JPS63155130A - Device for observing light wave front - Google Patents

Abstract

PURPOSE:To observe a light wave front in real time by providing a variable light delay system which adjusts the optical path length of a 1st or 2nd optical path to optional optical path length in a wave front optical path to be measured. CONSTITUTION:For example, respective parts of a flat plate 8 are irradiated at time points t1-t3 with the same light pulse generated by a pulse laser 1 at a time point 0. Light beams scattered by the flat plate 8 at the time points t1-t3 are passed through a half-mirror 9, converged by a lens 11, and incident on nonlinear crystal 12 in the order of t1' t2' t3'. When light beams passing through the 1st and 2nd optical paths I and II reach the nonlinear crystal 12 at the point t2', the light reflected by the flat plate at the time t2 and the light beams passing through the 1st and 2nd optical paths I and II cause phase conjugation light generation by degenerative four-light-wave mixing. At this time, the light beams passing through the 1st and 2nd optical paths I and II cause phase conjugation light generation by degenerative four-light-wave mixing. At this time, the optical path lengths of the 1st and 2nd optical paths I and II and the variable light delay system 13 are adjusted to adjust the optical path lengths to a little bit longer optical path length than before. Consequently, a light wave front can be observed in real time.

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.

(Prior art) In Abramson, Vol. 22, No. 2, pp. 215-232 (published February 15, 1983), Abramson describes the ability to record and reproduce holograms of optical wavefronts by using a coherent laser with an extremely short pulse width. It is reported that what has been done.

FIG. 10 is a schematic diagram showing a holographic 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.

By placing a dry plate on H and developing it, unlike a hologram, the light wave itself can be made It becomes possible to record and play.

That is, by using the light source, on H,
Of the light that has passed through A-E-D-B and A-C-B,
Their optical path lengths are within the coherent 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 has reached eQ on object 0 records interference fringes only on ho on H.

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

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 forming 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 11 shows the optical wavefront observed in this way,
This is a picture of how it is reflected by a mirror.

(Problems to be Solved by the Invention) The device described 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 pulsed light source, a nonlinear optical element, and a light pulse from the pulsed light source applied to the nonlinear optical element. a first optical path in which a light pulse from the pulsed light source is incident on the nonlinear optical element in the opposite direction with the same optical path length as the first optical path; ,
an optical element forming a wavefront to be measured; a reflecting surface tilted with respect to the optical axis of the optical path; a wavefront to be measured optical path that collects light reflected by the reflecting surface and enters the nonlinear optical element;
or a variable delay system that equally adjusts the optical path length of the second optical path and any optical path length in the measured wavefront optical path; The pulsed light that has passed through the optical fiber is simultaneously incident on the nonlinear optical element, and the output optical system separates and extracts phase co-projected light and projects it onto a screen.

The variable delay system can be inserted commonly into the first and second optical paths, and configured to adjust the lengths of each optical path simultaneously.

As the nonlinear optical element, a barium titanate crystal or a dye thin film such as eosin Y can be used.

The screen can be used as a fluorescent surface to observe a fluorescent image of a wavefront.

The screen may be an incident surface of the image tube, and may be configured to observe a wavefront based on an output image or an output signal of the image tube.

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

FIG. 1 is a plan view showing an embodiment of an apparatus for observing a light wavefront according to the present invention.

An extremely short-duration pulse generated from an ultra-short pulse light source 1 is split by a beam splitter 2 into a set of a first optical path I and a second optical path (3) and a measured wavefront optical path (rV).

As the pulsed light source 1, a CPM ring dye laser is used. This laser provides a 100 femtosecond pulse.

The pulse reflected by the beam splinter 2 and incident on the side of the set of the first optical path I and the second optical path (2) is made incident on the variable optical delay system 13 that can change the optical path length.

The pulse that has passed through the variable optical delay system 13 is further branched into a first optical path I and a second optical path (2) by a half mirror 4.

The optical pulse reflected by the half mirror 4 is reflected by the mirror 5 disposed on the first optical path I, and is passed through the nonlinear optical element 12.
is made incident on.

The light transmitted through the half mirror 4 is reflected by the mirror 6 disposed in the second optical path (2) and is made incident on the nonlinear optical element 12 in the opposite direction to the light in the optical path I.

