JPH05238773A - Phosphate-based glass filter and its production and image pick-up device - Google Patents

Abstract

PURPOSE:To provide a phosphate-based glass filter excellent in moisture resistance and optical characteristics and to provide a producing method and an image pick-up device. CONSTITUTION:The phosphate-based glass filter is constituted so that the weight component ratio of a phosphate compound in the surface of a phosphate-based glass plate is less than in the inner part. In the producing method, the phosphate- based glass plate is dipped in an acid solution having a prescribed conc. and temp. for a prescribed time. The image pick-up device is constituted by arranging successively an image pick-up lens, an optical filter absorbing selectively the light of near infrared wave length among rays transmitted through the image pick-up lens from an object to be mage-picked up and an imaging device such as e.g. CCD and the optical filter is formed from the phosphate-based glass pane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phosphate glass filter, a method for manufacturing the same, and an image pickup apparatus using the phosphate glass filter.

[0002]

2. Description of the Related Art For example, as a color sensitivity correcting optical element of an image pickup device of a video camera or an electronic still camera, a phosphate glass to which copper, iron or the like is added has been widely used (for example, Japanese Patent Publication No. 60). -49142,59-15102). However, this phosphate glass is inferior in moisture resistance, and there is a drawback that the so-called “burning” phenomenon occurs in which the surface layer is deteriorated by the action of moisture in the air, and the optical performance cannot be maintained for a long time. It was As a countermeasure against this, in order to improve the moisture resistance without deteriorating the optical performance, after applying a coating treatment to the optical surface of the phosphate-based glass, a hard optical element with excellent moisture resistance such as optical glass or crystal is used. Adhere to protect phosphate glass,
Further, there is a method of coating the surface of a phosphate glass with a dielectric protective film such as MgF ₂ (Japanese Patent Laid-Open No. 3-37142).

[0003]

However, in the prior art, the method of adhering and protecting a crystal or the like differs depending on the glass composition, but if a humidity resistance test is conducted under the conditions of a temperature of 60 ° C. and a humidity of 90%, it is at best. It has been clarified that the optical performance is impaired due to deterioration or peeling of the adhesive layer in about 300 hours. Also, by similarly adhering and protecting a glass having a protective film of a dielectric material with a crystal or the like, it is possible to improve the moisture resistance, but it requires a vacuum vapor deposition process, resulting in a high cost. was there.

The present invention has been made to solve these problems, and provides a phosphate glass filter having excellent moisture resistance and excellent optical characteristics, and at the same time, providing such a phosphate glass filter. It is an object of the present invention to provide a method for manufacturing the same and further to provide an imaging device using this phosphate glass filter.

[0005]

In order to achieve the object of the present invention, the phosphate glass filter of the first invention comprises:
In a phosphate glass filter composed of a phosphate glass plate, it is characterized in that the weight component ratio of the phosphate compound in the surface layer of the phosphate glass plate is smaller than that in the inside. ..

The method of manufacturing a phosphate glass filter according to the second aspect of the present invention comprises immersing a phosphate glass plate in an acid solution having a predetermined concentration and temperature for a predetermined time,
It is characterized by eluting the phosphate compound of the surface layer contained in the phosphate glass plate into the acid solution.

Further, the image pickup device of the third invention comprises an image pickup lens, an optical filter which selectively absorbs light of a predetermined wavelength out of the light from the image pickup object which has passed through the image pickup lens, and the optical filter thereof. The charge generated by the incidence of the light passing through, the image pickup device for accumulating and transferring, and the image pickup device sequentially arranged on the optical axis, the optical filter is composed of a phosphate glass plate, It is characterized in that the weight component ratio of the phosphate compound in the surface layer of the phosphate glass plate is smaller than that in the inside.

[0008]

In the phosphate glass filter of the first invention, the weight ratio of the phosphoric acid compound, which is the causative agent of burns, is smaller in the surface layer of the phosphate glass plate than in the inside. , The reaction of burns is suppressed and the surface of the glass plate is stabilized.

In the method for producing a phosphate glass filter according to the second aspect of the present invention, the phosphate glass plate is immersed in an acid solution having a predetermined concentration and temperature for a predetermined time so that the surface of the glass plate is removed. And the phosphate compound in the surface layer is eluted,
In the surface layer, the weight component ratio of the phosphoric acid compound is smaller than that in the inside.

