JPH0276126A - Method for detecting recording status of optical recording medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for detecting the recording state of an optical recording medium.

BACKGROUND OF THE INVENTION Optical memories currently in practical use can only record one bit of information per minimum area irradiated with a laser beam. In contrast, a method has been proposed in which multiple bits of information are recorded at the same location by providing a recording layer made of multiple types of dyes having different light absorption wavelength regions.

Problems to be Solved by the Invention However, when the absorption and fluorescence of multiple organic dyes in the recording layer overlap, it is difficult to accurately detect the recording state of each dye using steady-state fluorescence and absorption. No reports have been found regarding a recording state detection method that is effective in such cases.

The present invention aims to solve the problems of the prior art.

Means for Solving the Problems The present invention uses fluorescence to detect the recorded state of the dyes in the recording layer in an optical recording medium consisting of a recording layer containing a plurality of dyes with different fluorescence lifetimes, and in this case, excitation light irradiation is performed. This is to detect fluorescence at a specific time afterward.

In active dye molecules, even if there is no difference in absorption and fluorescence wavelengths, there may be a large difference in fluorescence lifetime.

Therefore, using the L distribution method, if we look at the fluorescence early after excitation light irradiation, we will detect fluorescence from dyes with short fluorescence lifetimes, and if we look at the fluorescence at late times, we will selectively detect fluorescence from dyes with long fluorescence lifetimes. can be detected. In this way, by shifting the timer, the fluorescence from each dye can be detected with less overlap.

Therefore, highly reliable reproduction is possible.

Example The present invention will be explained in detail below.

Cyanine dyes and rhodamine chromophores are representative dyes, but their absorption maximums are concentrated at 500 nm to 600 nm, and therefore their fluorescence maximums are concentrated at 600 nm to 700 nm. As described above, cyanine dyes and rhodamine dyes, which have overlapping absorption and fluorescence, have different fluorescence lifetimes and are therefore effective in the present invention.

FIG. 1 is a block diagram of an optical recording medium according to an embodiment of the present invention. 1 is a substrate. 2 and 3 are recording layers, the first recording layer 2 is an aqueous solution of rhodamine B, and the second recording layer 3 is an aqueous solution of 1,1-diethyl-2,2-cyanine bromide, which is gelatinized with gelatin. They are laminated in order on a substrate l using a spin cord. 4 is a protective film. Here, the fluorescence lifetime of rhodamine B is relatively long <ins or more, and the fluorescence lifetime of 1.1-diethyl-2,2-cyanine bromide is 100 ps or less.

Figure 2 shows the fluorescence corresponding to recording layers 2 and 3, where A2 is the fluorescence obtained within 0.1 ns after irradiation with excitation light, and A3 is the fluorescence obtained after 0.5 ns after irradiation with excitation light. This is the resulting fluorescence.

FIG. 3 shows fluorescence in a steady state, and it is impossible to distinguish between A2 and A3 in FIG. 2 because they overlap. This can be clearly separated by measuring the fluorescence at specific times as shown in FIG. This is due to the difference in the fluorescence lifetimes of the two dyes, but Figure 4 shows the relationship between changes in fluorescence intensity over time for the dye rhodamine B, which has a long fluorescence lifetime, and the dye 1, to-diethyl-2,2-cyanine bromide, which has a short fluorescence lifetime. This is a schematic representation. The vertical axis represents fluorescence intensity, and the horizontal axis represents elapsed time after light irradiation. Looking at this, it can be seen that although both of the two dyes begin to emit fluorescence immediately after irradiation with light, 1.1-diethyl-2,2-cyanine bromide has a short fluorescence lifetime, so almost no fluorescence occurs within 0.1 ns. However, it can be seen that -rhodamine B has a long fluorescence lifetime and therefore takes time to emit fluorescence. Therefore, the main component of fluorescence up to 0.1 ns is fluorescence from 1.1.-diethyl-2,2.-cyanine bromide, and the fluorescence after 0.5 ns is fluorescence from rhodamine B.

