JPS6023801A - Image pickup device - Google Patents

Abstract

PURPOSE:To decrease reflected light and to improve the sensitivity of an image pickup device by using a prescribed filter for the face plate of an image pickup tube or the cover glass of the package case of a solid-state image pickup element. CONSTITUTION:A solid-state image pickup element 8 and a separation filter 10 for three colors facing the photodetecting part of said element are built in a package case 1. The element 8 is connected to internal lead terminals 13, 14 via lead wires 11, 12 and the terminals 13, 14 are connected to external lead terminals 15, 16. A face plate (cover glass) 17 is further provided atop the case 1. A filter 18 having an IR cut characteristic or optical low-band filter characteristic is used for the face plate 17, by which the need for the glass plate used thus far is eliminated and the reflection of light is decreased. It is also possible to use a filter formed by adhering an optical low-band filter 10 and an IR cut filter 21 by means of an adhesive agent 20 as the face plate 17.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an imaging device, and more particularly to an imaging device in which a face plate or a cover glass of a package case has other functions.

Conventional technology Conventionally, MOS (metal oxide) was used as an image sensor.
Semiconductor), C0D (Char, The Coupled
In a solid-state color camera using a semiconductor (solid-state image sensor) such as a device), BBD (packet pre-gate device), or a color camera using an image pickup tube, an optical device placed in front of the solid-state image sensor or image pickup tube The system is
It is composed of a color separation filter, an infrared cut filter, a phase filter (optical low-pass filter) that uses crystal as a phase filter, and an optical lens. Furthermore, cameras using either an image pickup tube or a solid-state image pickup device are provided with a glass plate for the purpose of protecting the device. This glass plate is called a face plate in an image pickup tube, and is a cover glass of a package case in a solid-state image sensor, but for convenience of explanation, these will be collectively referred to as the face plate 1. The arrangement of this face plate and each element constituting the optical system described above,
Although the order of combination is arbitrary, the face plate, R-cut filter, and optical low-pass filter are often arranged as independent components. On the other hand, color separation filters are used in single-tube, single-plate, two-tube, or two-plate color cameras, and are often aligned with the internal imaging area and fixed with adhesive. many. Each of these components is generally constructed using a glass substrate or a crystal substrate.

FIG. 1 shows a perspective view of an example of a conventional solid-state image sensor. In the figure, a face plate (cover glass) 2b is provided on the top surface of the package case 1, and light from a subject (not shown) is made to pass through the face plate 2 and enter the package case 2. After being photoelectrically converted by an internal solid-state image sensor, the signal is output as a signal from external lead terminals 31 to 37. FIG. 2 shows the configuration of an example of an optical system of a color camera using a conventional solid-state image sensor. In the figure, the light from the subject is transmitted through the optical lens system 4.
The entire light is incident on the optical low-pass filter 5 as light A,
In order to prevent moire from occurring due to unnecessarily high spatial frequency components being incident on the color separation filter 7, which will be described later, the high spatial frequency components are removed to create blur. Light B emitted from the optical low-pass filter 5 enters an infrared (engineering R) cut filter 6 to reduce the wavelength component of the infrared light and is converted into light C. The light passes through and enters the color separation filter 7 inside the package case 1. The light separated by color and extracted by the color separation filter 7 is made incident on the light receiving section of the solid-state image sensor 8, where it is photoelectrically converted.

In the conventional optical system shown in Fig. 2, transmitted light A, B, O
It is well known that when incident on the optical low-pass filter 5, infrared cut filter 6, and face plate 7, reflected lights A', B', and σ occur due to the difference in refractive index between air and crystal or glass. This is the general rule. It is well known that in general optical glass, the reflectance is 43% (about 4%) on one side and about 8% on both sides. For example, if we focus only on this reflected light and assume that there is no absorption by each component, then when light A passes through the optical low-pass filter 5, it becomes 92% transmitted light B, and further infrared cut. After passing through the filter 6, 84.6% of the transmitted light C becomes
Furthermore, when the light passes through the face plate 2, the transmitted light becomes 77.8%. Therefore, the customized wavelength versus transmittance of the transmitted lights B, 0, and D is as shown in FIG.

As described above, in the conventional optical system shown in FIG. 2, the light intensity of the reflected light and transmitted light fluctuates greatly when each optical component passes through the light, reducing the light utilization rate. Therefore, conventionally, JF2 (magnesium fluoride) was used on the entrance surface of each optical component.
, ca'2. A method has been used in which a material such as calcium fluoride (calcium fluoride) is coated to provide a medium layer with a refractive index intermediate between that of air and glass. According to this method, the reflectance of each optical component can be improved to about 1 inch.

