JPH07244318A - Image acquiring device - Google Patents

Abstract

PURPOSE:To obtain an image having the same brightness in accordance with a difference in illumination between sunshine and shade, in on-satellite equipment by using a light source high in monochromaticity and arranging a filter having a passage band corresponding to the wavelength of the light source in front of an image pickup means. CONSTITUTION:An illuminating means 1 built in a laser diode having a monochromatic spectrum of 660nm and an interference optical filter 3 having a passage band for a wavelength of 660nm is installed in front of the image pickup means 2. When sunlight is made incident, the light source of the illuminating means 1 is turned off and the reflected light from an object 4 of the sunlight is made incident on the image pickup means 2. Most of a wide spectrum of sunlight is intercepted by the filter 3 and only components centering on a wavelength of 660nm are made incident on the image pickup means 2. When a satellite is moved to the back of the earth and the sunlight is not made incident, the light source of the illuminating means 1 is turned on and the reflected light from the object 4 of a lighting source is made incident on the image pickup means 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image acquisition device, and more particularly to an image acquisition device used in two environments in which the illuminance of the surface of an image acquisition object is extremely different. Today, various systems using artificial satellites orbiting the earth are in operation and are newly planned, and there is an increasing demand for improving the performance of image acquisition devices on artificial satellites. In particular,
Since the illuminance on the surface of the image acquisition target is extremely different between when the artificial satellite is illuminated by sunlight and when it is not illuminated, an image acquisition device that acquires an image of constant brightness is required. Has been done. Therefore, it is necessary to equivalently reduce the difference in surface illuminance of the image acquisition target.

[0002]

2. Description of the Related Art Conventionally, in a general image acquisition apparatus, filters having different light transmittances are used in order to acquire an image having a constant brightness in response to a change in illuminance environment of external light such as sunlight. A method of adjusting the amount of light transmission by changing the aperture of the diaphragm (also called iris), or a method of mechanically or electronically controlling the shutter speed. , A method of adjusting the exposure amount has been adopted. FIG. 6 shows a conventional example using a light bulb as an auxiliary light source.

However, in the case of satellite-equipped equipment, so-called resources such as weight, space, and electric power are severely limited, and the filter exchange mechanism and diaphragm adjustment described above are performed in an environment of high vacuum and large temperature difference such as outer space. It is very difficult to make the mechanism function reliably. Furthermore, the illuminance due to direct sunlight reaches 100,000 lux or more during sunshine, whereas lighting means is required during shade.
Due to the above-mentioned resource limitation and the like, the illuminance obtained by the illuminating means is limited to about 10 to 100 lux, and the illuminance difference between sunshine and shade is 1000 to 10000 times.

On the other hand, generally, the control range of the electronic shutter is 1/60 to 1/10000 seconds, and the adjustment range is about 200 times,
It is relatively small for the subject of the present invention.

[0005]

Therefore, if the shutter speed is only electronically adjusted, the difference in illuminance between the sunshine and the shade cannot be dealt with, and an image with a constant brightness cannot be obtained. There was a drawback to say.

The present invention is mainly applied to satellite-equipped equipment in response to an illuminance difference of up to 10000 times in the sunshine and in the shade without mechanical operations such as filter replacement and diaphragm adjustment. The object is to configure a device for acquiring a brightness image.

[0007]

FIG. 1 is a diagram for explaining the principle of the present invention. In the figure, reference numeral 1 denotes an illumination means that emits highly monochromatic light by incorporating a light emitting diode (LED) or a laser diode (LD), and provides illumination light in the shade.
Reference numeral 2 is an image pickup means, which converts an image of an image pickup object into an electric signal (also referred to as a video signal), and 3 is an optical filter,
A light source having a predetermined wavelength is selected and passed through. Reference numeral 4 is a tangible object such as a satellite-mounted device, which is an object to be imaged.

[0008]

In the image acquisition device according to the present invention, first, a light source having high monochromaticity is used as the illumination means, and secondly,
By disposing a filter having an extremely steep characteristic having a pass band corresponding to the light source wavelength on the front surface of the image pickup means, a specific effect can be obtained based on the operation described below. That is, as for the illuminating means, so-called light bulbs such as halogen lamps and xenon lamps used in conventional satellite-mounted devices have a wide emission spectrum corresponding to the filament temperature, like sunlight, whereas, for example, Light emitting diodes (LEDs) and laser diodes (semiconductor lasers) have high monochromaticity, have an extremely narrow emission spectrum as shown in FIG. 4, and the emission energy is concentrated in a specific wavelength band.

