JPH09248935A - Image recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To regenerate an image formed as an overlapped hard copy by the simple operation by generating a given pattern image signal and applying the modulation to the above-said signal by a first image signal to form a pattern modulation image signal, which is recorded on a second image signal. SOLUTION: For example, a color difference pattern image signal 753 is issued as a pattern image signal from a pattern generating section 703, and the phase modulation is applied in compliance with an embedded image signal 751 output from a first image memory 701 in a pattern modulation section 704 to form the pattern modulation image signal 754. Then the pattern modulation image signal 754 is overlapped on an image signal 752 to be embedded output from a second image memory 702 by a pattern overlapping section 705 to form a pattern overlapping image signal 755. The pattern overlapping image signal 755 is converted into an ink quantity signal 756 by a color modifying section 766, and then input into an image recording section 707 to output a hard copy image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus, and more particularly to a recording apparatus for superimposing another additional image on a main image and recording the additional image from an image on which the additional image is superposed and recorded. The present invention relates to a playback device for playing a typical image.

[0002]

2. Description of the Related Art A technique of superimposing other additional information (mainly an image) on a certain image and recording the additional information together with the image invisible is known as, for example, an ID card or a logo mark on which an image such as a facial photograph is recorded. This is effective in preventing falsification and forgery of documents and other recorded materials in which images such as stamps and seals are recorded as images. As a method of superimposing additional information on the recorded image,
Conventionally, the following methods are known.

(1) "Synthesis coding method of text data to image by color density pattern", Journal of Image Electronics Engineers of Japan,
17-4 (1988), pp194-198 (Reference 1)
Discloses a method of superimposing information on a digital image expressed in pseudo gradation. In this method, when the density is expressed in pseudo gradation, the additional information is superimposed by using the degree of freedom that the same density can be expressed in a plurality of gradation patterns.

(2) Komatsu et al .: "Proposal of Digital Watermark in Document Image Communication and Its Application to Signature", J. Theory J72
-B-1, pp208-218 (reference 2), digitally superimposes a second image obtained by performing a predetermined conversion on the first image. In this method, the low-frequency component of the second image is converted into the high-frequency component, so that the second image is invisible to humans or is observed as noise-like meaningless. The second image can be restored by performing a predetermined second conversion on the superposed image of the first image and the second image.

(3) JP-A-4-294862 (reference 3)
Discloses a method in which a recorded copying machine or the like can be specified from a hard copy output of a color copying machine. In this method, a small yellow dot pattern is recorded over the hard copy output. This dot pattern has a shape according to conditions such as the model number of the copying machine. By reading this hard copy output with a scanner or the like, extracting the dot patterns recorded in an overlapping manner, and performing a predetermined signal processing, the recorded copying machine can be identified.

(4) JP-A-7-123244 (Reference 4)
Discloses a method of superimposing additional information on a color image as a high-frequency color difference signal. In this method, additional information is coded, and a color difference component having a high spatial frequency peak corresponding to the code is superimposed and recorded on the original image. Since the color difference component of the high spatial frequency is hard to be seen by humans, the added additional information hardly deteriorates the original image. Further, since a general image contains almost no high-frequency color difference component, the superimposed additional information can be reproduced by reading the recorded image and extracting the high-frequency color difference component by signal processing.

(5) Although it is not superimposition of additional information on an image, as a similar example, Muura: “Simple image encryption method for decryption processing”, IEICE J72-B-1, 12 (Reference 5) The scheme is known. In this method, two random images are formed, and when these are superimposed, a significant image appears. However, it does not superimpose invisible information on a significant image.

(6) Oka: "Visual encryption of information", 19
In the Proceedings A-123 (Reference 6) of the 1995 IEICE Basic and Boundary Society Conference, when a certain image is expressed in pseudo-tone, two images that have different density-tone expression patterns in specific areas are used. A method is proposed in which a specific area appears dark when an image is created and two images are overlapped.

[0009]

Among the above-mentioned known techniques, the techniques (1) and (2) are for superimposing other additional information on a digital image. This is done, not for hardcopy output. Moreover, complicated signal processing and arithmetic processing are required to extract the superimposed additional information, and it is difficult to easily reproduce the additional information. Further, although it is possible to combine an image created by these methods with hard copy recording, by performing recording and reading operations, the superimposed additional information is significantly deteriorated and it is difficult to restore the additional information. is there.

The techniques (3) and (4) are intended for hard copy images, but in order to reproduce the superimposed additional information, it is necessary to read the image and perform signal processing and calculation. However, it is still difficult to easily reproduce the superimposed additional information.

In the technique (5), the information can be easily reproduced by stacking sheets on the recorded matter, but this is a random image by itself, and another information is superimposed on a significant image. It cannot be used for doing.

In the technique (6), the two images to be superposed are paired, and the information cannot be reproduced unless the unpaired images are superposed. That is, if information is to be reproduced for a plurality of images, it is necessary to prepare images corresponding to the number of images.

The present invention provides an image recording apparatus for recording an image superimposed on a hard copy so as to be reproduced by a simple operation which does not require complicated signal processing, and an image recording apparatus for reproducing the superimposed recorded image. An object is to provide an image reproducing device.

[0014]

To solve the above problems, the present invention superimposes a pattern-modulated image signal obtained by modulating a predetermined pattern image signal with an image to be additionally recorded on the original image. The essence is that the image thus recorded is reproduced and the image thus recorded is reproduced in correspondence with the pattern of the pattern image signal.

That is, the image recording apparatus according to the present invention is
A pattern image generating means for generating a predetermined pattern image signal, a modulating means for modulating the pattern image signal with a first image signal to generate a pattern modulated image signal, and a pattern modulating image signal for the second pattern image signal. It is characterized by comprising superimposing means for superimposing on the image signal and recording means for recording the image by inputting the image signal output from the superimposing means.

Further, the image recording apparatus according to the present invention further comprises a smoothing means for smoothing the first image signal, and a pattern image signal is formed by the first image signal smoothed by the smoothing means. It may be modulated.

An image recording apparatus according to one aspect of the present invention is a pattern image generating means for generating a pattern image signal in which gain values given to a predetermined color difference amount for each pixel are arranged in a predetermined pattern, and this pattern. Modulation means for generating a pattern-modulated image signal by modulating the image signal with the first image signal, and a second image signal composed of a color image signal after the pattern-modulated image signal is multiplied by the predetermined color difference amount. And a recording means for recording the image by inputting the image signal output from the superimposing means.

An image recording apparatus according to another aspect of the present invention is
Pattern image generating means for generating a pattern image signal in which gain values given to a predetermined color difference amount for each pixel are arranged in a predetermined irregular pattern, and the pattern image signal is modulated by the first image signal. Modulation means for generating a pattern modulation image signal, conversion means for converting the pattern modulation image signal into an ink density signal, and superposition for superimposing the pattern modulation image signal on the second image signal by an error diffusion method according to the ink density signal. It is characterized by comprising means and recording means for recording an image by inputting the image signal output from the superposing means.

In the image reproducing apparatus according to the present invention, an image signal in which a pattern-modulated image signal obtained by modulating a predetermined pattern image signal with the first image signal is superimposed on the second image signal is recorded as an image. An image reproducing apparatus for reproducing a first image as a visible image from a recorded matter, which is configured by arranging a sheet having a transmittance distribution of the same pattern as a pattern of a pattern image signal on the recorded matter. .

In another image reproducing apparatus according to the present invention, an image signal in which a pattern-modulated image signal obtained by modulating a predetermined pattern image signal with a first image signal is superimposed on a second image signal is an image. Is an image reproducing apparatus for reproducing a first image as a visible image from a recorded matter recorded as, wherein an optical element having a thickness distribution of the same pattern as the pattern of the pattern image signal is arranged on the recorded matter. To be done.

As described above, according to the present invention, the pattern-modulated image signal obtained by modulating the predetermined pattern image signal with the first image signal to be superimposed and recorded is superimposed on the second image signal and recorded as an image. To do. In this case, as the predetermined pattern image, for example, by using a visually difficult-to-see pattern such as a high spatial frequency color difference pattern in which gain values given to a predetermined color difference amount for each pixel are arranged in a predetermined pattern, The image information is almost invisible visually and does not impair the quality of the second image which is the current image.

