JP4821964B2 - Hologram observation tool - Google Patents

Description

  The present invention relates to a hologram observation tool, and more particularly to a hologram observation tool capable of observing a predetermined character string near the position of a point light source when the point light source is observed through a computer generated hologram configured as a transmission type Fourier transform hologram. is there.

  In Patent Document 1, hologram glasses are proposed. The hologram glasses are configured as shown in a perspective view in FIG. That is, two transmission holograms 2 and 3 are fitted into the binocular frame of the spectacle frame 1. When a scene including light sources 4, 5, 6, and 7 having a small area as shown in FIG. 6B is viewed by wearing glasses using the transmission holograms 2 and 3, for example, as shown in FIG. 6C. Looks like. That is, the light sources 4, 5, 6, and 7 in the actual scene in FIG. 6B appear as scenes that are replaced with the previously selected patterns “NOEL” 8, 9, 10, and 11, respectively. Alternatively, patterns “NOEL” 8, 9, 10, and 11 appear to overlap in the vicinity of the light sources 4, 5, 6, and 7. As the transmission holograms 2 and 3 having such characteristics, a Fourier transform hologram (Fraunhofer hologram) having the pattern “NOEL” configured as a computer generated hologram is used.

  Such transmission holograms 2 and 3 are created as phase holograms, for example, as follows.

  FIG. 1A is a flowchart showing one method for creating such a transmission hologram (Patent Document 2). FIG. 1B is a schematic diagram for explaining the flowchart. In step 101, an original image 21 is created. Next, in step 102, a Fourier transform image 22 of the original image is created using a computer. Next, in step 103, the Fourier transform image 22 is multi-valued into binary values or more to create a Fourier transform image 23. In step 104, a reproduced image is simulated. In this simulation, an inverse Fourier transform is performed on the multi-valued Fourier transform image 23 to obtain a reconstructed image 24, and it is checked whether the processing in each of the above steps has been performed properly. Next, in step 105, the obtained multi-valued Fourier transform image is arranged to a desired range. For example, a computer-generated hologram 25 is obtained by arranging four binarized Fourier transform images 23 vertically and horizontally. In practice, for example, 10 Fourier transform images 23 of minimum units are arranged vertically and horizontally. Next, at step 106, a master for duplication of the computer generated holograms 25 arranged in this way is prepared using, for example, a semiconductor process (photolithography and etching). Then, in step 107, the concavo-convex relief pattern of the original for duplication is duplicated on, for example, an ultraviolet curable resin to obtain transmission holograms 2 and 3.

  Such holographic glasses can be seen in the vicinity of the position of the light sources 4, 5, 6, 7 when a scene including the light sources 4, 5, 6, 7 having a small area is observed through the transmission hologram 2 or 3 on one side alone. A hologram observation tool that can be observed by reproducing a predetermined image or message ("NOEL" in FIG. 6C) can be configured.

Then, in the hologram observation tool composed of a Fourier transform hologram configured as such a computer generated hologram, in order to make a conjugate image and a pattern in which a higher-order image is inconspicuous, 2/3 of a reproduced image region of the computer generated hologram is displayed. In the following, Patent Document 3 proposes that an original image pattern that is desirably reproduced within a range of 1/2 or less is recorded on a computer generated hologram.
US Pat. No. 5,546,198 Japanese Patent Laid-Open No. 10-153943 JP 2004-126535 A

  However, in a conventional hologram observation tool using a computer generated hologram, a character string that appears to replace light sources 4, 5, 6, and 7, or a character string that appears to overlap light sources 4, 5, 6, and 7 (in the case of FIG. 6). “NOEL”) was not of satisfactory image quality and satisfactory reading.

  The present invention has been made in view of such problems of the prior art, and its purpose is to appropriately set the relationship between the number of pixels of an original image recorded on a computer generated hologram and the recording size of the pixels of the computer generated hologram. Accordingly, it is an object of the present invention to provide a hologram observation tool capable of observing a character string that is replaced or overlapped with a small-area point light source in a scene with good image quality.

