JPS6114015Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for arbitrarily setting the cross-sectional shape of a light beam, such as a laser beam, when the light beam is used for displaying or recording information.

Display and recording devices that use laser beams can make the beam narrow regardless of brightness, so they can obtain very high-resolution images, but if you scan with a narrow beam to increase the resolution, the horizontal resolution image will be lower. However, if the number of scanning lines is limited, the vertical resolution image is determined by the number of scanning lines, and in relation to the screen size, there are gaps between the scanning lines, resulting in a "blind-like" image. In order to avoid this, the horizontal size of the scanning beam should remain the same, and only the vertical size should be made thick enough to fill the gaps between the scanning lines. That is, the cross-sectional shape of the scanning spot may be a vertical ellipse.

First, an example of the configuration of a television image recording apparatus using a laser beam is shown in FIG. 1, and an outline of its operation will be described below. In FIG. 1, a laser beam 9 from a laser oscillator 1 is intensity-modulated by an optical modulator 2 (for example, an ultrasonic optical modulator) according to an input signal 8 from a television camera, and a laser beam 9 incident on a first optical deflector 10 is intensity-modulated according to an input signal 8 from a television camera. becomes. Next, the intensity-modulated laser beam 10 is deflected in the left-right direction by a first optical deflector 3 (for example, a rotating polygon mirror) to become a beam 11, and the beam 12 that has passed through the relay lens system 4 is
The beam is deflected in the vertical direction by a light deflector 5 (for example, a galvanometer), resulting in a beam 13 that is two-dimensionally deflected horizontally and vertically. This beam 13 passes through an imaging optical system 6 and an imaging beam 14
Then, a raster is formed on the recording medium 7 (for example, 16 mm color film).

Next, a second example of the configuration of an optical system used in a television image recording device using the laser beam will be described.
It is shown in the figure and its functions will be explained in detail. FIGS. 2a and 2b are views respectively seen from a direction perpendicular to a plane containing the deflection direction of the first optical deflector (3 in FIG. 1) and an optical axis of the lens and from a horizontal direction. The incident light beam 23 may be monochromatic or a plurality of overlapping beams such as red, green, blue, etc., but it is handled as a parallel light beam. The incident light beam 23 passes through the first cylindrical lens 15 and becomes a focused beam 10, which is focused at a position corresponding to the focal length _C1 of the first cylindrical lens 15. In this case, since 15 is a cylindrical lens, the beam is focused only in the vertical direction.
The focal point of the beam is the deflection surface 16 of the first optical deflector, where the beam 1 deflected in the left and right direction is
1 and enters the first relay lens 17. The position of the first relay lens 17 is the first optical deflector deflection surface 16
The focal length of the first relay lens 17 is ₁ apart from the first relay lens 17 . This beam then passes through a second cylindrical lens 18 and is focused onto a first focusing surface 19 . The position of the first focusing surface 19 is from the first relay lens 17 to the focal length ₁ of the first relay lens 17.
It is also located at a distance from the second cylindrical lens 18 by the focal length _C2 of the second cylindrical lens 18. The first relay lens 17 and the second cylindrical lens 18 are arranged such that the vertical and horizontal focal points of the light beam coincide. The light beam that has passed through the first focusing surface 19 is directed to the second relay lens 2.
0 and enters the second optical deflector (only the deflection surface 21 of the second optical deflector is shown in FIG. 2). The second relay lens 20 is located at a distance of ₂ focal lengths of the second relay lens 20 from the first focusing surface 19, and the second optical deflector deflection surface 21 is located at a distance of ₂ from the second relay lens 20. It is in. The light beam is vertically deflected at the second optical deflector deflection surface 21, resulting in a two-dimensionally deflected beam 13. Finally, the two-dimensionally deflected beam 13 is transmitted through the imaging lens 2
2 and becomes an imaging beam 14, forming a raster on the recording medium 7. The position of the imaging lens 22 is such that the focal length ₃ of the imaging lens 22 is away from the deflection surface 21 of the second optical deflector, and the recording medium 7 is located away from the imaging lens 22 by the focal length ₃ of the imaging lens 22. There is.

The configuration and function of the optical system of the television image recording apparatus using the laser beam have been explained above, but now let us consider the cross-sectional shape of the focused beam spot.

In FIG. 2, the first focusing surface 19 and the recording medium 7
Since they are connected only by spherical lenses, they are conjugate surfaces in both the vertical and horizontal directions. Therefore, in order to consider a point on the recording medium 7, the first focusing surface 19
It is sufficient to consider the above points.

