JPH046637A - Red/write power current generating circuit for optical disk - Google Patents

Abstract

PURPOSE:To supply a prescribed write power current by subtracting a signal representing a read power current from a signal representing an object of a write power current, generating a current based on the result of subtraction and outputting the current to a laser diode together with the read power current. CONSTITUTION:A read power current detection circuit 8 detects a read power current IR from a voltage generated across a resistor 13 and outputs voltage signal VIR equivalent to the current IR. A subtractor 9 outputs a voltage signal (VIW-VIR) being a difference between the voltage signal VIW and the voltage signal VIR to be inputted. That is, a voltage signal (VIW-VIR) being a difference between the voltage signal VIW and the voltage signal VIR equivalent to the read power current IR supplied to a laser diode 12 is outputted from the subtractor 9 to a write current control circuit 10 and a voltage decided by the voltage signal (VIW-VIR) is applied to a base of a transistor (TR) 11. Thus, a prescribed write power current is supplied automatically with respect to a change in the read power current without preparation of a table for each of plural read power currents.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical disk read/write power current generation circuit used in an optical disk medium evaluation device, an optical disk medium inspection device, etc. First, the present invention relates to a read/write power current generation circuit for an optical disc that can automatically supply a constant write power current.

[Prior Art] In an optical disk medium evaluation device, an optical disk medium inspection device, etc., the read power current 1+t and the write power current I4 (read power current IR<write power current 1.) supplied to the laser diode are arbitrarily set within a certain range. It is necessary to write/read data under various conditions and perform various tests.

In the conventional technology, tests were usually performed while the write power current 11 was held at a constant value (the write power Pu of the laser diode was constant) and the read power current IR was varied variously. In this case, in the prior art, the write power current Iw is configured to be obtained by adding a predetermined current 8 to the read power current IR that is always supplied (IR+IX = L, here I. constant), it was necessary to change the current IX to be added each time the value of the read power current 1+t changed.

[Problems to be Solved by the Invention] In the above-mentioned conventional technology, it is necessary to change the current IX to be added each time the read power current is changed, and furthermore, the current/laser power conversion characteristic of the laser diode is not linear. In addition, considering the situation where the write power current 9 is changed, multiple read power current values IR
For each case, it was necessary to provide a table representing the relationship between the added current (18) and the write power P1 of the laser diode. Therefore, in the prior art Q, a large number of the above-mentioned tables are required, and a memory for storing them is prepared, and each time a test is performed, the relationship between the current lx and the write power P2 is read out from this memory. Light power current 1i
1, which is very troublesome.

This invention solves the problems of the prior art described above, and allows the write power current 11 to be constant with respect to changes in the read power current IR without preparing a large number of tables.
Optical disc lead/lead that can automatically supply
The purpose of this invention is to provide a write power current generation circuit.

[Means for Solving the Problems] The read/write power current generation circuit for optical discs of the present invention includes read power current generation means for generating a predetermined read power current and outputting it to a laser diode, and read power current generation means. read power current detection means for detecting the magnitude of the read power current output from the read power current detection means, and subtracting a signal indicating the read power current value detected by the read power current detection means from a signal indicating the target value of the write power current. , generate a current based on the subtraction result,
The present invention is characterized in that it comprises a write power current generating means for outputting the read power current to the laser diode together with the read power current outputted from the read power current generating means.

[Effect]

According to the present invention, the signal indicating the read power current value is subtracted from the signal indicating the target value of the write power current, a current is generated based on the subtraction result, and the current is supplied to the laser diode together with the read power current. Therefore, it is possible to provide a read/write power current generation circuit for an optical disc that can automatically supply a constant write power current in response to changes in read power current without preparing a large number of tables.

[Example] The present invention will be described in more detail below with reference to Examples shown in the attached drawings.

