JPH07140324A - Light projecting and receiving device - Google Patents

Abstract

PURPOSE:To effectively detect the light of a specific wavelength region from a light projecting means with simple constitution. CONSTITUTION:Optical multilayered film interference filters 13 consisting of plural kinds of metal oxide thin-film layers which reflect light exclusive of the prescribed wavelength region are directly laminated on the light receiving surface of a light receiving semiconductor element 7 disposed in the light receiving part of this light projecting and receiving device. Dyes which absorb light of wavelengths exclusive of the desired wavelength are mixed in a resin molding package 14 for coating the semiconductor element 7, by which the matching of the band-pass characteristics and the light emitting wavelength of the light emitting element is optimized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting and receiving device for detecting an object by irradiating the object with light and receiving transmitted light or reflected light.

[0002]

2. Description of the Related Art Conventionally, various light emitting and receiving devices have been proposed which detect an object by irradiating the object with light and receiving transmitted light or reflected light. This type of light projecting / receiving device is provided with a bandpass filter for transmitting only light in a specific wavelength region emitted from the light projecting unit and preventing ambient light from entering the light receiving unit. As a conventional light receiving element with a bandpass filter, there is known one having a structure in which an interference filter in which a metal oxide is deposited on both surfaces of a glass substrate is installed in front of the light receiving element.

As another structure, as shown in FIG. 7, the transparent side in which a dye having a filter characteristic for cutting light of short wavelength is mixed on the light receiving surface side of the light receiving element 102 mounted on the substrate 101. There is a resin which is covered with a resin 103 and further covered with a transparent resin 104 in which a dye having a filter characteristic for cutting long-wavelength light is mixed on the surface of the resin 103 so that only light having a wavelength in a specific region is transmitted. . In addition,
The substrate 101 is housed in a case 105, and an opening 106 through which light enters the light receiving element 102 is formed on the upper surface of the case 105. The light receiving element 102 is the substrate 1
The wiring pattern on 01 is connected via a wire 107.

[0004]

However, in the case of a general interference filter in which a metal oxide is vapor-deposited on both surfaces of a glass substrate, its transmission characteristics change when the incident angle changes (the transmission region moves to the short wavelength side). However, there is a drawback that the amount of transmitted light in a desired specific wavelength region is reduced. Therefore, conventionally, it is necessary to arrange the optical filter in the parallel optical path where the incident angle is constant, and in the end, the optical filter is arranged in the preceding stage of the light receiving lens, and the shape of the light receiving section becomes large and the optical filter is arranged. It must be arranged so that the incident angle is constant with respect to the incident angle, which causes a problem of high manufacturing cost.

Further, in the case of the light receiving element shown in FIG. 7, since the transmittance attenuation characteristic on the long wavelength side is not sharp cut as shown in FIG. 8, it is matched with the wavelength distribution of the light emitting element. Was poor, and sufficient ambient light resistance was not obtained. In such a light receiving element, in order to obtain sharp cut characteristics, it is necessary to further coat an edge filter on the transparent resin 104. In this case, the technique of coating the transparent resin 104 with the multilayer film is difficult, and thus there is a problem in terms of reliability of transmission characteristics.

The present invention has been made in view of the above circumstances, and has light receiving means capable of obtaining a high disturbance light resistance with a simple structure, and efficiently emits light in a specific wavelength region from the light projecting means. It is an object of the present invention to provide a light emitting and receiving device capable of detecting light.

[0007]

In order to achieve the above object, the present invention according to claim 1 provides a light emitting means for emitting light in a specific wavelength region (for example, the light emitting element 5 in FIG. 2), and at least the above. An optical filter that transmits only light in a partial wavelength region of a specific wavelength is formed on the surface of the light receiving portion of the semiconductor element 7 having a spectral sensitivity in the light region from the visible light region to the infrared light region (for example, as shown in FIG. In the light projecting / receiving device 1 including the two light receiving parts 3), the optical filter is replaced by the semiconductor element 7
The optical multi-layer interference filter 13 is directly laminated on the surface of the light receiving part and is composed of a plurality of types of metal oxide thin film layers that reflect light other than a predetermined wavelength range.