In FIG. 2, if the incident light beam 23 has a Gaussian intensity distribution in cross-section, like a single transverse mode laser beam, the cross-section of the spot on the first focusing surface 19 will be circular. The condition is ₁ ² = _C1・_C2 . If it is necessary to make a vertically long or horizontally long elliptical beam with a cross-sectional shape of the spot, it is sufficient to use ₁ ² < _C1・_C2 or ₁ ² > _C1・_C2 . That is, in order to obtain an elliptical beam, it is sufficient to deviate from the condition that the spot cross section in the focusing plane is circular. However, the relationship between ₁ and _C2 needs to be determined so as to correct the pitch unevenness caused by the folding of the first optical deflector 3.

That is, when a rotating polygon mirror is used as the first optical deflector 3, if the rotating mirror is bent, a deflection component perpendicular to the original deflection direction is generated, which causes pitch unevenness in the scanning line. To prevent this, the deflection point 16 of the first optical deflector 3 and the first focusing surface 19
It is necessary to determine the relationship between ₁ and _C2 so that is the relationship between the object point and the image point, and ₁ and _C2 are usually considered to be fixed. Therefore, when changing the cross-sectional shape of the spot, a method is usually used to change _C1 . However, to change the cross-sectional shape of the spot using this method, it is necessary to change the focal length of the cylindrical lens, and to continuously obtain an arbitrary cross-sectional shape, it is necessary to use a cylindrical zoom lens. The drawback was that the lenses were extremely difficult to assemble and were expensive. Therefore, the present invention aims to eliminate such drawbacks and provide a device different from the conventional ones for continuously obtaining spots of arbitrary cross-sectional shapes.

FIG. 3 is a diagram showing the principle explanation and one embodiment of the present invention. Figure 3 a and b are Figure 2 a and b.
and b, respectively, as seen from the direction perpendicular to and horizontal to the plane containing the deflection direction of the first optical deflector and the optical axis of the lens. The first focusing surface 19 is a surface.
Only the previous one is shown. Fig. 3c shows an example of the cross-sectional shape of the beam corresponding to each part indicated by the numbers in Fig. 3a and b in the case of ₁ ² = _C1・_C2.The solid dotted line indicates the cylindrical lens 15, This corresponds to the case where they are inserted at the 15' position.

The arrangement and function of the elements of the optical system in FIG. 3 are almost the same as those shown in FIG.
3 passes through the first cylindrical lens 15, becomes a beam 10 that is focused in one direction, is deflected in the left-right direction by the first optical deflector, passes through the first relay lens 17 and the second cylindrical lens 18, and becomes the beam 10 that is focused in one direction. reach. First cylindrical lens 1
When the position of 5 is moved to 15' as shown by the dotted line in Fig. 3, the light beams passing through each optical element become 10' and 11' (indicated by the dotted line in the figure), and b As can be seen, new focusing surfaces 24 and 25 are created that focus in only one direction. That is, the vertical and horizontal focal points of the light beam do not coincide. Therefore, for example, if we consider the first focusing surface, which is a point conjugate to the recording medium surface, when we focus in the horizontal direction, the vertical direction becomes out of focus. The amount of this out-of-focus spreads the beam, and as a result, a light beam with an elliptical cross section can be formed.

In other words, the present invention has the advantage that when the first cylindrical lens is moved in the optical axis direction, only one of the horizontal or vertical focusing surfaces moves in the optical axis direction, and the remaining focusing surface does not move (the blurring occurs only in one direction). In this case, the only lens to be moved is the first cylindrical lens, and the arrangement of the elements after the first optical deflector is fixed, so their functions, for example, the first cylindrical lens, are fixed.
This does not affect the functions of the first relay lens 17 and the second cylindrical lens 18 for correcting pitch unevenness occurring in the optical deflector.

From the above, the first cylindrical lens 1
By continuously moving the position of 5 in the optical axis direction, the beam shape in the direction perpendicular to the scanning direction of the first optical deflector of the light beam can be continuously changed to any size without changing the beam shape in the scanning direction of the first optical deflector. You can see that it can be configured.

In FIG. 3, the first cylindrical lens 15 is moved only in one direction, but it should be taken into consideration that the shape of the intensity distribution in the cross section of the light beam is symmetrical before and after the focal point 16 of the first cylindrical lens 15. Then, even if the first cylindrical lens 15 is moved in the direction opposite to ΔZ in FIG. 3, exactly the same effect can be obtained.

In order to change the cross-sectional shape of the light beam spot on the recording medium surface from circular to vertical by using the present invention, first cylindrical lens 15, first relay lens 17, and second cylindrical lens 18 are required.
The relationship between the focal lengths _C1 , ₁ , and _C2 may be determined as ₁ ² = _C1・_C2 . In this case, if the deflection angle of the vertical deflector inserted after this optical system in a film recording device is sufficiently large,
If the scanning line spacing is sufficiently wide and the scanning lines can be resolved, if the deflection angle is small, the scanning lines will not be resolved, which may cause problems when checking or recording the raster recording state.

