DE2342444A1 - DEVICE FOR OPTICAL IMAGE GENERATION USING A DIFFUSE POINT THOLOGRAM - Google Patents

Description

Apparatus for optical imaging using a diffuse Dot Holograms The present invention relates to a device for optical imaging using a point hologram with illumination through diffuse light. As used herein, "dot hologram" is related on a hologram that uses a point light source for illumination of the object is generated. When reproducing images using a hologram is, according to the state of the art, an object image that is created during the generation of the Holograms have been recorded, reproduced by exposing light to the output surface of the optical reproduction system is projected.

When generating images using a dot hologram, in contrast, a permeable object in the projection light beam for imaging pushed, and thereby the image of the permeable object thus introduced becomes generated on the optical output surface.

The point-shaped used to create a point hologram Light source should be extremely small so that the image of the translucent object is faithfully reproduced on the optical output surface, as shown in the following Consideration can be seen. In view of the fact that the OAF (optical imaging function) the optical system, which is composed of the point hologram and lenses, is constant over the entire spatial frequency bands, at least as far as the point-like light source is an optimal geometrical "point" should be point light source to be as small as possible to allow the component the spatial frequency present in the permeable object by the optical reproduction system is imaged without attenuation, and thus the image of the permeable object faithfully reproduced on the optical output surface will. According to the prior art, this is point-shaped in a Runkt hologram Light source made by using a fine hole. The bigger, however the diameter of the hole, the stronger the OAF of such an optical becomes System is sharply attenuated and the reproduced image is necessarily with provided with a vignetting. In order to get a faithful image reproduction, you have to Hole therefore have a small diameter. Accordingly, it is required that the coherent light source has a relatively high power to receive enough light, to expose the hologram plate, which is generally of low sensitivity is. A laser is often used as a light source for this purpose, and the ErzeuJOu a normal point hologram has the disadvantage of using large and expensive lasers Need to become.

In order to avoid the disadvantages of the nkt-1Iologram according to the state of the Technology is afflicted, to be exercised, the present invention provides an optical System; that enables a faithful image production, although it is a fine one Hole of relatively large diameter is used and has essentially the same effectiveness if you compare it with a system that has an ontimal point-shaped light source used. The prior art diffusion hologram has the following Properties on. First is the light intensity to be recorded for the hologram on the surface of a drying plate, which is very even, scattered and raised so the degree of diffusion.

Second, the photographic dynamic range permits that to be recorded Light intensity that the hologram recorded linearly on photosensitive material and faithful image reproduction is facilitated. Third and lastly is one Multiple exposure of the hologram as a result of the already mentioned high Measure Diffusion of the recorded information is possible. Though such a multiple recording is generally even possible if the hologram uses unscattered light, so the number of exposures is limited, especially because of the lower frequency band saturation occurring on the dry plate. The number of exposures can be through the use of a diffusion hologram can be increased, which is disadvantageous Avoids saturation effects.

In order to take advantage of the advantageous properties of a diffusion hologram, such as to realize it above in connection with a dot hologram, it is provided that .... (characteristic of claim 1).

The dot hologram which is one according to the present invention optical system (hereinafter referred to as diffusion point hologram to it to be distinguished from the dot hologram according to the prior art) is used by the following properties compared with the prior art dot hologram the technology described.

First, a larger diameter of the hole does not affect one Faithful image reproduction, as the hole that the diffuser plate faces is another has spatial frequency response, because of the property of this scattering plate, as the hole according to the prior art without the use of a diffuser plate.

This has the practical advantage that a laser of low power and low cost can be used to that Diffusion funct hologram to be able to generate. Second, it can produce images with uniform light intensity from each;, no area of the hologram can be preserved, due to the dead diffusion, which is a special property of the diffusion point ologram in general. The common prior art dot Holcgram is with some The recorded information is tied to location, and so are, for example the images corresponding to an area near the optical axis and an outer area of the same holograms correspond to each other slightly different, what of the aberration of the hologram and a complicated amplitude - allocation of the to be recorded Light depends. Such a disadvantage of an ordinary dot hologram becomes effective fixed through the use of a disfusion point hologram.