Nonlinear optical element 12 is arranged between mirror 5 and mirror 6.

The nonlinear optical element 1 passes through the optical path ■ from the half mirror 4
2 and the distance from the half mirror 4 to the nonlinear optical element 12 via the optical path (2) are made equal.

If the optical path lengths of the optical path (1) and the optical path (2) are equal and the light can be made to enter the nonlinear optical element 12 from opposite directions,
The shape of the triangular mirror arrangement formed by the half mirror 4 and the mirror 5.6 can be any shape.

Barium titanate (BaTi) is used as the nonlinear optical element I2.
03) Use crystals. A dye thin film (such as Eosin Y) can also be used.

In this specification, the first optical path I and the second optical path (2) are defined as follows.

First optical path I (beam splinter 2 - variable optical delay system 1
3-Mirror 3-Half mirror 4-Mirror 5-Nonlinear optical element 12) Second optical path (Beam splitter 2-Variable optical delay system 13)
-Mirror 3-Half mirror 4-Mirror 6-Nonlinear optical element 12) The extremely short-duration light pulse transmitted through the beam splitter 2 is made incident on the nonlinear optical element 12 via the measured wavefront optical path (2) described below. .

The measured wavefront optical path (■) is defined as follows. Wavefront to be measured Optical path I[(Mirror 7 - Concave lens 15 - Flat plate 8 - Half mirror 9 - Lens 11 - Nonlinear optical element In this embodiment, the concave lens 15 is a wavefront changing element that forms the wavefront to be measured.

The plane plate 8 placed in the measured wavefront optical path (2) forms a diffuse reflection surface.

This measured wavefront optical path (1) is widened at one end by the concave lens 15, and a flat plate 8 is arranged at an angle with respect to the optical axis.
, it will include various optical path lengths.

Among these, only when there is light that has followed the same length of the optical path as the first optical path (■) and the second optical path (■) and entered the nonlinear optical element 12, this light and the total (phase conjugate wave propagating in the opposite direction) are detected. is generated.

As mentioned above, the phase conjugate wave is generated only for light that reaches the nonlinear optical element 12 at the same timing as the optical pulse that reaches the nonlinear optical element 12 through the first and second optical paths ■ and optical path ■. be.

The phase conjugate wave is reflected by the half mirror 9 and projected onto the screen 10, projecting an image of the optical wavefront onto the screen in real time.

Here, generation of phase co-projection by degenerate four-wave mixing will be explained with reference to FIG.

As described above, the optical path lengths of the first optical path (2) and the second optical path (2) are equal, and the optical pulses generated from the pulsed laser 1 follow the respective optical paths and enter the nonlinear optical element 12 from opposite directions at the same time.

The light pulses from the same light source that have passed through the measured wavefront optical path (2) are incident, and the light pulses that are incident at the same time cause the nonlinear optical element 12 to be affected by the light that has entered from the first and second optical paths.
A phase co-projected beam is generated which is reflected by a transient diffraction grating generated within the optical path (2) and propagates in the direction completely opposite to the optical path (2), and is sent into the optical path (3) to form a specific light wave image on the screen 10.

In this embodiment, it is assumed that the optical path (2) is formed by the following path.

Nonlinear optical element 12 - lens 11 - half mirror 9 - screen 10 Next, the operation of the above embodiment will be explained.

The light pulse that has passed through the beam splitter 2 is passed through the concave lens 15.
The light is magnified by the light beam, and is made obliquely incident on the flat plate 8, where it is scattered.

An extremely short single light pulse irradiates a portion of the flat plate 8 close to the lens 11 and gradually irradiates a portion further away from the lens 11, so the time at which the flat plate 8 is irradiated differs depending on the location.

FIG. 3 is a schematic diagram showing the position where the planar plate is illuminated at a particular time.

Now, the same optical pulse generated by pulse laser 1 at time 0 causes time t1. t2. Assume that each part of the plane Fi8 is irradiated at t3 as shown in the figure. The left side of Figure 3 is the concave lens 15.
It is close to .

t,, t2+ t3 (however, t1→t2=t+
), the light scattered by the plane plate 8 passes through the half mirror 9 and is focused by the lens 11, and the nonlinear crystal 1
2 (tl t-t2 "-t31).

