JPH04240535A - Polygon scanner inspecting circuit - Google Patents

Abstract

PURPOSE:To simplify a large and complicate polygon scanner inspecting means, to directly view the final data and to confirm the changing state of the inclining amount of the surface of a polygon mirror at real time. CONSTITUTION:This inspecting circuit is comprised of a detector 8 which detects the position of beams incident upon a surface 5a of a polygon mirror 5, an operational circuit 12 to which signals from the detector 8 are input through an amplifier 10 and which outputs the changing amount of the position of incidence of the light upon the polygon mirror as an analog signal, and a data converting circuit 17 which samples analog signals by means of two sample- holders 16, 18 for an interval of one plane of the rotating polygon mirror 5 and confirms the difference of the sample data outputs from the sample holders thereby to obtain a voltage signal indicating the inclining amount of the adjacent surface of the polygon mirror.

Description

[Detailed description of the invention]

0001

The present invention relates to a polygon scanner inspection circuit used for inspecting the accuracy of mutual mirror surfaces of polygon mirrors (rotating polygon mirrors) of a polygon scanner used for optical scanning.

0002

2. Description of the Related Art A conventionally used test circuit of this type is shown in FIG. The beam from the light source 6 is reflected on the surface 5a of the polygon mirror 5 of the polygon scanner 4 which is rotated by the current supplied from the DC power supply 2 to the motor driver 3, and this reflected light is sequentially sent to the optical position detector 8 made of semiconductor or the like. input, output as a position displacement analog voltage signal, and output it as a position displacement analog voltage signal to amplifier 1.
0, converted into a logical signal by an A/D converter 13 via a synchronous circuit 11, and subjected to calculation processing in a computer 15,
This is to know the tilt status of the rotating polygon mirror 5. This method reduces the burden on electronic circuits and relies on software processing. Also, data is taken in using a sample clock.

0003

[Problems to be Solved by the Invention] In the above-mentioned conventional example, since a computer is used, the system itself inevitably becomes large-sized, leading to an increase in cost. Since the output cannot be directly viewed, there have been problems such as difficulty in checking changes in real time.

0004

[Means for Solving the Problems] Accordingly, an object of the present invention is to grasp the movement of actual displacement detection in real time, and means for achieving this object are provided below. The light reflected on the rotating polygon mirror surface is detected by an optical position detector, and then an analog voltage signal representing the amount of change in the light incident position on the polygon mirror surface is outputted from an arithmetic circuit via an amplifier, and this analog voltage signal is rotated. Samples are taken with two sample holders at intervals of one surface of the polygon mirror to be used, and by checking the difference in the sampling data output from these two sample holders, a voltage signal indicating the amount of surface tilt of adjacent polygon mirror surfaces is obtained. A polygon provided with a means for providing a data conversion circuit, further connecting a determination circuit or a display circuit to the output of this circuit, and allowing the display circuit to directly view the amount of surface tilt of adjacent surfaces of the polygon mirror in real time. This is a scanner inspection circuit.

[0005]

[Operation] The analog voltage signal representing the amount of change in optical position is converted into a synchronization signal that toggles every scan using a synchronization clock pulse generator and a data selector, and the position voltage is sampled using this signal. Data sampling is performed on the surface n+1 adjacent to the surface n of the polygon mirror. This 2
By taking the difference between the two samplings using a differential amplifier and then performing full-wave rectification, it is possible to directly view the mutual angle of the positive adjacent polygon mirror surfaces as a voltage.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the polygon scanner inspection circuit of the present invention will be described below with reference to the accompanying drawings. Figure 1(A),
In (B), the beams from the light source 6 are sequentially incident on and reflected by the surface 5a of the polygon mirror (rotating polygon mirror) 5 of the polygon scanner 4, which is rotated at a predetermined speed by the motor driver 3 connected to the DC power source 2. The reflected light becomes a photocurrent at the optical position detector 8. Semiconductor position detection element of optical position detector 8 (position sensitive detector P
Photocurrents Y1 and Y2 detected by SD) are amplified by an amplifier 10 and input to an arithmetic circuit 12. This photocurrent Y1, Y2
The relationship between the incident position and the following equation is as follows. In the above formula, L is 1/2 of the length of the element.