Thirdly, in a known method of multiple generation of dildos, a multiple point hologram through good exposure for each relative position of the hole and the dry plate is formed, the use of the diffusion point hologram according to the invention, the possibility of such a multiplication due to the same considerations as discussed above in connection with the Diffusion kilogram have been employed.

Embodiments according to the invention are illustrated with the aid of the accompanying figures described, FIG. 1 showing a preferred embodiment of an optical system shows for point hologram generation in the manner of the Fourier transform, where is illuminated with diffuse light, Fig. 2 shows a preferred embodiment of a optical system in an imager of the Fraunhofer type shows, where a Diffusion point hologram is used for a permeable object, Fig. Da, 3b and nc the Fourier transform the tT function, the circular function and a random function, FIG. 4 shows a preferred embodiment of an optical system in a Fresnel-type imager shows using a diffusion point hologram for a transmissive article Fig. 5 shows a preferred embodiment of an optical system in a device shows, in order to illuminate an imaging object incoherently, FIG. 6 shows a preferred one Embodiment of an optical system in a lighting device for a shows reflective imaging object.

According to FIG. 1, a light source 1 is produced from a coherent light source Light beam enlarged through a lens 2 and through a lens 3 into a parallel one Light beam converted. After the light beam through a half-silvered plate 4 has passed through, it falls on a diffuser plate 5 which is perpendicular to the optical Axis is arranged. A small opening 6a is close next to it on the optical axis the scattering plate 5 arranged. The diameter of the small opening 6a must be optimal for imaging because the diameter of the small opening 6a is reversed proportional to the strength of the appearance of a mottled background pattern of imaging and is also inversely proportional to resolving power.

Diffuse light emerging from the small opening 6a is now noticeable the lens 7, which is spaced from the small opening 6a the Focal length f7 of the lens 7 is located and the light that has passed through the lens 7 falls on a photosensitive material 8, which is in the rear focus of the Lens 7 is arranged perpendicular to the optical axis. That of the half-silvered one Plate 4 reflected parallel light is reflected by a mirror 9 and falls on the photosensitive material 8 as a reference light beam at an angle e with respect to the optical axis.

The object light beam coming from the small opening 6a interferes with the reference light beam to form an interference pattern on the photosensitive material 8 to form. The photosensitive material 8 can be developed to be a dot hologram of the Fourier transform tape when illuminated with diffuse light will. This will continue to be referred to as a diffusion point hologram. The penetration ability the amplitude T (x) of this diffusion point hologram is given by the following Equation (1) expressed: T (x) ß T0 + 3 Aezp (- ik sin G) + F {P (u)} (1) Zur The penetration force of the amplitude is simplified by a linear coordinate expressed. x is a coordinate on the diffusion point hologram. T0 and B are Constants used only by the photosensitive material 8 and the developing method depend. A is an amplitude of the reference light, k is a wavenumber of the reference light and @ is an angle between the reference light and the optical axis. u is a coordinate of the small opening 6a, P (u) is a penetration force of the The amplitude of the small opening 6a in connection with the diffusion plate 5 and F is a Fourier transform operator.

In Fig. 2, a light beam that. from the coherent light source 1 comes from, enlarged by the lens 2 and by the lens 3 in a parallel Light beam converted. The width of this parallel light beam is sufficient, to cover the permeable article 10. The parallel beam of light leaves the permeable object 10 in the form of a Fraunhofer scattered light beam and falls on the diffraction point hologram 12. The angle between the optical axis generated by the coherent light source 1, the collimator lenses 2 and 3, the transmissive article 10 and the lens 11 is defined and the optical Axis passed through diffusion point hologram 12, lens 15 and an exit surface 14 is defined, is selected to be the same size as the angle of incidence @ g of the reference light in the optical system as shown in FIG.