The hologram observation tool of the present invention that achieves the above object comprises a computer generated hologram configured as a transmission type Fourier transform hologram. When a point light source is observed through the hologram, a predetermined character string is reproduced near the position of the point light source and observed. In a possible hologram observation tool, the number of horizontal pixels N _x , the number of vertical pixels N _{y of} the original image data recorded in the computer generated hologram, the recording size W _x of the horizontal pixels of the computer generated hologram, and the vertical direction The pixel recording size W _y satisfies the following relationship.

W _x × N _x ≦ 2.828 (mm) (1 ′)
W _y × N _y ≦ 2.828 (mm) (2 ′)
W _x ≦ λ / (0.004 × NT _x ) (13)
W _y ≦ λ / (0.004 × NT _y ) (14)
Where λ is the wavelength of the point light source, NT _x is the number of characters in the horizontal character string, and NT _y is the number of characters in the vertical character string.

In that case, it is desirable that the number of horizontal pixels N _x and the number of vertical pixels N _{y of} the original image data recorded in the computer generated hologram satisfy the following relationship.

N _x ≧ 12 × NT _x (17)
N _y ≧ 12 × NT _y (18)
Further, the computer generated hologram is preferably configured by arranging a predetermined number of unit computer holograms composed of Fourier transform images of the original image in the horizontal direction and the vertical direction.

According to the present invention, when a point light source is observed through a hologram, a predetermined character string is reproduced in the vicinity of the position of the point light source and can be observed, and in the horizontal direction of the original image data of the character string recorded on the computer generated hologram Pixel number N _x , vertical pixel number N _y , horizontal pixel recording size W _x , and vertical pixel recording size W _y of the computer generated hologram in which the original image data of the character string is recorded. By setting the range, it is possible to observe a character string that is replaced or overlapped with a point light source having a small area in the scene with good image quality.

The hologram observation tool of the present invention records characters recorded on a computer-generated hologram configured as a transmission-type Fourier transform hologram that allows a predetermined character string to be reproduced and observed near the position of the point light source when the point light source is observed through the hologram. The number of horizontal pixels N _x and the number of vertical pixels N _y of the original image data of the column, the recording size W _x of the horizontal pixels of the computer hologram on which the original image data of the character string is recorded, and the vertical pixels By setting the recording size _Wy to a predetermined range, it is possible to observe a character string that is replaced or overlapped with a small area point light source in the scene with good image quality.

  Hereinafter, the principle of the hologram observation tool of the present invention will be described with reference to the drawings.

In the present invention, the number of pixels N _x and N _y of the original image 21 in FIG. 1B and the Fourier transform image 23 (hereinafter referred to as a unit computer hologram 23) obtained by multi-valued the Fourier transform image 22 of the original image 21 are described. In other words, it is possible to observe a reproduction image of a character string having an image quality that can be clearly read at a desired resolution by examining the relationship between the pixel recording sizes W _x and W _y . FIG. 2 is a diagram schematically illustrating the relationship between the pixels of the original image 21 and the unit computer hologram 23. Since the original image 21 and the unit computer hologram 23 are in a Fourier transform relationship, the horizontal direction of the original image 21 is illustrated. Where N _{x is} the number of pixels and N _y is the number of pixels in the vertical direction, the number of pixels of the unit computer hologram 23 is N _x and N _y which are the same as the number of pixels of the original image 21 in the horizontal and vertical directions. When the horizontal pixel recording size of the unit computer hologram 23 is W _x and the vertical pixel recording size is W _y , the horizontal dimension of the unit computer hologram 23 is W _x × N _x , The dimension is W _y × N _y .