The accompanying drawings are block diagrams illustrating one embodiment of the invention. First, the operation during REIT will be explained. In the accompanying drawing, the register l for storing the leet power current value is
The value of the generated power current is stored as a digital value. The read power current value stored in the register 1 is converted into a digital signal by the digital/analog converter 2 and input to the read current control circuit 3. The read current control circuit 3 applies a voltage determined by the digital signal to the base of the transistor 4 in order to output the read power current IR specified by the digital signal input from the digital/analog converter 2 as the emitter current of the transistor 4. Apply.

As a result, the transistor 4 outputs the read power current I, l as an emitter current to the laser diode 12, and the laser diode 12 receives the read power current lR and generates a laser beam. Here, the laser light irradiated from the laser diode 12 is irradiated onto a monitoring light receiving diode 5, and the light receiving diode 5 detects the laser power of the laser light irradiated from the laser diode 12, and transmits it to the read current control circuit 3. give feedback. As a result, the read current control circuit 3 controls the laser diode 1
2, the voltage applied to the base of the transistor 4 is controlled in order to bring the amount of light emission to a desired value. In other words, an auto power control circuit is realized.

Next, the operation during writing will be explained. The write power current value storage register 6 stores the value of the generated write power current as a digital value. The write power current value stored in the register 6 is converted into a digital signal by a digital/analog converter and inputted to one input terminal of the subtracter 9 as a voltage signal Vll. Further, voltage signals v and R proportional to the read power current 8 detected by the read power current detection circuit 8 are input to the other input terminal of the subtracter 9. That is, the read power current detection circuit 8 detects the read power current 1.0 from the voltage generated across the resistor 13. is detected, and a voltage signal Vll+ corresponding to this is output. The subtracter 9 outputs a voltage signal (Vow VIM) obtained by subtracting the voltage signal (2) from the input voltage signal VIW. That is, the voltage signal V corresponding to the current already supplied to the laser diode 12 as the read power current IR
A voltage signal (Vow VIR) obtained by subtracting IR is output from the subtracter 9 to the write current control circuit 10. The write current control circuit IO sends a current (Ii=III) corresponding to the voltage signal (Vow VIR) to the transistor 11.
In order to output it as an emitter current, the above voltage signal (V+s=VI++) is applied to the base of the transistor 11.
Apply a voltage determined by As a result, the transistor 11 has a current (Ism
Ii) is output to the laser diode 12. Therefore, the laser diode 12 has a read power current IR from the transistor 4 and a current (I
h L) is supplied, so that the laser diode 12
A write power current 11 corresponding to the digital value stored in the register 6 is supplied to the register 6 . In the above embodiment, it is sufficient to prepare one table showing the current-laser power characteristics of the laser diode 12.

As is clear from the above description, according to the present embodiment, the write power current (2) is constant with respect to changes in the read power current IR without preparing a table for each of a plurality of read power currents. can be supplied automatically.

〔Effect of the invention〕

According to the present invention, without preparing a large number of tables,
It is possible to provide a write power current generation circuit for an optical disc that can automatically supply a constant write power current in response to changes in read power current.

[Brief explanation of the drawing]

The accompanying drawing is a block diagram showing an embodiment of the optical disc read/write power current generating circuit of the present invention. 1.6...Register, 2.7...Digital/analog converter, 3...Read current control circuit, 4゜1
1... Transistor, 5... Light receiving diode, 8...
...Leat power current detection circuit, 9...Subtractor, 10
...Write current control circuit, 12...Laser diode, 13...Resistor.

Claims (2)

[Claims] (1) A read power current generating means that generates a predetermined read power current and outputs it to the laser diode, a read power current detecting means that detects the magnitude of the read power current output from the read power current generating means, and a write A signal indicating a read power current value detected by the read power current detecting means is subtracted from a signal indicating a target value of the power current, a current is generated based on the subtraction result, and the current is output from the read power current generating means. 1. A read/write power current generation circuit for an optical disc, comprising a write power current generation means for outputting a read power current to a laser diode together with a read power current. (2) The optical disc according to claim 1, further comprising means for detecting the amount of light emitted by the laser diode and feeding it back to the read power current generating means to control the generated read power current to an appropriate value. Read/write power current generation circuit.