JPS6132324Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical dimension measuring device, and more particularly to a device for compensating for magnification errors in an optical system due to movement of an object to be measured.

Recent optical dimension measuring devices use a condensing optical system to measure the position of a slit that moves at a constant speed or the position of a complementary number of photoelectric conversion elements arranged at equal intervals in a straight line along the dimension measurement direction. The dimensions of the object to be measured are measured by forming an image of the object and using the pulse width obtained by scanning a slit or the number of pulses obtained by scanning a plurality of photoelectric conversion elements.

For example, in the dimension measuring apparatus shown in FIG. 1, an object to be measured 10 is connected to a light sensor 1 consisting of a plurality of photoelectric conversion elements P ₁ to _{P o} as shown in FIG. 2 using a condensing optical system 11.
The dimensions of the object to be measured 10 are measured by multiplying the number of pulses obtained from the optical sensor by a constant. The optical sensor is provided with a plurality of photoelectric conversion elements P ₁ , P _{2 .} . . P _o arranged in a straight line at equal intervals as shown in FIG. Multiple analog switches S ₁ , S ₂ , S ₃ ...S connected wire-or-side
_o , a pulse generating circuit _12-1 that generates pulses at a predetermined period, counts these pulses, and sequentially closes the analog switches S ₁ , S ₂ ,...S _o to output the output level state of each photoelectric conversion element. It consists of a scanning circuit _12-3 generated at the end _12-2 , and is used in the field of dimension measurement of objects to be measured because it does not have mechanical elements. Note that _12-4 and _12-5 indicate output terminals for the output signal of the oscillator, and terminals for outputting a signal indicating that the scanning circuit is performing one scan.

By the way, even if this type of optical sensor is used, even if it is a slit-type dimension measuring device, an optical system is used to form an image of the object to be measured on the slit or the optical sensor surface, so there is a difference between the optical system and the object to be measured. When the distance between them changes from A to B, the magnification of the optical system changes, and this is included in the measured value as a magnification error. Various methods have been considered to reduce the magnification error, but in any case, a new device for detecting the position of the object to be measured is installed in the dimension measurement system, and the measurement system is based on the output of the position detector. The magnification error is compensated for.

A disadvantage of this type of device is that it must be equipped with a position detector.

The purpose of the present invention is to detect the distance between the object to be measured and the optical system from the amount of blur on the slit surface or the light receiving surface of the photosensor due to distance fluctuations between the optical system and the object to be measured, and to ensure that the amount of blur is always constant. It is an object of the present invention to provide an optical dimension measuring device which controls the position of an optical system so as to move it closer to or farther away from the object to be measured so as to maintain a constant position, and is capable of compensating the magnification using a sensor of the measurement system.

For an outline of how to achieve this purpose, please refer to Figure 3, which shows the relationship between the output level of each photoelectric conversion element of the optical sensor in the edge image of the object to be measured with respect to the distance between the object to be measured and the optical sensor. I will explain. However, the high level state indicates the output level of the photoelectric conversion element in which the light is not blocked by the object to be measured. Note that in the case of a red-hot object to be measured, the output of the photoelectric conversion element on which the object is imaged will be at a high level.

When the object to be measured 10 is located at position A in FIG. It is set in advance to form a sharp image so that the level difference changes rapidly. When the object to be measured 10 moves to a position B which is a distance of Δx from the position A, the optical system 11 moves to the optical sensor 1.
The edge image of the object to be measured 10 on the light receiving surface 2 gradually decreases in level, that is, becomes blurred, as it moves further away from the edge position as shown in FIG. 3B.

When the object to be measured 10 is moved closer to or further away from the optical system than the position A, the blur area changes; at the position A, the amount of blur is small and almost zero, and the further away from the position A, the wider the blur area becomes. As can be understood from this, the blur area has a close relationship with Δx, and Δx maintains a direct and close relationship with the magnification error. Therefore, it is understood that the dimensions of the object to be measured can be accurately measured by focusing on the blurred region and moving the optical system and the optical sensor of the measurement system together to keep the blurred region constant.

Next, a blur amount detection circuit for measuring the amount of blur area will be explained with reference to FIG.