According to a second aspect of the present invention, in the light emitting and receiving device, the optical multilayer interference filter 13 reflects the light of one of the long and short wavelengths outside the predetermined wavelength range and absorbs the light of the other wavelength. A transparent resin containing a dye (see, for example, FIG. 1).
At least the surface of the light receiving portion of the semiconductor element 7 is covered with the resin mold package 14).

According to a third aspect of the present invention, there is provided a light projecting / receiving device in which a condenser lens 6 for converging light passing through the optical filter is formed integrally with the resin mold package 14.

[0010]

In the light emitting and receiving device according to the first aspect of the present invention, there is provided an optical multi-layer having a sharp wavelength cut characteristic and a plurality of kinds of metal oxide thin film layers having a small shift amount of the cutoff wavelength due to a difference in incident angle. By depositing the film interference filter 13 on the surface of the light receiving portion of the semiconductor element 7, the interference filter 1
It is possible to optimize the matching between the band pass characteristic of No. 3 and the emission wavelength of the light emitting element 5.

According to another aspect of the present invention, there is provided a light projecting / receiving device.
In the resin mold package 14 that covers the semiconductor element 7 on the light receiving side by reflecting the light of one of the long and short wavelengths outside the predetermined wavelength range by the interference filter 13, for example, the long wavelength side,
For example, since a dye that absorbs light on the short wavelength side is mixed, the bandpass characteristic can be complemented by the filter effect of the dye. As a result, the manufacturing process of the metal oxide thin film layer constituting the interference filter 13 can be simplified, and the semiconductor light receiving element 7 with the bandpass function can be manufactured at a lower cost.
Can be supplied.

In the light projecting / receiving device according to the third aspect,
Since the condenser lens 6 is formed integrally with the resin mold package 14, the light passing through the optical filter can be converged on the semiconductor light receiving element 7 with a simple and small structure.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the light emitting and receiving device of the present invention will be described below with reference to the drawings.

1 and 2 show the structure of an embodiment of the present invention. As shown in FIG. 2, the light emitting and receiving device 1 of the present embodiment is
The light emitting unit 2 emits light in a specific wavelength range, and the light receiving unit 3 receives the light emitted from the light emitting unit 2. The light emitting unit 2 emits light and the light receiving unit 3 receives light. Are arranged so as to face each other, and the object 4 moves between the light projecting section 2 and the light receiving section 3 in a direction at a right angle to the paper surface.
The object 4 is detected by receiving the light that has transmitted the light from the light receiving unit 3.

The light projecting section 2 collimates the light from the light emitting element 5 which emits light of a specific wavelength and the light from the light emitting element 5 into the light projecting section 3.
The light emitted from the LED as the light emitting element 5 is, for example, as shown in FIG. 3, a symmetric wavelength region with a center wavelength of 940 nm. Is a light having.

Returning to FIG. 2, the light-receiving unit 3 causes the light from the light-projecting unit 2 which is transmitted directly or through the object 4 to be incident on the light-receiving surface of the light-receiving element 7 by the condenser lens 6. Has become. Then, in order to prevent ambient light from being collected on the light receiving surface of the light receiving element 7 via the condenser lens 6, the filter characteristics of the resin mold package of the light receiving element 7 which will be described later and the metal oxide thin film layer of the semiconductor light receiving surface. The interference filter is provided with an optical filter that transmits only light of a specific wavelength to the light receiving surface.

FIG. 1 shows a detailed structure of the light receiving section 3. A semiconductor element 7 which is a light receiving element is provided on the metal lead frame 11.
Are die-bonded, and the semiconductor element 7 is wire-bonded via the wire 12. On the surface of the light receiving portion of the semiconductor element 7, the interference filter 13 made of a metal oxide multilayer film is directly laminated. Further, the semiconductor element 7 is covered with a resin mold package 14 by transfer molding.

The resin used for molding the resin mold package 14 is transparent and contains a dye that determines the filter characteristics. For example, if the wavelength λ1 of the desired light is 940
The resin having filter characteristics for cutting light of short wavelength is, for example, OPT manufactured by Sumitomo Chemical Co., Ltd.
It can be obtained by mixing a dye such as -NIR-840S, which absorbs light having a wavelength of around 840 nm or shorter, into a transparent resin.

