JP2927438B2 - Method and apparatus for recording images by laser and medium therefor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for recording an image using a laser.

In the present invention, the word “image” means not only a graphic display but also a printed text, a photograph, and the like.

2. Description of the Related Art For some applications, it is necessary to form an image on a medium that is difficult to alter or counterfeit.

Various methods are known for achieving this goal. Among them, a method of printing banknotes by a chemical transfer method may be mentioned. Various special methods have been used to make it difficult to imitate this method, but in some applications, imitating this method cannot be made sufficiently difficult.

Other methods, such as those used to produce digital optical disks, employ a method of removing selected layers that absorb incident light. When the light absorbing layer is removed by light irradiation, a specific portion of the medium is exposed to form an image. However, the "efficiency" of this method is low, and the quality, (definition, contrast, etc.) of the image cannot be equal to the quality of the printed image.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method that can not only be difficult to falsify or counterfeit, but also can generate an image having a quality substantially equal to the quality of a printed image. To provide. Such a method has particular application in the creation of top secret documents, such as, for example, identification cards.

According to the present invention, in order to achieve the above object, there is provided: a first material which is arranged in a plurality of rows on a substrate and forms an image area and a readout area. A first layer in which the image area is covered by a second layer capable of absorbing laser light;-a high-speed first movement along a first axis with respect to said recording medium; * A laser beam that is slower than the first movement and is capable of a double relative movement, for example with a second movement along a second axis perpendicular to the first axis; Means for modulating the power of the laser beam according to what information is recorded in synchronization with the movement.

The laser beam is guided over the row by the readout area, the image area on which the image is to be formed in the form of a strip parallel to the first axis, and the light-absorbing material thereon depends on the power of the laser beam. Therefore, the first material is selectively destroyed according to the information to be recorded, and the first material is selectively exposed. The read area is removed after the end of the recording operation.

Other objects, features and results of the present invention will be better understood from the following description with reference to the accompanying drawings.

Embodiment FIG. 1a is a diagram showing a first embodiment of the image medium of the present invention.

This figure shows a substrate 1 made of, for example, paper, cardboard or plastic, on which two regions are defined. That is, O of OXY in the rectangular coordinate system
Image areas separated by the equilibrium axis ZZ the X axis is a Z _I and read area Z _L. Image area Z in _I the first material 2 is deposited as a strip 20 parallel to the OY axis, column C _1, C _2,
C ₃ ... C _i ... are formed. This material 2 is, for example, an ink deposited by photoetching, smooth cutting, offset or otherwise.

The image area Z _I, for example, a layer 3 of a second material that absorbs a predetermined irradiation light such as laser light is deposited.
This material 3 preferably has a low melting point. However, in some applications, the melting point may not be too low, and may be preferably higher than normal for plasticizing the media, for example to about 200 ° C. This layer 3 is, for example, an organic layer or a metal layer. This layer 2 is thin and the light absorption is determined by the composition and thickness for a given irradiation light. As the layer 3, for example, a tellurium compound having a thickness of about 200 ° is suitable.

The part corresponding to the read area Z _L of the medium, the strip made of a first material 2 is deposited again along the columns _{C 1, C 2 ... C i} .... These strips may be continuous or discontinuous. For example, in FIG. 1a, the strip comprises a plurality of rows C _i
Are shown as two patterns 41 and 42 arranged in a row. Material forming the column or pattern of the read region Z _L is noted that may be different from the material 2.
Strip 20 and patterns 41, 42 to make the drawing easier to read
The part is drawn with "Nashiji".

FIG. 1b is a diagram showing a modification of FIG. 1a. This 1b
Example figure strip 20 of the image area Z _I is also that it has been arranged in a plurality of columns C _i is discontinuous form as a plurality of small parts 21 are different. For example, the minute portion is a square having a side of 20 μm.

In FIG. 1b, the light absorbing material layer 3 is not shown for the sake of simplicity.

FIG. 2 is a diagram showing a means for optically recording an image on the medium.

The drawings, as an example, the entire recording medium is indicated by reference numeral 10 shown in FIG. 1 and a read area Z _L and the light absorbing material 3 coated with the image area Z _I.

This recording medium includes a laser L that emits a light beam F toward a modulator M. The modulator M is controlled by the signal P. By performing this control, the recording medium 10
The power of the laser L can be modulated according to what information is recorded in the laser L. The energy of the light is
_Is sent to the oscillating mirror Mv through the separating means S. The mirror M _v can vibrate about a parallel ZZ axis OX axis. The mirror M _v sends toward the laser beam F on the recording medium 10 to form a spot S _L thereon.

If necessary, the recording medium 10 transmits the beam F to this recording medium.
Means (not shown) for focusing on the surface 10 are provided.

Depending on the power of the beam controlled by the signal P,
The recording medium performs one of the following two operations.

