JPH0226041Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a device that automatically focuses on an object to be focused on in a short period of time.

In a temperature measuring device, for example, as shown in FIG. 1, an optical system consisting of a scanning mirror 1, a condensing mirror 2, and a lens 3 is used to form an image spot of an infrared detector 4 on a subject, and The image spot is scanned. In this case, focusing is performed by observing the infrared image signal waveform obtained from the infrared detector 4 and manually moving the condensing mirror 2 back and forth in the direction of the arrow to find the position where the waveform is the sharpest. However, it was a cumbersome task that required skill.

Now, the fact that the video signal waveform sharpens when it comes into focus means that if we focus on the differential signal of the video signal, we can think of the peak value of the differential signal increasing. In other words, if the peak value of the differential signal of the video signal is monitored and the position of the condensing mirror at which the peak value is maximized is determined, correct focus will be achieved at that position. Recently, based on this idea, the infrared detector is capable of focusing the image spot of the infrared detector on the subject by scanning the image spot on the subject while sweepingly changing the focal length of the optical system for forming the image spot of the infrared detector on the subject. Find the differential signal of the signal obtained in , store the signal corresponding to the focal length of the optical system when the differential signal shows the maximum value, and calculate the focal length of the optical system based on the stored signal. An apparatus has been proposed in which focusing is automatically performed by setting the differential signal to a value when the differential signal shows a maximum value.

However, in such an apparatus, since the sweep range of the means for sweeping and changing the focal length of the optical system is fixed in advance, it is possible to sweep and change the entire fixed range. The maximum peak value of the differential signal of the video signal is determined while moving within a fixed entire range, and the condensing mirror is moved to the position where the maximum peak value is determined. It takes a lot of time. In addition, the fixed range often includes objects other than the target object, and if the temperature change of the object other than the target object is sharper than that of the target object, the non-target object may be in focus. I get tired.

The present invention aims to solve such problems.

With this invention, the target object can be seen with the naked eye, and the distance to the object can be roughly estimated.
The above problem is solved by limiting the focus adjustment range to the range length in the vicinity of the object. a scanning means for scanning the image spot on the subject, a differentiating means for obtaining a differential signal of the signal obtained by the infrared detector by the scanning, and a time when the differential signal shows a maximum value. Storage means for storing a signal corresponding to the focal length of the optical system; and for setting the focal length of the optical system to a value when the differential signal shows a maximum value based on the signal stored in the storage means. The object of the present invention is to provide a focusing device for a novel temperature measuring device, in which the sweeping range of the sweeping means can be arbitrarily set depending on the object to be focused.

FIG. 2 shows an embodiment of the present invention, and the same numbers as those used in FIG. 1 indicate the same components.

In FIG. 2, the scanning mirror 1 is repeatedly horizontally scanned by a motor 5 at regular intervals. The condensing mirror 2 is provided movably in the direction of the arrow by the rotation of a threaded rod 7 that is screwed into a nut 6 attached to the back surface. Reference numeral 8 denotes a pulse motor coupled to the threaded rod 7, and the motor 8 receives a horizontal synchronization signal received from the motor 5 via an up-down counter 9 that counts the horizontal synchronization signal generated for each horizontal scan. Since pulses generated by the control circuit 10 based on the above-mentioned signals are supplied via the switch 11, the motor 8 rotates by a predetermined angle for each horizontal scan. Therefore, the condensing mirror 2 is sequentially moved in steps for each horizontal scan. By repeating the horizontal scanning, the infrared image signal obtained from the infrared detector 4 is sent to the differentiating circuit 13 via the amplifier 12. The output of the differentiating circuit 13 is passed through the diode 14, and only the positive signal is sent to the AD converter 15.
is sent to the maximum value detection circuit 16 via
The maximum value is found. The maximum value detection circuit consists of a first latch circuit 17 and a comparison circuit 18. 19 is a second latch circuit for storing the position of the condenser mirror 2 when the maximum value is detected; the latch circuit includes the up-down counter 9 for counting the horizontal synchronization signal generated from the motor 5; The output of the switch 20 is supplied as a position signal through the switch 20. The up-down counter 9 is configured to be loaded with a number of pulses from the third latch circuit 21 corresponding to the forward movement start position of the condensing mirror 2, and
The control circuit 10 is supplied with a number of pulses corresponding to the return movement start position of the condensing mirror 2 from a fourth latch circuit 22, and the control circuit receives pulses sent from the up-down counter 9. When the number becomes equal to the number of pulses from the fourth latch circuit 22, that is, the number of steps from the forward movement start position to the return movement start position set by the object to be measured by the condenser mirror 2 is reached. When the movement is completed, the rotation direction of the pulse motor 8 is reversed,
The condenser mirror 2 is moved in the returning direction, and an inversion signal R is issued to switch the counter 9 to the down mode, and the switch 20 is also switched. During this return period, the coincidence circuit 23 compares the output of the counter 9 and the output of the first latch circuit 19,
When the two match, a match signal A is generated. The switch 11 is turned off by this coincidence signal.
Therefore, the pulse motor 8 stops.