An amplitude of the incident on the diffusion point hologram 12 Light can be expressed by F {S (v) 0 (ik sin) where S (v) is an amplitude penetration force of the permeable object 10 means (v means a coordinate of the permeable Item 10). From the light emitted by the diffusion point hologram 12, only the primary scattered light is Fourier-transformed again by the lens 13 and an amplitude H (w) of the light obtained in the back focal plane of the lens 13 (i.e. the gate out surface 14) is described by the following equation (2): H (W) = A. B. F [F {P (u)}. F {S (v)] ........... (2) where w is a coordinate of the output surface 14 means. Assume that the small opening 6a has an optimal geometric Point represented and no scattering plate 5 (see Fig. 1) in the point hologram generation were present, the amplitude penetration force would be the small opening in the equation (2) one; Function (u). Accordingly, equation (2) can be used in the following manner expressed as follows: H (w) = A-BSt - v). ---, (3) It follows from equation (3), that the permeable article 10 on the dispensing surface 14 is sharp and true is mapped. Figures Da, 3b and 3c show this with respect to the Fourier spectrum F {P (uÜ the penetration force P (u) of the small opening.

Fig. Da shows the Fourier spectrum F {# (u)} with respect to an optimal Point holograms, where F {(u) 3> 3 = 1 over the entire frequency range. As far as Fig. 3a is concerned, the permeable article 10 can faithfully the output surface 14 can be reproduced. However, it is practically impossible to produce such an optimal point hologram, and the small opening 6a (see Fig. Fig. 1) has a certain expansion. Without a diffuser the penetration force can in this case of the small opening 6a can be expressed by circ (usa) where a is the radius of the small opening 6a means circ (U / a) = 1 (| u / a | # 1), and circ (u / a) = O (| u / a |> 1). The spectrum of such a small opening therefore shows a sharp attenuation in the upper spatial frequency range, as shown in Fig.3b. The higher one Frequency range contained in the permeable article 10 is cut off and the result is an image reproduction on the output surface 14, the one Has vignetting. Although the reproduction even in the higher spatial frequency range would be possible if the diameter of the small opening is reduced as it continues As mentioned above, the light source would have to be of high power, and so would practically mean that the dot holograms are extremely limited.

The method, the diffusion point hologram according to the invention to use is that the diameter of the small opening is a little larger than that of the low-power laser3 that can be obtained cheaply on the market is selected, and that the diffuser plate is in close proximity to the small Opening is arranged to increase the characteristic in the higher spatial frequency range to enhance.

The operation of this diffusion plate will now be described with reference to FIG. 5c described. The spectrum that the combination of small opening and diffusion plate leaves, as shown in Fig. 3c, has a further spatial frequency range, than the spectrum as shown in Fig. 5b and is approximately equivalent with the spectrum of the optimal small opening (see Fig. 3a). That means that one faithful image of the permeable article 10 effectively through the use of the diffusion point hologram 12 can be obtained and that, as before It has been pointed out that the main objective of the invention is a picture of To obtain high resolving power can be achieved by widening the Penetration force of the diffuser plate, even if the small opening is a bit larger Has diameter. It should be noted that using a On the other hand, the image obtained from diffusion point holograms has vignetting would be provided (see the small spikes on the spectrum of Fig. 3c) what of the scattering characteristics of this scattering plate comes from. This vignetting that the Figure negatively affected can be removed by having a method for Incoherent light imaging is used, as further described below will be.

The optical system shown in Fig. 2 is used to generate an optical Image in which the light from the permeable object is scattered in the Fraunhofer style 10 is directed onto the diffusion point hologram 12. As a different procedure for image generation, could transmit light scattered in the Fresnel way Object 10 are directed to the diffusion point hologram 12, and a preferred embodiment of an optical system for such a case shown in FIG.