On the other hand, as for the filter, for example, the interference type filter can be configured as a bandpass filter that allows only a specific wavelength band to pass by controlling the film thickness of the vapor deposition film deposited on the glass surface. As shown in FIG. 5, the cutoff characteristic can be set very sharply. By matching the pass band of this filter with the light source wavelength of the illumination means, the total transmittance of the light from the illumination means
For example, while maintaining a high value of about 70%, the transmittance of sunlight having a wide spectrum distribution as shown in FIG. 4 is, for example, 1%.
It can be limited to a degree or less. As a result, the relative illuminance on the surface of the imaging means with respect to the sunlight during sunshine is, for example, 100000 × 1% = 1000 (lux). On the other hand, the relative illuminance to the lighting means in the shade is
Assuming that the brightness of the light source is equivalent to 100 lux, 100 × 70% = 70 (lux), which makes it possible to reduce the illuminance ratio during sunshine and shade to 15 or less. The combined use of and makes it possible to make the brightness of the acquired image substantially equal.

[0010]

FIG. 2 is a block diagram of the first embodiment of the present invention.
In the figure, 1 is an illuminating means by a laser diode having a monochromatic spectrum of 660 nm, 2 is an image pickup means having a CCD image pickup device, and 3 is 660 nm installed in front of the image pickup means.
The interference type optical filter having a bandwidth of 10 nm and a bandwidth of 10 nm, 4 is a tangible object such as a device mounted on a satellite and is an object to be imaged, 5 is a control means, and the image pickup means outputs an optimum image signal. It adjusts the related means so that

During sunlight, when sunlight is incident, the light source of the illumination means 2 is in the OFF state, and the object 4 of sunlight is
Although the reflected light from B is incident on the image pickup unit 2, most of the broad spectrum of sunlight is blocked by the interference filter 3, and only about 0.1% of the component centered at the wavelength of 660 nm is captured by the image pickup unit. Enter into. Next, in the shade, that is, when the satellite goes around the back side of the earth and sunlight does not enter, the light source of the illumination means 2 is turned on, and the reflected light from the target object 4 of the illumination light source enters the imaging means 2. Due to the characteristics of the illumination light source, most of this incident light has its light energy at the center of a wavelength of 660 nm, and, for example, about 70% thereof passes through the interference filter 3 and enters the imaging means.

A block diagram of the second embodiment of the present invention is shown in FIG. In the figure, 1A and 1B are illumination means by laser diodes each having a monochromatic spectrum, and the emission center wavelength of 1B does not match the emission center wavelength of 1A, but their emission wavelength bands overlap. Others are the same as those in the configuration diagram of the first embodiment. Since the bandwidth of the filter can be slightly widened as compared with the case of the configuration diagram of the first embodiment,
The passage loss of the filter can be reduced as compared with the case of the first embodiment configuration diagram, and the reliability of the illumination light source can be increased. Further, the illumination direction can be divided into a plurality of directions, which may facilitate observation of the shape of the object.

In the above-mentioned embodiment, an example in which an interference filter using a multilayer film is used as a filter has been described, but the same effect can be expected by using a diffraction grating. Also,
It is also possible to provide a simpler device using colored glass. Further, although the illumination light source has been described as being used in the shade, it can be used also in the sunlight to determine whether the shape of the object can be easily determined.

As described above, according to the present invention, it is possible to reduce the difference in the illuminance ratio during sunshine and in the shade regardless of the adjusting mechanism involving mechanical movement such as filter replacement and diaphragm adjustment. By using the electronic shutter together with the adjustment of the exposure time, it becomes possible to match the equivalent light energies.

[0015]

As described above, according to the present invention, a filter is used under two environments in which the brightness (illuminance) of external illumination is extremely different, such as an artificial satellite during sunshine and an artificial satellite during shade. It is possible to obtain an image with a constant brightness without performing adjustments involving mechanical operations such as replacement of the lens and adjustment of the diaphragm.

In addition, it is effective for protecting the device because it reduces the input light to the image pickup device.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a configuration diagram of a first embodiment of the present invention.

FIG. 3 is a configuration diagram of a second embodiment of the present invention.

FIG. 4 is an example of an emission spectrum of sunlight and an LED.

FIG. 5 is an example of a pass characteristic of an interference filter.

FIG. 6 is a conventional configuration example.

[Explanation of symbols]

 1, 1A, 1B Illuminating means 2 Imaging means 3 Optical filter 4 Imaging target 5 Control means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location G03B 15/02 F H04N 5/225 Z

Claims (3)

[Claims] 1. An image acquisition device having illumination means and imaging means, wherein the illumination light emitted by the illumination means (1) has a light spectrum with high monochromaticity, and the imaging means (2) is included in the illumination light. An image acquisition device characterized in that a filter (3) having a characteristic of selectively passing an optical spectrum to be transmitted is arranged in front of the image pickup means (2). 2. The image acquisition device according to claim 1, wherein a light emitting diode or a laser diode is used as a light source of the illumination means, and an interference type filter is used as a filter. 3. The image acquisition device according to claim 2, wherein a plurality of light emitting diodes or laser dies each having a different central wavelength of light emission wavelength are used.