By superimposing a sheet or an optical element having a transmittance distribution or a thickness distribution corresponding to a predetermined image pattern on the recorded matter thus recorded, the second image is visualized and a complicated signal is displayed. The second image can be reproduced easily without requiring any processing.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) A first embodiment in which the present invention is applied to an image synthesizing recording / reproducing apparatus will be described below. The present device is a device for combining two images, recording and reproducing them. More specifically, the composition of the two images is performed by embedding the first image in the second image. Then, when a human observes the recorded composite image by a normal method, it looks almost like the second image and the first image cannot be seen, and the first image is reproduced only by a special device or method. Make it visible. In the following description, for the sake of convenience, performing image synthesis in this manner is referred to as "embedding" the first image in the second image, and the first image is referred to as "embedding image".
Each of the second images will be referred to as an "embedded image". Further, the operation of making the embedded image visible to humans is expressed as “reproducing”.

FIG. 1 shows the arrangement of an image composition / recording apparatus according to this embodiment. This image synthesizing recording device is a CPU 10
1, an image memory 102, an image input unit 103, a program memory 104, and an image recording unit 105, all of which are connected by a bus 106. CPU10
1, the image memory 102, the image input unit 103, and the program memory 104 constitute an image processing unit 107.

The operation of the image synthesizing / recording apparatus will be briefly described. First, the embedding image and the embedding image are respectively written in predetermined areas of the image memory 102 through the image input unit 103. Then, based on the algorithm shown below, these images are subjected to calculation processing to create a composite image, and the composite image is recorded in the image recording unit 105 as a color hard copy.

The series of processes are all performed by the CPU 10 according to the program stored in the program memory 104.
It is performed by 1. Although a dedicated device may be used for the processing, a general-purpose computer such as a personal computer may be used. In this case, the image memory 102 and the program memory 104 generally use the same memory in divided areas.

Next, the configurations of the embedding image and the embedding image, which are the input images of this apparatus, and the content and meaning of the image processing will be described in detail.

The input image is usually expressed as digital information in which density is defined on each grid point of the Cartesian coordinate system, as in the case of being used for expression in a computer. Here, the two axes of the Cartesian coordinate system are the x-axis and the y-axis.
Expressed as vertical.

In this embodiment, the embedded image is a monochrome binary image such as a figure or a character. The density value of the pixel (x, y) is represented as R (x, y). On the other hand, a full-color image is used as the embedded image, and the pixel values of the R, G, and B color components are represented by Pr (x, y), Pg (x, y), and Pb (x, y). These pixel values are Pr = 0, Pg = 0, Pb =
The case of 0 represents black, and the case of Pr = 1, Pg = 1, Pb = 1 represents white.

Next, the image processing algorithm in this embodiment will be described in detail. The processing procedure is shown in the flowchart of FIG.

[First Step (Pattern Generation)] First,
In the first step S11, a pattern image Q (x, y) is generated. The pattern image is an image that is modulated by the embedded image and superimposed on the embedded image, and is preferably an image with a high spatial frequency that is difficult for human eyes to perceive.

In this embodiment, the pattern image Q (x,
As y), a checkerboard pattern image as shown in FIG. 3 is used. Here, each pixel of the pattern image Q (x, y) is represented by a numerical value of 1 or -1, but the physical meaning thereof is a predetermined color difference amount (Vr, Vg, V) for each pixel.
It is a gain given to b). Such a pattern image Q
(X, y) is called a color difference pattern image. The pattern image Q (x, y) shown in FIG. 3 is a pattern image in which pixels having a gain of 1 and a gain of -1 are arranged in a checkered pattern with (4 × 4) pixels as a unit. Shown in.

If (int (x / 2) + int (y / 2)) mod2 = 0, then Q (x, y) = − 1 (int (x / 2) + int (y / 2)) mod2 = 1 Q (x, y) = 1 (1) where int (x) is an operation that takes the integer part of x, x
mod y is an operation representing the remainder when x is divided by y. This pattern image Q (x, y) has no DC component.
Thus, an image having a low low-frequency component is small, that is, an image having a high spatial frequency.

[Second Step (Pattern Modulation)] Next,
In the second step S12, the pattern image Q (x, y) is modulated by the embedded image R (x, y). At this time, first, the embedded image R (x, y) is processed by a smoothing filter according to the equation (2) to obtain a smoothed embedded image R '(x, y).

[0035]

[Equation 1]

However, xi, yi and Ai represent kernels of the smoothing filter. In this embodiment, a smoothing filter of (5 × 5) pixels having a kernel as shown in FIG. 4A is used. That is, −2 ≦ xi, yi ≦ 2, and A
(Xi, yi) = 1/25.

The smoothed embedded image R '(x, y) is used to modulate the pattern image Q' (x, y) according to the equation (3) to obtain the pattern modulated image Q '(x, y).

Q ′ (x, y) = Q (x, y) · (−2 · R ′ (x, y) +1) (3) By this processing, a pattern-modulated image Q ′ (x, y) is obtained. In the area of R ′ = 1, the pattern image Q (x, y) of −
An image obtained by inverting the pattern image Q (x, y) is obtained, and in the region of R ′ = 0, the pattern image Q (x, y) is obtained.
y) itself becomes the pattern modulation image. R'is 1 and 0
In a region having a value between, the pattern modulation image Q ′ (x,
y) is an intermediate value between them. Since R'is a smoothed signal, it is between 1 and 0 in the edge region of the embedded image R (x, y). Therefore, by the above processing, an image in which the polarity of the amplitude is inverted according to the pixel value of the embedded image R (x, y) and the amplitude changes gently at the edge portion is obtained as the pattern modulation image Q ′ (x, y). To be

FIG. 5 shows an embedded image R (x, y), a smoothed embedded image R '(x, y), and a pattern image Q (x, y).
And the pattern-modulated image Q '(x, y).
However, in FIG. 5, for convenience, the image is represented in one dimension.

In the above description, the pattern image Q (x,
Amplitude modulation is applied to y) by the smoothed embedded image R ′ (x, y), but as another example, phase modulation represented by formula (4-1) may be used.

Q ′ (x, y) = Q (x + g (R ′ (x, y)), y) (4-1) where g (x) is 0 when x = 0 and x = 1 When the phase modulation is performed in this way, the pattern image Q (x, y) is shifted by 4 pixels in the x-axis direction in the region of R ′ = 1. However, in the region of R ′ = 0, the pattern image Q (x, y) itself becomes the pattern modulation image Q ′ (x, y). Since the pattern image Q (x, y) is an x-axis symmetric periodic image having a period of 4 pixels, a shift of 4 pixels and −1 times the amplitude have the same meaning. Therefore, the processing result by the phase modulation and the processing result by the amplitude modulation described above are equivalent in the portion where R'is 0 and 1, and the embedded image R in which the value of R'is an intermediate value.
Only the edge part of (x, y) is different. In this phase modulation processing, an image in which the phase changes gently at the edge portion can be obtained.

FIG. 6 shows an embedded image R (x, y), a smoothed embedded image R '(x, y), and an embedded image R (x, y) in the case of this phase modulation processing.
Pattern image Q (x, y) and pattern modulation image Q '
It is the figure which represented the relationship of (x, y) in one dimension similarly to FIG.

Although the above description is an example of phase modulation in the x-axis direction, phase modulation in the y-axis direction may be performed as shown in equation (4-2).

Q ′ (x, y) = Q (x, y + g (R ′ (x, y))) (4-2) Smoothing of the embedded image R (x, y) is shown in FIG. The smoothing is not limited to the two-dimensional reference region of (5 × 5) pixels which is symmetrical in the vertical and horizontal directions. For example, FIG.
As shown in (c) and (d), the reference area may be a vertically and horizontally asymmetric rectangle, a one-dimensional rectangle, or a non-rectangular shape. Furthermore, weighted smoothing as shown in FIG. Especially,
When this processing is performed by pipeline-type hardware described later, it is possible to reduce the circuit cost by performing smoothing by a method such as that shown in FIGS. 4B and 4C that can be configured with a line memory having a small capacity.