Further, in the image pickup device according to the third aspect of the present invention, the surface layer of the phosphate glass used as the optical filter suppresses the burn reaction and stabilizes the surface of the glass plate. Therefore, the moisture resistance is excellent, and the optical performance can be maintained for a long time.

[0011]

1 is a schematic sectional view showing an embodiment of the first invention. The phosphate glass filter of this example is
It is composed of the phosphate glass plate 1, and the surface layer thereof has a small weight component ratio of the phosphoric acid compound contained in the phosphate glass. As described above, as the phosphoric acid compound 2, which is the main causative agent of burns, such as phosphate, decreases in the surface layer of the phosphate glass plate 1, the glass surface is more stabilized and burns can be suppressed.

FIG. 2 is a schematic sectional view showing another embodiment of the first invention. In this embodiment, the above-mentioned first
The optical surface 1a of the phosphate glass plate 1 according to the embodiment of the present invention,
A crystal plate 4 is bonded to each of 1b via an adhesive 3. That is, the surface is protected by sandwiching the phosphate glass plate 1 between the two crystal plates 4.

A method of manufacturing the embodiment shown in FIGS. 1 and 2 having the above structure, that is, an embodiment of the second invention will be described below. First, 0.5N kept at 40 ° C
-A 10 mm square and 1 mm thick phosphate glass was immersed in a phosphoric acid solution, and acid-treated for 10 hours while stirring.

The acid used for this acid treatment may be a solution of nitric acid, hydrochloric acid, acetic acid or the like other than the above-mentioned phosphoric acid. Further, when this acid treatment is carried out at a high concentration, at a high temperature for a short time, the surface of the glass is roughened and latent scratches are generated, and the spectral characteristics are changed, resulting in deterioration of optical characteristics. Therefore, it is desirable that this acid treatment is performed for 20 hours in an atmosphere having a concentration of 5 N or less and a temperature of 80 ° C. or less.

By acid-treating the phosphate glass in this manner, the phosphoric acid compound, which is the causative agent of burns, is forcibly eluted from the surface layer of the phosphate glass. That is,
The phosphate-based glass surface layer is stabilized by eluting the one that easily dissolves first, so that the surface-layer is rich in the one that hardly dissolves, and as a result, the phosphate-based glass surface is stabilized.

The acid-treated phosphate-based glass had no change in the spectral transmittance characteristics or the surface condition by visual observation, but the Auger electron spectroscopic analysis (AES) showed that the energy intensity of phosphorus in the surface layer was high. It was confirmed that the phosphoric acid compound was reduced in the surface layer because the amount was smaller than that before the acid treatment.

With respect to the example shown in FIG. 1 manufactured by the method described above and the phosphate glass not subjected to the acid treatment by the method of the present invention (hereinafter referred to as Comparative Example [1]), 60 ° C.-90% A humidity resistance test was performed under the conditions of. As a result, it was confirmed that, in the example shown in FIG. 1, white burns were visually observed after 300 hours, whereas in Comparative Example [1], white burns were observed after 150 hours.

Further, a quartz plate is adhered to each of the optical surfaces of the embodiment shown in FIG. 2 manufactured by the method of the present invention and the phosphate-based glass plate not subjected to the acid treatment by the method of the present invention through an adhesive agent. With respect to the constitution (hereinafter, referred to as Comparative Example [2]), the moisture resistance test was similarly conducted under the condition of 60 ° C.-90%. As a result, it was confirmed that in the example shown in FIG. 2, abnormalities in optical characteristics occurred after 1000 hours, whereas in Comparative Example [2], abnormalities such as peeling occurred after 150 hours.

From these experimental results, it is clear that the structure of the phosphate glass filter of the present invention improves the moisture resistance, and therefore, the optical characteristics are further improved. It was

The construction of the phosphate glass filter is not limited to that described above, but in addition to this, for example, the optical surface of the phosphate glass of the embodiment shown in FIG. 1 is coated with a dielectric protective film. Needless to say, the moisture resistance is further improved in this case.

FIG. 3 is a block diagram for explaining an embodiment of the third invention. Hereinafter, description will be given with reference to the drawings. This embodiment is used in a video camera, an electronic still camera or the like as an optical device for color sensitivity correction.