At the time tl　l, the first and second optical paths ■.

Suppose that the light that has passed through (2) reaches the nonlinear crystal 12, then at time t1, the light reflected by the plane plate and the light that has passed through the first and second optical paths I and II cause the aforementioned degeneracy 4. Phase co-projection occurs due to light wave mixing.

The phase-co-projected light passes through the aforementioned optical path (2) and reaches the screen 10 at time tl'. Under the above-mentioned conditions, as shown in FIG.
) appears.

In FIG. 4, the left side is closer to the plane plate 8, and is an example observed from the half mirror 9 side.

At this time, z(tl Tf) is displayed on the screen 10.
No other wavefront images appear.

At time t2', the first and second optical paths 1. When the light that has passed through If reaches the nonlinear crystal 12, the light reflected by the plane plate at time t2 and the light that has passed through the first and second optical paths I and ff cause the aforementioned degenerate four-wave mixing. The occurrence of phase co-projection occurs.

At this time, the first and second optical paths I, the ItO optical path lengths,
By adjusting the variable optical delay system 13, it is adjusted to be slightly longer than in the previous case.

The variable optical delay system 13 can be placed in the measured wavefront optical path (2), for example between the beam splinter 2 and the mirror 7, to provide the same effect.

The phase-co-projected light passes through the optical path (3) described above and reaches the screen 10 at the time t2°, and the screen 10 shown in FIG.
An image of the wavefront shown at β (t2 Tf) appears.

Similarly, at time t3°, the light that has passed through the first and second optical paths ■ and ■ enters the nonlinear crystal 12.
If it reaches t3 g+, screen 10
An image of the wavefront shown at l (t311) appears.

As shown in Figure 1, since the plane plate is installed at an angle of θ with respect to the central optical axis of the light that has passed through the beam splinter 2, it is perpendicular to the optical axis of the phase-coincident light reflected by the half mirror 9. A light wavefront cut by a plane tilted by θ is reproduced on the screen 10, which is tilted by θ.

In the embodiment described in detail above, the optical wavefront can be observed in real time.

However, in order to know the overall optical characteristics of the wavefront deflection optical element (for example, the concave lens 15) from this light wavefront,
It is necessary to perform beam scanning and move the concave lens.

Next, with reference to FIGS. 5 to 9, an embodiment will be described in which, for example, a light wavefront changed by the entire concave lens is observed.

First, as shown in FIG. 5, the beam expander 16 is inserted between the mirror 7 and the flat plate 8 of the apparatus previously explained in FIG.

The wavefront observed at this time becomes as shown in FIG. 6 by adjusting the variable delay system in the same manner as in the embodiment described above.

After completing the above adjustment, as shown in FIG. 7, a concave lens 17, which is a wavefront deflection optical element, is inserted between the beam expander 16 and the sub-plane 8 to adjust the variable delay system.

Thereby, the light wavefront after passing through the entire concave lens 17 can be observed.

FIG. 8 shows a wavefront appearing on the screen 10.

As shown in FIG. 8, a portion of the wavefront that does not pass through the concave lens also appears on the screen 10.

FIG. 9 is a schematic diagram showing the main parts of another embodiment of the apparatus for observing a light wavefront according to the present invention.

The basic configuration of this embodiment is the same as the embodiment shown in FIG.

If the mask 18 is placed between the beam expander 16 and the concave lens in accordance with the shape of the concave lens 7 that forms the wavefront to be measured, only the light wavefront that has passed through the concave lens 7 can be observed.

In the embodiments described above, the light wavefront is reproduced on the screen 10, but by using this screen as a fluorescent surface, the fluorescent image of the wavefront can be observed.

When using a single pulse of light, the screen is used as a fluorescent surface for a total of 1
You can project the screen using a 13-sized television camera and observe it by triggering it.

Note that a bright image can be observed by repeatedly operating a pulsed laser to generate a light pulse train and repeatedly exciting the fluorescent surface.

Further, it is possible to arrange an incident surface of a TI image tube, an image intensifier tube, or the like at the position of the screen so that the wavefront can be observed using an output image or an output signal.