FIG. 3 is a diagram schematically showing the relationship between the pupil 31 of the eye 30 and the unit computer hologram 23 of the computer generated hologram 25 constituting the hologram observation tool when the human eye 30 observes the hologram observation tool of the present invention. If the unit computer hologram 23 repeatedly arranged in the horizontal and vertical directions of the computer hologram 25 satisfies the dimensional relationship such that it falls within the diameter D _p of the pupil 31 of the eye 30, the human eye will be in the computer hologram 25. The recorded original image 21 appears to be completely reproduced. Conversely, if the unit computer generated hologram 23 is dimensional relationships as eclipsed by the pupil 31 not enter into the diameter D _p of the pupil 31 of the eye 30, the number of pixels is reduced human eyes units computer generated hologram 23 Therefore, the number of pixels of the reproduced image corresponding to the inverse Fourier transform image is reduced, and the resolution is lowered.

Therefore, if the unit computer hologram 23 is a square,
W _x × N _x ≦ D _p / √2 (1)
W _y × N _y ≦ D _p / √2 (2)
Satisfying the conditional expressions (1) and (2) are conditions under which a recorded image can be observed with sufficient resolution. Here, since the diameter D _p of the pupil of the human eye is large (about 8 mm) in the dark place and small (about 2 mm) in the bright place, if D _p = 4 mm as a representative size, the conditional expression ( 1) and (2)
W _x × N _x ≦ 4 / √2 (mm) = 2.828 (mm) (1 ′)
W _y × N _y ≦ 4 / √2 (mm) = 2.828 (mm) (2 ′)
Thus, in order to be able to observe the image recorded on the computer generated hologram 25 with sufficient resolution, it can be said that the conditional expressions (1 ′) and (2 ′) must be satisfied.

  Next, when an image of a character string is recorded as the original image 21 on the computer generated hologram 25 (unit computer generated hologram 23), each character of the original image can be recognized in the reproduced image 24 reproduced from the computer generated hologram 25. Consider the conditions related to the size (angle) of the reconstructed image.

When the character “G” having a plurality of different character heights was observed from a distance of 5 m, a human with a visual acuity of 1.5 can recognize the character as “G” if the character height is 10 mm or more. I understood the result. At this time, if the angle at which the letter “G” is expected is 2θ ₀ , referring to FIG.
θ ₀ = arctan (5 mm / 5000 mm) ≈0.001 [rad]
... (3)
It is.

When observing a plurality of characters side by side, the angle at which the entire character string is viewed increases substantially in proportion to the number of characters. Assuming that the number of characters in the horizontal character string is NT _x , each character constituting the character string can be recognized if θ _x satisfies the following expression, where the horizontal angle of view of the entire character string is 2θ _x .

θ _x ≧ NT _x × θ ₀ = 0.001 × NT _x [rad] (4)
On the other hand, the angle 2θ _I at which the figure observed through the computer generated hologram 25 of the hologram observing tool is viewed is referred to FIG. 4B, and the minimum lattice interval included in the hologram pattern of the computer generated hologram 25 is P _x and the wavelength is λ. When the distance between the point light source 41 (corresponding to the light sources 4, 5, 6, and 7) for reproducing the figure and the computer generated hologram 25 is B, and the distance between the computer generated hologram 25 and the observer's eye 30 is A, It is determined as follows.

C = Btanθ _b (5)
Here, C is ½ of the height of the figure (character “G” in FIG. 4B) reproduced near the position of the point light source 41, and θ _b is 1 / of the angle at which the figure is viewed from the computer generated hologram 25. 2. On the other hand, from the diffraction equation:
P _x = λ / sin θ _b (6)
There is a relationship. From this equation (6)
θ _b = arcsin (λ / P _x ) (7)
It becomes. on the other hand,
tan θ _I = C / (A + B) (8)
Therefore, using equations (5) and (7),
θ _I = arctan [Btan {arcsin (λ / P _x )} / (A + B)]
≈ Bλ / P _x (A + B) [rad] (9)
Furthermore, in the normal usage pattern, B >> A, so from the equation (9),
θ _I ≈λ / P _x (10)
It becomes.