[Third Step (Pattern Superimposition)] Next,
In the third step S13, the pattern modulation image Q '(x, y)
Is superimposed on the embedded image. In this embodiment, a simple addition operation is performed as this superposition processing. As described above, the pattern image Q (x, y) has the color difference amount (Vr, Vg,
Since it is a gain given to Vb), the embedded image is Pi
(X, y) (i = r, g, b), the pattern-modulated image Q ′ (x, y) is multiplied by the color difference amount (Vr, Vg, Vb), and then the embedded image is Pi (x, y). Add to. Here, the color difference amounts (Vr, Vg, Vb) are set so that the lightness becomes 0 or approximately 0 and the intensity becomes approximately equal to or lower than the human visual limit. For example, (Vr, Vg, Vb) = (0.2,
The value of 0.2, -0.4) is used. This will be described in detail later. If the addition result exceeds the definition range (0, 1) of the density value, clipping is performed at the minimum value or the maximum value of the definition range.

The superimposition processing in the third step S13 is shown in equation (5). However, the pattern superposed image which is the superposition result is represented as Oi (x, y) (i = r, g, b).

Or (x, y) = Pr (x, y) + Q ′ (x, y) · Vr Og (x, y) = Pg (x, y) + Q ′ (x, y) · Vg Ob (x , Y) = Pb (x, y) + Q ′ (x, y) · Vb If Or (x, y) ≧ 1, Or (x, y) = 1 If Or (x, y) <0 , Or (x, y) = 0 Og, Ob (5) [Fourth step (color correction)] Next, fourth step S14
, The ink amount signals OC, used for controlling the ink amounts of the three colors C, M, Y in the image recording unit 105 of the pattern superimposed image Oi (x, y) represented by the RGB color components.
Convert to OM and OY. This conversion has been widely known as a color correction technique. Here, the formula (6-1)
Color correction processing is performed according to (6-2). Matrices Acr, Acg, Acb, Amr, Am in Expression (6-1)
g, Amb, Ayr, Ayg, Ayb are image recording units 1
The value depends on the chromaticity of each ink used in No. 05, and is selected as a value suitable for the image recording unit 105.

[0048]

[Equation 2]

If the processing is performed on the YMC basis from the beginning, the processing of the fourth step S14 can be omitted.

The above is a series of image combining processes in the present embodiment. After this process, the image recording unit 105 records a color image as a hard copy according to the ink amount signals OC, OM, and OY. As a result, a color image having substantially the same RGB components as the pattern-superimposed images Or ', Og', Ob 'is recorded on a predetermined recording material (recording paper). As the image recording unit 105, for example, a sublimation type thermal transfer printer is used. Sublimation type thermal transfer method has 1 for each pixel
It is possible to control the density over 100 gradations and easily perform full-color recording.

In addition to this, for example, a silver salt photographic system may be used for the image recording unit 105, or a recording system suitable for binary recording such as an inkjet system or a fusion type thermal transfer system may be used. However, when a binary recording printer is used, it is necessary to perform a pseudo gradation process such as an error diffusion method or a tissue dither method in order to express gradation. When these processes are performed, image information of high spatial frequency close to the recording density of the printer is disturbed or missing, so it is necessary to use a recording system having a recording density sufficiently higher than the spatial frequency of the pattern image.

In the above description, the series of image synthesizing processing is realized by software processing, but it is also possible to realize by hardware.

FIG. 7 shows the configuration of an image synthesizing / recording device that implements the series of image synthesizing processes described above by hardware.
The image processing unit stores the embedded image and the embedded image 2
Image memories 701 and 702, a pattern generation unit 70
3, pattern modulation unit 704 and pattern superposition unit 705
And the image recording unit 706 is combined with them to form an image synthesizing recording device.

First, for example, a color difference pattern image signal 753 is generated as a pattern image signal from the pattern generator 703. Then, in the pattern modulator 704, the first
Embedded image signal 75 output from the image memory 701 of
1 according to the formula (4)
The pattern modulation image signal 754 is generated by performing the phase modulation represented by 1) or (4-2).
Next, the pattern superimposing unit 705 superimposes the pattern modulated image signal 754 on the embedded image signal 752 output from the second image memory 702 to generate the pattern superposed image signal 755. Then, the pattern superimposed image signal 755 is supplied to the ink amount signal 756 by the color correction unit 706.
After being converted to, the image is input to the image recording unit 707 and a hard copy image is output.

The operation of the image synthesizing / recording apparatus will be described in more detail. First, the first and second image memories 70 are provided.
An embedded image R (x, y) and an embedded image P (x, y) are stored in reference numerals 1 and 702, respectively. The embedded image R (x, which is stored in the first image memory 701
y) is a binary image and is represented by 1 bit per pixel. The embedded image P (x, y) stored in the second image memory 701 is a full-color image of 8 bits each for RGB, and is represented by a total of 24 bits per pixel.

The pattern generator 703 generates a pattern image signal 753. The pattern image is the color difference pattern image signal as described above, and is generated according to the equation (1).

The pattern modulator 704 includes, for example, three line memories 711, a group of 15 latches 712, and an adder 7.
13 and two multipliers 714 and 715. First
Embedded image signal 75 output from the image memory 701 of
1 is delayed by the line memory 711 and the latch group 712. Each latch output of the latch group 712 is a signal in a rectangular area of (5 × 3) pixels, and after these are added by the adder 713, they are input to the first multiplier 714 and multiplied by the pattern image signal 753. To be This first multiplier 71
For the multiplication output of 4, the second multiplier 715 outputs 3
The two parameter sets Vr, Vg, Vb are multiplied. Here, the signal of one pixel is multiplied three times,
The pattern superimposing unit 706 outputs the result of these three multiplications as a pattern-modulated image signal 754 composed of time-series RGB signals.
Output to

The pattern superimposing unit 706 comprises an adder 716 and a clipping circuit 717. First, the adder 716
Thus, the embedded image signal 752 from the second image memory 702 is added to the pattern modulated image signal 754 from the pattern modulator 704. Pattern modulated image signal 75
4 and the embedded image signal 752 are RGB time-series signals, and the adder 716 adds the same components. The addition result of the adder 716 is clipped by the clipping circuit 717 and output as the pattern superimposed image signal 755. That is, the clipping circuit 717 outputs 0 when the addition result of the adder 716 is smaller than 0 and outputs 25 when it is larger than 255.
Perform the operation of 5.

The pattern-superimposed image signal 755 output from the pattern superimposing unit 705 is a signal having three color components of RGB, and is converted by the color correcting unit 706 into an ink amount signal 756 representing the ink amount in the image recording unit 707. It The color correction unit 706 uses, for example, a look-up table.
This table is calculated in advance according to equations (6-1) and (6-2) and stored in the memory.

As described above, it is possible to easily realize the above-mentioned image synthesizing process also by hardware. Since the signal processing can be performed at a relatively high speed by using hardware, it is particularly effective when a large number of images are created in a short time.

Next, the property of the composite image (pattern superposed image) of the embedded image and the embedded image recorded by the above processing will be described. This composite image is an image that looks almost the same as the embedded image, and the information of the embedded image is information that is hardly visible or almost invisible.

The RGB color components of the embedded image are set to Pr (x,
y), Pg (x, y), Pb (x, y), the embedded image is R (x, y), and the smoothed embedded image is R '(x, y).
(= R (x, y) * LPF (x, y)), the RGB components Or (x, y), Og (x, y), O of the composite image
b (x, y) is represented by Expression (7).

Or (x, y) = Pr (x, y) + Q (x, y) .Vr. (-2.R '(x, y) +1) Og (x, y) = Pg (x, y) ) + Q (x, y) · Vg · (−2 · R ′ (x, y) +1) Ob (x, y) = Pb (x, y) + Q (x, y) · Vb · (−2 · R) ′ (X, y) +1) (7) Next, the lightness component O of the composite image recorded in this way is recorded.
Consider y and the color difference component Oc. Here, the lightness component O
y and the color difference component Oc are defined by equation (8).