Problems to be Solved by the Invention However, the above-mentioned conventional method requires a vapor deposition process to coat M#F2 or ('aF2), resulting in high cost. Since it has slight spectral characteristics, it has problems such as changing the spectral q'!INote with respect to incident light having flat spectral characteristics.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an imaging device that solves the above problems by reducing the number of reflective surfaces due to the difference in refractive index between air and glass (or crystal).

Means for Solving the Problems The present invention is applied to a face plate of an image pickup tube or a cover glass of a package case of an all-in-one image pickup device.

Characteristics of infrared cut filters, optical low-pass filters, and/or custom-made color separation filters that separate and extract light of wavelengths of colors on the plate, or combinations of characteristics on any plate. Each of the embodiments will be described below with reference to the drawings from FIG. 4 onwards.

Embodiment FIG. 4 shows a sectional view of a first embodiment of the apparatus of the present invention. In the figure, inside the package case 1 is an image sensor 8, and an adhesive layer 9'f facing the light-receiving part is precisely aligned to each pixel and adhered to each pixel. Three color separation filters 10 are built in, respectively. Solid-state image sensor 8
is the internal lead terminal 1 via the lead wires 11 and 12.
3, 14, internal lead terminal 13,
14 is an external lead terminal 15 outside the package case 1
, 16 (corresponding to 31 to 37 in FIG. 1). Furthermore, on the top surface of the package case 1, there is a face plate (cover glass) 17 which is a main part of the present invention.
is provided.

Here, each embodiment of the face plate 17 is shown in FIG.
) l Shown in (B). FIG. 5(A) shows a first embodiment in which a filter 1B having infrared cut filter characteristics or optical low-pass filter characteristics is used as a face plate 1γ. This filter 18 is attached to the face plate 17.
If the filter 18 has a custom-made infrared cut filter, an optical low-pass filter is provided on the light incident side of the face plate 17 (filter 1B), and the filter 18 has optical low-pass filter characteristics. In this case, the infrared cut filter is offset from the light incident side Vcy with respect to the face plate 11 (filter 18).

This embodiment eliminates the need for the glass plate conventionally used as a face plate, and can prevent reflections of about 4 inches on one side and about 8 inches on both sides, which reduces the glare by about 4% compared to conventional imaging devices. Light reflection can be reduced (light transmittance increases by about 8%).

FIG. 5(B) shows the structure of a second embodiment of the face plate 17. In the figure, an optical low-pass filter 19 and an infrared cut filter 21 are each bonded to each other via an adhesive layer 20 made of optical adhesive. As an optical adhesive, in order to keep the reflectance as low as possible, the refractive index of glass is 1.
An adhesive with a refractive index as close as possible to 54 is used - for example Cemedine 1565 (trade name) is used.

Face plate 11 of rj'j configuration, not shown in FIG. 5(B)
When using the optical low-pass filter 1, it is possible to eliminate the need for the glass plate conventionally used as a face plate.
9 and the incident surface of the infrared cut filter 210 can be reduced by about 35% each (05% each on the adhesive layer 200 surface, a total of about 1 inch is reflected), and this allows light to pass through more easily than conventional devices. The rate can be improved by about 15 times.

Next, a second embodiment of the device of the present invention will be explained with reference to FIG. In FIG. 6, the same components as those in FIG. 4 are designated by the same reference numerals, and their explanations will be omitted. In FIG. 6, the height position 1d of the top surface of the three-color separation filter 10, the package case 1
The height positions of the face plate mounting step portions 1a and Ib are made to match. However, the stepped portion 1a,
lb has been coated with sealing adhesive and has already been coated with sealing adhesive.
Optical adhesive is applied to the upper surface of the three-color separation filter 10, which is mounted on the light-receiving part of the solid-state image sensor 8 in a closely positioned manner, and then the face plate 1' is attached.
7 from above on the stepped portions 1a, 1b and the three-color separation filter 10 and press-bond the face plate 1.
7, the package case 1 can be sealed.

