JPH01153920A - Dropout measuring instrument - Google Patents

Abstract

PURPOSE:To grasp the state of a dropout quantitatively as a material for deciding whether or not the exposure quality of a manufactured original disk is normal and to improve the efficiency of operation by measuring the depth, length, and position of a dropout of exposure laser light in an original disk exposing machine for an optical disk. CONSTITUTION:Branch laser light branched by a half-mirror 2, etc., from the main optical axis of the exposure laser light from a laser light source 1 is photodetected by a photoelectric converting element 3. A conversion signal corresponding to the quantity of photodetection is inputted to a dropout detecting circuit 4. Then the circuit 4 sets a threshold level for the mean output level of the conversion signal and the threshold level is compared with the conversion signal to detect the dropout of the laser light and finds its depth. Further, length data and position data on the dropout are obtained by a counter circuit 6 and a formatter 7. Then those data are stored 8 temporarily by a control part 5 and then outputted 9 after an exposure process is finished.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a dropout measuring device for a laser beam for master exposure in an optical disc master exposure machine.

BACKGROUND OF THE INVENTION Generally, in the manufacturing process of an optical disc, if a dropout occurs in the laser beam during exposure of the optical disc master, it is extremely difficult to detect the defect in subsequent processes. Furthermore, from the viewpoint of preventing defects in the optical disc, it is preferable to eliminate the need for manual operations such as microscopic observation. For this reason, dropout characteristics can only be confirmed after the optical disc is manufactured by observing signals using an optical disc drive or the like.

Such a dropout measurement method results in a large waste of time required to confirm the characteristics. However, if an optical disc goes on the market without detecting dropouts, matching may become impossible due to changes in the drive over time, etc.
This causes quality deterioration problems such as off-track.

In this regard, if the occurrence of dropouts, including their characteristics, can be detected during exposure of the original, wasteful manufacturing time in subsequent steps can be omitted, and a dropout measuring device for this purpose is desired.

Purpose The present invention has been made in view of the above points, and is to measure the depth, length (time), and position (sector address) when a dropout of an exposure laser beam occurs in an optical disk master exposure machine. By this, we can obtain a dropout measurement device that can quantitatively grasp the dropout condition, clarify the exposure quality of the produced glass master, and judge its quality, thereby improving work efficiency in the next process and thereafter. The purpose is to

Structure In order to achieve the above object, the present invention provides a photoelectric conversion element that receives and photoelectrically converts a branched laser beam branched from the main optical axis of a laser beam for exposing a master of an optical disc, and a conversion device output from this photoelectric conversion element. A dropout detection circuit in which a plurality of threshold levels are set with respect to the average output level of a signal and performs comparison with the converted signal to detect a dropout of a laser beam and obtain depth data thereof; and this dropout detection circuit. A counter means that measures the time from the occurrence of a dropout to recovery time and obtains dropout length data, and a counter means that controls recording of address information on the master disc during master disc exposure, and when a dropout is detected, it measures the dropout position from the sector address. This apparatus is characterized by comprising a formatter for obtaining data, and a control section for temporarily storing the depth data, length data, and position data in a recording device and outputting them after the exposure process is completed.

An embodiment of the present invention will now be described based on the drawings. First, a laser light source 1 is provided that emits laser light for exposing a glass master disc of an optical disc. This laser light source 1 is a semiconductor laser, a gas laser, or the like. A photoelectric conversion element 3 is provided that receives branched laser light branched from the main optical axis of the exposure laser light from the laser light source 1 by a half mirror 2 or the like. The second photoelectric conversion element 3 outputs an electrical conversion signal that is photoelectrically converted according to the amount of received branched laser light, and is constituted by, for example, a pin photodiode. Next, this photoelectric conversion element 3
A dropout detection circuit 4 receives a conversion signal from
is provided. This dropout detection circuit 4 is connected to a control unit (CPU) 5 via a data bus.

A counter circuit 6 as a counter means and a formatter 7 are connected to the control section 5, and a storage device (memory) 8 and an output device 9 are connected to the output side.

As shown in FIG. 2, the dropout detection circuit 4 includes a buffer amplifier 41 for receiving a conversion signal, an average output level circuit 42, a threshold level V ref setting circuit 43, a comparator 44, and a latch circuit 45. The converted signal amplified by the buffer amplifier 41 is directly input to one input Vin of the comparator 44 on the one hand, and is input to the average output level circuit 42 on the other hand. Based on the conversion signal, this average output level circuit 42 sets the average output level of the pseudo DC level, which is not influenced by the pulse-like fluctuation, to the threshold level Vre.
It is output to the f setting circuit 43.

This V rcf setting circuit 43 sets a threshold level Vref to be compared with the raw converted signal voltage Vin as a comparison reference voltage based on the average output level, and sets it as the other input of the comparator 44 .