Oy (x, y) = Kr.Or (x, y) + Kg.Og (x, y) + Kb.Ob (x, y) Oc (x, y) = Or (x, y) -Og ( x, y) (8) The lightness component Oy represents brightness and the color difference component Oc represents color intensity. The color difference component Oc includes two independent types of components, but only one component is handled here. (Kr,
Kg, Kb) is a coefficient representing the brightness of each of the RGB components, and (Kr, Kg, Kb) = (0.18, 0.8)
1, 0.01).

Spectra Foy (fx, fy), Foc (fx, f) of the lightness component Oy and the color difference component Oc
y) is represented by Formulas (9-1) and (9-2).

Foy (fx, fy) = Fpy (fx, fy) + Vy · Fq (fx, fy) * (− 2Fr ′ (fx, fy) + δ (fx, fy)) (9-1) Foc (fx, fy) fy) = Fpc (fx, fy) + Vc · Fq (fx, fy) * (− 2Fr ′ (fx, fy) + δ (fx, fy)) (9-2) where fx and fy are respectively in the x-axis direction, It represents the spatial frequency in the y-axis direction. In addition, Fr ', Fq, Fpy, Fpc
Are smoothed embedded image R ′, pattern image Q,
It is a Fourier transform of the lightness component and the color difference component of the embedded image P. Further, Vy and Vc are the lightness component and the color difference component of the color difference amount described above.

Here, since the lightness component Vy of the color difference amount V is set to 0 or sufficiently close to 0, the expression (9-
The second term of 1) becomes 0 or almost 0.

8 (a), (b), (c) and (d) are expressed by the equation (9)
-2) It is the figure which represented typically Fpc, Fr ', Fq, and Foc above. Spectrum F of the color difference component of a normal image
In pc (fx, fy), the power is concentrated in the low frequency component as shown in FIG. 8A, and the high frequency component is extremely low. On the other hand, in the smoothed embedded image R ′ as shown by the solid line in FIG. 8B, the high frequency components of the embedded image R are deleted as shown by the broken line. The pattern image Q is shown in FIG.
As shown in (c), it has only high frequency components. Therefore,
As shown in FIG. 8D, the spectrum of the color difference component of the composite image represented by the equation (9-2) is separated into the first term centered on the low frequency component and the second term centered on the high frequency component. To be done.

Further, as shown in FIG. 9 (cited from FIG. 1.76 in Chapter 3 of Television Image Engineering Handbook, Vol. 1, Chapter 3), it is known that human visual characteristics have low sensitivity especially for color difference components at high frequencies. Has been. Therefore, the formula (9-
The second term of 2) is almost invisible to humans. Therefore, in the composite image, only the first term of Expression (9) is observed for both the lightness component and the color difference component. That is, the composite image looks equal to the embedded image.

As described above, the image synthesized and recorded by this embodiment is almost the same as the image to be embedded visually, and the component of the embedded image is the color difference component of high spatial frequency, so that it is almost visible. Disappear. Also, the color difference component Fp1 (f
Since the high frequency component of (x, fy) decreases, there is no component that shifts to a low frequency due to the convolution of the embedded image and the pattern image.

Next, the reproducing apparatus for reproducing the embedded image from the composite image recorded as described above will be specifically described.

FIG. 10 is a diagram showing an example of the structure of the reproducing apparatus. Recorded material (recording paper) 110 on which a composite image is recorded
0 is loaded and fixed on the reproducing apparatus main body 1000 so that the upper end and the right end of the recorded material 1100 contact the upper end 1001 and the right end 1002 of the loading section of the reproducing apparatus main body 1000. As a result, the reproduction sheet 1003 and the image on the recorded material 1100 are held in a predetermined positional relationship. Then, the reproduction sheet 1003 connected to the reproduction apparatus main body 1000 is overlaid on the recorded matter 1100, and the image on the recorded matter 1100 is observed through this sheet 1003, so that the embedding image overlaps the embedding image. It is configured to be visible.

The reproducing apparatus is not limited to the structure shown in FIG. 10, and may have any structure as long as the relative position between the composite image on the recorded material 1100 and the reproducing sheet 1003 can be fixed. In addition, the reproduction sheet 1003 is recorded on the recorded matter 11
Instead of being fixed to 00, the sheet 1003 may be freely moved by one-dimensional or two-dimensional movement so that the sheet 1003 is adjusted to a position where the embedded image on the recorded matter 1100 is to be reproduced. Further, if the gap between the reproduction sheet 1003 and the recorded material 1100 is large, the reproduction contrast of the embedded image becomes low. Therefore, the reproduction sheet 1003 is pressed from above by a rigid transparent plate so that the gap is within 1 mm. It may be structured.

Next, the structure of the reproducing sheet 1003 and the principle of reproducing the embedded image will be described. Recycling sheet 1
003 is made of a transparent film-like thin medium such as plastic, and a predetermined pattern is formed on the medium.

The pattern on the reproduction sheet 1003 is the pattern at the time of creating the composite image, that is, the pattern of the pattern image generated in the first step S11 of FIG. 2 (the pattern generated by the pattern generation unit 703 of FIG. 7). An image having a suitable transmittance distribution corresponding to the image pattern) is used. The RGB transmittance distributions Tr (x, y), Tg (x, y), and Tb (x, y) of the reproducing sheet 1003 are shown in equation (10). Here, (Wr0, Wg0, Wb
0) and (Wr1, Wg1, Wb1) represent the RGB transmittances of the pixels having the corresponding pattern image Q (x, y) values of 1 and −1, respectively, and in the present embodiment, equation (11) is used.
As shown in -1), two colors of white (transparent) and black are used.

Tr (x, y) = 0.5 (Wr0−Wr1) · Q (x, y) +0.5 (Wr0 + Wr1) Tg (x, y) = 0.5 (Wr0−Wg1) · Q ( x, y) +0.5 (Wr0 + Wg1) Tb (x, y) = 0.5 (Wr0-Wb1) * Q (x, y) +0.5 (Wr0 + Wb1) (10) (Wr0, Wg0, Wb0) = (0,0,0) (Wr1, Wg1, Wb1) = (1,1,1) (11-1) FIG. 11 shows the transmittance distribution pattern of the reproducing sheet 1003. In the figure, W represents a transparent portion and K represents an opaque portion. The W and K portions respectively correspond to the gain -1 and gain 1 pixels of the pattern image Q (x, y) shown in FIG. . By stacking the reproducing sheet 1003 having such a transmittance pattern on the recorded matter 1100, the pattern on the sheet 1003 and the recorded matter 1100 can be obtained.
Interference with the component of the pattern image Q (x, y) of the above composite image occurs, and the embedded image is yellow / superposed on the embedded image.
Observed as a blue color difference image.

As another example of the reproducing sheet 1003, the structure in which the portions W and K in FIG. 11 are replaced with the portions for transmitting the colors Y and B, respectively, as shown in equation (11-2), is very good. . In this case, the embedded image is observed as a monochrome gray-scale image superimposed on the embedded image.

(Wr0, Wg0, Wb0) = (1,1,0) (Wr1, Wg1, Wb1) = (0,0,1) (11-2) Such a reproducing sheet 1003 has the above-mentioned image. It may be created by the recording system of the synthesizing recording device, or may be created by a completely independent recording system. However, since the recording density may differ depending on the recording system, it is easier to obtain the accuracy when the reproducing sheet 1003 is created by the same recording system as the image composition recording apparatus.

The reproduction sheet 1003 described above is used as the recorded material 1
When overlaid on 100, the high-frequency color difference information embedded as an embedded image shifts to the low-frequency region and becomes visible to the human eye. Hereinafter, this reason will be specifically described.

RGB reflectances Or, Og, Ob of the composite image
Is represented by the above-mentioned formula (7). Therefore, recorded matter 11
Letting Sr, Sg, and Sb be the RGB reflectances of the image observed by stacking the reproduction sheet 1003 on 00, these are expressed by equation (12). However, since the G component and the B component are the same as the R component, they are omitted.

