JPS6025183Y2 - Optical system of slide scanning device - Google Patents

Description

[Detailed description of the invention] This invention focuses the light emitted from a light source into a narrow spot light, scans the slide film, and transmits the transmitted light modulated by the image information on the slide film through a condensing lens. The present invention relates to an optical system of a slide scanning device that enters a light receiving surface of a photoelectric conversion element, converts the signal into an electrical signal carrying image information, and outputs the electrical signal to the outside.

This type of device has been conventionally known as a slide scanning device, and for example, the electric signal taken out to the outside as described above is input into a home television imager as a television signal, and is scanned onto a slide film. The recorded screen is displayed on the television screen.

In the optical system of the known slide scanning device, the slide film is scanned with a narrowly focused spot light, and the light modulated by the image information on the slide film is sequentially passed through a condenser lens and a gicroic mirror. Then, the light passes through an optical system consisting of a mixing lens, a color correction filter, and a cylindrical lens, and then enters a photomultiplier tube.
) is converted into an electrical image information signal.

However, since the optical system of this known slide scanning device uses a photomultiplier tube, it has many drawbacks as follows.

First of all, the photomultiplier tube itself, commonly called a photomultiplier tube, is expensive, and three of them are required.

Second, when a photomultiplier tube is used, a high-voltage power source is required.

Thirdly, in order to effectively use the light-receiving surface of the photomultiplier tube, a special optical component such as a cylindrical lens is required to match the beam shape of the incident light beam to the shape of the light-receiving surface.

Fourth, since the light-receiving area of the photomultiplier tube is relatively large (for example, 24 x 8 mm), the optical system becomes large and expensive.

For this reason, the known slide devices end up being large and expensive, and their users are limited to business users or some enthusiasts.

The object of the present invention is to provide a compact and inexpensive slide scanning device that does not have these various drawbacks, and an optical system that is suitable for a revolutionary and inexpensive slide scanning device for general household use.

To achieve this objective, the present invention focuses the light emitted from a light source into a narrow spot light, scans the slide film, and converts the transmitted light modulated by the image information on the slide film into a photoelectric converter through a condensing lens. In the optical system of the slide scanning device, the light is incident on the light-receiving surface of the conversion element, converted into an electrical signal carrying image information, and taken out to the outside. 1
a condensing lens, and a second condensing lens arranged apart from the first condensing lens so as to further condense the light that has passed through the condensing lens, and the second condensing lens The light emitted from the is made to enter a large diameter part of the reflector, which has a hollow truncated cone shape and a mirrored inner surface, and is made to enter a semiconductor photoelectric conversion element placed in the small diameter part, and this reflection The total length of the body is L1, the number of reflections inside L1 is m1, the spread width of human radiation is ao, and the diameter of the light receiving surface of the photoelectric conversion element is a.

, the hollow reflector is configured to satisfy the following relationship, where φ1 is the maximum incident angle that the incident light makes with the center axis of the reflector, and φL is the incident angle defined by the directional characteristics of the photoelectric conversion element. That is.

Furthermore, in one embodiment of the present invention in which three color electric signals are obtained by scanning a color slide film, the first,
A second and third reflector and a first, second and third semiconductor photoelectric conversion element provided at the small diameter end of each reflector are provided, and the first reflector and the second condensing lens are connected to each other. A first and a second guichroic mirror are arranged between them, and the light reflected by the first guichroic mirror is made to enter the second reflector,
The light reflected by the second gicroic mirror is made incident on a third reflector, and respective color filters are provided in front of the semiconductor photoelectric conversion elements provided in the small diameter portion of each reflector.

It is preferable to provide a mixing lens in front of the large diameter portion of the reflector.

It is preferable that the circuit for processing the electric signal generated by the semiconductor photoelectric conversion element is directly attached to a printed circuit board, and the printed circuit board is fixed to the small diameter portion of the reflector.

This invention simply requires a photomultiplier tube whose price is 5.
This was done based on the recognition that it is not enough to simply replace it with a semiconductor photoelectric conversion element that is only 3/100 to 3/100.

That is, simply replacing the photomultiplier tube in the conventional device with a semiconductor photoelectric conversion element would require a mixing lens with an extremely short focal length, which may cause strong shading.

It is also possible to use two mixing lenses instead of a mixing lens with such a large power, but another drawback is that it becomes extremely difficult to align the optical axis of these mixing lenses with the center of the light-receiving surface. arise.

The invention will be explained with reference to the drawings.

FIG. 1 shows the optical system of a conventional slide scanning device, and FIG. 2 shows the optical system of the slide scanning device of the present invention.

In both the optical system of a conventional slide scanning device shown in FIG. 1 and the optical system of a slide scanning device according to the present invention shown in FIG. The light is made incident on the slide film 3, and the slide film 3 is sequentially scanned.