(Effects of the Invention) As described in detail above, the apparatus for observing a light wavefront according to the present invention includes a pulsed light source, a nonlinear optical element, and a first system that makes a light pulse from the pulsed light source enter the nonlinear optical element. an optical path, a second optical path in which the optical pulse from the pulsed light source is incident on the nonlinear optical element in the opposite direction with the same optical path length as the first optical path, an element to be measured that changes the wavefront in the optical path, and a reflective surface tilted with respect to the optical axis; a measured wavefront optical path that condenses the light reflected by the reflective surface and enters the nonlinear optical element; an optical path length of the first or second optical path; a variable delay system that equally adjusts arbitrary optical path lengths in the measurement wavefront optical path; It consists of an output optical system that separates and extracts phase-coincident light beams that are simultaneously incident on the element and projects them onto a screen.

Therefore, real-time observation of a selected optical wavefront has become possible by adjusting the variable delay system.

When the optical wavefront can be observed in real time as described above, the optical characteristics (lens aberrations, etc.) of the element to be measured that changes the wavefront arranged in the optical path of the measured wavefront can be known in real time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an apparatus for observing a light wavefront according to the present invention. FIG. 2 is a schematic diagram for explaining the principle of degenerate four-wave mixing. FIG. 3 is a schematic diagram showing a cross-sectional image of a wavefront formed on a plane plate at a particular time. FIG. 4 is a schematic diagram showing an example of a reconstructed image (wavefront observation). FIG. 5 is a schematic diagram showing the main parts of another embodiment of the apparatus for observing a light wavefront according to the present invention. FIG. 6 is a schematic diagram showing an example of a reconstructed image (wavefront observation) observed with the apparatus shown in FIG. FIG. 7 is a schematic diagram showing an example of observing a wavefront formed by a concave lens using the apparatus according to the embodiment described above. FIG. 8 is a schematic diagram showing an example of a reconstructed image (wavefront observation) observed with the apparatus shown in FIG. 7. FIG. 9 is a schematic diagram showing the main parts of another embodiment of the apparatus for observing a light wavefront according to the present invention. FIG. 10 is a schematic diagram showing a holographic recording device for optical wavefronts. FIG. 11 is a diagram showing a light wavefront observed by the hologram recording device. l...Pulse light source 2...Beam splitter 3.5, 6.7...Mirror 4.9...Mirror 10...Screen 11...Lens 12...Nonlinear optical element 13...・Variable optical wavefront delay system 15.16...Concave lens 16...Beam expander 18...Mask Patent applicant Hamamatsu Photonics Co., Ltd. Representative Patent attorney Hisashi Inoro Figure 3 Figure 4 Figure 5 Figure 7 Figure 9 Procedural amendment January 27, 1986

Claims (6)

[Claims] (1) a pulsed light source, a nonlinear optical element, a first optical path for inputting the optical pulse from the pulsed light source into the nonlinear optical element, and a first optical path for inputting the optical pulse from the pulsed light source to the nonlinear optical element; a second optical path that is incident in the opposite direction with the same optical path length as the optical path; an optical element that changes the wavefront in the optical path to form a measured wavefront; a reflective surface tilted with respect to the optical axis of the optical path; a measured wavefront optical path that collects reflected light and enters the nonlinear optical element; and a variable variable that adjusts the optical path length of the first or second optical path and any optical path length in the measured wavefront optical path to be equal to each other. a delay system, and the first optical path;
Output optics that separates and extracts phase co-projected light that is generated when the pulsed light that has passed through an arbitrary optical path length in the second optical path and the measured wavefront optical path is simultaneously incident on the nonlinear optical element and projects it on a screen. A device that observes optical wavefronts constructed from systems. (2) The apparatus for observing a light wavefront according to claim 1, wherein the reflecting surface disposed in the optical path of the measured wavefront is a diffusing surface of a flat plate. (3) The apparatus for observing a light wavefront according to claim 1, wherein the variable delay system is inserted commonly into the first and second optical paths. (4) The nonlinear optical element is a barium titanate crystal or a dye thin film such as eosin Y.
A device for observing the optical wavefront described in Section 1. (5) The device for observing a light wavefront according to claim 1, wherein the screen is a fluorescent surface. (6) The device for observing a light wavefront according to claim 1, wherein the screen is an entrance surface of an image tube.