JP2000040813A - Image sensing apparatus and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable easy positioning with high precision, in position relations between an image sensing element and an imagery optical element and between the image sensing element and a phase type low-pass filter. SOLUTION: In an image sensing apparatus constituted of an image sensing element 3 an imagery optical element 6 and an optical low-pass filter 10 arranged between the image sensing element 3 and the imagery optical element 6 the imagery optical element 6 and the optical low-pass filter 10 are held with a specified position relation by a holder 5. The holder 5 is so fixed on a package that position relation of a reference surface of the imagery optical element 6 to an image sensing surface of the imaging element 3 satisfies a specified relation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup device, in particular, an image pickup device for converting input light into an electric signal by photoelectric conversion, and an image forming device for forming an object on an image pickup surface of the image pickup device. The present invention relates to an imaging device including an imaging optical element to be formed, an optical low-pass filter provided between the imaging device and the imaging optical device, and a method of manufacturing the same.

[0002]

2. Description of the Related Art An imaging apparatus generally includes a solid-state imaging device housed in a package and an imaging optical element (imaging lens) for imaging a subject on an imaging surface of the solid-state imaging device. In many cases, an objective low-pass filter is provided.
This is because a solid-state image sensor such as a CCD solid-state image sensor temporally and spatially samples an image formed on an imaging surface and photoelectrically converts the image, thereby generating a false signal due to sampling. Is necessary to suppress the false signal.

[0003] A phase-type low-pass filter and a birefringence-type low-pass filter are mainly used as an optical low-pass filter. Comparing the two, the phase-type low-pass filter can reduce the manufacturing cost and reduce the cost. Can be said to be suitable for a small-sized imaging device with extremely strong.

[0004]

By the way, in an image pickup apparatus using a phase-type low-pass filter as an optical low-pass filter, it is necessary to improve the positioning accuracy of the phase-type low-pass filter with respect to the imaging surface of the image sensor. was there. This is because the phase-type low-pass filter separates light rays by a diffraction grating, so that if the positional relationship of the filter with respect to the imaging surface is incorrect, the light beam incident on the imaging surface is different from the pixel that should originally be incident (adjacent pixel)
This causes a problem that the light is incident on the device and appears as noise.

[0005] Further, there is a strong demand for miniaturization, particularly thinning of the imaging device, but in order to meet the demand for thinning, the distance between the imaging lens (imaging optical element) and the imaging device is inevitably increased. It is necessary to make the lens narrow, and as a result, a lens having a small depth of focus must be used. However, as the imaging lens having such a shallow depth of focus is used, it is necessary to increase the positioning accuracy of the imaging lens with respect to the imaging surface of the imaging device.

As described above, in an image pickup apparatus, particularly a small-sized image pickup apparatus, it is necessary to increase the positioning accuracy of an imaging lens (imaging optical element) and an optical low-pass filter, particularly a phase-type low-pass filter, with respect to the image pickup element. However, obtaining the required positioning accuracy has not been easy in the past.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and has an image pickup device including an image pickup device, an image forming optical device, and an optical low-pass filter provided between the image pickup device and the image forming optical device. It is an object of the present invention to facilitate high-accuracy positioning of a positional relationship between an image sensor and an imaging optical element and a positional relationship between an image sensor and a phase-type low-pass filter.

[0008]

According to a first aspect of the present invention, there is provided an imaging apparatus comprising:
The imaging optical element and the optical low-pass filter are held in a predetermined positional relationship by the holder, and the holder is arranged such that the positional relationship between the reference surface of the imaging optical element and the imaging surface of the imaging device is as specified. It is characterized by being fixed to a package.

Therefore, according to the imaging device of the first aspect, since the holder holds the imaging optical element and the optical low-pass filter in a predetermined positional relationship, only the holder is positioned in the package holding the imaging element. Thus, both the image sensor and the imaging optical device can be easily positioned with high accuracy in a predetermined positional relationship with respect to the image sensor.

According to a fourth aspect of the present invention, there is provided a method of manufacturing an image pickup device, wherein a distance from an image pickup surface of an image pickup device mounted on a package is measured by a length measuring device using an objective lens having a small depth of focus, and the measured value is a predetermined value. The position where the value is obtained is determined, and the holder holding the imaging optical element and the optical low-pass filter in a predetermined positional relationship is positioned so that the lens reference plane is located at the position where the predetermined value is obtained. It is characterized in that the positional relationship is fixed.