In the optical system of the conventional slide scanning device shown in FIG. A rear dichroic mirror group 5 separates the colors into red, green, and blue channels.

The light of each color-separated channel, for example, the light of the green channel, is passed through the mixing lens 6, emitted from different positions of the flying spot tube 1, and transmitted through different places of the slide film 3, so that the light always covers the entire light-receiving surface. Make it incident.

The light that has passed through the mixing lens 6 is passed through a color filter 7.
After removing other color components that still remain even after color separation using the Guicroic Mira group 5, and further matching the shape of the light flux with the shape of the light receiving surface 10 of the photomultiplier tube 9 using the cylindrical lens 8, The image information carried by the modulated light is made incident on substantially the entire surface of the light-receiving surface 10, and is converted into an electrical signal and taken out to the outside.

On the other hand, in the optical system of the slide scanning device according to the present invention, the light passing through the slide film 3 is focused by the first condensing lens 11 and then condensed again by the second condensing lens 12. , the diameter of the luminous flux is further made narrower, and the colors are separated by a group of guichroic mirrors 13.

In this way, the group of guichroic mirrors 13 can be made much smaller than conventional ones.

One color created by color separation with 13 groups of Guicroic Mira.
For example, after passing the green channel light through the mixing lens 14 as desired, the interior is hollow and has a truncated conical shape;
The light is made incident on the large-diameter portion of the reflector 15 whose inner surface is made mirror-finished by, for example, aluminum plating by vacuum evaporation.

After the incident light is reflected several times on a mirror surface, the luminous flux becomes sufficiently thin and passes through a color filter 16 to a semiconductor photoelectric conversion element 1 with a small light receiving area, such as a PIN photodiode.
7, the light is received and converted into an electrical signal.

This color filter 16 can be directly deposited on the semiconductor photoelectric conversion element 17.

According to the present invention, since the condenser lens is divided into the first and second condenser lenses 11 and 12, the power of each condenser lens can be reduced, and therefore, it can be made thin. , for example, by molding plastic and can therefore be very inexpensive.

Furthermore, since the first and second condensing lenses can further narrow the luminous flux, the dimensions of the guichroic mirror can be reduced.

Furthermore, since the above-mentioned reflector 15 originally has a mixing function, it is advantageous to omit the mixing lens 14, and even if a mixing lens is provided, its power only needs to be small, so it can be made thin, and the condenser lens Similarly, it can be made inexpensively from plastic moldings.

Furthermore, the occurrence of shading due to the mixing lens can be suppressed.

Furthermore, since the present invention uses a semiconductor photoelectric conversion element 17 such as a PIN photodiode, the conventional cylindrical lens 8 can be omitted.

Next, a method of designing the reflector 15 will be explained with reference to FIG.

In the truncated conical hollow reflector shown in FIG. 3, the maximum incident angle φ□ that the incident light makes with the center axis of the reflector, and the output angle φ that the outgoing light makes with the center axis of the reflector.

The following relational expression holds true between . φ.

Engineering φ1+2rr1゜・・・・・・(
1) However, m is the number of reflections inside the reflector, and α is the taper angle of the reflector.

In equation (1), the maximum incident angle φ□ is determined by the optical system up to the reflector, and the output angle φ.

is limited by the directional characteristics of the light-receiving element as shown in FIG. 4, and when the angle of incidence on the light-receiving element selected from the directional characteristics of FIG. 4 is φL, it is necessary to satisfy the following relationship.

φ, ≧φ0 ・・・・・・
(2) The following equation (3) is derived from equations (1) and (2>).

mα≦kkomo (3) In this), the taper angle α of the reflector 15 is the maximum width a of the spread of the incident light.
, the diameter (or length of one side) ao of the light-receiving surface, and the total length of the reflector, it can be expressed as follows.

. =Ne “1 busy show ・Song・(4) Scream The following five equations are derived from equations (3) and (4).

mtan-1aL″< φL-φ+ 2
(5) When designing the hollow reflector 15, m and L are selected to appropriate values so as to satisfy equation (5).

FIG. 5 is a detailed view of the light receiving section of the optical system of the slide scanning device according to the present invention shown in FIG.

The hollow truncated conical reflector 15 has a main body 15A made of synthetic resin such as acrylic resin, a truncated conical hollow inside, and a mirror surface 15B formed by vacuum-depositing aluminum, for example, on its surface.

Further, the outer periphery of the main body 15A is surrounded by a copper plate ring 18, which is connected to ground.

It has been confirmed through experiments that by providing the ring 18 in this manner, the noise in the output signal of the PIN photodiode can be reduced.

Although this mechanism is not clear, it is presumed to be as follows.

