JPH0695173B2 - Measuring device for scanning distortion of optical system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] The present invention relates to a scanning distortion inspection device for an infrared imaging device scanning unit.

Photoelectric conversion elements are arranged in an array at a fixed interval over the entire optical scanning amplitude, and a scanning beam having a diameter smaller than the arrangement pitch of the individual photoelectric conversion elements is passed through the scanning mirror to the photoelectric conversion element array. It is possible to detect the scanning distortion by detecting the pulse interval of the pulsed scanning signal which is sequentially applied to and detected, and collating it with the geometrical interval of the light receiving element fixed in advance. In this way, when measuring the pulse interval of the pulsed scanning signal, the self-identification circuit that automatically adjusts the threshold setting of the optical pulse signal according to the pulse height is used to bring automation to the measurement. It's a rare thing.

[Industrial application field]

This device is used for automatic inspection of the optical scanning section of an infrared imager.

The infrared imaging device itself is used as a device for measuring the temperature distribution of each part of a human body, an animal, etc. for medical use, and various temperature distributions of a completed product or unfinished parts for industrial use during operation.

Since these infrared detecting elements are in a technical state in which it is difficult to apply a two-dimensional detecting element capable of obtaining a two-dimensional image on the detecting element, a single element or an array element and a scanning operation corresponding to the element are performed. 2 in combination with the scanning optical system
Obtaining a three-dimensional image. It is a condition of the infrared imaging device that the scanning optical system has no scanning distortion.

The inspection measurement of the scanning distortion of this scanning system to which the present invention is applied is very important, but technically unfinished remains.

[Conventional technology]

One of the conventionally used scanning distortion measuring methods is shown in FIG. 4, and its display screen is shown in FIG.

In the figure, 1 is a laser light source, 2 is a scanning mirror, 6 is a measuring stand, 30 is one photoelectric conversion element for performing photoelectric conversion, 40 is an amplifier, and 45 is a two-phenomenon oscilloscope. The scan angle 2Q that gives the scan range 2X0 is the image measurement range angle.

Here, it is assumed that the relationship between the horizontal scanning time of the oscilloscope 5 and the displayed scanning distance is ideally a straight line without distortion.

The light beam emitted from the laser light source 1 scans the maximum measuring range 2X0 on the measuring table 6 by the scanning mirror 2. The scanning mechanism of the scanning mirror 2 has a marker pulse generating mechanism (not shown), and emits the marker pulse 10 shown in FIG. 5 when the light beam reflected by the mirror 2 passes through the center of the measuring table.

The marker pulse signal 10 indicating the center of scanning enters one input terminal of the two-phenomenon oscilloscope 45, and the output signal of the single photoelectric conversion element 30 which receives the laser beam is input to the other input terminal of the amplifier 40 by the amplifier 40. It is input after being amplified.

Here, the distance X from the center of the measuring table 6 to the single photoelectric conversion element 30
Is a value that is changed as a change amount to obtain measurement data, and corresponds to X, and the measurement amount Y for determining the presence or absence of scanning distortion is the output pulse of the photoelectric conversion element 30 that receives the scanning beam and the measurement. It is represented by the distance from the marker pulse 10 representing the center of the table.

The distance X from the center of the measuring table 6 to the light receiving element 30 and the positional interval Y between the two pulses of the measuring beam have a linear relationship if there is no scanning distortion.

Thus, on the surface screen of the two-phenomenon oscilloscope 45, the marker pulse 10 indicating the time when the light beam passed through the center position and the measured output pulse 11 delayed by the time required for the optical scanning as shown in FIG. Is displayed. It was investigated whether the interval Y between the two pulses has a linear relationship with the size of the measured position X of the light receiving element 30.

In other words, the marker gap amount Y on the oscilloscope display screen that scans with a sawtooth wave with ideal linearity
By sequentially changing the position X of the photoelectric conversion element in small increments, and drawing the relationship between the position X of the photoelectric conversion element and the marker gap amount Y in a graph. Was being judged.

[Problems to be solved by the invention]

The conventional measurement method has a drawback that the effort for collecting data is very large.

That is, not only is it difficult to accurately set the measurement system in which the relative positions of the laser light source, the scanning optical system, and the detection system are fixed, but also the position X of the light receiving element position X is finely moved in the measurement system. It is very difficult to ensure precision and reproducibility, such as delicate fine measurement, and measurement of the time required for optical scanning on the display screen that was tested with a light beam.

In the present invention, it is desired to perform the measurement more accurately than the precision and reproducibility of the measurement repeated manually, and to save labor.

[Means for solving problems]

FIG. 1 is a block diagram of the principle of the scanning distortion measuring method of the present invention.