Therefore, according to the method of manufacturing an image pickup apparatus of the present invention, the distance between the image pickup surface of the image pickup device and the position where the reference surface of the imaging optical element should be located is measured using an objective lens having a small depth of focus. The position is fixed by adjusting the positional relationship of the holder with respect to the package so that the lens reference surface is located at that distance, so that the reference surface of the imaging optical element and the image sensor Can be controlled with high accuracy.

Since the holder also holds the optical low-pass filter in a predetermined positional relationship with respect to the imaging optical element held by the holder, the holder naturally moves the optical low-pass filter to the imaging device by being positioned with respect to the package. Can be accurately positioned with high accuracy. That is, both the imaging optical element and the optical low-pass filter can be simultaneously positioned with high accuracy with respect to the imaging element. Since the positioning between the imaging optical element, the optical low-pass filter, and the imaging element can be performed with high accuracy, the imaging apparatus can be configured without any problem even if the focal depth of the imaging optical element is reduced.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image pickup apparatus according to the present invention basically includes an image pickup element housed in a package, an image forming optical element for forming an image of a subject on an image pickup surface of the image pickup element, and the image pickup element. And an optical low-pass filter provided between the imaging optical element, and the imaging optical element and the optical low-pass filter are held by a holder in a predetermined positional relationship, and the holder is mounted on the package. On the other hand, the positional relationship is fixed so that the reference surface of the imaging optical element has a predetermined positional relationship with respect to the imaging surface of the imaging device. A solid-state imaging device, a MOS-type solid-state imaging device, or an amplification-type solid-state imaging device can be used. Further, the imaging element may be an area sensor type or a linear sensor type.

The optical low-pass filter is suitable for the image pickup apparatus of the present invention because the phase-type low-pass filter is low in manufacturing cost. However, the present invention is not limited to this. For example, a birefringent low-pass filter may be used. The imaging optical element may be formed of a plastic material or a glass material. Further, a spherical lens or an aspherical lens may be used, and any imaging optical element may be used as long as it can image a subject on an imaging surface of an imaging element. The holder for holding the imaging optical element may be formed of glass, but since a positioning portion for positioning the optical low-pass filter must be provided, workability is required. Is preferred.

The package holding the image sensor may be made of plastic or ceramic.

The positioning of the image forming optical element and the optical low-pass filter with respect to the image pickup element is performed, for example, by measuring the distance from the image pickup element to the position of the lens reference plane by a length measuring device, and measuring the distance. The positioning is performed by positioning the holder with respect to the package so that the lens reference surface is positioned at the same time, and then fixing the positional relationship. The length measuring device has a shallow depth of focus as an objective lens, for example, 0.1 μm to 0.1 mm, particularly 0.1 μm to
It is preferable to use one having a depth of focus of 10 μm. This is because the length measurement accuracy can be increased.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the illustrated embodiments. FIG. 1 is a longitudinal sectional view showing a first embodiment of the imaging apparatus of the present invention, and FIGS. 2A to 2C are cross-sectional views showing different components of the imaging apparatus of FIG. FIG. 2B shows an optical imaging device (lens) and a holder, FIG. 2B shows an optical low-pass filter (phase-type low-pass filter), and FIG. 1C shows an imaging device and a package containing the same. In the drawings, reference numeral 1 denotes a package made of, for example, ceramic or resin, 2 denotes a storage recess of the package, and a solid-state imaging device 3 is die-bonded on a bottom surface in the recess. A wire is bonded between the wiring and each wiring (not shown) of the package 1, but the bonding wire is not shown.

Reference numeral 4 denotes a transparent sealing plate for externally closing the storage recess 2 in which the solid-state imaging device 3 is stored, and is made of glass or transparent resin. Reference numeral 5 denotes a holder, which is made of, for example, a resin. At least substantially in the vicinity of a central portion thereof is made transparent, and a lens element 6 is adhered to the central portion. An imaging optical element (imaging lens) is formed.

Reference numerals 7 denote mounting steps formed on the holder 5 for mounting a low-pass filter. When an optical low-pass filter (10), which will be described later, is engaged with the mounting step, the optical low-pass filter 9 naturally The positional relationship is formed so as to be positioned in a predetermined positional relationship with high accuracy. Reference numerals 8 denote legs of the holder 5, and the holder 5 is fixed to the package 1 with adhesives 9 at the legs 8.

Reference numeral 10 denotes an optical low-pass filter, for example, a phase-type low-pass filter. A diffraction grating is provided on one side or both sides of the element.
As shown in (B), the light is separated into zero-order light beams and ± first-order light beams. However, strictly speaking, ± second-order light beams, ± third-order light beams, ...
Although there are ± multi-order light beams as described above, since these multi-order light beams are designed to be as small as possible in the diffraction grating, they are practically almost negligible. In this embodiment, the phase-type low-pass filter 10 has a function of absorbing or reflecting infrared light. That is, the low-pass filter not only functions to suppress the false signal but also performs the infrared cut function. By doing so, there is no need to provide an infrared cut filter separately in addition to the optical color filter 10, and it is possible to reduce the cost, size, and especially the thickness.