The blur amount detection circuit connects an input terminal 13 to an output terminal _12-2 of the optical sensor 12 of the measurement system.
The terminal 13 is connected to one input terminal of first and second comparator amplifiers 14 and 15, respectively, which compare signals at a pair of input terminals. The first comparator amplifier 14 has its other input connected to the output side of a potentiometer 16 which outputs a level _{of V 1 as} shown in FIG. It is output every time the output of the measurement system optical sensor of a level lower than that occurs. The second comparator amplifier 15 is connected to the output side of the potentiometer ₁₇ which outputs the level of _V2 as shown in FIG. It is. Note that the _V1 level is set in advance so that it is always lower than the output level of each photoelectric conversion element of the measurement system optical sensor when light is incident. On the other hand, the V ₂ level is noisy and
Set to a low level that can sufficiently eliminate dark current, etc., and lower than the _V1 level. The output of each comparator circuit is led to a compensation calculation circuit 18. In addition, the compensation calculation circuit 18, which also leads the one-scanning signal outputted from the scanning circuit _12-3 and the output of the oscillator, calculates a value based on these inputs. Compensation calculation is performed to detect each photoelectric conversion element of the measurement optical sensor having a peak level between the _V1 level and the _V2 level, and output a signal corresponding to the number of photoelectric conversion elements. By extracting the blur area as the number of photoelectric conversion elements using a measuring device having such a circuit configuration, the distance Δx can be naturally determined. This Δ
Once the distance x is measured, the magnification error of the optical system can be eliminated by positioning the object to be measured at a condition position determined by the position of the measurement system optical sensor with respect to the optical system. For example, the output of the compensation calculation circuit 18 is applied to a servo system, and the servo system moves the integrated optical system and measurement system optical sensor in the optical axis direction of the optical system, thereby adjusting the V ₁ level and V ₂ level. The number of photoelectric conversion elements that take a peak value between the levels is made equal to a predetermined value. As a result, the distance between the optical system and the object to be measured is always maintained at a predetermined value. If the distance between the optical system and the object to be measured, which changes its position from time to time, is maintained at a predetermined value, magnification errors in the optical system caused by vertical movement or one-sided upward movement of the object to be measured will not occur, and the focus will always be maintained. Since a matched image of the object to be measured is generated on the optical sensor surface of the measurement system, there can be a large difference in output between the photoelectric elements that receive the light and those that do not.
Output end 12 of the optical sensor of the measurement system for dimension measurement
- It has become easier to determine the discrimination level for discriminating the outputs of ₂ , and the reliability of dimension measurement values has been improved.

As described above, the present invention extracts the amount of blur of the image formed at the end of the object to be measured into a digital value, and measures that value as the amount of distance variation between the object to be measured and the optical system. By integrating the optical system and the sensor to maintain the distance to the object to be measured at a predetermined value, a severe end image of the object to be measured is formed on the light receiving surface of the optical sensor, resulting in optical interference. It has been possible to provide an optical dimension measuring device that can accurately measure the dimensions of an object by eliminating magnification errors in the system.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic configuration of a detection section of a conventional optical dimension measuring device, FIG. 2 is a diagram showing an electrical configuration of an optical sensor circuit, and FIGS. 3A and 3B are diagrams showing the principle of the present invention. FIG. 4, which is a diagram for explanation, is a block configuration diagram of a blur amount detection circuit for implementing the present invention. 14/15... Comparison amplifier, 16/17... Potentiometer, 18... Compensation calculation circuit.

Claims (1)

[Scope of utility model registration request] A plurality of photoelectric conversion elements are arranged in a straight line along the dimension measurement direction at an imaging position of the end of the object to be optically imaged, and the plurality of photoelectric conversion elements are sequentially scanned. a scanning circuit that outputs the output level of each element obtained through the process, and a first high level slightly lower than the high level of the output level of each photoelectric conversion element, and a second level lower than the first level, respectively. and a correction circuit that counts the number of photoelectric elements that have an output level between the first level and the second level in each scan at least, and outputs a signal corresponding to the number, and the output of the correction circuit. 1. An optical dimension measuring device, characterized in that an optical system and a plurality of photoelectric conversion elements are integrally positioned and controlled so that a constant value is always maintained, and a magnification error of the optical system is corrected.