JPH0315709A - Contactless minute surface shape measuring instrument - Google Patents

Abstract

PURPOSE:To quickly measure a minute surface shape with high precision and contactlessly by transmitting the laser light between laser transmitter and receiver and a polarizing beam splitter. CONSTITUTION:The two-frequency laser light radiated from a two-frequency laser transmitter 1 passes a beam expander 10, a rod lens 11, a polarization plane holing optical fiber 12, and a rod lens 13 and is made incident on a polarizing beam splitter (BS) 3, and is divided into two frequency components. One laser light is returned to the BS 3 through a quarter-wave plate 4, a reflection mirror 6, and a wave plate 4. The other passes a quarter-wave plate 5 and an objective lens 7 and is reflected by an object 9 to be measured and is returned to the BS 3 through a wave plate 5. Signal light synthesized on the BS 3 passes a collimator lens 14, a multimode optical fiber 15, and a collimator lens 16 and is made incident on a laser receiver 2. When the object 9 to be measured is moved at right angles to the laser optical axis at such a time, the minute surface shape is measured by the heterodyne laser interference method.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a device for measuring the fine surface shape of precision-machined parts at high speed, with high precision, and in a non-contact manner. [Conventional technology] The surfaces of precision-machined parts have minute irregularities such as surface roughness and surface waviness. The shape of these irregularities is an important factor that affects the performance and function of parts, and the measurement results may be useful as reference data for the next processing or measurement, or as necessary data for commercial transactions. many. Therefore, high-speed, high-precision, non-contact measurement of surface microstructures is becoming an increasingly important issue due to demands for improving part processing efficiency and product quality. One method of measuring displacement without contact is the heterodyne laser interferometry displacement measurement method, which basically does not require sensitivity calibration and can perform extremely reliable measurements, so it is suitable for contact-type measuring instruments. It is expected to be used in the development and research of products that may cause scratches. Below, the displacement measurement method using the heterodyne laser interference method will be briefly explained with reference to FIG. In Figure 6,
Code 1 is a two-frequency laser transmitter, code 2 is a laser receiver,
3 is a polarizing beam splitter, 4.5 is a 174 wavelength plate, 6 is a reflecting mirror, 7 is an objective lens, and 9 is an object to be measured. Two frequencies fl. emitted from a laser oscillator l. f2
Since the Caesar light has polarization components that are orthogonal to each other, a polarization beam splitter 3 called an "interferometer" is used.
The laser beam of f2, which is split into two frequency components above, is sent to a reflecting mirror 6 fixed to the polarizing beam splitter 3, and the laser beam of fl is focused by an objective lens 7 and directed to the object to be measured 9. The light is projected onto the surface of the Both reflected lights are combined again on the polarizing beam splitter 3 to become signal light, which is photoelectrically converted by the laser receiver 2. At this time, when the object to be measured 9 is moved in the direction of the laser optical axis, a Doppler shift occurs in the reflected light depending on the amount of displacement of the object to be measured 9, and H becomes f.
The frequency changes to 1±Δfl. Therefore, the beat frequency of fl±Δfl−f2 is counted in the signal detected by the laser receiver 2, and the beat frequency f
It is compared with the beat frequency count of L-f2, and the amount of displacement corresponding to Δfl is displayed. [Problems to be solved by the invention] Nowadays, as machining technology becomes more precise, on-machine measurement that measures the workpiece without removing it from the processing machine, in-process measurement that measures the workpiece during processing, and even more There is now a need for an efficient production process in which the measurement results are fed back to the machining process, and all measurements and inspections are completed when the machining process is complete. This requires small, high-speed, and highly accurate measuring instruments. However, in conventional non-contact displacement measuring devices using heterodyne laser interference, the transmission of laser light is prevented by arranging the laser transmitter, receiver, and interferometer in a straight line, or by using reflectors, prisms, etc. Because of this, the adjustment is complicated, it is difficult to maintain a large distance between the laser transmitter and receiver, and the interferometer, and once the interferometer is installed, it cannot be easily removed or moved. There were problems such as. The present invention aims to miniaturize the device and allows the interferometer to move freely, thereby achieving a non-contact, high-speed,
It is possible to perform on-machine or in-process measurements on processing machines with high precision.The unique feature is that the laser light is transmitted between the printer and the printer via the end fiber. [Function] In the non-contact surface micro-shape measuring device configured as above, the laser beam is transmitted through the tip fiber, so only the interferometer part can be easily installed on other measuring machines or processing machines. This makes it possible to measure surface microstructures at high speed and with high precision in a non-contact manner. Additionally, attaching the laser receiver directly to the polarization beam splitter is effective in improving the transmission efficiency of laser light and reducing noise. [
Example] An example will be explained with reference to the drawings. In FIG. 1, two-frequency laser beams emitted from a two-frequency laser oscillator l are transmitted to a beam expander l0 to achieve the above object. The laser beam emitted from the output end side is
The laser beam enters the polarized beam splitter 3 via the laser transmitter 13, and is split into two frequency components by the receiver and the polarized beam splitter called an "interferometer". 4, is reflected by the reflecting mirror 6, passes through the 174 wavelength plate 4 again, and returns onto the polarizing beam splitter.The other laser beam passes through the 1/4 wavelength plate 5.
, is focused by the objective lens 7, is reflected on the surface of the object to be measured 9, passes through the L/4 wavelength plate 5, and returns onto the polarizing beam splitter. The signal destination synthesized on the polarizing beam splitter 3 enters the multimode destination fiber 15 via the collimator lens 14, and the laser beam emitted from the output end passes through the collimator lens 16 and enters the laser receiver 2. is incident on . At this time, if the object to be measured 9 fixed on the moving table 8 is moved in a direction perpendicular to the laser optical axis, the fine surface shape of the object to be measured 9 can be measured by heterodyne laser interferometry. Figure 3 shows the results of a comparison between the measured value of the precision length measuring machine and the measured value of this measuring device when From FIG. 3, it can be seen that the measured values change linearly in the range of 0 to lWII+.

Claims (1)

[Claims] 1) A dual-frequency laser transmitter, a laser receiver, a polarizing beam splitter, one optical fiber, and the other optical fiber, and the polarizing beam splitter includes one quarter-wave plate and the other optical fiber. A quarter-wave plate, a reflecting mirror, and an objective lens are fixed, and the light beam emitted from the two-frequency laser oscillator is made incident on the polarizing beam splitter via the one optical fiber to be split into two frequency components. , one of the divided luminous fluxes is reflected by the reflecting mirror through one of the quarter wavelength plates, and the other of the divided luminous fluxes is reflected by the other one of the divided luminous fluxes.
reflected on the surface to be measured through the /4 wavelength plate and the objective lens, the one reflected light beam and the other reflected light beam are combined on the polarizing beam splitter, and the combined light beam is transmitted through the other optical fiber. 2) A non-contact surface micro-shape measuring device using a heterodyne laser interference method, characterized in that the combined light beam is made to enter the laser receiver directly. Described non-contact surface micro-shape measuring device