On the other hand, the desired wavelength of light (λ1 = 940n
m) Light having a longer wavelength is cut by the metal oxide multilayer film forming the interference filter 13, and desired filter characteristics are obtained. The light having the desired wavelength region in this manner is condensed on the light receiving surface of the semiconductor element 7 by the condenser lens 6 integrally formed on the light incident surface of the resin mold package 14.

The interference filter 13 is composed of a bandpass filter consisting of only an interference film. Therefore, the transmission characteristic of the interference filter 13 changes depending on the incident angle of the light condensed by the condenser lens 6, as shown in FIG. That is, the light transmitted through the center of the condenser lens 6 is incident on the interference filter 13 at an incident angle of 0 degree, but the light incident on the outermost diameter is incident on the interference filter 13 at an incident angle of 20 degrees. Therefore, the incident angle is 2 with respect to the wavelength characteristic λ0 with the incident angle of 0 degree.
The wavelength characteristic λ1 of 0 degree is parallel-shifted by Δλ (= λ1−λ0) to the short wavelength side.

This Δλ is calculated as follows from FIG. That is, as shown in FIG. 5A, the interference film 13 formed on the substrate 13 a forming the interference filter 13.
Assuming that the equivalent refractive index in the whole b is N and the equivalent film thickness of the interference film 13b is D, the equivalent optical film thickness D ′ is D ′ = N · D in the case of vertical incidence (incident angle of 0 degree). (1) Further, as shown in FIG. 5B, when the incident angle is θ, D ′ = N · D · cos θ ′ (2) However, θ '= arc sin {(1 / N) · sin θ}
Is.

As is clear from the equation (2), when the incident angle θ becomes large, the apparent optical thick film becomes thin, that is, the equivalent characteristic is obtained by shifting to the short wavelength side. Therefore,
Assuming that the wavelength having a certain characteristic at the time of vertical incidence is λ1, the wavelength λ0 having the same characteristic value as λ1 at the incident angle θ is λ0 = λ1 · cosθ ′ (3). Therefore, it is calculated as Δλ = λ1−λ0 = λ1 (1-cosθ ′) (4).

In the transmission characteristics of the interference filter 13 shown in FIG. 4, when the transmission band is widened, the amount of ambient light (white light) transmitted increases, so that the noise component increases. Conversely, if the transmission band is narrowed, the amount of light (signal light) emitted by the light emitting element 5 is reduced. As described above, the light emission characteristics of the light emitting element 5 have the peak wavelength λp = 940 (n
m), the transmission band of 90% or more of the interference filter 13 of the light receiving unit 3 shown in FIG. 1 is 940 ± C (nm) (C
Is a predetermined wavelength width), the light from the light emitting element 5 can be efficiently received with respect to the light having the incident angle of 0 degree, but the light of the light emitting element 5 can be received with respect to the light having the incident angle of 20 degrees. Since the transmittance of the long wave component of the emission spectrum decreases, the transmission characteristics of the interference filter 13 of this embodiment are as follows.

That is, 90% or more of the transmission band of the interference filter 13 is set to (940) with respect to the wavelength shift amount Δλ of the characteristics of the interference filter 13 of FIG.
+ Δλ / 2) ± C (nm). In other words,
For the peak wavelength λp of the light emitting element 5, the interference filter 1
The center wavelength of the transmission band of 3 is shifted by Δλ / 2 toward the long wavelength side.

As described above, according to the light emitting and receiving device 1 of this embodiment, the disturbance light is prevented from entering the light receiving portion 3 and the light emitting portion 2 is also provided.
It is possible to efficiently detect the light in the predetermined wavelength region from. Further, by integrally forming the semiconductor element 7 and the interference filter 13, the shift amount of the spectral characteristic due to the change of the incident angle can be minimized and the matching with the projected wavelength of the light emitting element 5 can be optimized. Further, by providing a bandpass function on the short wavelength side by the filter effect of the resin mold package 14, the device can be made extremely compact and the cost can be reduced as compared with the case where the optical filter is arranged on the conventional parallel optical path. be able to.