A first operating mode corresponding to the case where the light power is small, for example between 1 mW and 3 mW;
A second operation mode corresponding to the case where the material 2 can be removed to remove the material 2.

The areas where the material 2 is exposed form the desired image as a whole.

By controlling the movement about the ZZ axis of the mirror M _v, 1 row of the laser beam spot S _L image area Z _I
It becomes possible to draw C _i . Furthermore, the recording medium 10 translates along the OX axis with respect to the above optical device, so that the laser beam can move from one row to the next. In order to be able to write in rows parallel to each other, this movement is continuous along the OY axis, even in discontinuous movements where the movement only takes place during the time available during the spot scanning movement along the OY axis. The movement may be slower than the scanning movement.

As a result, it is possible to record an image on the image area Z _I using the control signal P of the modulator M. The quality of the image depends on the parameters chosen for particular controlling the scanning speed of the power and the spot S _L of the beam F.

In another embodiment, forgery is more difficult because the substrate 1 is of a different color than the strips 20 or the micro-parts 21. In other words, there is a high possibility that not the material 2 but the medium will be exposed when trying to forge.

Various methods of controlling the laser beam are possible and are shown in FIGS. 3a-3c.

The light pulse can have a constant frequency and a constant width, in which case the recording is of a binary type.

According to another embodiment, the light pulse is variable in width,
Patterns of various sizes can appear. This is shown in FIG. 3a.

In this 3a, the power P of the laser beam F is shown as a function of time. The power P is the minimum level for different pulse widths _{(L 1, L 2 ...)} P m and the maximum level P _M
Take two levels.

FIG. 3b is a partial cross-sectional view along the column of the recording medium 10 when the column is irradiated with the modulated laser beam of FIG. 3a.

In this section, the substrate 1 is partially covered by a strip 20. It is when the laser power is the minimum level P _m remains the strip 20, on the contrary, the strip 20 is removed by the laser beam at a portion having a width corresponding to the pulse width L ₁ and L ₂ because Because.

If formed by a plurality of micro-parts in a row, the pulses need to be synchronized with these micro-parts as described with reference to FIG. 1b.

In another embodiment, the power of the laser beam is no longer 2
One is the level P _m and the level P _M 2 value format taking no changes between these two levels continuously. In this way, the light absorbing layer 3 can be broken to some extent, for example, to expose a substantially triangular pattern. This is shown by way of example in FIG. 3c. In this figure, two strips 20 are shown, with differently shaped triangular patterns 31, 32 appearing. To make the drawing easier to see,
A plurality of points are drawn only in the area where the material 2 is exposed.

Referring to Figure 2 again, the laser beam F is directed to the vibrating mirror M _v and partially reflected by the recording medium 10, then is deflected by the separation means S are directed to the photosensitive cell C. A light spot T is formed in the cell C. Cell C outputs an electrical detection signal D.

The detection signal, as shown in FIG. 4 below, is used to scan the recording medium 10 by the spot S _L containing information constituting the image to synchronize. This signal becomes the signal P.

For this purpose, the spot S _L scans including the region Z _L reading the whole of each column C _i. It can be recognized (detected) the start of a row by the read region Z _L of the pattern (41 of FIG. 1). This is because the properties of the patterns 41 and 42 (the reflection of the beam is better or worse than that of the medium 1) and, in some cases, the thickness (the spot T on the cell C is shifted from the center if the thickness is too large). Changes the amplitude of the detection signal, which characterizes the start of the sequence. It should be noted that this detection cannot be performed on the rows of the image area, because the strip 20 or the microscopic part 21 is covered by the light absorbing layer 3 in the image area.

In another embodiment, the patterns 41, 42 are different in one row and the next. Therefore, each column can be identified better.

FIG. 4 is a diagram showing an embodiment of electronic means for controlling the recording medium of the present invention.

After being amplified by the amplifier 40, the electrical detection signal D is sent to a circuit 43 for confirming (detecting) the start of the column.

Under the control of the timing adjustment circuit 45 having a clock and a counter, the circuit 43 outputs a signal corresponding to the start time T ₀ of the columns of the image area Z _I. This signal can be, for example, a change to a state 0 of a binary signal and is sent to a logic circuit 46 of the AND gate type. From the AND gate 46, a control signal P for the modulator is output. In this embodiment, the time
The signal indicating T ₀ is sent to a circuit 44 that determines the end time T ₁ of the column before being sent to the AND gate 46. The determination of the end time T ₁ of the row is made by adding to the time T ₀ a certain time interval corresponding to the time required for the beam F to scan the row. In this embodiment, a signal indicating the time T ₁ is the same logic signal changing to state 1. The circuit 44 is controlled by the timing adjustment circuit 45.

