JP2745962B2 - Infrared imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared imaging apparatus, and more particularly to a method for correcting a change in focal length of a lens due to temperature.

[0002]

2. Description of the Related Art As shown in FIG. 3, a conventional scanning infrared imaging apparatus has a telephoto lens 17, a scanner 18, a condenser lens 6, and a detector 8. The scanner 18 generally scans a parallel beam 19, but when the beam is not parallel, shading, vignetting, and a decrease in MTF are caused.

On the other hand, the focal length of the condenser lens 6 changes depending on the ambient temperature, so that the beam is not parallel. Therefore, conventionally, in order to correct this, as shown in FIG. 4, the ambient temperature is measured by the temperature sensor 21, and the controller 12 preliminarily compares the temperature measured by using the motor 7 and the position sensor 20. In this method, the lens is moved and controlled to a predetermined position.

[0004]

In this conventional infrared imaging apparatus, it is necessary to acquire and store in advance the data on the positional relationship between the temperature and the optimum lens, and to obtain sufficient correction accuracy. However, there is a problem in that the device becomes complicated and expensive, such as the need for a position sensor with high detection accuracy.

An object of the present invention is to automatically correct a change in the focal length of a condenser lens due to a change in an ambient temperature.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method for reflecting external light by a horizontal scanner and a vertical scanner, condensing the extraneous light on a detector by a condenser lens, and detecting an electric signal by the detector. In a device that converts the signal to an amplifier and sends it to the next stage, means for detecting the sharpness of the signal component imaging the detector itself existing in the dead section, and moving the condenser lens back and forth And a position control means for controlling the position of the condenser lens so that the sharpness is maximized.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention. In FIG. 1, extraneous light 1 is reflected by a horizontal scanner 3 and a vertical scanner 5, and is collected on a detector 8 by a condenser lens 6. Then, it is converted into an electric signal by the detector 8,
After being amplified by the amplifier 9, it is sent to the next stage 23.

FIG. 2 shows an example of an output waveform of the amplifier 9. The active section 13 is a signal corresponding to the external light 1.

Next, when the horizontal scanner 3 comes to the position 4, the light beam 2 and the reflection surface of the horizontal scanner 4 are orthogonal to each other,
Travels through the same optical path and returns to the detector 8. That is, at this time, the detector 8 captures an image of itself. The signal 15 in this section is the narcissus section 1 in FIG.
6. The signal 15 is transmitted from the horizontal scanner 4 to the external light 1.
Are within the dead zone 14 where scanning is not performed, and therefore can be obtained without affecting normal imaging. The signal 15 is focused on the detector 8 when the light beam 2 is a parallel beam, and has the sharpest waveform at this time. Since the sharpness (sharpness) of the signal is considered to be proportional to the amount of the high-frequency component included in the signal, in this embodiment, the narcissus section 16 is gated, and the Is being extracted. The output signal of the band-pass filter 11 is input to a controller 12, which measures this level, moves the motor 7 so that the level becomes maximum, and controls the lens position. As described above, the condenser lens 6 is always focused on the detector 8 with respect to a change in the ambient temperature, and the light beam 2 can be made into a parallel beam.

[0011]

As described above, according to the present invention, the apparatus is provided with means for detecting the sharpness of the signal of the detector itself and moving the condenser lens so as to maximize the sharpness. It is possible to obtain an effect that the lens position can always be adjusted to an optimum position with respect to a change in the ambient temperature without making it complicated and without performing a special initial adjustment.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a diagram showing an example of an output waveform of an amplifier used in one embodiment of the present invention.

FIG. 3 is a block diagram showing a conventional scanning infrared imaging device.

FIG. 4 is a block diagram showing a correction method of a conventional scanning infrared imaging device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 External light 2 Light beam 3, 4 Horizontal scanner 5 Vertical scanner 6 Condensing lens 7 Motor 8 Detector 9 Amplifier 10 Gate 11 Bandpass filter 12 Controller 13 Active section 14 Dead section 15 Signal 16 Narcissus section 23 Next stage

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI G02B 26/10 102 H04N 5/232 A H04N 5/232 G02B 7/11 H

Claims (2)

(57) [Claims] An external light is reflected by a horizontal scanner and a vertical scanner, condensed on a detector by a condenser lens, converted into an electric signal by the detector, amplified by an amplifier, and sent to the next stage. Means for detecting the sharpness of the signal component imaging the detector itself present in the dead zone, means for moving the condenser lens back and forth, and focusing so that the sharpness is maximized. An infrared imaging apparatus comprising: a position control unit that controls a position of a lens. 2. A bandpass filter is used as a means for detecting the sharpness of a signal component imaging the detector itself existing in the dead zone, a motor is used as a means for moving the condenser lens back and forth, and a sharp The infrared imaging apparatus according to claim 1, wherein a controller is used as a position control means for controlling the position of the condenser lens so that the degree is maximized.