JPH0216257Y2 - - Google Patents

Description

[Detailed Description of the Invention] (1) Technical Field of the Invention The present invention relates to a measuring device that optically measures distances of about 0 to 10 cm.

(2) Background of the technology Traditionally, when assembling printed wiring boards used in electronic equipment, for example, in order to check the correctness and history of the electronic components mounted on them, information has been written on the printed wiring boards and electronic components. part number,
It is necessary to check the lot number etc. Traditionally, this work was done visually, but there is a need for the development of automatic machines to streamline this process.

(3) Prior art and problems Figure 1 is a diagram for explaining a printed wiring board on which components are mounted. In the figure, 1 is the printed wiring board, 1a is its part number, lot number, 2,
3 is a part, and 2a and 3a are written on the parts to indicate the part number and lot number, respectively.

Such symbols can be read with conventional character reading devices, but as shown in FIG. Because of the difference, the distance between the character reader and the symbol must be measured and the position of the character reader must be adjusted accordingly.

To measure this distance, you can measure the angle of the object when looking at it from both ends of a baseline of a certain length, calculate the distance from this, or move the lens to focus on the object. There are methods of measuring distance from the amount of movement of the lens, but each method requires a mechanical mechanism and has the disadvantage that it takes a long time to measure.

(4) Purpose of the invention In view of the above-mentioned drawbacks of the conventional technology, the object of the invention is to provide a distance measuring device that does not require a mechanical mechanism.

(5) Structure of the invention According to the invention, a hologram lens is formed by overlapping a plurality of hologram lenses with different focal lengths on a hologram dry plate, and when parallel light is incident on the lens, an imaging lens for condensing the light that has passed through the hologram lens among the light that has passed through the hologram lens and reflected on the object; and a pinhole provided in the focal plane of the imaging lens at a position corresponding to each of the hologram lenses. and a photodetector provided after each pinhole of the pinhole array, and from the focal length of the hologram lens corresponding to the pinhole that transmits the largest amount of light when parallel light is incident on the hologram lens, This is achieved by providing a distance measuring device characterized by determining the distance between the lens and an object.

(6) Example of implementation of the idea Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a diagram showing a distance measuring device according to the present invention.

In the figure, 4 is a hologram lens formed by overlapping a plurality of hologram lenses l ₁ to _{l o} with different focal lengths on a hologram dry plate, 5 is a beam splitter, 6 is an imaging lens,
7 is a pinhole array provided on the focal plane of the imaging lens 6, and 8 is a photodetector provided behind each pinhole. When a parallel light beam is incident on the hologram lens 4, each hologram lens l ₁ ~
The light that passes through l _o and is reflected by the object 9 passes through each hologram lens l ₁ to _{l o} again, is reflected by the beam splitter 5, is guided to the imaging lens 6, and is directed to the pinhole array 7.
It is configured to form an image. Note that a plurality of pinholes 7a are bored in the pinhole array 7, and the positions of the pinholes 7a are determined from each hologram lens l ₁ to _{l o}
It is located at the imaging position. Further, the size of each pinhole is adjusted so that the same amount of light passes through each hologram lens l ₁ to lo because the focal length of each hologram lens l 1 to _lo is different and the size of the image formation is different. That is, as shown in Fig. 3, when the focal length of the condenser lens 6 is _f0 , the focal length of the hologram lens _l1 is
In the case of f ₁ , the diameter of the pinhole is d=f ₀ /f ₁ k, and when the focal length of the hologram lens l ₂ is f ₂ , d=f ₀ /f ₂ k. Therefore, if the focal length of the hologram lens is f _x , then d=f ₀ /f _x k. In other words, the longer f _x becomes, the smaller the pinhole diameter becomes.

The operation of this embodiment configured in this way will be described next. First, parallel light rays are incident on the hologram lens 4. When prompted, each hologram lens l ₁ ~
The light that has passed through l _o is reflected by the object 9, passes through each hologram lens l ₁ to _{l o} again, is reflected by the beam splitter 5, is focused on the pinhole array 7 by the imaging lens 6, and is further The light passes through the pinhole 7a and reaches the light receiving element 8.

Here, if the focal length of a certain hologram lens is not equal to the distance between the lens and the object 9, the light hitting the object will be scattered, and the amount of light reflected and reaching the pinhole 7a will be reduced. On the other hand, if the focal length of a certain hologram lens is equal to the distance between the lens and the object 9, the focus will be on the object plane, and the light will be reflected from the object 9 into the pinhole 7.
The amount of light reaching point a is the largest. Therefore, it is determined that the focal length of the hologram lens corresponding to the pinhole with the largest amount of transmitted light is the distance from the lens to the object 9.

FIG. 4 is a diagram showing an example of a distance measuring circuit. In the figure, 10 _-1 to 10 _-o are amplifiers connected to each photodetector, 11 is a multiplexer to which each amplifier is connected, and 12 is an analog digital converter,
13 is a controller. The operation of this circuit is such that the outputs from the amplifiers 10 _-1 to 10 _-o are selected by the multiplexer 11, processed by the analog-to-digital converter 12, and input to the controller 13.
The controller 13 selects the largest output and can determine the distance between the hologram lens and the object from the focal length of the hologram lens corresponding to the photodetector. Note that a CCD may be used as the photodetector.

(7) Effects of the invention As explained in detail above, the distance measuring device of the present invention can measure distance optically and make its determination using an electric circuit, so it does not require mechanical operation. The measurement time is shortened, and this is a great advantage in that it can be used to quickly measure short distances.

[Brief explanation of the drawing]

Fig. 1 is a diagram for explaining a printed wiring board on which components are mounted, Fig. 2 is a diagram showing a distance measuring device according to the present invention, Fig. 3 is a diagram for explaining the size of a pinhole, and Fig. 4 is a diagram for explaining the size of a pinhole. The figure is a diagram for explaining an electric circuit for determining distance based on the output of a photodetector. In the drawings, 4 is a hologram lens, 5 is a beam splitter, 6 is an imaging lens, 7 is a pinhole array, 7a is a pinhole, and 8 is a photodetector.

Claims (1)

[Scope of utility model registration request] A hologram lens is formed by overlapping a plurality of hologram lenses with different focal lengths on a hologram dry plate, and when parallel light is incident on the lens, the hologram lens accounts for the light that passes through the lens and is reflected on an object. an imaging lens for condensing the transmitted light; a pinhole array having pinholes provided in the focal plane of the imaging lens at positions corresponding to each of the hologram lenses; and a pinhole array provided after each pinhole of the pinhole array. and a photodetector, and the distance between the lens and the object is determined from the focal length of the hologram lens corresponding to the pinhole that transmits the largest amount of light when parallel light is incident on the hologram lens. Distance measuring device.