Here, the V ref setting circuit 43 sets multiple threshold levels V ref, , V as shown in FIG.
ref2°~, VrefN can be set arbitrarily. In this embodiment, for example, each threshold level is Vref, = 80%, Vre
f, = 60%, Vref, = 40%, Vref,
= 20%, and four threshold levels are set in the depth direction for depth detection when dropout occurs in the converted signal.

Therefore, first, the dropout detection operation by this dropout detection circuit 4 will be explained. Now, consider a case where a dropout as shown in FIG. 4 occurs in the laser light (converted signal). At this time, the comparator 44 outputs a dropout detection trigger signal at L level at the moment the voltage Vin of the raw data (conversion signal itself) falls below the highest threshold level Vref. Thereafter, the voltage Vin of the raw data is set to this threshold level Vr.
ef.

Continue until recovery. During such an operation, when the voltage Vin crosses the threshold level Vref, the threshold level Vref from the comparator 44 and the detection flip-flop trigger signal are output to the latch circuit 45. Furthermore, it is depressed and other threshold levels V
Vref, from comparator 44 when voltage Vin crosses ref, , Vref, etc.

A detection flip-flop trigger signal such as Vref is similarly output to the latch circuit 45. In the case of the conversion signal shown in FIG. 4, detection flip-flop trigger signals from Vref to Vref are output to the latch circuit 45.

A detection trigger signal from such a dropout detection circuit 4 is input to a counter circuit 6.

In this counter circuit, as shown in FIG. 3, the fundamental frequency is always input as the clock signal CLK to the CLK terminal, and a dropout detection trigger signal can be input to the EN terminal.

As a result, the counter circuit 6 has a valid counter operation while the detection trigger signal is output at L level, that is, during the dropout duration time, and the clock CL during that period is valid.
Count the number of K pulses.

Therefore, (period of fundamental frequency) x (number of counts) is the length data from the time of dropout occurrence to the time of recovery (fourth
(corresponding to the time mark in the figure) is measured.

Furthermore, the detection trigger signal from the dropout detection circuit 4 is also output to the format tough. This formattuta 7
1 is a circuit for controlling sector address recording during exposure of a master disc, and latches sector address information as position data at the time when a detection trigger signal is input, that is, when a dropout occurs.

In the control unit 5, the detection trigger signal from the dropout detection circuit 4 becomes an interrupt signal, and when this detection trigger signal is input manually, each data, that is, the depth direction latch data (depth data ), length direction count number data from the counter circuit 6,
The sector address latch data from the formatter 7 is read, and depth, length, and position data related to dropout characteristics are collected. In the control section 5, when such a reading operation is completed, each circuit 4,
6.7, the latch flip-flop of the dropout detection circuit 4 and the counter circuit 6
, and reset the address latch circuits of the formatter 7, respectively. Further, when the reading of each data is completed, the control unit 5 temporarily stores each data in the storage device 8.

Such a series of operations is repeated under the control of the control section 5 until the master exposure process is completed.

When the exposure process is completed, the control unit 5 sequentially takes out each piece of data stored in the storage device 8 and outputs it to an output device 9 such as a printer, CRT, or plotter.

As described in 2, dropout is measured during exposure of the master disc, and if dropout occurs, its characteristics can be quantitatively understood, and the quality of the exposed glass master disc can be clarified. . Therefore, by making a quality/failure judgment, when a dropout occurs, it is possible to eliminate wasted time such as quality confirmation in the steps after the master exposure step, and improve work efficiency.

Effects Since the present invention is configured as described above, it is possible to quantitatively grasp the characteristics such as depth, length, position data, etc. related to dropouts when a dropout occurs in the laser beam for master exposure, and therefore, the production This can be used as material for determining whether the exposure quality of the exposed master is good or bad, and it is possible to eliminate wasted time such as checking the quality in the next process and thereafter, and improve work efficiency.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a block diagram, FIG. 2 is a block diagram of a dropout detection circuit,
FIG. 3 is a block diagram showing the operation of the counter circuit, and FIG. 4 is a waveform diagram.

Claims (1)

[Claims] a photoelectric conversion element that receives and photoelectrically converts branched laser light branched from the main optical axis of the laser light for exposing the master of the optical disc;
A plurality of threshold levels are set for the average output level of the conversion signal output from this photoelectric conversion element, and the dropout is compared with the conversion signal to detect a laser beam dropout and obtain its depth data. A dropout detection circuit, a counter means for measuring the time from the occurrence of dropout to recovery by this dropout detection circuit to obtain dropout length data, and controlling recording of address information on the master disc during exposure of the master disc to detect dropout. It consists of a formatter that obtains dropout position data from the sector address at the time of detection, and a control unit that temporarily stores the depth data, length data, and position data in a recording device and outputs them after the exposure process is completed. Characteristic dropout measuring device.