JPS63175730A - Observing device for light wave plane - Google Patents

Abstract

PURPOSE:To observe the wave front of a single pulse of a pulse laser in real time by providing the pulse laser, a streak camera, a trigger system which operates the camera, and an optical system which forms an image of a reflecting plate projected with laser light on the photoelectric cathode of the streak camera. CONSTITUTION:When a CPM ring coloring matter laser is used as the pulse laser 1, short light pulses of about 100 femtoseconds in pulse width are obtained. The streak camera 3 is a camera for fast development photography to which a streak tube is applied, and the streak tube has a deflection electrode provided in the converging lens of an image tube and runs an output image by applying a deflection voltage to the electrode. This deflection voltage synchronizes with the generating operation of a single pulse of the pulse laser 1 and is operated with a trigger signal generated by the trigger system 4. The single pulse generated by the pulse laser 1 is spread partially by a half-mirror 11 and guided to the trigger system 4, which generates the trigger pulse. The pulse transmitted through the mirror 11 is reflected by a mirror 12 toward a reflecting plate 2.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a device for observing a light wavefront in real time using a streak camera and a pulse laser.

(Prior art) In Applied Optics, Vol. 22, No. 2, pp. 215-232 (published February 15, 1983), Mr. Abramson describes the method of changing the optical wavefront by using a coherent laser with an extremely short pulse width or a laser with a short coherence length. It has been reported that hologram recording has been made.

FIG. 9 is a schematic diagram showing a hologram recording device for optical wavefronts.

A part of the light emitted from the laser L passes through A-C-B to form an object light.

Further, the light from the laser L that passes through A-E-D-B forms a reference light.

In this way, interference fringes between the object beam and the reference beam are formed on the recording surface H.

A hologram is created by placing a dry plate on H and developing it. At this time, unlike ordinary holograms, it is possible to record and reproduce the light wave itself by using a light source with a short coherence length or a short pulse light source as the laser L, and using a door painted with white paint as the object 0. Become.

That is, by using the light source, on H,
Of the light that has passed through A-E-D-B and A-C-B,
The optical path lengths of each other are within the coherence length.

Alternatively, only interference fringes are formed between lights that are equal within the pulse width, and interference fringes between lights that have different optical path lengths are not formed.

More specifically, the object light that reaches eo on object O records interference fringes only on ho on H.

Similarly, the object beams reaching el and e2 are respectively hl.

Interference fringes will be recorded only in h2.

When the hologram thus created is irradiated with only the reference light, the reference light is diffracted by the interference fringes recorded on each part of the hologram H, and the light that formed the interference fringes is reproduced.

Therefore, at this time, when the observation point is changed along H, the optical wavefront can be observed as shown in FIG.

Figure 10 shows the optical wavefront observed in this way,
This is a picture of how it is reflected by a mirror.

(Problems with the Prior Art) The device shown in the academic journal uses hologram technology and cannot observe wavefronts in real time.

An object of the present invention is to provide an apparatus for observing a light wavefront that can observe a light wavefront in real time.

(Means for Solving the Problems) In order to achieve the above object, an apparatus for observing a light wavefront according to the present invention includes a pulse laser, a streak camera, and an operation of the streak camera in synchronization with the operation of the pulse laser. a trigger system that causes the pulsed laser beam to be projected onto the photocathode of the streak camera; It consists of an optical system that

The reflector may be a flat diffuse reflector.

(Example) The present invention will be explained in more detail with reference to the drawings and the like.

FIG. 1 is a plan view of the main parts of a first embodiment of an apparatus for observing a light wavefront according to the present invention, and FIG. 2 is a side view of the main parts of the apparatus of the embodiment.

As the pulse laser 1, a CPM ring dye laser is used.

According to this, a short optical pulse with a pulse width of about 100 femtoseconds can be obtained. - Streak Camera 3 is a camera for high-speed phenomenon photography that uses a streak tube.

In a streak tube, a deflection electrode is provided within the focusing lens of an image tube, and a deflection voltage (single sweep) is applied to this electrode to cause an output image to run.

This deflection voltage is operated by a trigger signal generated by a trigger system 4 in synchronization with the single pulse generation operation of the pulsed laser 1.

A single pulse generated by the pulsed laser 1 is partially separated by a nof mirror 11 and guided to a trigger system 4, where a trigger pulse is generated. Said/%-Fumirar 11
The pulses transmitted through the streak camera 3 are reflected toward the reflecting plate 2 by a mirror 12 (see FIG. 2) provided above the incident surface of the streak camera 3.

A flat diffuse reflection surface is used as the reflection plate 2.

A cylindrical lens 14 having a concave cross section is arranged between the mirror 12 and the reflecting plate, and the light beam is expanded and irradiated onto the reflecting plate 2.

The image of the reflection plate 2 irradiated with the laser beam is formed on the photocathode of the streak camera 3 by the imaging lens 13.

A line portion of the plane plate 2 coaxial with the entrance slit of the streak camera 3 is imaged onto the slit of the streak camera 3 by an imaging lens 3.

At this time, the distance between the imaging lens 13 and the flat plate 2 is L,
If the image-side focal length of the imaging lens 13 is f and the length of the entrance slit is So, then the light wavefront can be observed with respect to the information on the length S of the line on the plane plate.

However, S = (L - f) S o / f.

The light reflected by the half mirror 11 enters the trigger system 4 and is swept in synchronization with the streak sweep timing.

The obtained streak image is observed by a measurement television camera 5 and an analysis device 6.

The reflector plate 2 is installed exactly parallel to the photocathode surface of the streak camera 3, and information on the light wavefront is scattered by the plane plate 9. It will be converted into information and observed.