The Y1 and Y2 signals are input to an arithmetic circuit 12, and an analog position voltage signal 14 is obtained as a result of the above calculation. At this point, it cannot be used as is as a positional quantity. Therefore, an accurate position voltage value can be obtained by sampling this signal by synchronizing it with the timing of light incidence on the optical position detector 8 using the synchronous clock pulse generator 22 and data selector 20 of the data conversion circuit 17. be.

The circuit according to the present invention obtains the angle of inclination of the surfaces of adjacent polygon mirrors as a voltage value from data sampling. It is composed of a wave rectifying means 26. As mentioned above, the synchronization signal that toggles every scan by the synchronization clock pulse generator 22 and the data selector 20 passes through the data selector 20 and is sent to the first
The data is supplied to a sample holder 16 and a second sample holder 18, and holds data on every other surface 5a of the polygon mirror 5, respectively. For example, the first sample holder 1
6 holds data for two scans of the polygon mirror 5, and
Compare with the output of the sample holder 18. That is, the analog position voltage signal 14 sequentially output from the arithmetic circuit 12
are alternately input to the sample holders 16 and 18 which operate mutually, and hold data for each surface 5a of the polygon mirror 5.
Sampling is switched by 0, and the obtained sample data is input to the differential amplifier 24, and by becoming a difference between these signals, a difference in data on adjacent surfaces of the polygon mirror is obtained. However, since this differential data output is a signal that swings positive and negative, this differential data output is sent to the full-wave rectifier 2.
6 performs full-wave rectification to obtain the absolute value of the difference data. Furthermore, if a comparator or the like having a voltage reference is connected to the absolute value signal of the difference data, it will serve as a determiner 32, and if an analog display 30 is connected, the amount of change in the adjacent surface of the polygon mirror can be monitored in real time. In this way, the amount of change in the adjacent surfaces of the polygon mirror can be directly observed in real time.

Next, a circuit according to the present invention will be explained with reference to FIG. 2, which shows a timing chart for determining adjacent tilt data and synchronizing. The analog position voltage signal 14 shown in FIG. 1(B) is the analog input signal shown in FIG. 2, and is a sinusoidal voltage signal. This analog input signal is a light incident position signal obtained in synchronization with the synchronization signal of the polygon mirror surface. Each peak voltage of the waveform of this analog input signal is
This is an effective amount for the light incident position. To store the peak value of the analog input voltage for each adjacent side, two
Using the second analog sample holder 16, 18, the first
The sample holder 16 is placed on the odd-numbered side of the polygon mirror 5, the second
The sample holder 18 stores the positions of light incident on the optical position detector 8 from even-numbered surfaces. When the polygon mirror 5 is formed of odd-numbered faces, the odd-numbered faces and even-numbered faces are exchanged every rotation, but the first and second sample holders 16,
18 have no uniqueness and are the same, so no problem arises. The peak value of the analog input signal is stored using sample pulses generated by the synchronous clock pulse generator 22 for each surface 5a of the polygon mirror 5. In order to hold data alternately in the first and second sample holders 16 and 18, a sampling switching signal from the data selector 20 is used to hold the data on the surface of the polygon mirror 5.
The first and second sample holders 16 and 18 are placed on every other side of a.
Perform each sample pulse switch to . As shown in FIG. 2, sample pulses are generated for each polygon mirror surface in synchronization with the wave height peak value of the analog input signal. This sample pulse is alternately distributed to the first and second sample holders 16 and 18 by a sampling switching signal. As a result, if the captured data of a certain surface of the polygon mirror is the n-th data, this data is held in the first sample holder 16, the n+1-th data is held in the second sample holder 18, and the n+2-th data is held in the first sample holder 18. Data holding is performed alternately such that the (n+3)th data of the sample holder 16 is held in the second sample holder 18. In other words, one sample holder holds one piece of data between two surfaces, but since the two sample holders hold the data one side at a time, it is possible to compare the difference in the light incident position on adjacent surfaces. .