Although the light emission spectrum of the light emitted from the light emitting element 5 is symmetrical with respect to the peak wavelength, it is not limited to this and may be an asymmetric light emission spectrum.
In this case, the same effect can be obtained by substituting the peak wavelength λp of the light emitting element 5 in the above embodiment for the center-of-gravity wavelength λG set so that the emitted light amount on the short wavelength side and the emitted light amount on the long wavelength side are equal. Can be obtained.

Further, as an example of the structure of the interference filter 13, there is a structure in which two layers of metal oxide materials of SiO ₂ and TiO ₂ are alternately laminated in 20 layers directly on the light receiving portion of the semiconductor element 7.

Further, although the present embodiment has been described by using the example of the transmission type light emitting / receiving device as shown in FIG. 2, the present invention is not limited to this, and as shown in FIG. May be integrally formed. In this case, the light from the light emitting element 5 is irradiated onto the object 4 as parallel light by the light projecting lens 8, and the reflected light from the object 4 is condensed by the condensing lens 6. Then, it is detected by the semiconductor element 7 via the package 14 and the interference filter 13 which have the function of a color resin filter.

[0029]

As described above, according to the light emitting and receiving device of the first aspect, since the optical multilayer interference filter made of the metal oxide thin film layer is directly laminated on the surface of the light receiving portion of the semiconductor element 7, the interference occurs. The matching between the bandpass characteristic of the filter and the emission wavelength of the light emitting means can be optimized, and stable bandpass characteristic can be obtained.

According to the light emitting and receiving device of the second aspect, since the dye that absorbs light having a wavelength other than the desired wavelength is mixed in the transparent resin that covers the semiconductor element of the light receiving portion, It is possible to supplement the bandpass characteristic and obtain a high resistance to ambient light with an inexpensive light receiving section.

According to the light emitting and receiving device of the third aspect, since the condenser lens is integrally formed with the transparent resin which covers the semiconductor element of the light receiving portion, the light transmitted through the optical filter is simple and small in size. It can be focused on a semiconductor device.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a configuration of a light receiving portion of an embodiment of a light emitting and receiving device of the present invention.

FIG. 2 is a vertical cross-sectional view showing the configuration of an embodiment of a light projecting / receiving device having the light receiving section of FIG.

FIG. 3 is a diagram showing a light emission intensity characteristic of light emitted by the light emitting element of FIG.

FIG. 4 is a diagram showing the relationship between the transmittance and the incident angle of the optical filter of the light receiving section of FIG.

5 is an explanatory diagram showing an incident angle of light on a semiconductor element of the light receiving section of FIG. 1. FIG.

FIG. 6 is a vertical cross-sectional view showing the configuration of another embodiment of the light emitting and receiving device of the present invention.

FIG. 7 is a configuration diagram showing a configuration of an example of a light receiving section of a conventional light projecting and receiving device.

8 is a diagram showing a transmission characteristic of a filter of the light receiving section of FIG. 7. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light emitting / receiving device 2 Light emitting section 3 Light receiving section 5 Light emitting element (light emitting means) 6 Condensing lens 7 Semiconductor element (light receiving element) 13 Interference filter 14 Resin mold package (transparent resin)

Claims (3)

[Claims] 1. A light emitting means for emitting light in a specific wavelength range, and an optical filter for transmitting only light in at least a part of the specific wavelength range in a light range from a visible light range to an infrared light range. A light projecting / receiving device comprising a light receiving means formed on a light receiving portion surface of a semiconductor element having a spectral sensitivity, wherein the optical filter is directly laminated on the light receiving portion surface of the semiconductor element and reflects light other than a predetermined wavelength region. An optical multi-layer interference filter composed of a plurality of types of metal oxide thin film layers. 2. The optical multilayer interference filter is a transparent resin containing a dye that reflects light of one of the long and short wavelengths outside the predetermined wavelength range and absorbs light of the other wavelength, The light emitting and receiving device according to claim 1, wherein at least the light receiving surface of the semiconductor element is covered. 3. The light projecting / receiving device according to claim 2, wherein a condensing lens for converging light passing through the optical filter is integrally formed with the transparent resin.