In FIG. 1, 1 is a laser light source for generating a narrow laser beam, 2 is a scanning mirror, 3 is an array of photoelectric detectors, 4 is a self-identifying circuit, 50 is a clock generator, and 51 is the output of the self-identifying circuit with clock pulses. The subdivided modulator, 52 is a center detector for finding the center pulse of the pulse train within the identification wave output width,
A drawing unit 53 draws a graph by performing arithmetic processing on the obtained linearity data.

The present invention is configured by the above means.

[Action]

FIG. 2 shows again the apparatus first half processing section which is the main part of the scanning distortion measuring method of the present invention.

Individual light receiving elements D1 and D that form the photoelectric light receiving element array 3
In the output pulses of 2, ..., Dn, since the diameter of the light beam is sufficiently smaller than the mounting interval of the light receiving element, the detected light output is an electric pulse separated in time. By cutting the pulse at a certain threshold value, the center position of the pulse width, that is, the light receiving element
Find each point corresponding to the position of the photo detector on the D1, D2, .... Dn electric pulse, and plot each value on the two-dimensional coordinates to correspond to the geometric position of the element arrangement. Then, a scanning curve is drawn to determine the linear scannability of this optical system.

The reason for existence of the self-identification circuit 4 is that even if there are fluctuations and drifts in the intensity of the laser light, and even if the characteristics of the light receiving elements D1, D2 ,. The operating point is automatically adjusted by the self-identification circuit 4 during the measurement process by setting the fraction of the peak value of the detection pulse by the variable resistance VR, and measurement with good reproducibility is performed. .

〔Example〕

FIG. 3 shows an embodiment of a front stage portion from the center detecting portion 52 forming the core of the present invention.

Load resistances R1, R2, .... Rn on the photo detectors D1, D2, ...
After being connected, the amplifier A1 is collectively input to the amplifier A1 and converted into a low impedance by the amplifier A1, and then the self-identification circuit 4 is input.

The self-identification circuit 4 is known, but its operation will be briefly described as follows.
After passing through the amplifier A1, the input signal is split into two and enters the peak holder A2 and the comparator A3.

The signal entering the beak retainer A2 is diode DP and capacitor
The peak value of the input pulse is held by C1 and the impedance of the input pulse is lowered by the high input impedance amplifier A2 and output to the variable resistance VR.

The voltage output to the divided variable resistor VR is the peak proportional value of the input pulse, and the fraction of that value is used as the threshold value in one input of the comparator A3.

Then, it enters the other input terminal of the comparator A3, and the photodetectors D1 and D
The output signal amplified by 2, .... Dn and the peak value of the signal input to the other input terminal multiplied by a fractional value smaller than 1 are entered, and the comparator A3 sets the threshold value. The output signals of the light receiving elements D1, D2, ... Appears in the output. This threshold is self-set by the first several input signals at the start of the main measurement, and is determined by the light-receiving element outputs that are successively input during the measurement operation. Therefore, no human adjustment is necessary thereafter.

The output of the comparator A3 enters the modulator 51, the photoelectric conversion output width by the light receiving element is subdivided by the clock pulse from the clock 50, and the number of the subdivided pulses in the center detector 52 is counted to obtain the photoelectric conversion output width For example, the center is found, and the measurement position Y via the optical system of the photoelectric light receiving element array 3 is determined.

The position is the correct position Y of the pulse output from the light receiving elements D1, D2, ... Dn, and the light receiving elements D1, D2 ,.
Corresponding to the geometrical position X of Dn, the linearity of the scan is determined in the drawing device 53.

In this way, the scanning linearity of the optical system can be easily measured by the device.

〔The invention's effect〕

As described above, according to the present invention, by setting the optical scanning system to be measured in the measuring apparatus of the present invention, the display linearity of the optical scanning system to be measured can be automatically measured easily with less effort. Advanced, the difficult adjustment of the infrared detector optics can be done easily and accurately, which is really useful.

[Brief description of drawings]

 FIG. 1 is a block diagram of the principle of the present invention, FIG. 2 is a scanning distortion measuring method of the present invention, FIG. 3 is an explanatory view of an embodiment of the present invention, FIG. 4 is a conventional measuring configuration method, and FIG. Is an oscilloscope display screen by the conventional method. In the figure, 1 is a laser light source, 2 is a scanning mirror, 3 is a photoelectric light receiving element array, 4 is a self-identification circuit, 51 is a clock modulation circuit, and 52 is a center pulse detection circuit.

Claims (1)

[Claims] 1. A laser light source for projecting a light beam onto an optical scanning system, a scanning optical system for sequentially entering the light beam into a light receiving element array for receiving the light beam and converting it into an electric signal, and the converted electric signal at a predetermined level. In an optical system measuring device having a discrimination circuit for discriminating in, the discrimination level of the discrimination circuit is variably controlled according to the peak level of the electric signal generated by the light beam, and the electric signal output from the discrimination circuit An optical system scanning distortion measuring device, characterized in that a light reception timing of the light receiving element is determined from a time interval between the rising portion and the falling portion of the light receiving element.