Sr = Or.Tr = Pr (x, y) .Tr (x, y) + Q (x, y) .Vr. (-2.R '(x, y) +1) .Tr (x, y) ) = Pr (x, y) * Tr (x, y) + Q (x, y) * Vr * (-2 * R '(x, y) +1) * (0.5 (Wr0-Wr1) * Q ( x, y) + (0.5 (Wr0 + Wr1)) = Pr (x, y) .Tr (x, y) + 0.5.Vr. (Wr0-Wr1) .Q (x, y) ^2. (- 2 * R '(x, y) +1) + 0.5 * Vr * (Wr0 + Wr1) * Q (x, y) * (-2 * R' (x, y) +1) = Pr (x, y) * Tr (x, y) + 0.5.Vr. (Wr0-Wr1). (-2.R '(x, y) +1) + 0.5.Vr. (Wr0 + Wr1) .Q (x, y). (- 2 · R '(x, y) +1) Same for g and b components (12) Here, schematic diagrams of the spectral distributions of the first term, the second term, and the third term of the equation (12) are shown in FIGS. 12 (a), (b), and (c), respectively. It is an image equivalent to an image in which the reproduction sheet 1003 is overlaid on the embedded image itself, and the third term is a high-frequency color difference component, which is not visually visible, while the second term is the chromaticity of the embedded image. (Vr.
(Wr0-Wr1), Vg · (Wg0-Wg1), Vb
(Wb0-Wb1)). In the present embodiment, this is a color difference component, but since it is demodulated to the same frequency as the embedded image, it becomes a visible image. Therefore, an image obtained by adding the image of which the chromaticity is modulated by the embedded image to the embedded image which is the first term is observed.

When the sheet having the pattern represented by the formula (11-2) is used as the reproducing sheet 1003, (Vr. (Wr0-Wr1), Vg. (Wg0-
Since Wg1) and Vb · (Wb0-Wb1)) are monochrome components, an image obtained by adding the pattern-modulated image whose density is modulated with the embedded image to the embedded image is observed.

As described above, according to the image synthesizing / recording apparatus of the present embodiment, a synthetic image which is visually similar to the embedding image and in which another image (embedding image) is embedded without image quality deterioration is recorded. Further, by superimposing a predetermined reproducing sheet on the recorded matter on which the composite image is recorded, the embedded image can be easily visually recognized without requiring complicated signal processing. It becomes possible to reproduce.

(Second Embodiment) Next, a second embodiment of the present invention will be described. In the first embodiment, a regular pattern is used as the pattern image and the reproducing sheet, but the present embodiment is different in that an irregular pattern is used. The basic configuration of the image synthesis recording apparatus according to this embodiment is the same as that of the first embodiment, but the processing procedure is slightly different.

The processing procedure of the image synthesizing recording apparatus according to the second embodiment will be described below with reference to the flowchart shown in FIG. 13, focusing on the differences from the first embodiment.

[First Step (Pattern Generation)] First,
In the first step S21, a pattern image Q (x, y) is generated. In the first embodiment, the pattern image Q (x, y)
Is a pattern image having a regular structure, but in the present embodiment, an irregular pattern image or an enlarged image thereof is used.

As the irregular pattern image, (1) the direct current component and the low frequency spectrum are 0, the intensity of the high frequency component is strong, and (2) the structure of the pattern image cannot be easily estimated from the embedded image. It is desirable to meet two conditions. In the present embodiment, as shown below, 2
An irregular pattern image is generated by a three-dimensional Markov stochastic process. That is, the transition probability Prob is defined as a function f of the already determined pixel value Q (x + axi, y + ayi) around the target pixel (x, y), and the value of the pattern image Q (x, y) is set to 1 with this probability Prob. Or decide to -1. This is shown in equation (13). However, Prob [Q (x,
y), a] is the probability that Q (x, y) = a.

Prob [Q (x, y), 1] = f (Q (x + axi, y + ayi)) Prob [Q (x, y), − 1] = 1−f (Q (x + axi, y + ayi)) (13 ) By repeating this process while appropriately scanning (x, y), a binary irregular pattern image Q (x, y)
Generate all images of. The function f used in this embodiment is shown in Expression (14).

[0089]

(Equation 3)

14A and 14B show the autocorrelation function and power spectrum of the binary irregular pattern image Q (x, y) thus generated. However, in FIG. 14, only the component in the x-axis direction is shown for simplicity. As shown in the figure, the pattern image Q (x, y) is an image in which the power is almost 0 at low spatial frequencies and the power is concentrated at high frequencies.

Here, in order to generate a probability image on a computer, a pseudo random number such as M series is used. That is, a pseudo random number D that takes a value in the range of 0 to N-1 with a uniform probability.
Is generated for each pixel, and the value of the pattern image Q (x, y) is determined by the equation (15).

If D / N ≧ Prob, Q (x, y) = 1 If D / N <Prob, Q (x, y) = − 1 (15) In this case, only the pseudorandom seed and the function f are stored. If so, the same pattern image can be generated uniquely, and it becomes unnecessary to store the pattern image Q (x, y) itself.

In the above description, the pattern image Q (x,
Since y) is generated by the Markov process, the amount of calculation becomes large. Therefore, using the random number directly, the pattern image Q
The pixel value of (x, y) may be determined. Alternatively, a pattern generated by the error diffusion process may be used. The former becomes white noise, and its DC component and low frequency components do not necessarily have small values, but the pattern image Q (x, y)
The calculation of is very simple. Further, in the latter case, the low frequency component becomes small and the image can be calculated deterministically, so that the random number generation process is not necessary.

[Second Step (Pattern Modulation)] [Third Step (Pattern Superposition)] [Fourth Step (Color Correction)] Next, second step S22,
In the third step S23 and the fourth step S24, the pattern modulation, the pattern superposition, and the color correction are sequentially performed, and the finally obtained composite image is recorded. However, these processes are the same as those in the first embodiment. , Description is omitted. However, since the pattern is irregular and has no periodicity,
In the pattern modulation processing, the phase modulation based on the periodic pattern as exemplified in the first embodiment is not used.

By the above processing, a composite image in which the embedded image and the embedded image are combined is recorded. Similar to the first embodiment, this composite image is an image that looks almost the same as the embedded image, and the information of the embedded image is information that is hardly visible or almost invisible.

Next, the properties of the composite image obtained in this embodiment will be described in detail. Each RGB color component Or (x, y), Og (x, y), Ob (x, y) of the composite image and its lightness component Oy (x, y) and color difference component Oc (x,
y) is represented by the equations (7) and (8) as in the first embodiment. Also, the brightness component Oy (x, y) and the color difference component Oc
(X, y) spectrum Foy (fx, fy), Foc
(Fx, fy) is represented by equations (9-1) and (9-2). Only the content of the spectrum Fq of the pattern image Q (x, y) is different from that of the first embodiment.

As in the first embodiment, the lightness component VY of the color difference amount V is set to 0 or sufficiently close to 0, so the second term of the equation (9-1) becomes 0. Also, FIG.
Since Fq is also designed to have a low low-frequency component as shown in FIG. 4, the second term of the equation (9-2), which is a convolution of Fq and Fr + δ, becomes an extremely weak signal of a low-frequency component. That is, the expression (9-
The contribution of the second term of 2) is extremely small. As previously mentioned,
Since the high-frequency color difference component has low visual sensitivity, almost only the component of the first term, that is, the embedded image is observed in the composite image.

FIGS. 15 (a), 15 (b), 15 (c) and 15 (d) show the spectral distributions of Fpc, Fr ', Fq and Foc of the equation (9-2).

Since the low frequency component of Fq is not completely 0 in this embodiment, the embedded image R is different from that in the first embodiment.
Although the contribution of (x, y) to low frequency components is large,
Since the low-frequency component of the irregular pattern that is the pattern image Q (x, y) to be created can be controlled by the function f, it can be designed so as not to be seen sufficiently by setting this appropriately. On the other hand, since the disorder of the regular pattern is easily detected, the pattern image Q (x,
This effect is reduced by using an irregular pattern for y).

Next, a method of reproducing the embedded image from the composite image recorded in the second embodiment will be described. Also in this embodiment, the embedded information is reproduced by the same method as in the first embodiment. However, as the reproducing sheet 1003, unlike the first embodiment, a sheet having the same structure as the pattern image used in the image combining and recording apparatus of the second embodiment is used.

Reproduction sheet 1003 used in this embodiment
RGB transmittance distributions Tr (x, y), Tg (x, y),
Equation (16) shows Tb (x, y). This has the same form as the equation (10) shown in the first embodiment, but the contents are different because the pattern image Q (x, y) is different.