That is, it seems that the metal surface 15B, such as aluminum, which constitutes the internal mirror surface of the hollow reflector 15 immediately in front of the semiconductor photoelectric conversion element 17 acts as an antenna that picks up noise.

Therefore, by providing the grounded copper plate ring 18 around the entire circumference, this copper plate ring 18 functions as a seal plate, and it is believed that noise is reduced.

Although the metal reflective surface 15B may be connected to ground, there is a risk that the optical characteristics of the reflective surface may deteriorate, so it is preferable to provide a copper plate ring 18 around the outer periphery.

As shown in FIG. 5, at the small diameter end of the reflector 15, for example,
A semiconductor photoelectric conversion element 17 such as an N photodiode is provided.

As mentioned above, the color filter 16 is provided in front of this element 17.
will be established.

For applications where image quality is not a big problem, a semiconductor photoelectric conversion element, which is cheaper than a PIN photodiode such as a photocell, can be used.

The semiconductor optoelectronic conversion element 17 has an electrical signal processing circuit 19 mounted directly on a printed circuit board 20, and this printed circuit board 20 is mounted directly on the reflector 15.

The present invention is not limited to the above-mentioned example, but can be modified in many ways.

For example, in the above-mentioned example, the slide film 3 is a color slide, and three channels are provided to generate three-color electric signals, but it can also be configured to generate black-and-white electric signals.

Of course, in this case, it is sufficient to provide one channel, and the color filter 16 is also unnecessary.

Further, the slide film 3 can be a positive or negative film, and when using a negative film, an image reversal circuit may be provided.

The effects of the optical system of the slide scanning device of the present invention described above are summarized as follows.

That is, by providing the second condensing lens, the guichroic mirror can be made smaller and can be housed in a small plastic box.

A semiconductor photoelectric conversion element with a relatively small light-receiving area, e.g. PIN
By attaching the diode (2.75 x 2.75 mm) directly to the printed circuit board and attaching the entire printed circuit board directly to the light receiving part of the reflector, stray capacitance associated with wiring is reduced, improving the S/N ratio. Contribute.

Semiconductor photoelectric conversion elements are extremely inexpensive, and unlike photomultiplier tubes, they do not require a special high-voltage power supply.

Furthermore, since the light-receiving surface is small, the area of the color correction filter can be extremely reduced.

There is no need for an optical component such as a cylindrical lens for matching the shape of the incident light beam to the shape of the light receiving surface.

Furthermore, as described above, since the interior is provided with a hollow conical reflector, an ordinary mixing lens with a relatively long focal length (for example, 30 mm) can be used, and the position adjustment is extremely easy.

In addition, by designing the hollow reflector to satisfy the above-mentioned equation (5), the incident light can be focused in accordance with the directional characteristics of the photoelectric conversion element, reducing light loss and S/ This has the effect of obtaining an image signal with a high N.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of an example of the optical system of a known slide scanning device, FIG. 2 is a diagram showing the configuration of an example of the optical system of the slide scanning device according to the present invention, and FIG. 3 is a diagram showing the configuration of an example of the optical system of the slide scanning device according to the present invention. FIG. 4 is a diagram showing the directional characteristics of the light receiving element, and FIG. 5 is an example of the light receiving section of the optical system of the slide scanning device according to the present invention. FIG. 1...Flying spot tube, 2...
Objective lens, 3...Slide film, 11
...First condensing lens, 12...Second
Condensing lens, 13... Gicroic mirror group, 14... Mixing lens, 15...
... Reflector, 16... Color filter, 17...
... Semiconductor photoelectric conversion element, 18 ... Copper plate ring, 19 ... Electric signal processing circuit, 20 ...
...Printed circuit board.

Claims (1)

[Claims for Utility Model Registration] Light emitted from a light source is narrowed down to a narrow spot light to scan a slide film, and the transmitted light modulated by image information on the slide film is photoelectrically converted through a condensing lens. In the optical system of a slide scanning device, which enters the light-receiving surface of the element, converts it into an electrical signal carrying image information, and takes this out to the outside, there is an optical system that collects the light modulated by the image information on the slide film. A first condensing lens and a second condensing lens arranged apart from the first condensing lens so as to further condense the light passing through the condensing lens, the second condensing lens is provided. The light emitted from the lens is incident on the large diameter part of the reflector, which has a hollow truncated cone shape and a mirrored inner surface.
The total length of this reflector is defined as the number of reflections inside L1, m is the spread width of the human incident light, and the diameter of the light-receiving surface of the photoelectric conversion element is a. , when the maximum incident angle that the incident light makes with the center axis of the reflector is φ8, and the angle of incidence defined by the directional characteristics of the photoelectric conversion element is φ, it is understood that the hollow reflector is constructed so as to satisfy the following relationship. Features of the optical system of the slide scanning device.