JPH04222927A - Optical read-out system - Google Patents

Abstract

PURPOSE:To be not erased the storage data even by performing the repetitive read-out with the optical read-out for photochromic data storage device use and to be unnecessary to weaken the intensity of the read-out light extremely. CONSTITUTION:The reading light is made by simultaneously radiating the writing light and the erasing light. The intensity ratio of the writing light and the erasing light is determined by considering the absorption probability of the photochromic material in each state. In an adequate relative intensity, there is no variation in the whole. The wider range of the reading light intensity can be adopted, so a low sensitive detector can be used.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to photochromic data.
The present invention relates to an optical reading system for a data storage device, and more particularly, to a method for solving the problem of stored data volatilizing when repeated optical reading is performed. This is useful in the electronics industry, particularly in the fields of optoelectronics, optical communications and optical data storage.

0002

[Prior Art] Conventionally, as a method for reading data stored in a photochromic memory, a method has been used in which a storage element is irradiated with light and a change in absorbance or a change in refractive index is detected. I've been exposed to it.

0003

[Problems to be Solved by the Invention] However, the readout light used to analyze changes in absorbance or refractive index usually has the wavelength of either the writing light or the erasing light, or a single wavelength other than that of the writing light or the erasing light. Since so much light is used, some of it is absorbed by the storage element, resulting in a slight erasure of the stored data. After repeated reading, the data
The data will eventually be erased. The greater the intensity of light required, the faster the data will be erased by repeated reading. Therefore, it is desirable that the reading light be weak. However, there is a problem in that a highly sensitive detector is required to detect data with weak readout light. It is an object of the present invention to solve these problems and provide an optical readout method that does not erase stored data even after repeated reading and does not require a highly sensitive detector. .

0004

[Means for Solving the Problems] The present invention provides an optical reading method for photochromic data storage in which information is written by irradiating writing light and erasing information by irradiating erasing light. The readout light that is emitted is
This is an optical readout method characterized by using a mixture of the wavelength of writing light and the wavelength of erasing light at a predetermined intensity ratio.

[0005]

In a photochromic data storage system, data is stored with one wavelength of light and erased with another wavelength of light. If the storage element is read by simultaneous irradiation with light of appropriate intensities of erasing and writing wavelengths, no net change is induced in the storage element. Therefore, there is no instability due to read operations. Furthermore, the intensity of the light applied to read the storage element need not be very low to prevent damage to the system. As a result, the state of the storage element can be detected by
easier than before.

[0006]

[Example] Next, an example of the present invention will be described. The write and erase wavelengths correspond to the optical absorption of the two photochromic states used. If one of these two states is used as readout light, that light will be absorbed and cause a change to the other state. However, if both write and erase light are applied to read the contents of a storage element, at appropriate relative intensities there is no overall change. The intensities of the two illuminating lights must be adjusted to the relative absorption probabilities of the two states at the wavelength of the incident light. For example, in an optically thin state, the proportion fA of molecules converted from state A to state B is given by the following equation 1
is given in the classical two-state model.

[0007]

[Math 1] In approximation to a small value of fA, this number 1 is

[
Equation 2] fA=2.303φAεAIA103. Here, εA is the absorption coefficient of light with wavelength λA in state A,
φA is the quantum yield of the formation of state B, and IA is the intensity of the incident light at wavelength λA. The absolute number of molecules changing from state A to B is equal to the initial number of molecules in state A, nA, multiplied by fA. Assuming that there is no overall change due to the readout operation, the number of molecules nAfA must be equal to the number nBfB of molecules B that undergo inverse conversion by light with wavelength λB. In other words, the ratio of the write light intensity to the read light intensity must be a first approximation given by Equation 3 below.

[Equation 3] Here, εB is the absorption coefficient for light with wavelength λB in state B, φB is the quantum yield of formation of state A, IB is the intensity of the incident light with wavelength λB, and nB is the light with wavelength λB is the number of molecules in state B before irradiation.

From equation 2, it can be seen that what is important is the relative intensity of the light used for the read operation, not the absolute intensity of that light. Of course, the light intensity must be kept at a reasonable value so that the light does not cause other undesirable photochemical reactions such as multiphoton events. In either case, this readout scheme allows for a much wider range of readout light intensities and thus allows the use of less sensitive detectors.

[0009]

[Effects of the Invention] The optical readout method of the present invention explained above is as follows:
It is very useful for optical data storage using photochromic materials and overcomes many of the problems of conventional optical data storage methods.

Claims (1)

[Claims] Claim 1: In an optical readout method for photochromic data storage in which information is written by irradiating writing light and information is erased by irradiating erasing light, the readout light for reading information is An optical readout method characterized by using a mixture of the wavelength and the wavelength of erasing light at a predetermined intensity ratio.