US-12627878-B2 - Image acquisition system and image acquisition method

Abstract

An image acquisition system configured to acquire an image of an object to be conveyed. The system includes a plurality of light sources configured to emit light rays with which the object is irradiated, a light source control unit configured to switch a light source that irradiates the object with the light among the plurality of light sources, and a line scan sensor configured to detect light from the object irradiated with the light. The line scan sensor has a pixel section in which a plurality of pixels are at least one-dimensionally arrayed and is configured to switch a gain value for amplifying a signal from each pixel. The line scan sensor switches the gain value in synchronization with the switching of the light source.

Inventors

• Tetsuya Taka

Assignees

• HAMAMATSU PHOTONICS K.K.

Dates

Publication Date

20260512

Application Date

20220325

Priority Date

20210730

Claims (5)

1. 1 . An image acquisition system configured to acquire an image of an object to be conveyed, comprising: a plurality of light sources configured to emit light rays with which the object is irradiated; a light source controller configured to switch a light source that irradiates the object with the light among the plurality of light sources; and a line scan sensor configured to detect light from the object irradiated with the light, the line scan sensor having a pixel section in which a plurality of pixels are at least one-dimensionally arrayed and being configured to switch a gain value for amplifying a signal from each pixel, wherein the line scan sensor switches the gain value in synchronization with the switching of the light source.
2. 2 . The image acquisition system according to claim 1 , wherein the light source controller is configured to switch between the plurality of light sources in a predetermined pixel period based on a width of each pixel and a conveyance speed of the object.
3. 3 . The image acquisition system according to claim 1 , wherein the plurality of light sources include at least one reflective light source and at least one transmissive light source.
4. 4 . The image acquisition system according to claim 1 , wherein the plurality of light sources emit light rays of different wavelengths.
5. 5 . An image acquisition method for acquiring an image of an object to be conveyed, comprising: an irradiation step of irradiating the object with light rays by using a plurality of light sources; and a detection step of detecting light from the object irradiated with the light by a line scan sensor, wherein the line scan sensor has a pixel section in which a plurality of pixels are at least one-dimensionally arrayed, and is configured to switch a gain value for amplifying a signal from each pixel, in the irradiation step, a light source that irradiates the object with the light among the plurality of light sources is switched, and in the detection step, the gain value is switched in synchronization with the switching of the light source.

Description

TECHNICAL FIELD The present disclosure relates to an image acquisition system and an image acquisition method. BACKGROUND ART A device that obtains image information (image signal) by using a line sensor and acquires an image of an object has been known (see, for example, Patent Literatures 1 and 2). In the device described in Patent Literature 1, a one-dimensional line sensor in which CCDs are disposed in one column is used. A color negative film is irradiated with white light from a halogen lamp light source, and transmitted light is projected onto a CCD surface. A signal information of each of R, G, and B projected on the CCD surface is amplified by an amplifier and is converted into digital image data by an A/D conversion circuit. In the device described in Patent Literature 2, data sampling, offset adjustment, and gain adjustment are performed in an analog processing unit. Thereafter, an analog signal is converted into a digital signal in an A/D converter. CITATION LIST Patent Literature Patent Literature 1: Japanese Unexamined Patent Publication No. 2002-229136Patent Literature 2: Japanese Unexamined Patent Publication No. 2007-82013 SUMMARY OF INVENTION Technical Problem Meanwhile, there is a demand for a technique for efficiently acquiring an image in a system that acquires an image of an object to be conveyed. Therefore, a method for alternately turning on a reflective illumination and a transmissive illumination and synchronizing a scan timing of a line sensor is considered. However, in this case, two kinds of imaging are needed to acquire an image. The present disclosure describes an image acquisition system and an image acquisition method capable of efficiently acquiring an image in a case where a plurality of light sources are used. Solution to Problem One aspect of the present disclosure is an image acquisition system configured to acquire an image of an object to be conveyed. The system includes a plurality of light sources configured to emit light rays with which the object is irradiated, a light source control unit configured to switch a light source that irradiates the object with the light among the plurality of light sources, and a line scan sensor configured to detect light from the object irradiated with the light. The line scan sensor has a pixel section in which a plurality of pixels are at least one-dimensionally arrayed and is configured to switch a gain value for amplifying a signal from each pixel. The line scan sensor switches the gain value in synchronization with the switching of the light source. According to this image acquisition system, the light source is switched by the light source control unit, and the line scan sensor switches the gain value for amplifying the signal from each pixel in synchronization with the switching of the light source. With this configuration, the gain value of the signal from each pixel output in accordance with different light sources is adjusted. For example, brightness levels of two types of images can be adjusted. Thus, the image can be efficiently acquired in a case where the plurality of light sources are used. The light source control unit may be configured to switch between the plurality of light sources in a predetermined pixel period based on a width of each pixel and a conveyance speed of the object. In this case, since the light source is switched and the gain value is also switched in the predetermined pixel period, an S/N ratio is suitably maintained. The plurality of light sources may include at least one reflective light source and at least one transmissive light source. In this case, a more accurate image can be acquired by a combination of the reflected light and the transmitted light. In particular, since the plurality of light sources include the transmissive light source, it is advantageous for imaging a cloth-like object such as fabric or a thin object such as paper, a substrate, or a form. The plurality of light sources may emit light rays of different wavelengths. In this case, an image corresponding to a spectral reflection characteristic of the object to be conveyed can be efficiently acquired. For example, it is advantageous for imaging freshness and moisture content of a medicine, a food, a vegetable, a fruit, or the like, components constituting an object, or a foreign substance. Another aspect of the present disclosure is an image acquisition method for acquiring an image of an object to be conveyed. The method includes an irradiation step of irradiating the object with light rays by using a plurality of light sources, and a detection step of detecting light from the object irradiated with the light by a line scan sensor. The line scan sensor has a pixel section in which a plurality of pixels are at least one-dimensionally arrayed, and is configured to switch a gain value for amplifying a signal from each pixel, in the irradiation step, a light source that irradiates the object with the light among the plurality of