JPS6151248B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pulsed laser power monitoring device.

Pulsed lasers, especially narrow laser pulses with a pulse width of about 1 to 50 ns, are used for various measurements such as air pollution observation (laser radar) and plasma measurement, but the energy of the pulse itself used for measurement is Conventionally, there has been no ideal monitoring method, especially when the beam diameter is large and the energy distribution in the beam cross section is non-uniform, resulting in various difficulties. One method is to measure the energy of the pulses before and after the pulse used for measurement with a calorimeter to estimate the power of the laser pulse used for measurement.
However, with this method, if the repetition stability of the laser is poor, it becomes difficult to know the energy of the pulse itself used for measurement. There are several other methods, including those that make use of nonlinear optical phenomena, but in either case, the equipment is large and expensive, or the accuracy is poor, so there is no ideal method.

The present invention eliminates the above drawbacks, measures the energy value of a laser pulse with a narrow pulse width, a large beam diameter, and an uneven beam pattern using a relatively simple device, and measures most of the energy in the laser pulse. This provides a new method that can be used for other purposes such as measurement.

The power monitoring device according to the present invention includes a beam splitter that separates a small portion of laser pulse energy, a diffuser plate that spatially scatters the separated laser pulse light, and a high-speed response sensor that receives a portion of the scattered light. A photoelectric converter, an integrating circuit consisting of a resistor and a capacitor that integrates the output current of the photoelectric converter, a switch circuit that quickly connects and disconnects between the integrating circuit and the photoelectric converter, and a voltage charged in the capacitor. It consists of a high input impedance voltage detection circuit that detects the

According to the present invention, a small portion of the pulsed laser light can be averaged and made incident on the photoelectric converter, and the output of the photoelectric converter is charged to the capacitor and measured at its charging voltage, so that the original pulsed laser beam is It is possible to accurately measure the energy of a certain percentage of energy.

An embodiment of the present invention will be described in detail using the drawings.

In the figure, a laser pulse beam 1, such as a Q-switched chilby laser, is partially separated by a beam splitter 2. As shown in FIG. As an example of beam splitter 2, it is possible to simply use a glass plate with an anti-reflection coating. Of course, this beam splitter 2 can only be used to monitor the power of a laser with a wavelength that passes through glass, but for example, in the case of a ruby laser, it is made of ordinary optical glass with two layers of anti-reflection coating. It becomes a beam splitter with a moderate reflectance and negligible absorption. Now, the light extracted by the beam splitter 2 is spatially scattered by a diffuser plate 3 made of frosted glass, opal glass, etc., and a portion of the scattered light 4 enters a photoelectric converter 5 such as a PIN diode. . When using a PIN diode as the photoelectric converter 5, a bias power supply 6 is used. The output of the photoelectric converter 5 is a resistor 7 and a capacitor 8
The output of the photoelectric converter 5 is controlled by a high-speed switch 9, such as an analog switch using a FET or a diode bridge, which is well known to those skilled in the art. electrically connected. The voltage charged in the capacitor 8 is detected by a high input impedance voltage detection circuit 10 using an FET or the like, as is well known to those skilled in the art.

Since the laser pulse energy is monitored by the light extracted by the beam splitter, the remaining laser pulse energy can be used for other purposes such as measurement. Energy can be monitored. Furthermore, by using the diffuser plate 3, even if the diameter of the beam 1 is larger than the diameter of the light-receiving surface of the photoelectric converter 5, or even if the spatial energy distribution of the beam 1 is uneven, a certain proportion of light can be accurately transmitted. The laser beam 1 can be incident on the photoelectric converter 5.
energy can be accurately monitored. Furthermore, the integrating circuit including the resistor 7 and the capacitor 8 allows the energy to be measured almost unaffected by the laser pulse width. Furthermore, the charging voltage of the capacitor 8 can be accurately measured by the high-speed switch 9 and the high input impedance voltage detection circuit 10.

The present invention is not limited to the above embodiments, and the target laser may be any pulsed laser as long as it is within a wavelength range in which the power monitor, diffuser plate, and photoelectric converter function effectively. Furthermore, the materials of the beam splitter and the diffuser plate are not limited to those mentioned above. The photoelectric converter may be a phototube, a photomultiplier tube, etc., and the high speed switch and high input impedance voltage detection circuit may be of other methods than those described above.

[Brief explanation of the drawing]

The figure is a circuit diagram showing one embodiment of the present invention. 1... Pulse laser beam, 2... Beam splitter, 3... Diffusion plate, 5... Photoelectric converter, 7...
...Resistor, 8...Capacitor, 9...High speed switch, 10...High input impedance voltage detection circuit.

Claims (1)

[Claims] 1. A beam splitter that separates a portion of the pulsed laser beam, a diffuser plate that scatters the separated light, a photoelectric converter that receives a portion of the scattered light, and an output of the photoelectric converter. an integrating circuit consisting of a resistor and a capacitor that integrates current;
An energy monitor comprising: a high-speed switch that connects and disconnects the integrating circuit and the photoelectric converter at high speed; and a high-input impedance voltage detection circuit that detects the voltage charged in the capacitor of the integrating circuit. Device.