In the case of a character string observed through the computer generated hologram 25 of the hologram observing tool, the angle 2θ _I for viewing the figure observed through the computer generated hologram 25 is the conditional expression (4) of the expected angle 2θ _{x in} the horizontal direction of the entire character string. If satisfied, the character string observed through the computer generated hologram 25 can be recognized. That is,
θ _I ≧ 0.001 × NT _x [rad] (11)
Therefore, using equation (10),
P _x ≦ λ / (0.001 × NT _x ) (12)
It becomes. In order to express the minimum grating interval P _x as a set of pixels, it is desirable that the minimum grating interval P _x is composed of at least four pixels (at least four pixels are required to express a diffraction grating having a sinusoidal cross section). . That is, since the recording size of one pixel is W _x , the condition for recognizing each character constituting the character string observed through the computer generated hologram 25 is as follows:
W _x ≦ λ / (4 × 0.001 × NT _x ) = λ / (0.004 × NT _x )
... (13)
It becomes.

The above is for the horizontal direction, but for the vertical direction as well,
W _y ≦ λ / (0.004 × NT _y ) (14)
It becomes. However, NT _y is the number of characters in the vertical direction string.

  Next, when the original image of the character string is recorded as the original image 21 in the computer generated hologram 25 (unit computer generated hologram 23), the conditions regarding the size (number of pixels) of the original image 21 for recognizing it as a character are examined.

  When the hologram of the hologram observation tool is created by the computer generated hologram 25, it is necessary to draw an image to be observed using the hologram observation tool as a set of pixels (original image 21 in FIG. 2). For this reason, even when the image to be observed is a character string, it is necessary to draw each character as a set of pixels. When alphabets are considered as characters, in order to distinguish all 26 alphabets, the number of pixels of at least 5 pixels horizontally and 5 pixels vertically is required. In order to make an image to be observed a character string, characters composed of 5 pixels × 5 pixels are arranged to create an image 21 of the character string. Actually, in order to arrange characters composed of 5 pixels × 5 pixels into a character string image, a space of one pixel is required between characters, so the number of pixels required per character Is 6 pixels × 6 pixels.

Here, assuming that the number of characters arranged in the horizontal direction is NT _x as described above and the number of characters arranged in the vertical direction is NT _y , the number of pixels NI _x and NI _y for the character string image to be regarded as a set of characters is
NI _x ≧ 6 × NT _x (15)
NI _y ≧ 6 × NT _y (16)
It is.

  On the other hand, when the computer generated hologram 25 of the hologram observation tool is observed, a high-order diffraction image having the same pattern as the original reproduction image is reproduced around the reproduction image region as described in Patent Document 3. For this reason, if an image to be observed as a reproduced image of the computer generated hologram 25 is arranged in substantially the entire area of the original image 21 of the computer generated hologram 25, the image is reproduced around the original pattern to be reproduced (in this case, a character string). The high-order diffraction image is too close to the original pattern, which is undesirably disturbing. For this reason, it is desirable to arrange the pattern to be observed within a range within 1/2 of the central portion of the original image 21 in both vertical and horizontal directions.

When the above conditions are added, the number of horizontal pixels N _x and the number of vertical pixels N _y of the original image 21 for reproducing a character string as a reproduced image of the computer generated hologram 25 of the hologram observation tool are as follows. It is necessary to satisfy the formula.

N _x ≧ 2 × NI _x ≧ 12 × NT _x (17)
N _y ≧ 2 × NI _y ≧ 12 × NT _y (18)
Hereinafter, an embodiment of the hologram observation tool of the present invention will be described. A computer generated hologram 25 used for an observable hologram observation tool was created by replacing the point light source in the scene (light sources 4, 5, 6, and 7 in FIG. 6) with the character string “I Love You” as shown in FIG. .

The number of characters NT _{x in} the horizontal direction of the original image is six characters of “I Love”, which is the larger of “I Love” in the upper row and “You” in the lower row, and NT _x = 6. Here, the “space” between “I” and “Love” is also counted as one character. The number of characters NT _{y in the} vertical direction is NT _y = 2 because there are a total of two lines of “I Love” and “You”. The distance B from the hologram to the point light source is B = 2 m, and the wavelength λ of the point light source is 550 nm.

