JPH0430484Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a movement measuring device having a measuring mechanism using optical interference.

[Prior Art] Precise measurement is required for devices that measure the amount of movement of a stage such as a charged beam lithography device.
It is equipped with a laser interferometer that uses optical interference.

FIG. 4 shows a simple example of such a device. In the figure, reference numeral 1 denotes a moving body such as a stage, which is moved as appropriate by a moving drive mechanism (not shown).
2 is a reflecting mirror fixed to the moving body, 3 is a laser light source, 4 is a semi-transparent mirror whose mirror surface is approximately 45 degrees with respect to the incident light;
Reference numeral 5 designates a reference reflecting mirror whose mirror surface is fixed perpendicular to the incident light, 6 a magnifying lens, 7 a light receiver, 8 a measurement circuit, 9 a register, and 10 a display. In such a device, light from a light source 3 passes through a semi-transparent mirror 4.
The light is split into two different optical paths and is reflected by mirrors 2 and 5. The two reflected lights cause interference fringes to appear on the surface of the semi-transparent mirror 4, and the interference fringes appear on the lens 6.
The detected signal from the light receiver 7 enters the measurement circuit 8. The measuring circuit generates a pulse signal corresponding to the brightness and darkness of the interference fringes every time the moving object 1 moves a distance of half a wavelength, and counts it.The counting signal from the circuit 8 is input to the register 9, The contents of the register are displayed by the display 10. This displayed value is the moving distance of the moving object.

Now, as the measurement circuit mentioned above, one that converts the optical interference signal into a pulse signal at an appropriate speed and with an appropriate resolution (accuracy) is selected. The conversion speed is slow; conversely, the faster the conversion speed, the lower the resolution. Therefore, if you use a low-speed high-resolution measurement circuit,
When the moving body is moving at low speed, the amount of movement can be measured with high accuracy, but when the moving body is moving at high speed, it is impossible to measure the amount of movement. Furthermore, if a high-speed, low-resolution amount measuring circuit is used, it can be measured when the moving body is moving at high speed, but the amount of movement cannot be measured with high precision.

[Problems to be solved by the invention] For example, when moving the stage of the above-mentioned charged beam lithography apparatus, etc., when moving the stage over a long distance, it is moved at high speed from the start of the movement until near the stop, and then stopped near the end. Move at low speed until
The aim is to shorten travel time and increase precision in stopping at a predetermined position. In such a case, if a low-speed, high-resolution measurement circuit is used, measurement cannot be performed while the moving object is moving at high speed, so measurement cannot be performed.

In addition, in such cases, if a high-speed, low-resolution amount measurement circuit is used, it is possible to measure when the moving object is moving at high speed, but when the moving object starts moving at low speed near a stop, the amount of movement can be increased. Since it cannot be measured accurately, it is not possible to draw at high speed and with high precision as a result.

The present invention is aimed at solving such problems.

[Means for Solving the Problems] Therefore, the movement measuring device of the present invention uses a high-speed low-resolution measuring circuit as a measuring circuit that generates a pulse signal based on an optical interference signal generated by the movement of a moving object. A low-speed high-resolution measurement circuit is prepared, an upper bit register that operates independently of the output pulse of the high-speed low-resolution measurement circuit and the output pulse of the low-speed high-resolution measurement circuit, and a reset state is established by the output pulse of the high-speed low-resolution measurement circuit. The amount of movement of the moving object is determined by adding the contents of both registers to the lower bit register.

[Embodiment] FIG. 1 is a schematic diagram of a movement amount measuring device showing an embodiment of the present invention.

Components in the figure denoted by the same numbers as those used in FIG. 4 are the same components.

8A and 8B are a high-speed low-resolution measurement circuit and a low-speed high-resolution measurement circuit, respectively. The high-speed low-resolution measurement circuit generates a pulse signal every λ/4 (λ is the wavelength of the optical interference signal) of the optical interference signal from the optical receiver 7, for example. In addition, low-speed high-resolution measurement circuit 8
B starts its operation by the first pulse signal from the high-speed low-resolution measurement circuit 8A, and generates a pulse signal every λ/64 of the optical interference signal from the light receiver 7, for example. For example, 90 is an 8-bit register, and the lower beam portion 9 from 1 bit to 4 bits.
It consists of 0B and upper bit part 90A from 5 bits to 8 bits, and each part operates independently. A pulse signal from the high-speed low-resolution measuring circuit 8A is input to the upper bit portion 90A.
The lower bit portion 90B is reset by each pulse signal from the high-speed low-resolution measuring circuit 8A, and receives the pulse signal from the low-speed high-resolution measuring circuit 8B. 10 displays the contents of the upper bit part 90A and lower bit part 90B as the contents of one register.

In such a device, the case where the moving body 1 is moved at high speed by, for example, moving the moving body 1 at high speed from the start of the movement until almost stopping, and then moving at low speed from near the end until it stops, is as follows. Explain.