In the embodiment shown in FIG.
And a comparator 47 for comparing the detection signal from the comparator with the threshold value. With this comparator 47, if the laser spot S _L is sometimes out of the strip 20 is capable of detecting it. This is because in this case, the signal D changes (eg, decreases) due to the difference in the reflected power between the material 2 and the substrate 1. The output signal of the comparator 47 is sent to the AND gate 46. The AND gate 46 further information I to be recorded on the recording medium 10, receives in synchronization example at time T ₀ and T ₁ via the buffer memory.

Therefore, this AND gate detects that the spot _SL is at time (T ₀ and T ₀
Allow the passage of information I when in the inside of) the image area Z _I between _1. If necessary, the operation of comparator 47 allows the AND gate to pass information I only when the spot _SL is exactly aligned with one row. Finally, timing adjustment circuit 45 controls the movement of the mirror M _v.

Thus, a laser beam that is electrically controlled by a binary or non-binary signal representing an image is used to describe a recording medium on which an image is recorded with an excellent effect and which image is difficult to forge or falsify. did.

Note that the read area of this recording medium does not necessarily need to be formed on the same medium as the image area. In any case, to prevent the column C _i is recognized, the read area after the recording of the image is separated from the image area.

In addition, the minute portions 21 are arranged in color in the image area in advance (for example, four colors of blue, yellow, red, and black in a square shape),
It should also be noted that if the laser beam is controlled accordingly, the image can be recorded in color.

The above description is, of course, only for one example, and other columns can be considered within the scope of the invention. For example, it is possible to deposit an additional layer on the light absorbing layer 3. This additional layer is transparent, has a thickness of approximately half the wavelength of the laser light and has the function of matching the layer with air. Therefore, reflection at the surface of layer 3 is limited.
Although the movement of the recording medium 10 with respect to the optical means has been described (FIG. 2), it is needless to say that this is a relative movement, and the recording medium 10 can be fixed and the optical means can be moved if necessary.

[Brief description of the drawings]

1a and 1b show an embodiment of an image medium. FIG. 2 is a diagram showing an embodiment of an optical unit for recording an image. 3a, 3b, and 3c are diagrams for explaining the operation of the recording medium of the present invention. FIG. 4 shows an embodiment of the electronic means for controlling the optical means of FIG. 2 to carry out the method of the present invention. (Main reference numbers) 1... Substrate, 2... First material, 3... Light absorbing layer, 10... Recording medium, 20... Strip, 21. 32,41,42 ...... pattern 43 starts recognition (detection) circuit ...... column, 44 determination circuit of ...... T _1, 45 ...... timing adjustment circuit, 46 ...... the AND gates, 47 ...... comparator, C ...... photoresponsive _{cells, C 1, C 2 ... C} i ... ...... column, D ...... electrical detection signal, F ...... light beam, L ...... laser, M ...... modulator, M _v: Vibrating mirror, P: Control signal, S: Separation means, S _L , T: Spot, Z _I: Image area, Z _L: Read area

Claims (6)

(57) [Claims] 1. A method for recording an image on a recording medium using a laser beam, the recording medium comprising: a substrate; and a plurality of rows arranged on the substrate to read out an image area. A layer of a first material forming the region; and a second layer of a light-absorbing material deposited on the image area of the layer of the first material and destroyable by a laser beam. A laser beam, relative to the recording medium, for: a fast first movement along a first axis; and a second movement along a second axis, slower than the first movement. The laser beam is guided over the row by the readout area, and the power of the laser beam is modulated in synchronism with the first motion according to the image. To selectively destroy the second material, As a result, the first material is selectively exposed, the area of the image area where the first material is exposed forms the image, and the reading area is removed after completion of the recording operation. A method comprising: 2. Apparatus for recording an image on a recording medium according to the method of claim 1, comprising: means for generating a laser beam; and means for synchronizing the laser beam with an electrical signal representing the image to be recorded. Means for modulating power; means for scanning the recording medium with a laser beam along a first axis; means for guiding the laser beam on a row of the recording medium; and recording the position of the guiding means. Means for synchronizing with a power image. 3. A recording medium for recording an image according to the method of claim 1 using a laser beam, comprising: a substrate; and an image area and a read area arranged in a row on the substrate. A layer of a first material to be formed; and a second layer of a light-absorbing material deposited on the image area of the layer of the first material, the second material comprising: Removing the layer to expose the first material in a shape that forms the image, wherein the readout area is removed from the image area after the end of the recording operation. Medium. 4. The method according to claim 3, wherein said first material is deposited on said substrate along a plurality of successive rows.
A recording medium according to claim 1. 5. The recording medium according to claim 3, wherein said first material is deposited on said substrate as minute portions arranged along said rows. 6. The recording medium according to claim 5, wherein said minute portion has a different color, so that an image can be recorded in color.