Tr (x, y) = 0.5 (Wr0−Wr1) · Q (x, y) +0.5 (Wr0 + Wr1) Tg (x, y) = 0.5 (Wg0−Wg1) · Q ( x, y) +0.5 (Wg0 + Wg1) Tb (x, y) = 0.5 (Wb0−Wb1) · Q (x, y) +0.5 (Wb0 + Wb1) (16) Further, the parameters Wr0, Wr1, Wg0, Wg1, W
The values of b0 and Wb1 and their modified examples are expressed by equation (17-1).
It is shown in (17-2).

(Wr0, Wg0, Wb0) = (0,0,0) (Wr1, Wg1, Wb1) = (1,1,1) (17-1) (Wr0, Wg0, Wb0) = (1,1 , 0) (Wr1, Wg1, Wb1) = (0, 0, 1) (17-2) Similar to the first embodiment, such a reproduction sheet 10 is used.
As shown in FIG. 10, when 03 is overlapped on the recorded matter 1100, patterns interfere with each other, and the embedding image is observed as a yellow / blue color difference image superimposed on the embedding image.

Next, the principle of reproducing an embedded image in this embodiment will be described. Composite R when a reproduction sheet 1003 is overlaid on a recorded matter on which a composite image is recorded
If the GB reflectances are Sr, Sg, and Sb, these are the first
The same as the embodiment of FIG. Also in this embodiment, since Q (x, y) ² is always 1, Sr (x, y) is represented by the equation (18) as in the equation (12).

Sr = Or * Tr = Pr (x, y) * Tr (x, y) + 0.5 * Vr * (Wr0-Wr1) * (-2 * R '(x, y) +1) +0.5 * Vr * (Wr0 + Wr1) * Q (x, y) * (-2 * R '(x, y) +1) (18) The 1st of Formula (18) is shown to FIGS. The spectral distributions of the term, the second term, and the third term are shown. Similar to the first embodiment, the first term is an image equivalent to an image in which the reproduction sheet 1003 is overlaid on the embedded image itself, and the third term is a high-frequency color difference component, and is not visually visible. . On the other hand, the second term is the chromaticity (Vr · (Wr0-Wr
1), Vg · (Wg0-Wg1), Vb · (Wb0-W
b1)) is multiplied, and it becomes a visible image.
Therefore, an image in which the image of which the chromaticity is modulated by the embedded image is added to the embedded image which is the first term is observed.

Further, as the reproducing sheet 1003, the formula (1
When a sheet having a pattern represented by 1-2) is used, (Vr · (Wr0−Wr1), Vg · (Wg0−W)
Since g1) and Vb · (Wb0−Wb1)) are monochrome components, an image obtained by adding the image of which the density is modulated by the embedded image to the embedded image is observed.

As described above, also in the present embodiment, as in the first embodiment, a composite image which is visually almost the same as the embedding image and in which another image (embedding image) is embedded without deterioration in image quality is obtained. Can be recorded. Furthermore, by superposing a predetermined reproduction sheet on the recorded matter on which the composite image is recorded, reproduction can be easily visually recognized without requiring complicated signal processing.

The present embodiment further has the following advantage, which is not provided in the first embodiment, because it is difficult to estimate the pattern of the embedded image from the composite image because an irregular pattern image is used as the pattern image. It becomes difficult for a third party to estimate the pattern information from the composite image and create a composite image independently or reproduce the embedded image. Therefore, the present embodiment is suitable for an application that allows only a specific person to synthesize and reproduce images.

(Third Embodiment) Next, a third embodiment according to the present invention will be described. In the first and second embodiments, the embedding of the pattern-modulated image is performed by the addition process, whereas the present embodiment is different in that the embedding is performed by the pseudo gradation process. Further, in the present embodiment, an ink jet printer which is a binary recording system is used as the image recording system.

The image synthesizing / recording apparatus of this embodiment also has basically the same configuration as that of the first embodiment, and only the processing procedure is different. Hereinafter, the processing procedure will be described in detail with reference to the flowchart shown in FIG.

[First Step (Pattern Generation)] First,
In the first step S31, the pattern image Q (x, y) is created. As this pattern image Q (x, y), an irregular pattern similar to that of the second embodiment is created.

[Second Step (Pattern Modulation) Next, in the second step S32, the pattern image is modulated with the embedded image. This point is also the same as in the second embodiment,
Details are omitted.

[Third Step (Color Correction)] In the present embodiment, the embedded images Pr, Pg, and Pb represented by RGB in the third step S33 are next converted into C (cyan), M (magenta), and Y ( Color correction processing is performed to convert the ink density signals Pc, Pm, and Py that represent the control amounts of the three color inks (yellow). The conversion of this color correction processing is similar to that of the color correction processing of the first embodiment, and equations (19-1) and (19-2)
It is performed according to.

[0114]

(Equation 4)

[Fourth Step (Pattern Superposition)] In the next fourth step S34, the pattern modulation image is superposed by the error diffusion method based on the ink density signals Pc, Pm, Py obtained by the color correction processing. This pattern superposition processing is significantly different from the first and second embodiments, and will be described in detail. This processing is similar to the pseudo gradation method represented by the conventional error diffusion method. However, the pattern structure peculiar to the pseudo gradation is controlled so as to be close to the image pattern.

In the fourth step S34, the same processing is performed for the Y component Py, the M component Pm, and the C component Pc of the ink density signal, so only the Y component Py will be described here as a representative. The fourth step S34 includes the following four sub steps S34-1, S34-2, S34-3,
It consists of S34-4.

[Sub-step S34-1] First, the expression (2
0), the cumulative error signal E'Y (x, y) is added to the embedded image Py (x, y). The cumulative error signal E′Y (x, y) is for correcting the quantization error due to binarization, and its generation method will be described later.

P′Y (x, y) = PY (x, y) + E′Y (x, y) (20) [Sub-step S34-2] Next, the addition result PY ′ is calculated according to equation (21). Binarize. if PY ′ (x, y) + (2 · P (x, y) −1) · Vy ≧ 0.5 OY (x, y) = 1 if PY ′ (x, y) + (2 · P (x , Y) -1) · Vy <0.5 OY (x, y) = 0 (21) Here, Vy is a parameter that determines the superimposing color difference intensity, and Vm and Vc for the M component and the C component, respectively. To use. In the present embodiment, (Vm, Vc, Vc) = (+
The values of 0.2, -0.12, -0.12) are used. The pattern superimposing process by the error diffusion method in the fourth step S34 is different from the conventional error diffusion method in the substep S34-2.

[Sub-step S34-3] Next, the equation (2
Perform the error calculation in 2). EY (x, y) = PY ′ (x, y) −Oy (x, y) (22) EY (x, y) represents a quantization error due to binarization, and this error component is fed back to the input signal. Thereby, the quantization error is compensated.

[Sub-step S34-4] Next, the equation (2
The cumulative error is calculated according to 3).

[0121]

(Equation 5)

Here, a (xi, yi) is an error distribution coefficient, and the values in Table 1 are used.

[0123]

[Table 1]

By repeating the above processing while scanning the pixels, the processing is performed on all the images. Further, the same calculation is performed for the M component and the C component, so that the binarized images O'y, O'm, O'c by error diffusion are obtained.
Is obtained.

Although the error diffusion method is used here, a dither method or the like may be used instead of the error diffusion method.

The above is a series of processes for image synthesis, and finally, the binarized output images O'Y, O'M, O'C are processed in the image recording section.
Image recording is performed in accordance with. That is, Oy (x, y) =
In the case of 1, Y color ink is printed on the pixel (x, y),
When Oy (x, y) = 0, printing is not performed. As a result, the averaged densities in the macro area are O'y, O'm,
An image having almost the same density as O'c is reproduced.

At this time, black printing processing may be performed. In the black printing process, pixels that record all colors of YMC are set to K.
This is a process of replacing with (black) ink, and there are effects such as reduction of printing cost by reduction of ink amount, reduction of ink bleeding, and improvement of density by using black ink. Although various methods have been proposed as specific processing, for example, the following processing is performed to perform O ″ Y, O ″ of the black-printing processing image.
Recording may be performed according to M, O ″ C, O ″ K. In this case, the image recording unit needs to be able to record four colors of YMCK.