The movable body 1 is moved at high speed by a moving drive mechanism (not shown) from the start of movement until almost stopping. Due to the high-speed movement, an optical interference signal as shown in FIG. 2a passes through the light receiver 7 and enters the high-speed low-resolution measurement circuit 8A and the low-speed high-resolution measurement circuit 8B. The high-speed low-resolution measurement circuit 8A generates a pulse signal every λ/4 of the optical interference signal, as shown in FIG. 2b. Furthermore, although the low-speed high-resolution measurement circuit 8B starts operating with the first pulse signal from the high-speed low-resolution measurement circuit 8A, the frequency of the optical interference signal is high and it is not possible to generate a pulse signal during each cycle. The pulse signal from the high-speed low-resolution measuring circuit 8A is input to the upper bit portion 90A of the register 90.

Next, the movable body 1 is moved at a low speed by a moving drive mechanism (not shown) from near the end of its movement until it stops. Due to the low-speed movement, an optical interference signal as shown in FIG. 3a passes through the light receiver 7 and enters the high-speed, low-resolution measurement circuit 8A and the low-speed, high-resolution measurement circuit 8B. The high-speed low-resolution measurement circuit 8A generates a pulse signal every λ/4 of the optical interference signal, as shown in FIG. 3b. Further, the low-speed high-resolution measuring circuit 8B starts operating with the first pulse signal from the high-speed low-resolution measuring circuit 8A, and as shown in FIG. A pulse signal is generated every time. Note that the low-speed, high-resolution measurement circuit 8B starts operating with the first pulse signal from the high-speed, low-resolution measurement circuit 8A, so when the high-speed, low-resolution measurement circuit 8A generates a pulse signal, it does not generate a pulse at the same time. , a pulse is generated later than the above pulse. The pulse signal from the high-speed low-resolution measurement circuit 8A is input to the upper bit portion 90A of the register 90. Further, the pulse signal from the low-speed high-resolution measurement circuit 8B is sent to the register 90.
is input to the lower bit portion 90B of. On this occasion,
Since the lower bit portion 90B enters a reset state every time a pulse signal is input from the high-speed low-resolution measurement circuit 8A, the low-speed high-resolution measurement circuit 8B is reset between the pulse signal from the high-speed low-resolution measurement circuit 8A. Holds the pulse signal length input from Therefore, the upper bit portion 90A holds the number of pulses corresponding to the distance traveled by the moving body 1 from high-speed movement to low-speed movement until it approaches a stop. Po in FIG. 3b is the last input pulse. Also, the lower bit part 90B
, the number of pulses (Pa in FIG. 3c) corresponding to the distance traveled by the moving body 1 immediately before stopping is held. As a result, the display 10 shows the upper bit part 9.
Since the sum of the contents of 0A and the contents of the lower bit portion 90B is displayed, the moving distance of the moving object is measured with the resolution of the low-speed high-resolution measurement circuit 8B. This means that the measurement was performed at a high speed approximately equal to the speed of the high-speed low-resolution measurement circuit 8A.

In this embodiment, it consists of a lower bit part 90B from 1 bit to 4 bits and an upper bit part 90A from 5 bits to 8 bits, and each part is one 8-bit register 9 that operates independently.
Although 0 is provided, completely separate lower bit registers from 1 bit to 4 bits and upper bit registers from 5 bits to 8 bits may be provided.

[Effect of the invention] The present invention provides a high-speed, low-resolution measurement circuit and a low-speed, high-resolution measurement circuit. The output pulse of the resolution measurement circuit is used to enter the lower bit register which is reset, and the sum of these two registers is used as the amount of movement of the moving object, so the moving object is moved at high speed from the start of movement until it nearly stops, and from near the end until it stops. When moving at a low speed, the moving distance of the moving object is measured at high resolution by the low speed, high resolution measurement circuit, and at a high speed approximately close to the speed of the high speed, low resolution measurement circuit.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a movement measuring device showing an embodiment of the present invention, FIGS. 2 and 3 are signal waveform diagrams to supplement the explanation of the operation of the device of the present invention, and FIG. FIG. 2 is a schematic diagram of a conventional movement measuring device. 1... Moving object, 2... Reflecting mirror, 3... Laser light source, 4... Semi-transparent mirror, 5... Reference reflecting mirror, 6...
Magnifying lens, 7... Light receiver, 8... Measurement circuit, 1
0... Display, 8A... High speed low resolution measurement circuit,
8B...Low-speed high-resolution measurement circuit, 90...Register, 90A...Upper bit part, 90B...Lower bit part.

Claims (1)

[Scope of utility model registration request] In a device that measures the amount of movement of a moving object using a measurement mechanism that uses optical interference, a high-speed, low-resolution measurement circuit and a low-speed measurement circuit are used as measurement circuits that generate pulse signals based on optical interference signals generated by the movement of the moving object. A high-resolution measurement circuit is prepared, and an upper bit register that operates independently of the output pulse of the high-speed low-resolution measurement circuit and the output pulse of the low-speed high-resolution measurement circuit, and is brought into a reset state by the output pulse of the high-speed low-resolution measurement circuit. A moving amount measuring device characterized in that the moving amount is stored in a lower bit register, and the sum of the contents of both registers is used as the moving amount of the moving object.