surface of the transmitted light IoT transformation member 2. can be maintained so that the focal plane is the focal plane, and the beam diameter of the beam 1 can be measured.

〔Effect of the invention〕

The beam diameter measuring device of the present invention uses a variable transmitted light amount member that is made up of two areas with different transmittances and has a uniform reflectance, instead of using a knife member made of a transparent substrate that partially has one analysis area area for light transmission. By using this, it is possible to make the amount of reflected light of the automatic laser for scraping uniform on the surface of the variable amount of transmitted light member, so a stable focus gain can be obtained and the beam can always be focused on the surface of the variable amount of transmitted light member. This has the effect that the beam diameter at the focal plane can be measured with good accuracy.

[Brief explanation of the drawing]

Fig. 1 shows an embodiment of the present invention (four composition diagrams, Fig. 2 is a configuration diagram showing a conventional example. 1... Beam, 2... Variable amount of transmitted light Member, 21... High transmittance region, 22...
Low transmittance area, 23° power boundary, 24...Reflective coating, 3...Movement means, 4...Photoelectric conversion means, 5...Auto Focus J1 Loser,
6...Lens, 7...Knifetsu member, 71...Transparent substrate, 72...-!
3. Light member, 73...Knife cover part, line bu L a

Claims (1)

[Claims] A variable amount of transmitted light member whose beam incidence surface has a uniform reflectance in two regions having different transmittances for the beam, and a variable amount of transmitted light such that the boundary between the two regions of the variable variable transmitted light member crosses the beam perpendicularly at a constant speed. A beam diameter measuring device comprising a moving means for moving the variable member, and a photoelectric conversion means for receiving and photoelectrically converting the beam transmitted through the variable transmitted light amount member.