The light beam emerging from the coherent light source 1 becomes enlarged by lenses 2 and 5 and converted into a parallel light beam, which in turn falls on the permeable Ge object 10 and then becomes an image of the transmissive article 10 through the lens 13 on the output surface 14 formed, as shown in the embodiment of FIG. It will it should be noted that the permeable article 10 and the dispensing surface 14 must be conjugate to one another with respect to the lens 17. Compared to the process of image generation according to the Fraunhofer type (Fig. 2), this is after of the Fresnel kind characterized by the following two points of view. First, an optical structure can be simplified in the second case (Fig. 2), since the lens 11 between the permeable article 10 and the diffusion point hologram 12 can be omitted while a practical adjustment of the optical system can be advantageously increased in its structure that the distance between the permeable object lo and the diffusion point hologram 12 are freely selected can be. Second, the transmissive article 10 can be on the optical axis are shifted by a spectrum of that generated on the output surface 14 Changing the image is a general Fresnel type of hologram possible to thereby make the image soft and hard in an advantageous manner for the image development process to adjust.

There are two methods to remove the vignetting, the one A significant disadvantage is encountered with the diffusion point hologram process. The first method is that an incoherent quasi-monochromatic light source instead of the coherent light source 1 (see FIGS. 2 and 4) in the optical system for Imaging is used, and the second method is given by the coherent light source 1 is used and that a rotatable diffuser plate directly is arranged in front of the permeable article 10. These methods can work for anyone optical system either according to the Fraunhofer type or according to the Fresnel type Kind be applied. Although a normal hologram does not use incoherent light can be played back, but a Pankt hologram can be successful through incoherent Light can be reproduced. A preferred embodiment of the second method is shown in FIG. A light beam generated by the coherent light source 1 is enlarged by the lenses 2 and 5 and into a parallel beam of light converted, which in turn impinges on a disc-shaped diffuser plate 5a, which has a larger radius than the diameter of the parallel light beam. Of the The center of this disc-shaped diffusion plate 5a is removed from the optical axis and the disc-shaped scattering plate 5 a is rotated by a motor 15. The ray of light which leaves the disc-shaped rotating diffusion plate 5a, falls in the optical The image formation system on the transmissive article XG as shown in Figs. 2 and 4, and thereby an optical image is obtained on the output surface 14, which is completely free from vignetting. The resolving power of the sp the image obtained is much larger than that obtained with the illumination with simple diffused light.

Although the subject of the image is made in the diffusion point hologram process has previously been used as a permeable Subject described like a two-dimensional pattern captured on film it is also possible to take an image of a reflective imaging object to create; A preferred embodiment of an optical system that uses an image from a reflective imaging object is shown in FIG. 6.

The beam emerging from the coherent light source 1 is through the lenses 2 and 3 enlarged and converted into a parallel beam of light, the again, impinges on a half-silvered plate 4. The one from the half-silvered one Plate 4 reflected light beam then falls on the reflective object 16 and the light reflected by this object 16 passes through the half-silvered one Plate 4 through it. That of the semi-silvered plate 4 adjoining optical System is identical to that shown in Figs. 2 or 4, but with a 6 has not been shown. The light beam from this reflective Object 16 creates a corresponding image on the output surface 14, after having covered the same light path as in FIGS. 2 or 4.

It is evident that the two methods, as already mentioned, also in this case can be applied to remove the vignetting.

Based on the description above, it is easy to see that the imaging to which a diffusion point hologram according to the invention has been used has the following characteristics and advantages.

First, the subject of the image can be both transparent and transparent reflective sin.

Second, optical imaging systems of the Fraunhofer type or Fresnel type can be used for normal hologram display.

Third, it is possible to display the hologram under lighting of incoherent light like an ordinary dot hologram.

Fourth, it becomes a high spatial frequency characteristic of the image due to the scattering effect of the 'scattering plate obtained even if the diameter the small opening is relatively large, and accordingly a faithful Figure can be achieved.

Fifth, the diffusion point hologram exhibits a high degree of scattering effect based on the same considerations just mentioned.