By inputting the outputs of the first and second sample holders 16 and 18 to the differential amplifier 24 and obtaining the difference between the sample data of each sample holder, it is possible to obtain the voltage signal of the adjacent polygon mirror surface. can. Since the magnitude relationship between the peak values of the even-numbered and odd-numbered analog input signals is uncertain (see differential signal in Figure 2), the operational amplifier 2
The output from 4 becomes bipolar data. In order to convert this bipolar data into unidirectional data, it is full-wave rectified by a full-wave rectifier 26 to obtain a final output (rectified signal in FIG. 2).

[0011]

[Effect] According to the present invention, the analog signal representing the amount of change in the position of light incident on the polygon mirror from the arithmetic circuit is sampled using two sample holders, and by checking the difference in sampling, the amount of surface tilt of the polygon mirror can be determined. In addition to providing a circuit that obtains a voltage signal representing With this circuit configuration, it is possible to check the amount of surface inclination of the adjacent surfaces of the polygon mirror and directly view the amount of surface inclination in real time. It is possible to obtain a simple inspection circuit that does not require a complicated and large analog signal conversion means as in the conventional example.

[Brief explanation of the drawing]

FIG. 1(A) is a block diagram of a polygon scanner inspection circuit according to the present invention.

FIG. 1(B) is a block diagram showing details of the data conversion circuit of FIG. 1(A).

FIG. 2 is a timing chart of waveforms for determining surface tilt data of adjacent surfaces of a polygon mirror according to the present invention.

FIG. 3 is a chart showing the difference between adjacent surfaces of the polygon mirror according to the present invention according to an analog input signal.

FIG. 4 is a block diagram of a conventional polygon scanner inspection circuit.

[Explanation of symbols]

5 Polygon Mira 5a Polygon mirror reflective surface 8 Optical position detector 10 Amplifier 12 Arithmetic circuit 14 Analog position voltage signal 16 First sample holder 17 Data conversion circuit 18 Second sample holder 20 Data selector 22 Synchronous clock pulse generator 24 Differential amplifier 26 Full wave rectifier 30 Display 32 Judgment device

Claims (3)

[Claims] 1. An optical position detector that detects the position of the beam incident on the surface of the polygon mirror, and a calculation that inputs the signal from the optical position detector via an amplifier and outputs it as an analog signal of the amount of change in the light incident position of the polygon mirror. The circuit and the analog signal are sampled with two sample holders at one surface interval of the rotating polygon mirror, and by checking the difference in the sample data output from these two sample holders, the amount of surface tilt of adjacent polygon mirror surfaces can be determined. A polygon scanner inspection circuit consisting of a data conversion circuit that obtains a voltage signal representing . 2. A pair of sample holders capable of storing an AC waveform peak value of an analog position voltage signal from an arithmetic circuit, and a synchronous clock generating a sample pulse for the sample holder to hold the peak value. a pulse generator; a data selector that issues a sampling pulse switching signal to cause the pair of sample holders to alternately hold data; a differential amplifier that obtains a difference between the data held by the pair of sample holders; 2. The polygon scanner detection circuit according to claim 1, further comprising a data conversion circuit comprising a full-wave rectifier for full-wave rectifying bipolar data from a dynamic amplifier into unidirectional data. 3. The polygon according to claim 1, further comprising a determination circuit or a display circuit connected to the full-wave rectifier, and the display circuit allows the amount of surface inclination of adjacent surfaces of the polygon mirror to be directly observed in real time. Scanner detection circuit.