If (O′Y = 1 and O′M = 1 and O′C = 1) OY ″ = 0 OM ″ = 0 OC ″ = 0 OK ″ = 1 else OY ″ = OY OM ″ = OM OC ″ = OC OK ″ = 0 (24) Through the series of processes described above, the pattern modulation image is embedded as an error diffusion pattern. The recorded image (composite image) obtained by this processing has the following properties. That is, since the density is compensated by the error diffusion process, an image having substantially the same chromaticity as the embedded image is recorded as a composite image in macro. Further, similarly to the second embodiment, the modulation pattern image component is a color difference signal in which a high frequency component having low visual sensitivity is strong. Further, a small amount of low-frequency component is further reduced by the density compensation effect due to error diffusion. Therefore, the components of the pattern-modulated image modulated by the embedded image can hardly be visually observed.

Since the composite image is binarized after the intensity of the pattern modulation image is added in the error diffusion process, the binarized image has a very high correlation with the pattern modulation image. That is, the modulation parameters (Vy, V
m, Vc) has a positive correlation when the parameter is positive and a negative correlation when the parameter is negative. Further, the larger the absolute value of the parameter, the higher the correlation. Here Vy ≧
Since 0, Vm <0 and Vc <0, the Y component has a high positive correlation with the pattern modulation image, and the M and C components have a high negative correlation with the pattern modulation image.

On the other hand, the pattern modulation image is the pattern image inverted by the embedded image. Therefore, the positive / negative of this correlation is inverted in the pixel having the image value of 1 in the embedded image. That is, in the area where the pixel value of the embedded image is 0, the pattern modulation image has a positive correlation with the Y component of the composite image,
It has a negative correlation with the M and C components. Further, in the area where the pixel value of the embedded image is 1, the pattern modulation image has a negative correlation with the Y component of the composite image and has a positive correlation with the M and C components.

Next, a method of reproducing the embedded image from the composite image recorded according to the third embodiment will be described. Also in the present embodiment, as in the second embodiment, as shown in FIG. 10, a composite image is recorded on the transparent reproduction sheet 1003 having the transmittance distribution corresponding to the irregular pattern image Q (x, y). The embedded image is reproduced by superposing it on the recorded matter 1100. In this embodiment, the same sheet as that shown in the second embodiment is used as the reproduction sheet 1003. That is, the transmittance distribution Tr (x, y), Tg (x, y), Tb of the reproduction sheet 1003.
(X, y) is represented by the above equation (16). By embedding the reproducing sheet 1003 on the recorded material 1100, the embedded image is reproduced as a Y-B color difference signal.

The principle of reproducing the embedded image by superposing such a reproducing sheet 1003 on the recorded material 1100 will be described. As described above, in the region where the pixel value of the embedded image is 0, the pattern modulation image has a positive correlation with the Y component of the composite image and has a negative correlation with the M and C components. Further, in the region where the pixel value of the embedded image is 1, the pattern modulation image has a negative correlation with the Y component of the composite image,
It has a positive correlation with the M and C components.

Therefore, by overlapping the reproduction sheet 1003 described above on the recorded matter 1100, the pixels in which the Y ink is printed are likely to overlap the black pixels of the reproduction sheet 1003 in the area where the pixel value of the embedded image is 0. Further, the pixels on which the M ink and the C ink are printed are likely to overlap the white (transparent) pixels of the reproducing sheet 1003.
That is, in a macroscopic view, in a region where the pixel value of the embedded image is 0, the color shifts to B, which is a composite color of M and C. On the other hand, in the area where the pixel value of the embedded image is 1, the area is shifted to Y for the same reason. Therefore, the reproduction sheet 10
By overlapping 03, the chromaticity of the image shifts in the Y or B direction according to the pixel value of the embedded image, so that the embedded image is reproduced as information modulated in the Y-B color difference.

As described above, in the third embodiment as well, similar to the first and second embodiments, another image (embedded image) that is substantially the same as the image to be embedded and is not degraded in image quality (embedded image). It is possible to record a composite image in which is embedded. Further, by superimposing a predetermined reproducing sheet on the recorded matter on which the composite image is recorded, it is possible to reproduce the image easily and visually without the need for complicated signal processing. Moreover, since an irregular pattern is used for the pattern image in the embodiment, it is difficult to estimate the embedded pattern from the composite image as in the second embodiment.

Furthermore, in the present embodiment, as a feature which is not provided in the first and second embodiments, since the composite image is recorded by binary recording, it is easy to control the multi-value density for each pixel like the ink jet recording method. It has an advantage that it can be easily applied even when a non-printing type printer is used.

(Fourth Embodiment) Next, a fourth embodiment according to the present invention will be described. In the first to third embodiments, the embedded image is reproduced by stacking the reproducing sheet having the transmittance distribution on the recorded material, whereas
The present embodiment is different in that reproduction can be performed by an optical element having a thickness distribution.

First, the image synthesizing / recording apparatus according to this embodiment will be described. The configuration and processing procedure of the image synthesizing recording device in this embodiment are basically the same as those in the first embodiment, and only the configuration of the pattern image is slightly different. The processing procedure in this embodiment will be described below with reference to the flowchart shown in FIG.

[First Step (Pattern Generation)] First,
In the first step S41, a pattern image Q (x, y) is generated. In the present embodiment, this pattern image Q (x, y)
A stripe-shaped pattern image as shown in FIG. This pattern image Q (x, y) has pixels with a gain of −1 and 1 for the color difference amount (Vr, Vg, Vb).
19 are arranged in a striped pattern, and in the example of FIG. 19, the gain-1 pixels are arranged in two rows in the y-axis direction and the gain-1 pixels are arranged in two rows in the y-axis direction alternately. In other words, that is, they are arranged in a cycle of 4 pixels in the x-axis direction. A formula for generating this pattern image Q (x, y) is shown in formula (25).

If (int (x / 2) mod2 = 0, Q (x, y) =-1 If (int (x / 2) mod2 = 1, Q (x, y) = 1 (25 ) [Second step (pattern modulation)] [Third step (pattern superimposition)] [Fourth step (color correction) Next, second step S42,
In the third step S43 and the fourth step S44, pattern modulation, pattern superposition, and color correction are sequentially performed, and the finally obtained composite image is recorded, but these processes are exactly the same as in the first embodiment. Therefore, the description is omitted.

Also in this embodiment, as in the first embodiment, a composite image in which the embedding image and the embedding image are combined is recorded. This composite image is an image that looks almost the same as the embedded image, and the information of the embedded image is completely
Or the information is almost invisible.

Next, a method of reproducing the embedded image from the composite image recorded in this embodiment will be described. In this embodiment, an optical system in which a cylindrical lens array, that is, a so-called lenticular lens is configured in a sheet shape is used for reproducing the embedded image.

FIG. 20 shows a lenticular lens 2000.
This is a structure in which a plurality of cylindrical lenses are arranged in parallel. The focal point of each cylindrical lens is the bottom surface 20.
On 01. The pitch of the cylindrical lenses is equal to the cycle of the pattern image Q (x, y) in the x-axis direction (4 pixels in this embodiment).

FIG. 21 shows a lenticular lens 200.
A schematic diagram in the case where 0 is overlaid on the composite image on the recorded matter 2002 is shown. The cylindrical axis of the cylindrical lens (Fig. 2
1 (perpendicular to the paper surface) and the x-axis direction of the composite image, that is, the cycle direction of the pattern image Q (x, y) are orthogonal to each other, and Q (x, y) = 1 of the corresponding pattern image
Position so that the center of the part is on the central axis of each cylindrical lens. And the lenticular lens 200
By observing from the top of 0, the embedded image is reproduced.