Incidentally, the phase type low-pass filter 10
Separates incident light at an arbitrary angle in accordance with the frequency of the diffraction grating. Therefore, if an error occurs in the position with respect to the solid-state imaging device 3, the separation width on the imaging surface will change.
Therefore, in order to obtain the low-pass effect, it is necessary to separate the light beam into an arbitrary width with respect to the pixel pitch of the image sensor, but if the separation width changes as described above, the desired low-pass effect can be obtained. I will not be able to. Therefore, the phase-type low-pass filter 10 must be positioned with extremely high accuracy with respect to the solid-state imaging device 3, which can be easily performed by accurately positioning the holder 5 with respect to the solid-state imaging device 3.

Next, the positioning of the holder 5 and the solid-state imaging device 3 will be described with reference to FIGS.

(A) The package 1 that houses the solid-state imaging device 3 is provided with a transparent sealing plate 4 for protecting the solid-state imaging device 3 from dust, moisture, and the like. Depth of focus (for example, 0.1 μm
A position corresponding to a predetermined distance set in advance from the imaging surface of the solid-state imaging device 3 is obtained by a length measuring device 11 using a lens (approximately 0.1 μm to 10 μm).
In the present specification, a length measuring device measures the position of an imaging surface by focusing an image from an objective lens and measuring a position when the image is focused. FIG.
4A shows a state in which the position of the solid-state imaging device 3 is measured by the length measuring device 11 and the position where the reference plane of the lens 6 should exist is obtained.

(B) On the other hand, the holder 5 for holding the lens element 6 has the mounting steps 7, 7 for positioning the phase-type low-pass filter 10 so as to have a predetermined positional relationship with the lens element 6 as described above. So that when the phase-type low-pass filter 10 is fitted and pressed against the mounting step portions 7, 7, the phase-type low-pass filter 10 is positioned with high precision in a predetermined positional relationship with the lens element 6. Has become
In this state, the phase-type low-pass filter 10 is fixed to the holder 5. FIG. 3B shows the holder 5 holding the lens element 6 and positioning the phase-type low-pass filter 10 with respect to the lens element 6 at the mounting steps 7, 7.

(C) Next, as shown in FIG. 3C, the holder 5 is held by a jig 12 so that the lens reference surface is
As shown in (A), the position of the holder 5 is moved so as to be located at a predetermined distance from the imaging surface of the solid-state imaging device 3 measured by the length measuring device 11. This is because the position data of the length measuring device 11 and the jig 12 are relatively managed.

Then, when the positional relationship of the lens reference surface with respect to the imaging surface of the solid-state image sensor 3 is as specified, the holder 5 is adhered to the solid-state image sensor 3 housing package 1 with its legs 8, 8 in that state. Fix with agents 9 and 9. Then, an imaging device as shown in FIG. 1 is completed.

According to such a method of manufacturing an imaging device,
A position where a preset lens reference plane should exist with respect to the imaging surface of the solid-state imaging device 3 housed in the package 1 is measured by the length measuring device 11, and an optical low-pass is performed so that the lens reference plane is located at that position. The holder (5) with the filter (phase type low-pass filter) (10) attached thereto is positioned by the jig (12), and the holder (5) is fixed to the package (1) with its legs (8) and (8) in that state. The reference surface of the lens element 6 can be positioned with extremely high accuracy.

The holder 5 holds the held lens element 6
The optical low-pass filter 4 is positioned and held in a predetermined positional relationship by the mounting steps 7 and 7 with respect to the position, so that the position is measured by the length measuring device 11 as described above, and the above-described repair is performed based on the measurement data. By controlling the position by the tool 12, the optical low-pass filter 4 is naturally positioned with high accuracy in a predetermined positional relationship with respect to the imaging surface of the solid-state imaging device 3. Accordingly, both the imaging optical element 6 and the optical low-pass filter 10 can be simultaneously positioned with high precision with respect to the solid-state imaging element 3.

The fact that the imaging optical element 6, the optical low-pass filter 10, and the imaging element 3 can be positioned with high accuracy means that imaging can be performed without any problem even if the focal depth of the imaging optical element 6 is reduced. This means that the device can be configured, and therefore it is nothing less than that a small-sized, particularly thin-type imaging device can be provided without any trouble.