In such a device, first, the switch 11
Then, the distance from the optical system to the object whose temperature is to be measured is visually measured, and the number of pulses corresponding to the distances L ₁ and L ₂ to the points before and after approaching the object is applied to the third and third pulses, respectively. 4 latch circuits 21 and 22. The third latch circuit 21 loads the up-down counter 9 with a pulse corresponding to the set distance L ₁ in front of the object, and the fourth latch circuit 22
supplies the control circuit 10 with a number of pulses corresponding to the set distance _L2 behind the object. By loading the pulse corresponding to _L1 into the counter, the control circuit 10 sends the pulse from the counter to the pulse motor 8 via the switch 11, so that the condenser mirror 2 moves to the position l corresponding to _L1 . Instantly move to ₁ . Further, at the same time as the third latch circuit loads the pulse, it sends an operation start signal to the motor 5 via a delay circuit (not shown), so that the scanning mirror 1 begins to horizontally scan the field of view including the object. . Due to the horizontal scanning, the control circuit 10 sends pulses synchronized with the horizontal scanning to the pulse motor 8, so that the condensing mirror 2 moves in steps with the position _L1 corresponding to the _L1 as the forward movement start position. Start. and,
Until the sum of the number of pulses corresponding to the _l1 and the number of pulses sent from the motor 5 via the counter 9 becomes equal to the number of pulses corresponding to the _L2 , that is, the condenser mirror 2 The condensing mirror 2 moves in steps until it reaches the return movement start position _l2 . During this time, the infrared image signal obtained from the infrared detector 4 is differentiated by the differentiating circuit 13 via the amplifier 12. The differential signal is passed through the diode 14 and
The signal is sent via the AD converter 15 to the first latch circuit 17 and comparison circuit 18 of the maximum value detection circuit 16. The latch circuit stores the previous maximum value, and the comparison circuit compares the maximum value with the current data. When the current data exceeds the maximum value, the comparison circuit 18 issues a store signal and stores the current data in the first latch circuit 17 as the maximum value. The store signal is also sent to the second latch circuit 19, so that the second latch circuit 19 has the number of horizontal scans (the number of step movements) from the start of the forward scan to the number of pulses corresponding to the _l1 position. ) The current count value of the up-down counter 9 is stored. Therefore, the condenser mirror 2 changes from l ₁ to l ₂
At the time when the movement is completed, the maximum value of the differential peak during that time is stored in the first latch circuit 16, and the maximum value of the differential peak during that time is stored in the second latch circuit 19 (i.e., the maximum value of the differential peak is stored in the second latch circuit 19. A count value C indicating the position of the condensing mirror 2 at the time when the object is in focus) is stored, and if the condensing mirror 2 is placed at the position of this count value, the condensing mirror 2 will be in focus.
In this embodiment, the return of the condensing mirror 2 is used to stop the condensing mirror 2 at the position of the count value C as described below. That is, when the control circuit 10 detects that the condenser mirror 2 has reached the position _l2 by moving a certain number of steps, it reverses the rotation direction of the pulse motor 8 and directs it from _l1 to _l2 . The inversion signal R is moved step by step for each horizontal scan.
is issued to put the counter 9 into the down mode and switch the switch 20 to the coincidence detector 23 side.
Therefore, the count value of the counter 9 is sequentially decremented, and when the count value returns to the C value, the coincidence signal A is generated from the coincidence detector 23. At this time,
The focusing mirror 2 is in a position where the focus is correct, and if the switch 11 is opened in response to the coincidence signal and the focusing mirror 2 is stopped at that position, focusing has been performed correctly. .

In the above embodiment, the condensing mirror was moved by a pulse motor, but a DC motor is used, and a value corresponding to the forward movement start position is supplied to the motor, and the condensing mirror is moved all at once to that position. And furthermore,
Feedback is applied so that the output from the volume controller connected to the DC motor is equal to the value corresponding to the return movement start position, and the value corresponding to the in-focus position detected and memorized during the return movement is applied. Alternatively, the light may be supplied to the DC motor at the same time, and the condenser mirror may be moved to a position where it can be focused more quickly.

According to the present invention, the sweep range of the means for sweepingly changing the focal length of the optical system is limited from a fixed range fixed in advance to a range in front and behind the object depending on the object to be measured. Since it is only necessary to move the optical mirror within the limited and extremely narrow range, focusing can be performed at extremely high speed. In addition, since the limited range rarely includes objects other than the target object, objects other than the target object will not be in focus, and the target object will be accurately focused. matches.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining a scanning optical system, and FIG. 2 shows an embodiment of the present invention. 1... Scanning mirror, 2... Concentrating mirror, 4... Infrared detector, 5... Motor, 8... Pulse motor, 9...
...Up-down counter, 10...Control circuit, 1
3...Differential circuit, 16...Maximum value detection circuit, 17
...First latch circuit, 18... Comparison circuit, 19...
...Second latch circuit, 21...Third latch circuit, 2
2... Fourth latch circuit, 23... Coincidence detection circuit.

Claims (1)

[Scope of utility model registration request] an optical system for forming an image spot of an infrared detector on a subject; a sweeping means for sweepingly changing the focal length of the optical system; a scanning means for scanning the image spot on the subject; a differentiating means for obtaining a differential signal of the signal obtained by the differential signal, a memory means for storing a signal corresponding to the focal length of the optical system when the differential signal shows a maximum value, and a memory means based on the signal stored in the memory means. In the apparatus, the sweep range of the sweep means is arbitrarily set according to the object to be focused. A focusing device in a temperature measuring device, characterized in that it is made to obtain.