Next, with reference to FIG. 3, the streak image observed in the above embodiment will be explained.

As shown in FIG. 1, if a cylindrical lens 14 with a concave cross section is placed in the middle of the optical path of the laser beam, it will be reflected! Light reaches the central part of Fi2 at a high speed, and the end parts arrive relatively slowly compared to the central part.

Therefore, as shown in Figure 3, the left and right sides of the center are Δ
A streak image that appears with a delay of t is obtained.

Based on the temporal resolution of the streak camera at this time, it is possible to observe the wavefront of the optical pulse that has reached the reflector.

At this time, as shown in Figure 2, the information is not on the axis connecting the input slit and the field of view of the plane plate, but on the plane that includes the observed line of the plane plate, which forms an angle θ with the plane plate, that is, the optical axis. Information on the wavefront of the included plane can be obtained.

The embodiment device further includes a streak camera 3;
By moving the imaging lens 13 up and down as a unit, it becomes possible to three-dimensionally observe the light wavefront at the position of the flat plate of light spread by a concave lens or the like.

FIG. 4 is a schematic diagram showing a second embodiment of an apparatus for observing optical wavefronts according to the present invention.

An ultrashort pulse wavefront is irradiated onto the reflecting plate 2 from an oblique direction through a cylindrical lens 14 having a concave cross section, and an image of the reflecting plate 2 is formed on the surface of the streak tube 3 by a lens 13 for observation. It is something.

With the above device, it is possible to observe optical wavefronts in real time. The surface accuracy of the optical element can be measured from this light wavefront. In the previous embodiments, it is possible to observe the optical wavefront when a light beam passes through a part of the optical element, but for the entire optical element, it is necessary to scan the beam or move the optical element. . Therefore, it is possible to observe the light wavefront when it passes through the entire optical element at once in the following manner.

FIG. 5 is a side view of the main parts of a third embodiment of an apparatus for observing optical wavefronts according to the present invention.

A beam expander 15 is arranged between the mirror 12 and the reflection plate 2.

The laser beam is expanded and becomes parallel light, which reaches the reflecting plate 2.

Other configurations are the same as those of the previously described embodiments.

The streak image at this time is as shown in FIG.

FIG. 7 is a layout diagram showing an example of measurement of the convex lens 16 using the third embodiment apparatus shown in FIG.

As shown in FIG. 7, the beam expander 15 of this system
A convex lens 16, which is an object to be observed, is inserted between the reflector 2 and the reflector 2.

At this time, the distance between the convex lens 16 and the reflecting plate 2 is
If the focal length is less than or equal to the focal length of the convex lens 16, a light wavefront that is being focused by the convex lens 16 is observed, and if the focal length is greater than or equal to the focal length, a light wavefront that is once focused and then diverging is observed.

FIG. 8 shows an example of observation of a light wavefront by the apparatus of the third embodiment. Both ends are portions that did not pass through the convex lens 16, and correspond to both ends in FIG. Note that this part can be cut using an aperture or the like.

(Effects of the Invention) As described in detail above, the device for observing a light wavefront according to the present invention includes a pulse laser, a streak camera, and a trigger system that operates the streak camera in synchronization with the operation of the pulse laser. Consisting of a reflector on which the light pulse of the pulsed laser is projected via an element forming an observed wavefront, and an optical system that forms an image of the reflector illuminated by the laser beam onto the photocathode of the streak camera. has been done.

Therefore, the wavefront of a single pulse of the pulsed laser projected onto the reflector can be observed in real time.

By adjusting the formed optical image and the signal of the reflector,
A streak image with an appropriate magnification can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a plan view of the main parts of a first embodiment of an apparatus for observing a light wavefront according to the present invention. FIG. 2 is a side view of the main parts of the apparatus of the embodiment. FIG. 3 is a schematic diagram showing an image of a wavefront observed by the apparatus of the embodiment. FIG. 4 is a plan view showing the relationship between the streak camera of the second embodiment and the incident wavefront. FIG. 5 is a side view of the main parts of a third embodiment of an apparatus for observing optical wavefronts according to the present invention. FIG. 6 is a schematic diagram showing an image of a wavefront observed by the apparatus of the embodiment. FIG. 7 is a side view showing an example in which a wavefront formed by a convex lens inserted into an optical path is measured by the third embodiment apparatus for observing the optical wavefront shown in FIG. FIG. 8 is a schematic diagram showing an image of the observed wavefront affected by the convex lens. FIG. 9 is a schematic diagram showing a hologram recording device for optical wavefronts. FIG. 10 is a diagram showing a light wavefront observed by the hologram recording device. 1... Pulse laser 2... Reflection plate (flat plate-like diffuse reflection surface) 3... Streak camera 4... Trigger system of streak camera 5... Television camera 6... Analysis device 11. ...Half mirror 12...Mirror 13...Imaging lens 14...Cylindrical lens 15...Beam expander 16...Convex lens Patent applicant Hamamatsu Photonics Co., Ltd. Agent Patent attorney Hisada Inoro Figure 3 Figure 5 Figure 7

Claims (2)

[Claims] (1) A pulse laser, a streak camera, a trigger system that operates the streak camera in synchronization with the operation of the pulse laser, and a light pulse of the pulse laser is projected via an element forming an observed wavefront. A device for observing a light wavefront, comprising a reflector and an optical system that forms an image of the reflector irradiated by the laser beam onto a photocathode of the streak camera. (2) The apparatus for observing a light wavefront according to claim 1, wherein the reflecting plate is a flat diffuse reflecting plate.