The image pickup lens 5 receives light from the object to be imaged,
An optical filter F is disposed between the image pickup lens 5 and the image pickup element I, which is a lens for forming an image on the light receiving surface of the image pickup element I.

The optical filter F has a structure in which two crystal plates 4 are bonded to each other with the phosphate glass plate 1 interposed therebetween. Further, the phosphate glass plate 1 is
The weight ratio of the phosphate compound in the surface layer is smaller than that in the inside. This optical filter F is also called color correction glass, and since the wavelength sensitivity of the solid-state image sensor I extends not only to visible light but also to the near infrared region, the phosphate glass plate 1 of this optical filter F It can absorb unnecessary near infrared rays and cut them.

The light passing through the optical filter F enters the image pickup element I. The image pickup device I has a cover glass 6, a color separation filter 7 and a CCD 8 along its optical axis.
Are sequentially arranged. Therefore, the incident light, that is, the light after the near infrared rays are removed, is separated by the color separation filter 7 into predetermined wavelengths, and then enters the CCD 8. Then, the CCD 8 sequentially accumulates the charges generated by this light incidence, outputs the accumulated charges to the outside at a predetermined time interval, and the output is displayed on a display device (not shown) such as a CRT. It is provided as information.

In the embodiment shown in FIG. 3, the optical filter F has a structure in which one crystal plate 4 is adhered to each side of the phosphate glass plate 1, and the crystal plate 4 is composed of two crystal plates. The number of sheets may be about seven to seven, and in this case, the same effect as described above can be obtained.

FIG. 4 shows the spectral transmittance characteristics of the phosphate glass filters used in the examples of the present invention. As is clear from this figure, by using the phosphate glass filter, it is clear that light in the wavelength range of 750 nm to 1000 nm is absorbed without being transmitted.

[0027]

As described above, according to the first aspect of the present invention, in the surface layer of the phosphate glass plate, the weight component ratio of the phosphoric acid compound which is the causative agent of burns is smaller than that in the inside. Since the constitution is adopted, the reaction of burns is suppressed and the surface of the glass plate is stabilized. As a result, it is possible to provide a phosphate glass filter having improved moisture resistance and excellent optical characteristics.

According to the second aspect of the invention, the phosphate glass plate is immersed in the acid solution having a predetermined concentration and temperature for a predetermined time. And the time can be easily controlled. As a result, the manufacturing process can be simplified and the cost can be reduced.

Further, according to the third aspect of the invention, since the phosphate glass type glass filter according to the first aspect of the invention is used as the optical filter, the image pickup device has excellent optical characteristics and is durable. It will improve the sex.
For example, when used in a video camera or the like, image quality and sensitivity are improved.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the first invention.

FIG. 2 is a schematic sectional view showing another embodiment of the first invention.

FIG. 3 is a configuration diagram showing an embodiment of a third invention.

FIG. 4 is a diagram illustrating a third invention.

[Explanation of symbols]

 1 ... ・ Phosphate glass plate 1a, 1b ... ・ Optical surface 2 ... ・ Phosphate compound 3 ...・ ・ ・ CCD F ・ ・ ・ ・ Optical filter I ・ ・ ・ ・ ・ ・ Imaging element

Claims (3)

[Claims] 1. A phosphate glass filter composed of a phosphate glass plate, wherein the weight component ratio of the phosphate compound in the surface layer of the phosphate glass plate is smaller than that in the inside. Characteristic phosphate glass filter. 2. A phosphate glass plate is immersed in an acid solution having a predetermined concentration and temperature for a predetermined time to remove the phosphate compound of the surface layer contained in the phosphate glass plate from the acid solution. A method for producing a phosphate-based glass filter that is eluted into a glass. 3. An imaging lens, an optical filter that selectively absorbs light of a predetermined wavelength of light from an object to be imaged that has passed through the imaging lens, and light that has passed through the optical filter. In an image pickup device in which an image pickup element that accumulates and transfers electric charges is sequentially arranged on the optical axis,
The optical filter is composed of a phosphate glass plate, characterized in that the weight component ratio of the phosphate compound of the surface layer of the phosphate glass plate is formed smaller than the inside Imaging device.