In order to solve this problem, the cross-sectional shape of the light beam in the vertical direction may be made smaller than a circle, that is, a horizontally elongated oval shape. In other words, if an optical system is designed under the conditions of ₁ ² > _C1 × _C2 , the cross-sectional shape of the light beam can be changed over a wide range from horizontally oblong oval to circular to vertically oblong. By doing this, when checking whether the recorded raster is written uniformly, you can record and observe a sufficiently thin scanning line of a horizontally oblong oval, and after confirming it, change the circle → vertical oval. It is possible to adjust the cross-sectional shape of the light beam in the direction and set it to a desired cross-sectional shape of the light beam. With this method, scanning line resolution can be ensured even if the deflection angle of the deflector is small, so
The range of applications is extremely wide.

Although omitted in the explanation of FIG. 3, the incident light beam 23 may be a combination of light beams of red, green, blue, etc. other than monochromatic light. Moreover, there is no problem even if 23 is a focused beam or a diverging beam other than parallel light.

In addition, as shown in Figure 4, the first cylindrical lens is connected to a light beam spot size conversion system (26, 27 in the figure) that determines the spot size of the incident beam.
When the spot size conversion lenses 26 and 27 are fixed,
By moving the first cylindrical lens 15 in the axial direction, it is possible to obtain exactly the same effect as the system shown in FIG. 3. Furthermore, the first
By dispersing the functions of the cylindrical lens 15,
Spherical lens 2 which is a lens for spot size conversion
one cylindrical lens 15 at the front and rear of 7,
15'' and make one of the cylindrical lenses movable, or place the cylindrical lens immediately before or after the spherical lens 26, which is the spot size conversion lens, to obtain exactly the same effect. can.

As explained above, by implementing this invention, the cross-sectional shape of a light beam such as a laser beam can be continuously varied to have an arbitrary ellipticity, and the spot size in the vertical direction can be changed continuously. can be controlled independently of the horizontal spot size.

Furthermore, in cases where the number of scanning lines is limited, for example, in TV image display devices and recording devices that use light beams, even if a thin beam is used to increase the resolution image, by implementing the present invention, it is possible to increase the resolution in the vertical direction. Since gaps that occur between scanning lines can be easily filled, it is possible to display and record natural images. Furthermore, if you take advantage of the fact that the beam spot can be changed continuously,
There is also the advantage that even when the number of scanning lines changes due to different television systems, the optimum beam spot for each system can be easily obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the configuration of a television image recording device using a laser beam, FIGS. 2a and 2b are diagrams showing an example of the configuration of an optical system used in a television image recording device using a laser beam, Figures 3a and 3b are diagrams explaining the principle of the present invention and a configuration diagram of an optical system showing one embodiment, and Figure 3c is a diagram showing an example of the cross-sectional shape of the beam corresponding to each part in Figures 2a and b. , Figure 4a,
b is a configuration diagram of an optical system showing another embodiment of the present invention. 1... Laser oscillator, 2... Optical modulator, 3...
First optical deflector, 4... Relay lens system, 5... Second optical deflector, 6... Imaging optical system, 7... Recording medium (second focusing surface), 8... Input signal, 9... ... Laser beam, 10, 10'... First optical deflector incident beam, 11, 11'12... One-dimensional deflected beam, 13... Two-dimensional deflected beam, 14...
Imaging beam, 15, 15', 15''...first cylindrical lens, 16...deflection surface of first optical deflector, 17...first relay lens, 18...second cylindrical lens, 19...th 1 focusing surface, 20
... Relay lens, 21 ... Deflection surface of second optical deflector, 22 ... Image forming lens, 23 ... Incident light beam, 24 ... Third focusing surface, 25 ... Fourth focusing surface,
26, 27... Lens for spot size conversion.

Claims (1)

[Scope of utility model registration request] When displaying or recording information using the deflection of a light beam, the first and second regions sandwiching a relay lens having a focal length _f1 and a spherical lens have a focal length f _C1 and a first region having a focal length f _C2 , respectively. In the beam shaping optical system including the second cylindrical lens system, the focal lengths f ₁ , f _C1 and f _C2 have the following relationship: f ² ₁ > f _C1 ×f _C2 ; The cylindrical lens of the first cylindrical lens system is adjusted in the optical axis direction while the imaging relationship between the spherical lens and the second cylindrical lens system in the direction orthogonal to the scanning line is fixed, and the light beam is formed on the surface of the recording medium. A light beam shaping device characterized in that the cross-sectional shape of the light beam can be changed from a horizontally oblong oval to a circular to a vertically oblong oval.