In the drawings showing the embodiments, the cover and the aperture of the optical system are not described, but it goes without saying that any cover and aperture can be attached as long as they do not interfere with the holder 5 and the lens element 6. In the illustrated embodiment, the lens element 6 is inserted into at least the transparent part (substantially the center part) of the holder 5 and stretched. However, the present invention is not limited thereto.
A lens element pair 6 having a flat surface on one side and a convex spherical surface on the other side adhered to the front and back surfaces of the transparent portion is used as an imaging optical element (lens). Alternatively, one lens element 6 having a convex spherical surface on one surface may be attached to only one surface of the lens attachment portion of the holder 5. Further, an aspheric lens may be used instead of the spherical lens. In short, any object can be used as long as the object can be imaged on the imaging surface of the solid-state imaging device 3.

[0031]

According to the imaging apparatus of the present invention, since the holder holds the imaging optical element and the optical low-pass filter in a predetermined positional relationship, the holder can be simply positioned in the package holding the imaging element. Both the imaging element and the imaging optical element can be easily positioned with high accuracy in a predetermined positional relationship with respect to the imaging element.

According to the method of manufacturing an image pickup device of the present invention, the distance from the image pickup surface of the image pickup device to the position where the reference plane of the imaging optical element should be located is measured by a length measuring device using an objective lens having a small depth of focus. Then, since the positional relationship between the holder and the package is adjusted and the positional relationship is fixed so that the lens reference surface is located at that distance, the reference surface of the imaging optical element, and the imaging surface of the image sensor, Distance can be controlled with high accuracy.

Since the holder also holds the optical low-pass filter in a predetermined positional relationship with respect to the imaging optical element held by the holder, the holder naturally moves the optical low-pass filter to the imaging device by being positioned with respect to the package. Can be accurately positioned with high accuracy. That is, both the imaging optical element and the optical low-pass filter can be simultaneously positioned with high accuracy with respect to the imaging element. Since the positioning between the imaging optical element, the optical low-pass filter, and the imaging element can be performed with high accuracy, the imaging apparatus can be configured without any problem even if the focal depth of the imaging optical element is reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of an imaging device of the present invention.

2 (A) to 2 (C) are cross-sectional views showing different components of the imaging apparatus of FIG. 1, and FIG. 2 (A) is an imaging optical element (lens).
(B) shows an optical low-pass filter (phase-type low-pass filter), and (C) shows an image sensor and a package for housing the same.

FIGS. 3A to 3C show an example of a method of manufacturing the imaging device shown in FIG. 1 (one embodiment of a method of manufacturing the imaging device of the present invention);
FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Package, 3 ... Image sensor (solid-state image sensor), 5 ... Holder, 6 ... Imaging optical element (lens element), 7 ... Optical low-pass filter mounting step part, 1
0: Optical low-pass filter (phase-type low-pass filter).

Claims (5)

[Claims] 1. An imaging device housed in a package for converting an input light into an electric signal by photoelectric conversion, an imaging optical device for forming an image of a subject on an imaging surface of the imaging device, and an image formation with the imaging device. An optical low-pass filter provided between the optical element and the optical element, wherein the imaging optical element and the optical low-pass filter are held by a holder in a predetermined positional relationship. An imaging apparatus, wherein the positional relationship is fixed such that the reference surface of the imaging optical element has a predetermined positional relationship with respect to the imaging surface of the imaging device. 2. The imaging apparatus according to claim 1, wherein the optical low-pass filter is a phase-type low-pass filter. 3. An optical low-pass filter having a function of absorbing or reflecting infrared light.
Or the imaging device according to 2. 4. An imaging device housed in a package for converting input light into an electric signal by photoelectric conversion, an imaging optical device for imaging a subject on an imaging surface of the imaging device, and imaging with the imaging device An optical low-pass filter provided between the optical element and the optical element, the imaging optical element and the optical low-pass filter are held by a holder in a predetermined positional relationship, the holder with respect to the package, A method of manufacturing an imaging device, wherein a positional relationship is fixed such that a reference surface of the imaging optical element has a predetermined positional relationship with respect to an imaging surface of the imaging device, wherein the imaging device attached to the package A predetermined distance from the imaging surface of the element where the reference plane of the imaging optical element is to be located is measured by a length measuring device using an objective lens having a small depth of focus, and the holder is mounted on the lens. The imaging device manufacturing method reference plane, characterized in that the positioning to be present at the distance measured by the measuring device, to fix the positional relationship thereon. 5. The method according to claim 4, wherein the depth of focus of the objective lens used in the length measuring device is 0.1 μm to 1 mm.