When creating a hologram observation tool under the above conditions, the number of horizontal pixels N _x , the number of vertical pixels N _y of the original image data of the computer generated hologram 25, the recording size W _x of the horizontal pixels of the computer generated hologram 25, and the vertical By setting the recording size W _y of the pixels in the direction to the following range based on the conditional expressions (1 ′), (2 ′), (13), (14), (17), (18), A hologram observation tool capable of observing a character string with good image quality can be obtained.

W _x × N _x ≦ 2.828 (mm)
W _y × N _y ≦ 2.828 (mm)
W _x ≦ λ / (0.004 × NT _x ) = 0.55 μm / (0.004 × 6)
= 22.916 μm
W _y ≦ λ / (0.004 × NT _y ) = 0.55 μm / (0.004 × 2)
= 68.75 μm
N _x ≧ 12 × NT _x = 12 × 6 = 72
N _y ≧ 12 × NT _y = 12 × 2 = 24
Within the above range, W _x , W _y , N _x , and N _y are set as follows to create a computer generated hologram 25 of the hologram observation tool. The string could be observed.

W _x = 5μm
W _y = 5μm
N _x = 256
N _y = 256
W _x × N _x = 1.28mm
W _y × N _y = 1.28mm
Although the hologram observation tool according to the present invention has been described based on the embodiments, the present invention is not limited to these embodiments and can be variously modified.

It is the flowchart (a) which shows one preparation method of the transmission type hologram for the hologram observation tool based on this invention, and the schematic diagram (b) for demonstrating the flowchart. It is the figure which showed typically the relationship between the pixel of an original image and a unit computer hologram. It is a figure which shows typically the relationship between the eye computer and the unit computer hologram of the computer hologram which comprises a hologram observation tool when human eyes observe the hologram observation tool of this invention. It is a figure for examining the conditions regarding the magnitude | size of the reproduction | regeneration image in order that each character can be recognized in a reproduction | regeneration image, when recording the image of a character string on a computer generated hologram as an original image. It is a figure which shows an example of the character string recorded on a computer generated hologram as an original image. It is a figure for demonstrating the hologram glasses as a hologram observation tool, and its effect | action.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Glasses frame 2, 3 ... Transmission hologram 4, 5, 6, 7 ... Small area light source 8, 9, 10, 11 ... Preselected replacement pattern 21 ... Original image 22 ... Fourier transform image 23 ... Many Quantized Fourier transform image (unit computer generated hologram)
24 ... reproduced image 25 ... computer generated hologram 30 ... human (observer) eye 31 ... eye pupil 41 ... point light source

Claims (2)

In a hologram observing tool comprising a computer generated hologram configured as a transmission type Fourier transform hologram, and when a point light source is observed with one eye through the hologram, a predetermined character string is reproduced near the position of the point light source. The number of horizontal pixels N _x , the number of vertical pixels N _y , the horizontal pixel recording size W _x , and the vertical pixel recording size W _{y of the} computer generated hologram have the following relationship: A hologram observation tool characterized by satisfying.
W _x × N _x ≦ 2.828 (mm) (1 ′)
W _y × N _y ≦ 2.828 (mm) (2 ′)
W _x ≦ λ / (0.004 × NT _x ) (13)
W _y ≦ λ / (0.004 × NT _y ) (14)
N _x ≧ 12 × NT _x (17)
N _y ≧ 12 × NT _y (18)
However, the wavelength of λ is a point light source, the number of characters of NT _x is the horizontal string, NT _y is Ri characters der the vertical string, wherein at least one of the NT _x and NT _y is 2 or more integer Oh Ru. 2. The hologram observation tool according to claim 1, wherein the computer generated hologram is configured by arranging a predetermined number of unit computer holograms composed of Fourier transform images of an original image in a horizontal direction and a vertical direction.

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