FIG. 5 is a system configuration diagram for implementing the detection method of the present invention. 5 is the optical recording medium shown in FIG. 1, and 6 and 7 are light sources. 6 is 520nm, 7 is 570n
It is possible to irradiate m light with a pulse width of 10 ps or less, and each can be turned on and off individually by human input signals. A condenser 8 condenses light from a light source onto the optical recording medium 5. 9 uses a spectroscope to extract light of 580nm-600nm to 10,1
Guides light to sensor 1. Each light received in this way is independently converted into an electrical signal. I will talk about recording and playback below.

a) Recording Now, if you want to set only the first recording layer 2 to "1", turn on the light source 6.
Turn only 7 on and turn 7 off.

At this time, the recording material N2 selectively absorbs light, decomposes due to heat generation, and ceases to emit fluorescence. In this way, 1j11t is recorded only on the first recording layer 2.

b) Reproduction The irradiation energy during reproduction is 1/1 of the energy during recording.
Light is emitted from the light sources 6 and 7 at the same time so that the amount of light becomes 0 or less. The pulse width of the excitation light irradiated at this time is about 10 ps. Depending on whether or not the dye is decomposed in the recording layer, the fluorescence intensity from each recording layer changes, and this can be extracted as a 2-bit electrical signal through a sensor.

At this time, the sensor 10 detects fluorescence up to 0.1 ns from irradiation with the bright light, and the sensor 11 detects fluorescence after 0.5 ns using the excitation light as a trigger.

Note that in this example, the excitation light is applied in pulses during reproduction, but the pulses may be applied in multiple pulses, each time detected by the sensor. All you have to do is integrate it. In this case, the time-close interval of the excitation light pulses does not need to be constant, and the intensity of each pulse may be different or constant. moreover,
Each light source does not have to emit light at the same time. Further, although the pulse width of the excitation light pulse during reproduction is about 1 Ops in this embodiment, it can be changed depending on the fluorescence lifetime of the dye to be detected. Instead of excitation by pulse irradiation as in this embodiment, continuous irradiation may be used to change the intensity. A fluorescence collector may be placed in front of the sensor.

In this example, the recording layer is made by the spin code method, but it may be made by the LB (Langmuir-Blodgett) method, and the recording state detection method of the present invention does not particularly depend on the recording layer forming method. Applicable. The recording medium may have a separation layer between each recording layer. It is also applicable to a case where a rewritable recording medium is formed using a photochromic compound as a dye. Although this embodiment describes the case where two types of dyes are present in the recording medium, there is no essential difference even if there are three or more types of dyes.

Effects of the Invention According to the present invention, fluorescence from each dye in the recording layer can be detected with little overlap, and the recording state can be detected with good accuracy. Therefore, it has the advantage that reproduction from a high-density recording medium in which two or more bits are recorded at one location is facilitated.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of an optical recording medium used in an embodiment of the method for detecting the recording state of an optical recording medium of the present invention, and FIG. Fig. 3 is a graph showing steady-state fluorescence of the same example, Fig. 4 is a graph schematically showing temporal changes in fluorescence intensity from each dye, Fifth
The figure is a block diagram showing an example of the information recording and reproducing system of the same embodiment. l...Substrate, 2, 3... Recording layer, 4... Protective film,
5... Optical recording medium, 6, 7... Light source, 8... Concentrator, 9... Spectrometer, 10.11... Name of sensor agent Patent attorney Shigetaka Awano Haka 1 person Figure 1 Figure 2 Figure 5 Skin length (nm) Figure 3 j Skin length (nm) Figure 4 Time after light irradiation (nS) Figure 5 No. 228232 2 Name of the invention Method for detecting the recording state of an optical recording medium 3 Relationship with the person making the amendment Case Patent application
Address 1006 Oaza Kadoma, Kadoma City, Osaka Name (582) Matsushita Electric Industrial Co., Ltd. Representative Tani
Akio Ii 4 Agent 571 Address Matsushita Electric Industrial Co., Ltd., 1006 Kadoma, Kadoma City, Osaka Prefecture.

Claims (1)

[Claims] 1. A method for detecting a recording state of an optical recording medium, comprising reproducing an optical recording medium comprising a recording layer containing a plurality of dyes with different fluorescence lifetimes using fluorescence at a specific time after irradiation with excitation light.