Sixth, and finally, the diffusion point hologram knows one advantageous possibility for multiple specification of information on, in particular in the use of both pattern recognition, information referencing and the like.

This multiple specification can be implemented in three different ways will. The first method is to have the imaging optical system a Diffusion point hologram with a plurality of small openings that are arranged in a grid shape so that a plurality of images of the same Object in the grid arrangement on the output surface of the optical system can be obtained according to the arrangement of the small openings. The second method consists in a multiple exposure during which the direction of the Reference light continuously during the creation of the diffusion point hologram is changed so that a plurality of images in accordance with the so varying Reference light can be obtained on the output surface upon image formation. The third method is a combination of the first and second Method wherein a plurality of small openings arranged in a grid shape during the creation of the diffusion point hologram together with a diffusion point hologram that is subjected to multiple exposure as soon as the direction is used of the reference light is changed and thereby a multiple image on the output surface che is obtained. Such a multiplication of the figure can also be successful be realized with a point hologram of a known type.

The multiplication in the diffusion point hologram according to the invention is characterized by the following aspects. As mentioned earlier, is the uniformity of the multiple pieces of information on such a diffusion point hologram recorded is much higher than that of a well-known point hologram, since the Diffusion point hologram has a relatively narrow photographic dynamic range Has. In other words, even pieces of information within any small one n area on the diffusion point hologram can be faithful to the corresponding image because they are spatially independent on the diffusion point hologram is information recorded on an ordinary dot hologram is necessarily afflicted with a local characteristic, so that e.g. there is a difference, even if it is slight, between images that come from a come to the optical axis adjoining sub-section or from an outer one Area of the point hologram, the difference being the aberration of the hologram and a different information recording density.

The advantages and properties mentioned make it easy to use the method for image generation using - the diffusion Runkt hologram according to the invention, a multiplication of the image. It also provides it is a useful means of pattern recognition as well as information referencing represents the simultaneous and parallel optical operations of input data high Can handle density and speed.

- patent claims -

Claims (7)

P A T E N T A N S P R Ü C H E 1. Device for optical image generation, as a result, that a small hole (6a) and one opposite it Diffuser plate (5) for generating a diffuse light beam and devices for Generation of a parallel reference light beam are present, the diffuse Light beam and the parallel reference light beam create a diffusion point hologram, and that a transparent or reflective imaging object and an optical Output surface (8, 14) are present, the diffusion point hologram through Light waves coming from the input pattern are enlightened to a faithful one To generate an image of the Xin! 2. winrichtung for optical imaging according to claim 1, characterized it is not indicated that a faithful representation of the translucent or reflective Image object through an optical system and through the diffusion point hologram is generated according to claim 1, wherein the optical system is designed Fraunhofer To generate scattered light of the subject. 3. direction for optical imaging according to claim 1, characterized It is not indicated that a faithful representation of the translucent or reflective Image object through an optical system and through the diffusion point hologram according to claim 1, wherein the optical system is designed so as to Fresnel To generate scattered light from the object to be displayed. 4. Device for optical image generation according to uen claims 1 and 2 or 5, in that the depicted object is from incoherent, quasi-monochromatic light, and that this causes vignetting of the image of the image object is removed. 5. Device for optical image generation according to claim 1, characterized It is not noted that a diffusion point hologram is through a multitude Small openings equally arranged in one plane and one opposite them Diffusion plate is generated, and that an optical system is in place to a variety to generate images that correspond to the subject of the image according to the location of the small Openings correspond. 6. Device for optical image generation according to claims 1 and 2 or 5, characterized in that a rotatable spreading plate (5a) is arranged in the immediate vicinity of the subject and that the diffusion plate and the imaging object can be illuminated by coherent light to produce vignetting to remove the image of the subject. 7. Device for optical image generation according to claims 1 and 6, noting that the diffusion point hologram during its generation of multiple exposure according to the change in direction is subjected to a reference light beam, and that thereby the image of the object to be imaged is multiplied. L e r s e i t e