The principle of reproducing an embedded image in this embodiment will be described with reference to FIG. The pattern image Q (x,
Since y) = 1 is aligned with the central axis of the cylindrical lens, when observing the image from the direction perpendicular to the cylindrical lens surface, all the light is in the central part of Q (x, y) = 1 of the pattern image. get together. Therefore, Q (x, y) of the pattern image =
The image of the portion 1 is visible, and the image of the portion Q (x, y) =-1 does not contribute to the observed image at all. Therefore, in the region where the pixel value R (x, y) of the embedded image is 0, (Vr, V
An image obtained by adding g, Vb) can be seen, and an image obtained by subtracting (Vr, Vg, Vb) can be seen in the region of R (x, y) = 1. Therefore, an image in which the color difference is shifted according to the embedded image is observed.

Here, in the first embodiment, the R (x, y) = 1 portion of the embedded image did not appear to overlap with the black portion of the reproducing sheet, but in the present embodiment, R (x, y) = 1.
Since the y) = 1 part also appears as a color difference-shifted color,
A color difference contrast twice as high as that of the first embodiment can be obtained. Further, since the embedded image component is not blocked by the black pixels of the sheet, the embedded image component is observed with its original brightness.

Further, in the first embodiment, the embedded image cannot be reproduced unless the reproduction sheet and the position of the composite image are in a predetermined relationship, whereas in the present embodiment, the reproduction optical element is used. A certain lenticular lens 2000
Is deviated from the predetermined positional relationship with the composite image,
The embedded image can be reproduced by moving the viewpoint. That is, for example, consider a case where the Q (x, y) = 1 portion of the pattern image is slightly shifted to the right from the central axis 2201 as shown in FIG. In such a case, by moving the viewpoint so as to observe from the direction of arrow 2202, the focus position shifts to the position of Q (x, y) = 1, and the embedded image can be reproduced correctly.

Also in the present embodiment, the embedding image can be recorded because it is substantially the same as the embedding image visually as in the first embodiment. Further, by stacking a predetermined sheet-shaped reproducing optical element such as a lenticular lens, this embedded image can be easily reproduced as a superimposed image on the embedded image and visually confirmed.

Further, in this embodiment, since the lenticular lens is used as the reproducing optical element, (1) the reproduction contrast becomes about twice as high as that of the first embodiment. (2)
Even if the reproduction optical element and the composite image are out of phase, the position where the reproduction contrast is maximum can be obtained by shifting the viewpoint, and (3) the embedded image can be observed with the same brightness. Has excellent advantages.

[0149]

As described above, according to the present invention, a composite image in which another first image is embedded can be recorded on the second image without degrading the second image, and at the time of reproduction. ,
The embedded image can be easily reproduced by a simple operation of stacking a sheet-shaped reproducing element having a pattern corresponding to the composite image on the recorded material without requiring complicated signal processing.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an image composition recording / reproducing system according to a first embodiment.

FIG. 2 is a flowchart showing an image processing procedure according to the first embodiment.

FIG. 3 is a diagram showing a configuration of a checkered pattern image used in the first embodiment.

FIG. 4 is a diagram showing a kernel of a smoothing filter for smoothing an embedded image according to the first embodiment.

FIG. 5 is a diagram showing an example of a relationship among an embedding image, a smoothing embedding image, a pattern image, and a pattern modulation image according to the first embodiment.

FIG. 6 is a diagram showing another example of the relationship among the embedded image, the smoothed embedded image, the pattern image, and the pattern modulation image in the first embodiment.

FIG. 7 is a block diagram showing an example in which an image processing system of the image composition / recording apparatus according to the first embodiment is realized by hardware.

FIG. 8 is a diagram showing frequency spectra of color difference components of an embedded image, a smoothed embedded image, a pattern image, and a composite image according to the first embodiment.

FIG. 9 is a diagram showing visual chromaticity spatial frequency characteristics.

FIG. 10 is a perspective view showing the configuration of the reproducing apparatus according to the first embodiment.

FIG. 11 is a diagram showing a pattern configuration of a reproduction sheet in FIG.

FIG. 12 is a diagram showing a frequency spectrum of an image in which a reproducing sheet is overlaid on a recorded material in the first embodiment.

FIG. 13 is a flowchart showing an image processing procedure according to the second embodiment.

FIG. 14 is a diagram showing an autocorrelation coefficient and a power spectrum of an irregular pattern image used in the second embodiment.

FIG. 15 is a diagram showing frequency spectra of color difference components of an embedded image, a smoothed embedded image, a pattern image, and a composite image according to the second embodiment.

FIG. 16 is a diagram showing a frequency spectrum of an image in which a reproducing sheet is overlaid on a recorded material in the second embodiment.

FIG. 17 is a flowchart showing an image processing procedure according to the third embodiment.

FIG. 18 is a flowchart showing an image processing procedure according to the fourth embodiment.

FIG. 19 is a diagram showing a pattern configuration of a pattern image used in the fourth embodiment.

FIG. 20 is a diagram showing a configuration of a lenticular lens which is a sheet-shaped reproducing optical element according to the fourth embodiment.

FIG. 21 is a diagram showing a principle of reproducing an embedded image according to the fourth embodiment.

FIG. 22 is a diagram showing a reproduction state when the reproduction optical element and the pattern image in the composite image on the recorded material are out of phase in the fourth embodiment.

[Explanation of symbols]

 101 ... CPU 102 ... Image memory 103 ... Image input section 104 ... Program memory 105 ... Image recording section 106 ... Bus 107 ... Image processing section 701 ... Image memory 702 ... Image memory 703 ... Pattern generating section 704 ... Pattern modulating section 705 ... Pattern Superimposing section 706 ... Color correcting section 707 ... Image recording section 1000 ... Image reproducing apparatus main body 1003 ... Reproducing sheet 1100 ... Recorded matter 2000 ... Lenticular lens (reproducing optical element) 2002 ... Recorded matter

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location H04N 1/44 H04N 1/40 Z 1/46 1/46 Z C3,4 (72) Inventor Kazuhiko Higuchi Kanagawa Prefecture Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Toshiba Research & Development Center

Claims (6)

[Claims] 1. A pattern image generating means for generating a predetermined pattern image signal; a modulating means for modulating the pattern image signal with a first image signal to generate a pattern modulated image signal; and the pattern modulated image. An image recording apparatus comprising: a superimposing unit that superimposes a signal on a second image signal; and a recording unit that inputs an image signal output from the superimposing unit and records an image. 2. A pattern image generating means for generating a predetermined pattern image signal, a smoothing means for smoothing the first image signal, and a first smoothing means for smoothing the pattern image signal by the smoothing means. Modulating means for generating a pattern-modulated image signal by modulating the image signal, superimposing means for superimposing the pattern-modulated image signal on the second image signal, and inputting the image signal output from the superimposing means. An image recording apparatus comprising: a recording unit that records an image. 3. A pattern image generating means for generating a pattern image signal in which gain values given to a predetermined color difference amount for each pixel are arranged in a predetermined pattern, and the pattern image signal is modulated by the first image signal. And a superimposing means for superimposing the pattern-modulated image signal on the second image signal composed of the color image signal after multiplying the pattern-modulated image signal by the predetermined color difference amount. An image recording apparatus comprising: a recording unit that inputs an output image signal and records an image. 4. A pattern image generating means for generating a pattern image signal in which gain values given to a predetermined color difference amount for each pixel are arranged in a predetermined irregular pattern, and a first image signal for the pattern image signal. Modulating means for generating a pattern-modulated image signal by converting the pattern-modulated image signal into an ink density signal, and a second means for converting the pattern-modulated image signal by an error diffusion method according to the ink density signal. An image recording apparatus comprising: a superimposing unit that superimposes on an image signal, and a recording unit that inputs an image signal output from the superimposing unit and records an image. 5. A recorded matter in which an image signal obtained by superimposing a pattern-modulated image signal obtained by modulating a predetermined pattern image signal with a first image signal on a second image signal is recorded as an image. An image reproducing apparatus for reproducing the image No. 1 as a visible image, comprising a sheet having a transmittance distribution of the same pattern as the pattern of the pattern image signal and arranged on the recorded matter. Image playback device. 6. A recorded matter in which an image signal in which a pattern-modulated image signal obtained by modulating a predetermined pattern image signal with a first image signal is superimposed on a second image signal is recorded as an image, An image reproducing apparatus for reproducing the image No. 1 as a visible image, comprising an optical element having the same thickness distribution as the pattern of the pattern image signal and arranged on the recorded matter. Image playback device.