For this reason, the increase in man-hours in the process is extremely small. In addition, in FIG. 6, 22 is an adhesive layer formed between the three-color separation filter 10 and the face plate 17, and 23a
, 23b is the stepped portion 1a', 1b and the face plate 17.
It shows the adhesive layer formed between the

According to this embodiment, when the first embodiment shown in FIG. 5(A) is used as the face plate 17, reflected light can be reduced by about 15% compared to the conventional device, When the second embodiment shown in FIG. 5(B) is used as the plate 11, reflected light can be reduced by about 22%. This is because reflection at the entrance surface of the three-color separation filter 100 can also be reduced compared to the first embodiment shown in FIG. 4.

Note that each of the above embodiments has been described as an example that can be applied to a single-panel type or a two-panel type color camera, or can also be applied to a three-panel type color camera.

For a 3-panel color camera, use a 3-color separation filter of 100
Instead, a monochromatic filter is used that selectively filters any of the three primary colors, and the optical low-pass filter 19 is not used. Therefore, in such a case, the face plate of the apparatus of the present invention should have an infrared cut filter function, or should have a structure as shown in FIG. 7(A).

FIG. 7(A) In the VC, an infrared cut filter 24 and the monochromatic filter 26 are bonded to each other via an adhesive layer 25 made of the optical adhesive. Since the monochromatic filter does not require precise alignment like the three-color separation filter 10, it can be handled separately from the image sensor.
A bonding machine other than the monochromatic filter 26 can be used as a face plate, and the reflectance can be reduced in the same way as shown in FIG. 5(A).

In addition, in a single-panel type or two-panel type color camera, as shown in FIG.
The part with the color separation filter 28 connected to it via t can also be used as a face plate. The above color separation filter 28 may be a three-color separation filter, or it may be a filter that forms the negative part of the filter group that forms it (however, in this case, a precise positioning process for the same-body image sensor is required). .

Application Examples Although each of the above embodiments has been described as being applied to a color camera using a solid-state image sensor, it goes without saying that the invention can also be applied to a color camera using an image pickup tube. Furthermore, although the three-color separation filter 10 has been described as being attached to the image sensor face plate with a straight line, it is also possible to use a type that is manufactured on the surface of the JJ image sensor.

EFFECTS As mentioned above, the present invention provides a faceplate or cover glass with the characteristics of -14% each of an infrared cut filter, an optical low pass filter, and a color separation filter or a custom assembly on the plate. Since the glass plate used as the face plate or cover glass in conventional equipment can be made completely unstable VC,
Not only can reflection on the glass plate surface be eliminated, but also reflected light on the incident surface of the various filters mentioned above, such as infrared cut filters, can be reduced, thus increasing the actual transmittance compared to conventional FI. As a result, the imaging device can be made highly sensitive, and the glass plate used as a face plate or cover glass can be made unnecessary, resulting in cost reduction, miniaturization and light forging of the device, etc. It has the following features.

[Brief explanation of drawings]

Figure 1 is a perspective view showing an example of a conventional solid-state image sensor;
The figure shows the schematic configuration of the optical system of color camera 2 using a conventional solid-state image sensor, and the state of light transmission and reflection σ).
The figure is a diagram showing an example of the transmittance versus wavelength characteristic of the transmitted light of the optical system shown in Figure 2, Figures 4 and 6 are cross-sectional views showing each embodiment of the device of the present invention, and Figure 5 (A). , (B) and the first
Figures (A) and (B) are diagrams showing the configuration of each embodiment of a face plate that constitutes a main part of the device of the present invention. 1...Package case, 2.17...Ka (-crow (facebrae)), '31~37...External 1
．． I-)" terminal, 5, 1B...' optical low-pass filter, 6, 21. 24... infrared (engineering R) cut filter, 7.28.
...Color separation (color separation) filter, 8...Solid-state image sensor, 10...Three color separation filter, 15, 16...External lead terminals. 18... Infrared cut filter (or optical low-pass filter), 20, 22, 23a, 23b, 25
, 27''-adhesive layer, 26...monochrome filter.

Claims (2)

[Claims] (1) The face plate of the image pickup tube The cover glass of the package case of the X-ray solid-state image sensor is equipped with an infrared cut filter, an optical low-pass filter, and a filter that separates and captures the light of the wavelength of the color on the dish plate. An imaging device characterized by being configured with a custom-made combination of - of the characteristics of a color separation filter to be produced or a custom-made combination on an arbitrary plate. (2) The imaging device according to claim 1, wherein a three-color separation filter is bonded to the face plate or the cover glass using an optical adhesive having a refractive index substantially equal to the refractive index of the glass.